| Nowadays the control of multidrug resistant (MDR) and pandrug resistant (PDR) bacteria has been the subject
of extensive research. In this study an effective strategywas developed to destroy bacteria using low-level laser
photothermal therapy combined with biocompatible surface-modified AuNPs. First, chitosan, poly(Nisopropylacrylamide)-
co-(2-dimethylamino ethyl methacrylate) P(NIPAAM-co-DMAEMA) and poly(lactic-coglycolic
acid) (PLGA) modified AuNPs were synthesized and fully characterized. Afterwards, P. aeruginosa
and A. baumannii (Two Gram-negative strains of bacteria) were exposed to different doses of low level NIR
laser (810 nm) radiation in the presence or absence of the as-prepared surface-modified AuNPs (in a 1 : 1
ratio) and the killing efficiency of the radiated laser doses was calculated based on pour-plate colony count
for each condition. Chitosan, P(NIPAAM-co-DMAEMA) and PLGA modified AuNPs were synthesized with
a core/shell size of 108, 10 and 120 nm, respectively which was confirmed with DLS and TEM studies.
Successful polymerization and surface coating of AuNPs was confirmed by FT-IR and 1H NMR. A
decreasing trend in the viability of both bacteria was observed along with an increase of the laser dose for
all three types of polymer-coated AuNPs. PLGA@AuNPs exhibited the most effective NIR-induced
photothermal killing on both bacteria. In other words, 10 J cm2 and 30 J cm2 doses were enough to
destroy almost all P. aeruginosa, and A. baumannii, respectively. Our study suggests the usefulness of lowlevel
laser in plasmonic photothermal treatment. The suggested strategy, as a new method of anti-bacterial
intervention, can be used for the eradication of infections such as wound infections in order to accelerate
the healing process. In addition, the offered strategy can be suggested in the treatment of other bio-threats
such as cancerous diseases in vivo |