Presence Of Uric Acid Research Articles

A Novel Co-MoS2/RGO-Based Highly sensitive Sensor for Simultaneous Detection of Ascorbic Acid and Uric Acid

Abstract This study presents the synthesis of cobalt-doped MoS₂/reduced graphene oxide (Co-MoS₂/RGO) nanocomposites via a microwave-assisted technique. These nanocomposites were meticulously characterized, revealing intricate details of their nanostructure and surface morphology. Electrochemical analyses demonstrated distinct sensing mechanisms for the electrochemical oxidation of ascorbic acid (AA) and uric acid (UA) at the Co-MoS₂/RGO interface. The sensor exhibited a diffusion-controlled behavior, achieving remarkable detection limits of 0.013 µM for AA, 0.06 µM for UA, 0.248 µM for AA in the presence of UA, and 0.36 µM for UA in the presence of AA. Additionally, the Co-MoS₂/RGO composite demonstrated impressive individual and selective sensitivities for AA, measuring 8.42 µA µM⁻¹ cm⁻² and 2.786 µA µM⁻¹ cm⁻², respectively, and for UA, measuring 10.628 µA µM⁻¹ cm⁻² and 7.25 µA µM⁻¹ cm⁻², respectively. These results highlight the exceptional capability of the Co-MoS₂/RGO nanocomposite to distinguish and accurately quantify concentrations of AA and UA, both individually and simultaneously. Furthermore, the Co-MoS₂/RGO sensor demonstrated outstanding repeatability and reproducibility, consistently delivering high performance even after 15 days. These findings underscore the potential of the Co-MoS₂/RGO-based electrochemical sensor as an ultra-sensitive, highly selective, and dependable tool for real-time sample analysis in practical applications.

Electrochemical Determination of Cysteine Using a 2-(2,5-Dihydroxy-Phenyl)-Naphtho[1,2-d] Oxazole-5-Sulfonic Acid (DHPNOS) and Cerium Oxide Nanoparticle (CeO2NP) Composite Carbon Paste Electrode (CPE)

An electrochemical sensor for the electrocatalytic oxidation of cysteine was designed based upon a 2-(2,5-dihydroxy-phenyl)-naphtho[1,2-d] oxazole-5-sulfonic acid (DHPNOS) and cerium oxide nanoparticle (CN) modified carbon paste electrode (CPE). An investigation of the redox properties of this modified electrode indicates a reduction in oxidative overvoltage and an intense increase in the analytical current. The pH, modifier, and nanoparticles were optimized to 7, 4% weight percent, and 5% weight percent, respectively. The apparent charge transfer rate constant (ks) and transfer coefficient for electron transfer between modifier and electrode were 2.776 s−1 and 0.47, respectively. Using differential pulse voltammetry, a linear range from 1 to40 µM with a detection limit of 0.33 µM was observed in phosphate buffer (pH 7.0). This work introduces a simple approach for selective determination of L-cysteine in the presence of uric acid. Also, based on chronoamperometry, the diffusion coefficient was determined to be 2.61 × 10−5 cm2 s−1. The effect of interferences on L-cysteine peak current were studied. The repeatability and reproducibility of the designed sensor were also measured with relative standard deviation values of 1.00% and 4.45%, respectively. The constructed sensor was employed for the determination of L-cysteine in acetylcysteine tablets.

A novel enzymeless electrochemical sensor based on Ni(OH)2–NiO(OH) nanoelectrocatalyst for sensitive and selective detection of uric acid in PBS simulated body fluid

Neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, and Huntington's disease are increasing worldwide. Therefore, the development of a low-cost, highly stable, and portable device for rapid and accurate risk assessment of relevant biomarkers, especially uric acid (UA), by electrochemical detection is currently attracting much attention. Herein, an electrochemical enzymeless UA sensor based on highly active Ni(OH)2–NiO(OH) nanoelectrocatalyst decorated on polyaniline–carbon nanotubes (PANI-CNTs) nanocomposite film, which was modified on a commercial screen-printed carbon electrode (SPCE) by electrodeposition method for sensitive and selective detection of UA. The sensing behavior of the modified electrode (named Ni(OH)2–NiO(OH)/PANI-CNTs/SPCE) is examined in a simulated body fluid (phosphate buffer solution-PBS, 0.01 M, pH 7.4) using differential pulse voltammetry (DPV) technique. The obtained results showed that the Ni(OH)2–NiO(OH)/PANI-CNTs/SPCE electrode exhibited outstanding electrocatalytic performance for the detection of UA at low potential (0.33 V vs. Ag/AgCl) without exhibiting interfering signals of dopamine (DA), glucose (Glu), ascorbic acid (AA) and urea. The sensor exhibited extra high sensitivity (386.8 μA mM−1 cm−2), high selectivity, good reproducibility, and durable stability with the ability to detect UA at both low (5–100 μM) and high (100–800 μM) levels with a very low detection limit down to 0.11 μM (individual detection of UA) and 0.29 μM (detection of UA in presence of DA) in a simulated body fluid. The recovery test using the proposed electrochemical sensor showed a high recovery percentage (>99.81 %), making it a viable option for practical applications.

Development of an efficient electrochemical sensor based on CuAl-LDH using an electrostatic repulsion approach for the selective determination of dopamine in the presence of uric acid and ascorbic acid species

This study provides a unique electrochemical sensor that exhibits both excellent sensitivity and selectivity, while also being environmentally friendly. The CuAl-LDH/GCE sensor, proposed as the recommended sensor, was synthesized using a straightforward one-step co-precipitation procedure. It was first used to measure dopamine levels using differential pulse voltammetry. At the ideal pH level of 8, dopamine has a positive charge, but ascorbic acid and uric acid have a negative charge. LDH, on the other hand, carries a negative charge and exhibits high electrostatic attraction towards dopamine, but is electrostatically repelled by negatively charged ascorbic acid and uric acid. Hence, CuAl-LDH/GCE has the potential to specifically ascertain the existence of dopamine in the presence of these particular species. The examination of the composition and morphology of CuAl-LDH was conducted using various analytical techniques, including scanner electron microscopy (FESEM), transmission electron microscope (TEM), element mapping (MAP), Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX), Brunauer Emmett Teller (BET), X-ray photoelectron diffraction (XRD), and Raman techniques. Under ideal circumstances, the calibration graph of dopamine was generated using differential pulse voltammetry. A linear range of 4.194–1151.54 μM was achieved for dopamine, with a limit of detection of 0.33 μM. The findings of the study indicate that the sensor created for dopamine determination has exceptional stability, repeatability, and reproducibility. The sensor that was presented was effectively used for the measurement of dopamine in both pharmaceutical ampoules and human plasma samples.

Electrochemical Detection of the Antidiabetic Medication Metformin in Human Urine and Pharmaceutical Tablets Using Boron-Doped Diamond Electrode

Electrochemical Detection of the Antidiabetic Medication Metformin in Human Urine and Pharmaceutical Tablets Using Boron-Doped Diamond Electrode

Electrochemical determination of uric acid in presence of folic acid using synthesized cobalt oxide modified carbon paste electrode

Here, the synthesis of CoO nanoparticle by using co-precipitation method and characterized by XRD, SEM and EDAX techniques. The CoO nanoparticle used as modified carbon paste electrode for sensing the UA in presence of FA. The CoO/MCPE shows the excellence sensitivity towards the determination of both UA and FA. The kinetic electron transfer study of UA and FA shows with good linearity and both electrodes showed adsorption electrode process. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 3.32 µM and 11.1 µM for FA and 6.09 µM and 20.3 µM for UA, respectively. The CoO/MCPE applied for the simultaneous electrochemical determination of UA and FA, the proposed method was used for real sample analysis.

