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At least 19 recordsLinked to original sources

PubMed2004

Synthesis of poly(methyl methacrylate) nanocomposites via emulsion polymerization using a zwitterionic surfactant.

The synthesis of nanocomposites via emulsion polymerization was investigated using methyl methacrylate (MMA) monomer, 10 wt % montmorillonite (MMT) clay, and a zwitterionic surfactant octadecyl dimethyl betaine (C18DMB). The particle size of the diluted polymer emulsion was about 550 nm, as determined by light scattering, while the sample without clay had a diameter of about 350 nm. The increase in the droplet size suggests that clay was present in the emulsion droplets. X-ray diffraction indicated no peak in the nanocomposites. Transmission electron microscopy showed that emulsion polymerization of MMA in the presence of C18DMB and MMT formed partially exfoliated nanocomposites. Differential scanning calorimetry showed an increase of 18 degrees C in the glass transition temperature (Tg) of the nanocomposites. A dynamic mechanical thermal analyzer also verified a similar Tg increase, 16 degrees C, for the partially exfoliated nanocomposites over poly(methyl methacrylate) (PMMA). Thermogravimetric analysis indicated a 37 degrees C increase in the decomposition temperature for a 20 wt % loss. A PMMA nanocomposite with 10 wt % C18DMB-MMT was also synthesized via in situ polymerization. This nanocomposite was intercalated and had a Tg 10 degrees lower than the emulsion nanocomposite. The storage modulus of the partially exfoliated emulsion nanocomposite was superior to the intercalated structure at higher temperatures and to the pure polymer. The rubbery plateau modulus was over 30 times higher for the emulsion product versus pure PMMA. The emulsion technique produced nanocomposites of the highest molecular weight with a bimodal distribution. This reinstates that exfoliated structures have enhanced thermal and mechanical properties over intercalated hybrids.

Journal Article↗

PubMed2006

Water absorption characteristics of novel Cu/LDPE nanocomposite for use in intrauterine devices.

Intrauterine devices (IUDs), especially the copper-containing IUDs (Cu-IUDs), are one of the worldwide used forms for birth control, owing to their advantages of long-lasting and high efficacy, economy, safety, and reversibility. However, it is not perfect for the existing Cu-IUDs; some shortcomings related to its side effects have not been overcome yet. For this reason, a new Cu-IUDs material, the copper/low-density polyethylene (Cu/LDPE) nanocomposite, has been developed in our research team. The structure and water uptake characteristics of this new Cu-IUDs material have been investigated by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and gravimetric analysis in this paper. The results of XRD, SEM, EDS, and FT-IR show three important outcomes associated with the structure of the nanocomposite. First, the nanocomposite is hybrid of the polymer and the copper nanoparticles (nano-Cu). Second, porosities, nano-Cu aggregates, and primary alcohol (R--CH(2)--OH) are existed in the nanocomposite. Third, the nano-Cu aggregates are distributed uniformly in the polymer matrix in general. The results of Gravimetric analysis, which associated with the water uptake characteristics of the nanocomposite, exhibit that the water absorption behavior of the nanocomposite obeys the classical diffusion theory very well, the water uptake of the nanocomposite increases with the increasing of the nano-Cu loading, and that the water uptake ability of the nanocomposite with 15.0 wt % nano-Cu (50 nm in diameter) is about 150 times larger than that of the base resin and about 45 times higher than that of the Cu/LDPE microcomposite with 15.0 wt % copper microparticles (5 microm in diameter). These water uptake characteristics are mainly attributed to the structure of the Cu/LDPE composites and the size effect of the nano-Cu.

Absorption↗

PubMed2002

Effects of various thiol molecules added on morphology of dendrimer-gold nanocomposites.

