A supramolecular assembly made of poly-sulfobutyl-β-cyclodextrin and a tetracationic Zn (II) porphyrin for antimicrobial photodynamic therapy

The rise of multidrug-resistant (MDR) pathogens poses an increasingly critical challenge in the management of nosocomial infections. Conventional therapeutic treatments often fail due to bacterial resistance mechanisms, including biofilm production, which significantly impairs antibiotic efficacy [1]. Consequently, there is a strong requirement for innovative and more effective therapeutic strategies. In this context, Antimicrobial Photodynamic Therapy (aPDT) has emerged as a highly promising complementary approach [2]. aPDT involves the activation of photosensitizers (PSs) by visible (Vis) or near-infrared (NIR) light, resulting in the generation of cytotoxic reactive oxygen species (ROS), predominantly singlet oxygen (¹O₂). Within our ongoing research on nanophotosensitizers (nanoPS) based on cyclodextrins [3,4], we report here a novel supramolecular assembly based on a soluble sulfobutyl-β-cyclodextrin polymers (SBBCDPS) [5] and the zinc(II) derivative of 5,10,15,20-Tetrakis(1-methylpyridinium-4-yl)porphine tetrakis(p-toluenesulfonate) (ZnTMPyP). The assembly was fully characterized by UV/Vis, steady-state and time-resolved emission spectroscopies, Dynamic Light Scattering (size and ζ-potential measurements). Stability studies in biological relevant media were carried out to establish the suitability of SBBCDPS/ZnTMPyP assemblies in antibacterial photodynamic application against bacteria involved in fatal hospital-acquired infections.