A novel microfluidic chip and antibody-aptamer based multianalysis method for simultaneous determination of several tumor markers with polymerization nicking reactions for homogenous signal amplification

Aptamer-based microfluidics for the detection of cancer biomarkers

Early diagnosis of cancer is a major concern in clinical medicine. Recently, aptamer-based microfluidics have offered promising platforms for the sensitive detection of cancer biomarkers. This review summarizes the application of aptamer sensors in the microfluidic platform for cancer biomarker analysis. The materials for microfluidic aptamer biosensor fabrication, unique design based on microposts, materials for enhanced detection capability, and the application principle of combining with other detection methods are introduced in detail, so as to demonstrate its development potential in cancer diagnosis and personalized therapy. Finally, the challenges and opportunities for developing miniaturized diagnostic platforms are discussed.

A universal assay strategy for sensitive and simultaneous quantitation of multiplex tumor markers based on the stirring rod-immobilized DNA-LaMnO3 perovskite-metal ions encoded probes

It was extremely urgent to develop some simultaneous and sensitive biosensors for detecting multiplex serum tumor markers (TMs) for early screening of cancers. Herein, a multiplex assay was developed based on the DNA-LaMnO₃ (DNA-LMO) perovskite encoded probes and targets mediated competitive replacement strategy. Alpha fetoprotein (AFP), carcinoembryonic antigen (CEA) and prostate specific antigen (PSA) markers were employed as representative target TMs. Aptasensor is prepared by a series of DNA-LMO-M encode probes which were prepared by three hyperbranched DNA firstly immobilized on LMO encapsulating Pb, Cd or Cu ions. Then, three TMs aptamers were labeled on the stirring-rod and hybridized with the probes. After the developed encoded probes was incubated the TMs, the encoded probes corresponding to different TMs can be released into the supernatant through the competitive replacement. The inner metal ion can be simultaneously detected by square wave voltammetry corresponding to various TMs. Since the stirring rod can enrich many encoded probes containing a lot of metal ions, multiplex signal amplification can be realized. Due to the enrichment and easy separation of the stirring rod, the signal-to-noise ratio was also obviously improved and thus to results in good sensitivity and accuracy. Moreover, it took only 20 min to detect three targets which much faster than many same types of aptasensor. Under the optimal conditions, the low detection limit for CEA (3.6 × 10^-4 ng/mL), AFP (3.4 × 10^-4 ng/mL) and PSA (2.8 × 10^-4 ng/mL) were obtained. Therefore, this method is likely to be used for early and sensitive screening of tumors.

Application of magnetic nanoparticles in nucleic acid detection

Nucleic acid is the main material for storing, copying, and transmitting genetic information. Gene sequencing is of great significance in DNA damage research, gene therapy, mutation analysis, bacterial infection, drug development, and clinical diagnosis. Gene detection has a wide range of applications, such as environmental, biomedical, pharmaceutical, agriculture and forensic medicine to name a few. Compared with Sanger sequencing, high-throughput sequencing technology has the advantages of larger output, high resolution, and low cost which greatly promotes the application of sequencing technology in life science research. Magnetic nanoparticles, as an important part of nanomaterials, have been widely used in various applications because of their good dispersion, high surface area, low cost, easy separation in buffer systems and signal detection. Based on the above, the application of magnetic nanoparticles in nucleic acid detection was reviewed.

Isothermal Nucleic Acid Amplification Techniques and Their Use in Bioanalysis

Recently, there has been a rapid progress in the development of techniques for isothermal amplification of nucleic acids as an alternative to polymerase chain reaction (PCR). The advantage of these methods is that the nucleic acids amplification can be carried out at constant temperature, unlike PCR, which requires cyclic temperature changes. Moreover, isothermal amplification can be conducted directly in living cells. This review describes the principles of isothermal amplification techniques and demonstrates their high efficiency in designing new highly sensitive detection methods of nucleic acids and enzymes involved in their modifications. The data on successful application of isothermal amplification methods for the analysis of cells and biomolecules with the use of DNA/RNA aptamers are presented.

Design and fabrication of a microfluidic chip to detect tumor markers

A microfluidic chip based on capillary infiltration was designed to detect tumor markers. Serum samples flowed along a microchannel that used capillary force to drive sample injection, biochemical reactions and waste liquid collection. This permitted us to realize rapid qualitative detection of tumor markers and other biological molecules. The chip integrated a number of microfluidic functions including blood plasma separation, microvalve operation, and antibody immobilization. Using antigen–antibody reaction principles, the chip provided highly selective and sensitive detection of markers. Combining a microfluidic chip with immunoassays not only improved the antigen–antibody reaction speed, but also reduced the consumption of samples and reagents. The experimental results showed that the chip can achieve separation of trace whole blood, control of sample flow rate, and detection of alpha fetoprotein, thus providing preliminary verification of its feasibility and potential for clinical use. In summary, in this paper a cheap, mass-produced, and portable microfluidic chip for cancer detection, which has good prospects for practical use during disease diagnosis and screening is reported.

A microfluidic chip for detecting tumor markers integrated functions including blood plasma separation, microvalve operation, and antibody immobilization.

Microfluidic chip electrophoresis for simultaneous fluorometric aptasensing of alpha-fetoprotein, carbohydrate antigen 125 and carcinoembryonic antigen by applying a catalytic hairpin assembly

An aptamer based assay is presented that is making use of a catalytic hybrid assembly and a microfluidic chip electrophoresis format. It enables simultaneous determination of the biomarkers (BMs) α-fetoprotein (AFP), carbohydrate antigen 125 (CA125), and carcinoembryonic antigen (CEA). The respective aptamers were covalently bound to Fe₃O₄@AuNPs (AuMPs) magnetic beads and then used to capture the biomarkers on their surface. Different single-stranded DNA primers were then labeled with various antibodies as encoding and signaling tags. The signal tags reacted with AuMPs-BMs to form different antibody-BM-aptamer complexes. After magnetic separation, three pairs of hairpins as substrates were introduced to trigger catalytic hybrid assembly by the primers in the complex. This will form many duplex DNA products of different length in the supernatant. The products can be magnetically separated by microfluidic chip electrophoresis and determined by fluorometry at excitation/emission wavelengths of 495/525 nm. Several experimental conditions including the hairpin concentration, reaction time and temperature were systemically optimized. The method can simultaneously quantify AFP, CEA and CA125, respectively, with detection limits of 0.1, 0.2, 0.15 pg mL^-1 (at S/N = 3). The aptamer functionalized magnetic beads can be reused for at least 20 times with a recovery of up to 80% after heat treatment. The method was employed to simultaneously detect the three BMs in serum samples. Graphical abstract Schematic presentation of the microfluidic chip electrophoresis and antibody-aptamer based multianalysis method for simultaneous detection of alpha-fetoprotein (AFP), carbohydrate antigen 125 (CA125) and carcinoembryonic antigen (CEA).