Detection Of Hypoxanthine Research Articles

Facile synthesis of Eu3+-doped niobium carbide MXene quantum dots for parallel detection of hypoxanthine and fluoxetine via fluorescence quenching and enhancement mechanisms.

Ahydrothermal synthetic method is established to produce blue fluorescent Eu3+-doped niobium carbide MXene quantum dots (Eu3+-Nb2C MQDs). The synthesized Eu3+-Nb2C MQDs demonstrated a quantum yield of 20.61% and a maximum emission intensity at 405nm. The as-prepared Eu3+-Nb2C MQDs acted as a sensor for the rapid and sensitive detection of hypoxanthine through fluorescence quenching, and of fluoxetine through fluorescence enhancement mechanisms. The emission peak of Eu3+-Nb2C MQDs at 405nm exhibited a linear response for hypoxanthine and fluoxetine in the ranges of 0.5-25µM and 0.125-2.5µM, with detection limits of 15.0 and 3.7nM, respectively. The newly developed probe was effectively used for the selective detection of hypoxanthine and fluoxetine in biofluids and pharmaceutical samples. Remarkably, theEu3+-Nb2C MQDs exhibited minimal cytotoxicity towards A549 lung cancer cells and showed great potential as imaging agent for imaging of Saccharomyces cerevisiae cells.

Hydrothermally Synthesized Cerium Phosphate with Functionalized Carbon Nanofiber Nanocomposite for Enhanced Electrochemical Detection of Hypoxanthine

This work presents the detection of hypoxanthine (HXA), a purine derivative that is similar to nucleic acids who overconsumption can cause health issues, by using hydrothermally synthesized cerium phosphate (CePO4) followed by a sonochemical approach for CePO4 decorated with a functionalized carbon nanofiber (CePO4@f-CNF) nanocomposite. The formation of the nanocomposite was confirmed with X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). A CePO4@f-CNF nanocomposite is used to modify a glassy carbon electrode (GCE) to analyze the electrochemical detection of HXA. Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and Differential pulse voltammetry (DPV) were used to examine the electrochemical properties of the composite. As a result, the modified electrode exhibits a larger active surface area (A = 1.39 cm2), a low limit of detection (LOD) at 0.23 µM, a wide linear range (2.05–629 µM), and significant sensitivity. Therefore, the CePO4@f-CNF nanocomposite was used to study the real-time detection in chicken and fish samples, and it depicted significant results.

A smartphone-assisted portable sensing hydrogel modules based on UCNPs and Co3O4 NPs for fluorescence quantitation of hypoxanthine in aquatic products

Hypoxanthine is a promising index for evaluating the freshness of various aquatic products. Combined the hydrogels containing upconversion nanoparticles (UCNPs), Co3O4 NPs, and N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt/4-amino-antipyrine (TOPS/4-AAP) with a smartphone, a portable sensor was developed for the convenient, sensitive detection of hypoxanthine. With the H2O2 from xanthine oxidase (XOD)-catalyzed reactions of hypoxanthine, the fluorescence of UCNPs was effectively quenched by the purple product produced from the oxidization of TOPS/4-AAP catalyzed by Co3O4 NPs exhibiting peroxidase activity, among which the color change could be transformed into digital signals for quantification of hypoxanthine. The Green value in the RGB analysis of the fluorescence image was negatively proportional to hypoxanthine concentration in the range of 2.5–20 mg/L with a detection limit of 0.69 mg/L and a quantitation limit of 2.30 mg/L. Finally, this sensor was applied for hypoxanthine detection in real aquatic products, showing potential application for freshness evaluation of aquatic products.

