Interference Of Uric Acid Research Articles

Empowering Electrochemical Biosensors with AI: Overcoming Interference for Precise Dopamine Detection in Complex Samples

Two significant issues in biosensors that can't be solved by conventional analytical methods are selectivity among likely biological interfering molecules and background noise in clinical samples. The application of embedded machine learning in the removal of background interference, which is extremely common in complex matrix solutions such as cerebrospinal fluid, is still unexplored. The implementation of machine learning into devices and sensors can enhance their reliability to discriminate responses. In addition, implementing these models into portable devices can further improve the usage of point‐of‐care devices, continuous monitoring, and viral mutation assessments. Herein, the requirements to implement an embedded AI model (TinyML) into low‐power portable systems and its use in the electrochemical field are presented. The application of TinyML to discriminate between interference of uric acid and ascorbic acid, both well‐known abundant electrochemically active species, in neurotransmitter detection, is explored, reaching overall accuracy of 98.1% for 32‐bit float point unit and 96.01% after 8‐bit quantization, with the usage of 4.55% of the custom‐made potentiostat memory. The model can be improved simply by having the trade‐off between memory and accuracy. The research suggests that TinyML can be a key component in future medical devices, allowing data processing in real time and with increasing reliability.

Laser-Induced Graphene on Optical Fibre: Towards Simple and Cost-Effective Electrochemical/Optical Lab-on-Fibre Bioplatforms

A 3D graphene foam made of interconnected multilayer graphene flakes was produced on optical fibres (OF) by laser-induced transformation of a polyimide (PI) film coated on the OF cladding. This material, known as laser-induced graphene (LIG), was explored in the electrochemical detection and quantification of dopamine (DA) at physiologically relevant concentrations in the presence of the most relevant interfering molecules in biological fluids, ascorbic acid (AA) and uric acid (UA). The measured limit of detection is 100 nM, the linear range is 0.1 to 5.0 μM and a maximum sensitivity of 5.0 µA µM−1 cm−2 was obtained for LIG decorated with Pt nanoparticles (NPs). Moreover, immunity to AA and UA interference and to fouling was attained by decorating the LIG electrode with Pt NPs and coating it with Nafion. These figures of merit underline the potential of these sensors for the quantification of physiologically relevant concentrations of DA in biological fluids, paving the way for the development of hybrid electrochemical/optical sensing actuating platforms in a lab-on-fibre configuration, with relevant applications in biomedical engineering. The advantages of this hybrid arrangement include the possibility of in situ counterproofing, extended measuring ranges, photoelectrochemical detection and the probing of inaccessible places. This elegant approach can also provide a simple and cost-effective way to fabricate biomedical devices with extended functionality, such as medical optical probes with added electrochemical capabilities and optogenetics combined with local electrochemical detection, among others.

Pretreatment strategies of titanium substrates to modulate the electrochemical properties of CVD-grown Ti-doped diamond electrodes for dopamine detection

The identification of highly sensitive materials able to combine performance stability, relatively low cost, controllable and large area fabrication process is still a major bottleneck in the scientific community. Dopamine is considered a key indicator to monitor cardio and cerebrovascular diseases and its redox activeness makes electrochemical detection the most straightforward and promising sensing approach. Here we report the realization, by a simple yet effective approach, of diamond-based electrodes with a native selectivity towards dopamine. In details, three different substrate pretreatments, i.e., lapping, electropolishing and chemical etching, are adopted to tailor the morphological, structural, and sensing features of titanium doped diamond layers. SEM, AFM, Raman spectroscopy, XRD, XPS and I-V analyses demonstrate the features' modulation of the diamond layers being crucial for electrochemical and sensing performances, as confirmed by dopamine selectivity under ascorbic and uric acid interferents' excess. Furthermore, the controlled introduction of oxygen-containing groups enhances the dopamine sensitivity, lowering the detection limit from 6000 to 600 nM. In addition to giving an important insight on the physical-chemical growth processes, these preliminary results pave the way for the exploitation of these materials in a wide range of sensing applications, thanks to the non-toxicity and high surface tunability without post-synthesis treatments.

