Photosensitizer and silver nanoparticles-modified surfaces: dual-pathway for bacterial inactivation

MARIA NOEL URRUTIA; GONZALO ACOSTA; FIORELA GHILINI; ANTONELA CÁNNEVA; EDUARDO PRIETO; ANDRÉS H. THOMAS; PATRICIA L. SCHILARDI

Rosario, Santa Fe

Congreso; 7ma Reunión Internacional de Ciencias Farmacéuticas (RICiFa 2023); 2023

Universidad Nacional de Rosario (UNR)

The use of photosensitizers (PS) immobilized on surfaces offers numerous advantages for their use in Photodynamic Inactivation (PDI), such as the possibility of reuse, ease removal after PDI treatment and increased photostability [1]. Pterins are PS that, under UV-A irradiation (320-400 nm), are able to photoinactivate pathogenic bacteria, either planktonic or sessile forming biofilms [2]. On the other hand, silver nanoparticles (AgNPs) were widely used as antibacterial against different microorganisms and have become one of the most studied alternatives for obtaining antimicrobial surfaces [3]. The aim of this work is the development, characterization, and evaluation of the antimicrobial performance of modified surfaces containing pterin derivatives and/or AgNPs. The PS and AgNPs combination would allow the PS to induce bacterial death upon irradiation, while AgNPs would allow a sustained antibacterial effect. A 11-bromoundecyltrichlorosilane (BUTS) molecular layer was formed on a glass substrate. To achieve this, different functionalization protocols were evaluated, being the most suitable that involving the immersion of substrates in a 15 mM BUTS solution in n-hexane at room temperature for 24 hours. Then, the bimolecular nucleophilic substitution (SN2) of the terminal bromine of BUTS by pterin (Ptr) was performed, using a mixture of Ptr and K2CO3 in N,N-dimethylacetamide at 70°C for 24 hours. On the other hand, the adsorption of AgNPs, was carried out by immersing the substrates in a dispersion of AgNPs at room temperature for 24 hours. The characterization of the BUTS-modified surfaces was assessed by X-ray Photoelectron Spectroscopy (XPS), revealing the characteristic signals of Br (~71 and ~184 eV for the 3d and 3p electronic states, respectively), confirming an adequate functionalization of the glass. The Br signal decreased after the reaction with Ptr and the N signal at ~400 eV confirmed the chemical binding of Ptr to BUTS. Furthermore, the typical doublet Ag3d5/2 (centered at ~368 eV) and Ag3d3/2 were detected in the Ag-containing samples. Also, the samples were evaluated using Atomic Force Microscopy (AFM) and contact angle measurements with a goniometer. Preliminary PDI experiments demonstrated that the surface with PS and AgNPs inhibited the growth of Staphylococcus aureus (ATCC 25923) under irradiation (86 ± 20% reduction in viable cells) compared to irradiated glass. Dark controls (in the presence and absence of PS and AgNPs) and irradiated controls (in the absence of PS and AgNPs) were performed.Our results indicate that PS and AgNPs-modified surfaces emerge as a potential platform for inhibiting biofilm formation, opening up the opportunity to explore novel applications.REFERENCES1.C. Spagnul, L.C. Turner, R.W. Boyle, J Photochem Photobiol B 150 (2015) 11.2.A. Miñán, et al, Biofouling 31 (2015) 459.3.F. Ghilini, et. al, ACS Appl. Mater. Interfaces 10 (2018) 23657.