Mesoscopic sponge-like topology engineered onto polypropylene promotes retention of bound protein: Material synthesis, characterization and utility

A simple synthetic approach was developed to transform ordinary polypropylene tubes into high-surface, protein-retaining plastics. The inner surface of native tubes was activated by incubation with aqueous persulfate. Infrared spectroscopic analyses of plastics treated in this fashion revealed significant amounts of carboxylic acids, ketones and alcohol groups as products. Concomitant to activation, a transformed surface was yielded, which displayed a meso-structured, high-area topology. The topology, reminiscent to the appearance of natural sponge, appeared to have been caused by an oxidation-induced phase separation. The enhanced chemical reactivity of oxidized surface-pendent functional groups greatly facilitated re-engineering of surface physico-chemical traits. The oxidized surfaces were treated with the hydrolysis products of aminopropyltriethoxysilane, and ninhydrin or glutaraldehyde, affording the corresponding amino and aldehyde surface derivatives. The performance of each tailored surface was assessed by the extent to which albumin could be loaded and retained following several washings. The results of the immobilization study indicated that appropriately engineered mesoscale topologies could greatly improve the retention of noncovalently adhered proteins. A model is proposed to rationalize the contribution of the mesostructure to protein binding.