Publications by authors named "Pierre Weiss"

115 Publications

An Extrudable Partially Demineralized Allogeneic Bone Paste Exhibits a Similar Bone Healing Capacity as the "Gold Standard" Bone Graft.

Front Bioeng Biotechnol 2021 20;9:658853. Epub 2021 Apr 20.

INSERM, UMR 1229, RMeS, Regenerative Medicine and Skeleton, CHU Nantes, ONIRIS, Université de Nantes, Nantes, France.

Autologous bone grafts (BGs) remain the reference grafting technique in various clinical contexts of bone grafting procedures despite their numerous peri- and post-operative limitations. The use of allogeneic bone is a viable option for overcoming these limitations, as it is reliable and it has been widely utilized in various forms for decades. However, the lack of versatility of conventional allogeneic BGs (e.g., blocks, powders) limits their potential for use with irregular or hard-to-reach bone defects. In this context, a ready- and easy-to-use partially demineralized allogeneic BG in a paste form has been developed, with the aim of facilitating such bone grafting procedures. The regenerative properties of this bone paste (BP) was assessed and compared to that of a syngeneic BG in a pre-clinical model of intramembranous bone healing in critical size defects in rat calvaria. The microcomputed tridimensional quantifications and the histological observations at 7 weeks after the implantation revealed that the bone regeneration of critical-size defects (CSDs) filled with the BP was similar to syngeneic bone grafts (BGs). Thus, this ready-to-use, injectable, and moldable partially demineralized allogeneic BP, displaying equivalent bone healing capacity than the "gold standard," may be of particular clinical relevance in the context of oral and maxillofacial bone reconstructions.
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http://dx.doi.org/10.3389/fbioe.2021.658853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8098662PMC
April 2021

A partially demineralized allogeneic bone graft: in vitro osteogenic potential and preclinical evaluation in two different intramembranous bone healing models.

Sci Rep 2021 Mar 1;11(1):4907. Epub 2021 Mar 1.

INSERM, UMR 1229, RMeS, Regenerative Medicine and Skeleton, CHU Nantes, Université de Nantes, Oniris, 1 Place Alexis Ricordeau, 44042, Nantes, France.

In skeletal surgical procedures, bone regeneration in irregular and hard-to-reach areas may present clinical challenges. In order to overcome the limitations of traditional autologous bone grafts and bone substitutes, an extrudable and easy-to-handle innovative partially demineralized allogenic bone graft in the form of a paste has been developed. In this study, the regenerative potential of this paste was assessed and compared to its clinically used precursor form allogenic bone particles. Compared to the particular bone graft, the bone paste allowed better attachment of human mesenchymal stromal cells and their commitment towards the osteoblastic lineage, and it induced a pro-regenerative phenotype of human monocytes/macrophages. The bone paste also supported bone healing in vivo in a guide bone regeneration model and, more interestingly, exhibited a substantial bone-forming ability when implanted in a critical-size defect model in rat calvaria. Thus, these findings indicate that this novel partially demineralized allogeneic bone paste that combines substantial bone healing properties and rapid and ease-of-use may be a promising alternative to allogeneic bone grafts for bone regeneration in several clinical contexts of oral and maxillofacial bone grafting.
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http://dx.doi.org/10.1038/s41598-021-84039-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7921404PMC
March 2021

Silanization of Chitosan and Hydrogel Preparation for Skeletal Tissue Engineering.

Polymers (Basel) 2020 Nov 27;12(12). Epub 2020 Nov 27.

Dental Faculty, Université de Nantes, UMR 1229, RMeS, Regenerative Medicine and Skeleton, INSERM, ONIRIS, F-44042 Nantes, France.

Tissue engineering is a multidisciplinary field that relies on the development of customized biomaterial to support cell growth, differentiation and matrix production. Toward that goal, we designed the grafting of silane groups onto the chitosan backbone (Si-chito) for the preparation of in situ setting hydrogels in association with silanized hydroxypropyl methylcellulose (Si-HPMC). Once functionalized, the chitosan was characterized, and the presence of silane groups and its ability to gel were demonstrated by rheology that strongly suggests the presence of silane groups. Throughout physicochemical investigations, the Si-HPMC hydrogels containing Si-chito were found to be stiffer with an injection force unmodified. The presence of chitosan within the hydrogel has demonstrated a higher adhesion of the hydrogel onto the surface of tissues. The results of cell viability assays indicated that there was no cytotoxicity of Si-chito hydrogels in 2D and 3D culture of human SW1353 cells and human adipose stromal cells, respectively. Moreover, Si-chito allows the transplantation of human nasal chondrocytes in the subcutis of nude mice while maintaining their viability and extracellular matrix secretory activity. To conclude, Si-chito mixed with Si-HPMC is an injectable, self-setting and cytocompatible hydrogel able to support the in vitro and in vivo viability and activity of hASC.
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http://dx.doi.org/10.3390/polym12122823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7761294PMC
November 2020

In Situ Forming, Silanized Hyaluronic Acid Hydrogels with Fine Control Over Mechanical Properties and In Vivo Degradation for Tissue Engineering Applications.

Adv Healthc Mater 2020 10 31;9(19):e2000981. Epub 2020 Aug 31.

Université de Nantes, ONIRIS , INSERM, Regenerative Medicine and Skeleton, RMeS, UMR 1229, 1 Pl A Ricordeau, Nantes, F-44042, France.

