In-situ synthesized MgIn2S4/CdWO4 type-II heterojunction as a light-driven photoelectrochemical sensor for ultrasensitive detection of catechol in environmental water samples.

As an essential chemical intermediate, catechol (CC) residues may have adverse effects on human health. Herein, an effective and facile photoelectrochemical sensor platform based on MgIn2S4/CdWO4 composite is constructed for monitoring CC. MgIn2S4 increases light absorption range and activity, while CdWO4 enhances photoelectronic stability, and the type-II heterojunction formed can significantly enhance photocurrent response. Due to the autoxidation process, CC is converted into oligomeric products, which increase the spatial site resistance and attenuate the overall photocurrent response. It is worth noting that the cauliflower-like structure of MgIn2S4 can provide a large specific surface area, and the presence of Mg2+ promotes autoxidation, thus providing a suitable condition for detecting CC. Under optimal conditions, the MgIn2S4/CdWO4/GCE photoelectrochemical sensor has a prominent linear relationship in the range of CC concentration from 2 nM to 7 µM, with a limit of detection of 0.27 nM. With satisfactory selectivity, excellent stability, and remarkable reproducibility, this sensor provides a crucial reference value for effectively and rapidly detecting pollutants in environmental water samples.

Multilayer Ti3 C2 -CNTs-Au Loaded with Cyclodextrin-MOF for Enhanced Selective Detection of Rutin.

In this work, multi-layer Ti3 C2 - carbon nanotubes - gold nanoparticles (Ti3 C2 -CNTs-Au) and cyclodextrin metal-organic framework - carbon nanotubes (CD-MOF-CNTs) have been prepared by in situ growth method and used to construct the ultra-sensitive rutin electrochemical sensor for the first time. Among them, the large number of metal active sites of Ti3 C2 , the high electron transfer efficiency of CNTS, and the good catalytic properties of AuNPs significantly enhance the electrochemical properties of the composite carbon nanomaterials. Interestingly, CD-MOF has a unique host-guest recognition and a large number of cavities, molecular gaps, and surface reactive groups, which gives the composite outstanding accumulation properties and selectivity for rutin. Under the optimized conditions, the constructed novel sensor has satisfactory detection performance for rutin in the range of 2 × 10-9 to 8 × 10-7  M with a limit of detection of 6.5 × 10-10  M. In addition, the sensor exhibits amazing anti-interference performance against rutin in some flavonoid compounds and can be used to test natural plant samples (buckwheat, Cymbopogon distans, and flos sophorae immaturus). This work has promising applications in the field of environmental and food analysis, and exploring new directions for the application of Mxene-based composites.

USP36 stabilizes nucleolar Snail1 to promote ribosome biogenesis and cancer cell survival upon ribotoxic stress.

Tumor growth requires elevated ribosome biogenesis. Targeting ribosomes is an important strategy for cancer therapy. The ribosome inhibitor, homoharringtonine (HHT), is used for the clinical treatment of leukemia, yet it is ineffective for the treatment of solid tumors, the reasons for which remain unclear. Here we show that Snail1, a key factor in the regulation of epithelial-to-mesenchymal transition, plays a pivotal role in cellular surveillance response upon ribotoxic stress. Mechanistically, ribotoxic stress activates the JNK-USP36 signaling to stabilize Snail1 in the nucleolus, which facilitates ribosome biogenesis and tumor cell survival. Furthermore, we show that HHT activates the JNK-USP36-Snail1 axis in solid tumor cells, but not in leukemia cells, resulting in solid tumor cell resistance to HHT. Importantly, a combination of HHT with the inhibition of the JNK-USP36-Snail1 axis synergistically inhibits solid tumor growth. Together, this study provides a rationale for targeting the JNK-USP36-Snail1 axis in ribosome inhibition-based solid tumor therapy.

Detection of gallic acid in food using an ultra-sensitive electrochemical sensor based on glass carbon electrode modified by bimetal doped carbon nanopolyhedras.