Non-enzymatic electrochemical sensor based on ZnO nanoparticles/porous graphene for the detection of hypoxanthine in pork meat

In this study, we developed a pioneering non-enzymatic electrochemical sensor utilizing a flexible porous graphene electrode modified with ZnO nanoparticles (ZnO/fPGE sensor) to assess hypoxanthine (HXA) content in pork at post-mortem time. The ZnO/fPGE sensor was synthesized via hydrothermal method and direct laser writing with a CO2 laser on a polyimide film at ambient conditions. Its characterization was analyzed by Raman, Fourier-transform infrared spectroscopy, field-emission scanning microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetric techniques. Linear response, the limit of detection, and sensitivity to the HXA were enhanced with the values of the range from 1.5 to 150, 0.14 µM, and 6.6 µA μM−1 cm−2, respectively. Effective resistance to common physiological interferences (such as uric acid, ascorbic acid, dopamine, glucose, and xanthine) was indicated, and additionally, the determination of HXA concentration in real samples with good selectivity is attributed to the synergistic effects between ZnO nanoparticles and fPGE. Therefore, the ZnO/fPGE has provided a favorable electrical environment for developing high-performance electrochemical biosensors to determine hypoxanthine in pork meat.

BCNO quantum dots-based ratiometric fluorescence platform integrated with portable device: Hypoxanthine sensing for on-site assessment of meat freshness with deep learning

Deep learning algorithms have been applied to digital image colorimetry (DIC) to improve color measurement and analysis, enabling the identification and quantification of analytes. In this work, we developed a smartphone-assisted platform for the detection of hypoxanthine (Hx) based on a ratiometric fluorescent probe (RF-probe) and deep learning algorithm for the first time with advantages of high sensitivity, in-field and simple operation, and accurate detection. Through an enzymatic cascade reaction, xanthine oxidase (XOD) degraded Hx to uric acid (UA) and H2O2, o-phenylenediamine (OPD) was converted to 2,3-diaminophenoxazine (DAP) by catalytic oxidation of H2O2 and OPD under horseradish peroxidase (HRP). The presence of DAP led to fluorescence quenching of BCNO quantum dots (BCNO QDs) at 440 nm and fluorescence enhancement of DAP at 570 nm due to the internal filtration effect (IFE). With the addition of Hx, the fluorescence color changed from blue to yellow. A good linear relationship was between I570/I440 and the Hx concentration in the range of 3-100 µM with a detection limit of 50 nM. Fluorescent color images of solution and test strips were acquired and extracted with a smartphone of our designed miniature device, which could be used to establish DIC for the detection of Hx with the linear relationship ranging from 0-100 μM and 0-40 μM, respectively. Then YOLOv5-assisted deep learning was applied to recognize and deal with the images, which offered improved accuracy, faster inference speed, flexibility, and efficient training. Therefore, our simple DIC platform was established for the in-field detection of Hx in real meat samples which was significant for the analysis of meat freshness and provided broad application potential for the analysis of other targets in food safety.

A ratiometric fluorescent probe for hypoxanthine detection in aquatic products based on the enzyme mimics and fluorescence of cobalt-doped carbon nitride

A ratiometric fluorescent probe for hypoxanthine (Hx) detection was established based on the mimic enzyme and fluorescence characteristics of cobalt-doped graphite-phase carbon nitride (Co doped g-C3N4). In addition to emitting strong fluorescence, the peroxidase activity of Co doped g-C3N4 can catalyze the reaction of O-phenylenediamine and H2O2 to produce diallyl phthalate which can emit yellow fluorescence at 570 nm. Through the decomposition of Hx by xanthine oxidase, Hx can be indirectly detected by the generating hydrogen peroxide based on the measurement of fluorescent ratio I (F570/F370). The linear range was 1.70–272.2 mg/kg (R2 = 0.997), and the detection limit was 1.52 mg/kg (3σ/K, n = 9). The established method was applied to Hx detection in bass, grass carp, and shrimp, and the data were verified by HPLC. The result shows that the established probe is sensitive, accurate, and reliable, and can be used for Hx detection in aquatic products.

Dual-Modal Bimetallic Nanozyme-Based Sensing Platform Combining Colorimetric and Photothermal Signal Cascade Catalytic Enhancement for Detection of Hypoxanthine to Judge Meat Freshness.