In situ forming hydrogels that can be injected into tissues in a minimally-invasive fashion are appealing as delivery vehicles for tissue engineering applications. Ideally, these hydrogels should have mechanical properties matching those of the host tissue, and a rate of degradation adapted for neo-tissue formation. Here, the development of in situ forming hyaluronic acid hydrogels based on the pH-triggered condensation of silicon alkoxide precursors into siloxanes is reported. Upon solubilization and pH adjustment, the low-viscosity precursor solutions are easily injectable through fine-gauge needles prior to in situ gelation. Tunable mechanical properties (stiffness from 1 to 40 kPa) and associated tunable degradability (from 4 days to more than 3 weeks in vivo) are obtained by varying the degree of silanization (from 4.3% to 57.7%) and molecular weight (120 and 267 kDa) of the hyaluronic acid component. Following cell encapsulation, high cell viability (> 80%) is obtained for at least 7 days. Finally, the in vivo biocompatibility of silanized hyaluronic acid gels is verified in a subcutaneous mouse model and a relationship between the inflammatory response and the crosslink density is observed. Silanized hyaluronic acid hydrogels constitute a tunable hydrogel platform for material-assisted cell therapies and tissue engineering applications.
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http://dx.doi.org/10.1002/adhm.202000981DOI Listing
October 2020

Versatile lysine dendrigrafts and polyethylene glycol hydrogels with inherent biological properties: in vitro cell behavior modulation and in vivo biocompatibility.

J Biomed Mater Res A 2021 Jun 18;109(6):926-937. Epub 2020 Sep 18.

Laboratory of Tissue Biology and Therapeutic Engineering, IBCP, CNRS Université, Lyon, France.

Poly(ethylene glycol) (PEG) hydrogels have been extensively used as scaffolds for tissue engineering applications, owing to their biocompatibility, chemical versatility, and tunable mechanical properties. However, their bio-inert properties require them to be associated with additional functional moieties to interact with cells. To circumvent this need, we propose here to reticulate PEG molecules with poly(L-lysine) dendrigrafts (DGL) to provide intrinsic cell functionalities to PEG-based hydrogels. The physico-chemical characteristics of the resulting hydrogels were studied in regard of the concentration of each component. With increasing amounts of DGL, the cross-linking time and swelling ratio could be decreased, conversely to mechanical properties, which could be tailored from 7.7 ± 0.7 to 90 ± 28.8 kPa. Furthermore, fibroblasts adhesion, viability, and morphology on hydrogels were then assessed. While cell adhesion significantly increased with the concentration of DGL, cell viability was dependant of the ratio of DGL and PEG. Cell morphology and proliferation; however, appeared mainly related to the overall hydrogel rigidity. To allow cell infiltration and cell growth in 3D, the hydrogels were rendered porous. The biocompatibility of resulting hydrogels of different compositions and porosities was evaluated by 3 week subcutaneous implantations in mice. Hydrogels allowed an extensive cellular infiltration with a mild foreign body reaction, histological evidence of hydrogel degradation, and neovascularization.
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http://dx.doi.org/10.1002/jbm.a.37083DOI Listing
June 2021

Development of a Rat Model of Mandibular Irradiation Sequelae for Preclinical Studies of Bone Repair.

Tissue Eng Part C Methods 2020 08;26(8):447-455

Service d'ORL et de Chirurgie Cervico-Faciale, Centre Hospitalier Universitaire de Nantes, Nantes, France.

Repairing mandibular bone defects after radiotherapy of the upper aerodigestive tract is clinically challenging. Although bone tissue engineering has recently generated a number of innovative treatment approaches for osteoradionecrosis (ORN), these modalities must be evaluated preclinically in a relevant, reproducible, animal model. The objective of this study was to evaluate a novel rat model of mandibular irradiation sequelae, with a focus on the adverse effects of radiotherapy on bone structure, intraosseous vascularization, and bone regeneration. Rats were irradiated with a single 80 Gy dose to the jaws. Three weeks after irradiation, mandibular bone defects of different sizes (0, 1, 3, or 5 mm) were produced in each hemimandible. Five weeks after the surgical procedure, the animals were euthanized. Explanted mandibular samples were qualitatively and quantitatively assessed for bone formation, bone structure, and intraosseous vascular volume by using micro-computed tomography, scanning electron microscopy, and histology. Twenty irradiated hemimandibles and 20 nonirradiated hemimandibles were included in the study. The bone and vessel volumes were significantly lower in the irradiated group. The extent of bone remodeling was inversely related to the defect size. In the irradiated group, scanning electron microscopy revealed a large number of polycyclic gaps consistent with periosteocytic lysis (described as being pathognomonic for ORN). This feature was correlated with elevated osteoclastic activity in a histological assessment. In the irradiated areas, the critical-sized defect was 3 mm. Hence, our rat model of mandibular irradiation sequelae showed hypovascularization and osteopenia. Impact statement Repairing mandibular bone defects after radiotherapy of the upper aerodigestive tract is clinically challenging. Novel tissue engineering approaches for healing irradiated bone must first be assessed in animal models. The current rat model of mandibular irradiation sequelae is based on tooth extraction after radiotherapy. However, the mucosal sequelae of radiotherapy often prevent the retention of tissue-engineered biomaterials within the bone defect. We used a submandibular approach to create a new rat model of mandibular irradiation sequelae, which enables the stable retention of biomaterials within the bone defect and should thus facilitate the assessment of bone regeneration.
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http://dx.doi.org/10.1089/ten.TEC.2020.0109DOI Listing
August 2020

3D variable-density SPARKLING trajectories for high-resolution T2*-weighted magnetic resonance imaging.

NMR Biomed 2020 09 1;33(9):e4349. Epub 2020 Jul 1.

CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette cedex, 91191, France.

