Dual-Function Antibacterial and Antibiofilm Agent Based on a Confinement-Activated Fluorescent System in Water

The influence of host-guest interactions on the physical behavior of encapsulated species represents a compelling area of study. Research in this domain has predominantly centered on how these interactions affect catalytic activity and the photoluminescence properties of confined guest molecules. In contrast, their potential impact on antibacterial and antibiofilm activity has been rare. In this report, we present antibacterial and antibiofilm activity of a Pd₈ low-symmetric molecular barrel (LSMB) based host-guest system (TPH⊂LSMB) in water. The new low-symmetric ligand (L) upon self-assembly with a cis-Pd(II) acceptor generated a tetrafacial low-symmetrical barrel (LSMB). Encapsulation of a guest TPH [1,4-bis(2,2-diphenylvinyl)benzene], which is otherwise non-emissive in dilute solution, by LSMB resulted in a remarkable increase in its emission intensity even in very dilute aqueous conditions. The host-guest complex (TPH⊂LSMB) shows better antibacterial and antibiofilm activity compared to the host (LSMB). More interestingly, TPH⊂LSMB shows better antibacterial and antibiofilm activity against Gram-negative bacterial strains as compared to Gram-positive strains. This selectivity against Gram-negative strains provides a critical advancement in the rational design of supramolecular antibacterial and antibiofilm agents. The findings provide valuable insights for the development of next-generation, light-independent therapeutic systems specifically tailored to overcome the inherent challenges posed by Gram-negative pathogens.