A novel signal amplification tag to develop rapid and sensitive aptamer-based biosensors

Application of a porous zirconium-based MOF nanoplate as an affinity ECL platform for the detection of protein kinase activity and inhibitor screening

Abnormal kinase expression affects phosphorylation in the human body, which is associated with numerous diseases, including cancer, diabetes mellitus, and Alzheimer's disease. In this study, we synthesized a highly stable, two-dimensional, luminescence-functionalized metal-organic framework with remarkable electrochemiluminescence (ECL) by immobilizing 9,10-Di(p-carboxyphenyl) anthracene (dca) on a zirconium cluster (dca-Zr₁₂) via a strong coordination bond between -COO⁻ and Zr⁴⁺. This novel and simple platform relies on the highly specific identification of phosphate molecules by the ultra-thin dca-Zr₁₂ nanoplate through carboxylate-Zr⁴⁺-phosphate chemistry. The ferrocene-labeled peptide substrate (Fc-S-Peptide) was phosphorylated in the presence of protein kinase A (PKA) and adenosine 5'-triphosphate (ATP), and the resulting phosphopeptide could subsequently be precisely captured by the zirconium sites of the dca-Zr12-modified electrode and, eventually, quench the ECL and gain a signal-off state. This rapid and simple detection strategy was successfully employed to measure PKA activity, with a detection limit as low as 0.35 mU mL-1. Based on the results, it exhibited high selectivity and can be applied for screening PKA inhibitors. The technique was subsequently applied to detect protein kinase activity in drug-stimulated MCF-7 cell lysates, demonstrating its potential for kinase-related investigations. Further, this platform could identify the activity of other kinase types with universal applicability.

Potential-resolved electrochemiluminescent immunoassay based on dual co-reactants regulation

Multi-signal-based self-calibrating biosensors have become a research focus due to their superior accuracy and sensitivity in recent years. Herein, the potential-resolved differential ECL immunoassay based on dual co-reactants regulation was developed. Meso-tetra(4-carboxyphenyl)porphyrin (TCPP) functionalized zirconium dioxide (ZrO2) composites (TCPP-ZrO2) was first synthesized using TCPP as the luminophore and ZrO2 as the enhancer and stabilizer. The organic-inorganic hybrid structure of TCPP-ZrO2 limits the intramolecular motion of TCPP and accelerates the production of reactive radicals of co-reactants, thus exhibiting excellent ECL intensity and stability. Then, the potential-resolved ECL properties of TCPP-ZrO2 regulated only by two co-reactants were explored. On this basis, a differential ECL immunosensor was constructed for the sensitive and accurate determination of heart-fatty acid binding protein (hFABP) using 2-(dibutylamino)ethanol modified gold nanoparticles (DBAE@Au) as labels (ECL-1, +1.3 V) and ECL-2 (-1.3 V) triggered by potassium persulfate (K2S2O8) as the internal reference. In the presence of hFABP, DBAE@Au was captured by the sensing interface to generate ECL-1 and consume K2S2O8, leading to a significant decrease of ECL-2. According to the intensity difference between ECL-2 and ECL-1, the detection of hFABP was achieved with a low detection limit and a wide linear range. The proposed differential ECL immunosensor has been applied in testing human serum samples with satisfactory results, demonstrating its promising applications for clinical diagnosis.

DNA nanotechnology-based strategies for gastric cancer diagnosis and therapy

Gastric cancer (GC) is a formidable adversary in the field of oncology. The low early diagnosis rate of GC results in a low overall survival rate. Therefore, early accurate diagnosis and effective treatment are the key to reduce the mortality of GC. With the advent of nanotechnology, researchers continue to explore new possibilities for accurate diagnosis and effective treatment. One such breakthrough is the application of DNA nanotechnology. In this paper, the application of exciting DNA nanomaterials in the diagnosis and treatment of GC is discussed in depth. Firstly, the biomarkers related to GC and the diagnostic strategies related to DNA nanotechnology are summarized. Second, the latest research progress of DNA nanomaterials in the GC targeted therapy are summarized. Finally, the challenges and opportunities of DNA nanomaterials in the research and clinical application of GC are prospected.

A label-free and ultrasensitive electrochemical biosensor using hybrid polypyrrole/gold nanoelectrocatalyst mediated signal amplification for the detection of miRNA-21

The quantitative detection of microRNAs (miRNAs) is crucial for the diagnosis of cancers, while the traditional methods involve complicated procedures and restricted signal gain. In this study, we have established an ultrasensitive electrochemical biosensor by combining a target-induced hybridization reaction and signal amplification strategy for the detection of miRNA-21. The signal amplification is achieved through employing double-stranded DNA as scaffolds for methylene blue (MB) and using a polypyrrole@gold nanocomposite (ppy@AuNPs) as the electrochemical catalyst for further enhancing the signal. Therefore, this proposed electrochemical platform displayed an analytical performance with a wide linear range from 10 fM to 100 nM and a low detection limit down to 5.4 fM. The excellent selectivity allows the biosensor to discriminate miRNA-21 from other miRNAs, even the one base-mismatched sequence. Moreover, this nanoelectrocatalyst-based platform exhibited good reproducibility and remarkable storage stability, which shows great potential for miRNA-21 detection.

