## 4 Antibacterial Nanotheranostics
### Theranostic Nanoparticles (NPs) and Nanofibers
#### 4.1.2 Nanoparticle-Mediated Therapeutic Antibacterial and Antibiofilm Actions
Our previous study has pointed toward the extensive different mechanistic antibacterial actions of Ag NPs and Ag\({}^{+}\) ions and concluded that Ag NP shots mainly damage the bacterial membranes, whereas Ag\({}^{+}\) ions mainly target bacterial DNA [158]. A more recent review was dedicated to referring to these substantial differences and similarities between the antibacterial mechanisms of Ag NP shots and Ag\({}^{+}\) ions. The review extended to shape the formula that not only are the antibacterial mechanisms different, but the bacterial resistance mechanisms against Ag NP shots and Ag\({}^{+}\) ions would also be different [162]. Would there be antibacterial properties related to the shape of NP shots? [PERSON] et al. [168] have highlighted the role of geometric structures (sharp edges and vertices) of triangular silver nanoprisms (broad size range of 25 to 400 nm) in the more prominent antibacterial effects compared with the spherical NPs (even with smaller average sizes of 21 nm). The sharp vertices of Ag nanoprisms disrupt the bacterial membranes, easing the penetration of more Ag prisms into the bacterial cells. In a leading article devoted to stress on the shape-dependent antibacterial effects of AgNPs [160], truncated triangular silver nanoplates with [111] lattice planes showed the best antibacterial effects against _E. coli_ among other shapes of Ag NPs (spheres and rods) and even Ag\({}^{+}\) ions. The authors also mentioned the sharing of the [111] lattice planes of the truncated triangular nanocrystals in their best antibacterial properties because of the high-atom-density [111] facets, enabling more reactivity with the bacterial cells. Similar effects of sharp edges have been echoed as damaging of bacterial membranes and killing of _S. aureus_ and _E. coli_ upon direct contact with the extremely sharp edges of the graphene oxide nanowalls. The nanowalls killed more _S. aureus_ than _E. coli_, possessing other outer membrane protection against the damage [169]. Finally, what antib Biofilm mechanisms might Ag NP shots or NP shots employ in general? Unfortunately, researchers have not studied the interactive mechanisms of NPs with biofilms in much detail. There has also been a controversy between scholars regarding experimental results. Some observers attributed the antibofilm effects of NPs to the same broad antibacterial mechanisms of NPs (i.e., oxidative stress via ROS, the release of metal ions, and non-oxidative stress). However, this broad concept has been debated by other studies arguing more intricate interactive mechanisms between NPs and biofilms, taking into consideration the formation and architecture of biofilms [170]. [PERSON] et al. [171] identified the retention of catalytic iron oxide NPs within the biofilm architecture of _Streptococcus mutans_. Catalytic NPs activated the co-administered hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) rapidly under acidic conditions (pH 4.5 to 5.5), mimicking the pH within biofilms and producing in situ free radicals that concurrently degraded the EPS of biofilms and killed the bacterial cells embedded within their biofilms. [PERSON] et al. [172] investigated the antib biofilm effects of Ag NPs and Ag-Fe\({}_{3}\)O\({}_{4}\) nanocomposites against _S. aureus_ biofilms in chronic wounds. The most striking result of their investigation is that the nanocomposites were uniformly distributed within the collagen gel matrix containing deeply embedded biofilms, and _S. aureus_ biofilms were eradicated following the administration of the magnetic field, pushing the nanocomposites within the collagen matrix. Meanwhile, Ag NPs could not eradicate _S. aureus_ biofilms, despite releasing more Ag\({}^{+}\) ions and producing more ROS than the nanocomposites. They finally suggested that the antib biofilm mechanisms of their nanocomposites remain murky. [PERSON] et al. [173] have shed light on the molecular antib biofilm mechanisms of Ag NPs immobilized in situ on titanium.