Gallic acid is widely used as an antioxidant in food because of its good antioxidant function, but excessive intake induces side effects in humans, so it is essential to devise a highly responsive technique for detecting gallic acid. In this work, we synthesized ZIF-67@FePc by the one-pot method. The synthesized material is more stable at high temperatures compared to ZIF-67 and maintains its original morphology during pyrolysis, when iron was introduced as a second metal active site during the synthesis process. Subsequently, Co/FeOX@NC-800 was employed to fabricate a GA sensor on a GCE. The developed sensor exhibited remarkable sensitivity towards GA, featuring a low LOD of 1.30 nM and a linear range spanning from 5 to 4500 nM. The electrochemical sensors we have prepared also showed good selectivity, stability, and reproducibility. It has been successfully employed for detecting GA in actual samples such as apples, grapes, tomatoes, and red wine.

Fabricating process-electrochemical property correlation of laser-scribed graphene and smartphone-based electrochemical platform for portable and sensitive biosensing.

Laser-scribed graphene (LSG), a promising electrode material has attracted special research interest in recent years. Here, the fabricating process-electrochemical property correlation of laser-scribed graphene (LSG) devices was discussed emphatically and a pertinent optimization was performed to achieve better electroanalytical performance. Experiment results indicated that the laser scribing technique possessed great process latitude and reducing laser power and scribing speed facilitated fabricating high-quality graphene electrodes. Benefiting from its binder-free 3D porous network structure and high active/geometric area ratio, the optimized LSG electrode was superior to the screen-printed carbon electrode (SPCE) on electrochemical performance in the [Fe(CN)6]3-/4- redox system. Integrating the LSG electrode with a homemade hand-held detector, a portable electrochemical sensing platform with smartphone readout was developed. It realized a specific detection of H2O2 (linear range: 0.02-3.4 mM, sensitivity: 24.56 µA mM-1 cm-2), glucose (linear range: 0.04-4.0 mM, sensitivity: 16.35 µA mM-1 cm-2) by directly decorating biological enzymes without artificial redox mediator and featured a satisfactory comprehensive performance. The constructed immunosensor for tumor necrosis factor-α exhibited a wide linear range (2-500 pg mL-1) and a 4.3-fold enhancement in sensitivity compared with that of SPCE. With satisfactory selectivity, reproducibility, and sensitivity, the developed smartphone-based electrochemical sensing platform held great promise in accurate detection on the spot. This work also provided a significant reference for tailoring binder-free carbonaceous electrode materials toward the desired application.

An ultrasensitive dietary caffeic acid electrochemical sensor based on Pd-Ru bimetal catalyst doped nano sponge-like carbon.

Caffeic acid (CA) is widely present in the human daily diet, and a reliable CA detection method is beneficial to food safety. Herein, we constructed a CA electrochemical sensor employing a glassy carbon electrode (GCE) which was modified by the bimetallic Pd-Ru nanoparticles decorated N-doped spongy porous carbon obtained by pyrolysis of the energetic metal-organic framework (MET). The high-energy bond N-NN in MET explodes to form N-doped sponge-like carbon materials (N-SCs) with porous structures, boosting the adsorptive capacity for CA. The addition of Pd-Ru bimetal improves the electrochemical sensitivity. The linear range of the PdRu/N-SCs/GCE sensor is 1 nM-100 nM and 100 nM-15 µM, with a low detection limit (LOD) of 0.19 nM. It has a high sensitivity (55 µA/µM) and repeatability. The PdRu/N-SCs/GCE sensor has been used to detect CA in actual samples of red wine, strawberries, and blueberries, providing a novel approach for CA detection in food analysis.

Electrochemical Behavior of ß-Cyclodextrin-Ni-MOF-74/Reduced Graphene Oxide Sensors for the Ultrasensitive Detection of Rutin.

Rutin, as a biological flavonoid glycoside, has very important medicinal value. The accurate and rapid detection of rutin is of great significance. Herein, an ultrasensitive electrochemical rutin sensor based on ß-cyclodextrin metal-organic framework/reduced graphene oxide (ß-CD-Ni-MOF-74/rGO) was constructed. The obtained ß-CD-Ni-MOF-74 was characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption and desorption. The ß-CD-Ni-MOF-74/rGO presented good electrochemical properties benefiting from the large specific surface area and good adsorption enrichment effect of ß-CD-Ni-MOF-74 and the good conductivity of rGO. Under optimal conditions for the detection of rutin, the ß-CD-Ni-MOF-74/rGO/GCE showed a wider linear range (0.06-1.0 µM) and lower detection limit (LOD, 0.68 nM, (S/N = 3)). Furthermore, the sensor shows good accuracy and stability for the detection of rutin in actual samples.

