Publications by authors named "Min Ho Kang"

98 Publications

Graphene Oxide-Supported Microwell Grids for Preparing Cryo-EM Samples with Controlled Ice Thickness.

Adv Mater 2021 Sep 12:e2102991. Epub 2021 Sep 12.

School of Chemical and Biological Engineering, and Institute of Chemical Processes (ICP), Seoul National University, Seoul, 08826, Republic of Korea.

Cryogenic-electron microscopy (cryo-EM) is the preferred method to determine 3D structures of proteins and to study diverse material systems that intrinsically have radiation or air sensitivity. Current cryo-EM sample preparation methods provide limited control over the sample quality, which limits the efficiency and high throughput of 3D structure analysis. This is partly because it is difficult to control the thickness of the vitreous ice that embeds specimens, in the range of nanoscale, depending on the size and type of materials of interest. Thus, there is a need for fine regulation of the thickness of vitreous ice to deliver consistent high signal-to-noise ratios for low-contrast biological specimens. Herein, an advanced silicon-chip-based device is developed which has a regular array of micropatterned holes with a graphene oxide (GO) window on freestanding silicon nitride (Si N ). Accurately regulated depths of micropatterned holes enable precise control of vitreous ice thickness. Furthermore, GO window with affinity for biomolecules can facilitate concentration of the sample molecules at a higher level. Incorporation of micropatterned chips with a GO window enhances cryo-EM imaging for various nanoscale biological samples including human immunodeficiency viral particles, groEL tetradecamers, apoferritin octahedral, aldolase homotetramer complexes, and tau filaments, as well as inorganic materials.
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http://dx.doi.org/10.1002/adma.202102991DOI Listing
September 2021

Silicon Oxide Etching Process of NF and FNO Plasmas with a Residual Gas Analyzer.

Materials (Basel) 2021 Jun 2;14(11). Epub 2021 Jun 2.

Department of Electrical and Biological Physics, Kwangwoon University, 20 Kwangwoon-ro, Nowon-gu, Seoul 01897, Korea.

The use of NF is significantly increasing every year. However, NF is a greenhouse gas with a very high global warming potential. Therefore, the development of a material to replace NF is required. FNO is considered a potential replacement to NF. In this study, the characteristics and cleaning performance of the FNO plasma to replace the greenhouse gas NF were examined. Etching of SiO thin films was performed, the DC offset of the plasma of both gases (i.e., NF and FNO) was analyzed, and a residual gas analysis was performed. Based on the analysis results, the characteristics of the FNO plasma were studied, and the SiO etch rates of the NF and FNO plasmas were compared. The results show that the etch rates of the two gases have a difference of 95% on average, and therefore, the cleaning performance of the FNO plasma was demonstrated, and the potential benefit of replacing NF with FNO was confirmed.
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http://dx.doi.org/10.3390/ma14113026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199652PMC
June 2021

Reversing the Irreversible: Thermodynamic Stabilization of LiAlH Nanoconfined Within a Nitrogen-Doped Carbon Host.

ACS Nano 2021 Jun 24;15(6):10163-10174. Epub 2021 May 24.

Sandia National Laboratories, 7011 East Avenue, Livermore, California 94550, United States.

A general problem when designing functional nanomaterials for energy storage is the lack of control over the stability and reactivity of metastable phases. Using the high-capacity hydrogen storage candidate LiAlH as an exemplar, we demonstrate an alternative approach to the thermodynamic stabilization of metastable metal hydrides by coordination to nitrogen binding sites within the nanopores of N-doped CMK-3 carbon (NCMK-3). The resulting [email protected] material releases H at temperatures as low as 126 °C with full decomposition below 240 °C, bypassing the usual LiAlH intermediate observed in bulk. Moreover, >80% of LiAlH can be regenerated under 100 MPa H, a feat previously thought to be impossible. Nitrogen sites are critical to these improvements, as no reversibility is observed with undoped CMK-3. Density functional theory predicts a drastically reduced Al-H bond dissociation energy and supports the observed change in the reaction pathway. The calculations also provide a rationale for the solid-state reversibility, which derives from the combined effects of nanoconfinement, Li adatom formation, and charge redistribution between the metal hydride and the host.
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http://dx.doi.org/10.1021/acsnano.1c02079DOI Listing
June 2021

Structuring Pickering Emulsion Interfaces with Bilayered Coacervates of Cellulose Nanofibers and Hectorite Nanoplatelets.

Langmuir 2021 04 29;37(13):3828-3835. Epub 2021 Mar 29.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea.

In this study, we present a water-in-silicone oil (W/S) Pickering emulsion system stabilized via in situ interfacial coacervation of attractive hectorite nanoplatelets (AHNPs) and bacterial cellulose nanofibrils (BCNFs). A bilayered coacervate is generated at the W/S interface by employing the controlled electrostatic interaction between the positively charged AHNPs and the negatively charged BCNFs. The W/S interface with the bilayered coacervate shows a significant increase in the interfacial modulus by 2 orders of magnitude than that with the AHNPs only. In addition, we observe that water droplets are interconnected by the BCNF bridging across the continuous phase of silicon, which is attributed to the diffusive transport phenomenon. This droplet interconnection results in the effective prevention of drop coalescence, which is confirmed via emulsion sedimentation kinetics. These results indicate that our bilayered coacervation technology has the potential of developing a promising Pickering emulsion platform that can be used in the pharmaceutical and cosmetic industries.
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http://dx.doi.org/10.1021/acs.langmuir.0c03082DOI Listing
April 2021

Reversible disorder-order transitions in atomic crystal nucleation.

Science 2021 01;371(6528):498-503

Department of Mechanical Engineering, BK21 FOUR ERICA-ACE Center, Hanyang University, Ansan, Gyeonggi 15588, Republic of Korea.

