This release behavior is particularly important when passive targeting mechanism is employed. Drug takes time to reach and act on the site of infection; hence it is very important that it must not be metabolized faster on one hand and should not deposit at nonspecific sites. Cipro@C-dots conjugate would provide an advantage of releasing antibiotic at slower rate, whereby giving longer time to reach at the site of infection and facilitate controlled release. This becomes important since nonspecific

deposition and use of higher concentration of antibiotics lead to microbial resistance to the drug. Cytotoxicity studies showed that C-dots were exceptionally biocompatible on Vero cells under ideal conditions of growth (Figure #GDC 0199 keyword# 7(b)). Table S2 summarizes impact of different concentrations Inhibitors,research,lifescience,medical on C-dots, free ciprofloxacin, and

Cipro@C-dots conjugate on Vero cell lines in terms of percentage viability at various concentrations of test samples. C-dots were found to have negligible impact on Vero cells at all the concentrations (Figure 7(b)). More than 90% cells were found to be healthy after incubation with bare C-dots up to ~80mg mL−1 (Table S2). Free ciprofloxacin was found to be highly inimical than C-dots showing 79% cell viability at its highest concentration Inhibitors,research,lifescience,medical (1.2mM). Cipro@C-dots conjugate was found to be extremely compatible with respect to bare ciprofloxacin. Vero cells showed 93% survival initially which got reduced to 84% at highest concentration having equal concentrations of ciprofloxacin and C-dots as compared to free ciprofloxacin. This may be due to controlled release of antibiotic from C-dots. Figure 7 (a) Drug release profile of Cipro@C-dots conjugate under physiological condition (pH 7.4) displaying time-dependent Inhibitors,research,lifescience,medical controlled release of ciprofloxacin Inhibitors,research,lifescience,medical (error bars represent 5% error) and (b) cytotoxicity of bare C-dots, bare ciprofloxacin, and Cipro@C-dots … Another significant property of C-dots was realized in microbial imaging as shown in Figure 8. Figures S1 and S2 show green fluorescing bare carbon dots and Cipro@C-dots at their

respective concentrations under UV excitation (365nm), respectively. After incubation for 4h with yeast (5 × 107 cells mL−1), the cells showed bright green fluorescence upon excitation Thymidine kinase at 350nm. C-dots were internalized inside the cells (Figure 8(b)) giving excitation dependent green florescence emission. This feature of C-dots can be further used to fabricate molecular tags to view the site of infection when used along with molecular markers on the surface. It would be very interesting to understand the internalization mechanism of C-dots into cells. Figure 8 Bioimaging using fluorescent carbon dots. S. cerevisiae treated with bare C-dots (13mg mL−1) under (a) normal light and (b) fluorescence (λ = 350nm). Antimicrobial activity of bare C-dots, ciprofloxacin, and Cipro@C-dots was performed on two representative gram positive bacteria, B. subtilis and S.