Science Letters:Evaluation of a kinetic uricase method for serum uric acid assay by predicting background absorbance of uricase reaction solution with an integrated method

A patented kinetic uricase method was evaluated for serum uric acid assay. Initial absorbance of the reaction mixture before uricase action （A0） was obtained by correcting the absorbance at 293 nm measured before the addition of uricase solution, and background absorbance （Ab） was predicted by an integrated method. Uric acid concentration in reaction solution was calculated from AA, the difference between A0 and Ab, using the absorptivity preset for uric acid. This kinetic uricase method exhibited CV〈4.3% and recovery of 100%. Lipids, bilirubin, hemoglobin, ascorbic acid, reduced glutathione and xanthine 〈0.32 mmol/L in serum had no significant effects. △A linearly responded to 1.2 to 37.5 μmol/L uric acid in reaction solution containing 15 μl serum. The slope of linear response was consistent with the absorptivity preset for uric acid while the intercept was consistent with that for serum alone. Uric acid concentrations in clinic sera by different uricase methods positively correlated to each other. By Bland-Altman analysis, this kinetic uricase method accorded with that by quantifying the total change of UV absorbance on the completion of uricase reaction. These results demonstrated that this kinetic uricase method is reliable for serum uric acid assay with enhanced resistance to both xanthine and other common errors, wider range of linear response and much lower cost.

Kinetic method for enzymatic analysis by predicting background with uricase reaction as model

Objective：To investigate the reliability for kinetic assay of substance with background predicted by the integrated method using uricase reaction as model. Methods： Absorbance before uricase action （Δ0） was estimated by extrapolation with given lag time of steady-state reaction. With Km fixed at 12.5μmol/L, background absorbance （Δb） was predicted by nonlinearly fitting integrated Michaelis-Menten equation to Candida utilis uricase reaction curve. Uric acid in reaction solution was determined by the difference （ΔA） between Δ0 and Δb. Results .Ab usually showed deviation 〈3% from direct assay with residual substrate done fifth of initial substrate for analysis. ΔA showed CV 〈5% with resistance to common interferences except xanthine, and it linearly responded to uric acid with slope consistent to the absorptivity of uric acid. The lower limit was 2.0 μmol/L and upper limit reached 30 μmol/L in reaction solution with data monitored within 8 min reaction at 0. 015 U/ml uricase. Preliminary application to serum and urine gave better precision than the direct equilibrium method without the removal of proteins before analysis. Conclusion .This kinetic method with background predicted by the integrated method was reliable for enzymatic analysis, and it showed resistance to common interferences and enhanced efficiency at much lower cost.

Rapidly separating dissolving microneedles with sustained-release colchicine and stabilized uricase for simplified long-term gout management

Despite growing prevalence and incidence,the management of gout remains suboptimal.The intermittent nature of the gout makes the long-term urate-lowering therapy(ULT)particularly important for gout management.However,patients are reluctant to take medication day after day to manage incurable occasional gout flares,and suffer from possible long-term toxicity.Therefore,a safe and easy-tooperate drug delivery system with simple preparation for the long-term management of gout is very necessary.Here,a chitosan-containing sustained-release microneedle system co-loaded with colchicine and uricase liposomes were fabricated to achieve this goal.This microneedle system was confirmed to successfully deliver the drug to the skin and maintain a one-week drug retention.Furthermore,its powerful therapeutic potency to manage gout was investigated in both acute gouty and chronic gouty models.Besides,the drug co-delivery system could help avoid long-term daily oral colchicine,a drug with a narrow therapeutic index.This system also avoids mass injection of uricase by improving its stability,enhancing the clinical application value of uricase.In general,this two-drug system reduces the dosage of uricase and colchicine and improves the patient’s compliance,which has a strong clinical translation.

Preparation of New Uric Acid Sensors Based on Iodide Selective Electrode

An electrode for uric acid has been prepared by using an iodide selective electrode with the uricase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according to our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 20 min at room temperature. The H2O2 formed from the reaction of uric acid was determined from the decrease of iodide concentration that was present in the reaction cell. The potential change was linear in the 2 × 10-5 to 2 × 10-4 M uric acid concentration (3 - 34 mg uric acid/100ml blood) range. Uric acid contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, glucose and urea was observed.

Commentary:Gut microbiota reduce the risk of hyperuricemia and gout in the human body

Gout,a prevalent and painful metabolic disease often associated with obesity and aging,is caused by the deposition of urate crystals in joints,bones,or soft tissues1.Urate is an intermediate metabolite within the purine degradation pathway,predominantly derived from uric acid under physiological pH levels.Hyperuricemia occurs due to excessive uric acid production or insufficient excretion2,which is associated with various chronic diseases,including type 2 diabetes.