The
substantial increase in multidrug-resistant (MDR) pathogenic
bacteria is a major threat to global health. Recently, the Centers
for Disease Control and Prevention reported possibilities of greater
deaths due to bacterial infections than cancer. Nanomaterials, especially
small-sized (size ≤10 nm) silver nanoparticles (AgNPs), can
be employed to combat these deadly bacterial diseases. However, high
reactivity, instability, susceptibility to fast oxidation, and cytotoxicity
remain crucial shortcomings for their uptake and clinical application.
In this review, we discuss various AgNPs-based approaches to eradicate
bacterial infections and provide comprehensive mechanistic insights
and recent advances in antibacterial activity, antibiofilm activity,
and cytotoxicity (both in vitro and in vivo) of AgNPs. The mechanistic of antimicrobial activity involves four
steps: (i) adhesion of AgNPs to cell wall/membrane and its disruption;
(ii) intracellular penetration and damage; (iii) oxidative stress;
and (iv) modulation of signal transduction pathways. Numerous factors
affecting the bactericidal activity of AgNPs such as shape, size,
crystallinity, pH, and surface coating/charge have also been described
in detail. The review also sheds light on antimicrobial photodynamic
therapy and the role of AgNPs versus Ag+ ions release in
bactericidal activities. In addition, different methods of synthesis
of AgNPs have been discussed in brief.