Porous gold-layered cubic and octahedral Cu-oxide nanocrystals: Dopamine sensing

Two morphologically different porous gold layered on Cu-oxide-based electrochemical sensors were developed for the selective detection of dopamine in the presence of uric acid, ascorbic acid or dextrose. The nanoparticles were prepared by layering Au onto either a cubic or octahedron-shaped Cu-oxide crystal via a galvanic reaction. These were characterized with scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. The porous structure of the gold over layer was clearly visible on the scanning electron microscopy image while the macro morphology was maintained. X-ray photoelectron spectroscopy confirmed the presence of metallic gold while both CuI (CuO) and CuII (Cu2O) were present in the samples. These two Au/Cu-oxide nanocomposites were used to modify glassy carbon electrodes and were tested for their dopamine sensing ability. Differential pulse voltammetry was used to investigate the selectivity towards dopamine in the presence of different interfering molecules uric acid, ascorbic acid and dextrose). From the differential pulse voltammetry, the lowest limit of detection was found to be 1.1 μM, with a sensitivity of 3.4 μA mM−1 mm−2 in the linear range of 10–250 μM for the porous gold layered covering the octahedron Cu-oxide-modified glassy carbon electrode.

Electrochemical Detection of Dopamine at a Novel Poly(2,4,6‐trihydroxybenzaldehyde) Film Modified Electrode

AbstractIn this study, a novel electrodeposition of poly(2,4,6‐trihydroxybenzaldehyde) on bare glassy carbon electrode for dopamine detection was reported. 2,4,6‐trihydroxybenzaldehyde and the electrodeposited poly(2,4,6‐trihydroxybenzaldehyde) were characterized using Fourier transform‐infrared spectroscopy, UV‐visible spectroscopy, and scanning electron microscopy. The bare electrode modified with the optimum amount of 2,4,6‐trihydroxybenzaldehyde (PTGCE) was used for dopamine electroanalysis. The linear dynamic range and the limit of detection of DA at PTGCE were 0.70‐19.48 μM and 19.48–53.30 μM, and 0.64 μM, respectively. The modified electrode showed outstanding discriminatory dopamine detection in the presence of uric acid and ascorbic acid due to a dopamine‐uric acid and a dopamine‐ascorbic acid peak‐to‐peak separation of 160 mV and 200 mV, respectively. The proposed sensor showed considerable reproducibility of dopamine current response and excellent % dopamine recovery of 99.70 % from the real sample solution.

Straightforward method for the electrochemical identification of dopamine in the presence of uric acid and ascorbic acid

A few-layer graphene/Pt (FGP) electrode and a novel electrochemical technique were used in determining dopamine and simultaneously detecting uric acid (UA), ascorbic acid (AA), and dopamine (DA) in a buffered phosphate-saline solution at pH 7.4. The FGP electrode effectively separated the oxidation peaks of UA, DA, and AA in the positive scan. Interestingly, during the negative scan, the FGP electrode selectively responded to DA while showing negligible response to UA and AA, thus allowing the accurate quantification of small amounts of DA in the presence of considerable UA and AA interferences. The sensors for AA, DA, and UA exhibited successful detection in the positive scan. The linear ranges were 10–1800 (AA), 1–300 (DA), and 5–800 (UA) µM, the sensitivity was 109.27 (AA), 754.19 (DA), and 493.03 (UA) µA cm–2 mM–1, and the detection limits were 4.2 µM (AA), 0.42 µM (DA), and 2.2 µM (UA). Furthermore, DA quantification was achieved in the negative scan, demonstrating a linear range of 1–100 µM, sensitivity of 2235.7 µA cm–2 mM–1, and detection limit of 0.14 µM. This study presents a novel and efficient electrochemical technique for the rapid and straightforward detection of dopamine.

