Publications by authors named "Leena Hupa"

35 Publications

Effect of bioactive glass air-abrasion on Fusobacterium nucleatum and Porphyromonas gingivalis biofilm formed on moderately rough titanium surface.

Eur J Oral Sci 2021 Mar 16:e12783. Epub 2021 Mar 16.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.

This aim of this study was to investigate the effects of three types of air-abrasion particles on dual-species biofilms of Fusobacterium nucleatum and Porphyromonas gingivalis, both of which were cultured on sandblasted and acid-etched (SA) titanium discs. Out of 24 SA discs with biofilm, 18 were exposed to either air-abrasion using Bioglass 45S5 (45S5 BG; n = 6), novel zinc (Zn)-containing bioactive glass (Zn4 BG; n = 6), or inert glass (n = 6). The efficiency of biofilm removal was evaluated using scanning electron microscopy (SEM) imaging and culturing techniques. Air-abrasion using 45S5 BG or Zn4 BG demonstrated a significant decrease in the total number of viable bacteria compared to discs air-abraded with inert glass or intact biofilm without abrasion. Moreover, P. gingivalis could not be detected from SEM images nor culture plates after air-abrasion with 45S5 BG or Zn4 BG. The present study showed that air-abrasion with 45S5 or Zn4 bioactive glasses can successfully eradicate dual-biofilm of F. nucleatum and P. gingivalis from sandblasted and acid-etched titanium discs.
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http://dx.doi.org/10.1111/eos.12783DOI Listing
March 2021

Behaviour of different bioactive glasses incorporated in polydimethylsiloxane endodontic sealer.

Dent Mater 2021 02 10;37(2):321-327. Epub 2021 Jan 10.

Department of Biomaterials Science and Turku Clinical Biomaterials Centre - TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, FI-20520 Turku, Finland; City of Turku Welfare Division, Oral Health Care, Turku, Finland.

Objectives: The aim of this study was to analyze the behavior of different bioactive glass fillers (BAGs) embedded in a polydimethylsiloxane matrix of an endodontic sealer.

Methods: Three different endodontic sealers were fabricated using S53P4, 45S5 and 18-06 glass fillers. Endodontic sealer Guttaflow Bioseal consisting of polydimethylsiloxane (PDMS) matrix was used as base of the experimental sealers. Behaviors of different glass fillers leaching from polymer matrix was studied in vitro for 14 days by measuring static ion dissolution profiles of Si, Na, Ca and P -ions. In addition, pH of the simulated bodyfluid (SBF) was monitored during the 14 days and all the sealer samples was examined with SEM/EDX analysis on the surface. Identical but non-glass filler containing polydimethylsiloxane-based sealer was used as a control material.

Results: By the time point of 24 h sealer with 45S5 had released twice as much of Si-ions compared to sealer with S53P4. No statistical differences of Na, Ca and P -ions dissolution were observed in the first 168 h for any groups whereas concentrations of Ca and P -ions decreased with 45S5 significantly after 336 h. Highest pH was measured for sealers with glass filler 45S5 and S53P4 (7.64-7.65). Visible mineral precipitation was observed only on sealer surfaces after 336 h' time period with groups of 45S5 and S53P4. However, presence of calcium and phosphorus oxides was confirmed only with 45S5.

Significance: Bioactive glass type 45S5 outperforms S53P4 and 18-06 by acting more dynamically in vitro set-up.
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http://dx.doi.org/10.1016/j.dental.2020.11.013DOI Listing
February 2021

Understanding the Interaction of Potassium Salts with an Ilmenite Oxygen Carrier Under Dry and Wet Conditions.

ACS Omega 2020 Sep 2;5(36):22966-22977. Epub 2020 Sep 2.

Chemistry and Chemical Engineering, Chalmers University of Technology, 412 93 Göteborg, Sweden.

This study describes how potassium salts representative of those in bio ash affect the reactivity of the oxygen carrier ilmenite under moist and dry conditions. Ilmenite is a bench-mark oxygen carrier for chemical-looping combustion, a technique that can separate CO from flue gases with minimal energy penalty. Different potassium salts were mixed with ilmenite to a concentration of 4 wt % potassium. The salts used were KCO, KSO, KCl, and KHPO. Experiments were performed at 850 °C under alternately oxidizing and reducing conditions in a dry atmosphere or in the presence of steam. Analyses of the oxygen carrier regarding changes in reactivity, structure, and composition followed the exposures. This study showed that salts such as KCO, KSO, and KCl increase the reactivity of the ilmenite. For the samples mixed with KCl, most of the salt was evaporated. KHPO decomposed into KPO, forming layers around the ilmenite particles that lead to agglomeration. Additionally, the KPO layer was more or less nonpermeable for CO and decreased the reactivity toward H significantly in both dry and wet conditions. This decreased reactivity indicates that the concentration of phosphorus in biofuel may have a significant effect on oxygen carrier degradation. It was also observed that the presence of steam changed the chemistry drastically for the nonphosphorus-containing salts. Alkali salts may react with steam, forming volatile KOH that evaporates partly. KOH may also form K-titanates by reaction with the oxygen carrier, leading to segregation of iron and titanium phases in the ilmenite.
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http://dx.doi.org/10.1021/acsomega.0c02538DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7495758PMC
September 2020

On-line microcolumn-based dynamic leaching method for investigation of lead bioaccessibility in shooting range soils.

Chemosphere 2020 Oct 10;256:127022. Epub 2020 May 10.

School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore; Nanyang Environment and Water Research Institute, Residues and Resources Reclamation Center, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore. Electronic address:

In this work, a miniaturized flow-through leaching test is presented for rapid screening of potential chemical extractants to explore the bioaccessibility of lead (Pb) in contaminated shooting range soils in Valkeala, Finland. The method combines the versatility of microcolumn-based extraction methods with on-line inductively coupled plasma optical emission spectrometry (ICP OES) analysis for expedient assessment of the magnitude of the bioaccessible pools and the leaching kinetics of lead from polluted soils under variable physicochemical scenarios. Acids and salt solutions were studied as potential extractants. The efficiency of the extractants relative to the initial total amount of lead in the soil sample (509 ± 21 mg/kg) were found to increase in the following order: 0.11 M acetic acid (55%) < 1 M MgCl (58%) < 0.1 M NHOH·HCl (61%) < 0.1 M citric acid (93%) < 0.1 M HCl (96%). The proposed on-line microcolumn-based method was further explored for implementation of the modified BCR (now termed Standards, Measurements and Testing Programme, SM&T) sequential extraction procedure to avail the information about different fractions available in the solid sample, and validated by mass balance calculations. The equivalent sequential procedure in a batch format was then studied and compared against the on-line microcolumn extraction method. The on-line dynamic extraction system presented in this work accepts a substantial amount of sample (2.5 g) as compared to previous flow-through mini-column setups (generally accommodating < 0.25 g of sample), thus maintaining sample representativeness and fostering comprehension of the extraction patterns for non-homogenous soil materials. The use of cotton buds and Teflon membranes and holders in the microcolumn setup facilitates the repeatable flow-through leaching of trace elements and restrict formation of preferential channels. Monitoring of the leachable trace elements in real time delivers detailed insight into the ongoing extraction process and provides a time-saving assessment of potential chemical extractants.
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http://dx.doi.org/10.1016/j.chemosphere.2020.127022DOI Listing
October 2020

Development of nano-porous hydroxyapatite coated e-glass for potential bone-tissue engineering application: An in vitro approach.

Mater Sci Eng C Mater Biol Appl 2020 Jun 19;111:110764. Epub 2020 Feb 19.

CSIR-Central Glass and Ceramic Research Institute (CSIR-CGCRI), Kolkata, India.

To reconstruct the defects caused by craniectomies autologous, bone grafting was usually used, but they failed most commonly due to bone resorption, infections and donor-site morbidity. In the present investigation, an effort has been made for the first time to check the feasibility and advantage of using hydroxyapatite (HAp) coated e-glass as component of bone implants. Sol-gel synthesized coatings were found to be purely hydroxyapatite from XRD with graded and interconnected pores all over the surface observable in TEM. The interconnected porous nature of ceramics are found to increase bioactivity by acting to up-regulate the process of osseointegration through enhanced nutrient transfer and induction of angiogenesis. From TEM studies and nano indentation studies, we have shown that pores were considered to be appropriate for nutrient supply without compromising the strength of sample while in contact with physiological fluid. After SBF immersion test, porous surface was found to be useful for nucleation of apatite crystals, hence increasing the feasibility and bioactivity of sample. However, our quasi-dynamic study showed less crystallization but had significant formation of apatite layer. Overall, the in vitro analyses show that HAp coated e-glass leads to significant improvement of implant properties in terms of biocompatibility, cell viability and proliferation, osteoinductivity and osteoconductivity. HAp coating of e-glass can potentially be utilized in fabricating durable and strong bioactive non-metallic implants and tissue engineering scaffolds.
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http://dx.doi.org/10.1016/j.msec.2020.110764DOI Listing
June 2020

Effect of bioactive glass air-abrasion on the wettability and osteoblast proliferation on sandblasted and acid-etched titanium surfaces.

Eur J Oral Sci 2020 04 10;128(2):160-169. Epub 2020 Mar 10.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.

The aim of this study was to evaluate the hydrophilicity, surface free energy, and proliferation and viability of human osteoblast-like MC3T3-E1 cells on sandblasted and acid-etched titanium surfaces after air-abrasion with 45S5 bioactive glass, zinc-containing bioactive glass, or inert glass. Sandblasted and acid-etched titanium discs were subjected to air-abrasion with 45S5 bioactive glass, experimental bioactive glass (Zn4), or inert glass. Water contact angles and surface free energy were evaluated. The surfaces were studied with preosteoblastic MC3T3-E1 cells. Air-abrasion with either type of glass significantly enhanced the hydrophilicity and surface free energy of the sandblasted and acid-etched titanium discs. The MC3T3-E1 cell number was higher for substrates air-abraded with Zn4 bioactive glass and similar to that observed on borosilicate coverslips (controls). Confocal laser scanning microscopy images showed that MC3T3-E1 cells did not spread as extensively on the sandblasted and acid-etched and bioactive glass-abraded surfaces as they did on control surfaces. However, for 45S5- and Zn4-treated samples, the cells spread most at the 24 h time point and changed their morphology to more spindle-like when cultured further. Air-abrasion with bioactive glass and inert glass was shown to have a significant effect on the wettability and surface free energy of the surfaces under investigation. Osteoblast cell proliferation on sandblasted and acid-etched titanium discs was enhanced by air-abrasion with 45S5 bioactive glass and experimental Zn4 bioactive glass compared with air-abrasion with inert glass or no air-abrasion.
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http://dx.doi.org/10.1111/eos.12683DOI Listing
April 2020

Bioactive Glass (BG) ICIE16 Shows Promising Osteogenic Properties Compared to Crystallized 45S5-BG.

Int J Mol Sci 2020 Feb 28;21(5). Epub 2020 Feb 28.

Institute of Biomaterials, University of Erlangen-Nuremberg, Cauerstr. 6, 91058 Erlangen, Germany.

The ICIE16-bioactive glass (BG) (48.0 SiO, 6.6 NaO, 32.9 CaO, 2.5 PO, 10.0 KO (wt %)) has been developed as an alternative to 45S5-BG, the original BG composition (45.0 SiO, 24.5 NaO, 24.5 CaO, 6.0 PO (wt %)), with the intention of broadening the BG sintering window while maintaining bioactivity. Because there is a lack of reports on ICIE16-BG biological properties, the influence of ICIE16-BG on viability, proliferation, and osteogenic differentiation of human mesenchymal stromal cells (MSCs) was evaluated in direct comparison to 45S5-BG in this study. The BGs underwent heat treatment similar to that which is required in order to fabricate scaffolds by sintering, which resulted in crystallization of 45S5-BG (45S5-CBG) while ICIE16 remained amorphous. Granules based on both BGs were biocompatible, but ICIE16-BG was less harmful to cell viability, most likely due to a more pronounced pH alkalization in the 45S5-CBG group. ICIE16-BG outperformed 45S5-CBG in terms of osteogenic differentiation at the cellular level, as determined by the increased activity of alkaline phosphatase. However, granules from both BGs were comparable regarding the stimulation of expression levels of genes encoding for osseous extracellular matrix (ECM) proteins. The addition of therapeutically active ions to ICIE16-BG might further improve its ability to stimulate ECM production and should be investigated in upcoming studies.
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http://dx.doi.org/10.3390/ijms21051639DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084569PMC
February 2020

Air Abrasion With Bioactive Glass Eradicates Biofilm From a Sandblasted and Acid-Etched Titanium Surface.

