BackgroundTargeting stem cells holds great potential for studying the embryonic stem cell and development of stem cell-based regenerative medicine. Previous studies demonstrated that nanoparticles can serve as a robust platform for gene delivery, non-invasive cell imaging, and manipulation of stem cell differentiation. However specific targeting of embryonic stem cells by peptide-linked nanoparticles has not been reported.Methodology/Principal FindingsHere, we developed a method for screening peptides that specifically recognize rhesus macaque embryonic stem cells by phage display and used the peptides to facilitate quantum dot targeting of embryonic stem cells. Through a phage display screen, we found phages that displayed an APWHLSSQYSRT peptide showed high affinity and specificity to undifferentiated primate embryonic stem cells in an enzyme-linked immunoabsorbent assay. These results were subsequently confirmed by immunofluoresence microscopy. Additionally, this binding could be completed by the chemically synthesized APWHLSSQYSRT peptide, indicating that the binding capability was specific and conferred by the peptide sequence. Through the ligation of the peptide to CdSe-ZnS core-shell nanocrystals, we were able to, for the first time, target embryonic stem cells through peptide-conjugated quantum dots.Conclusions/SignificanceThese data demonstrate that our established method of screening for embryonic stem cell specific binding peptides by phage display is feasible. Moreover, the peptide-conjugated quantum dots may be applicable for embryonic stem cell study and utilization.

The present study is aimed at evaluating the effects of luteolin on the scratching behavior associated with an allergic cutaneous reaction in mice. Elicitation of passive cutaneous anaphylaxis, and intradermal injections of compound 48/80, histamine or serotonin induced scratching behavior in ICR mice. Models of irritant contact dermatitis and allergic contact dermatitis were prepared by the topical application of 2,4-dinitrochlorobenzene (DNCB) on the ears of mice. Topical application of luteolin at concentrations of 20 and 100 mug/site significantly inhibited the number of scratching incidents associated with passive cutaneous anaphylaxis, and a similar tendency was also observed in histamine-, serotonin- and compound 48/80-evoked cutaneous reactions. The vascular permeability increase induced by passive cutaneous anaphylaxis or histamine injection was also significantly reduced by luteolin. Luteolin showed a potent inhibition on the ear thickness increase in models of irritant contact dermatitis and allergic contact dermatitis. In conclusion, luteolin significantly inhibited the scratching behavior associated with allergic cutaneous anaphylaxis. Its effects against pruritus are mainly attributed to its inhibition of mediator release from activated mast cells and direct antagonist effects on the released mediators which may act as local pruritogens.

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