We have recently proposed a new optimization algorithm called SPARKLING (Spreading Projection Algorithm for Rapid K-space sampLING) to design efficient compressive sampling patterns for magnetic resonance imaging (MRI). This method has a few advantages over conventional non-Cartesian trajectories such as radial lines or spirals: i) it allows to sample the k-space along any arbitrary density while the other two are restricted to radial densities and ii) it optimizes the gradient waveforms for a given readout time. Here, we introduce an extension of the SPARKLING method for 3D imaging by considering both stacks-of-SPARKLING and fully 3D SPARKLING trajectories. Our method allowed to achieve an isotropic resolution of 600 μm in just 45 seconds for T2∗-weighted ex vivo brain imaging at 7 Tesla over a field-of-view of 200 × 200 × 140 mm . Preliminary in vivo human brain data shows that a stack-of-SPARKLING is less subject to off-resonance artifacts than a stack-of-spirals.
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http://dx.doi.org/10.1002/nbm.4349DOI Listing
September 2020

Quantifying Oxygen Levels in 3D Bioprinted Cell-Laden Thick Constructs with Perfusable Microchannel Networks.

Polymers (Basel) 2020 May 30;12(6). Epub 2020 May 30.

Regenerative Medicine and Cellular Therapies Group, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK.

The survival and function of thick tissue engineered implanted constructs depends on pre-existing, embedded, functional, vascular-like structures that are able to integrate with the host vasculature. Bioprinting was employed to build perfusable vascular-like networks within thick constructs. However, the improvement of oxygen transportation facilitated by these vascular-like networks was directly quantified. Using an optical fiber oxygen sensor, we measured the oxygen content at different positions within 3D bioprinted constructs with and without perfusable microchannel networks. Perfusion was found to play an essential role in maintaining relatively high oxygen content in cell-laden constructs and, consequently, high cell viability. The concentration of oxygen changes following switching on and off the perfusion. Oxygen concentration depletes quickly after pausing perfusion but recovers rapidly after resuming the perfusion. The quantification of oxygen levels within cell-laden hydrogel constructs could provide insight into channel network design and cellular responses.
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http://dx.doi.org/10.3390/polym12061260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7361700PMC
May 2020

Tailored Three-Dimensionally Printed Triply Periodic Calcium Phosphate Implants: A Preclinical Study for Craniofacial Bone Repair.

ACS Biomater Sci Eng 2020 01 22;6(1):553-563. Epub 2019 Nov 22.

INSERM, U 1229, Laboratoire Regenerative Medicine and Skeleton (RMeS), 1 place Alexis Ricordeau, Nantes F - 44042, France.

Finding alternative strategies for the regeneration of craniofacial bone defects (CSD), such as combining a synthetic ephemeral calcium phosphate (CaP) implant and/or active substances and cells, would contribute to solving this reconstructive roadblock. However, CaP's architectural features (i.e., architecture and composition) still need to be tailored, and the use of processed stem cells and synthetic active substances (e.g., recombinant human bone morphogenetic protein 2) drastically limits the clinical application of such approaches. Focusing on solutions that are directly transposable to the clinical setting, biphasic calcium phosphate (BCP) and carbonated hydroxyapatite (CHA) 3D-printed disks with a triply periodic minimal structure (TPMS) were implanted in calvarial critical-sized defects (rat model) with or without addition of total bone marrow (TBM). Bone regeneration within the defect was evaluated, and the outcomes were compared to a standard-care procedure based on BCP granules soaked with TBM (positive control). After 7 weeks, de novo bone formation was significantly greater in the CHA disks + TBM group than in the positive controls (3.33 mm and 2.15 mm, respectively, P=0.04). These encouraging results indicate that both CHA and TPMS architectures are potentially advantageous in the repair of CSDs and that this one-step procedure warrants further clinical investigation.
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http://dx.doi.org/10.1021/acsbiomaterials.9b01241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064275PMC
January 2020

A Self-Setting Hydrogel of Silylated Chitosan and Cellulose for the Repair of Osteochondral Defects: From Characterization to Preclinical Evaluation in Dogs.

Front Bioeng Biotechnol 2020 29;8:23. Epub 2020 Jan 29.

Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, France.

Articular cartilage (AC) may be affected by many injuries including traumatic lesions that predispose to osteoarthritis. Currently there is no efficient cure for cartilage lesions. In that respect, new strategies for regenerating AC are contemplated with interest. In this context, we aim to develop and characterize an injectable, self-hardening, mechanically reinforced hydrogel (Si-HPCH) composed of silanised hydroxypropymethyl cellulose (Si-HPMC) mixed with silanised chitosan. The cytocompatibility of Si-HPCH was tested using human adipose stromal cells (hASC). , we first mixed Si-HPCH with hASC to observe cell viability after implantation in nude mice subcutis. Si-HPCH associated or not with canine ASC (cASC), was then tested for the repair of osteochondral defects in canine femoral condyles. Our data demonstrated that Si-HPCH supports hASC viability in culture. Moreover, Si-HPCH allows the transplantation of hASC in the subcutis of nude mice while maintaining their viability and secretory activity. In the canine osteochondral defect model, while the empty defects were only partially filled with a fibrous tissue, defects filled with Si-HPCH with or without cASC, revealed a significant osteochondral regeneration. To conclude, Si-HPCH is an injectable, self-setting and cytocompatible hydrogel able to support the and viability and activity of hASC as well as the regeneration of osteochondral defects in dogs when implanted alone or with ASC.
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http://dx.doi.org/10.3389/fbioe.2020.00023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7025592PMC
January 2020

Preliminary evaluation of an osteochondral autograft, a prosthetic implant, and a biphasic absorbable implant for osteochondral reconstruction in a sheep model.

Vet Surg 2020 Apr 9;49(3):570-581. Epub 2020 Jan 9.

Department of Small Animal Surgery, Oniris Nantes-Atlantic College of Veterinary Medicine Food Science and Engineering, Nantes, France.

Objective: To determine the ability of three implants to enhance the healing of osteochondral defects: (1) a biphasic construct composed of calcium phosphate (CaP) and chitosan/cellulosic polymer, (2) a titanium-polyurethane implant, and (3) an osteochondral autograft.