Considering the enormous demand for meat in people's daily lives, the development of efficient meat freshness assays is of great significance for safeguarding food safety. Here, a novel bimetallic nanozyme Fe@CeO2 with high peroxidase-like activity was first synthesized by embedding ferrocenecarboxylic acid (Fc) into hollow CeO2 nanospheres, which combined with xanthine oxidase (XOD) to develop a self-supplying H2O2-facilitated enzymatic cascade catalytic system of XOD + Fe@CeO2, yielding a meat freshness indicator hypoxanthine (Hx)-responsive colorimetric and photothermal dual-mode analytical platform for judging meat freshness upon the assistance of 3,3',5,5'-tetramethylbenzidine (TMB). Owing to the catalytic activity of XOD to convert Hx into H2O2, Fe@CeO2 rapidly dissociated it into •OH via a peroxidase activity-triggered Fenton-like reaction, emerging a typical enzymatic cascade catalytic reaction. As a result, the colorless TMB was oxidized to be the product of dark-blue oxTMB by •OH, with a chromogenic reaction-driven absorption enhancement at 652 nm, which endowed it with a significant photothermal effect under 660 nm laser irradiation. On this basis, an Hx concentration-dependent colorimetric and photothermal dual-mode signal cascade catalytic enhancement sensing platform was proposed by integrating with a Color Picker App-installed smartphone and a 660 nm laser-equipped handheld thermal imager, achieving the onsite quantitative, reliable, and visual detection of Hx in real meat samples for judging meat freshness with acceptable results. Notably, the colorimetric and photothermal dual-mode signal cascade catalytic enhancement improved not only the reliability but also the sensitivity of the assay, which provided new insights for efficient onsite visual monitoring of meat freshness to safeguard food safety.

MnO2 in-situ coated upconversion nanosystem for turn-on fluorescence detection of hypoxanthine in aquatic products

Hypoxanthine concentration is a potential indicator to evaluate the freshness in the early post-mortem of several aquatic products. Based on MnO2 in-situ coated upconversion nanoparticles (UCNPs) and xanthine oxidase (XOD), a novel sensor was conducted for the efficient, sensitive determination of hypoxanthine. In this strategy, upconversion fluorescence quenched by MnO2 would be restored by H2O2 and uric acid (UA), two products from the XOD-catalyzed reactions of hypoxanthine. Through pretreatment with short-time heating and alkylation by N-ethylmaleimide (NEM) to avoid potential interference from reducing substances in the food matrix, this method exhibited satisfactory selectivity. The fluorescence intensity of green emission Igreen was positively proportional to hypoxanthine concentration at a wide range of 0.5–50 mg/L with a detection limit of 0.14 mg/L. Moreover, this convenient method was employed to quantify the hypoxanthine in fish, shrimp, and shellfish samples, showing excellent potential for the application in quality control of aquatic products.

Surface-Enhanced Raman Analysis of Uric Acid and Hypoxanthine Analysis in Fractionated Bodily Fluids.

