(678g) Gold Nanoclusters Immobilised Onto Polymer Brushes As Stable Anti-Microbial Surfaces

Bacteria have built resistance against antibiotics due to their abusive usage, which will increasingly affect the treatment of certain infectious diseases and impact modern surgery, chemotherapy, and organ transplantations. According to the latest WHO report, at least 700,000 people die each year due to drug-resistant diseases, and this could cause 10 million deaths each year by 2050 if no actions are taken.¹ While medical scientists are working at a genetic level to combat anti-microbial resistance (AMR), it is essential to develop a methodology that can kill or prevent bacteria from colonialising surfaces in the first place (especially in healthcare) before spreading germs and causing infections. Advancements in nanotechnology have helped tackle major challenges in medicine, such as targeted drug delivery and cancer treatments.² In this context, atomically precise gold clusters have gained immense attention because of their high ratio of low-coordinated gold atoms on the surface with unique structural geometry.³ Ultra-small particles of gold are known to exhibit anti-microbial activity because they can control the production of reactive oxygen species (ROS), which ultimately kill the bacterial cells.⁴ Additionally, surface properties such as charge and hydrophilicity are known to exhibit bacteriostatic properties to reduce the adhesion of bacterial cells.⁵ In this regard, bactericidal properties of gold and bacteriostatic properties of polymers can be combined to create antimicrobial surfaces.

This study reports the synthesis and immobilisation of atomically precise gold nanoclusters (0.8 nm in diameter)⁶ onto polymer brushes grafted from the membrane surface to develop stable anti-microbial surfaces with minimum leaching of the nanoparticles. The physical and chemical properties of these surfaces are studied using XPS, AFM, SEM and UV-VIS spectroscopy. These surfaces were further tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, which are rapidly developing resistance against antibiotics and are a common cause of infection in healthcare facilities. The synthesised surfaces exhibit 90% and 96% reduction in S. aureus and E. coli, respectively, within one hour of contact. These findings suggest that these materials could be potentially used in healthcare facilities (such as fabrication of catheter surfaces or surgical coatings) to kill the bacterial cells effectively.

References

1. No time to wait: Securing the future from drug-resistant infections; Report To The Secretary-General of The United Nations. 2019.
2. Peer, D.; Karp, J. M.; Hong, S.; Farokhzad, O. C.; Margalit, R.; Langer, R., Nanocarriers as an emerging platform for cancer therapy. Nature nanotechnology 2007, 2 (12), 751-760.
3. Du, Y.; Sheng, H.; Astruc, D.; Zhu, M., Atomically Precise Noble Metal Nanoclusters as Efficient Catalysts: A Bridge between Structure and Properties. Chem. Rev. 2020, 120 (2), 526-622.
4. Zheng, K.; Setyawati, M. I.; Leong, D. T.; Xie, J., Antimicrobial gold nanoclusters. ACS nano 2017, 11 (7), 6904-6910.
5. Mohamed, H.; Hudziak, S.; Arumuganathan, V.; Meng, Z.; Coppens, M.-O., Effects of charge and hydrophilicity on the anti-fouling properties of kidney-inspired, polyester membranes. Molecular Systems Design & Engineering 2020, 5 (7), 1219-1229.
6. Kapil, N.; Weissenberger, T.; Cardinale, F.; Trogadas, P.; Nijhuis, T. A.; Nigra, M. M.; Coppens, M.-O., Precisely Engineered Supported Gold Clusters as a Stable Catalyst for Propylene Epoxidation. Angew. Chem. Int. Ed. 2021, 60 (33), 18185-18193.