A Chimeric Peptide-Carbon Quantum Dot Nanobiohybrid System for Gene Delivery to Macrophage Cells

Nanobiohybrid systems are innovative platforms that integrate biological macromolecules with nanomaterials to form hybrid structures. These systems have diverse applications, including gene delivery, cancer therapy, drug delivery, biosensing, and diagnostics. Specifically, for gene delivery, nanobiohybrid systems are designed to improve the transport of genetic material to target cells by protecting the material, enabling its passage across biological barriers, and accurately targeting specific cells. Here, a targeted gene delivery system based on the mannosylated carbon quantum dots (Man-CQDs) and a chimeric peptide (Pep) was developed to condense and deliver DNA into the antigen presenting cells. The nanobiohybrid complex formation was studied by spectroscopic methods, microscale thermophoresis (MST), dynamic light scattering, transmission electron microscopy, and gel retardation assay. The blue-emitting Pep/DNA/Man-CQDs nanohybrids exhibited a size of 16 ± 2 nm and a zeta potential of - 12.6 mV. Molecular dynamics simulations revealed that Man-CQDs preferentially interact with DNA within the Pep/DNA complex, supporting MST results which confirmed binding between Man-CQDs and the Pep/DNA complex (Kd = 15.6 µM), but not with the peptide alone. Gene transfection efficiency of the developed nanobiohybrid system was confirmed on J744A.1 macrophages. Additionally, MD simulations of the Pep/DNA/Man-CQDs complex revealed that Man-CQDs predominantly bind to the DNA component, primarily through π-π interactions between Man-CQDs and the unsaturated (poly)cyclic moieties in GC-rich regions of the DNA. The interactions between the chimeric peptide and DNA are largely driven by electrostatic forces, with coulombic energy being 3.9-fold higher than noncoulombic energy. These forces arise from the positively charged amino acids of the peptide and the negatively charged backbone of the DNA.