Sandwich-type aptamer-based biosensors for thrombin detection.

Thrombin, a proteolytic enzyme, plays an essential role in catalyzing many blood clotting reactions. Thrombin can act as a marker for some blood-related diseases, such as leukemia, thrombosis, Alzheimer's disease and liver disease. Therefore, its diagnosis is of great importance in the fields of biological and medical research. Biosensors containing sandwich-type structures have attracted much consideration owing to their superior features such as reproducible and stable responses with easy improvement in the sensitivity of detection. Sandwich-type platforms can be designed using a pair of receptors that are able to bind to diverse locations of the same target. Herein, we investigate recent advances in the progress and applications of thrombin aptasensors containing a sandwich-type structure, in which two thrombin-binding aptamers (TBAs) identify different parts of the thrombin molecule, leading to the formation of a sandwich structure and ultimately signal detection. We also discuss the pros and cons of these approaches and outline the most logical approach in each section.

Optimization of Gamma Aminobutyric Acid Production Using High Pressure Processing (HPP) by Lactobacillus brevis PML1.

In the present research, the production potential of gamma aminobutyric acid (GABA) using Lactobacillus brevis PML1 was investigated. In addition, the microorganism viability was examined in MAN, ROGOSA, and SHARPE (MRS) after undergoing high hydrostatic pressure at 100, 200, and 300 MPa for 5, 10, and 15 min. Response surface methodology (RSM) was applied to optimize the production conditions of GABA as well as the bacteria viability. Analysis of variance (ANOVA) indicated that both the independent variables (pressure and time) significantly influenced the dependent ones (GABA and bacteria viability) (P < 0.05). The optimum extraction conditions to maximize the production of GABA included the pressure of 300 MPa and the time of 15 min. The amount of the compound was quantified using thin-layer chromatography (TLC) and spectrophotometry. For the process optimization, a central composite design (CCD) was created using Design Expert with 5 replications at the center point, whereby the highest content of GABA was obtained to be 397.73 ppm which was confirmed by high performance liquid chromatography (HPLC). Moreover, scanning electron microscopy (SEM) was utilized to observe the morphological changes in the microorganism. The results revealed that not only did have Lactobacillus brevis PML1 the potential for the production of GABA under conventional conditions (control sample) but also the content of this bioactive compound could be elevated by optimizing the production parameters.

Ultrasensitive detection of micrococcal nuclease activity and Staphylococcus aureus contamination using optical biosensor technology-A review.

One of the most common and important pathogenic bacteria is Staphylococcus aureus (S. aureus) which is known as a foodborne illness all over the world. The detection of micrococcal nuclease (MNase) can act as a unique diagnostic biomarker for the identification of S. aureus. So far, various complex methods have been introduced for the evaluation of S. aureus bacterium. However, they have different limitations such as labor-intensive, inaccurate results and time-consuming procedures. Thus, it is of particular attention to develop fast, easy, simple and more approachable detection methods based on nanotechnology and MNase detection. In this review, recent advances and modern techniques of ultrasensitive biosensors based on quantum dots (QDs), noble metal and magnetic nanoparticles (NPs), graphene oxide (GO) nanosheets, and also transfer energy strategy have been discussed for the identification of MNase activity and S. aureus contamination. Besides, advantages and disadvantages of different types of fluorescent, phosphorescent and colorimetric biosensors have been discussed.