Quantum dots synthesized on DNA for infrared biological imaging

摘要

Quantum dot nanocrystals have been used to label single molecules during living-cell assays and provide direct visual guidance and real-time confirmation of complete resection during cancer surgery in an animal model. The use of quantum dots for deep tissue imaging accompanied by low autofluorescence in vivo requires emission in the second infrared biological window 1000-1200 nm, combined with stability in biologial media. Surface chemistry determines the chemical and optical stability of quantum dots. A stabilizing outer shell minimises diffusion of oxygen to the surface of the core of the nanoparticle, as demonstrated using a high-bandgap semiconductor shell and a dielectric shell. Silanized nanoparticles have been shown to be water-soluble and to retain the absorption and emission spectra of the original particles; however, the nanoparticles lost 60-80% of their original quantum efficiency in this process. Recently, oligomeric phosphines have been employed to form three thin concentric sublayers around quantum dots: an inner phosphine layer for dot surface passivation; a linking layer for protection; and an outer functionalized layer for miscibiliry and subsequent chemical modification or conjugation to biomolecules. In the infrared, this multistep synthetic method, applied to type-Ⅱ core-shell nanoparticles, has resulted in quantum dots which show modest degradation in 37℃ plasma over the course of half an hour.