A Versatile Integrated Microfluidic Chip Based on Sonic Toothbrush-Assisted Mixing for Analyses of Diverse Biomolecules.

Usually, different assays and instrumentation are required for different types of targets, e.g., nucleic acids, proteins, small molecules, etc., because of significant differences in their structures and sizes. To increase efficiency and reduce costs, a desirable solution is to develop a versatile platform suitable for diverse objectives. Here, we established a versatile detection technique: first, target separation and enrichment were carried out using magnetic beads (MBs); then, different targets were converted to same barcoded DNA strands (BDs) released from gold nanoparticles; finally, sensitive detection of three different targets (miRNA-21, digoxigenin antibody, and aflatoxin B1) was achieved through exonuclease III (Exo III) cyclic cleavage-assisted signal amplification. To simplify the operation, we integrated this technique into a microfluidic chip with multiple chambers in which the requisite reagents were prestored. Just by moving the MBs through different chambers with a magnet, multiple steps can be completed. Due to the limited space in microfluidic chips, the full mixing of MBs and solution is a key point to improve reaction efficiency. The mixing can be achieved by acoustic vibration generated by a small, portable sonic toothbrush. Based on the microfluidic chip, the detection limits of the above three targets were 0.76 pM, 0.16 ng/mL, and 0.56 nM, respectively. Furthermore, miRNA-21 and Digoxigenin antibody (Dig-Ab) in serum and AFB1 in corn powder were also used to demonstrate the performance of this chip. Our versatile platform is easy to operate and is expected to develop into an automatic "sample-to-answer" device.

Portable detection of multiple mycotoxins based on a sonic toothbrush, microfluidic chip and smartphone.

A portable method for on-site detection of three mycotoxins was developed based on a sonic toothbrush, microfluidic chip and smartphone. Our method could complete all procedures, including sample pretreatment, signal conversion and processing, without any sophisticated instruments. The limits of detection for these mycotoxins were lower than the limit values in cereals in the standards of China and the European Union.

Ratiometric Fluorescent DNA Nanostructure for Mitochondrial ATP Imaging in Living Cells Based on Hybridization Chain Reaction.

For intracellular molecular detection, the appropriate probes should include the abilities to enter target cells noninvasively, target specific sites, and then respond to the analytes reliably. Herein, a ratiometric fluorescent DNA nanostructure (RFDN) was designed for mitochondrial adenosine triphosphate (ATP) imaging in living cells. The DNA nanostructure was constructed by continuous hybridization of two hairpin DNA strands (HS1-Cy3 and HS2-Cy5) under the initiation of the trigger. HS1-Cy3 and HS2-Cy5 contained split aptamer fragments of ATP and are labeled with a fluorescent donor (Cy3) and acceptor (Cy5), respectively. The RFDN integrated multiple split aptamer fragments and increased the local concentration of sensing probes. The binding of ATP to aptamer fragments on the RFDN shortened the distance between Cy3 and Cy5, resulting in obvious ratiometric signals (fluorescence resonance energy transfer). The RFDN showed good biocompatibility and can be internalized into cells in a caveolin-dependent endocytosis pathway. The co-localization imaging results indicated that the DNA nanostructure could target the mitochondria via Cy3 and Cy5. Moreover, the confocal imaging results showed that the intracellular ATP changes stimulated by drugs in living cells could be indicated by the RFDN. In this way, the RFDN is expected to be a simple, flexible, and general platform for chemo/biosensing in living cells.

Sensitive and specific detection of tumour cells based on a multivalent DNA nanocreeper and a multiplexed fluorescence supersandwich.

A self-assembled DNA nanostructure based on a DNA nanocreeper and multiplexed fluorescence supersandwich was designed for the sensitive and specific detection of tumour cells. This nanostructure could improve the binding affinity of current aptamers and trigger signal amplification, which provide potential for the discrimination of low abundant target cells in liquid biopsy.