Study Design: Experimental study.

Animals: Ten adult female sheep.

Methods: In five sheep, an 8-mm diameter osteochondral defect was created on the medial femoral condyle of a stifle and filled with a synthetic titanium-polyurethane implant. In five sheep, a similar defect was filled with an osteochondral autograft, and the donor site was filled with a biphasic construct combining CaP granules and a chitosan/cellulosic polymer. Sheep were monitored daily for lameness. Stifle radiographs and MRI were evaluated at 20 weeks, prior to animals being humanely killed. Surgical sites were evaluated with histology, microcomputed tomography, and scanning electron microscopy.

Results: Clinical outcomes were satisfactory regardless of the tested biomaterials. All implants appeared in place on imaging studies. Osteointegration of prosthetic implants varied between sites, with limited ingrowth of new bone into the titanium structure. Autografts and biphasic constructs were consistently well integrated in subchondral bone. All autografts except one contained a cartilage surface, and all biphasic constructs except one partially restored hyaline cartilage surface.

Conclusion: Biphasic constructs supported hyaline cartilage and subchondral bone regeneration, although restoration of the articular cartilage was incomplete.

Clinical Impact: Biphasic constructs may provide an alternative treatment for osteochondral defects, offering a less invasive approach compared with autologous grafts and eliminating the requirement for a prosthetic implant.
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http://dx.doi.org/10.1111/vsu.13373DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7154554PMC
April 2020

Reconstruction of segmental mandibular defects: Current procedures and perspectives.

Laryngoscope Investig Otolaryngol 2019 Dec 22;4(6):587-596. Epub 2019 Nov 22.

Laboratoire Regenerative Medicine and Skeleton RMeS, France INSERM, U 1229 Nantes France.

Background: The reconstruction of segmental mandibular defects remains a challenge for the reconstructive surgeon, from both a functional and an esthetic point of view.

Methods: This clinical review examines the different techniques currently in use for mandibular reconstruction as related to a range of etiologies, including the different bone donor sites, the alternatives to free flaps (FFs), as well as the contribution of computer-assisted surgery. Recent progress and the perspectives in bone tissue engineering (BTE) are also discussed.

Results: Osseous FF allows reliable and satisfying outcomes. However, locoregional flap, distraction osteogenesis, or even induced membrane techniques are other potential options in less favorable cases. Obtaining an engineered bone with satisfactory mechanical properties and sufficient vascular supply requires further investigations.

Conclusions: Osseous FF procedure remains the gold standard for segmental mandible reconstruction. BTE strategies offer promising alternatives.
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http://dx.doi.org/10.1002/lio2.325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6929581PMC
December 2019

Periodontal regenerative medicine using mesenchymal stem cells and biomaterials: A systematic review of pre-clinical studies.

Dent Mater J 2019 Dec 11;38(6):867-883. Epub 2019 Sep 11.

Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, University of Nantes.

The aim of the systematic review was to analyze the use of mesenchymal stem cells (MSC) and biomaterial for periodontal regeneration from preclinical animal models and human. Electronic databases were searched and additional hand-search in leading journals was performed. The research strategy was achieved according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The including criteria were as follows: MSC, biomaterial, in vivo studies, with histologic and radiologic analysis and written in English. The risk of bias was assessed for individual studies. A total of 50 articles were selected and investigated in the systematic review. These results indicate that MSC and scaffold provide beneficial effects on periodontal regeneration, with no adverse effects of such interventions. Future studies need to identify the suitable association of MSC and biomaterial and to characterize the type of new cementum and the organization of the periodontal ligament fiber regeneration.
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http://dx.doi.org/10.4012/dmj.2018-315DOI Listing
December 2019

Measure and characterization of the forces exerted by growing multicellular spheroids using microdevice arrays.

PLoS One 2019 23;14(5):e0217227. Epub 2019 May 23.

ITAV, Université de Toulouse, CNRS, UT3, Toulouse, France.

Growing multicellular spheroids recapitulate many features of expanding microtumours, and therefore they are an attractive system for biomechanical studies. Here, we report an original approach to measure and characterize the forces exerted by proliferating multicellular spheroids. As force sensors, we used high aspect ratio PDMS pillars arranged as a ring that supports a growing breast tumour cell spheroid. After optical imaging and determination of the force application zones, we combined 3D reconstruction of the shape of each deformed PDMS pillar with the finite element method to extract the forces responsible for the experimental observation. We found that the force exerted by growing spheroids ranges between 100nN and 300nN. Moreover, the exerted force was dependent on the pillar stiffness and increased over time with spheroid growth.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217227PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6532909PMC
January 2020

A Cellulose/Laponite Interpenetrated Polymer Network (IPN) Hydrogel: Controllable Double-Network Structure with High Modulus.

Polymers (Basel) 2018 Jun 8;10(6). Epub 2018 Jun 8.

Regenerative Medicine and Skeleton (RMeS), INSERM UMR_S1229, Université de Nantes, Centre Hospitalier Universitaire de Nantes, ONIRIS, F-44042 Nantes, France.

Laponite XLS™, which is a synthetic clay of nanometric dimensions containing a peptizing agent, has been associated with silanized hydroxypropylmethylcellulose (Si-HPMC) to form, after crosslinking, a novel composite hydrogel. Different protocols of sample preparation were used, leading to different morphologies. A key result was that the storage modulus of Si-HPMC/XLS composite hydrogel could be increased ten times when compared to that of pure Si-HPMC hydrogel using 2 wt % of Laponite. The viscoelastic properties of the composite formulations indicated that chemical and physical network structures co-existed in the Si-HPMC/XLS composite hydrogel. Images that were obtained from confocal laser scanning microscopy using labelled Laponite XLS in the composite hydrogels show two co-continuous areas: red light area and dark area. The tracking of fluorescent microspheres motions in the composite formulations revealed that the red-light area was a dense structure, whereas the dark area was rather loose without aggregated Laponite. This novel special double-network structure facilitates the composite hydrogel to be an adapted biomaterial for specific tissue engineering. Unfortunately, cytotoxicity's assays suggested that XLS Laponites are cytotoxic at low concentration. This study validates that the hybrid interpenetrated network IPN hydrogel has a high modulus that has adapted for tissue engineering, but the cell's internalization of Laponites has to be controlled.
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http://dx.doi.org/10.3390/polym10060634DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403786PMC
June 2018

FitEllipsoid: a fast supervised ellipsoid segmentation plugin.