Nucleation in atomic crystallization remains poorly understood, despite advances in classical nucleation theory. The nucleation process has been described to involve a nonclassical mechanism that includes a spontaneous transition from disordered to crystalline states, but a detailed understanding of dynamics requires further investigation. In situ electron microscopy of heterogeneous nucleation of individual gold nanocrystals with millisecond temporal resolution shows that the early stage of atomic crystallization proceeds through dynamic structural fluctuations between disordered and crystalline states, rather than through a single irreversible transition. Our experimental and theoretical analyses support the idea that structural fluctuations originate from size-dependent thermodynamic stability of the two states in atomic clusters. These findings, based on dynamics in a real atomic system, reshape and improve our understanding of nucleation mechanisms in atomic crystallization.
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http://dx.doi.org/10.1126/science.aaz7555DOI Listing
January 2021

Effect of Hemodialysis on Peripapillary Choroidal Thickness Measured by Swept-Source Optical Coherence Tomography.

J Glaucoma 2021 06;30(6):459-464

Department of Ophthalmology.

Purpose: The aim was to investigate the effects of hemodialysis (HD) on peripapillary choroidal thickness (PCT) by swept-source optical coherence tomography and on other ophthalmologic parameters in patients with end-stage kidney disease.

Materials And Methods: This was a prospective observational study. The authors evaluated 29 patients who underwent HD for end-stage kidney disease. Detailed ophthalmologic examinations and swept-source optical coherence tomography were performed immediately before and after HD. PCT was measured using the modification tool in the built-in OCT image viewer program. Changes in PCT before and after HD were statistically analyzed.

Results: The average PCT significantly decreased from 127.3±49.2 μm before HD to 117.1±50.9 μm after HD (P<0.001). A significant correlation was found between changes in PCT and macular choroidal thickness (ρ=0.547, P=0.002). Changes in mean ocular perfusion pressure did not significantly correlate with changes in PCT (ρ=-0.049, P=0.803).

Conclusions: PCT significantly decreased after HD. HD could influence the optic nerve head and its surrounding structures.
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http://dx.doi.org/10.1097/IJG.0000000000001762DOI Listing
June 2021

Corneal Endothelial Cell Loss after Phacoemulsification in Eyes with a Prior Acute Angle-closure Attack.

Korean J Ophthalmol 2020 12 3;34(6):432-438. Epub 2020 Dec 3.

Department of Ophthalmology, Hanyang University Guri Hospital, Guri, Korea.

Purpose: To evaluate endothelial damage after cataract surgery in eyes affected by an angle-closure attack (ACA) and compare it to that in the unaffected fellow eyes (FEs) of patients with ACA and normal eyes (NEs).

Methods: The medical data of eyes affected by ACA, FEs (with no history of acute glaucoma attack), and NEs of patients who underwent cataract surgery with simultaneous intraocular lens implantation were retrospectively reviewed. Endothelial cell density (ECD) and central corneal thickness (CCT) measured before surgery and at 1 week, 1 month, and 3 months after surgery were analyzed, and the percentages of loss in ECD and increase in CCT of the three groups were compared.

Results: The study enrolled 140 eyes from 100 patients (50 eyes in the ACA group, 40 eyes in the FE group, and 50 eyes in the NE group). The mean ECD was significantly lower in the ACA group than in the other groups (p < 0.001). However, the percentage of ECD reduction was not significantly greater in the ACA group than in the other groups (p > 0.05). None of the eyes developed corneal edema at 3 months postoperatively. Moreover, the CCTs of the three groups were similar throughout the follow-up period (p > 0.05).

Conclusions: Phacoemulsification was not associated with greater endothelial cell loss in the ACA group than in the NE and FE groups. This finding shows that ACA history may not contribute to the exacerbation of corneal endothelial damage in cataract surgery.
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http://dx.doi.org/10.3341/kjo.2020.0040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7738218PMC
December 2020

Construction of tantalum/poly(ether imide) coatings on magnesium implants with both corrosion protection and osseointegration properties.

Bioact Mater 2021 Apr 28;6(4):1189-1200. Epub 2020 Oct 28.

Department of Materials Science and Engineering, Chosun University, Gwangju, Republic of Korea.

Poly(ether imide) (PEI) has shown satisfactory corrosion protection capability with good adhesion strength as a coating for magnesium (Mg), a potential candidate of biodegradable orthopedic implant material. However, its innate hydrophobic property causes insufficient osteoblast affinity and a lack of osseointegration. Herein, we modify the physical and chemical properties of a PEI-coated Mg implant. A plasma immersion ion implantation technique is combined with direct current (DC) magnetron sputtering to introduce biologically compatible tantalum (Ta) onto the surface of the PEI coating. The PEI-coating layer is not damaged during this process owing to the extremely short processing time (30 s), retaining its high corrosion protection property and adhesion stability. The Ta-implanted layer (roughly 10-nm-thick) on the topmost PEI surface generates long-term surface hydrophilicity and favorable surface conditions for pre-osteoblasts to adhere, proliferate, and differentiate. Furthermore, in a rabbit femur study, the Ta/PEI-coated Mg implant demonstrates significantly enhanced bone tissue affinity and osseointegration capability. These results indicate that Ta/PEI-coated Mg is promising for achieving early mechanical fixation and long-term success in biodegradable orthopedic implant applications.
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http://dx.doi.org/10.1016/j.bioactmat.2020.10.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595939PMC
April 2021

Enhanced Bioactivity of Micropatterned Hydroxyapatite Embedded Poly(L-lactic) Acid for a Load-Bearing Implant.

Polymers (Basel) 2020 Oct 17;12(10). Epub 2020 Oct 17.

Department of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Korea.