J Oral Implantol 2019 Dec 19;45(6):444-450. Epub 2019 Sep 19.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Finland.

is able to form a high-affinity biofilm on material surfaces. has also been detected around infected implants. Bioactive glasses (BAGs) have been shown to possess antibacterial effects against and other microorganisms. This in vitro study was performed to investigate the influence of BAG air abrasion on biofilm on sandblasted and acid-etched titanium surfaces. Sandblasted and acid-etched commercially pure titanium discs were used as substrates for bacteria (n = 107). The discs were immersed in an solution and incubated for 21 hours to form an biofilm. Twenty colonized discs were subjected to air abrasion with Bioglass 45S5 (45S5 BAG), experimental zinc oxide containing BAG (Zn4 BAG), and inert glass. After the abrasion, the discs were incubated for 5 hours in an anaerobic chamber followed by an assessment of viable cells. Surface morphology was evaluation using scanning electron microscopy (n = 12). The thrombogenicity of the glass particle-abraded discs (n = 75) was evaluated spectrophotometrically using whole-blood clotting measurement at predetermined time points. Air abrasion with 45S5 and Zn4 BAG eradicated biofilm. Significantly fewer viable cells were found on discs abraded with the 45S5 or Zn4 BAGs compared with the inert glass ( < .001). No significant differences were found in thrombogenicity since blood clotting was achieved for all substrates at 40 minutes. Air abrasion with BAG particles is effective in the eradication of biofilm from sandblasted and acid-etched titanium surfaces. Zn4 and 45S5 BAGs had similar biofilm-eradicating effects, but Zn4 BAG could be more tissue friendly. In addition, the steady release of zinc ions from Zn4 may enhance bone regeneration around the titanium implant and may thus have the potential to be used in the treatment of peri-implantitis. The use of either BAGs did not enhance the speed of blood coagulation.
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http://dx.doi.org/10.1563/aaid-joi-D-18-00324DOI Listing
December 2019

3D Scaffolds of Polycaprolactone/Copper-Doped Bioactive Glass: Architecture Engineering with Additive Manufacturing and Cellular Assessments in a Coculture of Bone Marrow Stem Cells and Endothelial Cells.

ACS Biomater Sci Eng 2019 Sep 2;5(9):4496-4510. Epub 2019 Aug 2.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia.

The local delivery of Cu from copper-doped bioactive glass (Cu-BaG) was combined with 3D printing of polycaprolactone (PCL) scaffolds for its potent angiogenic effect in bone tissue engineering. PCL and Cu-BaG were, respectively, dissolved and dispersed in acetone to formulate a moderately homogeneous ink. The PCL/Cu-BaG scaffolds were fabricated via direct ink writing into a cold ethanol bath. The architecture of the printed scaffolds, including strut diameter, strut spacing, and porosity, were investigated and characterized. The PCL/Cu-BaG scaffolds showed a Cu-BaG content-dependent mechanical property, as the compressive Young's modulus ranged from 7 to 13 MPa at an apparent porosity of 60%. The ion dissolution behavior in simulated body fluid was evaluated, and the hydroxyapatite-like precipitation on the strut surface was confirmed. Furthermore, the cytocompatibility of the PCL/Cu-BaG scaffolds was assessed in human bone marrow stem cell (hBMSC) culture, and a dose-dependent cytotoxicity of Cu was observed. Here, the PCL/BaG scaffold induced the higher expression of late osteogenic genes and in comparison to the PCL scaffold. The doping of Cu in BaG elicited higher expression of the early osteogenic marker gene but decreased the expression of late osteogenic marker genes and in comparison to the PCL/BaG scaffold, demonstrating the suppressing effect of Cu on osteogenic differentiation of hBMSCs. In a coculture of hBMSCs and human umbilical vein endothelial cells, both the PCL/BaG and PCL/Cu-BaG scaffolds stimulated the formation of a denser tubule network, compared to the PCL scaffold. Meanwhile, only slightly higher gene expression of was observed with the PCL/Cu-BaG scaffold than with the PCL/BaG scaffold, indicating the potent angiogenic effect of the released Cu.
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http://dx.doi.org/10.1021/acsbiomaterials.9b00105DOI Listing
September 2019

Bioactive glass ions for in vitro osteogenesis and microvascularization in gellan gum-collagen hydrogels.

J Biomed Mater Res B Appl Biomater 2020 05 31;108(4):1332-1342. Epub 2019 Aug 31.

Adult Stem Cell Group, BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.

Lack of bone grafts appeals for bone augmentation solutions. We aimed at osteogenic differentiation of human adipose stem cells (hASCs) and microvascularization in coculture with human umbilical vein endothelial cells (HUVECs) embedded in three-dimensional (3D) gellan gum (GG) and collagen type I (COL) hydrogel mixture. We compared endothelial growth medium-2 (EGM-2) and bioactive glass extract-based endothelial and osteogenic medium (BaG EM-OM) for vascularized bone-like graft development in vitro. Cell viability, cell number, and osteogenic and endothelial gene expression were analyzed. Mineralized hydroxyapatite residues, immunocytochemical staining of endothelial marker CD31 production and late osteogenic marker osteocalcin were imaged. With both media, good cell viability was observed within 3D hydrogel. EGM-2 condition induced significantly higher cell number compared to BaG EM-OM condition at both 7 and 14 days. Interestingly, both media supported osteogenic as well as endothelial marker gene expression. Moreover, formation of reticulated cellular structures was observed in both EGM-2 and BaG EM-OM conditions. However, hydroxyapatite mineralization and strong osteocalcin staining were detected only in BaG EM-OM condition. Importantly, strong production of CD31 and elongated tube-like structures were apparent in EGM-2 culture alone. In conclusion, we demonstrated efficient hASC osteogenic differentiation and microvessel-like network formation in coculture with HUVECs.
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http://dx.doi.org/10.1002/jbm.b.34482DOI Listing
May 2020

Bioactive glass ions induce efficient osteogenic differentiation of human adipose stem cells encapsulated in gellan gum and collagen type I hydrogels.

Mater Sci Eng C Mater Biol Appl 2019 Jun 13;99:905-918. Epub 2019 Feb 13.

