Adsorption of matrix metalloproteinases onto biomedical polymers: A new aspect in biological acceptance

Matrix metalloproteinases (MMPs) are zinc-dependent enzymes involved in the remodelling of connective tissues during the development and wound healing. Moreover, two MMPs, Gelatinase A (MMP-2) and Gelatinase B (MMP-9), are also present in body fluids such as blood and urine and, therefore, they can be in contact with implanted biomaterials and can be adsorbed onto their surface. In order to test this hypothesis disks of different polymers (polystyrene (PS), polyvinyl chloride (PVC), poly(D,L-lactide) (PLA), polymethyl methacrylate (PMMA) and poly(2-hydroxyethyl methacrylate) (PHEMA)) have been exposed to human plasma and adsorbed proteins have been eluted and analyzed. Using Western blot and substrate zymography analysis, we observed that both MMP-2 and MMP-9 adsorbed onto the surfaces of all the polymers, especially hydrophilic ones (PMMA and PHEMA) and PLA, in both the active and inactive forms. Furthermore, we observed that adhesion of human granulocyte neutophils to PMMA, the polymer that adsorbed the higher quantity of MMP-2 and MMP-9 compared to the others, was reduced by more that 50% by the presence of a gelatinase inhibitor. This data suggest a surprising role of these absorbed enzymes in the adhesion of neutrophil onto some polymeric biomaterials surface and, therefore, in the setting of inflammation.