We prepared DNA/cationic polylysine complexes, and examined their biodegradation behavior and histopathological responses for use as a scaffold material for bone regeneration. For the cationic polylysine, two types of isomeric polylysine, D-polylysine (DNA/D-lysine complex) and L-polylysine (DNA/L-lysine complex) were used. A water-insoluble white powder of the complexes with a porous structure was obtained. The yields of the DNA/D-lysine complexes and DNA/L-lysine complexes were 63.8% and 64.5%, respectively. There were mild tissue responses after a disk comprising either complex was implanted into the subcutaneous tissue of rats. The biodegradation rate of the DNA/L-lysine complexes was greater than that of the DNA/D-lysine complexes. This study suggested that DNA/cationic polylysine complexes have the potential for controlled biodegradation using satisfactory combinations of isomeric polylysine.

The effect of UV-photofunctionalization on the osteoconductivity of titanium implanted under osteoporotic conditions using the SAM-P/6 senile osteoporosis mouse model was evaluated. UV-photofunctionalized titanium was prepared by treatment of the aged titanium surfaces with UV irradiation. Titanium implants were fixed and subjected to push out testing. The morphology of new bone around the titanium plate was evaluated. Cell quantity, ALP activity and calcification of each titanium disc ware determined. The UV-photofunctionalized implants showed significantly higher maximum push out value (N) compared with the aged-surface controls. Bone contact ratio, cell quantity, ALP activity and calcification ware significantly higher for the UV-photofunctionalized titanium compared with the aged-surface controls. We established a system to study implant placement in this senile osteoporosis model, and conducted biomechanical, histological, and cytological investigations. Based on these investigations, we propose that UV-photofunctionalization enhanced osteoconductivity in osteoporotic conditions in the SAM-P/6 model of senile osteoporosis used in this study.