Clinically used bio-based tissue sealants bring in the risk of animal-borne infections, non-degradability, allergic reactions, tissue compression, tissue necrosis, and poor wet adhesion. Motivated by these unsatisfactory properties of existing tissue sealants, herein, we designed a library of solvent-and initiator-free hydrophobic musselinspired degradable tissue adhesives that can stick and seal the epidermis, pericardium, and Glisson's capsule under physiologically relevant wet conditions. By varying the molar ratio of the functional groups, we obtained polyester adhesive sealants with similar surface energy and varying viscosity. The careful examination of the wetting behavior of these polyester adhesive sealants on tissue surfaces showed that the polyester adhesive sealant with lower viscosity has higher intrinsic work of adhesion, which allowed them to adhere to strongly hydrated surfaces such as pericardium and Glisson's capsule. Because of the lower intrinsic work of adhesion, the polyester adhesive sealant with higher viscosity only adhered to the relatively hydrophobic surface (epidermis). The strong wet adhesion to tissue surfaces, cell-compatibility, hydrolytic degradability, and radical scavenging nature of these polyester adhesive sealants make them potential candidates for wound closure procedures.

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Real-time uniaxial strain-induced birefringence in loosely crosslinked double-network (DN) hydrogels synthesized from acrylamide (AAm) and N,N-dimethyl(acrylamide) (DMA) was measured. Tensile tests were performed at different extension rates from quasi-static conditions to very rapid tests followed by a holding for relaxation. Both DN hydrogels exhibit negative birefringence whose absolute value increased with extension and remained constant during relaxation. DN hydrogel synthesized from AAm displayed a linear stress optical (birefringencetrue stress) behavior, however, a nonlinear trend was observed for the DN gel synthesized from DMA. A simple photoelastic model was developed based on the mechanical behavior of the gels using Fung elastic potential and Brewster's stress-optical law, and the model was compared with the experimental data.

The effect of nanoclay on the thermal stability of polystyrene (PS)-poly(methyl methacrylate) (PMMA) core-shell nanocomposites morphology prepared by in situ suspension polymerization technique was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the formation of a PS-PMMA core-shell structure, both in the absence and presence of the clay. Wide angle X-ray diffraction (WAXD) indicated the formation of a highly intercalated expanded clay morphology in the core-shell composite particles irrespective of the location of the clay in the nanocomposites. Thermo gravimetric analysis (TGA) indicated an improvement in the thermal stability of the core-shell nanocomposites compared to that of the neat PS-PMMA coreshell one. Differential scanning calorimetry (DSC) showed that the core-shell nanocomposite particles containing the clay had a higher glass transition (T g ) temperature than the neat PS-PMMA core-shell composites particles. On the other hand, the improvement in the thermal stability of the PS-PMMA core-shell composites was found to depend strongly on the location and loading of the clay in the core-shell nanocomposites. FTIR indicated a probable interaction between the carbonyl (>C=O) group of PMMA and hydroxyl (-OH) group of the clay.

A model system of styrene (St) and methyl methacrylate (MMA) was copolymerized in an NMR tube at 60 °C using 2,2′-azobis(isobutyronitrile) as the initiator and pyridazine as an internal standard to optimize an in situ 1 H NMR spectroscopic method for determining reactivity ratios by generating data at hundreds of instantaneous comonomer compositions (244 data points from 8 to 91 mol % St) starting with only nine initial comonomer compositions. The radical reactivity ratios of styrene (r St = 0.697 ± 0.010) and methyl methacrylate (r MMA = 0.491 ± 0.007) were determined by nonlinear least-squares fitting of a Mayo−Lewis plot of the instantaneous copolymer composition as a function of the comonomer feed composition using the terminal model and MINITAB statistical software, in which the copolymer composition was calculated by assuming that all comonomer consumed was converted to copolymer without side reactions; the results were similar to accepted literature values for the terminal and implicit penultimate models. After correcting for changes in the "lock" value at the initial stages of the copolymerization (because of solids formed in the sealed NMR tube), the same technique was used to determine the reactivity ratios of 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA; r FOSA = 1.624 ± 0.048) and 2-(N-ethylperfluorooctanesulfonamido)ethyl methacrylate (FOSM; r FOSM = 2.876 ± 0.083) in their radical copolymerizations with N,Ndimethylacrylamide (DMA; r DMA = 1.126 ± 0.031 with FOSA; r DMA = 0.859 ± 0.026 with FOSM).

