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8-oxo guanine DNA glycosylase (8-oxoG DNA glycosylase), a crucial DNA repair enzyme, is essential for maintaining genome integrity and preventing diseases caused by DNA oxidative damage. Imaging 8-oxoG DNA glycosylase in living cells requires a dependable technique. In this study, we designed a DNAzyme-modified DNA tetrahedral nanomachine (DTDN) powered by 8-oxoG restoration. Incorporating a molecular beacon probe (MB), the constructed platform was used for amplified in situ monitoring of 8-oxoG DNA glycosylase. Under normal conditions, duplexing with a complementary strand modified with two 8-oxoG sites inhibited the activity of DNAzyme. The restoration of DNAzyme activity by the repair of intracellular 8-oxoG DNA glycosylase on 8-oxoG bases can initiate a signal amplification reaction. This detection system can detect 8-oxoG DNA glycosylase activity linearly between 0 and 20 U mL−1, with a detection limit as low as 0.52 U mL−1. Using this method, we were able to screen 14 natural compounds and identify 6 of them as 8-oxoG DNA glycosylase inhibitors. In addition, a novel approach was utilized to assess the activity of 8-oxoG DNA glycosylase in living cells. In conclusion, this method provides a universal tool for monitoring the activity of 8-oxoG DNA glycosylase in vitro and in living cells, which holds great promise for elucidating the enzyme's functionality and facilitating drug screening endeavors. [ABSTRACT FROM AUTHOR]

Here, we report a simple but effective nose/tongue-mimic sensor array based on HAuCl4/3,3′,5,5′-tetramethylbenzidine (TMB) for colorimetric discrimination and determination of antioxidants. Two concentrations of HAuCl4 were employed as receptor units to construct the colorimetric sensor array. The sensing strategy is based on the fact that HAuCl4 with different concentrations (0.08 and 0.03 mM) could oxidize TMB to oxidized TMB (oxTMB), resulting in a blue and green color solution, respectively, corresponding to an absorption peak centered at 440 nm and 657 nm. However, the presence of different antioxidants could cause the reduction in HAuCl4, leading to the fading of the blue and green color and the decrease in the absorbance at 440 nm and 657 nm to varying degrees. Based on the above phenomena, by taking advantage of linear discriminant analysis (LDA), five antioxidants (i.e. ascorbic acid (AA), melatonin (MT), uric acid (UA), tannic acid (TCA), and glycine (Gly)) at five concentrations (200, 120, 60, 20, and 1 nM) were successfully discriminated both in buffer and serum. More importantly, this approach is simple, fast, and without the use of any nanomaterials. [ABSTRACT FROM AUTHOR]

As a highly conserved damage repair protein, except for hydrolysis of DNA–RNA heteroduplex endonucleolytically, RNase H can cleave RNA–DNA junctions in Okazaki fragment processing through its junction ribonuclease (JRNase) activity. We report here a real time fluorescence method for detecting JRNase activity of RNase H with high accuracy by applying chimeric molecular beacons as substrates. The detection limit of E. coli RNase H is 0.5 U ml−1. The Km and kcat are 20 nM and 0.6 s−1, respectively. In addition, we used the method to investigate the effect of chemical drugs on the enzyme and found that both penicillin and streptomycin sulfate inhibit its activity with the IC50 values of 0.2 and 0.07 mM, respectively. Finally, we applied the method to reliably detect the JRNase level in tumor cells. In summary, these data indicate that the simple, rapid and sensitive method can be hopefully applied for high-throughput detection of samples and drug screening in vitro. [ABSTRACT FROM AUTHOR]

A simple chemodosimeter array has been successfully achieved for the detection and discrimination of different palladium species by using principal component analysis. [ABSTRACT FROM AUTHOR]

The detection of ultralow heavy metal ion concentration is highly significant for protecting human health and maintaining the stability of the ecological environment. Herein, a microfiber interferometer chemical sensor for the detection of Ni2+ ions was proposed and experimentally demonstrated. The microfiber sensor was coated with an ion-imprinted chitosan polymer using Ni2+ as the template ion. Experimental results demonstrated a high sensitivity of 0.0454 nm nM−M for detect-ing Ni2+ in the range of 10 nM to 100 nM, and a limit of detection as low as 6.5 nM was achieved. The microfiber sensor was verified using two different non-template heavy ions, Cu2+ and Cr3+, and was determined to be highly selective to Ni2+. Furthermore, the regeneration characteristics of the sensor were experimentally assessed by three repeated adsorption–desorption cycles, and the results showed that the microfiber sensor achieved good stability without a significant loss in sensitivity. Besides, the detecting tests of Ni2+ in lake water and industrial sewage samples demonstrated the sensor's practical application. This proposed sensor has the advantages of simple configuration, high selectivity and sensitivity, fast response, and the ability to serve as a platform for water safety monitoring and remote sensing. [ABSTRACT FROM AUTHOR]

