Preparation of zein conjugated quantum dots and their in vivo transdermal delivery capacity through nude mouse skin.

Zein have been successfully conjugated with quantum dots (QD630) via N-(3-dimethylaminopropyl)-N(-ethyl-carbodiimide hydrochloride (EDC) coupling. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements indicated that the average diameter of QD630 was about 5 nm, and that of the zein conjugated QD630 (QD630/Zein) increased to 24 nm. Their size distributions were relatively narrow (Polyindex (PI) < 0.15). The FT-IR and electrophoresis results indicated that QD630 has been combined with zein covalently. Uptakes of QD630 and QD630/Zein by NIH3T3 cells showed different kinetics as observed by fluorescent microscope. There was no obvious increase of fluorescent intensity within cells after 1 h for QD630 sample, while for QD630/Zein, uptake was found to be continuously increased and the major portion of QD630/Zein was localized in the perinuclear area in the form of granular inclusions at 9 h and 24 h. Moreover, penetrating ability of QD630 and QD630/Zein into skin was evaluated with nude mouse in vivo. Fluorescence images revealed that tiny QD630 particles penetrated through the stratum corneum barrier and localized within the epidermal and dermal layers by 8 h, and no QDs was found after 24 h; whereas for QD630/Zein particles, no obvious penetration was observed within 24 hours. Modification of conjugated zein to QDs may alter their skin penetration characteristics and reduce the risk of the QD toxicity.