A nanohybrid assembly composed of silver nanoparticles and porphyrins for antimicrobial photodynamic applications

Multifunctional hybrid nanomaterials composed of organic and inorganic components are extensively studied for the improved performances deriving by the combination of chemically different species, thus providing applications in several fields including biomedical applications [1]. If porphyrins are employed as organic components for the construction of multifunctional nanoscale architectures, their ability to act as photosensitizer able to kill bacteria or virus under light exposure enables the applications in antimicrobial photodynamic therapy (aPDT) [2]. Similarly, the use of silver nanoparticles as antimicrobial agent is extensively known [3]. With the aim to gain a boosting effect from the synergy between the photosensitizer and silver nanoparticles combined in a single nanohybrid materials, this study deals with the synthesis of AgNPs@H2T4 nanoassembly composed of meso-tetrakis(N-methylpyridinium 4-yl)porphine (H2T4) and silver nanoparticles (AgNPs), finely combined through synthetic procedures based on a supramolecular approach. Metal nanoparticles have been synthesized through reduction metal synthesis assisted by a cyclodextrin based polymer bearing citrate functionalities [4] which acts as stabilizing agent of NPs. The organic covering layer composed of cyclodextrins provides biocompatibility to NPs, which could be transferred into bacteria thanks to the widely proven carrier ability of the organic macrocycle. Several spectroscopic techniques including UV-vis absorption, static and dynamic fluorescence emission, Dynamic Light Scattering and Z- potential measurements, have been used to characterize the nanohybrid. In-vitro antibacterial activity has been evaluated against P. aeruginosa ATCC 27853 and two clinical isolates characterized by broad-spectrum resistance. Results indicate that AgNPs@H2T4 nanoassembly shows the highest biocidal activity when exposed to light, particularly against the two clinical isolates. Our approach allows for a control of the photosensitizer content in core-shell NPs aiming to design novel nanophototherapeutics with promising dual action.