Peroxides in edible oils, whose amounts are measured using the peroxide value, are closely related to human health. Long-term consumption of edible oils with high peroxide values can lead to a variety of human diseases, which highlights the significance of examining oil types and their corresponding peroxide values. For identifying a wide range of edible oils, we established a colorimetric sensor array based on the halogen ion exchange between CsPbBr3 and two iodides (octadecylammonium iodide (ODAI) and ZnI2). Different kinds of edible oils contain distinct peroxidic substances that have the distinct ability to oxidize iodides. After specific types of edible oils react with excess iodides (ODAI and ZnI2), different amounts of residual iodides are left for further halogen exchange with CsPbBr3, resulting in various colorimetric responses, measured in RGB (red/green/blue) values, under fluorescent light. Based on RGB pattern analysis as fingerprints using two anion exchangers (ODAI and ZnI2), our proposed colorimetric sensor array was proved by linear discriminant analysis (LDA) to have an ability to accurately distinguish edible oils at a minimal volumetric concentration of 6.67% in seven real samples. [ABSTRACT FROM AUTHOR]

Superior sensitive, selective, and repeatable real-time detection of low concentrations of benzene vapor is vitally important for environmental protection and human health. A benzene vapor sensor using three-dimensional photonic crystals (3-D PCs) based on zeolitic imidazolate framework-8@graphene quantum dots (ZIF-8@GQDs) was proposed. The 3-D PCs were acquired by centrifuging ZIF-8@GQDs pseudo-solutions, which were prepared via hydrothermal methods. The application of the ZIF-8@GQDs 3-D PCs sensor for optical benzene vapor detection via the strong π–π stacking interactions and large specific surface area and abundant open-framework structure of the ZIF-8@GQDs was investigated. The ZIF-8@GQDs 3-D PCs sensor exhibits a more sensitive response to benzene vapor compared with the ZIF-8 3-D PCs sensor. The relationship between the wavelength shift and the benzene vapor concentration was demonstrated to be linear. Additionally, the ZIF-8@GQDs 3-D PCs sensor presents a fast optical response and recovery times of 1 s and 7 s for 200 ppm benzene vapor detection, the benzene vapor detection limit can reach 1 ppm, and the deviation of the reflected wavelength varied within 2 nm after 10 cycles. Moreover, the fabricated ZIF-8@GQDs 3-D PCs sensor exhibited reliability and exceptional thermal and long-time storage stability, demonstrating great potential for practical benzene vapor sensing applications. [ABSTRACT FROM AUTHOR]

Ribonuclease H is essential for the research and development of complex pathema. The high rigidity and versatility of DNA tetrahedrons means they are often used in biosensing systems. Inspired by "radar" technology, we proposed a radar-like monitor to detect RNase H activity in vitro and in situ by integrating DNA tetrahedral elements. The structure of a radar-like monitor was self-assembled from five customized single nucleic acid strands. Four DNA strands were assembled as DNA tetrahedrons with a long strand labeled by Dabcyl (quencher) at one of the apexes, while the fifth strand (DNA–RNA heterozygous strand) was labeled with a FAM (Fluorophore) hybrid with a long strand. The fluorescence was quenched because the fluorophore and the quencher were very close. In the presence of RNase H, the RNA chain was hydrolyzed and the fluorophore released, resulting in fluorescence recovery. The radar-like monitor was used to detect the RNase H activity in vitro with a detection limit of 0.01 U mL−1. Based on the RNase H activity detection and the inhibitory effect of natural-compounds-targeting RNase H, three inhibitors were obtained among 35 compounds extracted from Panax japonicus. Therefore, the radar-like monitor was successfully used to detect RNase H activity in situ due to the long-term anti-DNase I effect of the RNA/DNA hybrid structure and DNA tetrahedrons structure. Overall, this radar-like monitor can effectively avoid false-positive signals and significantly improve the accuracy, precision, and reliability of detection. It is expected that the development of such an intelligent nano-platform will open the door to cancer diagnosis and treatment in clinical systems. [ABSTRACT FROM AUTHOR]