In recent years, the disease burden of hyperuricemia has been increasing, especially in high-income countries and the economically developing world with a Western lifestyle. Abnormal levels of uric acid and hypoxanthine are associated with many diseases, and therefore, to demonstrate improved methods of uric acid and hypoxanthine detection, three different bodily fluids were analysed using surface-enhanced Raman spectroscopy (SERS) and high-performance liquid chromatography (HPLC). Gold nanostar suspensions were mixed with series dilutions of uric acid and hypoxanthine, 3 kDa centrifugally filtered human blood serum, urine and saliva. The results show that gold nanostars enable the quantitative detection of the concentration of uric acid and hypoxanthine in the range 5-50 μg/mL and 50-250 ng/mL, respectively. The peak areas of HPLC and maximum peak intensity of SERS have strongly correlated, notably with the peaks of uric acid and hypoxanthine at 1000 and 640 cm-1, respectively. The r2 is 0.975 and 0.959 for uric acid and hypoxanthine, respectively. Each of the three body fluids has a number of spectral features in common with uric acid and hypoxanthine. The large overlap of the spectral bands of the SERS of uric acid against three body fluids at spectra peaks were at 442, 712, 802, 1000, 1086, 1206, 1343, 1436 and 1560 cm-1. The features at 560, 640, 803, 1206, 1290 and 1620 cm-1 from hypoxanthine were common to serum, saliva and urine. There is no statistical difference between HPLC and SERS for determination of the concentration of uric acid and hypoxanthine (p > 0.05). For clinical applications, 3 kDa centrifugal filtration followed by SERS can be used for uric acid and hypoxanthine screening is, which can be used to reveal the subtle abnormalities enhancing the great potential of vibrational spectroscopy as an analytical tool. Our work supports the hypnosis that it is possible to obtain the specific concentration of uric acid and hypoxanthine by comparing the SER signals of serum, saliva and urine. In the future, the analysis of other biofluids can be employed to detect biomarkers for the diagnosis of systemic pathologies.

Gelatin-based smart film incorporated with nano cerium oxide for rapid detection of shrimp freshness

A novel and convenient nano cerium oxide peroxidase mimic smart film for rapid detection of hypoxanthine (HX) concentrations to predict shrimp freshness was reported. Xanthine oxidase was incorporated into the smart film to react with HX and produce H2O2. Cerium oxide nanoparticles (CeNPs), as redox amplifiers and chromogenic agents, were oxidized by H2O2 to produce regular color changes to quantify HX concentrations. All components entrapped in a three-dimensional gelatin matrix crosslinked with glutaraldehyde. The nanostructure of CeNPs and the feasibility of their use as multifunctional nanozymes for HX detection were explored, as were the effects of CeNPs addition on the physical and colorimetric properties of the film. The morphology and HX sensitivity were also characterized, and their feasibility in monitoring shrimp freshness was further verified. The results showed the gelatin/glutaraldehyde film with 25% CeNPs had good performance. This film had a high sensitivity, with a linear range of HX detection of 6.2–200 μM and the lower limit of detection of 35 μM. Furthermore, the film could determine the shrimp freshness level with a predictive accuracy of approximately 0.9223. This method can be applied for packaging food as a freshness indicator because of its convenience, high sensitivity, and low cost.

Downregulation of Peroxidase Activity of Platinum Cube Enables Minute-Time Scale Colorimetric Signaling of Hypoxanthine for Fish Freshness Monitoring.

Due to its unique biological composition, aquatic products, especially fish, are extremely perishable compared to other muscle products. Herein, we proposed an artificial nanozyme-based colorimetric detection of hypoxanthine (Hx), the indicator of fish freshness, in a minute-time scale without the assistance of a natural enzyme (hypoxanthine oxidase). The principle is based on the interaction between Hx and polyvinylpyrrolidone-modified platinum cubic nanomaterials (PVP-PtNC), in which the catalytic active sites of PVP-PtNC's surface were blocked by Hx. This causes the downregulation of PVP-PtNC's catalytic ability and weakened its ability to catalyze the oxidization of 3,3',5,5'-Tetramethylbenzidine (TMB) by H2O2. Accordingly, the decrease in the UV-vis absorption and the weakening of the colorimetric reaction color is proportional to the Hx concentration. On this basis, a target-triggered colorimetric method for detecting Hx is developed for fish freshness monitoring with a fast detection speed, low cost, high accuracy, and simplified operation. Experiments reveal that the correlation response of Hx is from 0.5 μM to 10 mM with a limit of detection of 0.16 μM. In particular, the Hx detected from real fish indicates that the method possesses a promising potential for practical application. All of these features are expected to promote the development of online detection tools for food safety monitoring.

Molecularly Imprinted Polymer-Based Electrochemical Sensor for Rapid and Selective Detection of Hypoxanthine.

