Self-assembly of cascade nanoenzyme glucose oxidase encapsulated in copper benzenedicarboxylate for wearable sweat-glucose colorimetric sensors with smartphone readout.

BACKGROUND: With the advent of personalized medical approaches, precise and tailored treatments are expected to become widely accepted for the prevention and treatment of diabetes. Paper-based colorimetric sensors that function in combination with smartphones have been rapidly developed in recent years because it does not require additional equipment and is inexpensive and easy to perform. In this study, we developed a portable, low-cost, and wearable sweat-glucose detection device for in situ detection. RESULTS: The sensor adopted an integrated biomimetic nanoenzyme of glucose oxidase (GOx) encapsulated in copper 1, 4-benzenedicarboxylate (CuBDC) (GOx@CuBDC) through a biomimetic mineralization process. CuBDC exhibited a peroxide-like effect, cascade catalytic effect with the encapsulated GOx, and increased the enzyme stability. GOx@CuBDC and 3,3,5,5-tetramethylbenzidine were combined to form a hybrid membrane that achieved single-step paper-based glucose detection. SIGNIFICANCE AND NOVELTY: This GOx@CuBDC-based colorimetric glucose sensor was used to quantitatively analyze the sweat-glucose concentration with smartphone readings. The sensor exhibited a good linear relationship over the concentration range of 40-900 µM and a limit of detection of 20.7 µM (S/N = 3). Moreover, the sensor performed well in situ monitoring and in evaluating variations based on the consumption of foods with different glycemic indices. Therefore, the fabricated wearable sweat-glucose sensors exhibited optimal practical application performance.

PAIT effect: Padlock activator inhibits the trans-cleavage activity of CRISPR/Cas12a.

The CRISPR/Cas12a system is increasingly used in biosensor development. However, high background signal and low sensitivity for the non-nucleic acid targets detection is challenging. Here, a padlock activator which could inhibit the trans-cleavage activity of CRISPR/Cas12a system in the intact form by steric hindrance effect (PAIT effect) was designed for non-nucleic acid targets detection. The PAIT effect disappeared when padlock activator was separated into two split activators. To verify the feasibility of padlock activator, a Ca2+ sensor was developed based on PAIT effect with the assistance of DNAzyme, activity of which was Ca2+ dependent. In the presence of Ca2+, DNAzyme was activated to cleave its substrate, a padlock activator modified with adenine ribonucleotide, into split padlock activators which would trigger the trans-cleavage activity of Cas12a to generate fluorescence. There was a mathematical relationship between the fluorescence intensity and the logarithm of Ca2+ concentration ranging from 10 pM to 1 nM, with a limit of detection of 3.98 pM. The little interference of Mg2+, Mn2+, Cd2+, Cu2+, Na+, Al3+, K+, Fe2+, and Fe3+ indicated high selectivity. Recovery ranged from 93.32% to 103.28% with RSDs from 1.87% to 12.74% showed a good accuracy and reliability. Furthermore, the proposed sensor could be applied to detect Ca2+ in mineral water, milk powder and urine. The results were consistent with that of flame atomic absorption spectroscopy. Thus, PAIT effect is valuable for expanding the application boundary of CRISPR/Cas12a system.

Association between dinner-bedtime interval and type 2 diabetes mellitus: a large-scale cross-sectional study.

