Determination of mini-short tandem repeat (miniSTR) loci by using the combination of polymerase chain reaction (PCR) and microchip electrophoresis

Hair and Nail-On-Chip for Bioinspired Microfluidic Device Fabrication and Biomarker Detection

The advent of biosensors has tremendously increased our potential of identifying and solving important problems in various domains, ranging from food safety and environmental analysis, to healthcare and medicine. However, one of the most prominent drawbacks of these technologies, especially in the biomedical field, is to employ conventional samples, such as blood, urine, tissue extracts and other body fluids for analysis, which suffer from the drawbacks of invasiveness, discomfort, and high costs encountered in transportation and storage, thereby hindering these products to be applied for point-of-care testing that has garnered substantial attention in recent years. Therefore, through this review, we emphasize for the first time, the applications of switching over to noninvasive sampling techniques involving hair and nails that not only circumvent most of the aforementioned limitations, but also serve as interesting alternatives in understanding the human physiology involving minimal costs, equipment and human interference when combined with rapidly advancing technologies, such as microfluidics and organ-on-a-chip to achieve miniaturization on an unprecedented scale. The coalescence between these two fields has not only led to the fabrication of novel microdevices involving hair and nails, but also function as robust biosensors for the detection of biomarkers, chemicals, metabolites and nucleic acids through noninvasive sampling. Finally, we have also elucidated a plethora of futuristic innovations that could be incorporated in such devices, such as expanding their applications in nail and hair-based drug delivery, their potential in serving as next-generation wearable sensors and integrating these devices with machine-learning for enhanced automation and decentralization.

Simultaneous determination of trace Aflatoxin B1 and Ochratoxin A by aptamer-based microchip capillary electrophoresis in food samples

An aptamer-based microchip capillary electrophoresis coupled with laser induced fluorescence (MCE-LIF) detection method for fast determination of Aflatoxin B₁ (AFB₁) and Ochratoxin A (OTA) was developed. Aptamers that are specific to these two mycotoxins were first hybridized with their aptamer complementary oligonucleotides. The double strand DNA that comes in contact with mycotoxin-containing environment would be unwound into separate aptamer-mycotoxin complex and aptamer complementary single strand. Different types of oligonucleotides can be separated in MCE and detected under the aid of fluorescent dye SYBR gold in LIF detection unit. Under the optimal conditions, on-chip aptamer-mycotoxin conjugates analysis was achieved within 3 min with extremely low LODs (0.026 ng/mL for AFB₁ and 0.021 ng/mL for OTA). Specificity study indicated that other major mycotoxins would not cross-react with these two aptamers, demonstrating the good selectivity of the proposed method. Quantification of trace AFB₁ and OTA in real food samples was carried out and satisfactory recoveries were obtained. It is demonstrated that this method is fast, facile and specific for Simultaneous determination of trace AFB₁ and OTA from foodstuffs.

A label-free and universal platform for antibiotics detection based on microchip electrophoresis using aptamer probes

A novel label-free, universal, and high throughput aptasensor was developed based on a microchip electrophoresis (MCE) platform for automatic detection of antibiotic residues in food. Firstly, chloramphenicol (CAP) was employed as a model to be captured by its aptamer probe (Apt). Then, the partial complementary oligonucleotide of CAP's aptamer (C-DNA) was introduced into the reaction system. Because the Apt-CAP complex can't further hybrid with free C-DNA, the amount of hybrid Apt-C-DNA double strand DNA (dsDNA) was less than that without adding the target. Finally, the above mixture was introduced into the microchip electrophoresis (MCE) platform for detection, both dsDNA and Apt-CAP can be separated and produce different fluorescence signals in the MCE. In a certain concentration range, the ratio of signal between dsDNA and Apt-CAP (I_dsDNA/I _Apt-CAP) was proportional to the concentration of targets. Under the optimum conditions, the ratio showed a satisfactory linearity range from 0.008 to 1ng/mL of CAP with a detection limit of 0.003ng/mL. Thus, a universal MCE-based assay was developed for quantifying CAP automatically. The method was also successfully applied in the different food samples for CAP detection, which showed a good recovery (Milk: 91.1-108%, Fish: 86.1-114%) and the results were consistent with that of ELISA. This method owned many merits as follows: firstly, MCE was a high throughput screening platform and the detection time is limited to 3min for each sample. Secondly, the aptamer probes can be directly used for detection without labeling any signal tag which can facilitate the preparation procedures of probes. Thirdly, the operation was easy just by the following steps: firstly, the mixture of aptamer probes were incubated followed adding C-DNA; then measurement was performed. Moreover, the assay with MCE platform can be used to detect other targets just by changing the corresponding aptamer probe; it can even realize simultaneous detection when the targets have aptamers with different number of base pairs. Above all, it's a high- throughput and prospective method which can be applied in high throughput screening of antibiotics in food safety.

A comparative study of three different nucleic acid amplification techniques combined with microchip electrophoresis for HPV16 E6/E7 mRNA detection

The development of a high-throughput and automatic system by combining gene amplification with MCE for HPV16 E6/E7 mRNA screening is reported.

Assay of multiplex proteins from cell metabolism based on tunable aptamer and microchip electrophoresis

A simple and rapid method for multiplex protein assay based on tunable aptamer by microchip electrophoresis has been developed. Different lengths of aptamers can modulate the electrophoretic mobility of proteins, allowing the protein molecules to be effectively separated in hydroxyethyl cellulose buffer with 1.00 mM magnesium ion. A non-specific DNA was exploited as an internal standard to achieve the quantitative assay and to reduce the interference. A fluorescence dye SYBR gold was exploited to improve the sensitivity and to suppress the interference from sample matrix. Under optimum conditions, quantitative assay of PDGF-BB (R(2)=0.9986), VEGF165 (R(2)=0.9909), and thrombin (R(2)=0.9947) were achieved with a dynamic range in the 5.00-150.0 nM and RSDs in the 5.87-16.3% range. The recoveries were varied from 83.6% to 113.1%. Finally, the proposed method was successfully applied to analyze cell secretions, and then the concentration of PDGF-BB and VEGF165 were detected from 5.15 nM to 2.03 nM, and 3.14 to 2.53 nM, respectively, indicating the established method can be used to analyze cell secretions.