Ultrasensitive photoelectrochemical aptasensing of miR-155 using efficient and stable CH3NH3PbI3 quantum dots sensitized ZnO nanosheets as light harvester

A halide perovskite/lead sulfide heterostructure with enhanced photoelectrochemical performance for the sensing of alkaline phosphatase (ALP)

For the construction of halide perovskite-based photoelectrochemical (PEC) biosensors in aqueous solution, the balance between retaining the excellent photoelectric performances of the halide perovskite and the protective modification of the halide perovskite has always been a challenging problem. In this work, a simple and sensitive photoelectrochemical biosensor based on inorganic halide perovskite CsPbBr₃ as the photoactive material for the detection of alkaline phosphatase (ALP) was reported. The substrate sodium thiophosphate (Na₃SPO₃) can be catalyzed by ALP to produce hydrogen sulfide (H₂S), which can react with the lead site on the surface of the CsPbBr₃ film to form lead sulfide (PbS), resulting in a stable heterostructure and enhanced photocurrent intensity. The possible mechanism of enhanced photocurrent response of CsPbBr₃/PbS heterojunctions was studied in detail. This work paves a new way for applying halide perovskites in different biosensor designs.

Recent Progress of Perovskite Nanocrystals in Chem/Bio Sensing

Perovskite nanocrystals (PNCs) are endowed with extraordinary photophysical properties such as wide absorption spectra, high quantum yield, and narrow emission bands. However, the inherent shortcomings, especially the instability in polar solvents and water incompatibility, have hindered their application as probes in chem/bio sensing. In this review, we give a fundamental understanding of the challenges when using PNCs for chem/bio sensing and summarize recent progress in this area, including the application of PNCs in various sensors and the corresponding strategies to maintain their structural integrity. Finally, we provide perspectives to promote the future development of PNCs for chem/bio sensing applications.

A photoelectrochemical sensor based on a reliable basic photoactive matrix possessing good analytical performance for miRNA-21 detection

The basic photoactive matrixes on transparent electrodes are essential for the performance of photoelectrochemical (PEC) biosensors. Herein, we demonstrate an optimized fabrication strategy toward a reliable ITO/TiO2/AuNP photoanode by sequential deposition of TiO2/Au nanoparticles (Au NPs) on indium tin oxide (ITO) substrates. The identified fabrication conditions include spin-coating tetraisopropyl titanate on ITO slices followed by in situ electrodeposition of Au NPs and finally the thermal annealing treatment. By the conjugation of the thiolated hairpin NH2-DNA sequence and CdTe quantum dots (QDs) onto the thus-prepared photoanodes, a novel PEC sensor for the ultrasensitive detection of miRNA was constructed. The proposed PEC sensor offered advantages including simple structure, storage stability and excellent detection reproducibility as well as sensitivity and specificity toward miRNA-21. Finally, we found that this PEC displayed a broad detection linear range of 1.0 fM to 1.0 nM with a low detection limit of 0.37 fM. This PEC sensor can also excellently discriminate the mismatched miRNA. Moreover, the PEC sensor also showed a satisfactory result in normal human serum sample analysis. These findings emphasized the importance of basic photoactive matrixes for the fabrication of PEC sensors, providing solid fundamental insights for future application of metal oxide substrates for other PEC applications, especially PEC biosensors.

Dual-probe fluorescent biosensor based on T7 exonuclease-assisted target recycling amplification for simultaneous sensitive detection of microRNA-21 and microRNA-155

