Inhibition of biofilm, quorum-sensing, and swarming motility in pathogenic bacteria by magnetite, manganese ferrite, and nickel ferrite nanoparticles

Resistance to antibiotics by pathogenic bacteria constitutes a health burden and nanoparticles (NPs) are being developed as alternative and multipurpose antimicrobial substances. Magnetite (Fe3O4 np), manganese ferrite (MnFe2O4 np) and nickel ferrite (NiFe3O4 np) NPs were synthesized and characterized using thermogravimetric analysis, transmission electron microscopy, Fourier transformed infra-red, and X-ray diffraction. The minimal inhibitory concentrations (MIC) ranged from 0.625 to 10 mg/mL against gram-positive (Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212), gram-negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) and candida (Candida albicans ATCC 10239 and Candida tropicalis ATCC 13803) species. The NPs exhibited violacein inhibition against Chromobacterium violaceum CV12472 of 100% at MIC and reduced to 27.2% ± 0.8% for magnetite NPs, 12.7% ± 0.3% for manganese ferrite NPs and 43.1% ± 0.2% for nickel ferrite NPs at MIC/4. Quorum-sensing (QS) inhibition zones against C. violaceum CV026 were 12.5 ±0.6 mm for Fe3O4 np, 09.1 ± 0.5 mm for MnFe3O4 NP and 17.0 ± 1.2 mm for NiFe3O4 np. The NPs inhibited swarming motility against P. aeruginosa PA01 and biofilm against six pathogens and the gram-positive biofilms were more susceptible than the gram-negative ones. The NiFe2O4 np had highest antibiofilm activity against gram-positive and gram-negative bacteria as well as highest QS inhibition while Fe3O4 NP had highest biofilm inhibition against candida species. The synthesized magnetic NPs can be used in developing anti-virulence drugs which reduce pathogenicity of bacteria as well as resistance.

Antibiofilm and anti-quorum sensing activities of polyethylene imine coated magnetite and nickel ferrite nanoparticles

This study was aimed at synthesizing polyethyleneimine-coated magnetic nanoparticles and evaluating their effect on pathogenic bacteria. Polyethyleneimine-coated magnetite (PEIMnF) and nickel ferrite (PEINF) nanoparticles were succesfully synthesized and their surface groups, morphology and chemical structures were characterized using ATR-FTIR (Attenuated Total Reflectance Fourrier Transformed Infra-Red) and SEM (Scanning Electron Microscopy). TGA (Thermogravimetric analysis) was used to analyse the thermal behaviour and stability of synthesized nanomaterials. The minimal inhibitory concentration (MIC) values of the polyethylene imine coated magnetite and nickel ferrite nanomaterials against Staphylococcus aureus, Escherichia coli and Candida albicans was found to be 10 mg/mL. Both nanomaterials (PEIMnF and PEINF) showed very excellent and concentration-dependent biofilm inhibition especially at the highest test concentration of 10 mg/mL at which PEIMnF inhibited biofilm formation on E. coli (89.04 ± 0.50%), S. aureus (82.85 ± 2.42%) and C. albicans (91.37 ± 0.66%). At this concentration, PEINF equally inhibited biofilm formations of E. coli (90.48 ± 2.05%), S. aureus (87.04 ± 1.59%) and C. albicans (90.94 ± 1.03%). Only PEINF showed a concentration-dependent violacein inhibition with highest inhibition of 51.2 ± 3.5% at MIC and quorum sensing with inhibition zones of 16.3 ± 1.0 mm at MIC and 11.5 ± 0.5 mm at MIC/2 which could be attributed to the presence of nickel. The nanomaterials inhibited swimming and swarming motilities in Pseudomonas aeruginosa PA01 and it was found that at the same concentration, swimming inhibition was greater than swarming inhibitions and PEINF showed better inhibition than PEIMnF in both models. Polyethyleneimine-coated magnetite and nickel ferrite nanomaterials could be used in overcoming health problems associated with microbial infections and resistance.