An electrochemical sensor based on Ce-MOF-derived Ce-doped poly(3,4-ethylenedioxythiophene) composite for efficient determination of rutin in food.

As a common antioxidant and nutritional fortifier in food chemistry, rutin has positive therapeutic effects against novel coronaviruses. Here, Ce-doped poly(3,4-ethylenedioxythiophene) (Ce-PEDOT) nanocomposites derived through cerium-based metal-organic framework (Ce-MOF) as a sacrificial template have been synthesized and successfully applied to electrochemical sensors. Due to the outstanding electrical conductivity of PEDOT and the high catalytic activity of Ce, the nanocomposites were used for the detection of rutin. The Ce-PEDOT/GCE sensor detects rutin over a linear range of 0.02-9 µM with the limit of detection of 14.7 nM (S/N = 3). Satisfactory results were obtained in the determination of rutin in natural food samples (buckwheat tea and orange). Moreover, the redox mechanism and electrochemical reaction sites of rutin were investigated by the CV curves of scan rate and density functional theory. This work is the first to demonstrate the combined PEDOT and Ce-MOF-derived materials as an electrochemical sensor to detect rutin, thus opening a new window for the application of the material in detection.

A light-driven photoelectrochemical sensor for highly selective detection of hydroquinone based on type-II heterojunction formed by carbon nanotubes immobilized in 3D honeycomb CdS/SnS2.

The ecological environment and public safety are seriously threatened by the typical phenolic contaminant hydroquinone (HQ). Here, using a straightforward physical mixing technique, we created an n-n heterojunction by uniformly immobilizing cadmium sulfide (CdS) nanoparticles on the surface of a three-dimensionally layered, flower-like structure made of tin sulfide (SnS2). Then, as photosensitizers, carbon nanotubes (CNTs) were added to the CdS/SnS2 complex to create a type-II heterostructure of CdS/SnS2/CNTs with synergistic effects. Subsequently, the detector HQ was bound to the modified photoelectrodes, which was accompanied by the hole oxidation of the bound HQ, leading to a significant increase in the photocurrent signal, thus allowing specific and sensitive detection of HQ. Under optimized detection conditions, the proposed photoelectrochemical sensor shows a wide detection range of 0.2 to 100 µM for HQ with a detection limit as low as 0.1 µM. The high accuracy of the sensor was demonstrated by comparison with the detection results of UV-vis spectrophotometry. In addition, the photoelectrochemical sensor exhibits good reproducibility, stability, selectivity, and specificity, providing a light-driven method to detect HQ.

A "Special" Solvent to Prepare Alloyed Pd2Ni1 Nanoclusters on a MWCNT Catalyst for Enhanced Electrocatalytic Oxidation of Formic Acid.

Herein, an electrocatalyst with Pd2Ni1 nanoclusters, supporting multiwalled carbon nanotubes (MWCNTs) (referred to Pd2Ni1/CNTs), was fabricated with deep eutectic solvents (DES), which simultaneously served as reducing agent, dispersant, and solvent. The mass activity of the catalyst for formic acid oxidation reaction (FAOR) was increased nearly four times compared to a Pd/C catalyst. The excellent catalytic activity of Pd2Ni1/CNTs was ascribed to the special nanocluster structure and appropriate Ni doping, which changed the electron configuration of Pd to reduce the d-band and to produce a Pd-Ni bond as a new active sites. These newly added Ni sites obtained more OH- to release more effective active sites by interacting with the intermediate produced in the first step of FAOR. Hence, this study provides a new method for preparing a Pd-Ni catalyst with high catalytic performance.

A novel photoelectrochemical sensor based on flower-like SnS2, sea urchin-like AgBiS2 and graphene oxide nanocomposite film for efficient and sensitive detection of acetaminophen in lake water samples.