Interactions between poly(amidoamine) dendrimer (PAMAM)-gold nanocomposites and alkanethiols and between the former nanocomposites and thiol-modified poly(amidoamine) dendrons in ethyl acetate were investigated by adding alkanethiols, such as 1-propanethiol and 1,3-propanedithiol, and thiol-modified poly(amidoamine) dendrons, generations 0.5 and 2.5 (G0.5-SH and G2.5-SH). The PAMAM dendrimers with surface methyl ester groups used were generations 1.5 and 5.5 (G1.5 and G5.5). The mean particle sizes of PAMAM-gold nanocomposites were about 2.1 for G1.5 and 2.4 nm for G5.5. In both nanocomposite systems where 1-propanethiol and 1,3-propanedithiol were added, the mean particle size was about 4 nm, twice that of the systems where these thiols were not added. Increasing the addition of 1,3-propanedithiol made the average particle size smaller for both nanocomposites systems. To compare with alkanethiol, thiol-modified poly(amidoamine) dendron with a highly branched structure on one side was synthesized. Using G2.5-SH as a protective agent, dendron-gold nanocomposites with mean diameters of 3 to 4 nm were obtained. The difference in particle size was seen only when the combination of PAMAM-gold nanocomposites and thiol-modified dendron was less sterically dense, modified dendron (G0.5-SH). The mechanisms for morphology changes in the dendrimer-gold nanocomposites by the addition of these thiols are discussed.

Journal Article↗

PubMed2005

Stimulation of osteoblast responses to biomimetic nanocomposites of gelatin-hydroxyapatite for tissue engineering scaffolds.

Collagen-derived gelatin/hydroxyapatite (HA) nanocomposites were biomimetically synthesized for hard tissue engineering scaffold. In vitro osteoblastic cellular responses to the nanocomposites were assessed in comparison with those conventionally mixed gelatin-HA composites. A three-dimensional culture method involving floating cells in a culture medium was introduced to assist in the initial attachment of the cells to the scaffolds, and the proliferation and differentiation behaviors of the cells were examined. The osteoblastic MG63 cells attached to the nanocomposites to a significantly higher degree and subsequently proliferated more. The alkaline phosphatase (ALP) activity and osteocalcin produced by the cells were significantly higher on the nanocomposite scaffolds than on the conventional composite scaffolds. These improved cellular responses on the nanocomposites are considered to result from the increased ionic release and serum protein adsorption on the nanocomposites, which was derived from the different structural and morphological characteristics, i.e., the nanocomposite scaffolds retained less-crystallized and smaller-sized apatite crystals and a more well-developed pore configuration than the conventional ones. Based on these findings, the biomimetically synthesized nanocomposite scaffolds are believed to be potentially useful in hard tissue regeneration and tissue engineering fields.

Alkaline Phosphatase↗

PubMed2006

PEI-alginate nanocomposites as efficient in vitro gene transfection agents.

The positive charge on PEI was partially shielded by forming ionic nanocomposites with a polysaccharide, alginic acid, in aqueous solution, bypassing tedious chemical synthesis. The content of alginic acid was varied systematically to obtain a series of nanocomposites. The nanocomposites were first characterized by assessing the surface charge (zeta potential), size (DLS) and morphology (AFM) followed by evaluation for their DNA interaction ability, cytotoxicity and transfection efficiency on various cell lines. The transfection efficiency of PEI-alginate (6.26%) nanocomposites improved dramatically (2-16-fold over native PEI) in all the cell lines studied. However, a decrease in transfection efficiency was observed on deviating from this optimal concentration of alginic acid in nanocomposites. Cytotoxicity of PEI-alginate/DNA complexes was nearly abolished on increasing the concentration of alginic acid in nanocomposites. PEI-alginate (6.26%) nanocomposites also delivered SiRNAs efficiently into mammalian cells, resulting in 80% suppression of GFP expression. The cellular uptake and endosomal escape of PEI-alginate nanocomposites and PEI were found to follow a similar route when transfection was carried out in presence of chloroquine, bafilomycin A1, cytochalasin B and methyl-beta-cyclodextrin. The results demonstrate a versatile vector that can be used for efficient cytoplasmic delivery of a broad range of nucleic acids.