Electrochemical Detection of Dopamine in the Presence of Uric Acid at Cerium Oxide and L-Tyrosine Mixture Modified Carbon Paste Electrode: A Cyclic Voltammetry Study

In the present work, we are prepared a simple is sensitive and selective for Cerium oxide L-Tyrosine modified carbon paste electrode (CeO2 - L-TMCPE) for the simultaneous examination of Dopamine (DA) and Uric Acid (UA), by using cyclic voltammetry (CV). Carbon paste electrode was fabricated with Cerium oxide L-Tyrosine mixture as modifier for the detection of DA in the presence of UA in 0.2 M Phosphate buffer solution of pH 7.0. The CeO2 - L-TMCPE MCPE display an increase in the peak (Ip) current as related to that of BCPE. The CeO2 - L-TCPE mixture MCPE showed outstanding electro catalytic action for selective determination of DA in the presence of UA. Surface morphology of CeO2NPs was studied using XRD, SEM and EDAX, some electrochemical constraints alike effect of pH, effect of Scan rate, varied concentrations DA & UA were considered at CeO2 - L-TMCPE MCPE. The modified CeO2 - L-TCPE behaves similar selective electrochemical sensor for finding of DA and UA.

4,5-Diamino-2-Thiouracil-Powered Dual-Mode Biosensor for Sensitive, Nonenzymatic Determination of Saliva Uric Acid Levels.

Nonenzymatic and rapid monitoring of uric acid levels is of great value for early diagnosis, prevention, and management of oxidative stress-associated diseases. However, fast, convenient, and low-cost uric acid detection remains challenging, especially in resource-limited settings. In this study, a novel and rapid biosensing approach was developed for the simultaneous visualization and quantification of uric acid levels by using the unique surface plasmon resonance and photothermal property of 4,5-diamino-2-thiouracil (DT)-capped gold nanoparticles (AuNPs). With the presence of uric acid, DT-capped AuNPs rapidly aggregated, and a visible color/photothermal change was used for uric acid quantification within 15 min. The limit of detection was determined to be 11.3 and 6.6 μM for the dual-mode biosensor, leveraging the unique structure of DT to optimize reaction kinetics. Moreover, the sensor exhibited excellent anti-interference capabilities and demonstrated potential for detecting a wide range of uric acid concentrations in complex samples, thereby reducing the need for extensive sample dilution and complex material synthesis procedures. Furthermore, validation against gold standard testing indicates that this biosensor could serve as a highly sensitive assay for quantifying uric acid levels in point-of-care applications, particularly in resource-limited settings.

Development of Glutamate Sensor Based on Mxene/NiO Modified Screen Printed Carbon Electrode

Glutamate plays a vital role as a neurotransmitter, contributing significantly to both physiological and pathological processes. Although enzymatic electrochemical sensors exhibit the ability to selectively detect glutamate, the presence of enzymes introduce sensor instability. Consequently, there is a pressing need for the advancement of enzyme-free glutamate sensors [1-3]. In this study, we have developed an incredibly sensitive non-enzymatic electrochemical sensor for detecting glutamate.This was achieved by synthesizing nanoparticles of nickel oxide (NiO) and physically combining them with MXene on a Screen-printed carbon electrode (SPCE)[2]. Fig. 1 shows the MXene-NiO nanoparticles (NPs) modification process on SPCE. In this work, cyclic voltammetry and amperometric techniques were carried out in a three-electrode system with an oxygen-saturated environment, where MXene-NiO/SPCE, pt wire, and Ag/AgCl electrode were used as working, counter, and reference electrode respectively. MXene-NiO/SPCE showed significant electro-catalytic activity in catalyzing the oxidation of glutamate in 0.1 M NaOH solution. A linear relationship was established between the current response and Glutamate concentration after the electrochemical experiments were conducted while working parameters were optimized. We conducted an extensive investigation of glutamate-sensing mechanism. The optimized sensor exhibited an irreversible oxidation process for glutamate, involving the transfer of one electron and one proton. It displayed a fast response time of < 5 s and a linear response within the concentration range of 20 to 300 µM at a pH of 7, with a LOD of 17.5 µM, sensitivity of 4500 µA.mM−1.cm−2. The morphology of the MXene-NiO composites was characterized using SEM, EDX, XRD, FT-IR, and UV spectroscopy techniques. The investigation into interference on the MXene-NiO/SPCE revealed a noteworthy current response to glutamate even in the presence of uric acid and ascorbic acid. As a result, the development of a reliable, enzyme-free glutamate sensor could be enabled by this simple sensor based on MXene-NiO composites.Fig. 1. The process of MXene/NiO/SPCE electrode.Reference[1] M. Jamal et al., Microsyst. Technol., 24, 4217–4223, 2018. doi: 10.1007/s00542-018-3724-6.[2] M. Jamal et al., Biosens. Bioelectron., 40, 213–218, 2013. doi: 10.1016/j.bios.2012.07.024.[3] K. M. Razeeb et al., Vertically Aligned Nanowire Array-Based Sensors and Their Catalytic Applications. In: Vestergaard, M., Kerman, K., Hsing, IM., Tamiya, E. (eds) Nanobiosensors and Nanobioanalyses, Springer, Tokyo, 2015. Figure 1

