Acylase-Based Coatings on Sandblasted Polydimethylsiloxane-Based Materials for Antimicrobial Applications

Abstract

Indwelling medical devices, such as urinary catheters, often experience bacterial colonization, forming biofilms that resist antibiotics and the host's immune defenses through quorum sensing (QS), a chemical communication system. This study explores the development of antimicrobial coatings by immobilizing acylase, a quorum-quenching enzyme, on sandblasted polydimethylsiloxane (PDMS) surfaces. PDMS, commonly used in medical devices, was sandblasted to increase its surface roughness, enhancing acylase attachment. FTIR analysis confirmed that acylase retained its three-dimensional structure upon immobilization, preserving its enzymatic activity. The antibacterial efficacy of the coatings was tested against Pseudomonas aeruginosa (P. aeruginosa) (a common biofilm-forming pathogen), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli). The results showed that sandblasted PDMS surfaces had improved bacterial adhesion due to increased focal adhesion points, but acylase-functionalized surfaces had significantly reduced bacterial attachment and biofilm formation. Notably, the coatings inhibited P. aeruginosa growth by 40% under static conditions, demonstrating the potential of acylase-functionalized PDMS for medical applications. This approach offers a promising strategy for creating antimicrobial surfaces that prevent biofilm-related infections in urinary catheters and other medical devices. The findings highlight the dual role of surface roughness in enhancing enzyme attachment while reducing bacterial adhesion through effective QS inhibition.

Keywords: PDMS; acylase; quorum quenching; quorum sensing; sandblasting.

Figure 1

Disruption of quorum sensing in bacteria by acylase. Acylase acts as a QQ agent by cleaving the amide bond in AHLs, the QSM used by Gram-negative bacteria to communicate. By breaking down AHLs in the extracellular environment, acylase prevents these molecules from reaching the threshold concentration needed to activate QS receptors. This inhibition blocks QS-regulated behaviors, such as biofilm formation and virulence factor production, effectively disrupting bacterial communication and reducing infection potential.

Figure 2

(a) Assembly of acylase on the PDMS sandblasted stripes, (b) reaction of the ninhydrin test: the amino groups present on the PDMS surface from APTES treatment with ninhydrin will form a blue purple complex, (c) ninhydrin test: (1) mesh 180 with APTES; (2) PDMS with APTES; (3) PDMS; (4) PDMS with APTES and acylase.

Figure 3

Characterization of the PDMS materials: (a) FTIR-ATR spectra of an untreated sample and b acylase-coated sample, (b) FTIR spectrum of the materials between 1200 cm⁻¹ and 1800 cm⁻¹, highlighting the amide I, II, and III regions. a, untreated sample and b acylase-coated sample, (c) quantification of secondary structures in the materials based on FTIR spectral analysis. The graph displays the percentages of α-helix, β-turns, β-sheets and random coils present in both samples; (d) surface wettability of PDMS materials before and after treatment (sandblasting and acylase-coating).

Figure 4

Surface roughness measurements of the materials: (a) PDMS, (b) mesh 60, (c) mesh 180, (d) combined.

Figure 5

Antimicrobial activity of acylase-coated and untreated samples against P. aeruginosa, S. aureus and E. coli strains in solution after 2 h in contact with material.

Figure 6

Fluorescence microscopy Live/Dead images for (1) PDMS; (2) PDMS + acylase; (3) mesh 180; (4) mesh 180 + acylase; and E. coli on different material surfaces after 2 h of incubation. Scale bar represents 20 µm for all images.

Figure 7

(a) Quantification of pyocyanin production by P. aeruginosa using UV-Vis spectroscopy at 695 nm. The absorbance values at 695 nm correspond to the concentration of pyocyanin in the bacterial culture supernatant. Samples were measured in triplicate, and error bars represent standard deviations. (b) Biofilm production expressed as a percentage relative to the untreated control. Error bars represent standard deviations from triplicate experiments.