Evaluation of an electrochemical biosensor for uric acid measurement in human whole blood samples

A biosensing array for multiplex clinical evaluation of glucose, creatinine, and uric acid

The multiplex and simultaneous determination of blood glucose, creatinine and uric acid is essential for the early screening of chronic diseases or regular disease monitoring. Here, we report for the first time a biosensing array for the multiplex and simultaneous determination of plasma glucose, creatinine and uric acid. The sensing electrodes are fabricated on a PET surface, including three working electrodes, one reference electrode, and one counter electrode. Each specific enzyme is immobilized on its corresponding working electrode. The biosensing array can exhibit high sensitivity and selectivity for the simultaneous determination of blood glucose, creatinine and uric acid in real blood samples, and the measurement results are accurate and consistent with those from the clinical biochemistry analyzer in the hospital. It is expected that this work could provide new avenues for the fundamental study of biosensing device construction, as well as practical applications of the detection of biomarkers in chronic diseases.

Design of Smartphone-Assisted Point-of-Care Platform for Colorimetric Sensing of Uric Acid via Visible Light-Induced Oxidase-Like Activity of Covalent Organic Framework

Monitoring of uric acid (UA) levels in biological samples is of great significance for human health, while the development of a simple and effective method for the precise determination of UA content is still challenging. In the present study, a two-dimensional (2D) imine-linked crystalline pyridine-based covalent organic framework (TpBpy COF) was synthesized using 2,4,6-triformylphloroglucinol (Tp) and [2,2'-bipyridine]-5,5'-diamine (Bpy) as precursors via Schiff-base condensation reactions and was characterized with scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, and Brunauer-Emmett-Teller (BET) assays. The as-synthesized TpBpy COF exhibited excellent visible light-induced oxidase-like activity, ascribed to the generation of superoxide radicals (O₂^•-) by photo-generated electron transfer. TpBpy COF could efficiently oxidase the colorless substrate 3,3',5,5'-tetramethylbenzydine (TMB) into blue oxidized TMB (oxTMB) under visible light irradiation. Based on the color fade of the TpBpy COF + TMB system by UA, a colorimetric procedure was developed for UA determination with a detection limit of 1.7 μmol L^-1. Moreover, a smartphone-based sensing platform was also constructed for instrument-free and on-site detection of UA with a sensitive detection limit of 3.1 μmol L^-1. The developed sensing system was adopted for UA determination in human urine and serum samples with satisfactory recoveries (96.6-107.8%), suggesting the potential practical application of the TpBpy COF-based sensor for UA detection in biological samples.

Synthesis, Characterization, and Electrochemical Evaluation of Copper Sulfide Nanoparticles and Their Application for Non-Enzymatic Glucose Detection in Blood Samples

Glutathione-capped copper sulfide (Cu_xS_y) nanoparticles with two different average sizes were successfully achieved by using a simple reduction process that involves only changing the reaction temperature. Temperature-induced changes in the size of Cu_xS_y nanoparticles resulted in particles with different optical, morphological, and electrochemical properties. The dependence of electrochemical sensing properties on the sizes of Cu_xS_y nanoparticles was studied by using voltammetric and amperometric techniques. The spherical Cu_xS_y nanoparticles with the average particle size of 25 ± 0.6 nm were found to be highly conductive as compared to Cu_xS_y nanoparticles with the average particle size of 4.5 ± 0.2 nm. The spherical Cu_xS_y nanoparticles exhibited a low bandgap energy (E_g) of 1.87 eV, resulting in superior electrochemical properties and improved electron transfer during glucose detection. The sensor showed a very good electrocatalytic activity toward glucose molecules in the presence of interference species such as uric acid (UA), ascorbic acid (AA), fructose, sodium chloride, and sucrose. These species are often present in low concentrations in the blood. The sensor demonstrated an excellent dynamic linear range between 0.2 to 16 mM, detection limit of 0.2 mM, and sensitivity of 0.013 mA/mM. The applicability of the developed sensor for real field determination of glucose was demonstrated by use of spiked blood samples, which confirmed that the developed sensor had great potential for real analysis of blood glucose levels.

Diagnosis of disease relevant nucleic acid biomarkers with off-the-shelf devices

Changes in the level of nucleic acids in blood may be correlated with some clinical disorders like cancer, stroke, trauma and autoimmune diseases, and thus, nucleic acids can serve as potential biomarkers for pathological processes. The requirement of technical equipment and operator expertise in effective information readout of modern molecular diagnostic technologies significantly restricted application outside clinical laboratories. The ability to detect nucleic acid biomarkers with off-the-shelf devices, which have the advantages of portability, simplicity, low cost and short response time, is critical to provide a prompt clinical result in circumstances where the laboratory instruments are not available. This review throws light on the current strategies and challenges for nucleic acid diagnosis with commercial portable devices, indicating the future prospect of portable diagnostic devices and making a great difference in improving the healthcare and disease surveillance in resource-limited areas.