Poly(L-lactic) acid (PLLA) is among the most promising polymers for bone fixation, repair, and tissue engineering due to its biodegradability and relatively good mechanical strength. Despite these beneficial characteristics, its poor bioactivity often requires incorporation of bioactive ceramic materials. A bioresorbable composite made of PLLA and hydroxyapatite (HA) may improve biocompatibility but typically causes deterioration in mechanical properties, and bioactive coatings inevitably carry a risk of coating delamination. Therefore, in this study, we embedded micropatterned HA on the surface of PLLA to improve bioactivity while eliminating the risk of HA delamination. An HA pattern was successfully embedded in a PLLA matrix without degeneration of the matrix's mechanical properties, thanks to a transfer technique involving conversion of Mg to HA. Furthermore, patterned HA/PLLA's biological response outperformed that of pure PLLA. These results confirm patterned HA/PLLA as a candidate for wide acceptance in biodegradable load-bearing implant applications.
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http://dx.doi.org/10.3390/polym12102390DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7603062PMC
October 2020

Wafer-scale carbon nanotube network transistors.

Nanotechnology 2020 Nov;31(46):465303

School of Electrical Engineering, Kookmin University, Seoul 02707, Korea.

Highly purified, preseparated semiconducting carbon nanotubes (CNTs) hold great potential for high-performance CNT network transistors due to their high electrical conductivity, high mechanical strength, and room-temperature processing compatibility. In this paper, we report our recent progress on CNT network transistors integrated on an 8-inch wafer. We observe that the key device performance parameters of CNT network transistors at various locations on an 8-inch wafer are highly uniform and that the device yield is impressive. Therefore, this work validates a promising path toward mass production and will make a significant contribution to the future field of wafer-scale CNT electronics.
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http://dx.doi.org/10.1088/1361-6528/abac31DOI Listing
November 2020

Directly drawn top-gate semiconducting carbon nanotube thin-film transistors and complementary inverters.

Nanotechnology 2020 Aug 22;31(32):32LT01. Epub 2020 Apr 22.

School of Electrical Engineering, Kookmin University, Seoul 02707, Republic of Korea.

As the emerging demand for electronic devices that are simple, cost effective and capable of rapid fabrication has increased, novel fabrication techniques for designing and manufacturing such devices have attracted remarkable research interest. One method for prototyping these electronic devices is to draw them using a handwriting tool that is commonly available. In this work, we demonstrate a transistor and complementary logic inverter that are directly drawn using a brush and that are based on solution-based materials such as semiconducting carbon nanotubes (CNTs), silver ink and paste, and cross-linked poly(4-vinylphenol) (cPVP). The directly drawn CNT thin-film transistor (TFT) has p-type behavior due to the adsorption of oxygen and moisture, a high current on/off ratio (approximately 10), and a low operating voltage. By employing a solution-based chemical doping treatment with an amine-rich polymer, polyethyleneimine (PEI), that has strong electron-donating ability, the drawn p-type CNT-TFT is successfully converted to an n-type CNT-TFT. Therefore, we fabricate a drawn complementary logic inverter consisting of the p-type CNT-TFT and PEI-treated n-type CNT-TFT and evaluate its electrical performance.
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http://dx.doi.org/10.1088/1361-6528/ab8c06DOI Listing
August 2020

Changes in the Retinal Microvasculature Measured Using Optical Coherence Tomography Angiography According to Age.

J Clin Med 2020 Mar 24;9(3). Epub 2020 Mar 24.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul 04763, Korea.

In this cross-sectional study, we examined age-related changes in the retinal vessels of 100 healthy participants, aged from 5 to 80 years, and divided into four groups (G1, under 20 years of age; G2, from 20 to 39 years of age; G3, from 40 to 59 years of age; G4, age 60 years or older). All subjects underwent swept-source optical coherence tomography (SS-OCT) and OCT angiography (OCTA). The vascular density (VD) of the superficial (SCP) and deep capillary plexus (DCP), and choriocapillaris (CCP) were measured using OCTA. The vascular density of each capillary layer, foveal avascular zone (FAZ) area, ganglion cell-inner plexiform layer (GC-IPL) thickness, retinal thickness (RT), and choroidal thickness (CT) were compared between age groups. Most OCT variables were correlated with OCTA variables. The FAZ area; VD of the SCP, DCP, and CCP; GC-IPL thickness; RT; and CT showed significant difference ( < 0.001) between G1 + G2 and G3 + G4, except for central GC-IPL thickness ( = 0.14) and central RT ( = 0.25). Density of the retinal capillary vasculature reduced and FAZ area increased after age 40, which represents the onset of middle age.
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http://dx.doi.org/10.3390/jcm9030883DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7141499PMC
March 2020

Increasing incidence of macular edema in excessive morning blood pressure surge in patients with retinal vein occlusion.

Sci Rep 2020 03 10;10(1):4420. Epub 2020 Mar 10.

Division of Cardiology, Department of Internal Medicine, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Republic of Korea.

Morning blood pressure surge (MBPS) had been known to be associated with hypertensive target organ injury and vascular events. Retinal vein occlusion (RVO) is also known to be related with underlying cardiovascular risk factors. This study investigated the effect of MBPS on patients with RVO. In total, 76 patients with RVO who had undergone systemic cardiovascular examination including a 24-hour ambulatory blood pressure monitoring, carotid artery intima media thickness, and pulse wave velocity were evaluated between January 2015 and February 2019. The MBPS was calculated as follows: mean systolic blood pressure measured over two hours after awakening minus mean systolic blood pressure measured during the one hour that included the lowest sleep blood pressure. Macular edema was significantly more prevalent in the MBPS group compared with the non-MBPS group. After adjusting for confounding factors, multivariate regression analyses revealed that MBPS independently predicted macular edema in patients with RVO [Odds ratio 4.75, 95% confidence interval 1.136-16.6, p = 0.015]. In conclusion, evaluating blood pressure patterns, especially MBPS, using 24-hour ambulatory blood pressure monitoring may be useful for assessing and predicting ophthalmologic outcome and may facilitate better blood pressure control in patients with RVO.
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http://dx.doi.org/10.1038/s41598-020-61386-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064582PMC
March 2020

Changes in Retinal Vessel and Retinal Layer Thickness After Vitrectomy in Retinal Detachment via Swept-Source OCT Angiography.

