Intracellular Bacterial Targeting by a Thiazolyl Benzenesulfonamide and Octaarginine Peptide Complex

Abstract

A brominated thiazolyl benzenesulfonamide (BTB) derivative is conjugated with the cell-penetrating peptide octaarginine (R8) in an effort to construct innovative antibacterial products. The noncovalent complex of BTB and R8 is characterized by Fourier transform infrared (FTIR) spectroscopy, which indicates hydrogen bonding between the two constituents. Attachment of the peptide moiety renders aqueous solubility to the hydrophobic benzenesulfonamide drug and bestows bactericidal activity. Confocal imaging in conjunction with dye probes shows successful clearance of intracellular Staphylococcus aureus bacteria by the BTB–R8 complex. Scanning electron micrographs and studies with a set of fluorescent dyes suggest active disruption of the bacterial cell membrane by the BTB–R8 complex. In contrast, the complex of BTB with octalysine (K8) fails to cause membrane damage and displays a modest antibacterial effect. A complex of BTB with the water-soluble hydrophilic polymer poly­(vinylpyrrolidone) (PVP) does not display any antibacterial effect, indicating the distinctive role of the cell-penetrating peptide (CPP) R8 in the cognate complex. The leakage of the encapsulated dye from giant unilamellar vesicles upon interaction with the BTB–R8 complex further highlights the membrane activity of the complex, which cannot be accomplished by bare sulfonamide alone. This work broadens the scope of use of CPPs with respect to eliciting antibacterial activity and potentially expands the limited arsenal of membrane-targeting antibiotics.

Approaches for evaluation of novel CPP-based cargo delivery systems

“…HPLC is often used for purification of the CPP-s post-synthesis, but it can also be used to characterize CPPcargo, and UPLC methods can be used to characterize the stability of CPP-cargo by detecting its degradation. Spectroscopy-based methods such as Fourier Transform infrared spectroscopy (FTIR) was used to characterize R8cargo complexes (Ratrey et al, 2022), and the presence of CPPs in the gold NPs was confirmed by this method (Boussoufi et al, 2018).…”

“…In addition to RBC, the interactions or leakiness can be investigated on more artificial setups, such as large unilamellar vesicles (LUV) and giant unilamellar vesicles (GUV) (Ratrey et al, 2022). By enclosing fluorescent dyes into the vesicles, the leakage of these detectable substances can be measured after interactions between the CPP-cargo and vesicles.…”