Synergistic Antimicrobial Activity of a Nanopillar Surface on a Chitosan Hydrogel

Abstract

Despite ongoing efforts and technology development, the contamination of medical device surfaces by disease-causing microbes remains problematic. Two approaches to producing antimicrobial surfaces are using antimicrobial materials and applying physical topography such as nanopatterns. In this work, we describe the use of physical topography on a soft hydrogel to control microbial growth. We demonstrate this approach by using chitosan hydrogel films with nanopillars having periodicities ranging from 300 to 500 nm. The flat hydrophilic chitosan films exhibit antimicrobial activity against the pathogenic bacteria Pseudomonas aeruginosa and filamentous fungi Fusarium oxysporum . The addition of nanopillars to the hydrogel surface further reduces the growth of P. aeruginosa and F. oxysporum up to ∼52 and ∼99%, respectively. Multiple modes of antimicrobial action appear to act synergistically to inhibit microbial growth on the nanopillar hydrogels. We verified that the strongly bactericidal and fungicidal nanopillared material retains biocompatibility to human epithelial cells with the MTT assay. The nanopillared material is a promising candidate for applications that require a biocompatible and antimicrobial film. The study demonstrates that taking advantage of multiple modes of antimicrobial action can effectively inhibit pathogenic microbial growth.

Nanopillar Templating Augments the Stiffness and Strength in Biopolymer Films

“…Genipin is a common covalent cross-linker for aminecontaining biomaterials. 44,45 Uniaxial tensile testing verified that the nanopillar topography enhanced the mechanical performance of the hydrogels (Figure 6a, Table S8). The moduli of the flat chitosan−genipin film was 3.8 MPa, similar to values previously reported.…”

“…The genipin cross-linked films were fabricated as previously described. 44 A stock cross-linker solution was prepared by dissolving genipin in ethanol. An appropriate volume of genipin in ethanol mixture was added to a 1.1 w/v% chitosan solution (10:1 chitosan to ethanol) to obtain a final concentration of 0.25 mM genipin and 1 w/v% chitosan solution.…”

“…The master molds were prepared as previously described. 44,56,57 Briefly, the thermoplastic polyurethane solution was cast onto the prepared master molds or a flat polytetrafluoroethylene support. In both cases, the polyurethane-coated master molds were annealed at 70 °C to evaporate residual solvent.…”

The effects of surface topography modification on hydrogel properties

“…Pseudomonas aeruginosa was cultured on both cast flat and surface patterned chitosan hydrogel films for 18 h, and CFUs were then counted on agar plates to see if the surface topography could inhibit the bacteria growth. 138 Compared to the flat hydrogel films, P. aeruginosa cultured on nanopillars with 120 nm diameter and 230 nm height showed 31% lower CFUs. Nanopillars with 190 nm diameter and 400 nm height exhibited even better antibacterial property with 52% lower CFUs compared to flat chitosan films.…”

Mechanobactericidal, Gold Nanostar Hydrogel-Based Bandage for Bacteria-Infected Skin Wound Healing

“…Hydrogels are an attractive option for wound care management with biocompatibility, biodegradability, water retention capacity, and flexibility. , Lately, cellulose-, chitosan-, and carrageenan-based hydrogels have been developed, and their practicability to be used in wound healing has been studied. Alginate is a natural polymer that provides attractive features like biocompatibility and hydrophilicity. , Furthermore, reports have suggested its role in activating inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor α (TNF α) to accelerate wound healing.…”