Scanning and Transmission Electron Microscopy of Poly 2-Hydroxyethyl Methacrylate-Based Biomaterials

Abstract

Hydrogels, especially poly 2-hydroxyethyl methacrylate, or pHEMA, have received increased attention for numerous biomedical applications. We have prepared several pHEMA-based biomaterials suitable as bone substitutes; alkaline phosphatase, for example, when immobilized in pHEMA in a copolymerization technique at 4°C retains its biological activity. When pellets of the biomaterial were placed in synthetic body fluids or tissue culture medium containing organic phosphates, numerous calcified nodules formed spontaneously. Osteoblast-like cells harvested on pHEMA or pHEMA/alkaline phosphatase materials can spread and establish direct contacts. However, the hydrophilicity of pHEMA is a real handicap for preparing scanning and transmission electron microscopic analyses. We have found that 2-propanol was an excellent dehydrating preparing for scanning electron microscopy before critical point drying. HEMA itself was found to dehydrate the transmission electron microscopy blocks because it can copolymerise with the methacrylate-based embedding resin Lowicryl K4M. These 2 preparation techniques have allowed us to study calcium-phosphate crystal growth and cellular responses in vitro on these hydrogel biomaterials. (The J Histotechnol 20:343, 1997)