Adult Stem Cell Group, BioMediTech, Faculty of Medicine and Health Technology, Tampere University, P.O. BOX 100, FI-33014 Tampere, Finland; Research, Development and Innovation Centre, Tampere University Hospital, P.O. BOX 2000, FI-33521, Tampere, Finland. Electronic address:

Background: Due to unmet need for bone augmentation, our aim was to promote osteogenic differentiation of human adipose stem cells (hASCs) encapsulated in gellan gum (GG) or collagen type I (COL) hydrogels with bioactive glass (experimental glass 2-06 of composition [wt-%]: NaO 12.1, KO 14.0, CaO 19.8, PO5 2.5, BO 1.6, SiO 50.0) extract based osteogenic medium (BaG OM) for bone construct development. GG hydrogels were crosslinked with spermidine (GG-SPD) or BaG extract (GG-BaG).

Methods: Mechanical properties of cell-free GG-SPD, GG-BaG, and COL hydrogels were tested in osteogenic medium (OM) or BaG OM at 0, 14, and 21 d. Hydrogel embedded hASCs were cultured in OM or BaG OM for 3, 14, and 21 d, and analyzed for viability, cell number, osteogenic gene expression, osteocalcin production, and mineralization. Hydroxyapatite-stained GG-SPD samples were imaged with Optical Projection Tomography (OPT) and Selective Plane Illumination Microscopy (SPIM) in OM and BaG OM at 21 d. Furthermore, Raman spectroscopy was used to study the calcium phosphate (CaP) content of hASC-secreted ECM in GG-SPD, GG-BaG, and COL at 21 d in BaG OM.

Results: The results showed viable rounded cells in GG whereas hASCs were elongated in COL. Importantly, BaG OM induced significantly higher cell number and higher osteogenic gene expression in COL. In both hydrogels, BaG OM induced strong mineralization confirmed as CaP by Raman spectroscopy and significantly improved mechanical properties. GG-BaG hydrogels rescued hASC mineralization in OM. OPT and SPIM showed homogeneous 3D cell distribution with strong mineralization in BaG OM. Also, strong osteocalcin production was visible in COL.

Conclusions: Overall, we showed efficacious osteogenesis of hASCs in 3D hydrogels with BaG OM with potential for bone-like grafts.
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http://dx.doi.org/10.1016/j.msec.2019.02.035DOI Listing
June 2019

S53P4 Bioactive Glass Inorganic Ions for Vascularized Bone Tissue Engineering by Dental Pulp Pluripotent-Like Stem Cell Cocultures.

Tissue Eng Part A 2019 09 27;25(17-18):1213-1224. Epub 2019 Feb 27.

Adult Stem Cell Research Group, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.

Impact Statement: In this study, we proposed for the first time the use of inorganic ions dissolved from BaG in a cell coculture system to induce vascularized bone formation For that, we used dental pulp pluripotent-like stem cells from a single individual source obtained in a minimally invasive extraction manner. Moreover, we carried out all the experiments under xeno-free conditions, allowing the extrapolation of the results to the development of clinically orientated applications. Overall, these results would provide a new promising system to promote the success and survival of bone tissue engineering constructs after implantation.
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http://dx.doi.org/10.1089/ten.TEA.2018.0256DOI Listing
September 2019

Bone morphogenic protein expression and bone formation are induced by bioactive glass S53P4 scaffolds in vivo.

J Biomed Mater Res B Appl Biomater 2019 04 8;107(3):847-857. Epub 2018 Sep 8.

Department of Musculoskeletal and Plastic Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.

The two-stage induced-membrane (IM) technique is increasingly used for treatment of large bone defects. In stage one, the bone defect is filled with polymethylmethacrylate (PMMA), which induces a membrane around the implant. In stage two, PMMA is replaced with bone graft. Bioactive glasses (BAGs) are bone substitutes with bone-stimulating and angiogenic properties. We have previously shown that a certain type of BAG can also induce a foreign-body membrane similar to PMMA. The aim of this study was to evaluate the bone-forming capacity of sintered BAG-S53P4 and poly(lactide-co-glycolide) (PLGA)-coated BAG-S53P4 scaffolds for potential use as bone substitutes in a single-stage IM technique. Sintered porous rods of BAG-S53P4, BAG-S53P4-PLGA, or PMMA were implanted in rabbit femurs for 2, 4, or 8 weeks. The expression of bone morphogenic protein (BMP)-2, -4, and -7 in the IMs of implanted materials were analyzed with real-time quantitative polymerase chain reaction. Micro-computed tomography imaging was used to evaluate bone growth and further verified with scanning electron microscopy. BAG-S53P4 and BAG-S53P4-PGLA scaffold IMs show similar or superior expression of BMP-2, -4, and -7 compared with PMMA IM. Bone ingrowth into BAG scaffolds increased over time. Active bone formation occurred inside the BAG scaffolds and the respective BMP expressions were similar or superior for the BAG IMs compared with PMMA, thus making BAGs a promising device for single-stage treatment of bone defects. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 847-857, 2019.
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http://dx.doi.org/10.1002/jbm.b.34181DOI Listing
April 2019

Dissolution and mineralization characterization of bioactive glass ceramic containing endodontic sealer Guttaflow Bioseal.

Dent Mater J 2018 Nov 29;37(6):988-994. Epub 2018 Aug 29.

Department of Biomaterials Science and Turku Clinical Biomaterials Center-TCBC, Institute of Dentistry, University of Turku.

Aim of the study was to evaluate apatite forming ability and ion dissolution of bioactive glass-ceramic (BGC) particles from novel polydimethylsiloxane (PDMS) based endodontic sealer Guttaflow Bioseal. Firstly, water sorption and solubility were determined for Guttaflow 2 and Guttaflow Bioseal (GB), the latter containing BGC filler particles. Mineral precipitations in simulated body fluid (SBF) were observed with SEM/EDX. Ion-release from the sealer was determined with inductively coupled plasma optical emission spectrometry (ICP-OES) in Tris-buffer solution. Change in pH was also measured. The obtained data was statistically analyzed with Tukey's HSD test (p<0.05). GB exhibited significantly higher water sorption and solubility in comparison with Guttaflow 2. Surface structure exposed particles of BGC in the PDMS matrix. The BGC particles (size of 20-40 μm) indicated to consist of CaO-SiO-NaO-ZrO-PO. Morphologically spherical Ca/P precipitation formed after 3 days in the SBF on the sealer surface. Ca/P ratio of the precipitation ranged in 1.20-1.65 indicating transformation to hydroxyapatite (HA). The pH of the immersion solution rose gradually.
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http://dx.doi.org/10.4012/dmj.2017-224DOI Listing
November 2018

Bioactive dental materials-Do they exist and what does bioactivity mean?

Dent Mater 2018 05 20;34(5):693-694. Epub 2018 Mar 20.

