Long‐term tissue integration of porous biopolymers as a material platform for metabolic biosensor

Abstract

Implantable devices induce inflammation and collagen formation, which perturb the metabolic microenvironment and reduce mass transport. This study tested whether novel porous biomaterials improve tissue integration and normalize the glucose gradients. Five materials 700μm thick were implanted into rat dorsal subcutis: cotton cloth, solid silicone elastomer, solid polyHEMA, polyHEMA with 40μm pores, polyHEMA with 80μm pores. Specimens with surrounding tissue were explanted and frozen in liquid nitrogen 1, 4, and 8 weeks after implant. Serial sections were quantified for microvascular density (CD31 antibody), collagen (Masson's trichrome), immune cells (nuclear counterstain) and spatial glucose concentration (bioluminescence). Preliminary results indicate neovascularization of 80μm pore size polyHEMA after 1 week, and complete microvascular infiltration of the 80μm matrix after 4 weeks of implantation. Glucose concentrations in the porous polyHEMA after 4 weeks were comparable to those in the surrounding tissue. At that time, a moderate collagen deposition was observed in the 40 and 80 μm porous polyHEMA. While dense vascularization was also observed with cotton, it had the highest immune involvement. These preliminary findings suggest tissue integrates into porous polyHEMA matrix with a high microvessel density after 4 weeks and a more homogeneous glucose distribution.