Elevated serum uric acid, hyperuricaemia and dietary patterns among adolescents in mainland China

Background Elevated serum uric acid concentrations have been associated with metabolic syndrome. However, only limited information is available on the prevalence of hyperuricaemia in adolescents. Therefore, the aim of our cross-sectional study was to study the prevalence of hyperuricaemia and dietary patterns in adolescents aged 13-16 years living in Yangzhou, China. Methods Adolescents were asked to complete a 20-item food frequency questionnaire (FFQ) and provide an overnight fasting finger-prick sample. Principal component analysis (PCA) with varimax rotation was used to derive the dietary patterns that might be associated with high uric acid concentrations. Results A total of 1070 adolescents were recruited. Of these, 53.6% (n = 574) were females, and 58.5% (n = 625) were within the normal body mass index (BMI) range. The males had a significantly higher serving size and frequency in their weekly food consumption, including meat, poultry, Chinese cereal staple foods and Western-style fast foods, than the females (all p < 0.02). The overall mean serum uric acid concentration and prevalence of hyperuricaemia were 368.6 ± 114.5 μmol/L and 37.9%, respectively. The prevalence of hyperuricaemia was 4.633 times greater among the participants who were overweight and obese than among those who were underweight. On the other hand, the prevalence of hyperuricaemia was 0.694 times lower among the participants who had normal weight than those who were underweight. Conclusions The prevalence of hyperuricaemia was relatively high in Chinese adolescents. The prevention of hyperuricaemia measures should be strengthened in adolescents to effectively control for obesity and gout, which tend to persist into adulthood.

Voltammetric Determination of Uric Acid in Clinical Serum Samples Using DMF Modified Screen Printed Carbon Electrodes

Screen printed carbon electrodes (SPCEs) provide attractive opportunity for sensitive and selective determination target analytes in clinical samples. The aim of the current work was to develop SPCEs based sensor for the determination of uric acid in clinical serum samples. The electrodes were pretreated by soaking in N,N-dimethylformamide for 5 minutes followed by drying in an oven at 100°C for 20 mins. The effect of surface pretreatment was characterized using cyclic voltammetry. The current response of uric acid detection was improved by a factor of 3.5 in differential pulse voltammetric measurement compared to unmodified electrode. Under the optimized conditions, the sensor displayed two dynamic linear ranges 5-100 μM and 100-500 μM with correlation coefficient, R2, values of 0.98782 and 0.97876, respectively. The limit of detection and limit of quantification calculated using the dynamic linear range 5-100 μM were 1.9 x 10−7 M and 6.33 x 10−7 M, respectively. The developed sensor displayed well separated and discerned peaks for UA in presence of the potential interferent (ascorbic acid and citric acid). The electrode was successfully applied for the detection of very low level of UA in clinical serum samples in a phosphate buffer solution (pH = 7). The proposed sensor showed a very high reproducibility and repeatability with the relative standard deviation of 0.9%. In conclusion, a simple and low cost sensor based on SPCEs is developed for sensitive and selective detection of uric acid in clinical samples.

Increasing enzyme-like activity by in situ anchoring of Ag3PO4 nanoparticles on keratin–inorganic hybrid nanoflowers

Herein, we propose a facile strategy of rapid assembly of Ag₃PO₄ nanoparticles within three dimensional (3D) keratin–inorganic hybrid nanoflowers (keratin-NF@Ag₃PO₄), which can be used for colorimetric detection of UA.

Antioxidant properties of citric acid interfere with the uricase-based measurement of circulating uric acid

BACKGROUND

Circulating uric acid (UA) is an important biomarker, not only in the detection and management of gout, but also in assessing the risk of related comorbidity. The impact of collection methods on clinical UA measurements has been the subject of limited study. After observing significant differences between UA concentrations of blood samples obtained by different collection tubes, we began examining the effects of exogenous tube components on measured UA concentrations. We aimed to: (1) demonstrate the variability in uricase-based UA measurements attributable to different collection methods and (2) identify factors influencing this variability.

METHODS

Blood samples from human subjects were collected using Serum Separator Tubes (SST tubes), Acid Citrate Dextrose (ACD) tubes, and Sodium Citrate (SC) tubes. Circulating UA concentrations were measured by chemistry analyzers utilizing the uricase method. Absorbance assays were run in order to determine the effects of citric acid, sodium citrate, and dextrose on measured absorbance in the presence of leuco crystal violet dye, hydrogen peroxide, and peroxidase. Statistical analyses-including Student's T tests and ANOVA-were used to compare results.

