Gene Transfection Efficiency Improvement with Lipid Conjugated Cationic Carbon Dots.

An ideal vehicle with a high transfection efficiency is crucial for gene delivery. In this study, a type of cationic carbon dot (CCD) known as APCDs were first prepared with arginine (Arg) and pentaethylenehexamine (PEHA) as precursors and conjugated with oleic acid (OA) for gene delivery. By tuning the mass ratio of APCDs to OA, APCDs-OA conjugates, namely, APCDs-0.5OA, APCDs-1.0OA, and APCDs-1.5OA were synthesized. All three amphiphilic APCDs-OA conjugates show high affinity to DNA through electrostatic interactions. APCDs-0.5OA exhibit strong binding with small interfering RNA (siRNA). After being internalized by Human Embryonic Kidney (HEK 293) and osteosarcoma (U2OS) cells, they could distribute in both the cytoplasm and the nucleus. With APCDs-OA conjugates as gene delivery vehicles, plasmid DNA (pDNA) that encodes the gene for the green fluorescence protein (GFP) can be successfully delivered in both HEK 293 and U2OS cells. The GFP expression levels mediated by APCDs-0.5OA and APCDs-1.0OA are ten times greater than that of PEI in HEK 293 cells. Furthermore, APCDs-0.5OA show prominent siRNA transfection efficiency, which is proven by the significantly downregulated expression of FANCA and FANCD2 proteins upon delivery of FANCA siRNA and FANCD2 siRNA into U2OS cells. In conclusion, our work demonstrates that conjugation of CCDs with a lipid structure such as OA significantly improves the gene transfection efficiency, providing a new idea about the designation of nonviral carriers in gene delivery systems.

Cancer cells inhibition by cationic carbon dots targeting the cellular nucleus.

Nucleus targeting is tremendously important in cancer therapy. Cationic carbon dots (CCDs) are potential nanoparticles which might enter cells and penetrate nuclear membranes. Although some CCDs have been investigated in nucleus targeting and applied in nuclear imaging, the CCDs derived from drugs, that are able to target the nucleus, bind with DNA and inhibit the growth of cancer cells have not been reported. In this project, 1, 2, 4, 5-benzenetetramine (Y15, a focal adhesion kinase inhibitor) derived cationic carbon dots (Y15-CDs) were prepared via a hydrothermal approach utilizing Y15, folic acid and 1,2-ethylenediamine as precursors. Based on the structural, optical, and morphologic characterizations, Y15-CDs possess rich amine groups and nitrogen in structure, an excitation-dependent photoluminescence emission, and a small particle size of 2 to 4 nm. The DNA binding experiments conducted through agarose gel electrophoresis, UV-vis absorption, fluorescence emission, and circular dichroism spectroscopies, prove that Y15-CDs might bind with DNA via electrostatic interactions and partially intercalative binding modes. In addition, the cell imaging and cytotoxicity studies in human foreskin fibroblasts (HFF), prostate cancer (PC3) and osteosarcoma cells (U2OS) indicate the nucleus targeting and anticancer abilities of Y15-CDs. Most interestingly, Y15-CDs exhibit a higher cytotoxicity to cancer cells (PC3 and U2OS) than to normal cells (HFF), inferring that Y15-CDs might be potentially applied in cancer therapy.

An insight into embryogenesis interruption by carbon nitride dots: can they be nucleobase analogs?

The carbon nitride dot (CND) is an emerging carbon-based nanomaterial. It possesses rich surface functional moieties and a carbon nitride core. Spectroscopic data have demonstrated the analogy between CNDs and cytosine/uracil. Recently, it was found that CNDs could interrupt the normal embryogenesis of zebrafish. Modifying CNDs with various nucleobases, especially cytosine, further decreased embryo viability and increased deformities. Physicochemical property characterization demonstrated that adenine- and cytosine-incorporated CNDs are similar but different from guanine-, thymine- and uracil-incorporated CNDs in many properties, morphology, and structure. To investigate the embryogenesis interruption at the cellular level, bare and different nucleobase-incorporated CNDs were applied to normal and cancerous cell lines. A dose-dependent decline was observed in the viability of normal and cancerous cells incubated with cytosine-incorporated CNDs, which matched results from the zebrafish embryogenesis experiment. In addition, nucleobase-incorporated CNDs were observed to enter cell nuclei, demonstrating a possibility of CND-DNA interactions. CNDs modified by complementary nucleobases could bind each other via hydrogen bonds, which suggests nucleobase-incorporated CNDs can potentially bind the complementary nucleobases in a DNA double helix. Nonetheless, neither bare nor nucleobase-incorporated CNDs were observed to intervene in the amplification of the zebrafish polymerase-alpha 1 gene in quantitative polymerase chain reactions. Thus, in conclusion, the embryogenesis interruption by bare and nucleobase-incorporated CNDs might not be a consequence of CND-DNA interactions during DNA replication. Instead, CND-Ca2+ interactions offer a plausible mechanism that hindered cell proliferation and zebrafish embryogenesis originating from disturbed Ca2+ homeostasis by CNDs. Eventually, the hypothesis that raw or nucleobase-incorporated CNDs can be nucleobase analogs proved to be invalid.