Aptamer-based technology for gastric cancer theranostics

Gastric cancer is one of the most common causes of cancer death worldwide. This cancer exhibits high molecular and phenotype heterogeneity. The overall survival rate for gastric cancer is very low because it is always diagnosed in the advanced stages. Therefore, early detection and treatment are of great significance. Currently, biomedical studies have tapped the potential clinical applicability of aptamer-based technology for gastric cancer diagnosis and targeted therapy. Herein, we summarize the enrichment and evolution of relevant aptamers, followed by documentation of the recent developments in aptamer-based techniques for early diagnosis and precision therapy for gastric cancers.

A rapid and simple method for simultaneous determination of three breast cancer related microRNAs based on magnetic nanoparticles modified with S9.6 antibody

Cancer progression is typically associated with the simultaneous changes of multiple microRNA (miR) levels. Therefore, simultaneous determination of multiple miR biomarkers exhibits great promise in early diagnosis of cancers. This research seeks to discuss a simple biosensing method for the ultrasensitive and specific detection of the three miRs related to the breast cancer based on S9.6 antibody coated magnetic beads, titanium phosphate nanospheres, and screen-printed carbon electrode. To prepare signaling probes, three hairpin DNAs (hDNAs) were labeled with three encoding titanium phosphate nanospheres with large quantities of different heavy metal ions (zinc, cadmium, lead), which have been utilized to discriminate the signals of three microRNA targets in relation with the corresponding heavy metal ions. After that, these hairpin structures hybridize with miR-21, miR-155 and miR-10b to form miR-21/hDNA1, miR-155/hDNA2 and miR-10b/hDNA3 complexes, which were captured by S9.6 antibodies (one anti-DNA/RNA antibody) pre-modified on magnetic bead surface. Therefore, the specific preconcentration of targets from complex matrixes can be carried out using magnetic actuation, increasing the sensitivity and specificity of the detection. The biosensor was suitably applied for direct and rapid detection of multiple microRNAs in real sample. It was observed that there were no significant differences between the results obtained by the suggested method and qRT-PCR as a reference method. So, this method makes an ultrasensitive novel platform for miRNAs expression profiling in clinical diagnosis and biomedical research.

A universal ratiometric method for Micro-RNA detection based on the ratio of electrochemical/electrochemiluminescence signal, and toehold-mediated strand displacement amplification

An ultra-selective and reproductive ratiometric platform was introduced based on the ratio of Ru(phen)₃²⁺ electrochemiluminescence (ECL) signal and methylene blue (MB) electrochemistry (EC) signal, which was amplified using a specific and efficient toehold-mediated strand displacement (TMSD). The stable DNA nanoclews (NCs) were efficiently loaded with MB (MB-NCs) as EC signal tags after being synthesized utilizing a simple rolling circle amplification reaction. Besides, Ti₃C₂-based nanocomposite could apply as a superb carrier for both Ru(phen)₃²⁺ and gold nanoparticles (Ti₃C₂-Au-Ru), resulting in a nearly constant ECL internal reference to eliminate the possible interferences. The Ti₃C₂-Au-Ru was attached to the surface of the electrode using Nafion, which exhibited excellent conductivity, and hairpin DNAs (hDNAs) were fixed on AuNPs via an Au-S bond. The designed biosensor was finally applied for miRNA-18a detection as a target model. The TMSD method made it possible to concurrently convert and amplify a single miRNA-18ainput into a large amount of output DNAs with high selectivity. These output DNAs were designed to unfold the stem-locked area of hDNAs. The opened hDNAs then hybridized with the MB-NCs to produce an EC signal. In the proposed biosensing system, by raising the target concentration of miRNA, the EC signal gradually rose, the ECL signal remained nearly constant, and the ratiometric detection method markedly promoted biosensor accuracy. Linear correlations of the ratio value of the EC/ECL with miRNA-18a concentrations between 20 aM and 50 pMwere observed, with the limit of detection of 9 aM. The biosensor was applied to detect miRNA-18a in real serum samples with satisfactory results.

MXene catalytic amplification-fluorescence/absorption dimode aptamer sensor for the detection of trace Pb2+ in milk

Lead ion (Pb²⁺) is a toxic heavy metal, which is very harmful to organisms. Therefore, the establishment of a rapid, simple, and sensitive method is of great significance to food safety and human health. It was found that MXeneTi₃C₂ nanosheet (NS) has a strong catalytic effect on the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) via H₂O₂ to form the oxidized product (TMB_OX); it has a strong fluorescence peak at 415 nm and an absorption (Abs) peak at 295 nm. The aptamer of Pb²⁺ (Apt_pb) can be adsorbed on the surface of an NS to form MXene-Apt conjugates, which reduces its catalytic active sites and inhibits its catalytic activity. When the target Pb²⁺ is added, it specifically binds with Apt_pb to release MXene NSs to enhance the dimode signals. Therefore, a new MXene catalytic fluorescence/absorption dimode aptamer biosenering platform was fabricated for the determination of trace Pb²⁺ in milk and water samples, with the fluorescence assay linear range (LR) of 5.0 × 10⁻²-2.0 nmol/L.