Alginates↗

PubMed2003

Helical conformational specificity of enzymatically synthesized water-soluble conducting polyaniline nanocomposites.

A novel template guided enzymatic approach has been developed to synthesize optically active conducting polyaniline (PANI) nanocomposites in the presence of H2O2 as an oxidant, using (+) and (-) 10-camphorsulfonic acid (CSA) as a dopant and chiral inductor. The formation of chiral polyaniline in the nanocomposites was confirmed by circular dichroism (CD). Interestingly, the CD spectra of nanocomposites formed either with (+) or with (-) CSA show the enzyme itself plays a critical role in controlling the stereospecificity of the polyaniline (PANI) in the nanocomposite. The enzyme used for the polymerization of aniline in the nanocomposite was horseradish peroxidase (HRP). It was shown that this enzyme prefers a specific helical conformation, regardless of whether induced chirality in the complex CSA-aniline is from (+) or (-) CSA. UV-vis spectra show that the polyaniline is in the conducting form, and transmission electron micrographs (TEM) show that the nanocomposites are dispersed nicely with particle size dimensions in the range of 20-50 nm. Electron diffraction patterns of these chiral polymer nanocomposites suggest that these nanocomposites are in both crystalline and amorphous states.

Acrylic Resins↗

PubMed2004

Preparation of PAMAM- and PPI-metal (silver, platinum, and palladium) nanocomposites and their catalytic activities for reduction of 4-nitrophenol.

Dendrimer-metal (silver, platinum, and palladium) nanocomposites are prepared in aqueous solutions containing poly(amidoamine) (PAMAM) dendrimers with surface amino groups (generations 3, 4, and 5) or poly(propyleneimine) (PPI) dendrimers with surface amino groups (generations 2, 3, and 4). The particle sizes of the metal nanoparticles obtained are almost independent of the generation as well as the concentration of the dendrimer for both the PAMAM and the PPI dendrimers; the average sizes of silver, platinum, and palladium nanoparticles are 5.6-7.5, 1.2-1.6, and 1.6-2.0 nm, respectively. It is suggested that the dendrimer-metal nanocomposites are formed by adsorbing the dendrimers on the metal nanoparticles. Studies of the reduction reaction of 4-nitrophenol by these nanocomposites show that the rate constants are very similar between PAMAM and PPI dendrimer-silver nanocomposites, whereas the rate constants for the PPI dendrimer-platinum and -palladium nanocomposites are greater than those for the corresponding PAMAM dendrimer nanocomposites. In addition, it is found that the rate constants for the reduction of 4-nitrophenol involving all the dendrimer-metal nanocomposites decrease with an increase in the dendrimer concentrations, and the catalytic activity of dendrimer-palladium nanocomposites is highest.

Catalysis↗

PubMed2005

Characterization of the nanomorphology of polymer-silica colloidal nanocomposites using electron spectroscopy imaging.

The internal nanomorphologies of two types of vinyl polymer-silica colloidal nanocomposites were assessed using electron spectroscopy imaging (ESI). This technique enables the spatial location and concentration of the ultrafine silica sol within the nanocomposite particles to be determined. The ESI data confirmed that the ultrafine silica sol was distributed uniformly throughout the poly(4-vinylpyridine)/silica nanocomposite particles, which is consistent with the "currant bun" morphology previously used to describe this system. In contrast, the polystyrene/silica particles had a pronounced "core-shell" morphology, with the silica sol forming a well-defined monolayer surrounding the nanocomposite cores. Thus these ESI results provide direct verification of the two types of nanocomposite morphologies that were previously only inferred on the basis of X-ray photoelectron spectroscopy and aqueous electrophoresis studies. Moreover, ESI also allows the unambiguous identification of a minor population of polystyrene/silica nanocomposite particles that are not encapsulated by silica shells. The existence of this second morphology was hitherto unsuspected, but it is understandable given the conditions employed to synthesize these nanocomposites. It appears that ESI is a powerful technique for the characterization of colloidal nanocomposite particles.

