Electrochemical DNA Sensor for Determination of p53 Tumor Suppressor Gene Incorporating Gold Nanoparticles Modification

Development of a Competitive Chemiluminescent Assay for Quantitative Determination of TP53 Fusion Protein Using Reagent Strips

Recent studies have shown that almost half of all cancers occur due to DNA damage. For the early diagnosis of cancer, a highly sensitized and swift identification for TP53 is needed since the corresponding TP53 protein is effectively recognized as "the guardian of the genome." To improve the detection sensitivity, numerous analytical methods were previously used for the determination of the TP53 protein, including denaturing high-performance liquid chromatography and enzyme-linked immunosorbent assay (ELISA). Currently, immunochromatographic tests (ICTs) that are simple to use, stable over time, and show low interference are regarded as valuable tools for the quick screening of food and environmental monitoring along with clinical diagnosis. ICTs often have limited sensitivity even if a variety of novel reporters possessing optimum photostability and improved brightness are used as signal-intensity reporters. Compared with N-(4-aminobutyl)-N-(ethylisoluminol) or luminol, a novel luminescent probe, 2',6'-diMethyl-4'-(N-succiniMidyloxycarbonyl) phenyl-10-sulfopropylacridiniuM-9-carboxylate (NSP-DMAE-NHS) has achieved a much higher efficiency, improvement in the biosensor's performance, and amplification of the signal without causing any damage to the biomolecule in terms of its biochemical activity. In this study, the reagent strip method was initially used to detect TP53 fusion protein by combining the advantages of NSP-DMAE-NHS and immunochromatography. In our experiment, the control and study lines on the strips were immobilized through HRP-conjugated goat anti-rabbit IgG and TP53 antigen, respectively. The optimized concentration of the anti-TP53 antibody-NSP-DMAE-NHS immunoconjugates was then added to the TP53 antigen samples. After, the test strips were inserted and left in the aforementioned buffer solution for an additional 20 min. Finally, a lab-made luminous measurement device was used to analyze the corresponding control and study lines on the strips. Under optimized conditions, this method was found to be ultrasensitive, with a wide range of linear responses from 0.0008 ng mL-1 to 1 µg mL-1 and a limit of detection of 0.0008 ng mL-1 (0.013 pM). Thus, a novel competitive chemiluminescent assay based on reagent strips was established for the determination of the TP53 fusion proteins. The strategy has potential applications for ultrasensitive detection in the early diagnosis of cancer.

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

Selectivity enhancements in gel-based DNA-nanoparticle assays by membrane-induced isotachophoresis: thermodynamics versus kinetics

Selectivity against mutant nontargets with a few mismatches remains challenging in nucleic acid sensing. Sensitivity enhancement by analyte concentration does not improve selectivity because it affects targets and nontargets equally. Hydrodynamic or electrical shear enhanced selectivity is often accompanied by substantial losses in target signals, thereby leading to poor limits of detection. We introduce a platform based on depletion isotachophoresis in agarose gel generated by an ion-selective membrane that allows both selectivity and sensitivity enhancement with a two-step assay involving concentration polarization at an ion-selective membrane. By concentrating both the targets and probe-functionalized nanoparticles by ion enrichment at the membrane, the effective thermodynamic dissociation constant is lowered from 40 nM to below 500 pM, and the detection limit is 10 pM as reported previously. A dynamically optimized ion depletion front is then generated from the membrane with a high electrical shear force to selectively and irreversibly dehybridize nontargets. The optimized selectivity against a two-mismatch nontarget (in a 35-base pairing sequence) is shown to be better than the thermodynamic equilibrium selectivity by more than a hundred-fold, such that there is no detectable signal from the two-mismatch nontarget. We offer empirical evidence that irreversible cooperative dehybridization plays an important role in this kinetic selectivity enhancement and that mismatch location controls the optimum selectivity even when there is little change in the corresponding thermodynamic dissociation constant.

Versatile biosensing platform for DNA detection based on a DNAzyme and restriction-endonuclease-assisted recycling

On the basis of a DNAzyme and a restriction-endonuclease-assisted target recycling strategy using Pd-Au alloy nanocrystals to immobilize probe DNA on an electrode and catalyze the reduction of H2O2 which amplified signal and promoted the detection sensitivity, a versatile biosensing platform for DNA detection was proposed. Using p53 and oral cancer genes as models, hemin/G-quadruplex simultaneously acted as a reduced nicotinamide adenine dinucleotide (NADH) oxidase and a horseradish peroxidase (HRP)-mimicking DNAzyme, and a versatile DNA biosensor was designed for the first time based on the good electrocatalytic activity of Pd-Au alloy nanocrystals. Hemin/G-quadruplex catalyzed the reduction of H2O2, which was generated from NADH in the presence of O2, to produce an electrochemical signal when thionine functioned as the electron mediator. Moreover, the nicking endonuclease N.BstNB I caused the target DNA to cycle for multiple rounds and further amplified the electrochemical response. This versatile DNA biosensor exhibited linear ranges for the detection of p53 and oral cancer genes from 0.1 fmol L(-1) to 0.1 nmol L(-1) and 0.1 fmol L(-1) to 1 nmol L(-1), respectively. The detection limits, established as 3σ, were estimated to be 0.03 and 0.06 fmol L(-1) for the p53 and oral cancer genes, respectively. The as-prepared biosensor could discriminate mismatched sequences, indicating a satisfactory selectivity and validating the feasibility of the proposed strategy. More importantly, simply by changing the helper DNA, this versatile DNA biosensor could detect different target DNA species, which could create a new avenue for the potential diagnosis of cancer.