Formation of Novel Octuplex DNA Molecules from Guanine Quadruplexes

A review of DNA nanoparticles-encapsulated drug/gene/protein for advanced controlled drug release: Current status and future perspective over emerging therapy approaches

In the last ten years, the field of nanomedicine has experienced significant progress in creating novel drug delivery systems (DDSs). An effective strategy involves employing DNA nanoparticles (NPs) as carriers to encapsulate drugs, genes, or proteins, facilitating regulated drug release. This abstract examines the utilization of DNA NPs and their potential applications in strategies for controlled drug release. Researchers have utilized the distinctive characteristics of DNA molecules, including their ability to self-assemble and their compatibility with living organisms, to create NPs specifically for the purpose of delivering drugs. The DNA NPs possess numerous benefits compared to conventional drug carriers, such as exceptional stability, adjustable dimensions and structure, and convenient customization. Researchers have successfully achieved a highly efficient encapsulation of different therapeutic agents by carefully designing their structure and composition. This advancement enables precise and targeted delivery of drugs. The incorporation of drugs, genes, or proteins into DNA NPs provides notable advantages in terms of augmenting therapeutic effectiveness while reducing adverse effects. DNA NPs serve as a protective barrier for the enclosed payloads, preventing their degradation and extending their duration in the body. The protective effect is especially vital for delicate biologics, such as proteins or gene-based therapies that could otherwise be vulnerable to enzymatic degradation or quick elimination. Moreover, the surface of DNA NPs can be altered to facilitate specific targeting towards particular tissues or cells, thereby augmenting the accuracy of delivery. A significant benefit of DNA NPs is their capacity to regulate the kinetics of drug release. Through the manipulation of the DNA NPs structure, scientists can regulate the rate at which the enclosed cargo is released, enabling a prolonged and regulated dispensation of medication. This control is crucial for medications with limited therapeutic ranges or those necessitating uninterrupted administration to attain optimal therapeutic results. In addition, DNA NPs have the ability to react to external factors, including alterations in temperature, pH, or light, which can initiate the release of the payload at precise locations or moments. This feature enhances the precision of drug release control. The potential uses of DNA NPs in the controlled release of medicines are extensive. The NPs have the ability to transport various therapeutic substances, for example, drugs, peptides, NAs (NAs), and proteins. They exhibit potential for the therapeutic management of diverse ailments, including cancer, genetic disorders, and infectious diseases. In addition, DNA NPs can be employed for targeted drug delivery, traversing biological barriers, and surpassing the constraints of conventional drug administration methods.

Ag+-Mediated Folding of Long Polyguanine Strands to Double and Quadruple Helixes

Metal-mediated base pairing of DNA has been a topic of extensive research spanning over more than four decades. Precise positioning of a single metal ion by predetermining the DNA sequence, as well as improved conductivity offered by the ions, make these structures interesting candidates in the context of using DNA in nanotechnology. Here, we report the formation and characterization of conjugates of long (kilo bases) homoguanine DNA strands with silver ions. We demonstrate using atomic force microscopy (AFM) and scanning tunneling microscope (STM) that binding of silver ions leads to folding of homoguanine DNA strands in a "hairpin" fashion to yield double-helical, left-handed molecules composed of G-G base pairs each stabilized by a silver ion. Further folding of the DNA-silver conjugate yields linear molecules in which the two halves of the double helix are twisted one against the other in a right-handed fashion. Quantum mechanical calculations on smaller molecular models support the helical twist directions obtained by the high resolution STM analysis. These long guanine-based nanostructures bearing a chain of silver ions have not been synthesized and studied before and are likely to possess conductive properties that will make them attractive candidates for nanoelectronics.

Programmed Assembly of DNA Templates by Silver Nanowires

DNA origami templates are known to exhibit many advantages to integrate functional components at desirable locations for nanoelectronic applications. In order to immobilize conducting or semiconducting species in a bottom-up approach, the programmed assembly of DNA templates is of utmost necessity. This report demonstrates the silver nanowires enabled bridging of two linear DNA origami (DO) nanostructures by utilizing the host-guest interaction of biotin-STV and sequence-specific silver metallization of poly(dG-dC) DNA nanowires (in 10 % yield) using (dA)₁₀ coated AgNPs (15 nm). The enzymatic synthesis of 750 bp, 1500 bp and 3000 bp bis-biotinylated poly(dG-dC), facile synthesis of 1 : 1 biotin-STV and silver-nanowire bridged DNA templates were characterized by gel electrophoresis, atomic force microscope imaging techniques. The strategy utilized here provides a method that can precisely connect heterogeneous templates towards bottom-up fabrication of practical nanoelectronics.

Electronic Level Structure of Novel Guanine Octuplex DNA Single Molecules

Throughout the past few decades, guanine quadruplex DNA structures have attracted much interest both from a fundamental material science perspective and from a technologically oriented perspective. Novel guanine octuplex DNA, formed from coiled quadruplex DNA, was recently discovered as a stable and rigid DNA-based nanostructure. A detailed electronic structure study of this new nanomaterial, performed by scanning tunneling spectroscopy on a subsingle-molecule level at cryogenic temperature, is presented herein. The electronic levels and lower energy gap of guanine octuplex DNA compared to quadruplex DNA dictate higher transverse conductivity through guanine octads than through guanine tetrads.