Hepatitis C virus (HCV) is a major cause of chronic liver disease, which affects 2–3% of the world population. Until now, the early detection of HCV has been a great challenge, especially for those who live in developing countries. In this study, we developed a novel and ultrasensitive assay for the detection of HCV RNA based on the reduced graphene oxide nanosheets (rGONS) and hybridization chain reaction (HCR) amplification technique. This detection system contains a pair of single fluorophore-labeled hairpin probes that can freely exist in the solution in the absence of target RNA. The introduction of target RNA can robustly trigger a HCR with the two probes and produce long nanowires containing a double-stranded structure. The weak adsorption to rGONS makes the long nanowires emit a strong fluorescence. Using this enzyme-free amplification strategy, we developed a new method for the HCV RNA assay with a detection limit of 10 fM, which is far more sensitive than the common GO-based fluorescence method. Furthermore, the new method exhibits high selectivity for the discrimination of perfectly complementary and mismatched sequences. Finally, the new method was successfully used as a HCV RNA assay in biological samples with a strong anti-interference capability in complicated environments. In summary, these remarkable characteristics of the new method highlight its potential use in a clinical sample primary screening. [ABSTRACT FROM AUTHOR]

As a highly conserved damage repair protein, Fpg can specifically recognize and digest 8-oxoG from a damaged DNA backbone. Meanwhile, DNAzyme, a single-stranded DNA with enzymatic activity, can cleave RNA in the presence of cofactors. In this study, we established a highly sensitive method for Fpg assay using a DNAzyme-mediated signal cascade amplification strategy. Based on the Fpg-dependent fluorescence response of the “turn-on” manner, we could reliably determine Fpg activity down to 0.14 U mL−1 with a linear response from 0.10 to 40 U mL−1 under optimal conditions. In addition, this strategy was successfully applied to analyze the kinetic parameter of Fpg with Km of 0.061 μM. Furthermore, the developed sensing system was used to screen the regulators of Fpg from natural compounds and antibiotics. These results indicated that all of the 14 natural compounds and 6 kinds of antibiotics deferentially showed an active effect on Fpg in vitro. In summary, these results show that the method not only provides an alternative for monitoring Fpg activity but also shows great potential for drug screening in the future. [ABSTRACT FROM AUTHOR]

T4 polynucleotide kinase (PNK) is the primary member of the 5′-kinase family that can transfer the γ-phosphate residue of ATP to the 5′-hydroxyl group of oligonucleotides. In this article, using the differential quenching ability of reduced graphene oxide (rGO) towards the fluorophore-labeled DNA probe, we propose a novel method for detecting T4 PNK activity assisted by ligase reaction. Under the optimized conditions, the detection limit of T4 PNK was estimated to be 0.0002 U μL−1 in the linear region of 0.001 U μL−1–0.1 U μL−1. Additionally, the developed method was used to screen regulators of T4 PNK from natural compounds. The compound f isolated from the root of Kadsura coccinea (Lem.) A.C. Smith was found to stimulate T4 PNK activity in a concentration-dependent manner in vitro. Finally, the method was used to monitor the relation of T4 PNK activity with pelvic inflammatory disease (PID). The results demonstrated that the development of this disease could inhibit T4 PNK activity to some extent. In summary, the above data indicate that the method not only provides a universal platform for monitoring T4 PNK activity, but also shows great potential to be used in drug screening and clinic diagnosis. [ABSTRACT FROM AUTHOR]

A novel dual-photoluminescence probe for Cu2+ has been developed, in which the graphene quantum dots with blue emission and CdTe QDs with yellow emission act as internal standard and probe, respectively. The photoluminescence probe exhibited selective sensing for Cu2+ with a limit of detection (3SD/k) of 5.3 × 10−8 M and showed its potential application in visual imaging. The results indicated that the constructed probe can be employed for sensing Cu2+ by the naked eye, and also for monitoring intracellular Cu2+. [ABSTRACT FROM AUTHOR]

Schizophrenia is a severely devastating mental disorder, the pathological process of which is proposed to be associated with the dysfunction of dopaminergic transmission. Our previous results have demonstrated slower kinetics of transmitter release (glutamate release in hippocampus and norepinephrine release in adrenal slice) in a schizophrenia model, dysbindin null-sandy mice. However, whether dopaminergic transmission in the nigrostriatal pathway contributes to the pathology of dysbindin−/− mice remains unknown. Here, we have provided a step-by-step protocol to be applied in the in vivo amperometric recording of dopamine (DA) release from the mouse striatum evoked by an action potential (AP) pattern. With this protocol, AP pattern-dependent DA release was recorded from dysbindin−/− mice striatum in vivo. On combining amperometric recording in slices and electrophysiology, we found that in dysbindin−/− mice, (1) presynaptically, AP-pattern dependent dopamine overflow and uptake were intact in vivo; (2) the recycling of the dopamine vesicle pool remained unchanged. (3) Postsynaptically, the excitability of medium spiny neuron (MSN) was also normal, as revealed by patch-clamp recordings in striatal slices. Taken together, in contrast to reduced norepinephrine release in adrenal chromaffin cells, the dopaminergic transmission remains unchanged in the nigrostriatal pathway in dysbindin−/− mice, providing a new insight into the functions of the schizophrenia susceptibility gene dysbindin. [ABSTRACT FROM AUTHOR]