RESULTS

UA concentrations of blood samples collected in ACD tubes were significantly lower than those collected in SST tubes (P < 0.01). Samples collected in SC tubes trended towards lower UA measurements than samples collected in SST tubes, although this difference did not reach statistical significance (P = 0.06). Blood samples spiked with separate concentrations of sodium citrate (3.2 and 22.0 g/L), citric acid (8.0 g/L), and dextrose (24.5 g/L) demonstrated significantly lower UA measurements compared to controls (P < 0.01). Absorbance assays demonstrated that increasing concentrations of citric acid and sodium citrate-in the presence of leuco crystal violet, hydrogen peroxide, and peroxidase-decreased the amount of oxidized dye in the uricase method of UA measurement in a dose-dependent manner (P < 0.01). In contrast, dextrose did not significantly alter the amount of oxidized dye available.

DISCUSSION

Our results indicate that citric acid obstructs accurate uricase-based UA measurement, providing falsely low values. Citric acid, a known antioxidant, scavenges hydrogen peroxide, a key intermediate using the uricase method. By scavenging hydrogen peroxide, citric acid decreases the amount of oxidized leuco dye leading to falsely low UA measurements. Therefore, collection tubes, like ACD and SC tubes, which contain concentrations of citric acid or its conjugate base sodium citrate should not be used to measure circulating UA levels when utilizing uricase-based measurement methods.

Undiluted human whole blood uric acid detection using a graphitized mesoporous carbon modified electrode: a potential tool for clinical point-of-care uric acid diagnosis

Direct sensing of uric acid (UA) in an undiluted whole blood sample is reported here taking human whole blood as an analyte and a self-supporting electrolyte. Among various solid electrodes (Pt, Au, GCE, and GCE/Nafion) and carbon nanomaterials (carbon nanofibers, graphene oxide, graphite nanopowder, graphitized mesoporous carbon (GMC), single-walled carbon nanotubes, and multiwalled carbon nanotubes) tested, a GMC-modified glassy carbon electrode, designated as GCE/GMC, showed a remarkable response towards direct electrochemical oxidation of blood uric acid at ∼0.25 V vs. Ag/AgCl, unlike the poor and/or feeble current signals with the other unmodified and modified electrodes. It is plausible that the mesoporous nature of the GMC favours the formation of a blood-GMC bio-corona through internalization and provides straight access to blood-matrixed uric acid. Furthermore, the effects of the scan rate and interference with various biochemicals on the GCE/GMC were analysed. The electrochemical oxidation reaction is found to be diffusion controlled in nature and there is no interference from common biochemicals like ascorbic acid, glucose, tryptophan, H2O2, xanthine, hypoxanthine, cysteine, nitrate, nitrite, and sulfide in blood. Real blood UA sample analysis was demonstrated with comparable UA analysis results from the clinical measurement.

Enzyme mimicking inorganic hybrid Ni@MnO2 for colorimetric detection of uric acid in serum samples

Reliable and inexpensive detection of uric acid in the absence of any peroxide or enzyme is very challenging for the development of a new cost effective clinical method.

Polysilicon nanogap lab-on-chip facilitates multiplex analyses with single analyte

Rationally designed biosensing system supports multiplex analyses is warranted for medical diagnosis to determine the level of analyte interaction. The chemically functionalized novel multi-electrode polysilicon nanogap (PSNG) lab-on-chip is designed in this study, facilitates multiplex analyses for a single analyte. On the fabricated 69nm PSNG, biocompatibility and structural characteristics were verified for the efficient binding of Human Chorionic Gonadotropin (hCG). With the assistance of microfluidics, hCG sample was delivered via single-injection to 3-Aminopropyl(triethoxy)silane (APTES) and Glycidoxypropyl(trimethoxy)silane (GPMS) modified PSNG electrodes and the transduced signal was used to investigate the dielectric mechanisms for multiplex analyses. The results from amperometric response and impedance measurement delivered the scale of interaction between anti-hCG antibody and hCG that exhibited 6.5 times higher sensitivity for the chemical linker, APTES than GPMS. Under optimized experimental conditions, APTES and GPMS modified immunosensor has a limit of detection as 0.56mIU/ml and 2.93mIU/ml (at S/N=3), with dissociation constants (Kd) of 5.65±2.5mIU/ml and 7.28±2.6mIU/ml, respectively. These results suggest that multiplex analysis of single target could enhance the accuracy of detection and reliable for real-time comparative analyses. The designed PSNG is simple, feasible, requires low sample consumption and could be applied for any given multiplex analyses.

Colorimetric detection of uric acid in human urine and serum based on peroxidase mimetic activity of MIL-53(Fe)

The porous metal–organic framework MIL-53(Fe) was prepared using a simple solvothermal method, and was developed as a colorimetric sensor for the detection of uric acid in human urine and serum.