Distribution of polyethylene glycol coated quantum dots in mice skin.

The distribution of nanoparticles (NP) in an organism is an important issue for developing NP-based drug delivery systems and for general nanotoxicology. The knowledge of NP localisation in the skin is crucial for the optimisation of NP behaviour in vivo. Therefore, we have used semiconductor quantum dots (QD) to investigate their biodistribution in the skin by means of confocal fluorescence microscopy after subcutaneous injection. The results obtained showed that the diffusion of QD in the dermis is limited by basement membrane and dense connective tissue fibres, which resulted in negligible QD penetration into the epidermis, hair follicles, sebaceous and sweat glands, nerves and blood vessels. Low permeation of QD through the tissues results in slow clearance and raises the risks of potential immune, inflammatory and cytotoxic responses. The study reveals the significance of the tissue architecture for the interstitial and intracellular migration patterns of non-functionalised QD.