Sonochemical fabrication of a hybrid electrode material based on pristine carbon nanotubes and bentonite clay for fast and highly sensitive determination of dopamine in the presence of ascorbic and uric acid

This work focuses on the attachment of bentonite clay to external surface of individual pristine multiwalled carbon nanotubes (MWCNTs) and the use of the resulting hybrid material for the fast and highly sensitive electrochemical determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). XRD, FE-SEM and EDX highlighted the pristine state of MWCNTs and bentonite clay. HR-TEM confirmed the adsorption of clay on the external surfaces of individual pristine MWCNTs. Electrochemical characterization showed that the fabricated sensor possesses a large electrochemical surface area with excellent electron transfer properties. The influence of parameters likely to affect sensor performance was studied; 40 s, 10 μL suspension, and pH 7.4 were found to be the optimal accumulation time, optimal suspension volume, and optimal electrolyte pH, respectively. Under these optimal conditions, DPV peak currents were linearly related to DA concentrations in the range of 0.4–14 μM, and the detection limit was found to be 6 nM (S/N = 3). The Interference study revealed that the sensor eliminates AA and UA interference up to concentrations above their blood levels. Furthermore, the developed sensor exhibited good repeatability, satisfactory long-term stability, and was successfully applied to the detection and quantification of DA in human serum sample with satisfactory recoveries.

Microfluidic biochip platform sensitized by AgNPs for SERS based rapid detection of uric acid

Herein, a novel microfluidic-biochip enabled with surface enhanced Raman spectroscopy (SERS) as a readout has been demonstrated for uric acid (UA) detection as point-of care (POC) device. Three different biochip designs (D1, D2 and D3) containing pillars in a microchannel with different bending ratios were conceived and optimized for various mixing parameters using a multiphysics simulation tool. The microchannel, integrated with pillars, provide pressure perturbation, sharp corners, and variation in bending ratio improves phase shift and mixing index. Subsequently the microfluidic-biochips were fabricated by a combination of photo-and soft-lithography, and bonding strength between two Polydimethylsiloxane substrates were found stable up to a flow rate of 1.8 ml min−1. Further to realize SERS activity in the microfluidic-biochip, cubic shape silver nanoparticles (AgNPs), with an average size ∼68 nm, were synthesized using poly-ol method. The SERS activity was optimized by simultaneously flowing AgNPs and crystal violet (CV) dye of 10−6M, with double inlet in the reservoir and highest sensitivity was achieved in the D3 biochip. Further, D3 biochip was employed for detection of extended concentrations of CV and UA. The enhancement factor limit of detection and relative standard deviation was found to be 2 × 107, 8.9 × 10−11 and 2.7% respectively for CV and 3.1 × 103, 3.2 × 10−7 and 2.9% respectively for UA. Interference of UA with lactic acid has been tested and device was able to detect signature peaks of both biomarkers up to 50 × 10−9 M concentration. Thus, the developed microfluidic-biochip device has potential to be used in a POC setting for onsite detection of biomarkers.

Protein nano Dots conjugated AuNP, poly-Lysine biointerface for the selective voltammetric estimation of Melatonin in pharmaceutical and food samples

Attributed to the compromised charge transfer of Protein-derived nanomaterials, their beneficial traits as an extraordinarily selective and specific biorecognition element for the electrochemical sensors haven’t been fully exploited. Here in this work, we report a facile approach to electrochemically fabricate a Protein Nanodots (PNDs) conjugated AuNP, poly-Lysine biointerface for the voltammetric estimation of Melatonin. Using bovine serum albumin, PNDs decorated with active functional groups were derived and further tailored with AuNP-poly Lysine to achieve the facilitated charge-transfer and specific interactions with Melatonin. After detailed topographical and chemical characterization of the fabricated surface, its ability to estimate Melatonin was probed in a linear concentration range of 0.1–200 µM. The fabricated biointerface manifested a ∼3-fold magnification in Mel peak current with a potential shift of ∼60 mV compared to the unmodified electrode. The potential shift was attributed to the synergistic effect of PNDs and Au-poly-Lysine layer leading to the electro-catalytic behavior and facilitated charge-transfer due to specific interactions between Melatonin/AuNP-PLL/PND. Consequently, sensor demonstrated a LOD of 31.6 nM without any substantial interference of Uric acid, Ascorbic acid, and Hypoxanthine. The estimation of Melatonin in commercial pharmaceutical formulation as well as food sample (Mung Beans) was carried out to investigate the practical application.

