Fetuin-A Adsorption on Tunable Polydimethylsiloxane and Subsequent Macrophage Response

Abstract

To date, protein adsorption is an unavoidable response to implanted biomaterials. When proteins interact with materials, adverse biological events such as thrombus formation and inflammation can occur and challenge device efficacy. Protein adsorption is influenced by various material and surface properties which can be modified in efforts to alter the protein-material interactions and the subsequent cellular response. There is a need for simple modifications of commonly used biomaterials and the effect of these modifications on (1) material properties (2) proteins and (3) cells is important to study. In this work, the effect of modifying polydimethylsiloxane (PDMS) and its interactions with fetuin-A are studied for potential immunomodulatory properties. PDMS modifications are achieved by altering the ratio of PDMS formulations to simply and effectively control elastic modulus, and by coating PDMS with polydopamine (PDA), a molecule commonly used as a bioglue. Surface characterization confirmed that altering the PDMS formulation changed the elastic modulus without affecting surface wetting properties. Minor changes in surface roughness via atomic force microscopy and surface chemistry via x-ray photoelectron spectroscopy were detected on some samples, and the deposition of PDA was confirmed. Protein adsorption studies provided quantitative and qualitative data on fetuin-A interactions. It was determined that fetuin-A adsorption was influenced by the PDMS formulations, and that the preferential adsorption changed when adsorbed from a competitive environment. Following modification of samples with adsorbed fetuin-A, the inflammatory effects of fetuin-A were investigated by measuring the concentration of pro- and anti-inflammatory cytokines in response to modified and unmodified samples. Data suggest that elastic modulus influences cytokine secretion at certain timepoints, a result of varied protein adsorption amounts and orientations in response to material stiffness. The addition of a PDA layer demonstrated the potentially cytokine mitigating effect of PDA cell interactions and protein immobilization when compared to unmodified PDMS samples.