Department Biomaterials Science and Turku Clinical Biomaterial Centre-TCBC, Institute of Dentistry, University of Turku and City of Turku, Welfare Division, Lemminkäisenkatu 2, FI-20520 Turku, Finland; Institute of Biomaterials, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany; Johan Gadolin Process Chemistry Centre, Abo Akademi University, Turku, Finland; School of Medical Sciences, University of Manchester, Manchester, UK.

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http://dx.doi.org/10.1016/j.dental.2018.03.001DOI Listing
May 2018

A process for producing lignin and volatile compounds from hydrolysis liquor.

Biotechnol Biofuels 2017 23;10:47. Epub 2017 Feb 23.

Chemical Engineering Department, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada.

Background: Hot water hydrolysis process is commercially applied for treating wood chips prior to pulping or wood pellet production, while it produces hydrolysis liquor as a by-product. Since the hydrolysis liquor is dilute, the production of value-added materials from it would be challenging.

Results: In this study, acidification was proposed as a viable method to extract (1) furfural and acetic acid from hot water hydrolysis liquor and (2) lignin compounds from the liquor. The thermal properties of the precipitates made from the acidification of hydrolysis liquor confirmed the volatile characteristics of precipitates. Membrane dialysis was effective in removing inorganic salts associated with lignin compounds. The purified lignin compounds had a glass transition temperature (Tg) of 180-190 °C, and were thermally stable.

Conclusions: The results confirmed that lignin compounds present in hot water hydrolysis liquor had different characteristics. The acidification of hydrolysis liquor primarily removed the volatile compounds from hydrolysis liquor. Based on these results, a process for producing purified lignin and precipitates of volatile compounds was proposed.
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http://dx.doi.org/10.1186/s13068-017-0729-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322682PMC
February 2017

Compression properties and dissolution of bioactive glass S53P4 and n-butyl-2 cyanoacrylate tissue adhesive-composite.

Biomed Mater Eng 2016 Sep;27(4):425-436

BioCity, Turku Biomaterials Research Program, Turku Clinical Biomaterials Centre - TCBC, Finland.

Bioactive glass (BG)-containing fiber-reinforced composite implants, typically screw-retained, have started to be used clinically. In this study, we tested the mechanical strength of composites formed by a potential implant adhesive of n-butyl-2-cyanoacrylate glue and BG S53P4 particles. Water immersion for 3, 10 or 30 days had no adverse effect on the compression strength. When cyanoacrylate glue-BG-composites were subjected to simulated body fluid immersion, the average pH rose to 7.52 (SD 0.066) from the original value of 7.35 after 7 days, and this pH increment was smaller compared to BG particle-group or fibrin glue-BG-composite group. Based on these results n-butyl-2 cyanoacrylate glue, by potentially producing a strong adhesion, might be considered a possible alternative for fixation of BG S53P4 containing composite implants. However, the mechanical and solubility properties of the cyanoacrylate glue may not encourage the use of this tissue adhesive with BG particles.
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http://dx.doi.org/10.3233/BME-161596DOI Listing
September 2016

Biocomposites of copper-containing mesoporous bioactive glass and nanofibrillated cellulose: Biocompatibility and angiogenic promotion in chronic wound healing application.

Acta Biomater 2016 12 17;46:286-298. Epub 2016 Sep 17.

Johan Gadolin Process Chemistry Centre, Åbo Akademi University, FI-20500 Åbo/Turku, Finland.

Biocomposites of copper-containing mesoporous bioactive glass (Cu-MBG) and nanofibrillated cellulose (NFC) were designated as potential dressing material for chronic wound healing. The phase composition and mesoporous micro-structure of the synthesized Cu-MBGs were elaborately characterized by combining several techniques, including TEM, SEM, XRD, SXAS and N physisorption. High bioactivity of the Cu-MBG was confirmed in stimulated body fluids in vitro. A controlled dissolution of Cu from the glass suggests Cu-MBG a suitable source for Cu release in wound healing dressings. Depending on the content of Cu-MBG in the composite formulation, the composites were fabricated as membranes and aerogels. In biocompatibility assessment of the composites, a dose-dependent cytotoxicity of Cu on 3T3 fibroblasts was found. Importantly, a critical biological level of Cu below 10mg/L was suggested for the survival and growth of 3T3 fibroblasts. The Cu released from the composite aerogel of NFC and Cu-MBG showed a profound angiogenic effect in the 3D spheroid culture system of human umbilical vein endothelial cells. Moreover, the angiogenic gene expression of 3T3 fibroblast was upregulated in the real-time quantitative PCR analysis, which also confirms that the incorporation of Cu-MBG into NFC matrix enhances the proangiogenic potential of the biocomposites. In addition, composites of NFC and Cu-MBG also showed an inhibiting effect on the growth of E. coli.

Statement Of Significance: To address an urgent need in clinics on developing a new generation of therapeutic dressings with advanced functionalities, this study has exploited the utilization of Cu-containing mesoporous bioactive glass in the nanocellulose matrix to release Cu as therapeutic ions for its angiogenic effect on promoting wound healing. This manuscript reports research work on biomaterial design, fabrication development, material characterizations and bioassessments in 2D cellular studies. To utilize nanocellulose derived from the wood resource in biomedical applications is of great significance, due to its vast availability and bioeconomy competence. The use of Cu-containing bioactive glass in tissue engineering scaffolds, including wound healing, is an intriguing research topic, which has been recently discussed in the field of biomaterials. I think that our manuscript title with 'Biocomposites of copper-containing mesoporous bioactive glass and nanofibrillated cellulose: biocompatibility and angiogenic promotion in chronic wound healing application' will make its own contribution on understanding the complex effects of Cu on wound-healing-relevant events with acceptable novelty for Acta Biomaterialia.
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http://dx.doi.org/10.1016/j.actbio.2016.09.021DOI Listing
December 2016

Controlling the ion release from mixed alkali bioactive glasses by varying modifier ionic radii and molar volume.

J Mater Chem B 2016 May 29;4(18):3121-3134. Epub 2016 Mar 29.

Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena, Germany.

