Exploring Glutathione as a Ligand for Personalized Antibiotic Loading Against Bacterial Infections

Acute bacterial skin and skin structure infections (ABSSSI) are a major burden on healthcare systems globally. Systemic treatment of ABSSSIs is often complicated by subtherapeutic drug concentrations at the infection site. Localized therapeutic delivery may overcome such barriers but current formulation approaches remain rigid and unable to accommodate flexible antimicrobial loading for ABSSSI treatment. Glutathione (GSH) is a tripeptide conventionally employed as a ligand for glutathione-S-transferase (GST) protein binding but also contains two anionic and one cationic functional groups. We explored the novel use of GSH as an association site for charge-bearing antimicrobials to provide an approach for selective antibiotic loading within polymeric hydrogels. Following polymerization of poly(ethylene glycol) hydrogels in the absence (PEG) or presence of GSH (GSH-PEG), electrostatic intermolecular forces were confirmed in the presence of GSH ligands. Placing blank hydrogels within drug solutions, increased loading of cationic and zwitterionic drugs was observed within GSH-PEG as compared to PEG hydrogels whereas anionic drugs were observed to load similarly in GSH-PEG and PEG hydrogels. Further flexibility in GSH-PEG hydrogel preparation was demonstrated by varying loading solution drug concentration to establish several dosage strengths while maintaining a rapid, clinically-relevant one hour loading period. Controlled release of antibiotics from GSH-PEG hydrogels was confirmed under submerged conditions and within a Franz diffusion system, mimicking topical application. Dose-dependent bacterial clearance was achieved with drug loaded GSH-PEG hydrogels using in vitro time kills and an ex vivo porcine dermis infection model. Moreover, the observed bacterial killing confirmed in silico mechanism-based modeling simulations, supporting the predictable and reliable nature of the GSH-PEG delivery phenomena. Conversely, human dermal fibroblast migration and proliferation was not significantly impaired in the presence of drug loaded or blank GSH-PEG hydrogels. Our findings successfully broadened the utility of GSH ligands beyond protein anchoring, providing flexible antibiotic association sites to achieve safe and effective release. These findings advance the concept of multi-functional delivery platforms in an effort to provide local therapeutic delivery tailored to patient needs in a timely and accessible manner.