Role of Silver Nanoparticle-Doped 2-Aminodiphenylamine Polymeric Material in the Detection of Dopamine (DA) with Uric Acid Interference.

A viable electrochemical approach for the detection of dopamine (DA) in uric acid (UA) utilizing a silver nanoparticle-doped 2-aminodiphenylamine (AgNPs-2ADPA) electrode was invented. The electrochemical performance of DA showed that the incorporated electrode displayed outstanding electrocatalytic performance to the electrochemical oxidation of DA. In our study, the AgNPs-2ADPA exhibits remarkable catalytic activity, retaining high current value and resilience when employed as a working electrode component for electrocatalytic detection of DA. We have also utilized the bare and polymeric-2ADPA in DA detection for a comparison study. This method offers a facile route with extraordinary sensitivity, selectivity, and strength for the voltammetric detection of DA, even in the presence of UA and ascorbic acid (AA) as interferents, that can be employed for pharmaceutical and biological specimens.

Highly sensitive and selective non-enzymatic measurement of glucose using arraying of two separate sweat sensors at physiological pH

A big challenge of non-enzymatic sensors is their lack of enough selectivity towards the analytes such as glucose, which must be addressed. In this study, a new system of arraying two different electrochemical sensors is designed to achieve glucose-selective and -sensitive non-enzymatic sweat-based sensors. Two kinds of sensors have been fabricated using (i) the controlled electrodeposition of cobalt/copper as the glucose-sensing electrode and (ii) the functionalized MWCNT/Fe3O4 electrode to eliminate the interference of other existing chemicals in the sweat. The controlled electrodeposition of Co/Cu led to the nanowire-shaped growth of cobalt and nanoparticle formation of copper on the carbon working electrode, confirmed by the SEM. Also, the functionalization of MWCNT with long-chain amine groups and Fe3O4 electrocatalysts has been monitored. Chronoamperometry test results of Co/Cu sensor showed a linear behavior in response to the glucose with a high sensitivity of 1909.86 µA.mM−1.cm−2 and less than 5% error for the chemicals interferences in the sweat with an exception for the uric acid. The second sensor for minimizing the uric acid interference has been fabricated based on F-MWCNT/Fe3O4, which showed a high sensitivity of 629.75 µA.mM−1.cm−2 towards the uric acid and no sensitivity response to the glucose. The arrayed sensors minimized the error imposed by the uric acid interference and the need for an alkaline medium for measuring the glucose in real sweat samples. The analyzed data of real sweat samples at physiological pH by Clarke's error grid method showed a “zone A” deviation (clinical accuracy zone), comparable with the blood glucose levels measured by the commercial glucometers.

L-Cysteine self-assembled Au(1 1 1)-like nanoparticles modified indium tin oxide electrode for determination of dopamine in the present of uric acid

A novel L-Cysteine self-assembled gold nanoparticles modified indium tin oxide electrode (ITO/Au/L-Cys) was fabricated by facile steps of electro-deposition and immersion in solution. The as-prepared ITO/Au/L-Cys electrode is investigated as a potential electrochemical sensor for dopamine (DA) in the interference of Uric Acid (UA). It combines the catalytic advantages of the Au(111)-like nanoparticles array with self-assembled L-Cysteine. The biosensor displays a highly sensitive and selective behavior for DA in the present of UA. The peak currents response to DA is linear with their concentrations in the range of 2 μM ∼ 400 μM. In addition, a limit of detection reaches up to 0.6 μM (S/N = 3). Consequently, the high sensitivity, stability and excellent biocompatibility of ITO/Au/L-Cys electrode made it as a promising DA sensor.

