Metal-DNA coordination based bioinspired hybrid nanospheres for in situ amplification and sensing of microRNA

Functional DNA-Zn2+ coordination nanospheres for sensitive imaging of 8-oxyguanine DNA glycosylase activity in living cells

Sensitive monitoring of human 8-oxyguanine DNA glycosylase (hOGG1) activity in living cells is helpful to understand its function in damage repair and evaluate its role in disease diagnosis. Herein, a functional DNA-Zn2+ coordination nanospheres was proposed for sensitive imaging of hOGG1 in living cells. The nanospheres were constructed through the coordination-driven self-assembly of the entropy driven reaction (EDR) -deoxyribozyme (DNAzyme) system with Zn2+, where DNAzyme was designed to split structure and assembled into the EDR system. When the nanospheres entered the cell, the competitive coordination between phosphate in the cell and Zn2+ leaded to the disintegration of the nanospheres, releasing DNA and some Zn2+. The released Zn2+ acted as a cofactor of DNAzyme. In the presence of hOGG1, the EDR was completed, accompanied by fluorescence recovery and the generation of a complete DNAzyme. With the assistance of Zn2+, DNAzyme continuously cleaved substrates to produce plenty of fluorescence signals, thus achieving sensitive imaging of hOGG1 activity. The nanospheres successfully achieved sensitive imaging of hOGG1 in human cervical cancer cells (HeLa), human non-small cell lung cancer cells and human normal colonic epithelial cells, and assayed changes in hOGG1 activity in HeLa cells. This nanospheres may provide a new tool for intracellular hOGG1 imaging and related biomedical studies.

A photoelectrochemical biosensor based on b-TiO2/CdS:Eu/Ti3C2 heterojunction for the ultrasensitive detection of miRNA-21

A novel photoelectrochemical (PEC) biosensor based on b-TiO₂/CdS:Eu/Ti₃C₂ heterojunction was developed for ultrasensitive determination of miRNA-21. In this device, the b-TiO₂/CdS:Eu/Ti₃C₂ heterojunction with excellent energy level arrangement effectively facilitated photoelectric conversion efficiency and accelerated the separation of the photogenerated electron hole pairs, which because that the structure of heterojunction overcomes the drawbacks of single material, such as narrow light absorption range, wide band gap, short carrier lifetime, etc., improves light utilization, extends the lifetime of photogenerated electron hole pairs, and promotes electron transfer. Herein, hairpin DNA1 (H1) decorated on the b-TiO₂/CdS:Eu/Ti₃C₂ electrode surface by Cd-S bonds, after H2/miRNA-21 heterduplex was introduced, the strand-displacement reaction (SDR) was triggered between H1 and H2/miRNA-21, accordingly, miRNA-21 was discharged from the H2/miRNA-21 heterduplex, forming the H1/H2 duplex, and the reuse of miRNA-21 was realized. As a signal amplification factor, the signal amplification factor H3-CdSe was hybridized with H1/H2 duplex, which greatly enhanced the sensitivity of the PEC biosensor. Under optimal conditions, the designed PEC biosensor displayed outstanding sensitivity, selectivity and stability with a wide liner range from 1.0 μM to 10.0 fM and a low detection limit of 3.3 fM. The preparation of the optoelectronic material affords a new direction for the progress of heterojunction photovoltaic materials and the construction of the proposed biosensor also provides a new thought for the PEC detection of human miRNA-21 with superior performance. Simultaneously, the established biosensor exhibiting tremendous possibility for detecting other biomarkers and biomolecules in clinical diagnosis fields.

Highly sensitive biosensor based on aptamer and hybridization chain reaction for detection of cadmium ions

In this work, a highly sensitive biosensor for detecting cadmium ions (Cd²⁺ ) was developed based on Cd²⁺ -specific DNA aptamer and hybridization chain reaction (HCR). The Cd²⁺ -aptamer (named S0) was used to recognize Cd²⁺ and trigger HCR reaction. Without Cd²⁺ , S0 initiated the HCR to form long nicked dsDNA structures to quench the fluorescence. Then, Cd²⁺ can bind with S0 to block HCR to recover fluorescence. This biosensor had high sensitivity with the detection limit of 0.36 nM and a linear range from 0 to 10 nM. Moreover, it showed a satisfactory selectivity and recovery rates.

Development of a single-molecule biosensor with ultra-low background for simultaneous detection of multiple retroviral DNAs

Human T-cell lymphotropic virus type I and type II (HTLV-I and HTLV-II) are two most prevalent subtypes of HTLVs, and they usually infect individuals asymptomatically and may induce various diseases....