Browsing by Subject "Biocompatible Materials"

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    Assessing monocyte phenotype in poly(γ-glutamic acid) hydrogels formed by orthogonal thiol–norbornene chemistry
    (IOP, 2021-07) Kim, Min Hee; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Hydrogels with tunable properties are highly desirable in tissue engineering applications as they can serve as artificial extracellular matrix to control cellular fate processes, including adhesion, migration, differentiation, and other phenotypic changes via matrix induced mechanotransduction. Poly(γ-glutamic acid) (PGA) is an natural anionic polypeptide that has excellent biocompatibility, biodegradability, and water solubility. Moreover, the abundant carboxylic acids on PGA can be readily modified to introduce additional functionality or facilitate chemical crosslinking. PGA and its derivatives have been widely used in tissue engineering applications. However, no prior work has explored orthogonal crosslinking of PGA hydrogels by thiol-norbornene (NB) chemistry. In this study, we report the synthesis and orthogonal crosslinking of PGA-norbornene (PGANB) hydrogels. PGANB was synthesized by standard carbodiimide chemistry and crosslinked into hydrogels via either photopolymerization or enzymatic reaction. Moduli of PGA hydrogels were readily tuned by controlling thiol-NB crosslinking conditions or stoichiometric ratio of functional groups. Orthogonally crosslinked PGA hydrogels were used to evaluate the influence of mechanical cues of hydrogel substrate on the phenotype of naïve human monocytes and M0 macrophages in 3D culture.
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    Assessment of electromechanically stimulated bone marrow stem cells seeded acellular cardiac patch in a rat myocardial infarct model
    (IOPP, 2021) Öztürk, Şükrü; Shahbazi, Reza; Zeybek, Naciye Dilara; Kurum, Barıs; Gultekinoglu, Merve; Aksoy, Eda Ayse; Demircin, Metin; Ulubayram, Kezban; Medicine, School of Medicine
    In this study, we evaluated cardiomyogenic differentiation of electromechanically stimulated rat bone marrow-derived stem cells (rt-BMSCs) on an acellular bovine pericardium (aBP) and we looked at the functioning of this engineered patch in a rat myocardial infarct (MI) model. aBP was prepared using a detergent-based decellularization procedure followed by rt-BMSCs seeding, and electrical, mechanical, or electromechanical stimulations (3 millisecond pulses of 5 V cm-1at 1 Hz, 5% stretching) to enhance cardiomyogenic differentiation. Furthermore, the electromechanically stimulated patch was applied to the MI region over 3 weeks. After this period, the retrieved patch and infarct region were evaluated for the presence of calcification, inflammatory reaction (CD68), patch to host tissue cell migration, and structural sarcomere protein expressions. In conjunction with any sign of calcification, a higher number of BrdU-labelled cells, and a low level of CD68 positive cells were observed in the infarct region under electromechanically stimulated conditions compared with static conditions. More importantly, MHC, SAC, Troponin T, and N-cad positive cells were observed in both infarct region, and retrieved engineered patch after 3 weeks. In a clear alignment with other results, our developed acellular patch promoted the expression of cardiomyogenic differentiation factors under electromechanical stimulation. Our engineered patch showed a successful integration with the host tissue followed by the cell migration to the infarct region.
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    An In-Vitro Comparison of Microleakage With E. faecalis In Teeth With Root-End Fillings of Proroot MTA and Brasseler's EndoSequence Root Repair Putty
    (2011) Brasseale, Beau J. (Beau John), 1980-; Spolnik, Kenneth Jacob, 1950-; Vail, Mychel Macapagal, 1969-; Legan, Joseph J.; Zunt, Susan L., 1951-; Moore, B. Keith; Gregory, Richard L.
    Brasseler USA (Savannah, GA) developed and introduced a bioceramic putty called EndoSequence Root Repair Material (ERRM) that can be used as a retrofilling material for surgical endodontics. The material is said to have many of the same chemical, physical, and biological properties as mineral trioxide aggregate (MTA), but with superior handling characteristics. The material is composed of calcium silicates, monobasic calcium phosphate, zirconium oxide, tantalum oxide, proprietary fillers, and thickening agents. ERRM is said by the manufacturer to bond to adjacent dentin, have no shrinkage, be highly biocompatible, hydrophilic, radiopaque, and antibacterial due to a high pH during setting. Investigations on the sealing properties of this material have not yet been conducted. The purpose of this study was to compare the microbial leakage of Enterococcus faecalis in teeth with root-end fillings using ProRoot MTA and Brasseler’s ERRM in a dual-chamber bacterial leakage model as described by Torabinejad and colleagues. The aim of this investigation was to compare the bacterial microleakage of these two root-end filling materials exists. Sixty-two human, single-rooted, mandibular premolars in which extraction was indicated were accessed and instrumented in an orthograde fashion with hand and rotary files. Root resection of the apical 3 mm was then completed and root-end retropreparations were created for placement of root-end filling material. Twenty-seven of these premolars had root-end fillings using ProRoot MTA and 27 had root-end fillings using ERRM. Two teeth were used as a positive control group with no root-end filling, and two other teeth were used as a negative control group and were sealed and coated with dentin bonding agent. The teeth were then evaluated for microleakage using a dual-chamber bacterial microleakage model for 40 days as described by Torabinejad and colleagues. Microleakage was determined by the presence of turbidity in the lower chamber of the apparatus and was assessed each day. Fresh samples of E. faecalis were used every three days to inoculate the apparatus and serve as a bacterial challenge for the materials. Results were recorded every day for 30 days. The outcome of interest (bacterial turbidity) and time-to-leakage (in days) were determined for each of the samples. Survival analysis was used to compare the two groups with a Kaplan-Meier plot to visualize the results and a nonparametric log-rank test for the group comparison. The microleakage of ERRM was not statistically different (p > 0.05) than leakage of ProRoot MTA when subjected to E. faecalis over the 40 day observation period. Both groups had a small number of early failures (within 4 days) and no leakage was observed for the remaining 40 days of the study. Therefore, the null hypothesis was rejected. The results of this research support the use of either of these two materials when compared with the controls. The microleakage of Brasseler’s EndoSequence Root Repair Material was at least as good as ProRoot Mineral Trioxide Aggregate when tested with E. faecalis.