Highly Sensitive and Selective Non-Enzymatic Measurement of Glucose Using Arraying of Two Sweat Sensors Modified By Controlled Growth of Co/Cu and Functionalized Carbon Nanotubes

Due to a relation between glucose in sweat and blood, there is an opportunity to monitor patients' glucose levels non-invasively through sweat. There is a high demand for developing highly selective and sensitive biosensors in order to sense biomarkers like glucose and, therefore, the diseases based on those biomarkers. However, enzymatic sensors are selective to specific biomarkers; they are suffering from high sensitivity to the fluctuation of temperature, oxygen, pH, humidity, detergents, organic reagents, and toxic chemicals, affecting their stability and sensitivity, and reproducibility. Therefore, developing non-enzymatic glucose (or other biomarkers) sensors is getting significant attention to fulfill higher sensitivity and selectivity as well as minimized susceptibility to fouling by enzyme-ageing and adsorbed intermediates. Here we have proposed a combination of two sensors that can help us improve these non-enzymatic sensors' selectivity. Two electrochemical arrayed sensors have been developed. The first electrochemical sensor has been achieved by controlled growth of cobalt nanowire and copper nanoparticles on carbon substrate in order to measure the glucose level at low concentrations, and the second electrochemical sensor has been modified by MWCNT-CO-NH-cyanuric-NH2 and Fe3O4 in order to measure the uric acid and eliminate the interference of it in glucose measurement results. In order to show the morphology of the glucose sensor, the SEM and EDX have been conducted. Also, the FT-IR test has been shown to confirm the functionalization of MWCNT. The electrocatalytic and electrochemical performance of each sensor have been evaluated in the presence of the various contaminants of sweat. The glucose sensor showed less than 5% interference toward ascorbic acid, sodium bicarbonate, and the lactic acid at their max range of presence in the sweat. For eliminating the interference of uric acid, the second sensor has developed, which has no response to the glucose and high sensitivity to the uric acid. The calibration curve of each sensor has been provided in the 3D form, and a simple method of arraying has been applied to improve the sensors' selectivity. The arrayed sensors showed a highly glucose-selective sweat-based sensor with minimized error imposed by the uric acid interference. The glucose sensor's reproducibility and durability have also been tested, which showed less than 5% and 10% variations, respectively. In the end, the arrayed sensor's performance has been evaluated by real sweat samples of a male and a female, analyzed by Clarke’s error grid analysis showing less than 20% deviation from the glucose levels measured by the commercial glucometers.

Arraying of Two Modified Sensors By Controlled Growth of Co-Cu and Functionalized Carbon Nanotube for Highly Sensitive and Selective Non-Enzymatic Sensing of Glucose in Sweat

