Fabrication of Ag nanoparticles coated leonardite basalt ceramic membrane with improved antimicrobial properties for DNA cleavage, E. coli removal and antibiofilm effects

This study aimed to fabricate a novel, low-cost, and environmental-friendly ceramic membrane based on basalt and leonardite powders via press and sintering methods. The fabricated leonardite basalt ceramic membrane (LBCM) was coated with silver nanoparticles (AgNPs); to create an antibacterial surface. The capabilities of the bare and coated membranes were examined. In this context, water permeability reached 554 ± 2.61 and 447 ± 1.21 L/m²hbar for bare LBCM and AgNPs-coated LBCM, respectively. The fabricated membranes indicated 100% Escherichia coli (E. coli) removal efficiency at a transmembrane pressure of 0.5 bar. The solid surface antimicrobial activity of the LBCM and AgNPs-coated LBCM reached 26.38% and 100%, respectively. The LBCM and AgNPs-coated LBCM were analyzed for the in-vitro 2,2- diphenyl-1-picrylhydrazyl (DPPH) antioxidant. Accordingly, AgNPs-coated LBCM exhibited higher antioxidant activities than raw LBCM. The scavenging capacity reached 83.91% with AgNPs-coated LBCM, while only 58.95% was achieved with raw LBCM, indicating that AgNPs-coated LBCM was better than bare LBCM from an antioxidant activities perspective. AgNPs-coated LBCM had a deoxyribonucleic acid (DNA) cleavage activity (single-strand DNA cleavage activity at 50 mg/L and double-strand DNA cleavage activity at 100 and 200 mg/L). In contrast, the raw LBCM did not exhibit DNA cleavage activity at any concentration. AgNPs-coated LBCM showed higher antimicrobial activities (minimum inhibition concentrations (MICs) were 32 mg/L against Enterococcus faecalis (E. faecalis) and 64 mg/L against Staphylococcus aureus (S. aureus), Candida tropicalis (C. tropicalis), and Enterococcus hirae (E. hirae)). The biofilm inhibition of LBCM and AgNPs-coated LBCM powders was tested against S. aureus and Pseudomonas aeruginosa (P. aeruginosa). The maximum S. aureus inhabitations by LBCM and AgNP-coated LBCM were 60.34% and 99.12%, respectively. The inhabitation of P. aeruginosa increased from 52.38% before coating to 96.37% at the end of the coating process. Regarding E.coli microbial cell viability inhibition, LBCM powders and AgNPs-coated LBCM powders were found to inhibit E. coli growth by 68.35% and 100%, respectively.