Objective: Glucose metabolism is impacted by circadian disruption. Dinner-bedtime interval (DBI) was an accessible indicator to reflect the alignment between dinner time and circadian clock. We aimed to investigate the association of DBI with type 2 diabetes mellitus (T2DM). Methods: 7676 adult subjects from the Henan Rural Cohort were included. Their demographic information including dinner time and bedtime was collected. Fasting venous blood samples were collected for biochemical determinations. Generalized linear regression model was used to analyze the factors influencing DBI. Furthermore, logistic regression incorporated with restricted cubic spline model was applied to evaluate the association between DBI and T2DM. Results: The results of multiple linear regression model showed that age (ß: -0.018, 95% CI: -0.021, -0.015) was negatively correlated with DBI. Female (ß: 0.311, 95% CI: 0.229, 0.393), junior high school education (ß: 0.246, 95% CI: 0.187, 0.306), high school education or above (ß: 0.346, 95% CI: 0.259, 0.433), average monthly income with 1000-1999 CNY(0.102, 95% CI: 0.032, 0.171), average monthly income ≥ 2000 CNY (ß: 0.164, 95% CI: 0.076, 0.251), moderate physical activity (ß: 0.134, 95% CI: 0.071, 0.197), current smokers (ß: 0.214, 95% CI: 0.118, 0.309), current drinkers (ß: 0.099, 95% CI: 0.008, 0.190) were positively correlated with DBI. Furthermore, DBI was significantly associated with T2DM (adjusted OR: 0.910, 95%CI: 0.845-0.979, P = 0.012). DBI longer than 3 h was associated with decreased risk of T2DM (adjusted OR: 0.773, 95%CI: 0.648-0.921, P = 0.004). Conclusions: DBI larger than 3 h is beneficial to T2DM prevention. Further investigation is required to verify the association.

Multiplexed Detection Strategies for Biosensors Based on the CRISPR-Cas System.

A growing number of applications require simultaneous detection of multiplexed nucleic acid targets in a single reaction, which enables higher information density in combination with reduced assay time and cost. Clustered regularly interspaced short palindromic repeats (CRISPR) and the CRISPR-Cas system have broad applications for the detection of nucleic acids due to their strong specificity, high sensitivity, and excellent programmability. However, realizing multiplexed detection is still challenging for the CRISPR-Cas system due to the nonspecific collateral cleavage activity, limited signal reporting strategies, and possible cross-reactions. In this review, we summarize the principles, strategies, and features of multiplexed detection based on the CRISPR-Cas system and further discuss the challenges and perspective.

Antibiotic-Fe3O4 nanoparticles with highly efficient catalytic activity for enhanced chemiluminescence detection of tetracyclines residues in foods.

Tetracyclines (TCs) are the most commonly antimicrobial agents that used in livestock production worldwide. It is important to supervise tetracyclines residues in food for environmental monitoring and food safety. In this study, a novel, label-free chemiluminescence (CL) assay without antibody was established. Fe3O4 NPs could facilitate the CL interaction between luminol and H2O2. Interestingly, TCs could enhance the catalytic ability of Fe3O4 NPs and result in a further amplification of the CL intensity. The CL intensity varied linearly with the concentration of tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), and ranging from 10-2400, 10-2800, and 5-2100 nmol/L, respectively; The limits of detection were 4 nmol/L for TC, 6 nmol/L for OTC, and 2 nmol/L for CTC. This CL strategy was applied successfully in testing three TCs residues in milk, eggs and honey samples with more sensitive results, which provided an alternative strategy for monitoring the correct use of TCs.

Ratiometric CRISPR/Cas12a-Triggered CHA System Coupling with the MSRE to Detect Site-Specific DNA Methylation.

The precise determination of DNA methylation at specific sites is critical for the timely detection of cancer, as DNA methylation is closely associated with the initiation and progression of cancer. Herein, a novel ratiometric fluorescence method based on the methylation-sensitive restriction enzyme (MSRE), CRISPR/Cas12a, and catalytic hairpin assembly (CHA) amplification were developed to detect site-specific methylation with high sensitivity and specificity. In detail, AciI, one of the commonly used MSREs, was employed to distinguish the methylated target from nonmethylated targets. The CRISPR/Cas12a system was utilized to recognize the site-specific target. In this process, the protospacer adjacent motif and crRNA-dependent identification, the single-base resolution of Cas12a, can effectively ensure detection specificity. The trans-cleavage ability of Cas12a can convert one target into abundant activators and can then trigger the CHA reaction, leading to the accomplishment of cascaded signal amplification. Moreover, with the structural change of the hairpin probe during CHA, two labeled dyes can be spatially separated, generating a change of the Förster resonance energy transfer signal. In general, the proposed strategy of tandem CHA after the CRISPR/Cas12a reaction not only avoids the generation of false-positive signals caused by the target-similar nucleic acid but can also improve the sensitivity. The use of ratiometric fluorescence can eradicate environmental effects by self-calibration. Consequently, the proposed approach had a detection limit of 2.02 fM. This approach could distinguish between colorectal cancer and precancerous tissue, as well as between colorectal patients and healthy people. Therefore, the developed method can serve as an excellent site-specific methylation detection tool, which is promising for biological and disease studies.

