28 log (47%) reduction in total viable cells compared to the control samples (bacteria only). THCPSi NPs that were not loaded with NO applied at the same concentration

produced a negligible reduction in the biofilm density, indicating that the NO released from the prepared NO/THCPSi NPs was the primary cause of any antimicrobial action. In comparison with the high doses of NO donor silica NPs reportedly required for the treatment of S. epidermidis selleck chemical biofilms [22], the sugar-mediated NO/THCPSi NPs showed effective biofilm reduction at a fractional dose. Cytotoxicity of NO/THCPSi NPs to NIH/3T3 fibroblast cells The biocompatibility of THCPSi NPs has been previously reported by Santos and co-workers [25, 28], where cytotoxicity, oxidative, and inflammatory responses were studied for a variety of mammalian cell lines. The toxicity

of NO/THCPSi NPs, glucose/THCPSi NPs, and THCPSi NPs at different concentrations (0.05 to 0.2 mg/mL) over 48 h was evaluated using the NIH/3T3 cell line, which is one of the most commonly used fibroblast cell lines and often used as a model for skin cells. Two viability assays were used for toxicity studies: LDH and fluorescein NU7441 mw diacetate-propidium iodide (FDA-PI). As shown in Figure 6, the Alvocidib results from the LDH assay showed well over 90% viability for all NP types up to 0.1 mg/mL. However, increasing the concentration of NO/THCPSi NPs to 0.2 mg/mL reduced the viability of NIH/3T3 cells to 92%. In contrast, the viability of fibroblast cells incubated with glucose/THCPSi NPs and THCPSi NPs at 0.15 and 0.2 mg/mL remained over 95%. The results of the FDA-PI assay (Additional file 1: Figure S3) were consistent with those obtained using the LDH assay. Figure 6 Toxicity of the NPs to NIH/3T3 fibroblasts using the LDH assay after 48-h incubationc NO/THCPSi NPs (red bars), glucose/THCPSi NPs (blue bars), and THCPSi NPs (yellow bars). Viability measures normalized to no NP control samples (n = 3; mean ± standard deviation shown). The cytotoxicity

of THCPSi NPs has been reported to be concentration dependent [25, 27], and increased very concentrations of NO/THCPSi NPs did raise cytotoxicity. However, the cytotoxicity of THCPSi NPs on fibroblast cells is much less than observed for silica NPs, silver NPs, and other clinical antiseptic wound treatments [3, 11, 44, 45]. We note that dosage optimization (e.g., concentration of 0.1 mg/mL) enables a balance between high antibacterial efficacy and low toxicity towards mammalian cells present in a wound environment to be achieved. Conclusions The present work demonstrates the capacity of THCPSi NPs to be loaded with NO by utilizing the sugar-mediated thermal reduction of nitrite. These NO/THCPSi NPs possess the capacity to deliver NO at therapeutic levels in a more sustained manner than previously demonstrated using NO-releasing NPs. NO delivered from the NPs was effective at killing pathogenic P. aeruginosa, E. coli, and S. aureus after only 2 h of incubation.