(471f) Photochemical Reaction Kinetics and Thermodynamics of Light-Induced Collagen Cross-Linking with Rose Bengal for Suture-Less Wound and Incision Closure and Repair

Photochemical tissue bonding (PTB) of wounds and surgical incisions relies on the use of photosensitive molecules and light to induce the formation of covalent linkages in collagenous tissue. Rose Bengal (RB) has been found to be a suitable photosensitizer (dye) for PTB as well as for Photochemical Tissue Passivation (PTP). The light-induced cross-linking of collagenous matrices in the presence of RB has yielded promising results in laboratory and clinical trials in terms of wound closure, reduced inflammation and less scaring. However, the required irradiation doses are still higher than what would be ideal for broad implementation of this phototherapy. We recently proposed that the aggregation of RB molecules (monomers) lowers the quantum yield of reactive oxygen species (ROS) molecules. Kinetic steady-state analysis showed that dimeric species are not as effective as monomeric RB for the photochemical ROS-mediated therapy. Here, we tested several cucurbituril and cyclodextrin based nanocages (NCs) as potential inhibitors of RB aggregation to study the effect of dimerization on RB photobleaching and oxygen consumption kinetics when RB is irradiated with green light in aqueous phosphate-buffered solutions.We discuss the effects of RB and nanocage concentrations in a proposed mechanism for the RB light-induced oxidative decomposition process that has previously been linked to the formation of crosslinks in the presence of collagenous tissue. Our proposed mechanism integrates thermodynamic and reaction kinetics of the RB photo-oxidation reaction via the monitoring of the photochemical reactions with multiple spectroscopic techniques in tandem. Notably, we utilized a fluorescence-based oxygen sensor to monitor the concentration of molecular oxygen in real-time. We confirmed that the RB/HP-γ-CD host-guest complex yields the fastest photobleaching and oxygen consumption rates. The cyclodextrins appear to be better candidates for precluding RB aggregation, making them great candidates for novel PTB approaches with higher efficiencies and lower fluence requirements. We provide a comprehensive analysis of the photochemical and photophysical pathways of nanocaged RB to better understand how to control the function of RB as a photo-active ROS-therapeutic agent. We hope that this contribution helps advance the field of photomedicine in general, and the implementation of PTB for tissue bonding and repair in particular.