Invest Ophthalmol Vis Sci 2020 02;61(2):35

,.

Purpose: To compare postvitrectomy retinal and choroidal vessel density (VD) and retinal layer thickness between eyes with macula-off and macula-on rhegmatogenous retinal detachment (RRD) using swept-source optical coherence tomography (SS-OCT) and optical coherence tomography angiography (OCTA) and to identify OCTA factors associated with visual outcomes.

Methods: We retrospectively reviewed 31 eyes that underwent pars plana vitrectomy for primary RRD. Eyes with macula-off and macula-on RRD were compared with healthy fellow eyes. Both OCT and OCTA were performed 6 months after surgery, and the macula-off RRD group was divided into two subgroups according to the presence of an outer retinal defect. The correlations between postoperative best-corrected visual acuity (BCVA) at 6 months and SS-OCT and OCTA measurements were analyzed.

Results: Twenty eyes with macula-off RRD and 11 eyes with macula-on RRD were included. In the macula-off RRD group, the central retinal thickness was significantly decreased 6 months postoperatively compared with the fellow eyes (228.9 ± 29.7 µm and 253.6 ± 27.7 µm, P = 0.009). In the outer retinal defect group, the choriocapillaris plexus (CCP) VD was significantly decreased compared with the fellow eyes (56.4% ± 4.8% and 60.2% ± 4.0%, P = 0.026). In the macula-off RRD group, the postoperative BCVA at 6 months correlated significantly with the ratio of the center CCP VD of the detached eyes to that of the fellow eyes (R2 = 0.207, P = 0.025).

Conclusions: The CCP VD could be related to the anatomical restoration of the outer retinal layer in macula-off RRD. The CCP VD as determined by OCTA could be an indicator of the visual outcome after surgery in macula-off RRD.
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http://dx.doi.org/10.1167/iovs.61.2.35DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7326598PMC
February 2020

Incidence of Terson Syndrome in Treated Subarachnoid Hemorrhage in South Korea: a National Health Insurance Database Study.

Sci Rep 2019 12 13;9(1):19048. Epub 2019 Dec 13.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Korea.

The aim of this study is to investigate the incidence and mortality of Terson syndrome in patients with treated subarachnoid hemorrhage (SAH) in South Korea. In this nationwide, population-based study, we used the National Health Insurance(NHI) database (2011-2015) to identify patients aged ≥18 years. Newly diagnosed non-traumatic SAH, treated using clipping or coil embolization, were identified, and Terson syndrome was defined as newly diagnosed retinal or vitreous hemorrhage within 3 months of SAH diagnosis. We identified 22,864 patients with treated SAH (tSAH), 196 of whom had Terson syndrome, with the cumulative incidence during 5 years of 0.86% (95% CI: 0.74-0.98): 1.10% (95% CI: 0.88-1.33) in men and 0.71% (95% CI, 0.58-0.85) in women. The cumulative incidence of Terson syndrome in patients aged under 40 was higher than in those aged 40 or over (1.41% vs. 0.81%; p = 0.007). The mortality rate of Terson syndrome in patients with tSAH was not different from that in those without Terson syndrome (4.08% vs. 7.30%; p = 0.089). This was the first nationwide epidemiological study of Terson syndrome using a population-based database. The incidence of Terson syndrome in patients with tSAH was higher in those age under 40 than in those aged 40 or over.
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http://dx.doi.org/10.1038/s41598-019-55566-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6911003PMC
December 2019

Comparison of MicroRNA Expression in Tears of Normal Subjects and Sjögren Syndrome Patients.

Invest Ophthalmol Vis Sci 2019 11;60(14):4889-4895

Department of Ophthalmology, Hanyang University Hospital, Hanyang University College of Medicine, Seoul, Republic of Korea.

Purpose: Deregulated expression of several microRNAs (miRNAs) in sera or salivary glands of patients with Sjögren syndrome (SS) has been reported. However, none have investigated miRNAs in samples that can represent lacrimal glands. We compared the miRNAs expression in the tears of SS patients and healthy controls. Moreover, we investigated the correlation between miRNAs expression and ocular staining score (OSS).

Methods: Individual tear samples were collected from 18 SS patients and 8 age-matched controls. Clinical ophthalmologic assessments included Schirmer I test, tear film breakup time (tBUT), and OSS. The expression of 43 different miRNAs in tears was measured using real-time polymerase chain reaction, and compared between the SS patients and controls. And we also compared between the three groups of control, primary SS, and secondary SS patients. The correlation between the miRNA expression and OSS was evaluated.

Results: The expression levels of miR-16-5p, miR-34a-5p, miR-142-3p, and miR-223-3p were significantly upregulated in patients with SS when compared with those in the control group (P < 0.05). The expression of 10 miRNAs (miR-30b-5p, miR-30c-5p, miR-30d-5p, miR-92a-3p, miR-134-5p, miR-137, miR-302d-5p, miR-365b-3p, miR-374c-5p, miR-487b-3p) was significantly downregulated in the SS patients (P < 0.05). Eight miRNAs showed statistically significant differences between the three groups of control, primary SS and secondary SS. All 14 miRNAs with significant differences in SS patients and control group were not significantly correlated with OSSs.

Conclusions: The 14 differentially expressed miRNAs may be involved in the pathogenesis of SS, in particular, related to autoimmunity and neuropathy.
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http://dx.doi.org/10.1167/iovs.19-27062DOI Listing
November 2019

Binarized Neural Network with Silicon Nanosheet Synaptic Transistors for Supervised Pattern Classification.