MicroRNA Sensors Based on CRISPR/Cas12a Technologies: Evolution From Indirect to Direct Detection.

MicroRNA (miRNA) has emerged as a promising biomarker for disease diagnosis and a potential therapeutic targets for drug development. The detection of miRNA can serve as a noninvasive tool in diseases diagnosis and predicting diseases prognosis. CRISPR/Cas12a system has great potential in nucleic acid detection due to its high sensitivity and specificity, which has been developed to be a versatile tool for nucleic acid-based detection of targets in various fields. However, conversion from RNA to DNA with or without amplification operation is necessary for miRNA detection based on CRISPR/Cas12a system, because dsDNA containing PAM sequence or ssDNA is traditionally considered as the activator of Cas12a. Until recently, direct detection of miRNA by CRISPR/Cas12a system has been reported. In this review, we provide an overview of the evolution of biosensors based on CRISPR/Cas12a for miRNA detection from indirect to direct, which would be beneficial to the development of CRISPR/Cas12a-based sensors with better performance for direct detection of miRNA.

4-Vinylbenzodioxinones as a new type of precursor for palladium-catalyzed (4+3) cycloaddition of azomethine imines.

In this paper, benzo-fused cyclic carbonates were designed and synthesized as a new type of precursor of π-allylpalladium zwitterionic intermediates, and were applied in Pd-catalyzed diastereo- and enantioselective (4+3) cycloaddition with C,N-cyclic azomethine imines, leading to various biologically important 1,3,4-benzoxadiazepine derivatives in 43-99% yields with 6 : 1 to >20 : 1 dr and up to 95% ee.

Non-canonical CRISPR/Cas12a-based technology: A novel horizon for biosensing in nucleic acid detection.

Nucleic acids are essential biomarkers in molecular diagnostics. The CRISPR/Cas system has been widely used for nucleic acid detection. Moreover, canonical CRISPR/Cas12a based biosensors can specifically recognize and cleave target DNA, as well as single-strand DNA serving as reporter probe, which have become a super star in recent years in the field of nucleic acid detection due to its high specificity, universal programmability and simple operation. However, canonical CRISPR/Cas12a based biosensors are hard to meet the requirements of higher sensitivity, higher specificity, higher efficiency, larger target scope, easier operation, multiplexing, low cost and diversified signal reading. Then, advanced non-canonical CRISPR/Cas12a based biosensors emerge. In this review, applications of non-canonical CRISPR/Cas12a-based biosensors in nucleic acid detection are summarized. And the principles, peculiarities, performances and perspectives of these non-canonical CRISPR/Cas12a based biosensors are also discussed.

Phosphine-Catalyzed (3 + 2) Annulation of γ-Substituted Cinnamic Aldehyde-Derived Morita-Baylis-Hillman Carbonates through Remote Activation.

A series of γ-substituted Morita-Baylis-Hillman (MBH) carbonates were synthesized and subjected to phosphine-catalyzed annulations with electrophilic exocyclic alkenes, giving various valuable spirocyclopentenes in moderate to excellent yields with moderate to excellent diastereoselectivities. A large scope of MBH carbonates bearing γ-hydrogen, alkenyl, and alkynyl substituents was well tolerated. The annulation unprecedentedly involves ß-, γ-, and δ-carbons of MBH carbonates.

Palladium-Catalyzed Asymmetric (3 + 2) Cycloaddition of 5-Allenyloxazolidine-2,4-Diones with Barbiturate-Derived Alkenes: Synthesis of Spirobarbiturate-γ-Lactams.

