Surface coatings determine cytotoxicity and irritation potential of quantum dot nanoparticles in epidermal keratinocytes

Quantum dot (QD) nanoparticles have potential applications in nanomedicine as drug delivery vectors and diagnostic agents, but the skin toxicity and irritation potential of QDs are unknown. Human epidermal keratinocytes (HEKs) were used to assess if QDs with different surface coatings would cause differential effects on HEK cytotoxicity, proinflammatory cytokine release, and cellular uptake. Commercially available QDs of two different sizes, QD 565 and QD 655, with neutral (polyethylene glycol (PEG)), cationic (PEG-amine), or anionic (carboxylic acid) coatings were utilized. Live cell imaging and transmission electron microscopy were used to determine that all QDs localized intracellularly by 24 hours, with evidence of QD localization in the nucleus. Cytotoxicity and release of the proinflammatory cytokines IL-1 beta, IL-6, IL-8, IL-10, and tumor necrosis factor-alpha were assessed at 24 and 48 hours. Cytotoxicity was observed for QD 565 and QD 655 coated with carboxylic acids or PEG-amine by 48 hours, with little cytotoxicity observed for PEG-coated QDs. Only carboxylic acid-coated QDs significantly increased release of IL-1 beta, IL-6, and IL-8. These data indicate that QD surface coating is a primary determinant of cytotoxicity and immunotoxicity in HEKs, which is consistent across size. However, uptake of QDs by HEKs is independent of surface coating.