Sci Rep 2019 08 12;9(1):11705. Epub 2019 Aug 12.

School of Electrical Engineering, Kookmin University, Seoul, 02707, Korea.

In the biological neural network, the learning process is achieved through massively parallel synaptic connections between neurons that can be adjusted in an analog manner. Recent developments in emerging synaptic devices and their networks can emulate the functionality of a biological neural network, which will be the fundamental building block for a neuromorphic computing architecture. However, on-chip implementation of a large-scale artificial neural network is still very challenging due to unreliable analog weight modulation in current synaptic device technology. Here, we demonstrate a binarized neural network (BNN) based on a gate-all-around silicon nanosheet synaptic transistor, where reliable digital-type weight modulation can contribute to improve the sustainability of the entire network. BNN is applied to three proof-of-concept examples: (1) handwritten digit classification (MNIST dataset), (2) face image classification (Yale dataset), and (3) experimental 3 × 3 binary pattern classifications using an integrated synaptic transistor network (total 9 × 9 × 2   162 cells) through a supervised online training procedure. The results consolidate the feasibility of binarized neural networks and pave the way toward building a reliable and large-scale artificial neural network by using more advanced conventional digital device technologies.
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http://dx.doi.org/10.1038/s41598-019-48048-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6690903PMC
August 2019

The influence of low signal-to-noise ratio of axial length measurement on prediction of target refraction, achieved using IOLMaster.

PLoS One 2019 6;14(6):e0217584. Epub 2019 Jun 6.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, South Korea.

Purpose: To evaluate the influence of low signal-to-noise ratio (SNR) of axial length measurement, achieved using IOLMaster, on prediction of target refraction.

Methods: A total of 131 eyes of 131 patients who underwent phacoemulsification with posterior chamber lens implantation were enrolled. Preoperative axial length measurements were performed with the IOLMaster 500 (Carl Zeiss Meditec, Germany); preoperative SNR values were used to divide the eyes into three groups (Group 1; SNR <10, Group 2; 10 ≤ SNR <50, Group 3; 50 ≤ SNR <100). One month and 6 months after cataract surgery, the manifest refraction spherical equivalents (MRSE) were measured. The mean numeric errors (MNE), the mean of the difference between postoperative MRSE, and preoperative target refraction, using the various intraocular lens (IOL) formulas, were calculated and compared among the three groups.

Results: One month after cataract surgery, postoperative MRSE was more hyperopic than preoperative target refraction, calculated by the Haigis formula in group 1, and by the SRK/T formula in group 2. After 6 months, for all formulas in group 1, there were significantly hyperopic results (approximately 0.35 diopter). Upon comparison of MNE among the three groups, group 1 was statistically significantly different from the other groups by Haigis formula.

Conclusions: When the SNR values in biometry, using IOLMaster, are <10, careful attention should be given to determining IOL power, as postoperative spherical equivalents are more hyperopic than preoperative target refraction by IOL formula.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217584PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6553733PMC
February 2020

Evaluation of changes in choroidal thickness and the choroidal vascularity index after hemodialysis in patients with end-stage renal disease by using swept-source optical coherence tomography.

Medicine (Baltimore) 2019 May;98(18):e15421

Department of Ophthalmology.

To evaluate the effect of hemodialysis on choroidal thickness and the choroidal vascularity index (CVI) in patients with end-stage renal disease (ESRD) by using swept-source optical coherence tomography.Thirty-two eyes of 32 patients with ESRD undergoing hemodialysis were recruited prospectively. Detailed ophthalmologic examinations and swept-source optical coherence tomography were performed immediately before and after hemodialysis. Choroidal thickness maps were generated automatically by using built-in software. The CVI was calculated using binarized choroidal optical coherence tomography images. Systemic parameters such as body weight and blood pressure were also measured. The changes in systemic and ocular parameters during hemodialysis were evaluated. Subjects were divided into 2 groups (diabetes mellitus [DM] vs non-diabetes mellitus) for subgroup analysis.Total choroidal thickness showed a significant overall decrease after hemodialysis (-10.9 ± 14.0, P <.001). In the subgroup analysis, total choroidal thickness significantly decreased in both patients with DM (-11.3 ± 13.6, P = .004) and those without (-10.6 ± 14.9, P = .020), but the reduction of choroidal thickness was observed in more subfields in patients with DM than in those without. The CVI did not significantly change after hemodialysis (P = .717). No significant systemic and ocular factors affected the changes in total choroidal thicknesses.Choroidal thickness significantly decreased after hemodialysis in most subfields regardless of the presence of DM. Peri-hemodialysis choroidal changes could be considered in the management of patients with ESRD. Swept-source optical coherence tomography can provide ample and reliable quantitative data for monitoring ocular hemodynamic changes.
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http://dx.doi.org/10.1097/MD.0000000000015421DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6504263PMC
May 2019

Dynamics of nitric oxide level in liquids treated with microwave plasma-generated gas and their effects on spinach development.

Sci Rep 2019 01 30;9(1):1011. Epub 2019 Jan 30.

Plasma Bioscience Research Center, Kwangwoon University, Seoul, 01897, Korea.

In this study, we generated water and phosphate buffer treated with microwave plasma-generated gas in which the major component was nitric oxide (PGNO), and investigated the efficiency of the treated water and buffer in fertilization and sanitation. Real time NO level monitored by an electrode sensor was linearly increased over PGNO injection time, and removal of O from liquid before PGNO injection accelerated NO assimilation into liquids. Residual NO was still present 16 h after PGNO injection was stopped. HO, NO, and NO were also detected in PGNO-treated liquids. Spinach plants applied with 10 and 30 times diluted PGNO-treated water and 0.5 mM phosphate buffer showed slightly higher height and dry weight than control after 5 weeks. Plants grown with 10 and 30 times diluted PGNO-treated water exhibited the increased tolerance to water deficiency. Significant anti-microbial activity within 1 h was observed in un-diluted and in half-diluted PGNO-treated water and 0.5 mM phosphate buffer. Our results suggest that water or phosphate buffer containing NO, HO, NO, and NO can be produced by PGNO treatment, and that PGNO-treated water or buffer can be used as a potential fertilizer enhancing plant vitality with sanitation effect.
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http://dx.doi.org/10.1038/s41598-018-37711-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353906PMC
January 2019

Comparison of repeatability of swept-source and spectral-domain optical coherence tomography for measuring inner retinal thickness in retinal disease.