BMC Bioinformatics 2019 Mar 15;20(1):142. Epub 2019 Mar 15.

ITAV, CNRS, Université de Toulouse, 1 Pl. Pierre Potier, Toulouse, 31106, France.

Background: The segmentation of a 3D image is a task that can hardly be automatized in certain situations, notably when the contrast is low and/or the distance between elements is small. The existing supervised methods require a high amount of user input, e.g. delineating the domain in all planar sections.

Results: We present FitEllipsoid, a supervised segmentation code that allows fitting ellipsoids to 3D images with a minimal amount of interactions: the user clicks on a few points on the boundary of the object on 3 orthogonal views. The quantitative geometric results of the segmentation of ellipsoids can be exported as a csv file or as a binary image. The core of the code is based on an original computational approach to fit ellipsoids to point clouds in an affine invariant manner. The plugin is validated by segmenting a large number of 3D nuclei in tumor spheroids, allowing to analyze the distribution of their shapes. User experiments show that large collections of nuclei can be segmented with a high accuracy much faster than with more traditional 2D slice by slice delineation approaches.

Conclusions: We designed a user-friendly software FitEllipsoid allowing to segment hundreds of ellipsoidal shapes in a supervised manner. It may be used directly to analyze biological samples, or to generate segmentation databases necessary to train learning algorithms. The algorithm is distributed as an open-source plugin to be used within the image analysis software Icy. We also provide a Matlab toolbox available with GitHub.
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http://dx.doi.org/10.1186/s12859-019-2673-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6419800PMC
March 2019

Synthesis of calcium-deficient hydroxyapatite nanowires and nanotubes performed by template-assisted electrodeposition.

Mater Sci Eng C Mater Biol Appl 2019 May 4;98:333-346. Epub 2019 Jan 4.

LISM, URCA, B.P. 1039, 51687 Reims Cedex 2, France; Université de Reims-Champagne Ardennes, UFR Odontologie, Reims 51100, France.

Hydroxyapatite (HA) has received much interest for being used as bone substitutes because of its similarity with bioapatites. In form of nanowires or nanotubes, HA would offer more advantages such as better biological and mechanical properties than conventional particles (spherical). To date, no study had allowed the isolated nanowires production with simultaneously well-controlled morphology and size, narrow size distribution and high aspect ratio (length on diameter ratio). So, it is impossible to determine exactly the real impact of particles' size and aspect ratio on healing responses of bone substitutes and characteristics of these ones; their biological and mechanical effects can never be reproducible. By the template-assisted pulsed electrodeposition method, we have for the first time succeeded to obtain such calcium-deficient hydroxyapatite (CDHA) particles in aqueous baths with hydrogen peroxide by both applying pulsed current density and pulsed potential in cathodic electrodeposition. After determining the best conditions for CDHA synthesis on gold substrate in thin films by X-ray diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDX), we have transferred those conditions to the nanowires and nanotubes synthesis with high aspect ratio going until 71 and 25 respectively. Polycrystalline CDHA nanowires and nanotubes were characterized by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). At the same time, this study enabled to understand the mechanism of nanopores filling in gold covered polycarbonate membrane: here a preferential nucleation on gold in membranes with 100 and 200 nm nanopores diameters forming nanowires whereas a preferential and randomly nucleation on nanopores walls in membranes with 400 nm nanopores diameter forming nanotubes.
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http://dx.doi.org/10.1016/j.msec.2018.12.071DOI Listing
May 2019

SPARKLING: variable-density k-space filling curves for accelerated T -weighted MRI.

Magn Reson Med 2019 06 17;81(6):3643-3661. Epub 2019 Feb 17.

NeuroSpin, CEA Saclay, Gif-sur-Yvette, France.

Purpose: To present a new optimition-driven design of optimal k-space trajectories in the context of compressed sensing: Spreading Projection Algorithm for Rapid K-space sampLING (SPARKLING).

Theory: The SPARKLING algorithm is a versatile method inspired from stippling techniques that automatically generates optimized sampling patterns compatible with MR hardware constraints on maximum gradient amplitude and slew rate. These non-Cartesian sampling curves are designed to comply with key criteria for optimal sampling: a controlled distribution of samples (e.g., variable density) and a locally uniform k-space coverage.

Methods: Ex vivo and in vivo prospective -weighted acquisitions were performed on a 7-Tesla scanner using the SPARKLING trajectories for various setups and target densities. Our method was compared to radial and variable-density spiral trajectories for high-resolution imaging.

Results: Combining sampling efficiency with compressed sensing, the proposed sampling patterns allowed up to 20-fold reductions in MR scan time (compared to fully sampled Cartesian acquisitions) for two-dimensional -weighted imaging without deterioration of image quality, as demonstrated by our experimental results at 7 Tesla on in vivo human brains for a high in-plane resolution of 390 μm. In comparison to existing non-Cartesian sampling strategies, the proposed technique also yielded superior image quality.

Conclusions: The proposed optimization-driven design of k-space trajectories is a versatile framework that is able to enhance MR sampling performance in the context of compressed sensing.
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http://dx.doi.org/10.1002/mrm.27678DOI Listing
June 2019

Heparan Sulfate Mimetics: A New Way to Optimize Therapeutic Effects of Hydrogel-Embedded Mesenchymal Stromal Cells in Colonic Radiation-Induced Damage.

