Understanding the Influence of Serum Proteins Adsorption on the Mechano‐Bactericidal Efficacy and Immunomodulation of Nanostructured Titanium

Abstract

Nanostructured surfaces are effective at physically killing bacterial cells, highlighting their prospective application as biomaterials. The benefits of application of mechano‐bactericidal nanostructures as an alternative to chemical functionalisation are well documented, however, the effects of protein adsorption are not well understood. In this work, theoretical and experimental analyses are conducted by studying the adsorption of human serum proteins (HSP) to nanosheet titanium (Ti) and its subsequent effect on the mechano‐bactericidal efficacy toward Staphylococcus aureus and Pseudomonas aeruginosa cells. The nanosheet pattern exhibits enhanced antibiofouling behaviour mantaining high bactericidal efficiency toward both Gram‐negative and Gram‐positive cells in the presence of adsorbed HSP. To ascertain the immunomodulatory response, S. aureus cells are introduced to protein‐conditioned Ti nanosheet surfaces prior to introducing RAW 264.7 macrophages. On the pre‐infected nanostructured surfaces, macrophages exhibit wound healing behaviour with superior activation of M2‐like macrophage polarization and secretion of anti‐inflammatory cytokines. By contrast, macrophages attached to infected smooth surfaces activated the M1‐like polarized phenotype via the high expression of pro‐inflammatory cytokines, indicating persistent inflammation. The outcomes of this work demonstrate the suitability of Ti nanosheets as a potential biomaterial surface whereby the mechano‐bactericidal activity is not compromised by HSP adsorption and, furthermore, positively influenced an anti‐inflammatory immune response.