Chirality of Glutathione Surface Coating Affects the Cytotoxicity of Quantum Dots

Reversing the Chirality of Surface Ligands Can Improve the Biosafety and Pharmacokinetics of Cationic Gold Nanoclusters

Severe toxicity and rapid in vivo clearance of cationic nanomaterials seriously hinder their clinical translation. Present strategies to improve the biosafety and in vivo performance of cationic nanomaterials require neutralization of positive charge, which often compromises their efficacy. Herein, we report that substituting L-glutathione (L-GSH) on cationic gold nanoclusters (GNCs) with its D-counterpart can effectively improve the biosafety and pharmacokinetics. Compared with L-GNCs, D-GNCs do not exhibit cellular cytotoxicity, hemolysis, or acute damage to organs. Cationic D-GNCs show less cell internalization than L-GNCs, and do not induce cellular apoptosis. In vivo, the chirality of surface ligands distinctly affects the pharmacokinetics and tumor targeting abilities of D-/L-GNCs. D-GNCs show higher extended circulation time in blood plasma compared to similarly-sized and poly (ethylene glycol)-modified gold nanoparticles. This work demonstrates that the choice of chirality of surface ligands can determine toxicities and pharmacokinetics of cationic nanomaterials.

Surface-anchored poly(acryloyl-L(D)-valine) with enhanced chirality-selective effect on cellular uptake of gold nanoparticles

Chirality is one of the ubiquitous phenomena in biological systems. The left handed (L-) amino acids and right handed (D-) sugars are normally found in proteins, and in RNAs and DNAs, respectively. The effect of chiral surfaces at the nanoscale on cellular uptake has, however, not been explored. This study reveals for the first time the molecular chirality on gold nanoparticles (AuNPs) functions as a direct regulator for cellular uptake. Monolayers of 2-mercaptoacetyl-L(D)-valine (L(D)-MAV) and poly(acryloyl-L(D)-valine (L(D)-PAV) chiral molecules were formed on AuNPs surface, respectively. The internalized amount of PAV-AuNPs was several times larger than that of MAV-AuNPs by A549 and HepG2 cells, regardless of the chirality difference. However, the D-PAV-AuNPs were internalized with significantly larger amount than the L-PAV-AuNPs. This chirality-dependent uptake effect is likely attributed to the preferable interaction between the L-phospholipid-based cell membrane and the D-enantiomers.

DNA nanoflowers for multiplexed cellular imaging and traceable targeted drug delivery

We present a facile approach to make aptamer-conjugated FRET (fluorescent resonance energy transfer) nanoflowers (NFs) through rolling circle replication for multiplexed cellular imaging and traceable targeted drug delivery. The NFs can exhibit multi-fluorescence emissions by a single-wavelength excitation as a result of the DNA matrix covalently incorporated with three dye molecules able to perform FRET. Compared with the conventional DNA nanostructure assembly, NF assembly is independent of template sequences, avoiding the otherwise complicated design of DNA building blocks assembled into nanostructures by base-pairing. The NFs were uniform and exhibited high fluorescence intensity and excellent photostability. Combined with the ability of traceable targeted drug delivery, these colorful DNA NFs provide a novel system for applications in multiplex fluorescent cellular imaging, effective screening of drugs, and therapeutic protocol development.

The application of CdSe quantum dots with multicolor emission as fluorescent probes for cell labeling

Herein, highly luminescent CdSe quantum dots (QDs) with emissions from the blue to the red region of visible light were synthesized by using a simple method. The emission range of the CdSe QDs could be tuned from λ=503 to 606 nm by controlling the size of the CdSe QDs. Two amino acids, L-tryptophan (L-Trp) and L-arginine (L-Arg), were used as coating agents. The quantum yield (QY) of CdSe QDs (green color) with an optimized thickness could reach up to 52 %. The structures and compositions of QDs were examined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Optical properties were studied by using UV/Vis and photoluminescence (PL) spectroscopy and a comparison was made between uncoated and coated CdSe QDs. The amino acid-modified β-cyclodextrin (CD)-coated CdSe QDs presented lower cytotoxicity to cells for 48 h. Furthermore, amino acid-modified β-CD-coated green CdSe QDs in HepG2 cells were assessed by using confocal laser scanning fluorescence microscopy. The results showed that amino acid-modified β-CD-coated green CdSe QDs could enter tumor cells efficiently and indicated that biomolecule-coated QDs could be used as a potential fluorescent probe.