Synthesis of functionalized gold nanoparticle and study of the antibacterial effect on gram negative pathogenic bacteria via photothermal therapy

Abstract

Control of the multi-drug resistant and sometimes pan-drug resistant bacteria (super bugs) have been the subject of extensive research to overcome and control it. Different methods are used to eliminate such bacteria, mostly through anti-biotic therapy. Nevertheless, most antibiotics loss their efficiency duo to the advent of drug-resistant bactericidal strains. Therefore, in the present study, we report development of an effective strategy to destroy bacteria isolate in an efficient, safe, targeted and rapid manner-using low-level laser photothermal therapy combined with biocompatible AuNPs. Method: First, chitosan, DMAEMA-co-NIPAAM, PLGA were coated on AuNPs and the resultant polymer-AuNPs were characterized. Afterwards, P. aeruginosa and A. baumannii were exposure to different doses of low level NIR laser (810nm) in the presence or absence of the as-prepared surface-modified AuNPs (in a 1:1 ratio) and the killing efficiency of the laser was calculated based on pour-plate colony count for each condition. Result: the synthesized polymer modified AuNPs showed high stability and dispersing with a core/shell size of 108, 10 >, 120 nm for chitosan, DMAEMA-co-NIPAAM and PLGA –AuNPs, respectively. FT-IR and 1HNMR confirmed successful polymerization of the polymers on surface of AuNPs. A decreasing trend in the viability of both bacteria was observed along with increasing of the laser dose for all three types of polymer-coated AuNPs. Chitosan-AuNPs showed more intense photothermal killing of P. aeruginosa (32% viability) compared with A. baumannii (47% viability). DMAEMA-co-NIPAAM-AuNPs could destroyed higher percentage of both bacteria when recived 70J energy density (almost 0% viability for P. aeruginosa and 15% viability for A. baumannii). PLGA-AuNPs exhibited the most effective NIR-induced photothermal killing on both bacteria. In other words, a 10J dose was enough to destroy almost all P. aeruginosa, however, we observed the same result for A. baumannii in 30J dose. Conclusion: among three types of polymer-coated AuNPs, chitosan-AuNPs and PLGA-AuNPs were least and most effective photothermal agent, respectively. Our study suggests the usefulness of low-level laser in plasmonic photothermal treatment. Regarding the results, the offered strategy can be used in treatment of various bio-threats such as pan-drug-resistant infections and cancerous diseases.