Non-covalent surface engineering of an alloplastic polymeric bone graft material for controlled protein release

Alloplastic materials, derived from poly(methylmethacrylate), such Bioplant-HTR, are a promising alternative to autologous bone in implant-dentistry and maxillofacial reconstruction. The clinical utility and outcomes using alloplasts such as HTR can be enhanced through the incorporation and release of proteins and growth factors. A simple, water-based process to surface engineer alloplast material to bear proteins has been developed. In this non-covalent process, the protein of choice is formulated into granules using gelatin-wet granulation and immobilized on the HTR alloplast surface, using water-soluble polymeric binders such as poly(vinyl alcohol) and Pluronics. The utility of this process has been verified using bovine serum albumin and horseradish peroxidase as model proteins. The process is capable of rendering these proteins on HTR surface in a reproducible manner, with formulated protein:HTR ratios less than 1:1 favoring more uniform surface coatings. By varying the ratio of the granulated protein to the HTR, surface protein concentration as high as 30 μg/mg of HTR particle can be achieved. By incorporating the protein-modified HTR particles with photocurable polymeric matrices and varying its hydrophobicity, sustained release of active HRP for at least 30 days was observed, with cumulative release ranging from 7–35% of loaded protein, depending on the protein:HTR ratio and the polymeric binder. The integrity of the released protein was also verified using SDS-PAGE gel and enzymatic assay. The simplicity of the surface modification strategy may make this suitable for ceramic and metal substrates as well.