ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Visible light-induced synergic antimicrobial activity of silver nanoparticles/methylene blue nanohybrids encapsulated in chitosan and pluronic polymers

Giovanni Alexsander Silva Lima, Guilherme Gonçalves Guerini, Suzan Pantaroto de Vasconcellos, and Diogo Silva Pellosi

Laboratory of Hybrid Materials, Department of Chemistry, Federal University of São Paulo, Centro Diadema, Brazil

E-mail: diogo.pellosi@unifesp.br

Received: 9 August 2022  Accepted: 19 September 2022

Abstract:

Despite the extraordinary advances, bacterial infections continue to be one of the main concerns in modern medicine due the development of antibiotic multidrug resistant strains. In this scenario, the development of new antimicrobial agents that can act by multiple targets avoiding resistance development is urgent. Among several approaches, the use of silver nanoparticles (AgNP) and photodynamic therapy are highlighted. However, these modalities alone have not been enough. Therefore, in this work, we integrated AgNP and the photosensitizing agent methylene blue (MB) favorable photophysical properties into Pluronic P123 and chitosan polymers creating an AgNP/MB nonohybrid structure as demonstrated by UV–Vis, particle size and transmission electron microscopy analysis. These were carefully engineered to tune the distance between AgNP-MB aiming to enhance material photophysics through resonant coupling of MB photosensitizer and AgNP. The nanohybrid allowed a significant enhancement of hypertoxic singlet oxygen (¹O₂) generation, which in turn promoted the inactivation of S. aureus and E. coli bacteria, under red LED light irradiation. Chou−Talalay statistics demonstrated that when AgNP and MB are working together, especially in P123 formulations, a strong synergistic action occurs mainly due to the so-called double-enhancement mechanism, which improves the in situ Ag⁺ and ¹O₂ release, inducing bacteria to inactivation. These results showed the importance of the rational design for engineering new and efficient multifunctional nanomaterials, indicating that Pluronic-loaded AgNP/MB nanohybrids can act as a next-generation of antimicrobial nanoplatforms against bacterial infections.

Graphical abstract

Keywords: Bacteria inactivation; Photodynamic therapy; Silver; Photosensitizing agent

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02509-1

Chemical Papers 77 (1) 549–561 (2023)