Synthesis and Characterization of Water-Soluble Polypyrrole-Sulfonated Naphthalene Formaldehyde Composite as a Selective Turn-off Chemosensor for Pb2+, Antimicrobial Activity, and Molecular Docking Studies

The water-soluble polypyrrole-sulfonated naphthalene formaldehyde (PPy-SNF) composite was synthesized via a one-step in-situ oxidative polymerization process. The prepared PPy-SNF composites were characterized using FT-IR, UV-Vis, SEM, DAX, XRD, and DLS techniques. The conductivity of PPy-SNF 5 reached 0.249 Scm⁻¹, which is higher than the other mole ratios studied (PPy-SNF 1, 2, 3, 4, and 6). The fluorescence behaviors were investigated by photoluminescence spectroscopy. Pb²⁺ ions can effectively quench the fluorescence intensity of PPy-SNF via the inner filter effect. The proposed fluorescence probe’s excellent performance and satisfied linear ranges were obtained over the 2.2–3.5 µM range, with the lowest detecting limit of 2.9 nM attained by the PPy-SNF 5 composite. Also, the fluorescence probe was successfully applied to determine the Pb²⁺ ion in real sample analysis. The antimicrobial activity of SNF and PPy-SNF composites was tested against S. aureus, E. coli, and C. albicans. A higher zone of inhibition (ZOI) around the PPy-SNF 5 composite is highly effective against S. aureus and E. coli but less effective against C. albicans. The hemolytic assay proves the PPy-SNF composite was compatible with blood, and the hemolytic (%) was less than 1%. In cytotoxicity assays, the PPy-SNF composite exhibited non-cytotoxic towards peripheral blood mononuclear cells up to 800 µg/ml. Further, molecular docking of the PPy-SNF composite was executed with DNA gyrase. The calculated higher interaction energy towards S. aureus and E. coli. This study delivers dual applications of PPy-SNF composite as an antibacterial agent and Pb²⁺ ion detection in environmental fields.

Graphical Abstract

Graphical representation of sensing, in-vitro, and computational studies of PPy-SNF composite