Due to a relation between glucose in sweat and blood, there is an opportunity to monitor the glucose level of patients non-invasively through sweat. There is a high demand for developing highly selective and sensitive biosensors in order to sense biomarkers like glucose and therefore the diseases based on those biomarkers. However enzymatic sensors are selective to specific biomarkers, they are suffering from high sensitivity to the fluctuation of temperature, oxygen, pH, humidity, detergents, organic reagents and toxic chemicals which subsequently affect their stability, sensitivity, and reproducibility. Therefore, developing non-enzymatic sensors have gotten more attention recently due to their stability against those parameters. But these non-enzymatic sensors are almost non-selective toward just one contaminant. Here we proposed a combination of two sensors that can help us to improve the selectivity of these non-enzymatic sensors. Two electrochemical arrayed sensor has been developed. The first electrochemical sensor has been achieved by controlled growth of cobalt nanowire and copper nanoparticles on carbon substrate in order to measure the glucose level at low concentrations and the second electrochemical sensor has been modified by MWCNT- CO-NH-cyanuric-NH2 in order to measure the uric acid and eliminate the interference of it in glucose measurement results. In order to show the morphology of the glucose sensor, the SEM and EDX have been conducted. Also, the FT-IR test has been shown to confirm the functionalization of MWCNT. The electrocatalytic and electrochemical performance of each sensor has been evaluated in the presence of the various contaminants of sweat. The glucose sensor showed the limit of detection (LOD) of 25 μM of glucose and less than 15% interference by ascorbic acid, sodium bicarbonate, lactic acid at the max range of contaminants in the sweat. For eliminating the interference of uric acid, the second sensor has developed which has no response to the glucose and high sensitivity to the uric acid. The calibration curve of each sensor has been provided and a simple method of arraying has been applied to improve the selectivity of the sensors. At the end, the sweat of a male and a female have been collected continuously over 8hours to compare the glucose level of sweat monitored by the sensors and the blood monitored with the commercial glucometer in the same period of time.

Highly sensitive and selective dopamine biosensor using Au nanoparticles-ZnO nanocone arrays/graphene foam electrode.

Based on the Au nanoparticles-ZnO nanocone arrays/graphene foam electrode, a novel dopamine biosensor was successfully developed. Graphene foam was synthesized by chemical vapor deposition, ZnO nanocone arrays were grown on its surface by a hydrothermal method and Au nanoparticles with carboxyl groups were self-assembled onto the ZnO nanocone arrays to obtain Au nanoparticles-ZnO nanocone arrays/graphene foam electrode. The result indicates that the prepared electrode has a high sensitivity (4.36μAμM-1) and low limit of detection (0.04μM, S/N=3) for the detection of dopamine. The prepared electrode also exhibits an excellent selectivity under the interference of uric acid, good repeatability and stability. The prepared sensor has been successfully applied in real samples and has a great potential to be used in the field of medical and health.

Modulating Electrode Kinetics for Discrimination of Dopamine by a PEDOT:COOH Interface Doped with Negatively Charged Tricarboxylate.

The rapidly developing field of conducting polymers in organic electronics has many implications for bioelectronics. For biosensing applications, tailoring the functionalities of the conducting polymer's surface is an efficient approach to improve both sensitivity and selectivity. Here, we demonstrated a facile and economic approach for the fabrication of a high-density, negatively charged carboxylic-acid-group-functionalized PEDOT (PEDOT:COOH) using an inexpensive ternary carboxylic acid, citrate, as a dopant. The polymerization efficiency was significantly improved by the addition of LiClO4 as a supporting electrolyte yielding a dense PEDOT:COOH sensing interface. The resulting PEDOT:COOH interface had a high surface density of carboxylic acid groups of 0.129 μmol/cm2 as quantified by the toluidine blue O (TBO) staining technique. The dopamine response measured with the PEDOT:COOH sensing interface was characterized by cyclic voltammetry with a significantly reduced ΔEp of 90 mV and a 3-fold increase in the Ipa value compared with those of the nonfunctionalized PEDOT sensing interface. Moreover, the cyclic voltammetry and electrochemical impedance spectroscopy results demonstrated the increased electrode kinetics and highly selective discrimination of dopamine (DA) in the presence of the interferents ascorbic acid (AA) and uric acid (UA), which resulted from the introduction of negatively charged carboxylic acid groups. The negatively charged carboxylic acid groups could favor the transfer, preconcentration, and permeation of positively charged DA to deliver improved sensing performance while repelling the negatively charged AA and UA interferents. The PEDOT:COOH interface facilitated measurement of dopamine over the range of 1-85 μM, with a sensitivity of 0.228 μA μM-1, which is 4.1 times higher than that of a nonfunctionalized PEDOT electrode (0.055 μA μM-1). Our results demonstrate the feasibility of a simple and economic fabrication of a high-density PEDOT:COOH interface for chemical sensing, which also has the potential for coupling with other biorecognition molecules via carboxylic acid moieties for the development of a range of advanced PEDOT-based biosensors.