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(2-Bromo-n-nonan-1-oxycarbonyl)ethyl acrylate was synthesized as an inimer for self-condensing vinyl polymerization (SCVP) to produce hyperbranched poly(n-nonyl acrylate), either as a homopolymer or as a copolymer with n-nonyl acrylate. The inimer was homopolymerized and copolymerized by atom transfer radical polymerization (ATRP) and activator generated by electron transfer ATRP to produce soluble polymers with broad polydispersities (up to -D 5 9.91), which is characteristic of hyperbranched polymers produced by SCVP. The resulting hyperbranched (co)polymers were crosslinked by atom transfer radical coupling in both one-pot and two-step procedures. The radical-radical crosslinking reaction is extremely efficient, resulting in hard plastic particles from the homopolymer of (2-bromo-n-nonan-1-oxycarbonyl)ethyl acrylate synthesized in bulk. Crosslinked organogels that swell in tetrahydrofuran were formed when the rate of crosslinking decreased using acetonitrile solutions. Dynamic shear and stress relaxation experiments demonstrated that the dry network behaves as a covalently crosslinked soft gel, with a glass transition at 250 8C according to differential scanning calorimetry.

Tissue Engineering is emerging as a next generation therapeutical methods to overcome shortcomings of tissue defects from within using living cells and multidisciplinary fields of science and technology. Human beings have been greatly affected by various diseases which lead to degradation of bone tissue such as osteoporosis. It is difficult for the human body to regrow bone tissue affected by such diseases. For this reason it is necessary to develop methods by which bone tissue can be grown in vitro and can then replace the degraded tissue in human beings. Hydroxyapatite (HAp) being structurally similar to bone tissue of living organisms can be actively used as a matrix for the culturing of osteoblast cells which can then be incorporated into a human being at the diseased site to regenerate osseous tissue. Moreover HAp is widely used as a matrix due to its increased biocompatibility as well as its exceptional osteoconductivity. In addition, HAp has also been used in the form of composite like HAp-chondroitin sulphate(HAp-ChS) composite matrices that have been tested on Japanese white rabbits and have yielded significant results. Furthermore, metal ions doped with HAp have also been known to yield greater osteoconductivity. One of the most prominent of these metal ions is Zinc which can be found as a trace metal in bone and aids in bone metabolism and development. Zinc is known to initiate the activity of the enzyme aminoacyl-tRNAsynthetase which thus helps in translation and leads to protein synthesis. It also helps in the expression of genes which code transcription factors such as the Runx2 transcription factor required for differentiation of osteoblast cells as well as optimises the development of osteoclast cells to regulate resorption. Furthermore, zinc ions are capable of showing antimicrobial and antifungal properties which are extremely beneficial to prevent contamination during cell culture. MG63 osteoblast cells are primarily used for cell culture on HAp matrix generally for a few weeks to observe the efficiency of the matrix. MG63 cell lines have characteristics which are nearest to human osteoblast cells. Different matrices with same composition but varying surface roughness are also prepared to increase adhesion of the cells to the matrix, determined by various cell viability assays. It is found through comparative study that zinc doped HAp matrices yield significant growth of cells in comparison to pure HAp matrices when formed at a temperature of 1250oC and that does not exhibit any cytotoxic effect. In the present report an idea of the various research work conducted for the development of zinc doped Hap matrix in the field of bone tissue engineering is provided.