An electrochemical aptasensor based on target triggered multiple-channel DNAzymes cycling amplification strategy with PtFe@Co-MOF as signal amplifier.

A novel electrochemical aptasensor for the detection of Aflatoxin B1 (AFB1) was developed for the first time by using the target-triggered multiple-channel deoxyribozymes (DNAzymes) cycling amplified assay with Pt Fe doped NH2-Co-MOF (PtFe@Co-MOF) as a signal amplifier. In the presence of AFB1, a self-assembling cross-over nucleic structure could be triggered by AFB1 via two aptamers' structure switching for strand displacement, resulting in four channels of Mg2+-dependent DNAzyme recycling simultaneously to multiply the detection signals. These DNAzymes cyclically split the substrate sequence to release the PtFe@Co-MOF labeled detection probe (DP), which is subsequently hybridized with the capture probes on the Au-deposited glassy carbon electrode. The fabrication procedure was characterized by differential pulse voltammetry, and the results of the morphological and element composition characteristics methods were analyzed to determine the successful preparation of PtFe@Co-MOF. The limit of detection (LOD) for AFB1 detection was 2 pg mL-1 with a linear range from 5 pg mL-1 to 80 ng mL-1. By comparison, the enhanced detection sensitivity has been found to originate from the efficient shearing of DNAzymes, enhanced peroxidase-like capability, and multiple active sites of PtFe@Co-MOF. Besides, this aptasensor showed high specificity for AFB1 compared with similar mycotoxins and exhibited high accuracy with low experimental cost and easy operation. Furthermore, the unique design of electrochemical aptasensors could provide a promising platform for the onsite determination of AFB1, as well as other targets by replacing the aptamer and other core recognition sequences.

Efficacy and Safety of Phentermine/Topiramate in Adults with Overweight or Obesity: A Systematic Review and Meta-Analysis.

OBJECTIVE: The study objective was to examine the association between phentermine/topiramate therapy and weight loss and adverse events in adults with overweight or obesity by meta-analysis and systematic review. METHODS: Medical Subject Headings and free-text terms were selected to search for eligible trials in PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and Embase up to April 18, 2020. The quality of randomized controlled trials was evaluated by the Cochrane risk-of-bias tool. Meta-analysis was performed using random-effect models. RESULTS: Phentermine/topiramate therapy resulted in an average weight loss of 7.73 kg (95% CI: 6.60-8.85) in general compared with placebo. The weight loss was related to the dose of phentermine/topiramate. Compared with placebo, the average weight loss was 3.55 kg (95% CI: 2.22-4.88) for 3.75/23 mg, 7.27 kg (95% CI: 6.40-8.13) for 7.5/46 mg, and 8.25 kg (95% CI: 6.92-9.79) for 15/92 mg. For phentermine/topiramate participants in different weight-loss subgroups, the weight loss of participants with ≥5%, ≥10%, and ≥15% baseline weight loss was 3.18 (95% CI: 2.75-3.67), 5.32 (95% CI: 4.53-6.25), and 5.65 (95% CI: 3.55-9.01), respectively. Compared with placebo, the adverse events associated with the treatment mainly included dysgeusia (odds ratio [OR] = 8.86, 95% CI: 5.65-13.89), paresthesia (OR = 8.51, 95% CI: 6.20-11.67), dry mouth (OR = 6.71, 95% CI: 5.03-8.94), disturbance in attention (OR = 4.48, 95% CI: 2.39-8.41), irritability (OR = 4.10, 95% CI: 2.29-7.33), hypoesthesia (OR = 3.81, 95% CI: 1.32-11.00), constipation (OR = 2.43, 95% CI: 2.02-2.93), and dizziness (OR = 2.26, 95% CI: 1.72-2.98). Phentermine/topiramate also reduced waist circumference, blood pressure, blood sugar levels, and lipid levels. CONCLUSIONS: Phentermine/topiramate has considerable benefit in reducing body weight, and the efficacy was closely related to the dosage. However, it increased the risk of nervous system-related adverse events.

An improved cryosection method for polyethylene glycol hydrogels used in tissue engineering.

The high water content of hydrogels allows these materials to closely mimic the native biological extracellular conditions, but it also makes difficult the histological preparation of hydrogel-based bioengineered tissue. Paraffin-embedding techniques require dehydration of hydrogels, resulting in substantial collapse and deformation, whereas cryosectioning is hampered by the formation of ice crystals within the hydrogel material. Here, we sought to develop a method to obtain good-quality cryosections for the microscopic evaluation of hydrogel-based tissue-engineered constructs, using polyethylene glycol (PEG) as a test hydrogel. Conventional sucrose solutions, which dehydrate cells while leaving extracellular water in place, produce a hydrogel block that is brittle and difficult to section. We therefore replaced sucrose with multiple protein-based and nonprotein-based solutions as cryoprotectants. Our analysis demonstrated that overnight incubation in bovine serum albumin (BSA), fetal bovine serum (FBS), polyvinyl alcohol (PVA), optimum cutting temperature (OCT) compound, and Fisher HistoPrep frozen tissue-embedding media work well to improve the cryosectioning of hydrogels. The protein-based solutions give background staining with routine hematoxylin and eosin, but the use of nonprotein-based solutions PVA and OCT reduces this background by 50%. These methods preserve the tissue architecture and cellular details with both in vitro PEG constructs and in constructs that have been implanted in vivo. This simple hydrogel cryosectioning technique improves the methodology for creation of good-quality histological sections from hydrogels in multiple applications.