Development of visible light-responsive antibacterial coatings on neonatal intensive care incubators: An innovative approach to infection control

According to World Health Organization (WHO) data, neonatal infections cause the deaths of over 550,000 newborns annually, with a significant proportion originating not in utero or during delivery but in neonatal intensive care units (NICUs). Incubators, designed to maintain thermal homeostasis through elevated humidity and temperature, inadvertently provide a favorable environment for microbial contamination and biofilm formation. Gram-positive bacteria are particularly capable of proliferating in moist environments, establishing long-term surface colonization, and developing resistance to disinfectants, thereby increasing infection incidence. Previous reports have shown that, despite standard hospital disinfection protocols, bacterial biofilms persist on incubator surfaces. These biofilms, through extracellular polymeric substances (EPS), demonstrate strong disinfectant resistance and promote microbial persistence, facilitating long-term colonization and increasing the risk of hospital-acquired infections. To address this, visible-light-activated (450 nm) silver nanoparticle (AgNP) coatings were developed to reduce microbial load on incubator canopy surfaces. Three biocompatible polymer matrix formulations were synthesized: (i) AgNP-loaded PVP/ODA-MMT, (ii) AgNP-loaded PVP/MA/ODA-MMT, and (iii) AgNP-loaded CMC/MA/ODA-MMT. The coatings were deposited onto PMMA substrates by drop-casting and characterized via SEM-EDS, UV–Vis, and XRD. UV–Vis spectra revealed localized surface plasmon resonance (LSPR) peaks at 391, 409, 441 nm, confirming AgNP immobilization. XRD patterns showed characteristic fcc crystalline AgNP phases at 38,27° and 44,42°. Biocompatibility was assessed using HaCaT cells in MTT assays, demonstrating that all coatings were non-cytotoxic according to ISO 10993-5 standards. Antibacterial activity against S. aureus, S. epidermidis, and E. faecalis biofilms was investigated by confocal microscopy with live/dead staining. Inhibition efficiency increased with coating concentration. S. epidermidis was highly sensitive, showing strong inhibition even at low doses, while E. faecalis, due to its dense EPS matrix, exhibited the highest resistance. The optimal dose was identified as 1,5 mg/ml, achieving maximum antibacterial inhibition across all formulations and showing superior biocompatibility compared to colloidal AgNPs. In conclusion, visible-light-activated AgNP-loaded nanocomposite coatings provide strong antibacterial effects, biofilm inhibition, and acceptable biocompatibility for NICU surfaces. This approach offers enhanced microbial control compared to conventional disinfection, with the potential to reduce hospital-acquired infection risks. Further durability studies, clvalidation, and cost analyses willinical support translation into clinical application.