A facile poly(allura red) film for signal-amplified electrochemical sensing of dopamine and uric acid in human plasma and urine

A novel and facile sensing platform based on poly(allura red) film, synthesized via a one-step cyclic voltammetry scanning, was used for determining dopamine and uric acid in human plasma and urine. The signal was amplified thanks to the good π–π and electrostatic interaction of the allura red polymer film, and thus the superior electron transfer rate. The electrochemical determination of dopamine and uric acid, alone and in the presence of each other, was investigated and the oxidation peaks at 190 mV for dopamine and 320 mV for uric acid were used as the analytical response. Characterization measurements for the fabricated platform were performed with various techniques including cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The poly(allura red) film-modified electrode exhibits a remarkable limit of detection values of 10.5 nM for dopamine and 30.1 nM for uric acid with wide linear ranges of 0.03–20 µM and 25–70 µM µM for dopamine, 0.09–110 µM for uric acid, 0.48–80 µM and 90–290 µM for dopamine in the presence of uric acid, and 0.35–200 µM for uric acid in the presence of dopamine. The proposed method was applied to the human plasma and urine samples, the results were statistically compared with those obtained from the titrimetric method, and no significant difference at a 95 % confidence level was found.

CeO2 nanocubes-based electrochemical sensor for the selective and simultaneous determination of dopamine in the presence of uric acid and ascorbic acid

CeO2 nanocubes-based electrochemical sensor for the selective and simultaneous determination of dopamine in the presence of uric acid and ascorbic acid

Laser-induced graphene electrodes on polyimide membranes modified with gold nanoparticles for the simultaneous detection of dopamine and uric acid in human serum.

The level control of biological active molecules in human body fluids is important for the surveillance of several human diseases. Dopamine (DA) and uric acid (UA) are two important biomarkers of neurological and bone diseases, respectively. Design of sensitive and cost-effective sensors for their detection is an effervescent research field. We report on the straightforward design of laser-induced graphene electrodes (LIGEs) from the laser ablation of a polyimide substrate and their modification by electrochemical deposition of gold nanoparticles (AuNPs/LIGE) and their uses as chemosensors. Electrochemical investigations showed that the presence of gold nanoclusters onto the electrode surface improved the electrochemical surface area (ECSA) and the heterogenous electron transfer (HET) rate. Furthermore, the AuNPs/LIGEs can be used to detect simultaneously low concentrations of DA and UA in presence of ascorbic acid (AA)as an potentiallyinterfering substance at redox potentials of 300 mV, 230 mV and 450 mV and 91 mV, respectively, compared with the Ag/AgCl (3 M KCl) reference electrode in cyclic voltametric. The method displayed linear ranges varying from 2 to 20 μM and 5 to 50 μM, led to limits of detection of 0.37 μM and 0.71 μM for DA and UA, respectively. The AuNPs/LIGE was applied to simultaneously detect both analytes in scarcely diluted human serum with good recoveries. The data show that the recovery percentages ranged from 94% ± 2.1 to 102 % ± 0.5 and from 94% ±0.3 to 112% ± 1.4 for dopamine and uric acid, respectively. Thus, the AuNPs/LIGEs are promising candidates for the detection of other biologically active molecules such as drugs, pesticides, and metabolites.