Nitrite Detection in Near-Neutral-pH Electrolytes by Differential Pulse Voltammetry Under Cross Interference of Uric Acid, Ascorbic Acid, and Paracetamol

This article proposes nitrite detection in near-neutral-pH electrolytes by differential pulse voltammetry under cross-interference of uric acid (UA), ascorbic acid (AA), and paracetamol (PA) using 1,2-cis/trans diaminobenzene-modified gold measuring electrodes and a 0.9% NaCl solution as a neutral-pH blank. The peak at (0.247 ± 0.005) VAg/AgCl/nafion117 was attributed to the oxidation reaction from NO2− to NO3−, and another at (0.506 ± 0.005) VAg/AgCl/nafion117 was shown to be due to the oxidation reaction from HNO2 to NO3− based on the Nernst formalism to calculate its relative position. It was noteworthy that the peak located at (0.247 ± 0.005) VAg/AgCl/nafion117 allowed the nitrite quantification for concentrations higher than 1 mmol L−1 under cross interference of UA, AA, and PA at their upper limits reported for human urine.

A novel non-enzymatic dopamine sensors based on NiO-reduced graphene oxide hybrid nanosheets

Ni(OH)2 nanoflakes (NFs) and graphene oxide (GO) nanosheets were prepared by a hydrothermal process and the modified Hummer’s method, respectively. Then, Ni(OH)2 NFs were dispersed in the GO suspension with the assistance of ultrasonic. Finally, the mixed colloidal solution was uniformly sprayed onto the surface of indium tin oxide (ITO) glass and annealed to obtain the NiO-reduced GO (RGO)/ITO electrode, which subsequently used for electrochemical sensing of dopamine (DA) analyte. The NiO-RGO/ITO electrode exhibits enhanced electrochemical response in the aqueous solution of DA analyte, which shows a high sensitivity (1.04 µA µM− 1), the lower measured detection limit (1 µM). The NiO-RGO/ITO electrode also exhibits an excellent selectivity under the interference of uric acid, repeatability and stability. The prepared sensor has been successfully applied in real samples and has a great potential to be used in clinical medicine.

Electrochemical determination of levodopa in the presence of uric acid using ZnO nanoflowers-reduced graphene oxide

ZnO nanoflowers (ZnO NFs) were prepared by hydrothermal synthesis and graphene oxide nanosheets (GO NSs) were synthesized by the Hummer’s method. Then, ZnO NFs were dispersed in GO dispersion and sprayed onto ITO-coated glass. Finally, the ZnO NFs-GO NSs/ITO was annealed to form the ZnO NFs-rGO NSs/ITO, acting as the electrode for the determination of levodopa (LD) under the interference of uric acid (UA). The results reveal that the ZnO NFs are made up of nanorods with the diameter of ∼ 150 nm and the length of ∼ 2 µm and ZnO NFs are covered by rGO NSs. The ZnO NFs-rGO NSs/ITO electrode exhibits an enhanced electrochemical response due to its excellent redox activity, which shows a high sensitivity (0.66 µA µM−1), low measured detection limit (1 µM) and excellent selectivity for determination of LD. The electrode was used to detect the LD in the actual sample of human serum for practical application, revealing satisfactory results.

Determination of Colchicine in Pharmaceutical Formulations and Urine by Multiple-Pulse Amperometric Detection in an FIA System Using Boron-Doped Diamond Electrode

This work presents a simple and fast method for colchicine (CO) determination in pharmaceutical formulations and urine by multiple pulse amperometry (MPA) with flow injection analysis (FIA) system using a boron-doped diamond electrode. In optimized conditions, it was possible to quantify CO in urine samples without interference of uric acid and ascorbic acid. The working linear range for CO quantification was achieved from 1.0 × 10-7 to 0.5 × 10-3mol L-1 with a low limit of detection of 2.14 × 10-8mol L-1. Furthermore, the proposed method showed high repeatability for 10 consecutive injections of 1.0 × 10-4mol L-1 CO (relative standard deviation = 1.28%) and good analytical frequency (30 determinations per hour). The addition and recovery studies in all pharmaceutical samples were approximately 100% and the results for CO determination were compared by high performance liquid chromatography (HPLC) with UV detection.

