(J-389) Nanocoatings for Nosocomial Infection Prevention

Introduction:: Healthcare-associated infections (HAI) have a significant impact on public health and require the use of infection prevention strategies to minimize the risk for medical personnel and patients. Fomites, inanimate surfaces that are likely to be contaminated with microbes, may become a passive source of infection. For instance, noncritical frequently touched surfaces (FTS) such as doorknobs and bedside tables can become important vectors for fomite-mediated HAI. Hence, to mitigate this risk, low-level disinfection (LLD) is widely used to reduce up to 99.99% of pathogens by applying liquid disinfectants onto FTS. However, a significant drawback to this method is the need for repeated disinfectant application since recontamination can occur at any moment after cleaning. To address this issue, we developed self-disinfecting nanocoatings based on photocatalytic metal oxides (PMO), which can produce electron-hole pairs as a result of visible light irradiation. We hypothesized that reactive oxygen species (ROS) formed by the interaction of electron hole-pairs with oxygen and environmental moisture could exert a continuous bactericidal effect to protect FTS exposed to indoor LED light.


Materials and Methods:: PMO nanoparticles were surface-decorated with a high density of non-metal polymers (NMP) to extend their photo-responsive performance into the visible light range, following methods previously published [1]. Next, the photocatalytic oxidative potential under visible light of the resultant core-shell NMP PMO nanoparticles (2 mg/mL in deionized water) was evaluated by the photodegradation of Rhodamine B (RhB, 1 ppm). Thereafter, nanocoatings were prepared by mixing NMP PMOs into a polymeric carrier material and applied onto aluminum tickets (1.89 mg NMP PMO/ cm²) to test their antimicrobial performance under visible light irradiation against S. aureus and E. coli, following methods adapted from literature published by the EPA [2].

Results, Conclusions, and Discussions::

The photocatalytic activity of NMP PMO resulted in 96% degradation of RhB in 48 hours (Fig. 1A). The hypsochromic shift from 555 nm to 490 nm (blue arrow) is evidence of the presence of advanced oxidative processes. Images of nanocoated and uncoated (control) aluminum tickets demonstrated the success of nanocoatings on planar surfaces (Fig. 1B). The antimicrobial effect of the nanocoating under visible light irradiation resulted in around 99.999% (5-log₁₀) reduction in the bacterial population (Fig. 1C). These results were confirmed by plating samples of S. aureus inoculum tested against control and nanocoating (Fig. 1D). Similar results were obtained for E. coli (Fig. 1E).

To conclude, in this proof-of-concept study we developed and successfully tested a nanocoating that significantly reduces gram positive and gram-negative bacterial populations by the effect of oxidative stress triggered by the action of visible light from an LED lamp. The relevance of these results is related to their translational potential to reduce HAI risk by impeding pathogen growth on FTS. Future work will be focused on understanding the mechanisms involved and optimizing the formulation and its performance to reduce the time and light intensity required to exert the bactericidal affect.






Acknowledgements (Optional): : LSG is supported by NIH F31 AI169954 (LS) and previously by NIH T32 HL134613 (LS, KTN). Research has been partially supported by NIH R15 HL156076 (KTN) and R01 HL158204 (KTN).

References (Optional): : [1] Mao WX, Lin XJ, Zhang W, Chi ZX, Lyu RW, Cao AM, et al. Core-shell structured TiO2@polydopamine for highly active visible-light photocatalysis. Chemical communications (Cambridge, England). 2016;52(44):7122-5.

[2] US Environmental Protection Agency. Interim Method for Evaluating the Efficacy of Antimicrobial Surface Coatings; 2020 [Available from: https://www.epa.gov/pesticide-analytical-methods/antimicrobial-testing-methods-procedures-interim-method-evaluating.]