Sci Rep 2019 01 17;9(1):164. Epub 2019 Jan 17.

IRSN, Institut de Radioprotection et de Sûreté Nucléaire, PSE-SANTE, SERAMED, LRMed, 31 avenue de la division Leclerc, 92262, Fontenay-aux-Roses, France.

Clinical expression of gastrointestinal radiation toxicity on non-cancerous tissue could be very life threatening and clinicians must deal increasingly with the management of late side effects of radiotherapy. Cell therapy, in particular mesenchymal stromal cell (MSC) therapy, has shown promising results in numerous preclinical animal studies and thus has emerged as a new hope for patient refractory to current treatments. However, many stem cell clinical trials do not confer any beneficial effect suggesting a real need to accelerate research towards the successful clinical application of stem cell therapy. In this study, we propose a new concept to improve the procedure of MSC-based treatment for greater efficacy and clinical translatability. We demonstrated that heparan sulfate mimetic (HS-m) injections that restore the extracellular matrix network and enhance the biological activity of growth factors, associated with local injection of MSC protected in a hydrogel, that increase cell engraftment and cell survival, improve the therapeutic benefit of MSC treatment in two animal models relevant of the human pathology. For the first time, a decrease of the injury score in the ulcerated area was observed with this combined treatment. We also demonstrated that the combined treatment favored the epithelial regenerative process. In this study, we identified a new way, clinically applicable, to optimize stem-cell therapy and could be proposed to patients suffering from severe colonic defect after radiotherapy.
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http://dx.doi.org/10.1038/s41598-018-36631-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6336771PMC
January 2019

PiT1/Slc20a1 Is Required for Endoplasmic Reticulum Homeostasis, Chondrocyte Survival, and Skeletal Development.

J Bone Miner Res 2019 02 20;34(2):387-398. Epub 2018 Nov 20.

INSERM, Unité mixte de Recherche (UMR) 1229, Regenerative Medicine and Skeleton (RMeS), Nantes-Atlantic National College of Veterinary Medicine, Food Science and Engineering, ONIRIS, Université de Nantes, Nantes, France.

During skeletal mineralization, the sodium-phosphate co-transporter PiT1Slc20a1 is assumed to meet the phosphate requirements of bone-forming cells, although evidence is missing. Here, we used a conditional gene deletion approach to determine the role of PiT1 in growth plate chondrocytes. We show that PiT1 ablation shortly after birth generates a rapid and massive cell death in the center of the growth plate, together with an uncompensated endoplasmic reticulum (ER) stress, characterized by morphological changes and increased Chop, Atf4, and Bip expression. PiT1 expression in chondrocytes was not found at the cell membrane but co-localized with the ER marker ERp46, and was upregulated by the unfolded protein response cascade. In addition, we identified the protein disulfide isomerase (Pdi) ER chaperone as a PiT1 binding partner and showed that PiT1 ablation impaired Pdi reductase activity. The ER stress induced by PiT1 deficiency in chondrocytes was associated with intracellular retention of aggrecan and vascular endothelial growth factor A (Vegf-A), which was rescued by overexpressing a phosphate transport-deficient mutant of PiT1. Our data thus reveal a novel, Pi-transport independent function of PiT1, as a critical modulator of ER homeostasis and chondrocyte survival during endochondral ossification. © 2018 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3609DOI Listing
February 2019

In situ photochemical crosslinking of hydrogel membrane for Guided Tissue Regeneration.

Dent Mater 2018 12 15;34(12):1769-1782. Epub 2018 Oct 15.

Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France; CHU Nantes, PHU4 OTONN, Nantes, F-44093, France. Electronic address:

Objective: Periodontitis is an inflammatory disease that destroys the tooth-supporting attachment apparatus. Guided tissue regeneration (GTR) is a technique based on a barrier membrane designed to prevent wound space colonization by gingival cells. This study examined a new formulation composed of two polymers that could be photochemically cross-linked in situ into an interpenetrated polymer network (IPN) forming a hydrogel membrane.

Methods: We synthetized and characterized silanized hydroxypropyl methylcellulose (Si-HPMC) for its cell barrier properties and methacrylated carboxymethyl chitosan (MA-CMCS) for its degradable backbone to use in IPN. Hydrogel membranes were cross-linked using riboflavin photoinitiator and a dentistry visible light lamp. The biomaterial's physicochemical and mechanical properties were determined. Hydrogel membrane degradation was evaluated in lysozyme. Cytocompatibility was estimated by neutral red uptake. The cell barrier property was studied culturing human primary gingival fibroblasts or human gingival explants on membrane and analyzed with confocal microscopy and histological staining.

Results: The IPN hydrogel membrane was obtained after 120s of irradiation. The IPN showed a synergistic increase in Young moduli compared with the single networks. The CMCS addition in IPN allows a progressive weight loss compared to each polymer network. Cytocompatibility was confirmed by neutral red assay. Human cell invasion was prevented by hydrogel membranes and histological sections revealed that the biomaterial exhibited a barrier effect in contact with soft gingival tissue.

Significance: We demonstrated the ability of an innovative polymer formulation to form in situ, using a dentist's lamp, an IPN hydrogel membrane, which could be an easy-to-use biomaterial for GTR therapy.
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http://dx.doi.org/10.1016/j.dental.2018.09.017DOI Listing
December 2018

An empirical study of the maximum degree of undersampling in compressed sensing for T-weighted MRI.

Magn Reson Imaging 2018 11 21;53:112-122. Epub 2018 Jul 21.