PLoS One 2019 16;14(1):e0210729. Epub 2019 Jan 16.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Korea.

Purpose: To compare repeatability between SS-OCT and SD-OCT for measurement of macular, macular retinal nerve fiber (mRNFL), and ganglion cell-inner plexiform layer (GC-IPL) thickness in various retinal diseases.

Methods: One hundred and fourteen eyes of 114 subjects were investigated. Seventy-eight eyes with retinal disease and 36 normal eyes underwent two consecutive measurements of macular, mRNFL, and GC-IPL thickness using SS-OCT and SD-OCT. The data were obtained using the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. The eyes with retinal diseases were divided into three subgroups according to central macular thickness (CMT) for analysis. The intraclass correlation coefficient (ICC) was calculated to determine the repeatability of OCT device.

Results: In normal eyes, both OCT devices showed excellent repeatability of macula, mRNFL, and GC-IPL thickness measurements with high ICCs in all ETDRS subfields. In eyes with retinal disease, although SS-OCT showed better repeatability for inner retinal thickness measurements than SD-OCT, the overall ICCs were lower than those in normal eyes. In subgroup analysis, the ICCs in the low CMT group were lower than those in the normal and high CMT groups, particularly when using SD-OCT.

Conclusions: Both OCT devices had comparable repeatability for retinal thickness measurement in normal eyes and eyes with retinal disease. However, the possibility of measurement error should be considered in eyes with a thin and atrophic retina.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0210729PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6334919PMC
October 2019

Biomimetic porous Mg with tunable mechanical properties and biodegradation rates for bone regeneration.

Acta Biomater 2019 01 27;84:453-467. Epub 2018 Nov 27.

Research Institute of Advanced Manufacturing Technology, Korea Institute of Industrial Technology, Incheon 21999, Republic of Korea. Electronic address:

The medical applications of porous Mg scaffolds are limited owing to its rapid corrosion, which dramatically decreases the mechanical strength of the scaffold. Mimicking the bone structure and composition can improve the mechanical and biological properties of porous Mg scaffolds. The Mg structure can also be coated with HA by an aqueous precipitation coating method to enhance both the corrosion resistance and the biocompatibility. However, due to the brittleness of HA coating layer, cracks tend to form in the HA coating layer, which may influence the corrosion and biological functionality of the scaffold. Consequently, in this study, hybrid poly(ether imide) (PEI)-SiO layers were applied to the HA-coated biomimetic porous Mg to impart the structure with the high corrosion resistance associated with PEI and excellent bioactivity with SiO. The porosity of the Mg was controlled by adjusting the concentration of the sodium chloride (NaCl) particles used in the fabrication via the space-holder method. The mechanical measurements showed that the compressive strength and stiffness of the biomimetic porous Mg increased as the portion of the dense region increased. In addition, following results show that HA/(PEI-SiO) hybrid-coated biomimetic Mg is a promising biodegradable scaffold for orthopedic applications. In-vitro testing revealed that the proposed hybrid coating reduced the degradation rate and facilitated osteoblast spreading compared to HA- and HA/PEI-coating scaffolds. Moreover, in-vivo testing with a rabbit femoropatellar groove model showed improved tissue formation, reduced corrosion and degradation, and improved bone formation on the scaffold. STATEMENT OF SIGNIFICANCE: Porous Mg is a promising biodegradable scaffold for orthopedic applications. However, there are limitations in applying porous Mg for an orthopedic biomaterial due to its poor mechanical properties and susceptibility to rapid corrosion. Here, we strategically designed the structure and coating layer of porous Mg to overcome these limitations. First, porous Mg was fabricated by mimicking the bone structure which has a combined structure of dense and porous regions, thus resulting in an enhancement of mechanical properties. Furthermore, the biomimetic porous Mg was coated with HA/(PEI-SiO) hybrid layer to improve both corrosion resistance and biocompatibility. As the final outcome, with tunable mechanical and biodegradable properties, HA/(PEI-SiO)-coated biomimetic porous Mg could be a promising candidate material for load-bearing orthopedic applications.
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http://dx.doi.org/10.1016/j.actbio.2018.11.045DOI Listing
January 2019

Optical coherence tomography angiography analysis of changes in the retina and the choroid after haemodialysis.

Sci Rep 2018 11 21;8(1):17184. Epub 2018 Nov 21.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Korea.

The purpose of this study is to evaluate the effect of haemodialysis on perfused vessel density, choroidal thickness (CT), and retinal thickness in end-stage renal disease (ESRD) using swept-source optical coherence tomography angiography (SS-OCTA). We studied twenty-nine eyes of 29 ESRD patients by ophthalmologic examination and SS-OCTA before and after haemodialysis. The colour-coded perfusion density maps were generated and perfused vessel density was calculated. Changes in systemic and other ocular parameters such as retinal and choroidal thickness were measured and analysed. Total perfused vessel density decreased significantly after haemodialysis in the choriocapillaris; it was not significantly different in the superficial capillary plexus (SCP) and the deep capillary plexus (DCP). Total CT decreased significantly, but total retinal thickness was not significantly different. There was no significant correlation between choriocapillaris perfused vessel density and CT. The reduction in choriocapillaris perfused vessel density correlated with the decrease in systolic and mean arterial blood pressures. The decrease in CT correlated with the ultrafiltration volume. There were no significant systemic and ocular factors affecting change in retinal thickness and perfused vessel density of SCP and DCP. This is the first study to assess the effect of haemodialysis on blood flow changes using SS-OCTA; changes may be more prominent in the choroidal compared to the retinal layer.
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http://dx.doi.org/10.1038/s41598-018-35562-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6249329PMC
November 2018

Compressive optic neuropathy secondary to Ewing sarcoma in the paranasal sinus: A case report.