Effective and simultaneous monitoring of the abnormal expression of certain microRNAs (miRNAs), especially for miRNA-21 and miRNA-155, can indicate drug resistance in lung cancer. In this work, T7 exonuclease (T7 Exo)-assisted target recycling amplification coupled with the extensive fluorescence quenching of graphene oxide (GO) was designed for the simultaneous detection of miRNA-21 and miRNA-155 using FAM- and ROX-labeled single-strand DNA probes. Through this method, the variable emission intensities of FAM and ROX caused by the introduction of miRNA-21 and miRNA-155, respectively, were obtained with high sensitivity. The method exhibited excellent analytical performance for simultaneous detection of miRNA-21 and miRNA-155 without cross-interference. The linear range was from 0.005 nM to 5 nM over three orders of magnitude, with detection limits as low as 3.2 pM and 4.5 pM for miRNA-21 and miRNA-155, respectively. Furthermore, the recovery (92.49-103.67%) and relative standard deviation (RSD < 4.8%) of the standard addition test of miRNA-21 and miRNA-155 in human plasma suggested the potential for drug resistance warning in clinical practice via this simple strategy. A homogeneous T7 Exo-assisted signal amplification combined with GO quenching platform was developed for accurate, sensitive and simultaneous analysis of miRNA-21 and miRNA-155 for drug resistance warning in lung cancer. This simple method exhibited a wide linear range and low LODs for miR-21 and miR-155.

Recent Progress and Development in Inorganic Halide Perovskite Quantum Dots for Photoelectrochemical Applications

Inorganic halide perovskite quantum dots (IHPQDs) have recently emerged as a new class of optoelectronic nanomaterials that can outperform the existing hybrid organometallic halide perovskite (OHP), II-VI and III-V groups semiconductor nanocrystals, mainly due to their relatively high stability, excellent photophysical properties, and promising applications in wide-ranging and diverse fields. In particular, IHPQDs have attracted much recent attention in the field of photoelectrochemistry, with the potential to harness their superb optical and charge transport properties as well as spectacular characteristics of quantum confinement effect for opening up new opportunities in next-generation photoelectrochemical (PEC) systems. Over the past few years, numerous efforts have been made to design and prepare IHPQD-based materials for a wide range of applications in photoelectrochemistry, ranging from photocatalytic degradation, photocatalytic CO₂ reduction and PEC sensing, to photovoltaic devices. In this review, the recent advances in the development of IHPQD-based materials are summarized from the standpoint of photoelectrochemistry. The prospects and further developments of IHPQDs in this exciting field are also discussed.

Au nanoparticles on two-dimensional MoS2 nanosheets as a photoanode for efficient photoelectrochemical miRNA detection

MiRNAs are small regulatory RNAs that play crucial roles in the oncogenic state in various cancers and have shown highly promising clinical applications as plasma-based markers for cancer classification and prognostication. Due to their electroanalytical advantages, photoelectrochemical biosensors are a very attractive alternative technology for miRNA sensing and detection. In this work, we demonstrated a novel photoelectrochemical (PEC) sensor using the in situ grown Au nanoparticles/two-dimensional molybdenum disulfide (MoS2) nanosheet heterojunction (MoS2-AuNPs) on ITO glass as the photoanode (MoS2-AuNPs/ITO). AuNPs were used as a photoelectronic transfer promoter and DNA probe immobilization carrier as well. The thiol modified biotin DNA with a hairpin structure was tethered to the MoS2-AuNPs/ITO surface to form a specific capturing layer for miRNA detection. The biotin specific protein streptavidin was used as the signal amplifying species. This PEC sensor is structurally simple and possesses sensitivity and specificity toward miRNA. The CV and EIS responses were evaluated to monitor the PEC anode fabrication. The stability and reproducibility of this PEC design strategy were both evaluated before it was used in analyzing the samples of miRNA in human serum. Finally, we found that this PEC sensor displayed a broad detection linear range and a low detection limit of 4.21 fM, and it can excellently discriminate the mismatched miRNA. These findings pave the way for developing PEC sensors targeting miRNA by using noble metals/MoS2 heterojunctions.

Recent advances in nanomaterial-based electrochemical and optical sensing platforms for microRNA assays

This review describes recent efforts in the application of nanomaterials as sensing elements in electrochemical and optical miRNAs assays.

