Strategies for electrochemical detection in immunochemistry

Current Nucleic Acid Extraction Methods and Their Implications to Point-of-Care Diagnostics

Nucleic acid extraction (NAE) plays a vital role in molecular biology as the primary step for many downstream applications. Many modifications have been introduced to the original 1869 method. Modern processes are categorized into chemical or mechanical, each with peculiarities that influence their use, especially in point-of-care diagnostics (POC-Dx). POC-Dx is a new approach aiming to replace sophisticated analytical machinery with microanalytical systems, able to be used near the patient, at the point of care or point of need. Although notable efforts have been made, a simple and effective extraction method is still a major challenge for widespread use of POC-Dx. In this review, we dissected the working principle of each of the most common NAE methods, overviewing their advantages and disadvantages, as well their potential for integration in POC-Dx systems. At present, it seems difficult, if not impossible, to establish a procedure which can be universally applied to POC-Dx. We also discuss the effects of the NAE chemicals upon the main plastic polymers used to mass produce POC-Dx systems. We end our review discussing the limitations and challenges that should guide the quest for an efficient extraction method that can be integrated in a POC-Dx system.

Ultrasensitive strategy based on PtPd nanodendrite/nano-flower-like@GO signal amplification for the detection of long non-coding RNA

Highly up-regulated in liver cancer (HULC) is a novel promising noninvasive biomarker for hepatocellular carcinoma (HCC), which is a kind of long non-coding RNAs (lncRNAs). But traditional methods limited HULC clinical detection for ownself drawbacks. Development a new HULC detection approach is urgent and necessary. Electrochemical nucleic acid sensor based on different signal amplification strategies with high sensitivity, fast, simple, and convenient, may solve this problem. Herein, we propose a novel strategy based on Pt-Pd bimetallic nanodendrites/nanoflower-like clusters on graphene oxide/Au/horseradish peroxidase (PtPd BND/BNF@GO/Au/HRP) to enhance the catalytic efficiency and sensitivity. And Au particles were simultaneously and separately capped with thionine or detection probe, which increase the binding amount of detection probe and decrease the electronic background. The results indicated that the catalytic effect was noticeably elevated and that the biosensor provides ultrasensitive detection for the lncRNA HULC. The linear calibration of the biosensor ranged from 1.00×10(-3) to 1.00×10(3) pM/mL, and the limit of detection was 0.247 fM/mL. The lncRNA biosensor based on the PtPd BND/BNF@GO/Au/HRP/Au/thionine exhibited acceptable reproducibility and clear selectivity. This strategy may provide a new alternative for clinical HCC diagnosis through the detection of HULC.

Design of immunoprobes for electrochemical multiplexed tumor marker detection

Many approaches have been developed for simultaneous detection of multiple tumor markers. Among these approaches, the electrochemical immunoassay has the advantage of high sensitivity and specificity and could be easily expanded into multiplex detection platform. For the simultaneous multianalyte electrochemical immunosensor, performance is closely related with the characteristics of the immunoprobes and substrate. In order to construct a multilabeled immunoprobe platform, the most important issue is how to discriminate each signal for each analyte from the multiple antigen-antibody reactions. Currently, enzyme-based, noble metal nanomaterials, carbonmaterials and polymer-based nanomaterial immunoprobes have been used for dual- or three-analyte detections. However, there are still some challenges in developing sensitive method to detect three or more tumor markers owing to the lack of redox-active species that can produce three or more distinctive peaks. Additionally, for the immunosensing substrate, good conductivity, high specific surface area and good biocompatibility are further necessities.

Electrochemical detection of the disease marker human chitinase-3-like protein 1 by matching antibody-modified gold electrodes as label-free immunosensors

Tissue inflammation, certain cardiovascular syndromes and the occurrence of some solid tumors are correlated with raised serum concentrations of human chitinase-3-like protein 1 (YKL-40), a mammalian chitinase-like glycoprotein, which has become the subject of current research. Here we report the construction and characterization of an electrochemical platform for label-free immunosensing of YKL-40. Details of the synthesis of YKL-40 and production of anti-YKL-40 immunoglobulin G (IgG) are provided and cross-reactivity tests presented. Polyclonal anti-YKL-40 IgG was immobilized on gold electrodes and the resulting immunosensors were operated in an electrochemical flow system with capacitive signal generation. The strategy offered a wide linear detection range (0.1μg/L to 1mg/L) with correlation coefficients (R(2)) above 0.99 and good sensitivity (12.28±0.27nF/cm(2) per decade of concentration change). Additionally, the detection limit of 0.07±0.01μg/L was well below that of optical enzyme-linked immunosorbent assays (ELISAs), which makes the proposed methodology a promising alternative for YKL-40 related disease studies.

Ultrasensitive signal-on DNA biosensor based on nicking endonuclease assisted electrochemistry signal amplification

Combining the advantages of signal-on strategy and nicking endonuclease assisted electrochemistry signal amplification (NEAESA), a new sensitive and signal-on electrochemical DNA biosensor for the sequence specific DNA detection based on NEAESA has been developed for the first time. A Hairpin-shape probe (HP), containing the target DNA recognition sequence, is thiol-modified at 5' end and immobilized on gold electrode via Au-S bonding. Subsequently, the HP modified electrode is hybridized with target DNA to form a duplex. Then the nicking endonuclease is added and nicks the HP strand in the duplex. After nicking, 3'-ferrocene (Fc)-labeled part complementary probe (Fc-PCP) is introduced on the electrode surface by hybridizing with the thiol-modified HP fragment, which results in the generation of electrochemical signal. Hence, the DNA biosensor is constructed successfully. The present DNA biosensor shows a wide linear range of 5.0×10(-13)-5.0×10(-8)M for detecting target DNA, with a low detection limit of 0.167pM. The proposed strategy does not require any amplifying labels (enzymes, DNAzymes, nanoparticles, etc.) for biorecognition events, which avoids false-positive results to occur frequently. Moreover, the strategy has the benefits of simple preparation, convenient operation, good selectivity, and high sensitivity. With the advantages mentioned above, this simple and sensitive strategy has the potential to be integrated in portable, low cost and simplified devices for diagnostic applications.