Sustainable Laser‐Induced Graphene Electrochemical Sensors from Natural Cork for Sensitive Tyrosine Detection

AbstractCork laser induced graphene (cork‐LIG) electrochemical sensors are fabricated by direct laser writing of natural cork sheets. Laser writing is performed with a hobbyist visible laser. The obtained cork‐LIG structures display graphene‐like Raman signatures, high conductivity, and fast electron‐transfer rates. After a 10 min electrochemical pretreatment, electrodes are used for detection of Tyrosine (Tyr) in the presence of uric acid, dopamine, ascorbic acid, urea, and glucose. linear detection of tyrosine is achieved in the 5–150 µm range with a limit of detection (LOD) of 3.03 µm. Calibration of dopamine detection is achieved with a LOD of 1.1 µm. Finally, the cork‐LIG electrochemical sensors show linear response of Tyr in artificial sweat in the relevant physiological range of 5–250 μm (sensitivity, 1.8×10−2 A m−1). The LOD is calculated as 3.75 μm. These results open the door to the exploitation of renewable materials such as cork for the development of high‐quality, green sensors for the monitoring of health and wellbeing parameters.

An intelligent and novel electrochemical biosensor for simultaneous enzymatic biosensing of cholesterol and glucose in the presence of uric acid based on first-and second-order calibration methods

In this work, for the first time, a novel electrochemical biosensor was fabricated based on modification of a glassy carbon electrode with multi-walled carbon nanotubes-ionic liquid (MWCNTs-IL) which was used as a platform to the synthesis of molecularly imprinted polymers having glucose (GL), glucose oxidase (GO), cholesterol (CL), cholesterol oxidase (CO), cholesterol esterase (CE), horse radish peroxidase (HRP), and uric acid (UA) as template molecules. For simultaneous biosensing of GL and CL, the biosensor (MIPs/MWCNTs-IL/GCE) was incubated with the enzymes and then, it was individually incubated with GL and CL. Response of the biosensor was based on the reduction of the hydrogen peroxide produced from enzymatic reactions. Individual incubation of the biosensor with GL and CL generated two very similar peaks while its incubation with both GL and CL generated a single peak which needed to be assisted by first- and second-order calibration methods to choose the best method. Second-order hydrodynamic differential pulse voltammetric data were generated and modeled by MCR-ALS, PARASIAS, and PARAFAC2 to simultaneous determination of them in the presence of UA as uncalibrated interference based on exploiting second-order advantage. Amperometric responses of the biosensor to GL and CL were also calibrated and assisted by first-order calibration methods for simultaneous determination of GL and CL in the presence of UA based on exploiting first-order advantage. The result confirmed that the biosensor assisted by second-order data modeled by MCR-ALS showed the best performance for simultaneous determination of CL and GL in the presence of UA as uncalibrated interference in both synthetic samples and human serum samples which was comparable with HPLC-UV as the reference method. It should be noted the biosensor was able to simultaneous determination of CL and GL in the ranges of 0.5–15 pM and 1–18 pM with limits of detection of 0.81 pM and 0.23 pM, respectively, and response of the biosensor was stable, selective, ultrasensitive, repeatable, and reproducible. This work as the first report chemometric assisted enzymatic biosensing of GL and CL can be continued to develop more projects for biomedical purposes.