Partially substituting one alkali oxide for another reduces the crystallisation tendency and improves the processing of bioactive glasses. Here, we investigate how we can use alkali ions of varying ionic radii to control glass degradation and ion release from Bioglass 45S5. Partially replacing sodium by lithium reduced ion release in static and dynamic dissolution studies in Tris buffer, while ion release increased with increasing potassium for sodium substitution. While the mixed alkali effect is known to reduce ion release from conventional silicate glasses (compared to compositions containing one alkali oxide only), in the glasses studied here ion release was controlled by the packing of the silicate network, described by glass molar volume and oxygen density. Incorporating an alkali ion of smaller ionic radius (Li for Na or Na for K) resulted in a more compact network of higher oxygen density, which reduced ion release. On the other hand, an alkali ion of larger ionic radius (K for Na or Na for Li) expanded the silicate network, allowing for faster ion release. This can be explained by water molecules penetrating an expanded silicate network more easily than a more compact one, thereby directly influencing the ion exchange between modifier ions and protons from the dissolution medium. This shows that the use of modifier ions of varying ionic radii allows for tailoring bioactive glass ion release and degradation while maintaining silicate network polymerisation and network connectivity. And, indeed, recent literature suggests that this concept can be extended to other modifiers besides alkali metal ions, making it possible to design bioactive glasses of tailored solubility.
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http://dx.doi.org/10.1039/c5tb02426aDOI Listing
May 2016

Porous SiO2 nanofiber grafted novel bioactive glass-ceramic coating: A structural scaffold for uniform apatite precipitation and oriented cell proliferation on inert implant.

Mater Sci Eng C Mater Biol Appl 2016 May 22;62:206-14. Epub 2016 Jan 22.

Turku Clinical Biomaterials Centre-TCBC, University of Turku, FI-20520 Turku, Finland; Institute of Dentistry, University of Turku, Department of Biomaterials Science and City of Turku, Welfare Division, Turku, Finland.

A composite bioactive glass-ceramic coating grafted with porous silica nanofibers was fabricated on inert glass to provide a structural scaffold favoring uniform apatite precipitation and oriented cell proliferation. The coating surfaces were investigated thoroughly before and after immersion in simulated body fluid. In addition, the proliferation behavior of fibroblast cells on the surface was observed for several culture times. The nanofibrous exterior of this composite bioactive coating facilitated homogeneous growth of flake-like carbonated hydroxyapatite layer within a short period of immersion. Moreover, the embedded porous silica nanofibers enhanced hydrophilicity which is required for proper cell adhesion on the surface. The cells proliferated well following a particular orientation on the entire coating by the assistance of nanofibrous scaffold-like structural matrix. This newly engineered composite coating was effective in creating a biological structural matrix favorable for homogeneous precipitation of calcium phosphate, and organized cell growth on the inert glass surface.
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http://dx.doi.org/10.1016/j.msec.2016.01.053DOI Listing
May 2016

A glass fiber-reinforced composite - bioactive glass cranioplasty implant: A case study of an early development stage implant removed due to a late infection.

J Mech Behav Biomed Mater 2015 Mar 7;55:191-200. Epub 2015 Nov 7.

Department of Otorhinolaryngology - Head and Neck Surgery, Division of Surgery and Cancer Diseases, Turku University Hospital, PO Box 52, 20521 Turku, Finland; City of Turku Welfare Division, PO Box 670, 20101 Turku, Finland.

This case study describes the properties of an early development stage bioactive glass containing fiber-reinforced composite calvarial implant with histology that has been in function for two years and three months. The patient is a 33-year old woman with a history of substance abuse, who sustained a severe traumatic brain injury later unsuccessfully treated with an autologous bone flap and a custom-made porous polyethylene implant. She was thereafter treated with developmental stage glass fiber-reinforced composite - bioactive glass implant. After two years and three months, the implant was removed due to an implant site infection. The implant was analyzed histologically, mechanically, and in terms of chemistry and dissolution of bioactive glass. Mechanical integrity of the load bearing fiber-reinforced composite part of the implant was not affected by the in vivo period. Bioactive glass particles demonstrated surface layers of hydroxyapatite like mineral and dissolution, and related increase of pH was considerably less after two and three months period than that for fresh bioactive glass. There was a difference in the histology of the tissues inside the implant areas near to the margin of the implant that absorbed blood during implant installation surgery, showed fibrous tissue with blood vessels, osteoblasts, collagenous fibers with osteoid formation, and tiny clusters of more mature hard tissue. In the center of the implant, where there was less absorbed blood, only fibrous tissue was observed. This finding is in line with the combined positron emission tomography - computed tomography examination with (18F)-fluoride marker, which demonstrated activity of the mineralizing bone by osteoblasts especially at the area near to the margin of the implant 10 months after implantation. Based on these promising reactions found in the bioactive glass containing fiber-reinforced composite implant that has been implanted for two years and three months, calvarial reconstruction with the presented material appears to be a feasible method.
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http://dx.doi.org/10.1016/j.jmbbm.2015.10.030DOI Listing
March 2015

Impact of gastric acidic challenge on surface topography and optical properties of monolithic zirconia.

Dent Mater 2015 Dec 20;31(12):1445-52. Epub 2015 Oct 20.

Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Centre (TCBC), University of Turku and City of Turku, Finland; Clinic of Oral Diseases, Turku University Central Hospital, Turku, Finland.

Objective: To evaluate the surface topography and optical properties of monolithic zirconia after immersion in simulated gastric acid.

Materials And Methods: Four partially stabilized (PSZ) and one fully stabilized (FSZ) zirconia materials were selected for the study: Prettau (PRT, Zirkonzahn), Zenostar (ZEN, Ivoclar), Bruxzir (BRX, Glidewell), Katana (KAT, Noritake) and FSZ Prettau Anterior (PRTA, Zirkonzahn). IPS e.max (Ivoclar) was used as a control. The specimens (10×10×1.2mm, n=5 per material) were cut, sintered, polished and cleaned before immersed in 5ml of simulated gastric acid solution (Hydrochloric acid (HCl) 0.06M, 0.113% solution in deionized distal water, pH 1.2) for 96h in a 37°C incubator. Specimens were weighed and examined for morphological changes under scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Surface roughness was evaluated by a confocal microscope. Surface gloss and translucency parameter (TP) values were determined by a reflection spectrophotometer before and after acid immersion. The data was analyzed by one-way ANOVA followed by Tukey's HSD post hoc test (p<0.05).

Results: PRTA displayed the most weight loss (1.40%) among the zirconia specimens. IPS e.max showed about three times more weight loss (3.05%) than zirconia specimens as an average. SEM examination indicated areas of degradation, bead-like shapes and smoothening of the polishing scratches after acid immersion. EDX displayed ion interactions and possible ion leaching from all specimens. Sa and Sq values for PRTA, ZEN and IPS e.max were significantly lower (p<0.05) after acid immersion. TP values increased significantly for PRT, ZEN and IPS e.max (p<0.05), while the surface gloss of ZEN, PRTA and IPS e.max increased (p<0.05).