Letter↗

PubMed2006

Bioactive glass nanofiber-collagen nanocomposite as a novel bone regeneration matrix.

Nanoscale organized organic-inorganic nanocomposite systems have great potential in the development of biomaterials with advanced properties. Herein, we developed a novel nanocomposite biomaterial consisting of bioactive glass nanofiber (BGNF) and collagen reconstituted fibrous matrix for bone regenerative medicine. A sol-gel derived glass with a bioactive composition (58SiO(2). 38CaO.4P(2)O(5)) was electrospun to a nanoscale fiber with an average diameter of approximately 320 nm. The BGNF was subsequently hybridized with type I collagen, which is the main organic constituent of bone matrix. The BGNF and self-assembled collagen sol were combined in aqueous solution, and then crosslinked to produce a BGNF-collagen nanocomposite, in the form of either a thin membrane or a macroporous scaffold, by adopting appropriate processing conditions. The BGNF was observed to be distributed uniformly within the collagen reconstituted nanofibrous matrix. The nanocomposite matrices induced rapid formation of bone-like apatite minerals on their surfaces when incubated in a simulated body fluid, exhibiting excellent bioactivity in vitro. Osteoblastic cells showed favorable growth on the BGNF-collagen nanocomposite. In particular, the alkaline phosphatase activity of the cells on the nanocomposite was significantly higher than that on the collagen. This novel BGNF-collagen nanocomposite is believed to have significant potential in bone regeneration and tissue engineering applications.

Biocompatible Materials↗

PubMed1997

A Physicochemical Study of Polypyrrole-Silica Nanocomposites by Inverse Gas Chromatography

Three polypyrrole-silica nanocomposites were characterized by inverse gas chromatography (IGC) at 60 and 80degreesC using both linear and branched alkane probes. The IGC data for these materials were compared with those obtained for the ultrafine silica sol and polypyrrole (PPy) bulk powder reference materials. The London components of the surface energies (gammasd) of the nanocomposites were in the range 115-225 mJ m-2 at 60degreesC. These values are much higher than those obtained for either the polypyrrole powders or the colloidal silica sol, which suggests that the nanocomposites have significant microporosity. The gammasd values for the nanocomposites decrease in the order chloride-doped PPy > sulfate-doped PPy > tosylate-doped PPy, which is the same trend as that found for the heat of adsorption (DeltaHa) of a given n-alkane. DeltaHa values of the linear and branched alkanes are up to three times higher than the heats of vaporization, which confirms that the nanocomposites (and, to a lesser extent, the polypyrrole powders) have high adsorption capacities for these solutes. For a series of alkane isomers (e.g., C7H16 or C8H18), the difference between the DeltaHa values for the nanocomposites and the corresponding polypyrrole powders decreased as the degree of branching for these probes was increased. These observations suggest that the more sterically hindered probes are excluded from the microporous interior of the nanocomposites. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

PubMed2005

Low shrinkage light curable nanocomposite for dental restorative material.

OBJECTIVES: The aim of this study was to develop a low shrinkage visible light curable nanocomposite dental restorative material without sacrificing the other properties of conventional materials. This nanocomposite was developed by using an epoxy resin 3,4-epoxycyclohexylmethyl-(3,4-epoxy)cyclohexane carboxylate (ERL4221) matrix with 55% wt of 70-100 nm nanosilica fillers through ring-opening polymerization. GPS (gamma-glycidoxypropyl trimethoxysilane) was used to modify the surfaces of silica nanoparticles. RESULTS: The nanocomposite was shown to exhibit low polymerization shrinkage strain, which is only a quarter of currently used methacrylate-based composites. It also exhibited a low thermal expansion coefficient of 49.8 microm/m degrees C which is comparable to that of the methacrylate based composites (51.2 microm/m degrees C). The strong interfacial interactions between the resin and fillers at nanoscales were demonstrated by an observed high strength and high thermal stability of the nanocomposite. A microhardness of 62 KHN and a tensile strength of 47 MPa were reached. A high degree of conversion ( approximately 70%) can be obtained after less than 60 s of irradiation upon the nanocomposite. A transmission electron microscope (TEM) study of the nanocomposite showed no aggregation of fillers. Comparable results to the methacrylate based composites were obtained from the one day MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) cytotoxicity test. SIGNIFICANCE: The developed epoxy resin based nanocomposite demonstrated low shrinkage and high strength and is suitable for dental restorative material applications.

