Key Engineering Materials Vols. 342-343

Abstract: Bone cements incorporated with montmorillonite (MMT) were prepared in an attempt to improve their mechanical properties. The cements were characterized using particle size analysis, gel permeation chromatography, viscosity measurements, X-ray diffraction, transmission electron microscopy, and mechanical properties. The average particle size and molecular weight of the PMMA powders used were 47 μm and 100,000 g/mol, respectively. The incorporation of MMT led to an increase in viscosity of the bone cement but did not severely affect its setting temperature or the amount of residual monomer. Regardless of the MMT mixing methods used, in this case MMT being mixing in liquid and powder components, sodium MMT (SMMT) was not well dispersed in the bone cements, which was believed to be due to its hydrophilicity. Organophilic MMT (OMMT) was better dispersed in the liquid component than in the powder component. The tensile and compressive strengths of the bone cements with 0.5 wt% OMMT mixed in the liquid component were 35.9 and 119.6 MPa, respectively, which were considerably higher than those of the bone cements with 0.5 wt% OMMT mixed in the powder component (27.9 and 100.5 MPa, respectively).

Abstract: Thermoplastic polyurethanes are versatile polymers much used for biomedical applications due to their mechanical properties and biocompatibility. Like most implantable materials they are susceptible to bacterial colonization, particularly in applications at high risk of bacterial contamination such as percutaneous catheters. The objective of this study was to assess the antibacterial activity and the cell responses to a series of nanocomposite variants fabricated from a polyether polyurethane and organically modified silicates containing either antibacterial dispersing agents, non-antibacterial dispersing agents, or combinations of the two. The results suggest that co-modification is a promising approach for modulating both bacterial and mammalian cell responses to achieve appropriate antibacterial properties without cell inhibition.

Abstract: The effect of different hydroxyapatite particles on malignant melanoma cell was evaluated in vitro. Two kinds of short-rode hydroxyapatite particles, which range from 0.4 to 1 um and 0.5 to 1.5 um, were co-cultured with human’s malignant melanoma (MM) cell line A375 for 24, 48, and 72 h. Both of these HA particles showed the same cell proliferation rate as blank control, and there was no statistically significant correlation of matrix metalloproteinases-2 (MMP-2) expression to the HA particle size. SEM images showed that the membrane of tumor cell, which co-cultured with HA particles, was shrunk. The cell superficial sentus was reduced and small size particle’ effect was more obvious. Since immunohistochemistry and SEM data are qualitative technique, further precise methods might bring more information about the effect of HA particles on tumor behaviors. But this study can provide the bio-security test of micrometer HA particles in transplantation after tumor excision.

Abstract: In vitro cell behaviors of calvarial osteoblasts (MC3T3) were evaluated by seeding them on both the surface and inside of in situ hyaluronic acid-poly(ethylene oxide) (HA-PEO) hydrogel, either after or before incorporation of mixture micro-particles of hydroxyapatite-β-tricalcium phosphate on/inside the hydrogel, respectively. Cellular behaviors such as adhesion and proliferation on the surface and inside the gel were evaluated with light microscopy and a microplate reader by focusing on the interactions of cell-HA-PEO as well as cell-hydroxyapatitetricalcium phosphate micro-particle surface in the gel. Cell adhesion and spreading seemed to be enhanced by supplying the micro-particles to the inside the HA-PEO hydrogel, compared to the results of the HA-PEO hydrogel itself.

Abstract: The achievement of biological sealing is determined by the quality of the skin attachment on the surface of the percutaneous implant in the area where the implant penetrates the skin. It has been known that certain surface features of the implants can significantly influence the interactions between cells and substrate. In this study, titanium plates were bioactivated through anode-oxidization firstly, and then cultured with human epithelium cells for 72h. Untreated Ti plates were used as control. After the samples were dehydrated, the morphology of the cultured epithelium cells was tested with Scanning electron microscopy (SEM). The surfaces of control group did not enhance epithelium cell attachment and growth, while the bioactivated microporous surface of anode-oxidized group would be beneficial to induce the formation of the pseudopod of epithelium cell, and then interlock the human epithelium cells through the pseudopod, which imply that the surface modification method of anode oxidization may be one of the most effective methods to resolve the biological sealing.

