Adsorption and release profiles of gelatin hydrogel-coated CI electrodes for recombinant human IGF1 (rhIGF1). (A) Adsorption of rhIGF1 was expressed by relative radioactivities of incorporated 125I-labeled rhIGF1 (n = 6). Gel (−), gel (+) and gel (++) represent non-coated, single-hydrogel-coated and double-coated electrodes, respectively. Error bars indicate the standard deviation (SD). *P < 0.01. (B) Time-course of the rhIGF1 radioactivity on test electrodes after gently agitated in 37C phosphate-buffered saline (PBS), with or without type I collagenase. Note that even after 24 h, hydrogel-coated electrodes retained more than 7% of IGF1 in natural environment (gray boxes).