Antibacterial Hydrogel as a Self-Drug-Delivery System Derived from Zn(II)-bis-imidazole/NSAID-Based Organic–Inorganic Hybrids

A skin
wound is prone to bacterial infection and growth. An antibacterial
topical hydrogel that can act as a self-drug-delivery (SDD) system
is reported here. Two bidentate ligands (L2/L1) derived
from imidazole/benzimidazole derivatives when reacted with Zn(NO3)2 and a series of nonsteroidal-anti-inflammatory
drugs (NSAIDs) produced crystalline products, which were characterized
by single-crystal X-ray diffraction (SXRD). Simple mixing of the ingredients
of the crystalline products (stoichiometry guided by the corresponding
crystal structure) produced an aqueous gel (DMSO/water) when the bidentate
ligand was water-insoluble L2, whereas water-soluble L1 readily produced hydrogels under similar conditions. Dynamic
rheology and scanning electron microscopy (SEM) were employed to characterize
the gels. Zone inhibition diameters, minimum inhibitory concentration
(MIC), minimum bactericidal concentration (MBC), and hemolysis data
suggested that among the hydrogelators, L1MEC derived
from L1, meclofenac and Zn(NO3)2, was found to be the best against the Gram-negative bacteria Escherichia coli. The corresponding hydrogel L1MEC_HG and a piece of a dried cloth bandage coated with
the hydrogel also showed appreciable activity against E. coli. The antibacterial property of L1MEC_HG against E. coli, thus demonstrated,
is relevant in developing an antibacterial SDD system because E. coli is reported to be present in infected wounds.