Zinc oxide modified carbon paste electrode sensor for the voltammetric detection of L-tryptophan in presence of uric acid and ascorbic acid

The mechanochemical method was used for the synthesis of Zinc oxide nanoparticles (ZnONps) and was characterized by energy-dispersive spectroscopy (EDAX) scanning electron microscopy (SEM) and X-ray diffraction (XRD). Using a zinc oxide modified carbon paste electrode (ZnOMCPE) the oxidative response of L-tryptophan (LTP) was analyzed by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. CV was used to scrutinize the parameters of pH, concentration and scan rate of LTP. In this work, compared to bare carbon paste electrode (BCPE), the modified electrode shows enhanced peak current. CV exhibits a good linearity in the concentration range 10–40 μM (LTP). The limit of detection (LOD) and limit of quantification (LOQ) values of LTP were observe to be 0.57 and 1.72 μM respectively. DPV was used to study the analytical individualization and interference study of L-tryptophan (LTP), Uric acid (UA) and Ascorbic acid (AA). The above outcome shows that the polished surface of the modified electrode gives excellent sensitivity and selectivity in its voltammetric response and good LOD for LTP.

Stabilization of uric acid mixed crystals by melamine

Melamine stabilizes heterogeneous nucleation of calcium crystals by increasing the retention time and decreasing the rate of dissolution. Stabilization of such mixed crystals limits the efficacy of non-invasive treatment options for kidney stones. Crystalline forms of uric acid (UA) are also involved in urolithiasis or UA kidney stones; however, its interactions with contaminating melamine and the resulting effects on the retention of kidney stones remain unknown. Since melamine augments calcium crystal formation, it provides an avenue for us to understand the stability of UA-calcium phosphate (CaP) crystals. We show here that melamine facilitates UA + CaP crystal formation, resulting in greater aggregates. Moreover, melamine induced mixed crystal retention through a time-dependent manner in presence and/or absence of hydroxycitrate (crystal inhibitor), indicating its abridged effectiveness as conventional remedy. CaP was also shown to modify optical properties of UA + CaP mixed crystals. Differential staining of individual crystals revealed enhanced co-aggregation of UA and CaP. The dissolution rate of UA in presence of melamine was faster than its heterogeneous crystallization form with CaP, although the size was comparatively much smaller, suggesting disparity in regulation between UA and CaP crystallization. While melamine stabilized UA, CaP and mixed crystals in relatively physiological conditions (artificial urine), the retentions of those crystals were further augmented by melamine, even in presence of hydroxycitrate, thus reducing treatment efficacy.

Dual-template molecularly surface imprinted polymer on fluorescent metal-organic frameworks functionalized with carbon dots for ascorbic acid and uric acid detection

In this work, dual-template molecularly imprinted polymer surfaces imprinted on blue fluorescent Cr-based MOF (Cr-MOF) functionalized with yellow emissive carbon dots (Y-CDs) were prepared using l-ascorbic acid (AA) and uric acid (UA) as templates for simultaneous selective recognition of AA and UA. The as-prepared nanocomposite probe (Y-CDs/Cr-MOF@MIP) contains two recognition site cavities and emits a dual well-resolved fluorescence spectra when excited at 390 nm; blue emission (λem 450 nm) is due to Cr-MOF, and yellow emission (λem 560 nm) is due to Y-CDs. The yellow fluorescence emission of Y-CDs was quenched upon the addition of ascorbic acid, while Cr-MOF’s emission remained unaffected. In the same way, the blue fluorescence emission of the Cr-MOFs was quenched in the presence of uric acid, while the yellow emission remained constant. Both emissions were quenched in a sample containing both AA and UA. This can be exploited to design a dual-template biosensor to detect UA and AA simultaneously. The Y-CDs/Cr-MOF@MIP sensor displayed a dynamic linear response for AA in the range 25.0 µM – 425.0 µM with a detection limit of 1.30 µM, and for UA in the range 25.0 µM – 425.0 µM with a detection limit of 1.10 µM. The dual-target probe Y-CDs/Cr-MOF@MIP was highly selective and sensitive for the detection of UA and AA in human urine samples due to the selectivity of the two recognition sites.