Antibacterial and Antibiofilm Activities of the Photothermal Therapy Using Gold Nanorods against Seven Different Bacterial Strains

Abstract

The objective of this work was to determine the bactericidal and antibiofilm activities of gold nanorods (AuNRs) using plasmonic photothermal therapy (PPTT) against oral microorganisms. AuNRs were synthesized by the seed and growth solution method and the gold nanoclusters were characterized with a size of 33.2 nm ± 2.23 length and 7.33 nm ± 1.60 width. The efficacy of PPTT related to its temperature was done reaching 67 ∘ C. Minimum inhibitory concentration (MIC) and minimum bactericide concentration (MBC) of AuNRs and AuNRs PPTT were determined against Enterococcus faecalis, Staphylococcus aureus, Streptococcus mutans, Streptococcus sobrinus, Streptococcus oralis, Streptococcus salivarius, and Escherichia coli growth. The antibiofilm activity of AuNRs was explored by fluorescence microscopy. After experimental analyses, AuNRs PPTT shows better results in MICs and MBCs, when it was compared with AuNRs alone. The laser employed to activate the AuNRs had no antibacterial effect against oral microbes. The MICs and MBCs values were higher for S. aureus and E. coli and lower against S. oralis. Surprisingly, the AuNRs alone presented a high antibiofilm activity, inhibiting the biofilm formation of S. mutans. Altogether, these results strongly suggest that AuNRs could be an interesting option to control oral biofilms.

Antibacterial activity of gold nanorods against <em>Staphylococcus aureus</em> and<em> Propionibacterium acnes</em>: misinterpretations and artifacts

“…However, we cannot exclude other hypotheses which support that GNR may pose intrinsic antibacterial activity, since the extra-centrifuged GNR suspensions (GNR 2) still exhibited a considerable antibacterial activity although their MIC values were significantly higher than that of original GNR suspensions. In a recent study, the MIC value of non-functionalized GNR (CTAB-GNR) using 0.2 M CTAB was ∼6.5 μg/mL against S. aureus, 35 which is lower than MIC values of GNR suspensions against S. aureus reported in the current study. These results support our hypothesis of CTAB contribution to the observed antibacterial activity since the concentration of CTAB in the non-functionalized GNR is much higher than that of functionalized GNR.…”

Green Synthesis of Silver Nanoparticles and Their Bactericidal and Antimycotic Activities against Oral Microbes

“…Great advances in nanotechnology have provided a solid foundation for using nanoparticles (NPs) in the fight against pathogen microorganisms, including multidrugresistant bacteria [2,4,5]. Previously the biocidal properties of nanoclusters of several metals have been described, mainly, silver, gold, zinc, titanium, and bismuth [6][7][8][9][10]. Aside from their potential metal nanoparticles present cytotoxicity on human cells, this may occur in all reactive chemicals employed in their synthesis and limiting their use in clinical practice [11][12][13][14].…”

Novel Clinical Trial for Treatment of Infected Subcutaneous Fistula in Female Griffon Dog using Gold Nano-Rod Assisted Near-Infrared Plasmonic Photothermal Therapy

“…That was described previously as the most effective size in the plasmonic photothermal heat generation against bacterial and cancer cells (MacKey, et al, 2014 and Castillo-Martínez, et al, 2015) [38,30]. The previous in vitro bactericidal studies irradiated 1 mL of GnP solution at various concentrations placed in a glass cuvette with approximately one cm bottom surface for 10 minutes, using an 808 or 810 nm wavelength laser with variable output power (up to 2 W/cm2 diode) which was fixed above the surface, approximately 2 cm2, in a vertical position and this dispersion reached a temperature up to 70°C (Mocan, et al, 2014 and Castillo-Martínez, et al, 2015) [32,30]. These conditions are not logically acceptable among the clinical level as this temperature will lead to tissue burn.…”

“…Superficial tissues had numerous small vessels, while larger blood vessels were visible in the deep tissues In the present study, there were two challenges; the first was to achieve bactericidal effect of PPTT against ESβL Klebsiella pneumoniae and the second was enhancement of fistula healing without evidence of hyperthermia side effects on the tissues. Regarding first one, plasmonic photothermal therapy has been extensively investigated (in vitro) as an alternative technique in the biomedical area like determination of its bactericidal and antibiofilm activities against different strains of oral microorganisms (Castillo-Martínez, et al, 2015) [30], using of covalently primary antibodies linked gold nanorods to selectively destroy the pathogenic Gram-negative bacterium, Pseudomonas aeruginosa after exposure to near-infrared radiation (norman, et al, 2008) [31], using surface plasmonic resonance-induced photo-activation of gold nanoparticles as bactericidal agents against methicillin-resistant Staphylococcus aureus (Mocan, et al, 2014) [32], developing a drug delivery platform where gold nanorods (AunRs) are conjugated to rifampicin (RF), which is released after the uptake into macrophage cells (RAW264.7) [22] and studying the action of bactericidal gold nanoparticles on Escherichia coli (Cui, et al, 2012) [33]. In addition to that, a new antibacterial gold nanorod (GnR) conjugated magnetic nanoparticle (MnP) composite (GnR-MnP) was synthesized successfully for the eradication of antibiotic resistant nosocomial pathogens in water to improve the water quality (Ramasamy, et al, 2014) [34].…”