As an emerging detection technology, photoelectrochemical sensors have been widely noticed for their unique technical features. Among others, the technology has been widely used in the fields of drug, biological antibody or antigen and contaminant detection. Secondly, acetaminophen, as a novel environmental pollutant, is difficult to be degraded in the ecosystem, which in turn causes serious impacts on the ecosystem. Therefore, in this work, we designed a photoelectrochemical sensor based on a composite film of flower-like SnS2, sea urchin-like AgBiS2 and graphene oxide for the detection of acetaminophen in water samples. Among them, graphene oxide, as a two-dimensional carbon-based material, can immobilize other photoelectric materials well. In addition, the flower-like SnS2 and sea urchin-like AgBiS2 can enhance the intensity of the photoelectric response due to their synergistic effect. Notably, the combination of graphene oxide with SnS2 and AgBiS2 revealed an exponential increase in the photoresponse intensity, indicating that SnS2/AgBiS2/GO has a satisfactory photoresponse intensity. At the same time, the photoelectrochemical sensor exhibited sensitive detection performance (LOD = 4 nM) and a wide detection range (0.01-50 µM) for acetaminophen under optimal detection conditions. Moreover, it also showed excellent detection performance in the detection of actual water samples, indicating that it can be applied to the detection of acetaminophen in lakes.

Near-Infrared Fluorescent Nanoprobes for Adenosine Triphosphate-Guided Imaging in Cancer and Fatty Liver Mice.

Adenosine triphosphate (ATP), as an indispensable biomolecule, is the main energy source of cells and is used as a marker for diseases such as cancer and fatty liver. It is of great significance to design a near-infrared fluorescent nanoprobe with excellent performance and apply it to various disease models. Here, a near-infrared fluorescent nanoprobe (ZIF-90@SiR) based on a zeolitic imidazole framework is proposed. The fluorescent nanoprobes are synthesized by encapsulating the dye (SiR) into the framework of ZIF-90. Upon the addition of ATP, the structure of the ZIF-90@SiR nanoprobe is disrupted and SiR is released to generate near-infrared fluorescence at 670 nm. In the process of ATP detection, ZIF-90@SiR shows high sensitivity and good selectivity. Moreover, the ZIF-90@SiR nanoprobe has good biocompatibility due to its low toxicity to cells. It is used for fluorescence imaging of ATP in living cells and thus distinguishing normal cells and cancer cells, as well as distinguishing fatty liver cells. Due to excellent near-infrared fluorescence properties, the ZIF-90@SiR nanoprobe can not only distinguish normal mice and tumor mice but also differentiate normal mice and fatty liver mice for the first time.

Neuromorphic functions with a polyelectrolyte-confined fluidic memristor.

Reproducing ion channel-based neural functions with artificial fluidic systems has long been an aspirational goal for both neuromorphic computing and biomedical applications. In this study, neuromorphic functions were successfully accomplished with a polyelectrolyte-confined fluidic memristor (PFM), in which confined polyelectrolyte-ion interactions contributed to hysteretic ion transport, resulting in ion memory effects. Various electric pulse patterns were emulated by PFM with ultralow energy consumption. The fluidic property of PFM enabled the mimicking of chemical-regulated electric pulses. More importantly, chemical-electric signal transduction was implemented with a single PFM. With its structural similarity to ion channels, PFM is versatile and easily interfaces with biological systems, paving a way to building neuromorphic devices with advanced functions by introducing rich chemical designs.

HSF1 activates the FOXO3a-ΔNp63α-CDK4 axis to promote head and neck squamous cell carcinoma cell proliferation and tumour growth.

Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent cancers worldwide. Heat shock factor 1 (HSF1) is a conserved transcriptional factor that plays a critical role in maintaining cellular proteostasis. However, the role of HSF1 in HNSCC development remains largely unclear. Here, we report that HSF1 promotes forkhead box protein O3a (FOXO3a)-dependent transcription of ΔNp63α (p63 isoform in the p53 family; inhibits cell migration, invasion, and metastasis), which leads to upregulation of cyclin-dependent kinase 4 expression and HNSCC tumour growth. Ablation of HSF1 or treatment with KRIBB11, a specific pharmacological inhibitor of HSF1, significantly suppresses ΔNp63α expression and HNSCC tumour growth. Clinically, the expression of HSF1 is positively correlated with the expression of ΔNp63α in HNSCC tumours. Together, this study demonstrates that the HSF1-ΔNp63α pathway is critically important for HNSCC tumour growth.

