Enhancement of Antimicrobial Activity of Silver Nanoparticles Using Lasers

Bacterial resistance to antibiotic treatment raises serious public health-related concerns, in parallel with increasing efforts to develop efficient and safe therapeutic alternatives. Silver nanoparticles (Ag-NPs) have been synthesized and enhanced to increase their antibacterial properties using two primary types of lasers. These include the Q-switched Nd:YAG laser and the 405 nm diode laser. The former was used to prepare Ag-NPs colloidal solutions that shown effectiveness against sensitive Staphylococcus aureus, whereas the latter was utilized to activate Ag-NPs against methicillin-resistant S. aureus (MRSA). The approach of this work is to enhance the antibacterial potential of Q-switched Nd:YAG synthesized Ag-NPs against both normal and resistant strains of S. aureus, once by using them in combination with antibiotics and another time by exposing them to 405 nm diode laser. The synthesized silver nanoparticles were characterized by different methods such as UV–Visible, TEM, AFM and zeta potential. These characterizations revealed the formation of AgNPs with sizes in the range from 10 to 30 nm in response to pulsed laser ablation of pure Ag metal plates. The NPs efficiently deactivated S. aureus. The minimum inhibitory concentration (MIC) of AgNPs was 60 µg/ml, which caused a growth inhibition zone with a diameter of 12 mm. A remarkable improvement in antibacterial activity was achieved upon the irradiation of AgNPs with 405 nm laser light, causing a reduction of the MIC to the half (30 µg/ml), even when the treated strain is known to be resistant (MRSA). It is concluded that further enhancement of laser-synthesized AgNPs leads to more powerful antimicrobial impacts that even involve antibiotic-resistant bacteria.