Advanced Materials Research Vols. 47-50

Abstract: This paper introduces a new method of surface modification by self-assembled monolayer (SAM) and polymer monolayer grafting. Since most of the glass surfaces lack the reactive functional group, an activation process with 3-(trimethoxysilyl)propyl methacrylate(TPM) is used in our experiment to generate the vinyl reactive sites on the substrate surface for further graft polymerization. The TPM saline layer acts as the “anchor” part to link the functional part onto the surface of substrate. The paper summarizes the surface modifications by the polymerizations of PEGMA, AA(Acrylic acid) and NVP(Nitrogen-vinyl-2-pyrrolidone) respectively and their applications for protein adsorption and cell adhesion through a series of measurements. In previous research, AA and NVP had also been adopted for surface treatment and had achieved good results. The substrate can be glass, alumina, silicon, metals or stainless steel. We choose glass as our substrate during the experiment.

Abstract: In this work, the effect of multiwalled carbon nanotubes (NWNTs) incorporation in poly(L-lactide) (PLLA) on the human osteoblast-like cell (Saos-2) growth behaviour was studied. The PLLA/MWCNT composite with different ratio of PLLA to MWCNT was fabricated using solvent-casting technique. MWCNT was detected by XRD and showed the successful incorporation of MWCNT into PLLA. Fixed amount of cells were cultured on different composite. Cell viability assay and scanning electron microscopy were used to evaluate cell adhesion, morphology and cytoskeleton development on the scaffolds. The activity of mitochondrial dehydrogenase (MD) enzyme was evaluated by MTT substrate and p-nitrophenyl phosphate substrate. The results demonstrated cytoskeleton fibre and good adhesion of osteoblast cells to the composite surface. No significant differences of cell viability were found for the PLLA/MWCNT composite and controls. The incorporation of MWCNT into PLLA can obviously enhance the MD activity. We believe that sample with more MWCNT provided favourite interactions to the human osteoblast-like cells, which indicate a potential candidate in bone tissue engineering.

Abstract: The bioactivity of potassium titanate whiskers (PTW) was evaluated by soaking in simulated body fluids (SBF, Kokubo solution). At first, PTW was chemically treated by 1 M HCl and 1 M NaOH solutions at 60 oC for 48 h, respectively. Then PTW before and after treated were soaked in SBF solution and cultured at 37 oC for different times. The apatite deposit on PTW was examined by FTIR and SEM/EDX. The results showed that there was not apatite deposit on the raw PTW even after soaked for 14 days while apatite appeared on the treated PTW after soaked for only 7 days. This implies that treatment by HCl/NaOH solutions can improve the in vitro bioactivity of PTW. The possible mechanism is that more Ti–OH groups occur after treatment and induce Ca2+ and PO4 3- aggregate and accelerate to deposit of apatite. The bioactive PTW with good biocompatibility is a potential candidate as reinforcing agent to improve the mechanical properties of calcium phosphate ceramics or cements.

Abstract: We have been interested in the soluble interpolyelectrolyte complexes (IPEC) between DNA and the cationic comb-type copolymers, poly(L-lysine)-graft-dextran (PLL-g-Dex), consisting of a polylysine backbone and abundant hydrophilic graft chains of dextran as a model of nucleic acid-binding proteins. In this paper, we described the kinetic effect of the copolymers on the DNA hybridization. We found that the cationic copolymer at nano molar concentrations in cationic groups accelerated DNA duplex formation by two orders under physiologically relevant conditions.

Abstract: In this paper, a new approach for controllable bio-fabrication of patterened cellulose nano-fibers has been proposed by micro-fluidic techniques, via the combination of biological technology and nanotechnology. We attempted to make sure whether A. xylinum can regularly move within micro-fluidic channels and further to clarify how the flow can direct and control the assembly of cellulose nano-fibers. The movement of A. xylinum within the micro-fluidic channels was observed in vivo by real time video microscopy. The well-patterned materials have great potential utility in tissue engineering.

Abstract: This paper presents a two-step approach for electrospinning of hydroxyapatite/chitosan (HAp/CTS) nanocomposite, which was firstly prepared by an in situ co-precipitation method. Continuous HAp/CTS nanofibers with diameters of 214 ± 25 nm were produced successfully with the aid of an ultrahigh molecular weight poly(ethylene oxide) (UHMWPEO). The HAp nanoparticles with aggregations to some extent were incorporated along the electrospun CTS-based nanofibers. And their crystallite structure can be preserved to some extent although an acidic solvent system was used. Current nanocomposite nanofibers of HAp/CTS may be of potential interest for bone repair and regeneration application.

Abstract: Plasma polymerization is an effective method to directly deposit ultra-thin film on substrates with advantageous properties such as good adhesion and biocompatibility. In this paper, the monomers containing amine groups with various unsaturated structures (propylamine, allylamine) are chosen to provide amine functionalities and to promote biocompatibilities for the polymerized thin films. The deposition rates revealed by measuring the thickness of thin films are characterized by profilometer under various plasma conditions. FTIR and AFM are used to study the chemical structures and morphology of the deposited thin films. In order to examine the applicability of the deposited polymers for biosensors, the activities of the incorporated biomolecules on deposited thin films are analyzed. Chinese hamster ovary (CHO) cells are cultivated on the polymerized thin films. Both propylamine and allylamine polymerized thin films show enhanced cell viability than on glass slide substrates.

Abstract: The effect of plasma treatment on physicochemical properties of a porous polypropylene (PP) membrane was studied. The treated porous membranes were used as substrates for Acetobacter xylinum to grow and produce microbial cellulose pellicle. The effects of modifications on wettability and morphology were correlated with the growth rate of microbial cellulose. The CO2, O2 and N2/H2 plasmas modification not only can increase the hydrophilicity of the membrane but also enhance the growth of microbial cellulose. For 14 days of cultivation, the amount of microbial cellulose found on O2 treated substrate was approximately 2 folds of that on the untreated membranes.

Abstract: In this paper, water-soluble polymer PEG of different molecular weight was grafted on the SIS films by plasma surface grafting modification. These surface modifed SIS films were characterized by contact angle measurement, ATR-FTIR and XPS. The contact angle of water decreased significantly while the surface free energy and hydrophilicity increased. The relative ratio of oxygen to carbon increased from 0.06 to 0.21 . All the results revealed that the PEG molecules were incorporated onto the surface of the SIS films through covalent bonds and the surface properties changed to some extent. The blood compatibilities of the surface-modified SIS films were examined using APTT, APTT of the SIS-PEG2000 exhibted the best blood compatibility

Abstract: Nanocrystalline Zn-substituted calcium hydroxyapatite (HA) powder was synthesized by wet chemical method. Detailed characterization was carried out with both experimental techniques and numerical simulation method. X-ray diffraction (XRD) patterns show the calcium phosphate maintains as the apatite phase when the atomic ratio of Zn/(Zn+Ca) is less than 17% Zn in aqueous solutions. The calcium phosphate crystallinility decreases with the Zn concentration increase. The morphological changes with Zn substitution in HA were investigated by TEM. Lattice parameters of the apatitic samples were determined by XRD Rietveld refinement method. A computational study using ab initio generalized gradient approximation density functional theory was performed on Zn-substituted HA. Comparison of the experimental and computer simulation results provides our insights of Zn substitution in apatite structure.