Intracellular Delivery of Quantum Dots for Live Cell Labeling and Organelle Tracking

Abstract

time. This might be a promising antimicrobial coating for a wide range of materials for biomedical or daily-life applications. ExperimentalPEI (MW 5000 g/mol) was purchased from Hyperpolymers (Freiburg, Germany). All other chemicals, if not stated otherwise, were from Fluka and used without further purification. One gram of PEI was suspended in 50 mL acetone and the mixture was cooled to 0 C . Methacryloyl chloride (0.83 mL dissolved in 35 mL acetone) was added dropwise to the stirred suspension within 20 min. After 30 min at 0 C, 150 mL of methanol and 20.4 mL of HEA were added to give a clear solution. The solvents were removed under reduced pressure, the PEI-MA/HEA stock solution was further diluted with HEA to control the PEI content, and 1 mg of the photoinitiator Irgacure 651 (Ciba) was dissolved in 1 mL of the solution. 20 lL of the this mixture was spread on a commercial glass slide previously modified with methacryloyloxy-propyltrimethoxysilane using a standard procedure [20]. The slide was then covered with another glass slide, previously coated with a polypropylene film. The liquid layer between the two slides was UV cured in the UV reactor Heraflash from Heraeus-Kulzer (Hanau, Germany) for 180 s to give a transparent film. The films were then washed with water/methanol/triethylamine (TEA) (1:1:1 v/v/v), water/methanol (1:1 v/v), and water, than immersed in a solution of 250 mg AgNO 3 in 8 mL water for 30 s, washed with water, and finally added to 50 mL of an aqueous solution of ascorbic acid (10 mg mL ±1 ). The modification of the films with PEG was performed as follows: The samples were washed with the water/methanol/TEA mixture, methanol, and acetone, then immersed into a solution of 2 g cyanuric chloride in 10 mL acetone at room temperature overnight, rinsed with acetone and chloroform, and finally left in a solution of 2 g O-2-aminoethyl-O¢-methoxy polyethylene glycol (MW 5000 g/ mol) in 10 mL chloroform for 24 h at room temperature. Prior to use the films were thoroughly rinsed with chloroform and immersed in a large amount of water for at least 24 h.UV-vis measurements were carried out with the photospectrometer Lambda 11 from Perkin Elmer. AFM images were recorded with a Nanoscope III scanning probe microscope using Si cantilevers with a fundamental resonance frequency of around 200 kHz. TEM measurements were carried out using a LEO 912 transmission electron microscope applying an acceleration voltage of 120 kV. The silver content was determined using the flame-atom absorption spectrometer Vario 6 from Analytik-Jena-AG (Jena, Germany).The bacterial susceptibility measurement was carried out according to a modified procedure described earlier [21]. S. aureus (ATCC 25123) cells were cultivated by adding 100 lL of a suspension of the bacterial cells in PBS (10 11 cells/mL) to 50 mL of a standard growth medium from Merck and incubating it under shaking at 37 C for 6 h. The bacterial suspension was then centrifuged at 2750 rpm for 10 min, the cells were washed twice with PBS, pH 7.0, re-suspended in...

Cytosolic Delivery of Nanolabels Prevents Their Asymmetric Inheritance and Enables Extended Quantitative in Vivo Cell Imaging

“…Although it needs to be demonstrated in future research, it could be expected that similar findings on long-term visibility and symmetric inheritance in daughter cells may be obtained with other methods that enable cytosolic delivery of contrast agents. For instance, electroporation could be explored to this end, although it is typically associated with high cell death 53 and for QD it was reported to result in marked aggregation 54 . Also molecular approaches are developed to this end where contrast agents are conjugated to ligands thathopefully -can translocate the contrast agents into the cytoplasm, either directly across the cell membrane or across endosomal membranes after endocytic uptake.…”

Self-Assembled Quantum Dot−Peptide Bioconjugates for Selective Intracellular Delivery

“…In a detailed report, Jaiswal et al demonstrated passive endocytotic uptake of hydrophilic QDs capped with dihydrolipoic acid (DHLA) by incubating HeLa cells with solutions containing QDs at concentrations of 400 -600 nM QDs for 3-4 hours (1). QDs entering cells by this pathway remained largely sequestered within endocytic vesicles for several hours (1,11). Other methods for the cellular uptake of QDs that have been reported include: electroporation (14), cationic transfection reagents (11,15) and microinjection (11).…”

Aqueous phase synthesis of CdTe quantum dots for biophotonics

“…There are a number of strategies to deliver QDs to the cells, namely, transfection [65], electroporation, microinjection, uptake into cells via both targeting [66], and passive pathways are common routes for cell labeling and imaging [67]. In many cases, a targeted approach (e.g.…”