Medicine (Baltimore) 2018 Nov;97(44):e13027

Department of Ophthalmology.

Rationale: Ewing sarcoma localized in the paranasal sinuses, compressing the optic nerve, is very rare, with no prior case reports PATIENT CONCERNS:: A 68-year-old woman presented with decreased visual acuity in her left eye and paresthesia of the left face. Brain magnetic resonance imaging showed heterogeneously enhancing mass in the left paranasal sinuses with adjacent bone destruction, extending to the extraocular muscles and optic nerve of the left orbit. A biopsy of the nasal cavity confirmed Ewing sarcoma.

Diagnosis: Compressive optic neuropathy secondary to Ewing sarcoma in the paranasal sinuses.

Intervention: Neoadjuvant chemotherapy and radiotherapy were performed.

Outcomes: Resolution of the tumor and increased visual acuity and field of the left eye.

Lessons: Primary head and neck Ewing sarcoma can lead to compressive optic neuropathy, but the tumor responded well to the chemotherapy. Early diagnosis and immediate treatment by close cooperation between the ophthalmologist and oncologist can prevent from permanent visual loss.
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http://dx.doi.org/10.1097/MD.0000000000013027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221559PMC
November 2018

The Association between Female Reproductive Factors and Open-Angle Glaucoma in Korean Women: The Korean National Health and Nutrition Examination Survey V.

J Ophthalmol 2018 20;2018:2750786. Epub 2018 Jun 20.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Republic of Korea.

Purpose: We investigated associations between female reproductive factors and open-angle glaucoma (OAG) in Korean females using the Korea National Health and Nutrition Examination Survey (KNHANES).

Methods: A nationwide, population-based, cross-sectional study was conducted. We enrolled 23,376 participants from the KNHANES who had undergone ophthalmologic exams from 2010 through 2012. Associations between undiagnosed OAG and female reproductive factors such as age at menarche and menopause, parity, history of lactation, and administration of oral contraceptives (OC) or hormone replacement therapy (HRT) were determined using stepwise logistic regression analyses.

Results: Of the enrolled participants, 6,860 participants (397 with OAG and 6,463 without OAG) met our study criteria and were included in the analyses. In the multivariate logistic regression analysis after adjusting for all potential confounding factors, only early menopause (younger than 45 years) was significantly associated with OAG in participants with natural menopause (OR 2.28, 95% CI 1.17-4.46). Age at menarche, parity, history of lactation, and administration of OC or HRT were not significantly associated with OAG.

Conclusions: Only early menopause was associated with an increased risk of OAG in our study, in contrast to previous Western studies reporting both early menopause and late menarche as associated factors.
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http://dx.doi.org/10.1155/2018/2750786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6031087PMC
June 2018

Three-Dimensional Printed Poly(vinyl alcohol) Substrate with Controlled On-Demand Degradation for Transient Electronics.

ACS Nano 2018 Jun 25;12(6):6006-6012. Epub 2018 May 25.

School of Electrical Engineering , Kookmin University , Seoul 02707 , Korea.

Electronics that degrade after stable operation for a desired operating time, called transient electronics, are of great interest in many fields, including biomedical implants, secure memory devices, and environmental sensors. Thus, the development of transient materials is critical for the advancement of transient electronics and their applications. However, previous reports have mostly relied on achieving transience in aqueous solutions, where the transience time is largely predetermined based on the materials initially selected at the beginning of the fabrication. Therefore, accurate control of the transience time is difficult, thereby limiting their application. In this work, we demonstrate transient electronics based on a water-soluble poly(vinyl alcohol) (PVA) substrate on which carbon nanotube (CNT)-based field-effect transistors were fabricated. We regulated the structural parameters of the PVA substrate using a three-dimensional (3D) printer to accurately control and program the transience time of the PVA substrate in water. The 3D printing technology can produce complex objects directly, thus enabling the efficient fabrication of a transient substrate with a prescribed and controlled transience time. In addition, the 3D printer was used to develop a facile method for the selective and partial destruction of electronics.
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http://dx.doi.org/10.1021/acsnano.8b02244DOI Listing
June 2018

Three-Dimensionally Printed Micro-electromechanical Switches.

ACS Appl Mater Interfaces 2018 May 30;10(18):15841-15846. Epub 2018 Apr 30.

School of Electrical Engineering , Kookmin University , Seoul 02707 , Korea.

Three-dimensional (3D) printers have attracted considerable attention from both industry and academia and especially in recent years because of their ability to overcome the limitations of two-dimensional (2D) processes and to enable large-scale facile integration techniques. With 3D printing technologies, complex structures can be created using only a computer-aided design file as a reference; consequently, complex shapes can be manufactured in a single step with little dependence on manufacturer technologies. In this work, we provide a first demonstration of the facile and time-saving 3D printing of two-terminal micro-electromechanical (MEM) switches. Two widely used thermoplastic materials were used to form 3D-printed MEM switches; freely suspended and fixed electrodes were printed from conductive polylactic acid, and a water-soluble sacrificial layer for air-gap formation was printed from poly(vinyl alcohol). Our 3D-printed MEM switches exhibit excellent electromechanical properties, with abrupt switching characteristics and an excellent on/off current ratio value exceeding 10. Therefore, we believe that our study makes an innovative contribution with implications for the development of a broader range of 3D printer applications (e.g., the manufacturing of various MEM devices and sensors), and the work highlights a uniquely attractive path toward the realization of 3D-printed electronics.
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http://dx.doi.org/10.1021/acsami.8b01455DOI Listing
May 2018

Anomalous coagulation factors in non-arteritic anterior ischemic optic neuropathy with central retinal vein occlusion: A case report.