NeuroSpin, CEA Saclay, Gif-sur-Yvette cedex 91191, France; Université Paris-Saclay, France; Parietal, INRIA, Palaiseau 91120, France. Electronic address:

Magnetic Resonance Imaging (MRI) is one of the most dynamic and safe imaging modalities used in clinical routine today. Yet, one major limitation to this technique resides in its long acquisition times. Over the last decade, Compressed Sensing (CS) has been increasingly used to address this issue and offers to shorten MR scans by reconstructing images from undersampled Fourier data. Nevertheless, a quantitative guide on the degree of acceleration applicable to a given acquisition scenario is still lacking today, leading in practice to a trial-and-error approach in the selection of the appropriate undersampling factor. In this study, we shortly point out the existing theoretical sampling results in CS and their limitations which motivate the focus of this work: an empirical and quantitative analysis of the maximum degree of undersampling allowed by CS in the specific context of T-weighted MRI. We make use of a generic method based on retrospective undersampling to quantitatively deduce the maximum acceleration factor R which preserves a desired image quality as a function of the image resolution and the available signal-to-noise ratio (SNR). Our results quantify how larger acceleration factors can be applied to higher resolution images as long as a minimum SNR is guaranteed. In practice however, the maximum acceleration factor for a given resolution appears to be constrained by the available SNR inherent to the considered acquisition. Our analysis enables to take this a priori knowledge into account, allowing to derive a sequence-specific maximum acceleration factor adapted to the intrinsic SNR of any MR pipeline. These results obtained on an analytical T-weighted phantom image were corroborated by prospective experiments performed on MR data collected with radial trajectories on a 7 T scanner with the same contrast. The proposed framework allows to study other sequence weightings and therefore better optimize sequences when accelerated using CS.
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http://dx.doi.org/10.1016/j.mri.2018.07.006DOI Listing
November 2018

Application of Millifluidics to Encapsulate and Support Viable Human Mesenchymal Stem Cells in a Polysaccharide Hydrogel.

Int J Mol Sci 2018 Jul 3;19(7). Epub 2018 Jul 3.

Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, F-44042 Nantes, France.

Human adipose-derived stromal cells (hASCs) are widely known for their immunomodulatory and anti-inflammatory properties. This study proposes a method to protect cells during and after their injection by encapsulation in a hydrogel using a droplet millifluidics technique. A biocompatible, self-hardening biomaterial composed of silanized-hydroxypropylmethylcellulose (Si-HPMC) hydrogel was used and dispersed in an oil continuous phase. Spherical particles with a mean diameter of 200 μm could be obtained in a reproducible manner. The viability of the encapsulated hASCs in the Si-HPMC particles was 70% after 14 days in vitro, confirming that the Si-HPMC particles supported the diffusion of nutrients, vitamins, and glucose essential for survival of the encapsulated hASCs. The combination of droplet millifluidics and biomaterials is therefore a very promising method for the development of new cellular microenvironments, with the potential for applications in biomedical engineering.
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http://dx.doi.org/10.3390/ijms19071952DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073862PMC
July 2018

Evaluation of a hydrogel membrane on bone regeneration in furcation periodontal defects in dogs.

Dent Mater J 2018 Sep 20;37(5):825-834. Epub 2018 Jun 20.

INSERM, UMR-S 1229, RMeS, Faculty of Dental Surgery, University of Nantes.

The aim of the study was to evaluate bone regeneration using a canine model with surgically created periodontal defects filled for 12 weeks using a stratified biomaterial consisting in a biphasic calcium phosphate (BCP) covered with a crosslinking hydrogel acting as polymer membrane of silated hydroxypropyl methylcellulose (Si-HPMC) as the tested new concept. Bilateral, critical-sized, defects were surgically created at the mandibular premolar teeth of six adult beagle dogs. The defects were randomly allocated and: (i) left empty for spontaneous healing or filled with: (ii) BCP and a collagen membrane; (iii) BCP and hydrogel Si-HPMC membrane. At 12 weeks, the experimental conditions resulted in significantly enhanced bone regeneration in the test BCP/Si-HPMC group. Within the limits of this study, we suggest that the hydrogel Si-HPMC may act as an occlusive barrier to protect bone area from soft connective tissue invasion and then effectively contribute to enhance bone regeneration.
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http://dx.doi.org/10.4012/dmj.2017-238DOI Listing
September 2018

Impact of physical confinement on nuclei geometry and cell division dynamics in 3D spheroids.

Sci Rep 2018 06 8;8(1):8785. Epub 2018 Jun 8.

ITAV, Université de Toulouse, CNRS, Toulouse, France.

Multicellular tumour spheroids are used as a culture model to reproduce the 3D architecture, proliferation gradient and cell interactions of a tumour micro-domain. However, their 3D characterization at the cell scale remains challenging due to size and cell density issues. In this study, we developed a methodology based on 3D light sheet fluorescence microscopy (LSFM) image analysis and convex hull calculation that allows characterizing the 3D shape and orientation of cell nuclei relative to the spheroid surface. By using this technique and optically cleared spheroids, we found that in freely growing spheroids, nuclei display an elongated shape and are preferentially oriented parallel to the spheroid surface. This geometry is lost when spheroids are grown in conditions of physical confinement. Live 3D LSFM analysis of cell division revealed that confined growth also altered the preferential cell division axis orientation parallel to the spheroid surface and induced prometaphase delay. These results provide key information and parameters that help understanding the impact of physical confinement on cell proliferation within tumour micro-domains.
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http://dx.doi.org/10.1038/s41598-018-27060-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5993719PMC
June 2018

Polysaccharide Hydrogels Support the Long-Term Viability of Encapsulated Human Mesenchymal Stem Cells and Their Ability to Secrete Immunomodulatory Factors.

Stem Cells Int 2017 11;2017:9303598. Epub 2017 Oct 11.

