Artificially synthesized functional nucleic acid (Functional Nucleic Acid) has great application potential in the field of biotechnology due to its biocompatibility, relatively simple and mature synthesis method, and its ever-changing nucleotide monomer sequence. In recent years, scientists have designed a series of functional nucleic acids such as aptamers (Aptamer), DNAzymes (DNAZyme), and CpG oligodeoxynucleotides. They are widely used in targeted diagnosis and treatment, catalysis, and immunotherapy.
However, the original or unmodified functional nucleic acid, like another kind of well-known biological molecule polypeptide, has an extremely short half-life in the human body. On the one hand, nuclease (nuclease) is widely present in human cells or tissues, which can cause the hydrolysis of the phosphodiester bond of the functional nucleic acid backbone. On the other hand, the molecular weight of functional nucleic acid is relatively small, and it is easily eliminated by human metabolism. In addition, the nucleic acid backbone exhibits electronegativity and generates mutually repulsive electrostatic effects with the same negatively charged cell membrane. Therefore, nucleic acids often need the help of vectors to enter cells.
Recently, scientists from the University of Florida have jointly developed a new method for synthesizing three-dimensional functional nucleic acid nanomaterials. They used Polymerization Induced Self-Assembly (Polymerization Induced Self-Assembly) to successfully assemble functional nucleic acid molecules on the interface of polymer nanoparticles. Compared with unmodified functional nucleic acid molecules, this new type of functional nucleic acid supramolecular nanomaterials exhibit excellent stability and cell membrane penetration, providing a novel and feasible way for the practical application of functional nucleic acids in the future. The first author of this article is Dr. Lu Yang from the Department of Chemistry, University of Florida.
The author of this article first introduced a chain transfer agent to the end of the functional nucleic acid, and then used the photo-initiated reversible addition-fragmentation transfer polymerization (Photo-RAFT) method to carry out the chain-controlled polymerization of monomeric HPMA in aqueous solution (Figure 1 and Figure 2) . They first studied the assembly behavior of the nucleic acid aptamer Sgc8 in this polymerization system. The author found that as the polymerization reaction progresses, the PHPMA block gradually grows and the water solubility decreases, thereby completing in-situ self-assembly and nucleation. This process forms supramolecular nanoparticles with nucleic acid molecules as the shell and PHPMA polymer as the core. The subsequent polymerization reaction mainly takes place in the hydrophobic PHPMA core. As the degree of polymerization continues to increase, the morphology of Sgc8 nucleic acid nanoparticles has gradually evolved from a basic spherical shape to a rod shape, nanowires, and even vesicle structures. It is worth noting that the author cleverly used glucose oxidase and Glucose eliminates the oxygen in the aqueous system, ensuring the efficient progress of free radical polymerization.
Next, the author systematically studied the stability of Sgc8 nucleic acid polymer nanoparticles in serum, as well as their targeting and membrane penetration capabilities for human acute lymphoblastic leukemia T lymphocytes (CCRF-CEM). They found that the unmodified Sgc8 molecule degraded rapidly in 10% fetal calf serum through gel electrophoresis, and the corresponding bands basically disappeared after twelve hours. In comparison, the stability of Sgc8-PHPMA nanoparticles is significantly higher than that of Sgc8 molecules alone. These nucleic acid nanoparticles still retain a large amount of intact Sgc8 structure after twelve hours or even twenty-four hours (Figure 4A). Next, the authors found that Sgc8-PHPMA nanoparticles retain the specific targeting function of Sgc8 nucleic acid molecules to CCRF-CEM, and their ability to penetrate and enter CEM cells is much stronger than that of Sgc8 alone.
Finally, the author extended this synthetic method to CpG oligodeoxynucleotides, a class of widely used immune enhancers. Similar to the results of the Sgc8 system described above, they successfully prepared CpG-PHPMA nanoparticles with different sizes and morphologies. They found that the stability of CpG-PHPMA nanoparticles in serum, intracellular delivery, and immune enhancement effects are significantly better than that of CpG nucleic acid molecules alone.
In short, this research skillfully applies modern controllable polymerization technology to the structural design of functional nucleic acids, and prepares a series of functional nucleic acid supramolecular nanomaterials with stable structures and excellent performance, which will provide practical applications for such biological materials in the future. A completely new idea.
references:
Lu Yang et al. “Enhancing nucleolytic resistance and bioactivity of functional nucleic acids by diverse nanostructures via in situ polymerization-induced self-assembly”, ChemBioChem, 2020, doi:10.1002/cbic.202000712.
Link to this article:
https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cbic.202000712