Medicine (Baltimore) 2018 Apr;97(15):e0437

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Korea.

Rationale: Non-arteritic anterior ischemic optic neuropathy (NAION) is characterized by sudden, painless visual loss and optic disc edema. NAION occurs mainly in the presence of cardiovascular disease and hypercoagulability, mainly in patients over 50 years of age. We experienced a case of NAION associated with central retinal vein occlusion (CRVO) in a young man with no underlying disease.

Patient Concerns: A 46-year-old man was referred to our clinic following a sudden loss of vision in his right eye. The patient exhibited no underlying disease and reported no ongoing medication. Significant visual loss and visual disturbance of the right eye were observed. The pupil of the right eye was enlarged and an afferent pupillary defect was observed. On fundus examination, retinal hemorrhage was observed in the peripheral retina; macular edema was observed in optical coherence tomography analysis. However, optic disc edema was not evident. No abnormal findings were found in routine blood tests for hypercoagulability. After 3 days of steroid intravenous injection, macular edema disappeared and visual acuity was improved, but optic disc edema began to appear. One week later, optic disc edema was evident and visual acuity was significantly reduced; thus, the patient was diagnosed with NAION. In fluorescein angiography, peripheral retinal ischemia was observed, suggesting that CRVO was complicated. Blood tests, including analysis of coagulation factors, were performed again, showing that coagulation factors IX and XI were increased.

Diagnoses: Anomalous coagulation factors in non-arteritic anterior ischemic optic neuropathy with central retinal vein occlusion.

Interventions: Systemic steroids were administered.

Outcomes: One month later, optic disc edema and retinal hemorrhage gradually diminished and eventually disappeared; however, visual acuity did not recover.

Conclusion: In young patients without underlying disease, cases of NAION require careful screening for coagulation disorders. Even if there is no abnormality in the test for routine coagulation status, it may be necessary to confirm a coagulation defect through an additional coagulation factor assay.
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http://dx.doi.org/10.1097/MD.0000000000010437DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5908582PMC
April 2018

Wide scan imaging with swept-source optical coherent tomography for glaucoma diagnosis.

PLoS One 2018 5;13(4):e0195040. Epub 2018 Apr 5.

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Korea.

Purpose: To determine glaucoma-discriminating abilities of macular and circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurements of wide scan (12X9mm) using swept-source optical coherence tomography (SS-OCT) compared to measurements of standard macula and disc scans (6 X 6 mm).

Methods: This retrospective chart review study included 60 glaucomatous and 62 healthy eyes of total 122 subjects who visited a glaucoma clinic and were examined with wide, standard macula, and standard disc scans of SS-OCT (DRI-OCT-1 Atlantis; Topcon Inc., Tokyo, Japan) on the same day. Thickness measurements of the ganglion cell layer plus inner plexiform layer (mGCIPL), mGCIPL plus nerve fiber layer (mGCC), and total retinal layer (TRL) were assessed in wide and standard macula scans. Thickness measurements of cpRNFL were assessed in wide and standard disc scans. The repeatability and agreement of measurements taken in each scan were evaluated using intraclass correlation coefficients (ICCs). The abilities of parameters to discriminate between glaucoma and normal groups were assessed using areas under receiver operating characteristic curves (AUCs).

Results: The repeatability and agreement of all parameters showed high ICC values (all ≥ 0.800). AUCs for mGCIPL thickness were 0.710-0.847 and 0.701-0.836 in standard macula and wide scans, respectively. AUCs for cpRNFL thickness were 0.749-0.902 and 0.726-0.897 in standard disc and wide scans, respectively. There were no significant differences in AUCs between wide and standard scans.

Conclusions: The agreement between SS-OCT wide and standard scans for mGCIPL, mGCC and cpRNFL measurements were excellent. As the glaucoma-discriminating ability of wide scans was comparable to that of standard macula/disc scans, a single wide scan can replace separate standard macula/disc scans for evaluating glaucoma.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0195040PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5886522PMC
July 2018

In vitro and in vivo evaluation of polylactic acid-based composite with tricalcium phosphate microsphere for enhanced biodegradability and osseointegration.

J Biomater Appl 2018 05 15;32(10):1360-1370. Epub 2018 Mar 15.

Materials Science and Engineering, 26725 Seoul National University , Seoul, Republic of Korea.

A biodegradable polylactic acid composite containing tricalcium phosphate microsphere was fabricated. The composite exhibited enhanced biocompatibility and a well-interconnected porous structure that enabled tissue ingrowth after degradation. The tricalcium phosphate microspheres had an average size of 106 ± 43 μm and were incorporated into the polylactic acid matrix using a high-shear mixer. The resulting bioactivity and hydrophilicity were enhanced to levels comparable to those of a polylactic acid composite containing tricalcium phosphate powder, which is a well-known material used in the medical field. An accelerated 30-day degradation test in HCl revealed successful generation of an open porous structure with ∼98% interconnectivity in the polylactic acid-tricalcium phosphate microsphere composite, demonstrating the potential of this material to induce enhanced osseointegration in the later stage of bone regeneration. The early stage osseointegration was also evaluated by implanting the composite in vivo using a rabbit femoral defect model. After 16 weeks of implantation, the bone-to-implant contact ratio of the polylactic acid-tricalcium phosphate microsphere composite was enhanced owing to tissue ingrowth through the generated pores near the surface.
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http://dx.doi.org/10.1177/0885328218763660DOI Listing
May 2018
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