Vacuum-assisted infiltration of chitosan or polycaprolactone as a structural reinforcement for sintered cancellous bovine bone graft

Abstract

Sintered cancellous bovine bone (SCBB) offers numerous advantages as a bone graft substitute material; however, its mechanical properties require improvement. In this study, SCBB was infiltrated with ε-polycaprolactone (PCL) or chitosan/monetite to improve mechanical properties while retaining valuable SCBB structure. Organic infiltrating solutions consisted of (i) chitosan and monetite (CaHPO₄) dissolved in hydrochloric acid; (ii) chitosan, monetite (CaHPO₄), and genipin dissolved in hydrochloric acid; or (iii) PCL polymer dissolved in tetrahydrofuran (THF). Porous SCBB materials were infiltrated with one of the three solutions using vacuum-assisted infiltration. Chitosan and CaHPO₄ were immobilized in the SCBB structure by reprecipitation following a pH increase in an ammonia atmosphere. Genipin was used in one sample group to immobilize chitosan via crosslinking. PCL was immobilized by evaporating the THF carrier solvent. Mechanical compression testing showed an improvement in ultimate stress for the SCBB with chitosan/CaHPO₄ infiltrates, whereas PCL samples showed an increase in modulus. All SCBB samples were found to demonstrate favorable in vitro biocompatibility when subjected to L929 mouse fibroblast cells but required a vigorous washing regime to eradicate toxic ammonia residue. In conclusion, infiltration of SCBB with a polymeric or organic/mineral composite matrix positively modifies SCBB mechanical properties in favor of bone grafting applications.