PDADMAC/Alginate-Coated Gold Nanorod For Eradication of Staphylococcus Aureus Biofilms

Abstract

Introduction

Over 75% of clinical microbiological infections are caused by bacterial biofilms that grow on wounds or implantable medical devices. This work describes the development of a new poly(diallyldimethylammonium chloride) (PDADMAC)/alginate-coated gold nanorod (GNR/Alg/PDADMAC) that effectively disintegrates the biofilms of Staphylococcus aureus (S. aureus), a prominent pathogen responsible for hospital-acquired infections.

Methods

GNR was synthesised via seed-mediated growth method, and the resulting nanoparticles were coated first with Alg and then PDADMAC. FTIR, zeta potential, transmission electron microscopy, and UV–Vis spectrophotometry analysis were performed to characterise the nanoparticles. The efficacy and speed of the non-coated GNR and GNR/Alg/PDADMAC in disintegrating S. aureus-preformed biofilms, as well as their in vitro biocompatibility (L929 murine fibroblast) were then studied.

Results

The synthesised GNR/Alg/PDADMAC (mean length: 55.71 ± 1.15 nm, mean width: 23.70 ± 1.13 nm, aspect ratio: 2.35) was biocompatible and potent in eradicating preformed biofilms of methicillin-resistant (MRSA) and methicillin-susceptible S. aureus (MSSA) when compared to triclosan, an antiseptic used for disinfecting S. aureus colonisation on abiotic surfaces in the hospital. The minimum biofilm eradication concentrations of GNR/Alg/PDADMAC (MBEC₅₀ for MRSA biofilm = 0.029 nM; MBEC₅₀ for MSSA biofilm = 0.032 nM) were significantly lower than those of triclosan (MBEC₅₀ for MRSA biofilm = 10,784 nM; MBEC₅₀ for MRSA biofilm 5967 nM). Moreover, GNR/Alg/PDADMAC was effective in eradicating 50% of MRSA and MSSA biofilms within 17 min when used at a low concentration (0.15 nM), similar to triclosan at a much higher concentration (50 µM). Disintegration of MRSA and MSSA biofilms was confirmed by field emission scanning electron microscopy and confocal laser scanning microscopy.

Conclusion

These findings support the potential application of GNR/Alg/PDADMAC as an alternative agent to conventional antiseptics and antibiotics for the eradication of medically important MRSA and MSSA biofilms.

Keywords:

• biofilm
• gold nanorod
• S. aureus
• PDADMAC
• MRSA
• MSSA

Disclosure

Dr Sek Peng Chin reports a patent UI 2022007566, Malaysian Utility Innovation pending. Professor Lik Voon Kiew reports a patent UI 2022007566 pending. The authors report no other conflicts of interest in this work.

Additional information

Funding

This study was funded by an Impact-oriented Interdisciplinary Research Grant (IIRG) (project codes: IIRG003B-19FNW and IIRG003C-19FNW) from the Universiti Malaya and the Ministry of Higher Education, Malaysia. This work was supported in part by the National Science and Technology Council (NSTC), Taiwan, ROC. (NSTC 112-2321-B-A49-005, NSTC 111-2112-M-A49-025, MSTC 110-2923-M-009-005-MY3, NSTC 111-2927-I-A49-004, and NSTC 112-2927-I-A49-001), and the Ministry of Education through the SPROUT Project and the Center for Intelligent Drug Systems and Smart Biodevices (IDS²B) of NYCU, Taiwan, ROC. Taiwan-Malaysia Semiconductor and Biomedical Oversea Science and Research Innovation Center, National Yang Ming Chiao Tung University, Hsinchu, Taiwan, ROC, for CCC.