In this paper, we report on the coupling of an electrochemical transducer with a specifically designed biomimetic and synthetic polymeric layer that serves as a recognition surface that demonstrates the molecular memory necessary to facilitate the stable and selective identification of the meat-freshness indicator hypoxanthine. Consumer preferences and the food safety of meat products are largely influenced by their freshness, so it is crucial to monitor it so as to quickly identify when it deteriorates. The sensor consists of a glassy-carbon electrode, which can be regenerated in situ continuously, functionalized with molecularly imprinted polymers (MIPs) and a nanocomposite of curcumin-coated iron oxide magnetic nanospheres (C-IO-MNSs) and multiwalled carbon nanotubes (MWCNTs) that enhance the surface area as well as the electroactive characteristics. The electrochemical behavior of the fabricated sensor was analyzed by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetric studies revealed the rapid response of the proposed sol-gel-MIP/MWCNT/C-IO-MNS/GCE sensor to hypoxanthine in a concentration range of 2-50 µg/mL with a lower limit of detection at 0.165 μg/mL. Application of the newly fabricated sensor demonstrated acceptable recoveries and satisfactory accuracy when used to measure hypoxanthine in different meat samples.

Co(OH)2/MXene-Ti3C2 nanocomposites with triple-enzyme mimic activities as hydrogel sensing platform for on-site detection of hypoxanthine.

Novel Co(OH)2/MXene-Ti3C2 nanocomposites with oxidase (OXD)-mimic, peroxidase (POD)-mimic, and catalase (CAT)-mimic activities were prepared by asimple two-step method. The Co(OH)2/MXene-Ti3C2 nanocomposites with triple-enzyme mimic activities were embedded into sodium alginate (SA) gels for the first time to fabricate a target-responsive hydrogel-assisted assay. The catalytic mechanism and steady-state kinetics of Co(OH)2/MXene-Ti3C2 nanocomposites were investigated. Subsequently, hypoxanthine (Hx) was catalyzed by xanthine oxidase (XOD) to form H2O2, which reacts with 3,3',5,5'-tetramethyl-benzidine (TMB) in the presence of Co(OH)2/MXene-Ti3C2 nanocomposites to form a blue oxide (ox-TMB) in the hydrogel. The visible color change of the hydrogel with the increase of Hx concentration can be recognized through a smartphone App to transfer the red (R), green (G), and blue (B) values for the quantitative determination of Hx, with adetection range from 5 to 250μM, and detection limit of0.2μM. Themethod was applied to the determination of Hx content in different aquatic products. The spiked recoveries of the aquatic products were from 94.1 to 106.4%, and the relative standard deviations (RSD) were less than 5.4%. Our results show that the Co(OH)2/MXene-Ti3C2 nanocomposites hydrogel-assisted colorimetric biosensor is cost-effective, sensitive, and selective andhas excellent application prospects forin-the-field determinationof Hx.

Cu nanoclusters decorated Ti3C2 nanosheets composite with tetraenzyme mimic activities and the application for smartphone-assisted detection of hypoxanthine

MXene-based nanozymes have increased research enthusiasm in the field of food safety and environment monitoring. Herein, the Cu NCs/Ti3C2 NSs nanocomposites were prepared by modifying copper nanoclusters (Cu NCs) on the surface of Ti3C2 nanosheets (NSs) with a simple two-step method. The Cu NCs/Ti3C2 NSs nanocomposites had outstanding tetraenzyme mimic activities, i.e. peroxidase (POD)-mimics, catalase (CAT)-mimics, ascorbic acid oxidase (AAO)-mimics and superoxide dismutase (SOD)-mimics. Modification of Cu NCs on Ti3C2 NSs can enhance tetraenzyme mimic activities because of the synergistic catalytic effect between Cu NCs and Ti3C2 NSs. The catalytic mechanism and steady-state kinetics of Cu NCs/Ti3C2 NSs were also investigated. Based on the POD-mimic activity of Cu NCs/Ti3C2 NSs, a simple and rapid colorimetric method was established for the on-site detection of hypoxanthine (Hx), with the linear range of 5–200 μM and limit of detection (LOD) was 0.25 μM. The visible color change with the increase of Hx concentration can be recognized by a smartphone APP to transfer the red (R), green (G) and blue (B) value for the quantitative analysis of Hx, with the linear range of 10–200 μM, which provided a convenient method for the real-time detection of Hx. This work not only provides a significant route to fabricate nanocomposite with outstanding tetraenzyme mimic activities but also offers a low-cost and rapid method for monitoring the freshness of aquatic products.

