RESUMEN
A novel, enhanced photoelectrochemical aptasensing platform was developed through integrating the sensitization effect of CdTe@CdS core-shell quantum dots (QDs) coupled with exonuclease-I (Exo-I) assisted target recycling for significant signal amplification. Carcinoembryonic antigen (CEA) was selected as the target analyte to exhibit the analytical performance of this platform. Specifically, nitrogen-doped mesoporous TiO2 (mTiO2:N) was firstly synthesized through an evaporation-induced self-assembly (EISA) method. Then, an mTiO2:N/Au hybrid structure was prepared through depositing Au nanoparticles on the surface of the mTiO2:N film and this acted as the photoelectrochemical matrix to immobilize the complementary DNA (cDNA) of the CEA aptamer probe (pDNA). CdTe@CdS core-shell QDs as sensitization agents were covalently bound at the front-end of pDNA. After pDNA was hybridized with cDNA, the labels of the CdTe@CdS core-shell QDs were very close to the mTiO2:N/Au electrode surface, resulting in an evidently enhanced photocurrent intensity due to the generation of the sensitization effect. When the aptasensor was incubated with CEA and Exo-I simultaneously, CdTe@CdS QD labeled pDNA (denoted QD-pDNA) became specifically bound with CEA and meanwhile was separated from the electrode surface, leading to an obviously weakened sensitization effect and a decreased photocurrent intensity. Moreover, as Exo-I could digest the single strand form of pDNA, the previously bound CEA was released and continuously interacted with the rest of the pDNA on the electrode surface, causing further decreased photocurrent intensity. The well-designed photoelectrochemical aptasensor exhibited a low detection limit of 0.12 pg mL-1 and a wide linear range from 0.5 pg mL-1 to 10 ng mL-1 for CEA detection, and it also showed good selectivity, reproducibility and stability. The proposed signal amplification strategy provides a promising universal photoelectrochemical platform for sensitively detecting various biomolecules at low levels.
RESUMEN
Based on the identification of the threatened plants in Northeast China and the priority conservation value of plants, the priority conservation regions of the threatened plants in Northeast China were determined. In the 219 counties (or cities) of Northeast China, 119 counties (or cities) had the distribution of threatened plants. The Antu County in Jilin Province had the most species (42) of threatened plants. A total of 16 counties (cities) such as the Antu County of Jilin Province and the Huanren Manchu Autonomous County of Liaoning Provice, etc. were identified as the priority conservation regions of the threatened plants in Northeast China. According to the priority conservation value, five priority conservation regions of threatened plants in Northoast China were divided, including Changbai Mountain conservation region, East Liaoning conservation region, South Liaoning conservation region, Zhangguangcai Mountain conservation region, and Xiaoxing' an Mountain conservation region. The main threatened plants in each priority conservation region were also analyzed.