INSERM, UMR 1229, Regenerative Medicine and Skeleton (RMeS), Université de Nantes, ONIRIS, 44042 Nantes, France.

While therapeutically interesting, the injection of MSCs suffers major limitations including cell death upon injection and a massive leakage outside the injection site. We proposed to entrap MSCs within spherical particles derived from alginate, as a control, or from silanized hydroxypropyl methylcellulose (Si-HPMC). We developed water in an oil dispersion method to produce small Si-HPMC particles with an average size of about 68 m. We evidenced a faster diffusion of fluorescein isothiocyanate-dextran in Si-HPMC particles than in alginate ones. Human adipose-derived MSCs (hASC) were encapsulated either in alginate or in Si-HPMC, and the cellularized particles were cultured for up to 1 month. Both alginate and Si-HPMC particles supported cell survival, and the average number of encapsulated hASC per alginate and Si-HPMC particle (7102 and 5100, resp.) did not significantly change. The stimulation of encapsulated hASC with proinflammatory cytokines resulted in the production of IDO, PGE, and HGF whose concentration was always higher when cells were encapsulated in Si-HPMC particles than in alginate ones. We have demonstrated that Si-HPMC and alginate particles support hASC viability and the maintenance of their ability to secrete therapeutic factors.
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http://dx.doi.org/10.1155/2017/9303598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5660815PMC
October 2017

Laponite nanoparticle-associated silated hydroxypropylmethyl cellulose as an injectable reinforced interpenetrating network hydrogel for cartilage tissue engineering.

Acta Biomater 2018 Jan 8;65:112-122. Epub 2017 Nov 8.

Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes F-44042, France; Université de Nantes, UFR Odontologie, Nantes F-44042, France; CHU Nantes, PHU4 OTONN, Nantes F-44042, France.

Articular cartilage is a connective tissue which does not spontaneously heal. To address this issue, biomaterial-assisted cell therapy has been researched with promising advances. The lack of strong mechanical properties is still a concern despite significant progress in three-dimensional scaffolds. This article's objective was to develop a composite hydrogel using a small amount of nano-reinforcement clay known as laponites. These laponites were capable of self-setting within the gel structure of the silated hydroxypropylmethyl cellulose (Si-HPMC) hydrogel. Laponites (XLG) were mixed with Si-HPMC to prepare composite hydrogels leading to the development of a hybrid interpenetrating network. This interpenetrating network increases the mechanical properties of the hydrogel. The in vitro investigations showed no side effects from the XLG regarding cytocompatibility or oxygen diffusion within the composite after cross-linking. The ability of the hybrid scaffold containing the composite hydrogel and chondrogenic cells to form a cartilaginous tissue in vivo was investigated during a 6-week implantation in subcutaneous pockets of nude mice. Histological analysis of the composite constructs revealed the formation of a cartilage-like tissue with an extracellular matrix containing glycosaminoglycans and collagens. Overall, this new hybrid construct demonstrates an interpenetrating network which enhances the hydrogel mechanical properties without interfering with its cytocompatibility, oxygen diffusion, or the ability of chondrogenic cells to self-organize in the cluster and produce extracellular matrix components. This composite hydrogel may be of relevance for the treatment of cartilage defects in a large animal model of articular cartilage defects.

Statement Of Significance: Articular cartilage is a tissue that fails to heal spontaneously. To address this clinically relevant issue, biomaterial-assisted cell therapy is considered promising but often lacks adequate mechanical properties. Our objective was to develop a composite hydrogel using a small amount of nano reinforcement (laponite) capable of gelling within polysaccharide based self-crosslinking hydrogel. This new hybrid construct demonstrates an interpenetrating network (IPN) which enhances the hydrogel mechanical properties without interfering with its cytocompatibility, O diffusion and the ability of chondrogenic cells to self-organize in cluster and produce extracellular matrix components. This composite hydrogel may be of relevance for the treatment of cartilage defects and will now be considered in a large animal model of articular cartilage defects.
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http://dx.doi.org/10.1016/j.actbio.2017.11.027DOI Listing
January 2018

Adhesion, proliferation and osteogenic differentiation of human MSCs cultured under perfusion with a marine oxygen carrier on an allogenic bone substitute.

Artif Cells Nanomed Biotechnol 2018 Feb 22;46(1):95-107. Epub 2017 Aug 22.

a Functional Genetics Department, INSERM Research Unit 1078 , University of Western Brittany, European Brittany University , Brest , France.

Tissue engineering strategies have been developed to optimize osseointegration in dental implant surgery. One of the major problems is the non-homogeneous spatial cell distribution in the scaffold, as well as subsequent matrix production. Insufficient nutrient and oxygen supplies inside the scaffold are factors in this phenomenon. To mediate this gradient formation, we have implemented a perfusion culture method to seed human bone marrow mesenchymal stem cells (MSCs) into three-dimensional (3-D)-allogenic bone scaffolds in combination with a marine haemoglobin, HEMOXCell, for oxygen delivery. Cell culture was performed under static and perfusion conditions, with standard and osteogenic media, with and without HEMOXCell. The cell seeding efficiency, as well as MSC/scaffold cytocompatibly were assessed using viability and proliferation assays. Scaffolds' cellularization and extracellular matrix (ECM) formation were analyzed using scanning electron microscopy and histological staining. Cell differentiation was investigated with osteogenic biomarkers gene expression analysis. The perfusion culture was observed to significantly promote MSC proliferation and differentiation throughout the scaffolds, especially when using the induction medium w/HEMOXCell. Our data suggest that perfusion culture of MSC into allogenic bone substitute with HEMOXCell as a natural oxygen carrier is promising for tissue engineering applications to oxygenate hypoxic areas and to promote cellular proliferation.
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http://dx.doi.org/10.1080/21691401.2017.1365724DOI Listing
February 2018