Biocompatible Luminescent Silicon Quantum Dots for Imaging of Cancer Cells

Abstract

Luminescent silicon quantum dots (Si QDs) have great potential for use in biological imaging and diagnostic applications. To exploit this potential, they must remain luminescent and stably dispersed in water and biological fluids over a wide range of pH and salt concentration. There have been many challenges in creating such stable water-dispersible Si QDs, including instability of photoluminescence due their fast oxidation in aqueous environments and the difficulty of attaching hydrophilic molecules to Si QD surfaces. In this paper, we report the preparation of highly stable aqueous suspensions of Si QDs using phospholipid micelles, in which the optical properties of Si nanocrystals are retained. These luminescent micelle-encapsulated Si QDs were used as luminescent labels for pancreatic cancer cells. This paves the way for silicon quantum dots to be a valuable optical probe in biomedical diagnostics.

Biocompatibility of Thermally Hydrocarbonized Porous Silicon Nanoparticles and their Biodistribution in Rats

“…These particles exhibited similar size as the 142 nm unlabeled THCPSi (Figure 1a,b). In addition, the THCPSi nanoparticles were also grafted with 18 www.acsnano.org…”

“…23 In this study, 0.5Ϫ1.0 GBq of no-carrier added [ 18 F]fluoride corresponding to less than 0.1 g in mass was used to label a 10000-fold excess of 1 mg of THCPSi nanoparticles. Therefore, radiolabeling of the THCPSi surface with a trace amount of 18 F is unlikely to result in detectable change in the particle size and surface chemistry and, consequently, alterations in the in vivo behavior of the nanoparticles. Most importantly, it can be seen that the labeling of the THCPSi surface with FITC or 18 F did not affect the physicochemical properties of the particles.…”

“…Control animals received 18 F-NaF in the vehicle to establish the biodistribution pattern of free [ 18 F]fluoride in the experimental setup. Administered doses are given in Table 1.…”

“…14Ϫ16 The silicon surface can be treated in the gas phase by oxidation, hydrosilylation, and thermal carbonization, 3 or it can also be grafted with numerous functional moieties, including polyethyleneglycol 17 and folate. 18 Recently, the suitability of thermally hydrocarbonized silicon (THCPSi) microparticles for peptide delivery was demonstrated. 19 The stabilization of PSi with thermal carbonization was used to prevent chemical reactions between the peptide and the PSi surface.…”

Cationic Silicon Nanocrystals with Colloidal Stability, pH‐Independent Positive Surface Charge and Size Tunable Photoluminescence in the Near‐Infrared to Red Spectral Range

“…Steric stabilization strategies typically use long poly(ethylene glycol) chains to achieve colloidal stability. The use of solid lipid nanoparticles by Henderson et al and phospholipid micelles by Erogbogbo et al are prime examples 13, 14, 15. Electrostatic stabilization strategies rely on ionic ligands to prevent flocculation, commonly used ones include olefins with terminal carboxylic acids and terminal primary amines 8, 12, 15, 16, 17, 18, 19, 20.…”