Gelatinase-Responsive Short Peptide Conjugate as a Precision Therapy Against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to most antibiotics, posing a major challenge to effective treatment. To address this, a gelatinase-responsive short peptide has been synthesized, selectively targeting pathogenic MRSA while sparing beneficial bacteria in the microflora. The therapeutic peptide, Py-FFRPLGVRGKKQK (Py-FGGK; Py: Pyrene), comprises a fiber-forming Py-FFR sequence, a gelatinase-cleavable linker (PLGVRG), and a heparan sulfate (HS)-binding motif (KKQK). HS is found ubiquitously on the MRSA-infected site. Py was used as a fluorescent marker apart from favoring self-aggregation through π-stacking interactions. Reverse-phase HPLC studies showed a serum half-life of ∼4.5 h, and isothermal calorimetry confirmed moderate binding with heparin sulfate (HPS) (3.08 ± 0.2 × 10⁴ M^-1), a pharmaceutical analogue of HS. Cationic lysine-derivatives in Py-FGGK, helped in specific binding to HS at the MRSA-infected site, followed by gelatinase-mediated cleavage at the G-V site, releasing the active component Py-FFRPLG (Py-FG), which self-assembled into amyloid fibrils via aggregation of the bis-phenylalanine moieties on the MRSA surfaces causing remarkable antibacterial activity. Py-FGGK is highly effective in biofilm disruption, leakages of cellular constituents, in situ ROS generation, killing biofilm-embedded cells, and favoring cellular migration in NIH/3T3 Cells that help wound healing. The significance of each synthon in Py-FGGK is demonstrated by control studies using various model peptides with appropriate structural variations. Biocompatibility of Py-FGGK as a potential therapeutic agent is ensured through hemolysis assay and insignificant mortality toward live HEK293 and WI38 cells. Its efficacy in wound healing and recovery of MRSA-infected female albino Wistar rats is also demonstrated.