Significance: Monolithic zirconia materials show some surface alterations in an acidic environment with minimum effect on their optical properties. Whether a smoother surface is in fact a sign of true corrosion resistance or is purely the result of an evenly progressive corrosive process is yet to be confirmed by further research.
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http://dx.doi.org/10.1016/j.dental.2015.09.010DOI Listing
December 2015

Bioactive glass ions as strong enhancers of osteogenic differentiation in human adipose stem cells.

Acta Biomater 2015 Jul 18;21:190-203. Epub 2015 Apr 18.

Adult Stem Cell Research Group, University of Tampere, Tampere, Finland; BioMediTech, University of Tampere and Tampere University of Technology, Tampere, Finland; Science Centre, Tampere University Hospital, Tampere, Finland; Science Centre, Tampere University Hospital, Tampere, Finland.

Bioactive glasses are known for their ability to induce osteogenic differentiation of stem cells. To elucidate the mechanism of the osteoinductivity in more detail, we studied whether ionic extracts prepared from a commercial glass S53P4 and from three experimental glasses (2-06, 1-06 and 3-06) are alone sufficient to induce osteogenic differentiation of human adipose stem cells. Cells were cultured using basic medium or osteogenic medium as extract basis. Our results indicate that cells stay viable in all the glass extracts for the whole culturing period, 14 days. At 14 days the mineralization in osteogenic medium extracts was excessive compared to the control. Parallel to the increased mineralization we observed a decrease in the cell amount. Raman and Laser Induced Breakdown Spectroscopy analyses confirmed that the mineral consisted of calcium phosphates. Consistently, the osteogenic medium extracts also increased osteocalcin production and collagen Type-I accumulation in the extracellular matrix at 13 days. Of the four osteogenic medium extracts, 2-06 and 3-06 induced the best responses of osteogenesis. However, regardless of the enhanced mineral formation, alkaline phosphatase activity was not promoted by the extracts. The osteogenic medium extracts could potentially provide a fast and effective way to differentiate human adipose stem cells in vitro.
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http://dx.doi.org/10.1016/j.actbio.2015.04.017DOI Listing
July 2015

Fiber glass-bioactive glass composite for bone replacing and bone anchoring implants.

Dent Mater 2015 Apr 29;31(4):371-81. Epub 2015 Jan 29.

Laboratory of Inorganic Chemistry, Process Chemistry Centre, Åbo Akademi University, Turku, Finland.

Objective: Although metal implants have successfully been used for decades, devices made out of metals do not meet all clinical requirements, for example, metal objects may interfere with some new medical imaging systems, while their stiffness also differs from natural bone and may cause stress-shielding and over-loading of bone.

Methods: Peer-review articles and other scientific literature were reviewed for providing up-dated information how fiber-reinforced composites and bioactive glass can be utilized in implantology.

Results: There has been a lot of development in the field of composite material research, which has focused to a large extent on biodegradable composites. However, it has become evident that biostable composites may also have several clinical benefits. Fiber reinforced composites containing bioactive glasses are relatively new types of biomaterials in the field of implantology. Biostable glass fibers are responsible for the load-bearing capacity of the implant, while the dissolution of the bioactive glass particles supports bone bonding and provides antimicrobial properties for the implant. These kinds of combination materials have been used clinically in cranioplasty implants and they have been investigated also as oral and orthopedic implants.

Significance: The present knowledge suggests that by combining glass fiber-reinforced composite with particles of bioactive glass can be used in cranial implants and that the combination of materials may have potential use also as other types of bone replacing and repairing implants.
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http://dx.doi.org/10.1016/j.dental.2015.01.003DOI Listing
April 2015

Influence of SrO substitution for CaO on the properties of bioactive glass S53P4.

J Mater Sci Mater Med 2014 Mar 12;25(3):657-68. Epub 2013 Dec 12.

Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500, Turku, Finland,

Commercial melt-quenched bioactive glasses consist of the oxides of silicon, phosphorus, calcium and sodium. Doping of the glasses with oxides of some other elements is known to affect their capability to support hydroxyapatite formation and thus bone tissue healing but also to modify their high temperature processing parameters. In the present study, the influence of gradual substitution of SrO for CaO on the properties of the bioactive glass S53P4 was studied. Thermal analysis and hot stage microscopy were utilized to measure the thermal properties of the glasses. The in vitro bioactivity and solubility was measured by immersing the glasses in simulated body fluid for 6 h to 1 week. The formation of silica rich and hydroxyapatite layers was assessed from FTIR spectra analysis and SEM images of the glass surface. Increasing substitution of SrO for CaO decreased all characteristic temperatures and led to a slightly stronger glass network. The initial glass dissolution rate increased with SrO content. Hydroxyapatite layer was formed on all glasses but on the SrO containing glasses the layer was thinner and contained also strontium. The results suggest that substituting SrO for CaO in S53P4 glass retards the bioactivity. However, substitution greater than 10 mol% allow for precipitation of a strontium substituted hydroxyapatite layer.
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http://dx.doi.org/10.1007/s10856-013-5120-1DOI Listing
March 2014

In vitro blood and fibroblast responses to BisGMA-TEGDMA/bioactive glass composite implants.

J Mater Sci Mater Med 2014 Jan;25(1):151-62

This in vitro study was designed to evaluate both blood and human gingival fibroblast responses to bisphenol A-glycidyl methacrylate-triethyleneglycol dimethacrylate (BisGMA-TEGDMA)/bioactive glass (BAG) composite, aimed to be used as composite implant abutment surface modifier. Three different types of substrates were investigated: (a) plain polymer (BisGMA 50 wt%-TEGDMA 50 wt%), (b) BAG-composite (50 wt% polymer + 50 wt% fraction of BAG-particles, <50 μm), and (c) plain BAG plates (100 wt% BAG). The blood response, including the blood-clotting ability and platelet adhesion morphology were evaluated. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 10 days, then the cell proliferation rate was assessed using AlamarBlue assay™. The BAG-composite and plain BAG substrates had a shorter clotting time than plain polymer substrates. Platelet activation and aggregation were most extensive, qualitatively, on BAG-composite. Analysis of the normalized cell proliferation rate on the different surfaces showed some variations throughout the experiment, however, by day 10 the BAG-composite substrate showed the highest (P < 0.001) cell proliferation rate. In conclusion, the presence of exposed BAG-particles enhances fibroblast and blood responses on composite surfaces in vitro.
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http://dx.doi.org/10.1007/s10856-013-5040-0DOI Listing
January 2014

Examining porous bio-active glass as a potential osteo-odonto-keratoprosthetic skirt material.

