Development of Gliadin@AgNPs hybrid nanoparticles as building blocks for constructing antimicrobial protein-based porous materials

The accelerated rise of antibiotic-resistant bacterial strains presents a significant challenge to both global health and the economy. Although silver-based materials have already been successfully developed in dealing with the infections of drug-resistant bacteria, there has been much controversy over the applications of them because the waste silver nanoparticles (AgNPs) are potentially harmful to humanity and the environment. To address this issue, gliadin@AgNPs hybrid nanoparticles with ultralow minimum bactericidal concentration (MBC) were designed via growing AgNPs on amphiphilic gliadin molecule, followed by co-assembly-induced nanoencapsulation of AgNPs. The highly monodispersed gliadin nanoparticles (∼120 nm) infused with ultrasmall AgNPs (2–3 nm) were synthesized successfully. This strategy protected AgNPs from aggregation and fast oxidation, exerted programmed release profiles. In vitro antibacterial experiments demonstrate the hybrids could kill a broad-spectrum bacteria at an ultralow Ag equivalent, with MBCs of 0.0312 and 0.125 μg/mL for E. coli and MRSA, respectively. More importantly, its MBC against E. coli below the safety threshold established by the WHO for drinking water (0.1 ppm). Using the hybrid nanostructure as building blocks, we fabricated unprecedented protein-based antimicrobial porous materials for the first time through Pickering HIPEs templates, which was characterized by the formation of gliadin@AgNPs-decorated nanostructures on the pore wall of porous materials. They have a complex interlaced tubular porous structure with over 96 % porosity, presenting programmed release behavior of Ag+, and were able to inhibit the growth of tested bacteria at concentrations that did not affect the viability of HaCaT human cells, confirming that hierarchical nanomaterials possess valid antibacterial activity within the cellular viability concentration range. Particularly, the antimicrobial protein porous material promoted HaCaT cell adhesion and proliferation within its hierarchical nanostructure. This work provides new insights into the rational design of advanced gliadin@AgNPs as a potent antibacterial nanoplatform with a much smaller environmental impact and health concerns and a building block for constructing protein-based porous materials with outstanding antimicrobial performance and biocompatibility for emerging applications in catalysis, tissue engineering, and environmental engineering.