Coloring Agents↗

PubMed2006

The antithrombogenic potential of a polyhedral oligomeric silsesquioxane (POSS) nanocomposite.

We have developed a nanocomposite using a silica nanocomposite polyhedral oligomeric silsesquioxane (POSS) and poly(carbonate-urea)urethane (PCU) for potential use in cardiovascular bypass grafts and the microvascular component of artificial capillary beds. In this study, we sought to compare its antithrombogenicity to that of conventional polymers used in vascular bypass grafts so as to improve upon current patency rates, particularly in the microvascular setting. Using atomic force microscopy (AFM) and transmission electron microscopy (TEM), surface topography and composition were studied, respectively. The ability of the nanocomposite surface to repel both proteins and platelets in vitro was assessed using thromboelastography (TEG), fibrinogen ELISA assays, antifactor Xa assays, scanning electron microscopy (SEM), and platelet adsorption tests. TEG analysis showed a significant decrease in clot strength (one-way ANOVA, p < 0.001) and increase in clot lysis (one-way ANOVA, p < 0.0001) on the nanocomposite when compared to both poly(tetrafluoroethylene) (PTFE) and PCU. ELISA assays indicate lower adsorption of fibrinogen to the nanocomposite compared to PTFE (one-way ANOVA, p < 0.01). Interestingly, increasing the concentration of POSS nanocages within these polymers was shown to proportionately inhibit factor X activity. Platelet adsorption at 120 min was also lower compared to PTFE and PCU (two-way ANOVA, p < 0.05). SEM images showed a "speckled" morphologic pattern with Cooper grades I platelet adsorption morphology on the nanocomposite compared to PTFE with grade IV morphology. On the basis of these results, we concluded that POSS nanocomposites possess greater thromboresistance than PTFE and PCU, making it an ideal material for the construction of both bypass grafts and microvessels.

Adsorption↗

PubMed2006

Novel biobased nanocomposites from soybean oil and functionalized organoclay.

Novel biobased nanocomposites have been prepared by the cationic polymerization of conjugated soybean oil (CSOY) or conjugated LoSatSoy oil (CLS) with styrene (ST) and divinylbenzene (DVB), and a reactive organomodified montmorillonite (VMMT) clay as a reinforcing phase. This filler has been prepared by the cationic exchange of sodium montmorillonite with (4-vinylbenzyl)triethylammonium chloride in aqueous solution. The nanostructures of the nanocomposites have been determined by using wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM), respectively. The results from WAXD and TEM indicate that a heterogeneous structure consisting of intercalation and partial exfoliation or an intercalation structure exists in the nanocomposites, depending on the amount of VMMT in the polymer matrix. The thermal, mechanical, and organic vapor barrier properties of the nanocomposites have been evaluated by dynamic thermal analysis, thermogravimetric analysis, mechanical testing, and toluene absorption. A significant improvement is observed in the thermal stability, the dynamic bending storage modulus, the compressive modulus, the compressive strength, the compressive strain at failure, and the vapor barrier performance for the CSOY-- and CLS-based nanocomposites with 1-2 wt % VMMT loading, where some individual exfoliated silicate platelets occur. For example, the CLS-based nanocomposite with 1-2 wt % VMMT exhibits increases of 100-128%, 86-92%, and 5-7% in compressive modulus, compressive strength, and compressive strain at failure, respectively. CLS with higher unsaturation and reactivity affords nanocomposites with higher thermal stability and higher mechanical properties than CSOY.

