Abstract
Anisotropic gold nanoparticles, especially gold nanostars, are used in many fields of biomedical applications such as sensing, targeted drug delivery, and diagnostic and photothermal therapy. In this study, we introduced a novel application of gold nanostars as an antimicrobial agent. While spherical gold nanoparticles have an inappreciable effect, gold nanostars exhibit significant antibacterial activity. Besides, the seed-mediated method, a conventional technique for preparing gold nanostars, is rather complex and toxic to human and environment due to unsafe synthesized materials such as surfactants and reducers. In recent years, green chemistry for nanoparticle synthesis is attractive because of its advantages. Instead of the seed-mediated procedure, we present a facile and green procedure to synthesize gold nanostars using ascorbic acid as a reductant and chitosan as a directing-growth agent. The influences of reacting parameters were evaluated to determine the optimal conditions. Star-shaped gold nanoparticles were successfully synthesized with average size tunning from 137.0 ± 20.7 nm to 281.9 ± 25.8 nm of the core and 14.0 ± 4.4 nm to 54.2 ± 11.9 nm of branches. Antibacterial activity against Propionibacterium acnes of gold nanostars was also investigated. Propionibacterium acnes is one of the main reasons causing acne vulgaris. The antibacterial test was evaluated by the plate count and well diffusion method. The results showed a significant effect that gold nanostars could be the prospective agent for replacing antibiotics in acne treatment.
Highlights
Acne vulgaris is one of the most popular chronic inflammatory dermatological problems affecting around 10% of the global population [1]
Surface resonance plasmon (SPR) of gold nanostars (GNS) consists of two absorption bands ranging from 500 to 900 nm, including a weaker peak at 500–575 nm referring to the core and an intense band in the NIR region (SPRmax) ranging from 600 to 1200 nm referring to the branches of GNS [56]
It was clear that the intensity of SPRmax increased according to the decreasing pH from 3.73 while absorption locations were almost stable at 871 nm
Summary
Acne vulgaris is one of the most popular chronic inflammatory dermatological problems affecting around 10% of the global population [1]. Nanotechnology and nanomaterials are prospective methods for replacing conventional acne treatment [16, 17] Antimicrobial metallic nanoparticles such as noble- (copper, silver, and gold) [18,19,20], oxide- (zinc oxide, magnesium oxide, and tin oxide) [21,22,23], and carbon-based nanoparticles (carbon nanotube, graphene) [23, 24] were attractive and studied by researchers in several years. Green chemistry becomes a common trend in many fields of chemistry and materials [40] including nanomaterial synthesis [41] This technology uses safe agents derived from nature for replacing toxic materials as well as applying low-cost and energy-efficient equipment [42]. The mechanism that GNS killed bacteria was identified by SEM observation using simple preparation without any fixative and dehydrating step
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