Electrophoretic deposition of cellulose nanofibers in aqueous suspensions

Cellulose is one of the most abundant organic polymers in nature and a promising biomass. Since cellulose nanofibers (CNF) have attractive features such as a low thermal expansion coefficient, a high elastic modulus, high mechanical strength, and high eco-friendliness, CNFs are envisaged to be applied for biomaterials, tissue engineering scaffolds, filtration media, and reinforcement in nanocomposites. In this study, in order to develop a coating technology with nanofibers for biomedical applications, CNFs in aqueous suspensions were deposited on titanium and aluminum substrates by an electrophoretic deposition (EPD) technique. CNFs used were obtained from Sugino Machine Ltd. (Japan). Aqueous suspensions of the CNFs were prepared using a wet pulverizing and dispersing device. The obtained 0.2wt% aqueous suspensions of the CNFs were stable and not observed the aggregation of the nanofibers. EPD was conducted in a two-electrode system, where titanium or aluminum sheets were used as anode and a platinum sheet as cathode. The constant voltages of 10-30 V were applied to the system for 10-60 seconds. After the process, it was observed that the CNFs were successfully deposited on the anodes. The deposition amount of CNFs on either anode increased linearly with an increase of the applied time at the constant voltage of 20 V. Moreover, the amount also increased as a function of the applied voltages between 10 to 30 V at the constant applied time of 30 seconds. These results indicated that negatively charged CNFs in the aqueous suspension moved to the anodes by the electrophoresis. The adhesiveness of the deposited CNFs was superior on the aluminum anode compared with the titanium anode, indicating that the interaction between them depended on the kind of metal. In conclusion, EPD of the CNFs paves the way for the development of a coating technology with nanofibers for biomedical applications

Solid-state nuclear magnetic resonance study of setting mechanism of beta-tricalcium phosphate-inositol phosphate composite cements

Solid-state nuclear magnetic resonance (NMR) spectroscopy is a technique, which can be used to provide insight into the chemical structure of non-crystalline and crystalline materials. Hence, the present study aimed to elucidate the setting mechanism of CPC, which was fabricated using beta -tricalcium phosphate (beta -TCP)-inositol phosphate (IP6) composite powder using NMR In addition, the effect of IP6 on the local chemical structure of the beta -TCP-IP6 composite powder and its hardened cement would also be investigated. The H-1 -> P-31 heteronuclear correlation NMR spectrum revealed that an amorphous hydrated layer, along with small amount of hydroxyapatite (HA) was formed on the surface of beta -TCP during the ball-milling process. Results demonstrated that the IP6 in the hydrated layer on the surface of beta -TCP inhibited the formation of HA. Moreover, the setting reaction of the cement was mainly triggered by the dissolution of the amorphous hydrated layer on beta -TCP surface, and subsequent precipitation, followed by the inter-entanglement between the HA crystals on the beta -TCP

Preparation of chitosan-hydroxyapatite composite mono-fiber using coagulation method and their mechanical properties

Autograft has been carried out for anterior cruciate ligament (ACL) reconstruction surgery. However, it has negative aspect because patients lose their healthy ligaments from other part. We focus on a chitosan-hydroxyapatite (HAp) composite fiber as a scaffold of ligament regeneration. Chitosan- HAp composite fiber was made by using coagulation method. Chitosan-NaH2PO4 solution was coagulated with coagulation bath including calcium ion to get the mono-fiber and then treated with sodium hydroxide solution to form HAp in fiber matrix. The mechanical property of the fiber was improved by the stretching of the wet one because of the orientation of chitosan molecule and the interaction between chitosan and HAp. Maximum stress was improved with increasing of sodium dihydrogen phosphate until 0.03 M. The swelling ratio of the fiber was inhibited by composited with HAp. Additionally, bone-bonding ability was confirmed by SBF soaking tests

Anisotropic coating of a-plane oriented hydroxyapatite via a drop-on-demand micro-dispensing technique

10.1080/10667857.2018.1469261Materials Technology3511-12713-71

Effects of Adding Polysaccharides and Citric Acid into Sodium Dihydrogen Phosphate Mixing Solution on the Material Properties of Gelatin-Hybridized Calcium-Phosphate Cement

We have succeeded in improving the material properties of a chelate-setting calcium-phosphate cement (CPC), which is composed of hydroxyapatite (HAp) the surface of which has been modified with inositol hexaphosphate (IP6) by adding α-tricalcium phosphate (α-TCP) powder. In order to create a novel chelate-setting CPC with sufficient bioresorbability, gelatin particles were added into the IP6-HAp/α-TCP cement system to modify the material properties. The effects of adding polysaccharides (chitosan, chondroitin sulfate, and sodium alginate) into the sodium dihydrogen phosphate mixing solution on the material properties of the gelatin-hybridized CPC were evaluated. The results of mechanical testing revealed that chondroitin sulfate would be the most suitable for fabricating the hybridized CPC with higher compressive strength. Moreover, further addition of an appropriate amount of citric acid could improve the anti-washout capability of the cement paste. In summary, a gelatin-hybridized IP6-HAp/α-TCP cement system prepared with a mixing solution containing chondroitin sulfate and citric acid is expected to be a beneficial CPC, with sufficient bioresorbability and material properties

Fabrication of Novel Biodegradable α-Tricalcium Phosphate Cement Set by Chelating Capability of Inositol Phosphate and Its Biocompatibility

Biodegradable α-tricalcium phosphate (α-TCP) cement based on the chelate-setting mechanism of inositol phosphate (IP6) was developed. This paper examined the effect of the milling time of α-TCP powder on the material properties of the cement. In addition, biocompatibility of the result cement in vitro using osteoblasts and in vivo using rabbit models will be studied as well. The α-TCP powders were ballmilled using ZrO2 beads in pure water for various durations up to 270 minutes, with a single-phase α-TCP obtained at ballmilling for 120 minutes. The resulting cement was mostly composed of α-TCP phase, and the compressive strength of the cement was 8.5±1.1 MPa, which suggested that the cements set with keeping the crystallite phase of starting cement powder. The cell-culture test indicated that the resulting cements were biocompatible materials. In vivo studies showed that the newly formed bones increased with milling time at a slight distance from the cement specimens and grew mature at 24 weeks, and the surface of the cement was resorbed by tartrate-resistant acid phosphatase-(TRAP-)positive osteoclast-like cells until 24 weeks of implantation. The present α-TCP cement is promising for application as a novel paste-like artificial bone with biodegradability and osteoconductivity