Papers by Author: Yu Sogo

Abstract: FGF-2-apatite and FGF-2-zinc-apatite composite layers were formed on commercially available anodically oxidized Ti external fixation rods using FGF-2-and ZnCl₂-containing supersaturated calcium phosphate solutions. The FGF-2-zinc-apatite composite layers precipitated on the Ti external fixation rods significantly enhanced proliferation of fibroblastic NIH3T3 and osteoblastic MC3T3-E1 cells in vitro.

Abstract: An apatite-pathogen-associated molecular patterns (PAMPs) adjuvant was prepared by coprecipitation of apatite and PAMPs using a supersaturated calcium phosphate solution supplemented with PAMPs. In this study, we used a hydrothermal extract of human tubercle bacillus (HTB) as PAMPs. The effects of coprecipitation conditions on immunogenic activity were studied. The adjuvants prepared using extract of at 10 and 20 μg/mL showed higher in vitro immunogenic activity than that at 2 μg/mL. The adjuvants prepared under stir at speed of 300 rpm showed better in vitro immunogenic activity than those under still. The adjuvants prepared using 10 μg/mL of extract of HTB under stir at speed of 300 rpm may be promising for cancer immune therapy.

Abstract: Calcium phosphate (CaP) coating is an effective technique for surface functionalization of biomaterials. The objective of our research is to prepare calcium phosphate (CaP) coatings on a hydroxyapatite/collagen (HAp/Col) nanocomposite and subsequently provide it with gene delivery function through the immobilization of DNA in the coating. We have specifically selected the HAp/Col nanocomposite since it has the high potential as bone substitutes due to its similar composition, nanostructure, and biological properties to those of human bone. CaP coatings consisting of different sized particles were prepared on the HAp/Col nanocomposite membrane by immersing it in supersaturaterd CaP solutions (so-called RKM solutions) with the varied Ca and P concentration levels. We immobilized DNA in the CaP coatings together with lipid and fibronectin by supplementing DNA, lipid, and fibronectin to the RKM solutions (DLF-RKM solutions). Gene transfer capability of the resulting HAp/Col nanocomposite membrane was improved with decreasing concentration level of the DLF-RKM solution. It was confirmed that the present CaP coating technique was effective in providing the HAp/Col nanocomposite membrane with gene transfer capability and that the Ca and P concentration level of the DLF-RKM solution was a controlling factor affecting the gene transfer efficiency.

Abstract: Hydroxyapatite/collagen (HAp/Col) nanocomposites with bone-like self-organized nanostructure show excellent bioactivity in vivo. However, they show quite high absorbability for cationic ions and lower culture medium ionic concentrations which adversely affects bone cell proliferation and osteogenic differentiation in in vitro cell culture condition. To address this limitation, in this study we have supplemented Ca²⁺ and Mg²⁺ ions to the HAp/Col nanocomposite membrane sample prior to cell culture to improve it’s in vitro biological properties. The HAp/Col nanocomposite membrane samples were fabricated by the simultaneous titration method using Ca(OH)₂, type-I atelocollagen and H₃PO₄ as starting precursor materials. Prior to in vitro cell culture experiments, the HAp/Col samples were pretreated with Ca²⁺ and/or Mg²⁺ ions by immersing in 10 ml of 20 mM CaCl₂ solution, 20 mM MgCl₂ solution, or a solution containing 20 mM CaCl₂ and 20 mM MgCl₂ for 7 days. In vitro bone cell-material interactions on the pretreated and untreated HAp/Col samples were studied by culturing MC3T3-E1 cells up to 7 days. Enhanced bone cell proliferation was found on all the pretreated HAp/col samples as confirmed by the CCK-8 assay. Interestingly, the HAp/Col samples pretreated with both Ca²⁺ and Mg²⁺ ions showed the maximum viable bone cell density.

Abstract: A composite of co-polymer of lactic and glycolic acids (PLGA) loaded with gatifloxacine (GFLX), an antibiotics, and a β-tricalcium phosphate (βTCP) porous ceramic body was prepared by a solvent-free process in which no toxic solvent was used. The GFLX-loaded PLGA released GFLX for 8 weeks in Hanks’ balanced solution. The inhibitory zone diameter (26.25±0.95 mm) for GFLX-containing PLGA disk against S. milleri was significantly larger than 18 mm, and comparable to that (24.88±1.6 mm) for the KB paper disk containing 5 μg of GFLX/disk. This means that the GFLX-containing PLGA has the clinical efficacy. The molten PLGA containing GFLX was successfully loaded in the pores and on the surface of the porous βTCP ceramic at 120 °C at a reduced pressure of 0.02 MPa. The composite of GFLX-loaded porous βTCP ceramic would be promising for treating osteomyelitis.

Abstract: A composite layer of fibroblast growth factor-2 (FGF-2) and low-crystalline apatite was formed on an ethylene-vinyl alcohol copolymer specimen using two types of aqueous calcium phosphate solutions supplemented with 10 !g·mL-1 FGF-2; one is a CP solution that is prepared by dissolving chemical reagents into ultrapure water and the other is an RKB solution that can be prepared by mixing clinically approved infusion fluids. In both solutions, a sufficient amount of FGF-2 for new skin tissue formation (1 !g·cm-2) was immobilized on the specimen surface.

Abstract: A FGF-2-apatite composite layer (FGF-AP layer) was formed on the surface of Ti screws in a supersaturated calcium phosphate solution supplemented with FGF-2. By an in vitro study using fibroblastic NIH3T3 cells, it was confirmed that FGF-2 was immobilized in the layer without complete denaturation although the composite layer was formed at 37°C. When Ti screws with the FGF-AP layer were percutaneously implanted in the proximal tibial metaphysis of 16 rabbits, no osteomyelitis was observed in any rabbits although a FGF-2-free AP layer allowed osteomyelitis in some cases in our previous study. These results suggest that a FGF-AP layer formed on Ti screws is useful for resisting bacterial infection during external fixations.

Abstract: Highly disgregated dicalcium phosphate anhydrate (DCP) nanoparticles 240-367 nm in diameter were synthesized by a reaction between calcium carbonate and phosphoric acid. When the DCP nanoparticles were immersed in a supersaturated calcium phosphate solution containing bovine serum albumin (BSA) and ethanol, BSA/DCP nano-composite particles were synthesized through the coprecipitation of BSA on the DCP nanoparticles. BSA was firmly immobilized on the BSA/DCP nano-composite particles. The results of this study suggest that DCP nanoparticles appear to be useful as a drug delivery vehicle.

Abstract: An ethylene-vinyl alcohol copolymer (EVOH) film with a laminin–apatite composite layer on its surface showed improved adhesion and compatibility to living epithelial tissue compared to untreated EVOH film. This result can be attributed to the good biocompatibility of apatite and the cell-adhesion activity of the laminin on the EVOH surface. This composite material, consisting of laminin, apatite, and EVOH, is considered a promising material for skin terminals to prevent epidermal downgrowth.