Efficient intracellular delivery of quantum dots (QDs) in living cells and elucidating the mechanism of the
delivery are essential for advancing the applications of QDs to in vivo imaging and in vivo photodynamic therapy. Here,
we demonstrate that clathrin-mediated endocytosis is the most dominant pathway for the delivery of peptide-conjugated
QDs. We selected an insect neuropeptide, allatostatin (AST1), conjugated with CdSe-ZnS QDs, and investigated the
delivery of the conjugate in living cells. We evaluated the contributions of clathrin-mediated endocytosis, receptormediated
endocytosis, and charge-based cell penetration to the delivery of QD605-AST1 conjugates by flow cytometry
and fluorescence video microscopy. The delivery was suppressed by ~57% in inhibiting phosphoinositide 3-kinase with
wortmannin, which blocks the formation of clathrin-coated vesicles, and by ~45% in incubating the cells at 4°C. Also,
we identified clathrin-mediated endocytosis by two-color experiment to find colocalization of QD560-labeled clathrin
heavy-chain antibody and QD605-AST1. We further observed reduction of the galanin receptor-mediated delivery of
QD605-AST1 by ~8% in blocking the cells with a galanin antagonist, and reduction of charge-based cell penetration
delivery by ~30% in removing the positive charge in the peptide from arginine and suppressing the cell-surface negative
charge from glycosaminoglycan.
Laser manipulation is an important technique suitable for controlling objects in liquid at length scales ranging from
sub-micrometers to micrometers. However, the use of this technique by itself is not enough to dexterously or automatically
manipulate objects. In this article we propose a concept for automated non-contact micro-manipulation combined with
laser manipulation and advanced control system techniques, and describe the configuration of a developed system, i.e. a
three-beam laser trapping system with excellent user-interfaces, real-time image processing functions and a micro-laser
ablation beam. We also show the results of several demonstrations; namely the arrangement of metallic particles, the
manipulation of a non-spherical object, the laser perforation of a cell, and the automated selection and transportation of
colored micro beads.
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