Figure 2. Nanoparticle characterization and toxicity screening.

(a) Enhancement factor (EF) for several commonly used dyes shows a strong dependence for size of the Ag core. EF was calculated from the ratio of fluorescence for unetched/etched Ag-NA-dye conjugates. The approximate peak absorption value of the dye is on the x-axis. Error bars = S.D. from replicate wells. OR488, Oregon Green 488; CF dyes from Biotium. (b) Etching kinetics for Ag-NA depends linearly on the concentration and the molar ratio of the etchant components TS:HCF. The decrease in scattering intensity from the Ag plasmon band upon etching was used to calculate a rate, and the time to reach 10% of the initial value is plotted. 1:1 TS:HCF except where indicated, Ag-NA (70 nm core) concentration fixed in all conditions. (c) PPC-1 cells with RPARPAR Ag-NA (R-Ag) and etching showed no effect on 48 h viability (resazurin assay) for short-term exposures to etchant. N=6. Values normalized to the condition of no Ag, no etchant. Ag-NA without peptide, x-Ag, does not internalize into cells. Etchant concentration and duration of contact with cells is indicated. (d) In vivo blood chemistry was evaluated 24 h after x-Ag-NA or etchant injection. Marker levels were not significantly different from those for a PBS control injection, see Supporting Information for additional plots. Error bars = S.D. N=3-6 mice. (e) The etchant was capable of etching pre-injected Ag in mice. Ag was injected into the tail vein then 20 min later followed by either etchant or PBS injection, and blood was analyzed for fluorescence at 60 min. Values were normalized to % of fluorescence at 5 min. Ag had been labeled with CF555 and PEG for blood etching, see Supporting Information. Error bars = S.D., N=2. Terms and units for d: GLOB, globulin g/L; TP, total protein g/L; GLU, glucose mM; BUN, blood urea nitrogen mM; CRE, creatinine μM; TBIL, total bilirubin μM; AMY, amylase units/L; ALT, alanine transaminase units/L; ALP, alkaline phosphatase units/L; ALB, albumin g/L.