Self-Assembled DNA Nanospheres Driven by Carbon Dots for MicroRNAs Imaging in Tumor via Logic Circuit.

DNA nanostructures with diverse biological functions have made significant advancements in biomedical applications. However, a universal strategy for the efficient production of DNA nanostructures is still lacking. In this work, a facile and mild method is presented for self-assembling polyethylenimine-modified carbon dots (PEI-CDs) and DNA into nanospheres called CANs at room temperature. This makes CANs universally applicable to multiple biological applications involving various types of DNA. Due to the ultra-small size and strong cationic charge of PEI-CDs, CANs exhibit a dense structure with high loading capacity for encapsulated DNA while providing excellent stability by protecting DNA from enzymatic hydrolysis. Additionally, Mg2+ is incorporated into CANs to form Mg@CANs which enriches the performance of CANs and enables subsequent biological imaging applications by providing exogenous Mg2+. Especially, a DNAzyme logic gate system that contains AND and OR Mg@CANs is constructed and successfully delivered to tumor cells in vitro and in vivo. They can be specifically activated by endogenic human apurinic/apyrimidinic endonuclease 1 and recognize the expression levels of miRNA-21 and miRNA-155 at tumor sites by logic biocomputing. A versatile pattern for delivery of diverse DNA and flexible logic circuits for multiple miRNAs imaging are developed.

Label-free and sensitive detection assay for terminal deoxynucleotidyl transferase via polyadenosine-coralyne fluorescence enhancement strategy.

Terminal deoxynucleotidyl transferase (TdT) is a unique template-free polymerase that randomly adds multiple deoxyribonucleoside triphosphates (dNTPs) to the 3'-OH terminus of ssDNA. This characteristic makes TdT a versatile enzymatic tool in many fields. Moreover, aberrant TdT expression is a well-recognized biomarker of several leukemic diseases and is related to carcinogenesis. In this study, we developed a facile, rapid, label-free, and convenient assay for TdT detection. TdT-generated poly A tails formed a fluorescent enhancement complex in the presence of coralyne. To achieve a better signal-to-noise ratio, we used potassium thiocyanate (KSCN), instead of other halogen anions (KCl, KBr, KI, NaI) as the quenching agent of dissociate coralyne. Our results demonstrate that this assay is extremely facile, rapid, and label-free; at levels as low as 0.025 U/mL, TdT was distinctly detected within 55 min. And the determination of TdT activity in RBL-2H3 and Reh cells lysates exhibited a good sensing performance, demonstrating its potential applications in biochemical research and clinical diagnosis.

A novel DNA biosensor integrated with Polypyrrole/streptavidin and Au-PAMAM-CP bionanocomposite probes to detect the rs4839469 locus of the vangl1 gene for dysontogenesis prediction.

The single nucleotide polymorphism (SNP) of the vangl1 gene is highly correlated with Neural Tube Defects (NTDs), a group of severe congenital malformations. It is hindered by the lack of a quantitative detection method. We first propose the use of a DNA biosensor to detect the missense single nucleotide polymorphism (rs4839469 c.346G>A p.Ala116Thr) of the vangl1 gene in this work. Polypyrrole (PPy) and streptavidin were integrated to modify a gold electrode. We took advantage of the PPy's good biocompatibility and excellent conductivity. To further accelerate the electron transfer process at the electrode surface, polyamidoamine dendrimer-encapsulated gold nanoparticles (Au-PAMAM) were used, because Au-PAMAM possess a large number of amino groups to load capture probes (CP). Using the biotin-streptavidin system, the Au-PAMAM-CP bionanocomposite probe, which can detect the target DNA, was conjugated to the electrode surface. Under optimal conditions, the DNA biosensor exhibited a wide linear range of 0.1-100 nM with a low detection limit of 0.033 nM (S/N=3). The results suggest that this approach has the potential to be used in clinical research.