Silver doped resorbable tricalcium phosphate scaffolds for bone graft applications

Bone graft procedures, in particular maxillofacial repair, account for half of the orthopedic procedures done in the US each year. Infection is a major issue in surgery, and should be of primary concern when engineering biomaterials. Silver is of renewed importance today, as it has the ability to potentiate antibiotics against resistant bacterial strains. In order to reduce long term infection risks, it is necessary for the scaffold to maintain a silver ion release for the length of the healing process. In this study, silver doped porous β-tricalcium phosphate (β-TCP) scaffolds were engineered using liquid porogen based method with the goal of meeting these requirements. Silver was added to the β-TCP at three different dopant levels: 0.5 wt% Ag2O, 1 wt% Ag2O and 2 wt% Ag2O. Immersion in pH 5 acetate buffer over a 60 day period resulted in a total cumulative ion release between 32 and 54 μM for dense control scaffolds, and between 80 and 90 μM for porous scaffolds. Porosity increased the dissolution rate of the scaffolds by a factor of 2. Human osteoblast cell lines were grown on the scaffolds to measure cytotoxicity and cell proliferation. Porosity increased osteoconduction by doubling the cell growth, and there was no significant cytotoxic effect even for the 2 wt% Ag2O, as cells were observed on all the samples. Our results showed that silver can be released over a long period without compromising the biocompatibility of the scaffolds.