Aluminum Silicates↗

PubMed2004

Synthesis of vinyl polymer-silica colloidal nanocomposites prepared using commercial alcoholic silica sols.

The surfactant-free synthesis of vinyl polymer-silica nanocomposite particles has been achieved in aqueous alcoholic media at ambient temperature in the absence of auxiliary comonomers. Styrene, methyl methacrylate, methyl acrylate, n-butyl acrylate, and 2-hydroxypropyl methacrylate were homopolymerized in turn in the presence of three commercially available ultrafine alcoholic silica sols. Stable colloidal dispersions with reasonably narrow size distributions were obtained, with silica contents of up to 58% by mass indicated by thermogravimetric analysis. Particle size distributions were assessed using both dynamic light scattering and disk centrifuge photosedimentometry. The former technique indicated that the particle size increased for the first 1-2 h at 25 degrees C and thereafter remained constant. Particle morphologies were studied using electron microscopy. Most of the colloidal nanocomposites comprised approximately spherical particles with relatively narrow size distributions, but in some cases more polydisperse or nonspherical particles were obtained. Selected acrylate-based nanocomposites were examined in terms of their film formation behavior. Scanning electron microscopy studies indicated relatively smooth films were obtained on drying at 20 degrees C, with complete loss of the original particle morphology. The optical clarity of solution-cast 10 microm nanocomposite films was assessed using visible absorption spectrophotometry, with 93-98% transmission being obtained from 400 to 800 nm; the effect of long-term immersion of such films in aqueous solutions was also examined. X-ray photoelectron spectroscopy studies indicated that the surface compositions of these nanocomposite particles are invariably silica-rich, which is consistent with their long-term colloidal stability and also with aqueous electrophoresis measurements. FT-IR studies suggested that in the case of the poly(methyl methacrylate)-silica nanocomposite particles, the carbonyl ester groups in the polymer are hydrogen-bonded to the surface silanol groups. According to differential scanning calorimetry studies, the glass transition temperatures of several poly(methyl methacrylate)-silica and polystyrene-silica nanocomposites can be either higher or lower than those of the corresponding homopolymers, depending on the nature of the silica sol.

Journal Article↗

PubMed2007

Cupric ion release controlled by copper/low-density polyethylene nanocomposite in simulated uterine solution.

The Cu2+ release rate of novel copper/low-density polyethylene composites as an intrauterine device material in the simulated uterine solution was investigated for 280 days. The corrosion products of these composites were identified by the X-ray diffraction method. The distributions of the copper phase and the cuprous oxide phase at different corrosion depths in the composites were measured by the internal standard method. For comparison, copper particles of two sizes were embedded in a polyethylene matrix to form composites. The average copper particle diameter of the nanocomposite was 30 nm, while that of microcomposite was 52 microm. Mechanism of Cu2+ release controlled by the nanocomposite revealed that many clusters composed of copper nanoparticles, which were observed by the field emission scanning electron microscopy in the nanocomposite, led to the formation of large amounts of Cu2O and consequently facilitated the Cu2+ steady release. A scanning electron microscope with energy dispersive X-ray microanalysis mapping technique (SEM/EDX) was employed to measure the corrosion depth and to calculate the life span of the nanocomposite. The result that the nanocomposite displayed a near zero-order release after a month of incubation indicated that the Cu2+ release behavior controlled by nanocomposite was remarkably superior to that by microcomposite.

Biocompatible Materials↗

PubMed2006

Biocompatibility of poly(ether)urethane-gold nanocomposites.