A long-term survival rat model of spinal cord ischemia injury: Thoracic aortic occlusion combined with aortic bypass circulation.

OBJECTIVE: This study aims to investigate the methods for rat spinal cord ischemia injury models with a high long-term survival rate. METHODS: The rats were divided into three groups: the treatment group, the control group, and the sham operation group. The treatment group had a blocked thoracic aorta (landing zone 3 by Ishimaru - T11) + aortic bypass circulation for 20 min. In the control group, the thoracic aorta at the landing zone 3 was blocked for 20 min. In the sham operation group, only thoracotomy without thoracic aortic occlusion was performed. The mean arterial blood pressure (MABP) of the thoracic aorta and caudal artery before and after thoracic aortic occlusion was monitored intraoperatively. Spinal cord function was monitored by a transcranial motor evoked potential (Tc-MEP) during the operation. Spinal cord function was evaluated by the BBB scale (Basso, Beattie, & Bresnahan locomotor rating scale) scores at multiple postoperative time points. The spinal cord sections of the rats were observed for 7 days after surgery, and the survival curves were analyzed for 28 days after surgery. RESULTS: After aortic occlusion, the MABP of thoracic aorta decreased to 6% of that before occlusion, and the MABP of caudal artery decreased to 63% of that before occlusion in the treatment group. In the control group, the MABP of both thoracic aorta and caudal artery decreased to 19% of that before occlusion. The Tc-MEP waveform of the treatment group disappeared after 6 min, and that of the control group disappeared after 8 min until the end of surgery. There was no change in the Tc-MEP waveform in the sham operation group. The BBB score of the treatment group decreased more obviously than the control group, and there was a significant difference. There was no decrease in the sham group. Spinal cord sections showed a large number of degeneration and necrosis of neurons, infiltration of inflammatory cells, and proliferation of surrounding glial cells in the treatment group. In the control group, multiple neurons were necrotic. The histology of the sham operation group was normal. The 28-day survival rate of the treatment group was 73.3%, which was higher than the control group (40.0%), and there was a significant difference (p < 0.05). CONCLUSION: Thoracic aortic occlusion combined with aortic bypass is an effective modeling method for rats with accurate modeling effects and high long-term survival rates.

Ultrasensitive Determination of Natural Flavonoid Rutin Using an Electrochemical Sensor Based on Metal-Organic Framework CAU-1/Acidified Carbon Nanotubes Composites.

Rutin, a natural flavonol glycoside, is widely present in plants and foods, such as black tea and wheat tea. The antioxidant and anti-inflammatory effects of flavonoids are well known. In this study, a new electrochemical rutin sensor was developed using multiwalled carbon nanotubes/aluminum-based metal-organic frameworks (MWCNT/CAU-1) (CAU-1, a type of Al-MOF) as the electrode modification material. The suspension of multiwalled carbon tubes was dropped on the surface of the GCE electrode to make MWCNT/GCEs, and CAU-1 was then attached to the electrode surface by electrodeposition. MWCNTs and CAU-1 were characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Due to the synergistic effect of CAU-1 and MWCNT-COOH, the prepared sensor showed an ultrasensitive electrochemical response to rutin. Under optimized conditions, the sensor showed a linear relationship between 1.0 × 10-9~3.0 × 10-6 M with a detection limit of 6.7 × 10-10 M (S/N = 3). The sensor also showed satisfactory stability and accuracy in the detection of real samples.

A novel temperature-responsive electrochemical sensing platform for reversible switch-sensitive detection of acetamidophenol.

A novel facile, quick, and temperature-controlled sensor was constructed based on a polystyrene-poly-N,N-diethyl acrylamide-polystyrene (PS-PDEAM)/carboxylated multi-walled carbon nanotube (MWCNT) composite modified glass carbon electrode. The sensor achieves acetaminophen (AP) reversibility through better temperature sensitivity. PS-PDEAM shrinks when the temperature exceeds its lower critical temperature (LCST). When AP molecules pass through the modified interface, the electron transfer rate is accelerated, and the sensor is turned on. In the off state, the electrochemical response of AP cannot be detected. Under ideal experimental conditions, for composite modified films, there is a wide detection range of AP between 1.5-85.1 µM and 85.1-235.1 µM, and the limit of detection of acetaminophen is as low as 0.57 µM (S/N = 3). This method has been successfully applied to the determination of AP in tablets, and shows high stability, good reproducibility and excellent anti-interference ability. The on-off sensor opens up a wide range of possibilities for the use of temperature-sensitive polymers in electro-catalysis, sensors, and environmental pollutant monitoring.

