A microfluidic chip-based fluorescent biosensor for the sensitive and specific detection of label-free single-base mismatch via magnetic beads-based "sandwich" hybridization strategy.

A novel microfluidic chip-based fluorescent DNA biosensor, which utilized the electrophoretic driving mode and magnetic beads-based "sandwich" hybridization strategy, was developed for the sensitive and ultra-specific detection of single-base mismatch DNA in this study. In comparison with previous biosensors, the proposed DNA biosensor has much more robust resistibility to the complex matrix of real saliva and serum samples, shorter analysis time, and much higher discrimination ability for the detection of single-base mismatch. These features, as well as its easiness of fabrication, operation convenience, stability, better reusability, and low cost, make it a promising alternative to the SNPs genotyping/detection in clinical diagnosis. By using the biosensor, we have successfully determined oral cancer-related DNA in saliva and serum samples without sample labeling and any preseparation or dilution with a detection limit of 5.6 × 10(-11) M, a RSD (n = 5) < 5% and a discrimination factor of 3.58-4.54 for one-base mismatch.

Liquid chromatography on a monolithic column microfluidic chip coupled with "three-T" sample injection mode and amperometric detection.

An LC microfluidic chip (LC chip) with amperometric detection was developed. The LC chip employed a 7.5 cm long reversed-phase polymethacrylate monolithic column as a stationary phase and a "three-T" injection mode. A convenient interface was designed to conduct pump pressure into the microfluidic chip to drive solution, and a home-made device was used to control the distance between the working electrode and the LC chip accurately. The "three-T" sample injection mode completely avoided the problem of sample dilution and sample leakage during separation, which is usually observed in traditional and "T" type LC chip, without the using of valve and finally results in a better resolution, reproducibility and relatively high sensitivity. Using the proposed LC chip system, we have successfully separated two isomers, catechol and hydroquinone, within 12 min with a RSD (n=3) <3.0% for retention time and <2.4% for peak area. We have also successfully separated and determined 5-hydroxy-L-tryptophan, dopamine and 5-hydroxytryptamine within 25 min with a RSD (n=3) <5% (for peak area) and a detection limit of 0.16-0.51 µmol/L.

A novel electrically magnetic-controllable electrochemical biosensor for the ultra sensitive and specific detection of attomolar level oral cancer-related microRNA.

Non-invasive early diagnosis of oral cancer is the most effective means to reduce mortality rate from this disease. In this paper, we described a novel magnetic-controllable electrochemical RNA biosensor for the ultra sensitive and specific detection of oral cancer-related microRNA (miRNA) based on a home-made electrically magnetic-controllable gold electrode. The electrically magnetic-controllable gold electrode combined the merits of heated electrode and magnetic electrode, has notable advantage such as that the strength and direction of the magnetic field and the temperature of the electrode's surface can be easily regulated. The advantage of electrically magnetic-controllable gold electrode, as well as the utilization of "junction-probe" strategy and magnetic beads (MBs)-based enzymatic catalysis amplification, make the biosensor has ultra-high sensitivity and discrimination ability even for the detection of similar miRNAs. It can be used to detect as low as 0.22 aM (2.2 × 10(-19)M) of oral cancer-related miRNA with a recovery of 93-108% and a RSD<6 (n=5). The high sensitivity and selectivity, as well as the easiness of fabrication, operational convenience, short analysis time, good stability and re-usability, make the biosensor a promising alternative for the early point-of-care diagnosis of oral cancer. The success of the biosensor also leads to a great potential in the development of biosensor for the early diagnosis of other diseases.