## 3 Results
### Antimicrobial Efficacy Evaluation of Ag7 NO11:SiO2  
Silver oxynritate is known as a potent antimicrobial agent against planktonic, biofilm, and drug resistant bacterium [16; 17; 18]. Modification of the form or function of silver oxynritate may result in an impairment of this antimicrobial activity. Therefore, it is imperative to determine the impact of synthetic modifications on the efficacy of silver oxynritate. Towards this, a series of antimicrobial methodologies were employed to evaluate the efficacy of silver oxynritate and Ag7 NO11:SiO2 against both planktonic and biofilm states of _Staphylococcus aureus_ (ATCC 6538) and _Pseudomonas aeruginosa_ (ATCC 9027).  
Figure 6: Powder X-ray diffraction patterns of (**A**) silver oxynritate (Ag7 NO11) and; (**B**) Ag7 NO11-SiO2 containing 0.10:1, SiO2:Ag, equivalents silica over a seven-day period in an aqueous solution at room temperature. Solid-state silver compounds were identified as silver oxynritate (Ag7 NO11, inverted red triangles), silver sulfate (Ag2 SO4, green circles), and argentic oxide (AgO, blue squares).  
Figure 7: Scanning electron microscopy images of silver oxynritate and Ag7 NO11:SiO2 containing 0.1:1, SiO2:Ag, exposed to aqueous media for a period of seven days. Silver oxynritate (Ag7 NO11) (**A**) prior to aqueous exposure; (**B**) after 24 h of exposure to aqueous media; and (**C**) after 168 h of exposure to aqueous media. Ag7 NO11:SiO2 containing 0.1:1, SiO2:Ag (**D**) prior to aqueous exposure; (**E**) after 24 h of exposure to aqueous media; and (**F**) after 168 h of exposure to aqueous media.  
Single time point log reduction of Gram-positive _S. aureus_ (4 h) and Gram-negative _P. aeruginosa_ (1 h) were evaluated in Mueller Hinton Broth (MHB) inoculated to a concentration of \(1\times 10^{6}\) CFU/mL. The efficacy of silver oxynitrate and Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) containing 0.1:1 SiO\({}_{2}\):Ag were evaluated at normalized silver concentration. Following treatment, the remaining bacteria were numerated and log reduction quantified versus untreated control. The efficacy of Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) was compared with silver oxynitrate and was found to be equivalent for both organisms tested (_p_ value \(>\) 0.05), as shown in Figure 8A.  
The role of biofilm in infection and delayed wound healing is becoming increasingly evident [33; 34; 35]. Using a clinically relevant biofilm model, adapted from literature, we evaluated the capacity of silver oxynitrate and Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) containing 0.1:1 SiO\({}_{2}\):Ag to target and reduce biofilm [17; 36]. In brief, established biofilms of _P. aeruginosa_ and _S. aureus_ were treated with silver oxynitrate or Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\). Following a 2-h and 4-h treatment period for _P. aeruginosa_ and _S. aureus_ respectively, viable cells were recovered and numerated versus untreated control to determine log reduction values. Silver oxynitrate and Ag\({}_{7}\)NO\({}_{11}\):SiO\({}_{2}\) were found to equivalently reduce viable biofilm counts (_p_ value \(>\) 0.05), as shown in Figure 8B. In comparison with silver oxynitrate, no hindrance of antibacterial or antib Biofilm activity was observed with the incorporation of silver oxynitrate to the silicon dioxide framework through the described co-deposition procedures.