Owing to the excellent optical and electronic properties of nanocrystals coupled with stability under relatively harsh environment, these have been targeted for various biomedical applications. Biomedical applications require high-quality water-soluble nanocrystals. Quantum dots can be made directly in water but the resulting nanocrystals have narrow available size ranges with wide size distribution that causes wide FWHM. Quantum dots produced at high temperature organic solvent are monodisperse with narrow FWHM, very wide emission color ranging from ultraviolet to near infrared (300–2500 nm) by simply changing the size, omposition and/or structure. But, these quantum dots synthesized in organic solvents are insoluble in water. The same thing can be said for iron oxide magnetic nanoparticles.
Using Ocean’s proprietary method, most hydrophobic, organic ligand-coated nanocrystals can be made soluble in water through the monolayer polymer coating strategy (Figure a). The process allows more than 100 hydrocarbon chains of polymer to interdigitize into the hydrophobic layer of the nanocrystal surface through hydrophobic interaction. This orients the carboxylic acid groups towards to surface converting the nanocrystals into water soluble (hydrophilic), bio-reactive, and stable particles against harsh conditions allowing bioconjugation. The water soluble quantum dots and iron oxide nanocrystals are stable in high salt concentrations (e.g., 3 M sodium chloride) and in a pH range of 1-14. Their shelf-life is at least 1 year at room temperature. Due to the compact nature of this coating, only one polymer layer is coated on the nanocrystal surface. The organic layer (surface ligand and polymer coating) is less than 4 nm in thickness and keeps the nanocrystals highly stable (Figure b). Figure c shows the electrophoresis gel picture of Ocean’s quantum dots at emission wavelength of 550, 580, 600, and 620 nm representing the colors green to red. Figure d demonstrates that the iron oxide nanoparticles show size dependent migration during an agarose gel electrophoresis. Ocean’s proprietary reproducible and scalable process provides very stable water soluble nanocrystals for various research applications. For more information on the research applications of water soluble nanocrystals, please click here. Please find more information about our water soluble nanocrystal products here.