We have prepared the nanocomposites of a polyether-type waterborne polyurethane (PU) incorporated with different amounts (17.4-174 ppm) of gold (Au) nanoparticles ( approximately 5 nm). The nanocomposite containing a certain amount (43.5 ppm) of gold was previously demonstrated to possess the optimal thermal and mechanical properties, as well as much reduced foreign body reactions in subcutaneous rats. In this study, the surface morphology, biocompatibility, oxidative degradation, and free radical scavenging ability of the nanocomposites were characterized in vitro. The nanocomposite at 43.5 ppm of gold ("PU-Au 43.5 ppm") exhibited different surface morphology confirmed by the atomic force microscope. PU-Au 43.5 ppm also showed enhanced cellular proliferation, reduced platelet and monocyte activation, and much less bacterial adhesion, relative to PU alone or nanocomposites at the other Au contents, in general. This better biocompatibility was associated with the surface morphological change in the presence of Au. The oxidative degradation in PU-Au 43.5 ppm was also inhibited. The increased oxidative stability corresponded to the greater free radical scavenging ability of the nanocomposites.

Biocompatible Materials↗

PubMed2005

Porous scaffolds of gelatin-hydroxyapatite nanocomposites obtained by biomimetic approach: characterization and antibiotic drug release.

Gelatin-hydroxyapatite (HA) nanocomposite porous scaffolds were fabricated biomimetically, and their feasibility as a drug-delivery carrier for tissue-regeneration and wound-healing treatments was addressed. The composite sols were prepared by the precipitation of HA up to 30 wt % within a gelatin solution with the use of calcium and phosphate precursors, and the porous scaffold was obtained by casting the sols and further freeze drying. The obtained bodies were crosslinked with carbodiimide derivatives to retain chemical and thermal integrity. The apatite precipitates were observed to be a poorly crystallized carbonate-substituted HA. The nanocomposite scaffolds had porosities of approximately 89-92% and exhibited a bimodal pore distribution, that is, the macropores (approximately 300-500 microm) of the framework structure, and micropores (approximately 0.5-1 microm) formed on the framework surface. Transmission electron microscopy (TEM) observation revealed the precipitation of highly elongated HA nanocrystals on the gelatin network. The well-developed porous structure and organized nanocomposite configurations were in marked contrast to the directly mixed gelatin-HA powder conventional composites. For drug-release tests, tetracycline, an antibiotic drug, was entrapped within the scaffold, and the drug-release profile was examined with processing parameters, such as HA amount in gelatin, crosslinking degree, and initial drug addition. The drug entrapment decreased with increasing HA amount, but increased with increasing crosslinking degree and initial drug addition. The crosslinking of the gelatin was the prerequisite to sustaining and controlling the drug releases. Compared to pure gelatin, the gelatin-HA nanocomposites had lower drug releases, because of their lower water uptake and degradation. All the nanocomposite scaffolds released drugs in proportion to the initial drug addition, suggesting their capacity to deliver drugs in a controlled manner. Based on the findings of the well-developed morphological feature and controlled drug-release profile, the gelatin-HA nanocomposite porous scaffolds are suggested to be potentially useful for hard-tissue regeneration.

Anti-Bacterial Agents↗

PubMed2004

Preparation and characterization of metal-chitosan nanocomposites.

Various metal-chitosan nanocomposites were synthesized, including silver (Ag), gold (Au), platinum (Pt), and palladium (Pd) in aqueous solutions. Metal nanoparticles were formed by reduction of corresponding metal salts with NaBH4 in the presence of chitosan. And chitosan molecules adsorbing onto the surface of as-prepared metal nanoparticles formed the corresponding metal-chitosan nanocomposites. Transmission electron microscopy (TEM) images and UV-vis spectra of the nanocomposites revealed the presence of metal nanoparticles. Comparison of all the resulting particles size, it shows that silver nanoparticles are much larger than others (Au, Pt and Pd). In addition, the difference in particles size leads to develop different morphologies in the films cast from prepared metal-chitosan nanocomposites. Polarized optical microscopy (POM) images show a batonet-like structure for Ag-chitosan nanocomposites film, while for the films cast from other metal (Au, Pt, and Pd)-chitosan nanocomposites, some branched-like structures with a few differences among them were observed under POM observation.

Biocompatible Materials↗