Generation-Collection Electrochemistry Inside a Rotating Droplet.

In this work, we explore generation-collection electrochemistry in a rotating droplet hydrodynamic system, where a 70 μL droplet containing a redox active species (ferrocyanide) is sandwiched between an upper rotating rod and bottom nonmoving generator and collector planar electrodes. In such a system, we studied the effect of the counter electrode reaction on the recorded generator current, and the effect of the generator-collector distance (ranging from 3 to ca. 500 μm) on the collection efficiencies obtained at rotation rates ranging from 50 to 1100 rpm. We found that the counter electrode reaction competes with the collector reaction for the regeneration of the electroactive species; thus, collection efficiencies of 100% are probably impossible to obtain with this system geometry. We found that the collection efficiency increases with the droplet rotation rate and decreases with the generator-collector distance. The highest collection efficiency we obtained is 62% for the generator-collector distance of 3 μm, which is more than two times higher than that for typical bulk experiments with a commercial rotating ring disk electrode. We show that the increased collection efficiency can be successfully used in epinephrine detection for filtering out signals from ascorbic acid and uric acid interferents.

Sensitive electrochemical sensor for simultaneous determination of uric acid and xanthine in human biological fluids based on the nano-boron doped ceria modified glassy carbon paste electrode

A sensitive and selective electrochemical method was developed for simultaneous determination of uric acid and xanthine using the nano boron doped ceria modified glassy carbon paste electrode (nano-B-CeO2/GCPE). The proposed sensor exhibited an excellent catalytic activity, high sensitivity and good selectivity toward the oxidation of uric acid and xanthine. The potential mutual interference of uric acid (UA), xanthine (XA), dopamine (DA) and ascorbic acid (AA) were examined indicting that their oxidation take place independently at the nano-B-CeO2/GCPE sensor. For simultaneous detection by synchronous change of the concentration of UA and XA, the linear ranges were 0.42–11.87μM and 0.07–2.02μM with detection limits of 5.39×10−9M and 2.36×10−9M, respectively. The proposed method was successfully applied to simultaneous determination of UA and XA in human urine and serum samples with satisfactory results.

In Situ Growth of Fe2O3 Nanoparticles on Highly Porous Graphene/Polyimide‐Based Carbon Aerogel Nanocomposites for Effectively Selective Detection of Dopamine

It is very important to develop a simple, efficient, and scaleable method for detection of dopamine (DA) with high sensitivity and selectivity to diagnose some serious neurological diseases. Herein, electro‐catalysts for detection of DA are simply prepared based on Fe2O3 nanoparticles (NPs) decorated on highly porous carbon aerogels (CAs), which are derived from KOH activated graphene‐polyimide aerogels. In the hierarchical nanocomposites (NCs), CAs provide large specific surface area, abundant mesopores, and macropores, and many sites for in situ growth of Fe2O3 NPs, thus effectively preventing the aggregation of Fe2O3 NPs. Moreover, CAs with 3D interconnected porous structures are able to shorten the charge transfer pathways through the intimate interaction between CAs and Fe2O3 NPs. Therefore, when applied as electro‐catalysts for detection of DA, the optimized NC exhibits rapid amperometric response and a low detection limit of 0.109 × 10−6 m (S/N = 3), with a wide linear concentration range from 5 to 500 × 10−6 m. In addition, the oxidation peak of DA can be readily distinguished from the interference of uric acid and ascorbic acid. Therefore, the highly porous CAs derived from KOH activated graphene‐polyimide aerogels are excellent substrates for in situ growth of Fe2O3 NPs, exhibiting high electrocatalytic activity for DA detection.