In Vitro Prostate Cancer Treatment via CRISPR-Cas9 Gene Editing Facilitated by Polyethyleneimine-Derived Graphene Quantum Dots

CRISPR-Cas9 is a programmable gene editing tool with a promising potential for cancer gene therapy. This therapeutic function is enabled in the present work via the non-covalent delivery of CRISPR ribonucleic protein (RNP) by cationic glucosamine/PEI-derived graphene quantum dots (PEI-GQD) that aid in overcoming physiological barriers and tracking genes of interest. PEI-GQD/RNP complex targeting the TP53 mutation overexpressed in ~50% of cancers successfully produces its double-stranded breaks in solution and in PC3 prostate cancer cells. Restoring this cancer "suicide" gene can promote cellular repair pathways and lead to cancer cell apoptosis. Its repair to the healthy form performed by simultaneous PEI-GQD delivery of CRISPR RNP and a gene repair template leads to a successful therapeutic outcome: 40% apoptotic cancer cell death, while having no effect on non-cancerous HeK293 cells. The translocation of PEI-GQD/RNP complex into PC3 cell cytoplasm is tracked via GQD intrinsic fluorescence, while EGFP-tagged RNP is detected in the cell nucleus, showing the successful detachment of the gene editing tool upon internalization. Using GQDs as non-viral delivery and imaging agents for CRISPR-Cas9 RNP sets the stage for image-guided cancer-specific gene therapy.

Cancer Therapeutic siRNA Delivery and Imaging by Nitrogen- and Neodymium-Doped Graphene Quantum Dots

While small interfering RNA (siRNA) technology has become a powerful tool that can enable cancer-specific gene therapy, its translation to the clinic is still hampered by the inability of the genes alone to cell transfection, poor siRNA stability in blood, and the lack of delivery tracking capabilities. Recently, graphene quantum dots (GQDs) have emerged as a novel platform allowing targeted drug delivery and fluorescence image tracking in visible and near-infrared regions. These capabilities can aid in overcoming primary obstacles to siRNA therapeutics. Here, for the first time, we utilize biocompatible nitrogen- and neodymium-doped graphene quantum dots (NGQDs and Nd-NGQDs, respectively) for the delivery of Kirsten rat sarcoma virus (KRAS) and epidermal growth factor receptor (EGFR) siRNA effective against a variety of cancer types. GQDs loaded with siRNA noncovalently facilitate successful siRNA transfection into HeLa cells, confirmed by confocal fluorescence microscopy at biocompatible GQD concentrations of 375 μg/mL. While the GQD platform provides visible fluorescence tracking, Nd doping enables deeper-tissue near-infrared fluorescence imaging suitable for both in vitro and in vivo applications. The therapeutic efficacy of the GQD/siRNA complex is verified by successful protein knockdown in HeLa cells at nanomolar siEGFR and siKRAS concentrations. A range of GQD/siRNA loading ratios and payloads are tested to ultimately provide substantial inhibition of protein expression down to 31-45%, comparable with conventional Lipofectamine-mediated delivery. This demonstrates the promising potential of GQDs for the nontoxic delivery of siRNA and genes in general, complemented by multiwavelength image tracking.

Mechanism of action and limited cross-resistance of new lipopeptide MX-2401

MX-2401 is a semisynthetic calcium-dependent lipopeptide antibiotic (analogue of amphomycin) in preclinical development for the treatment of serious Gram-positive infections. In vitro and in vivo, MX-2401 demonstrates broad-spectrum bactericidal activity against Gram-positive organisms, including antibiotic-resistant strains. The objective of this study was to investigate the mechanism of action of MX-2401 and compare it with that of the lipopeptide daptomycin. The results indicated that although both daptomycin and MX-2401 are in the structural class of Ca²⁺-dependent lipopeptide antibiotics, the latter has a different mechanism of action. Specifically, MX-2401 inhibits peptidoglycan synthesis by binding to the substrate undecaprenylphosphate (C₅₅-P), the universal carbohydrate carrier involved in several biosynthetic pathways. This interaction resulted in inhibition, in a dose-dependent manner, of the biosynthesis of the cell wall precursors lipids I and II and the wall teichoic acid precursor lipid III, while daptomycin had no significant effect on these processes. MX-2401 induced very slow membrane depolarization that was observed only at high concentrations. Unlike daptomycin, membrane depolarization by MX-2401 did not correlate with its bactericidal activity and did not affect general membrane permeability. In contrast to daptomycin, MX-2401 had no effect on lipid flip-flop, calcein release, or membrane fusion with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (POPG) liposomes. MX-2401 adopts a more defined structure than daptomycin, presumably to facilitate interaction with C₅₅-P. Mutants resistant to MX-2401 demonstrated low cross-resistance to other antibiotics. Overall, these results provided strong evidence that the mode of action of MX-2401 is unique and different from that of any of the approved antibiotics, including daptomycin.