Role of Size and Shape on Biofilm Eradication for Nitric Oxide-Releasing Silica Nanoparticles

Abstract

Nitric oxide (NO), a reactive free radical, has proven effective in eradicating bacterial biofilms with reduced risk of fostering antibacterial resistance. Herein, we evaluated the efficacy of NO-releasing silica nanoparticles against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus biofilms as a function of particle size and shape. Three sizes of NO-releasing silica nanoparticles (i.e., 14, 50, and 150 nm) with identical total NO release (∼0.3 μmol/mg) were utilized to study antibiofilm eradication as a function of size. To observe the role of particle shape on biofilm killing, we varied the aspect ratio of the NO-releasing silica particles from 1 to 8 while maintaining constant particle volume (∼0.02 μm(3)) and NO-release totals (∼0.7 μmol/mg). Nitric oxide-releasing particles with decreased size and increased aspect ratio were more effective against both P. aeruginosa and S. aureus biofilms, with the Gram-negative species exhibiting the greatest susceptibility to NO. To further understand the influence of these nanoparticle properties on NO-mediated antibacterial activity, we visualized intracellular NO concentrations and cell death with confocal microscopy. Smaller NO-releasing particles (14 nm) exhibited better NO delivery and enhanced bacteria killing compared to the larger (50 and 150 nm) particles. Likewise, the rod-like NO-releasing particles proved more effective than spherical particles in delivering NO and inducing greater antibacterial action throughout the biofilm.

The spherical nanoparticle-encapsulated chlorhexidine enhances anti-biofilm efficiency through an effective releasing mode and close microbial interactions

“…6 Moreover, Slomberg et al found that the decreased size and increased aspect ratio could enhance the anti-biofilm efficiency of the NO-releasing silica nanoparticles. 5 However, in our study, W-CHX with wire shape did not show a better anti-biofilm efficiency than S-CHX, partly due to the entanglement of W-CHX that may restrict the release of CHX. The nanoparticle encapsulation per se still improves the anti-biofilm efficiency of CHX.…”

“…1 Previous in vitro and in vivo studies have reported the promising capacity of MSNs as anticancer and antibacterial drug delivery systems. [2][3][4][5][6] Moreover, our group has recently successfully encapsulated the most commonly used antimicrobial agent in dentistry, chlorhexidine (CHX), into commercial MSNs (MCM-41), and further confirmed their antibacterial and anti-biofilm efficiencies via an effective releasing mode. 7 There are plenty of studies on how the nanoparticle morphology, size, and surface modifications affect their interactions with the mammal cells.…”

The antimicrobial activity of nanoparticles: present situation and prospects for the future

“…In addition, bacterial biofilms are "a breeding ground" for frequent resistance mutations and the exchange and alteration of these mutations among different bacterial cells. 15 Studies have shown that many NPs can prevent or overcome biofilm formation, including Au-based NPs, 37 Ag-based NPs, 38 Mg-based NPs, 39 NO NPs, 40,41 ZnO NPs, 7 CuO NPs, Combatting microbes using multiple mechanisms simultaneously…”

Nitric oxide-releasing poly(lactic-co-glycolic acid)-polyethylenimine nanoparticles for prolonged nitric oxide release, antibacterial efficacy, and in vivo wound healing activity

“…15 To date, several NO-releasing NPs such as silica, gold, liposomes, and dendrimers have been developed by taking advantage of nanotechnology and NO. [16][17][18][19][20][21][22] However, these NO-releasing NPs showed an initial burst release probably due to the NO tethering only to the surface of the NPs. This was accompanied by a relatively short duration of NO release ranging from a few to up to 24 hours.…”