The 5-allenyloxazolidine-2,4-diones had been synthesized as novel precursors of π-allyl palladium zwitterion and were applied in a palladium-catalyzed enantioselective (3 + 2) annulation by using barbiturate-derived alkenes as the reaction partner in the presence of an axially chiral phosphoramidite ligand. This reaction proceeded smoothly under mild reaction conditions, affording highly functionalized spirobarbiturate-γ-lactam derivatives in excellent yields along with high diastereo- and enantioselectivities. The scale-up reaction and further transformation of the product were also successful.

Association between dinner timing and glucose metabolism in rural China: A large-scale cross-sectional study.

OBJECTIVES: Meal timing is a major risk factor for metabolic disease. The aim of this study was to assess the relationship between dinner timing and glucose metabolism in the rural Chinese population. METHODS: This cross-sectional study included 7701 participants from a Henan rural cohort study. Basic information was collected by in-person questionnaires. Multiple linear regression analysis was used to evaluate the relationship between dinner timing and fasting insulin (FINS), fasting plasma glucose (FPG), and homeostatic model assessment for insulin resistance (HOMA-IR). Restricted cubic spline was employed to investigate the dose-response relationship between dinner timing and FINS, FPG, and HOMA-IR. A generalized linear model was used to explore the interaction effect of age and dinner timing on FINS, FPG, and HOMA-IR. RESULTS: After adjusting for confounding factors, FINS concentration was reduced by 0.482 mmol/L (P < 0.001) for each hour delay in dinner timing. Furthermore, the HOMA-IR index decreased by 0.122 mmol/L for each hour delay. The results indicated a noticeable trend of decreasing values associated with later dinner timing (FINS: Poverall association < 0.001, Pnonlinear association = 0.144; HOMA-IR: Poverall association = 0.001, Pnonlinear association = 0.186). The interaction between age and dinner time significantly correlated with FINS and HOMA-IR (P < 0.05). This relationship was statistically significant before 69 y (P < 0.05). CONCLUSION: A significant association between dinner timing and glucose metabolism was observed in the rural Chinese population. Delayed dinner timing may be associated with lower fasting insulin. The negative effect of dinner timing on FINS and HOMA-IR was diminished with age.

Fluorescence quenching determination of tetracyclines based on the synergistic oxidation effect between Fe3O4nanoparticles and tetracyclines.

In recent years, tetracyclines (TCs) is a hot research topic. Herein, we report an interesting discovery using the complexation of oxytetracycline and metal ions. In this study, according to the properties of Fe3O4nanoparticles (Fe3O4NPs) as a nanoenzyme, it can be used to catalyze the oxidation of KI by H2O2to produceI3-,while at the same timeI3-binds to rhodamine 6G (Rh6G) to form a conjoined particle (Rh6G ∼ I3)n, leading to a decrease in the fluorescence intensity of Rh6G. However, in the presence of TCs, Fe3O4NPs have a synergistic effect with TCs, leading to enhanced catalytic activity, as well as better selectivity compared to the activity of other reducing enzymes. Consequently,the fluorescent signal based on a resonance scattering effect between Rh6G andI3-is dependent on the concentration of TCs, thus achieving highly facile and robust detection of TCs. The limits of detection (LOD) of the method were 20 nM, 10 nM and 40 nM for oxytetracycline(OTC), tetracycline(TC) and chlortetracycline(CTC), respectively. Most importantly, the method can be successfully applied to the detection of TCs in milk, eggs, and honey. The recoveries of spiked samples ranged from 83.11 to 118.95%. Thus, a stable, hands-on strategy for the detection of TCs is proposed, which has potential applications in the field of food safety and environmental protection.

Phosphine-Catalyzed Tandem Annulation of Allenylic Alcohols with 1,1-Dicyanoalkenes.

