Eradication of Bacteria in Suspension and Biofilms Using Methylene Blue-Loaded Dynamic Nanoplatforms

Abstract

The bacterial killing efficiency of a dynamic nanoplatform (DNP) was evaluated. The polyacrylamide (PAA) hydrogel matrix of the DNP was loaded with methylene blue (MB) and was previously applied successfully to killing rat C6 glioma tumor cells in culture. This series of experiments is aimed at determining the suitability of this nanoplatform for elimination of bacterial infections. Suspended cultures of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter sp. were exposed to activated (ϳ650-nm laser light) MB-PAA-DNPs. The killing efficiency of nanoparticle mass concentration, light irradiance and fluence, and dark incubation time was determined on each of the bacterial species. Moreover, the ability of activated MB-PAA-DNPs to inhibit biofilm growth and eradicate and disperse preformed biofilms, preformed on glass and polystyrene surfaces, was demonstrated. The data revealed that activated MB-PAA-DNPs eradicated all species of bacteria examined. Also, encapsulation of MB into the PAA-DNP matrix significantly diminished the observed dark toxicity of free dye. The photobactericidal efficacy of MB-PAA-DNP was found to be higher for gram-positive bacteria than for gram-negative bacteria. In addition, activated MB-PAA-DNP can inhibit biofilm growth and eradicate almost all of the early-age biofilms that are formed by all of the bacteria examined.

Reduced <em>Staphylococcus aureus</em> biofilm formation in the presence of chitosan-coated iron oxide nanoparticles

“…Treatment of biofilm-related infections requires high doses and long-term use of antibiotics and the resultant inactivation is not always satisfactory. 7 Low concentrations of antibiotics have even been reported to enhance the growth of biofilms. 8,10,11 The chronic infection usually cannot be eradicated unless the implant is removed after various treatments, and this procedure places a large burden on patients and the medical officials.…”

“…6 The main component of PIA is glycosaminoglycans. 7 PIA provides the biofilm with a stable structure, helps the bacteria to adhere to material surfaces, and protects the bacteria embedded in it from being killed by the immune system or antibiotics. 8 Biofilm allows the bacteria to survive in hostile environmental conditions against various environmental stresses, including antibiotic treatment.…”

Current Approaches for Exploration of Nanoparticles as Antibacterial Agents

“…Both standardized and modified microdilution and macrodilution methods have been applied to the determination of MIC and MBC values to evaluate the antimicrobial susceptibility of several microorganisms to nanoparticles [76,109,[110][111][112][113][114][115][116]. Additionally, resazurin staining assay has been employed to determine the MIC.…”

“…Viable plate counts have been frequently performed according to the various protocols to assess the antimicrobial efficacy of nanoparticles against both planktonic and biofilm-growing bacteria [109,128,[110][111][112]116]. Samples can either be spread or pipetted on agar plates followed by overnight incubation and determination of the number of CFUs [116,111,[113][114][115]. Especially, when quantifying the biofilm bacteria, efficient disaggregation of samples is of great importance to avoid false positive results.…”

Non-conventional therapeutics for oral infections

“…Such systems may have better sustainability in the subgingival environment by being taken up into the plaque biofilm. 54 Nanoparticles that contain a conventional sensitizer and have antibacterial action have been known for some time, for example the polysiloxane polymers containing embedded methylene blue and gold nanoparticles described by Perni et al 55 However, more recently similar systems have been developed that are independent of a chemical sensitizer. Chong et al 56 produced nanoparticles of a boron-dipyrromethene polymer that is cationic and that on photoactivation with white light generates ROS at the particle surface.…”