J Mater Sci Mater Med 2013 May 6;24(5):1217-27. Epub 2013 Feb 6.

BioCity Turku Biomaterials Research Program, Institute of Dentistry, Turku Clinical Biomaterials Centre-TCBC, University of Turku, Turku, Finland.

Bio-active glass has been developed for use as a bone substitute with strong osteo-inductive capacity and the ability to form strong bonds with soft and hard tissue. The ability of this material to enhance tissue in-growth suggests its potential use as a substitute for the dental laminate of an osteo-odonto-keratoprosthesis. A preliminary in vitro investigation of porous bio-active glass as an OOKP skirt material was carried out. Porous glass structures were manufactured from bio-active glasses 1-98 and 28-04 containing varying oxide formulation (1-98, 28-04) and particle size range (250-315 μm for 1-98 and 28-04a, 315-500 μm for 28-04b). Dissolution of the porous glass structure and its effect on pH was measured. Structural 2D and 3D analysis of porous structures were performed. Cell culture experiments were carried out to study keratocyte adhesion and the inflammatory response induced by the porous glass materials. The dissolution results suggested that the porous structure made out of 1-98 dissolves faster than the structures made from glass 28-04. pH experiments showed that the dissolution of the porous glass increased the pH of the surrounding solution. The cell culture results showed that keratocytes adhered onto the surface of each of the porous glass structures, but cell adhesion and spreading was greatest for the 98a bio-glass. Cytokine production by all porous glass samples was similar to that of the negative control indicating that the glasses do not induce a cytokine driven inflammatory response. Cell culture results support the potential use of synthetic porous bio-glass as an OOKP skirt material in terms of limited inflammatory potential and capacity to induce and support tissue ingrowth.
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http://dx.doi.org/10.1007/s10856-013-4881-xDOI Listing
May 2013

Multi-layer porous fiber-reinforced composites for implants: in vitro calcium phosphate formation in the presence of bioactive glass.

Dent Mater 2012 Nov 25;28(11):1134-45. Epub 2012 Aug 25.

Department of Biomaterials Science, University of Turku, Turku, Finland.

Objectives: Glass-fiber-reinforced composites (FRCs), based on bifunctional methacrylate resin, have recently shown their potential for use as durable cranioplasty, orthopedic and oral implants. In this study we suggest a multi-component sandwich implant structure with (i) outer layers out of porous FRC, which interface the cortical bone, and (ii) inner layers encompassing bioactive glass granules, which interface with the cancellous bone.

Methods: The capability of Bioglass(®) 45S5 granules (100-250μm) to induce calcium phosphate formation on the surface of the FRC was explored by immersing the porous FRC-Bioglass laminates in simulated body fluid (SBF) for up to 28d.

Results: In both static (agitated) and dynamic conditions, bioactive glass granules induced precipitation of calcium phosphate at the laminate surfaces as confirmed by scanning electron microscopy.

Significance: The proposed dynamic flow system is useful for the in vitro simulation of bone-like apatite formation on various new porous implant designs containing bioactive glass and implant material degradation.
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http://dx.doi.org/10.1016/j.dental.2012.08.005DOI Listing
November 2012

In vitro behaviour of three biocompatible glasses in composite implants.

J Mater Sci Mater Med 2012 Oct 6;23(10):2425-35. Epub 2012 Jun 6.

Process Chemistry Centre, Åbo Akademi University, 20500 Turku, Finland.

Poly(L,DL-lactide) composites containing filler particles of bioactive glasses 45S5 and S53P4 were compared with a composite containing a slowly dissolving glass S68. The in vitro reactivity of the composites was studied in simulated body fluid, Tris-buffered solution, and phosphate buffered saline. The high processing temperature induced thermal degradation giving cavities in the composites containing 45S5 and S53P4, while good adhesion of S68 to the polymer was observed. The cavities partly affected the in vitro reactivity of the composites. The degradation of the composites containing the bioactive glasses was faster in phosphate buffered saline than in the two other solutions. Hydroxyapatite precipitation suggesting bone tissue bonding capability was observed on these two composites in all three solutions. The slower dissolution of S68 glass particles and the limited hydroxyapatite precipitation suggested that this glass has potential as a reinforcing composition with the capability to guide bone tissue growth in biodegradable polymer composites.
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http://dx.doi.org/10.1007/s10856-012-4693-4DOI Listing
October 2012

Bioactive composite for keratoprosthesis skirt.

J Mech Behav Biomed Mater 2011 Nov 21;4(8):1700-8. Epub 2011 Jun 21.

Turku Clinical Biomaterials Centre-TCBC, Department of Biomaterials Science, University of Turku, Itäinen Pitkäkatu 4 B, FI-20520 Turku, Finland.

In this study, the fabrication and properties of a synthetic keratoprosthesis skirt for use in osteo-odonto-keratoprosthesis (OOKP) surgery are discussed. In the search for a new material concept, bioactive glass and polymethyl methacrylate (PMMA)-based composites were prepared. Three different bioactive glasses (i.e. 45S5, S53P4 and 1-98) and one slowly resorbing glass, FL107, with two different forms (i.e. particles and porous glass structures) were employed in the fabrication of specimens. In in vitro studies, the dissolution behaviour in simulated aqueous humour, compressive properties, and pore formation of the composites were investigated. According to the results, FL107 dissolved very slowly (2.4% of the initial glass content in three weeks); thus, the pore formation of the FL107 composite was also observed to be restricted. The dissolution rates of the bioactive glass-PMMA composites were greater (12%-17%). These faster dissolving bioactive glass particles caused some porosity on the outermost surfaces of the composite. The slight surface porosity was also confirmed by a decrease in compressive properties. During six weeks' in vitro dissolution, the compressive strength of the test specimens containing particles decreased by 22% compared to values in dry conditions (90-107 MPa). These results indicate that the bioactive composites could be stable synthetic candidates for a keratoprosthesis skirt in the treatment of severely damaged or diseased cornea.
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http://dx.doi.org/10.1016/j.jmbbm.2011.05.025DOI Listing
November 2011