The phosphine-catalyzed tandem annulation of allenylic alcohols with 1,1-dicyanoalkenes has been developed, giving various bicyclic tetrahydrocyclopentafuran derivatives in 40-89% yields with moderate to excellent diastereoselectivities. The fused ring was furnished through a sequential (3 + 2) annulation/nucleophilic addition reaction. The unusual nucleophilic addition of an alkoxide ion to a cyano group led to a formation of tetrahydrofuran ring having an imino substituent.

Both early and late maternal age at childbirth is associated with increasing odds of central obesity in offspring.

OBJECTIVE: Despite studies on offspring obesity and delayed parenthood, little attention has been paid to the central obesity of offspring. The purpose of this study was to test the hypothesis that maternal age at childbirth (MAC) was associated with central obesity in offspring among the adult population, and fasting insulin may play a role in this association as a mediating factor. METHODS: A total of 423 adults (mean age 37.9 years, 37.1% female) were included. Information about maternal variables and other confounders was collected by face-to-face interview. Waist circumference and insulin were determined through physical measurements and biochemical examinations. Logistic regression model and restricted cubic spline model were used to analyze the relationship between MAC and central obesity of offspring. The mediating effect of fasting insulin levels on association between MAC and offspring waist circumference was also analyzed. RESULTS: There was a nonlinear relationship between MAC and central obesity in offspring. Compared with subjects with MAC 27-32 years, those with MAC 21-26 years (OR = 1.814, 95% CI: 1.129-2.915) and MAC ≥33 years (OR = 3.337, 95% CI: 1.638-6.798) had higher odds to develop central obesity. Offspring fasting insulin was also higher in MAC 21-26 years and MAC ≥33 years compared with those with MAC 27-32 years. Taking the group MAC 27-32 years as reference, the mediating effect of fasting insulin levels on the waist circumference was 20.6% and 12.4% for MAC 21-26 years and ≥ 33 years, respectively. CONCLUSION: MAC 27-32 years has the lowest odds of central obesity in offspring. Fasting insulin levels may have a partial mediating effect on the association between MAC and central obesity.

Fungicide-inspired precursors of π-allylpalladium intermediates for palladium-catalyzed decarboxylative cycloadditions.

Inspired by a fungicide, we designed 5-vinyloxazolidine-2,4-diones as new precursors of π-allylpalladium zwitterionic intermediates and developed palladium-catalyzed asymmetric (5 + 3) cycloaddition with azomethine imines and (3 + 2) cycloaddition with 1,1-dicyanoalkenes. Both reactions proceeded smoothly under mild reaction conditions to produce various chiral heterocyclic compounds in high yields with excellent enantioselectivities. These results revealed that 5-vinyloxazolidine-2,4-diones were a type of suitable precursor for palladium catalysis and will find extensive applications in Pd-catalyzed reactions such as cycloaddition and allylic alkylation.

Polymeric Memristor Based Artificial Synapses with Ultra-Wide Operating Temperature.

Neuromorphic electronics, being inspired by how the brain works, hold great promise to the successful implementation of smart artificial systems. Among several neuromorphic hardware issues, a robust device functionality under extreme temperature is of particular importance for practical applications. Given that the organic memristors for artificial synapse applications are demonstrated under room temperature, achieving a robust device performance at extremely low or high temperature is still utterly challenging. In this work, the temperature issue is addressed by tuning the functionality of the solution-based organic polymeric memristor. The optimized memristor demonstrates a reliable performance under both the cryogenic and high-temperature environments. The unencapsulated organic polymeric memristor shows a robust memristive response under test temperature ranging from 77 to 573 K. Utilizing X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (ToF-SIMS) depth profiling, the device working mechanism is unveiled by comparing the compositional profiles of the fresh and written organic polymeric memristors. A reversible ion migration induced by an applied voltage contributes to the characteristic switching behavior of the memristor. Herein, both the robust memristive response achieved at extreme temperatures and the verified device working mechanism will remarkably accelerate the development of memristors in neuromorphic systems.

Association between Meal Frequency and Type 2 Diabetes Mellitus in Rural Adults: A Large-Scale Cross-Sectional Study.