Development of curcumin/rice starch films for sensitive detection of hypoxanthine in chicken and fish meat

Food freshness monitoring, which is reflected in the quality of the product at the time of use, remains a significant challenge for both consumers and the food industry. This paper presents an experimental study on the development of a biodegradable, film-based curcumin, incorporated with modified rice starch, that may be used to detect hypoxanthine in chicken and fish. The physicochemical properties of the films were characterized and analyzed through several different approaches, including moisture content, water absorption, and water solubility. The morphology characteristics were analyzed using an SEM. The nanocomposite of the films showed excellent physical and chemical properties that bettered the control film used in the study. The deprotonation of curcumin occurs when the indicator is exposed to a pH level of 9 and above, where the indicator's color changes from yellow to a reddish-brown or wine-red color, which can be seen by the naked eye. The thickness of the films increased as the concentration of curcumin rose to 3%, showing that they were more stable than other films. The stability of the films increased when they were kept at a lower temperature (4 °C). Under optimum conditions, the detection limit of the film was found to be at 38.63 μM, with a limit of quantification of 128.75 μM, and the linear working range was determined to be from 0 to 100 μM. The concentration of hypoxanthine in chicken meat and fish was determined to be 30.25 μM and 52.84 μM, respectively. The recovery rate of the technique used was from 99.94 to 104.11%.Therefore, these results encourage the use of curcumin films as active packaging material in monitoring the freshness of various meat products.

Smart phone assisted paper-based biosensor system for hypoxanthine detection in fish meat samples

In this work, we present the development of a paper-based, low-cost, sensitive, quantitative and stable platform proper for smartphone-assisted colorimetric detection of the fresh fish product to eliminate people’s concerns while consuming seafood. Biocompatible zones were prepared onto the paper filter material by chitosan modification an d mu lti-enzyme immobilization in the developed biosensor system. The visual detected result was connected with the hypoxanthine (Hx) amount by using a smartphone app that can perform image processing to evaluate the quantitative detection. Selectivity, specificity, stability, and direct real sample tests indicated the potential usability of the developed paper-based biosensor system for Hx detection in meat samples with an easy-to-use method. An application for examination of Hx concentration in real fish meat was achieved by placing the paper-based biosensor in contact with fish skin. As a future perspective, the developed method can be practical in developing portable biosensors to assess the fish freshness grade.

One-Step and Colorimetric Detection of Fish Freshness Indicator Hypoxanthine Based on the Peroxidase Activity of Xanthine Oxidase Grade I Ammonium Sulfate Suspension.

The global food waste problem, especially aquatic product spoilage, stimulates the accurate freshness analysis of food products. However, it still remains a great challenge to realize in-field determination of fish freshness at the time of use. In the present study, a colorimetric enzyme biosensor was developed for one-step detection of hypoxanthine (Hx), which is an important intermediate of adenosine triphosphate decomposition during fish storage. We demonstrate that xanthine oxidase grade I ammonium sulfate suspension (XOD-ASS) possesses peroxidase activity. It can oxidize different peroxidase substrates, including 3,3′,5,5′-tetramethylbenzidine, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and o-phenylenediamine in the presence of H2O2, producing visible color reactions. Further experiments indicate that XOD-ASS displayed effective peroxidase activity and could be used for H2O2 detection. Based on this, a one-step Hx detection method was established using only XOD-ASS as the catalyst. The method displays a good linear relationship in the range from 20 to 100 μM with a detection limit of 6.93 μM. Additionally, we successfully applied this method in testing Hx accumulation in sea bass fish samples of different storage times. The recovery values range from 97.44 to 102.56%. It is exciting to note that, compared with other methods, our proposed method provides a robust advantage on the economic reaction system, ease of preparation, short time consumption, and moderate reaction temperature. We believe that this method shows good application prospects for on-site fish freshness determination.