An ultrasensitive high-performance baicalin sensor based on C3N4-SWCNTs/reduced graphene oxide/cyclodextrin metal-organic framework nanocomposite.

Baicalin (Bn) obtained from natural plants has been found to exhibit significant antiviral activity against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Herein, a novel ultrasensitive Bn electrochemical sensor was proposed based on graphitized carbon-nitride - single-walled carbon nanotube nanocomposites (C3N4-SWCNTs), reduced graphene oxide (rGO) and electrodeposited cyclodextrin-metal organic framework (CD-MOF). The sensing nanomaterials were characterized by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Under optimal conditions, the sensor exhibited sensitive detection of Bn in a wide linear range of 1 × 10-9-5 × 10-7 M with an LOD of 4.6 × 10-10 M and a sensitivity of 220 A/M, and it showed satisfactory stability and accuracy for detecting Bn in real samples (human serum and bear bile scutellaria eye drops). In addition, the electrochemical reaction sites and redox mechanism of Bn were revealed through electrochemical behavior and density functional theory. This work provided an insightful solution for detecting Bn, and extensive potential applications could be further expected.

A Dual-Channel Fluorescent Nanoprobe for Sequential Detection of ATP and Peroxynitrite to Accurately Distinguish between Normal Cells and Cancer Cells.

Cancer is one of the biggest public enemies of global health with its high morbidity and mortality. Achieving early diagnosis is the most effective means of reducing cancer harm, which requires the use of powerful tools to accurately identify biomarkers. However, most of the reported fluorescent probes for cancer diagnosis can only detect one substance, which makes it difficult to meet the requirements of high accuracy. Here, a fluorescent nanoprobe (CPQ@ZIF-90) for sequential detection of ATP and ONOO- is constructed by encapsulating the ONOO- sensitive unit CPQ within ZIF-90. CPQ@ZIF-90 first reacts with ATP to release CPQ, which greatly enhances the fluorescence at 740 nm. Then, the released CPQ continues to react with ONOO- and is oxidatively cleaved by ONOO- to form a coumarin product with a small π-conjugated structure, which significantly enhances the fluorescence at 510 nm. CPQ@ZIF-90 shows high sensitivity and selectivity for the detection of ATP and then ONOO-. Moreover, CPQ@ZIF-90 has good biocompatibility and successfully realizes the sequential detection of a dual-channel fluorescence change of ATP and ONOO- in living cells and zebrafish and accurately distinguishes normal cells from cancer cells. CPQ@ZIF-90 is expected to be a potential tool for accurate cancer diagnosis through sequential detection of two cancer markers.

Ultrasensitive catechin electrochemical sensor based on uniform ordered mesoporous carbon hollow spheres (MCHSs) advanced carbon-based conductive materials.

Catechin is one of the flavonoids with antioxidant activity and has attracted great interest. A rapid and accurate detection of catechin is of great significance. Herein, an ultrasensitive catechin electrochemical sensor based on uniform ordered mesoporous carbon hollow spheres (MCHSs) advanced carbon-based conductive material modified glass carbon electrode was constructed. The MCHSs were synthesized by pyrolysis using nitrogen protection and template removal methods, and they exhibited excellent electrochemical detection for catechin owing to their high conductivity and uniform and small spheres with a large specific surface area and hollow structure. Under optimal conditions for the detection of catechin, the MCHSs/GCE showed a wider linear range (10 -1400 nM) and lower detection limit (LOD, 2.82 nM, (S/N = 3)). Furthermore, the electrochemical reaction sites and redox mechanisms of catechin were revealed by electrochemical behavior and density flooding theory. Moreover, the sensor we constructed exhibited good accuracy and stability for the detection of catechin in actual sample detections.