Bacterial anti-adhesive films of PDMS coated with microstructures of biogenic silica rosettes extracted from pineapple peels residues

Abstract

The appearance of several multi-drug resistant strains has been linked to the extensive use of antibiotics. The use of bio-inspired plant and animal surfaces that exhibit new strategies such as contact-killing surfaces has been proposed to face this problem. Pineapple peels expose 10 µm in length and 5 µm height biogenic silica rosettes (BSR) on their cuticle surface. These BSRs are formed by granules with sized of about 300 nm, which improve their mechanical properties and responses against stresses such as microorganisms' attacks. This study presents a valuable application of pineapple peel BSRs, becoming an attractive raw material for generating products with economic value such as coatings against non-specific adhesion of cells and bacteria on polydimethylsiloxane. Characterization techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and water contact angle were used. We found that the high-density coverage coating formed by BSR increased the PDMS roughness and surface's water repellency while decreasing the Escherichia coli (E. coli) bacteria adhesion. Besides, the cell membrane disruption effect on red blood cells was investigated. Inspired also by the cuticle of pineapple plants formed by lipids and waxes, we further functionalized the BSR with octadecyltrietoxysilane with the aim of increasing the hydrophobicity of the areas between the BSR voids and BSR surface. Bacteria adhesion decreased from 27% to 14% and an increased in contact angle from 130° to 158°. This coating has other potential uses, such as serving as a platform for encapsulating active compounds due to its high porosity. Therefore, different BSR arrangements could be studied to improve its antifouling properties.