Abstract: The purpose of this study was to investigate the effects of Galla Rhois, Psoralea corylifolia, Camellia sinensis, Salvia miltiorrhiza and Platcodon grandiflorum on the inhibition of artificial dental plaque formation and the cytotoxicity of the herbal extracts on human gingival fibroblasts. The analysis was carried out with the measurment of dental plaque weight and the cell survival rate of human gingival fibroblasts. It showed that Galla Rhois, Psoralea corylifolia, Camellia sinensis and Salvia miltiorrhiza inhibited the artificial dental plaque formation and did not reduce the cell viability of human gingival fibroblasts.

Abstract: We investigated phospholipid polymer hydrogels containing Fe3+ ions (PMA/PMB/Fe hydrogel) for their use as antiadhesive materials in the healing tissues. These hydrogels were prepared from the aqueous solutions of poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-comethacrylic acid) (PMA) and poly(MPC-co-n-butyl methacrylate) (PMB). The PMA/PMB hydrogel is formed by the intermolecular interactions between PMA and PMB, and it reversibly dissociates under physiological conditions. The addition of Fe3+ ions could control the gelation time and the dissociation time. Mechanical properties such as the gelation time and viscoelastic properties can be controlled by the FeCl3 concentration. With regard to biocompatibility, no evidence of inflammation was observed in vivo. Therefore, the PMA/PMB/Fe hydrogel has a potential to be used as an antiadhesive material.

Abstract: Stabilization of the fibrous protein collagen is important in biomedical applications. This study investigated the efficacy of degradation control of collagen using (-)-epigallocatechin-3-Ogallate (EGCG). EGCG treatment of collagen in solid state was carried out and collagen sponges produced were characterized by measuring the physicochemical properties such as gel fraction, the enzymatic degradability and cytocompatibility. According to gel fraction, EGCG-treated sponges showed the increase of insolubility compared to intact sponges. It showed that EGCG played a role in a crosslinker of collagen. Through in vitro enzymatic degradation test, EGCG-treated collagen sponges showed significant enhancement of resistance to collagenase in comparison with 25 mM EDC-treated collagen sponges. Also, cell proliferation assays showed that 40 mM EGCG-treated collagen sponges exhibited similar cytocompatibility properties compared with tissue culture plate. In summary, EGCG treatment of collagen sponges increased the stability of collagen. Therefore, crosslinking of collagen based scaffold with EGCG imparted more desirable properties, making it more applicable for use as a scaffold in tissue engineering applications.

Abstract: We investigated the bioconjugation of proteins on polymer nanoparticles covered with bio-inert phosphorylcholine groups. Poly[2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate-co-p-nitrophenyloxycarbonyl polyethyleneglycol methacrylate] was used as an emulsifier and a surface modifier to prepare the poly (L-lactic acid) nanoparticles by a solvent evaporation technique. The diameter and surface potential of the nanoparticles were approximately 260 nm and –5 mV, respectively. We considered that the polymer chain that transformed the conformation by change in pH may be used as a method of controlling the bioreaction. The enzyme activity in a different pH under the coexistence of poly (glutamic acid) (PGA) and the enzyme was measured. Therefore, the enzyme activity increased in pH 6 in PGA/enzyme mixture system compared with that in pH 7 while the activity was constant in the enzyme single conjugation regardless of the pH change.

Abstract: Non-biofouling surfaces with polymer-based substrate were prepared for manufacturing microfluidic devices. It was done by constructing biocompatible poly(2-methacryloyloxyethyl phosphorylcholine(MPC)) brushes using surface-initiated graft polymerization method based on dithiocarbamate as photoiniferter. The density and length of the polymer chains were varied by changing the composition of the photoiniferter moiety in the base polymer (macrophotoiniferter) and the photoirradiation time, respectively. The molecular weight and thickness of the poly(MPC)- grafted chains were 320 kDa and 95±14 nm, respectively. Characterizations of the poly(MPC) modified surfaces were conducted by water contact angle, X-ray photoelectron spectroscopy, atomic force microscope. Protein adsorption resistance of these modified surfaces was then investigated by contacting with human plasma protein dissolved in phosphate buffered saline. These poly(MPC)-modified surfaces effectively reduced protein adsorption.