Detection of Hypoxanthine from Inosine and Unusual Hydrolysis of Immunosuppressive Drug Azathioprine through the Formation of a Diruthenium(III) System.

Hypoxanthine (hpx) is an important molecule for both biochemistry research and biomedical applications. It is involved in several biological processes associated to energy and purine metabolism and has been proposed as a biomarker for a variety of disease states. Consequently, the discovery and development of systems suitable for the detection of hypoxanthine is pretty appealing in this research field. Thus, we have obtained a stable diruthenium (III) compound in its dehydrated and hydrated forms with formula [{Ru(µ-Cl)(µ-hpx)}2Cl4] (1a) and [{Ru(µ-Cl)(µ-hpx)}2Cl4]·2H2O (1b), respectively. This purine-based diruthenium(III) system was prepared from two very different starting materials, namely, inosine and azathioprine, the latter being an immunosuppressive drug. Remarkably, it was observed that an unusual azathioprine hydrolysis occurs in the presence of ruthenium, thus generating hypoxanthine instead of the expected 6-mercaptopurine antimetabolite, so that the hpx molecule is linked to two ruthenium(III) ions. 1a and 1b were characterized through IR, SEM, powder and single-crystal X-ray Diffraction and Cyclic Voltammetry (CV). The electrochemical studies allowed us to detect the hpx molecule when coordinated to ruthenium in the reported compound. The grade of sensitivity, repeatability and stability reached by this diruthenium system make it potentially useful and could provide a first step to develop new sensor devices suitable to detect hypoxanthine.

Colorimetric detection of hypoxanthine in aquatic products based on the enzyme mimic of cobalt-doped carbon nitride

A colorimetric method for the rapid detection of Hx in aquatic products was established based on the peroxidase-like activity of cobalt-doped graphite phase carbon nitride (Co-doped-g-C3N4).

Paper-Based Enzyme Biosensor for One-Step Detection of Hypoxanthine in Fresh and Degraded Fish.

Food freshness monitoring, which can reflect the quality of the product at the time of use, remains a great challenge for consumers and the food industry. Herein, we report the development of a cost-effective enzyme-based paper biosensor, which can monitor fish freshness and predict spoilage. The biosensor measures the release of hypoxanthine (HX), an indicator of meat and fish degradation, using the enzymatic conversion of HX by xanthine oxidase (XOD). We demonstrate that the entrapment of XOD and an organic dye, nitro blue tetrazolium chloride (NBT), within a sol-gel biohybrid enables their stabilization on paper and promotes the enzymatic reaction with further retention of the reaction products within the cellulosic network . Linearity in the micromolar concentration range with a detection limit of 3.7 μM for HX is obtained. The biosensor has high selectivity toward HX and is manufactured in few steps from inexpensive widely available materials. The applicability of the biosensor is demonstrated by following fish degradation over time and measuring HX concentrations ranging from 117 (±9) to 198 (±5) μM within 24 h of degradation, at levels that are comparable with those measured by a commercial enzymatic kit for HX detection. As compared to the commercial kit, our biosensors are more cost-effective, do not require addition of exogenous reagents and are portable, having all of the reagents needed for analysis embedded within the sensing platform. This proof-of-concept work demonstrates that the paper-based HX biosensor has potential as a robust reagentless device for real-time monitoring of food freshness and for other applications in which HX plays an important role.