Stöber silica nanoparticle (SSNP) can concentrate methylene blue (MB), an FDA-approved dye for photoacoustic (PA) imaging, for cancer and cell tracking application. However, its negative surface charge reduces their uptake by cells whose membranes are also negative charged. Here, we demonstrate a SSNP that has both a modulated surface potential and a high concentration of MB dye. The size (263±18 nm) and uniformity of SSNP were measured under transmission electron microscope (Figure a). The surface potential of SSNP, originally -41 mV, changed to 24 mv and -31 mV by coupling with (3-aminopropyl)triethoxysilane (APTES) and (3-mercaptopropyl)trimethoxysilane (MPTMS), respectively (i.e. SSNP-NH2 and SSNP-SH). Unmodified SSNP offers 48-fold and 2-fold better loading efficiency than SSNP-NH2 and SSNP-SH, respectively. All three samples were incubated in 0.8 mM MB overnight and washed 3 times (i.e. SSNP-NH2+MB, SSNP-SH+MB, SSNP+MB). Vis-NIR spectra showed that 1 mg/ml SSNP can capture at least 3 nM MB, and all SSNPs showed stable and only negligible MB release (&lt;12 %) after the third wash. The SSNPs were prepared in small tubing placed in parallel for ultrasound and PA scanning, respectively. Figures b shows the ultrasound (grey) and PA (red) signal. The PA signal of SSNP+MB is 2.5 times and 1000 times higher than SSNP-NH2+MB and SSNP-SH, respectively.

Stöber silica nanoparticles can concentrate methylene blue for a charge-tunable photoacoustic imaging agent

251st National Meeting (2016)

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