Diet frequency may potentially influence metabolic health. However, general population-based evidence on the association between meal frequency and type 2 diabetes mellitus (T2DM) remains limited and inconclusive. Thus, this study aimed to investigate the association between meal frequency and T2DM in resource limited area. A total of 29,405 qualified participants were enrolled from the Henan rural cohort study. Data on meal frequency were collected through a validated face-to-face questionnaire survey. Logistic regression models were utilized to explore the association between meal frequency and T2DM. Compared with 21 times per week meal frequency group, the adjusted odds ratios (ORs) and 95% confidence intervals (95%CIs) were 0.75 (0.58, 0.95) and 0.70 (0.54, 0.90) for 16-20 times/week group and 14-15 times/week group, respectively. For the analysis of the three meals, significant associations were only found between dinner frequency and T2DM. Compared with seven times per week dinner group, the ORs (95%CIs) were 0.66 (0.42, 0.99) and 0.51 (0.29, 0.82) for the group with three to six times/week and zero to two times/week. Reduced meal frequency, especially dinner frequency, was associated with lower prevalence of T2DM, which suggests that an appropriate reduction in meal frequency per week may have a role in decreasing the risk of T2DM.

Locus-Specific Detection of DNA Methylation: The Advance, Challenge, and Perspective of CRISPR-Cas Assisted Biosensors.

Deoxyribonucleic acid (DNA) methylation is one of the epigenetic characteristics that result in heritable and revisable phenotype changes but without sequence changes in DNA. Aberrant methylation occurring at a specific locus was reported to be associated with cancers, insulin resistance, obesity, Alzheimer's disease, Parkinson's disease, etc. Therefore, locus-specific DNA methylation can serve as a valuable biomarker for disease diagnosis and therapy. Recently, Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems are applied to develop biosensors for DNA, ribonucleic acid, proteins, and small molecules detection. Because of their highly specific binding ability and signal amplification capacity, CRISPR-Cas assisted biosensor also serve as a potential tool for locus-specific detection of DNA methylation. In this perspective, based on the detection principle, a detailed classification and comprehensive discussion of recent works about the latest advances in locus-specific detection of DNA methylation using CRISPR-Cas systems are provided. Furthermore, current challenges and future perspectives of CRISPR-based locus-specific detection of DNA methylation are outlined.

Universal DNAzyme walkers-triggered CRISPR-Cas12a/Cas13a bioassay for the synchronous detection of two exosomal proteins and its application in intelligent diagnosis of cancer.

Exosomal proteins are considered to be promising indicators of cancer. Herein, a novel DNAzyme walkers-triggered CRISPR-Cas12a/Cas13a strategy was proposed for the synchronous determination of exosomal proteins: serum amyloid A-1 protein (SAA1) and coagulation factor V (FV). In this design, the paired antibodies were used to recognize targets, thereby ensuring the specificity. DNAzyme walkers were employed to convert the contents of SAA1 and FV into activators (P1 and P2), and one target can produce abundant activators, thus achieving an initial amplification of signal. Furthermore, the P1 and P2 can activate CRISPR-Cas12a/Cas13a system, which in turn trans-cleaves the reporters, enabling a second amplification and generating two fluorescent signals. The assay is highly sensitive (limits of detection as low as 30.00 pg/mL for SAA1 and 200.00 pg/mL for FV), highly specific and ideally accurate. More importantly, it is universal and can be used to detect both non-membrane and membrane proteins in exosome. Besides, the method can be successfully applied to detect SAA1 and FV in plasma exosomes to differentiate between lung cancer patients and healthy individuals. To explore the application of the developed method in tumor diagnosis, a deep learning model based on the expressions of SAA1 and FV was developed. The accuracy of this model can achieve 86.96%, which proves that it has a promising practical application capacity. Thus, this study does not only provide a new tool for the detection of exosomal proteins and cancer diagnosis, but also propose a new strategy to detect non-nucleic acid analytes for CRISPR-Cas system.