Nucleic Acid Aptamers Targeting Epigenetic Regulators: An Innovative Therapeutic Option

Epigenetic mechanisms include DNA methylation, posttranslational modifications of histones, chromatin remodeling factors, and post transcriptional gene regulation by noncoding RNAs. All together, these processes regulate gene expression by changing chromatin organization and DNA accessibility. Targeting enzymatic regulators responsible for DNA and chromatin modifications hold promise for modulating the transcriptional regulation of genes that are involved in cancer, as well as in chronic noncommunicable metabolic diseases like obesity, diabetes, and cardiovascular diseases. Increasingly studies are emerging, leading to the identification of specific and effective molecules targeting epigenetic pathways involved in disease onset. In this regard, RNA interference, which uses small RNAs to reduce gene expression and nucleic acid aptamers are arising as very promising candidates in therapeutic approach. Common to all these strategies is the imperative challenge of specificity. In this regard, nucleic acid aptamers have emerged as an attractive class of carrier molecules due to their ability to bind with high affinity to specific ligands, their high chemical flexibility as well as tissue penetration capability. In this review, we will focus on the recent progress in the field of aptamers used as targeting moieties able to recognize and revert epigenetics marks involved in diseases onset.

All-inorganic perovskite quantum dot/TiO2 inverse opal electrode platform: stable and efficient photoelectrochemical sensing of dopamine under visible irradiation

CsPbX3 (X = Cl, Br or I) perovskite quantum dots (PQDs) have attracted tremendous attention due to their extraordinarily excellent optical properties. However, there is still an obstacle for their bio-application, which is limited by their water-instability. In this work, we have designed a novel visible light triggered photoelectrochemical (PEC) sensor for dopamine (DA) based on CsPbBr1.5I1.5 PQD immobilized three-dimensional (3D) TiO2 inverse opal photonic crystals (IOPCs). Supported by the TiO2 IOPCs, the water-stability of the PQDs as well as that of the PEC sensor was considerably improved. Furthermore, employed as a photoactive material in PEC sensor, CsPbBr1.5I1.5 PQDs can expand the photocurrent response of the PEC sensor to the whole visible region. In addition, the modulation of the photonic stop band effect of TiO2 IOPCs on the incident light and the emission of PQDs could further enhance the photocurrent response. Such a PEC sensor demonstrates sensitive detection of DA in phosphate buffer saline solution and serum, with a good linear range from 0.1 μM to 250 μM and a low detection limit of approximately 0.012 μM. Our strategy opens an alternative horizon for PQD based PEC sensing, which could be more sensitive, convenient and inexpensive for clinical and biological analysis.

CsPbBr3 perovskite quantum dots/ZnO inverse opal electrodes: photoelectrochemical sensing for dihydronicotinamide adenine dinucleotide under visible irradiation

All-inorganic perovskite quantum dots (PQDs) have attracted tremendous attention due to their extraordinary optical properties, especially CsPbBr₃ QDs with their high stability and photoluminescence efficiency.

Two-Dimensional Fluorescence Difference Spectroscopy of ZnO and Mg Composites in the Detection of Physiological Protein and RNA Interactions

Two-dimensional fluorescence difference spectroscopy (2-D FDS) was used to determine the unique spectral signatures of zinc oxide (ZnO), magnesium oxide (MgO), and 5% magnesium zinc oxide nanocomposite (5% Mg/ZnO) and was then used to demonstrate the change in spectral signature that occurs when physiologically important proteins, such as angiotensin-converting enzyme (ACE) and ribonuclease A (RNase A), interact with ZnO nanoparticles (NPs). When RNase A is bound to 5% Mg/ZnO, the intensity is quenched, while the intensity is magnified and a significant shift is seen when torula yeast RNA (TYRNA) is bound to RNase A and 5% Mg/ZnO. The intensity of 5% Mg/ZnO is quenched also when thrombin and thrombin aptamer are bound to the nanocomposite. These data indicate that RNA–protein interaction can occur unimpeded on the surface of NPs, which was confirmed by gel electrophoresis, and importantly that the change in fluorescence excitation, emission, and intensity shown by 2-D FDS may indicate specificity of biomolecular interactions.