Application of colorimetric sensor array coupled with machine-learning approaches for the discrimination of grains based on freshness.

BACKGROUND: Volatile organic compounds (VOCs) in grain fluctuate depending on the degree of grain freshness. A new colorimetric sensor array (CSA) was developed as capture probes for the quantification of VOCs in grains in this work, and it was designed to monitor the variation of grain VOCs. CSA spectral data acquisition using visible-near-infrared spectroscopy and image processing of CSA's image imformation by computer were used comparatively. Then, machine-learning-based models - for example, synergistic interval partial least squares, genetic algorithm, competitive adaptive reweighted sampling (CARS) algorithm, and ant colony optimization (ACO) algorithm - were introduced to optimize variables. Moreover, principal component analysis, and linear discriminant analysis (LDA), and K-nearest neighbors (KNN) were used for the classification. Ultimately, quantitative models for detecting grain freshness are developed using various variable selection strategies. RESULTS: Compared with the pattern recognition results of image processing, visible-near-infrared spectroscopy could better separate the grains with different freshness from principal component analysis, and the prediction set of LDA models could correctly identify 100% of rice, 96.88% of paddy, and 97.9% of soybeans. In addition, compared with CARS and ACO, the LDA model and KNN model based on genetic algorithms show the best prediction performance. The prediction set could correctly identify 100% of rice and paddy samples and 95.83% of soybean samples. CONCLUSION: The method developed could be used for non-destructive detection of grain freshness. © 2023 Society of Chemical Industry.

Electrochemical immunosensor based on self-assembled gold nanorods for label-free and sensitive determination of Staphylococcus aureus.

An electrochemical immunosensor based on self-assembled gold nanorods on glassy carbon electrode was developed for label-free and sensitive detection of Staphylococcus aureus (S. aureus). The gold nanorods were firstly assembled on the electrode surface by using poly-(diallyldimethylammonium chloride) (PDDA) and poly-(styrenesulfonate) (PSS) as the linkers, followed by the functionlization of anti-S. aureus antibodies. The immobilized antibodies on self-assembled gold nanorods could efficiently capture S. aureus to the modified electrode by the specific immune reaction, which clearly blocked the electron transfer of electrochemical probes on the electrode surface due to the resistance of S. aureus. Atomic force microscopy and electrochemical impedance spectroscopy were used to verify the stepwise assembly of the immunosensor fabrication. The immunosensor could detect S. aureus in a linear range from 1.8 × 103 to 1.8 × 107 CFU mL-1 with a low detection limit of 2.4 × 102 CFU mL-1. Furthermore, the designed electrochemical immunosensor was successfully used to determine S. aureus in milk samples with acceptable results. The proposed immunosensor could be further expanded to sensitive detect other pathogens with the addition of specific antibodies.

The value of oral contrast ultrasonography in the diagnosis of gastric cancer in elderly patients.

BACKGROUND: This study aims to investigate the value of oral contrast ultrasonography (OCUS) in the diagnosis of gastric cancer in elderly patients. METHODS: OCUS data obtained from patients ≥ 60 years old were retrospectively analyzed and compared with gastroscopy results. RESULTS: Among the 12,716 subjects examined by OCUS, 5021 subjects were ≥ 60 years old, which accounted for 39.48% (5021/12,716). Gastritis, gastric polyp, benign ulcer, and gastric cancer were detected by OCUS in 1099 patients. Among them, 196 patients underwent gastroscopy. Furthermore, ulcerative lesions were detected in 32 patients by OCUS and in 51 patients by gastroscopy, and the coincidence rate was 62.74%. Among these patients, gastric cancer was diagnosed in 18 patients by OCUS with a detection rate of 1.64% (18/1099) and detected in 19 patients by gastroscopy with a diagnostic coincidence rate of 94.73% (18/19). Furthermore, benign ulcer was detected in 14 patients by OCUS and in 32 patients by gastroscopy, and the diagnostic coincidence rate was 43.75% (14/32). CONCLUSION: OCUS helps to timely detect senile gastric cancer and can be used as a suitable technique for the detection of gastric diseases.

[Clinical value of contrast-enhanced ultrasonography in the diagnosis of prostate cancer in patients with different PSA concentrations].

OBJECTIVE: To investigate the clinical value of contrast-enhanced ultrasonography (CEUS) in the diagnosis of prostate cancer in patients with different concentrations of prostate-specific antigen (PSA). METHODS: Based on the PSA concentration, 186 patients were divided into three groups (PSA 4－10 µg/L, 11－20 µg/L, and >20 µg/L) and underwent transrectal CEUS and biopsy. We compared the pathological results with the CEUS features in different groups of patients and performed a statistical analysis on the characteristics of the CEUS manifestations of prostate cancer and benign prostatic lesions. RESULTS: Of the 186 patients, 118 (63.4%) were diagnosed by biopsy with prostate cancer and the other 68 (36.6%) with benign prostatic lesions. The positive rate of CEUS in the diagnosis of prostate cancer was above 95% in all the three groups, significantly higher than that of conventional ultrasound in the PSA 4－10 and >10－20 µg/L groups (P <0.01). CONCLUSIONS: Contrast-enhanced ultrasonography can achieve a high detection rate in the diagnosis of prostate cancer, especially for the patients with a low PSA concentration, and therefore can be used as one of the most valuable diagnostic techniques for this purpose.

Development of tyrosinase biosensor based on quantum dots/chitosan nanocomposite for detection of phenolic compounds.

A sensitive and simple amperometric biosensor for phenols was developed based on the immobilization of tyrosinase into CdS quantum dots/chitosan nanocomposite matrix. The nanocomposite film with porous nanostructure, excellent hydrophilicity and biocompatibility resulted in high enzyme loading, and the tyrosinase (Tyr) immobilized in this novel matrix retained its activity to a large extent. The CdS quantum dots/chitosan nanocomposite film was characterized by scanning electron microscopy and electrochemical impedance spectroscopy, and the parameters of the various experimental variables for the biosensor were optimized. Under the optimal conditions, the designed biosensor displayed a wide linear response to catechol over a concentration range of 1.0×10(-9) to 2.0×10(-5)M with a high sensitivity of 561±9.7mAM(-1) and a low detection limit down to 0.3 nM at a signal-to-noise ratio of 3. The CdS quantum dots/chitosan nanocomposites could provide a novel matrix for enzyme immobilization to promote the development of biosensing and biocatalysis.

Graphene quantum dots enhanced electrochemiluminescence of cadmium sulfide nanocrystals for ultrasensitive determination of pentachlorophenol.

An ultrasensitive electrochemiluminescence (ECL) sensor based on the ECL amplifying behavior of the graphene quantum dots-CdS nanocrystals (GQDs-CdS NCs) was constructed for the detection of pentachlorophenol (PCP). Because of the presence of doped GQDs, the resulting GQDs-CdS NCs exhibited 5-fold enhanced ECL intensity than pure CdS NCs with the ECL onset potential positively shifted by 80 mV. Furthermore, based on the effective inhibition of the ECL response of GQDs-CdS NCs film by PCP, a simple method for ultrasensitive determination of PCP was devised, which showed a wide linear range of 0.01-500 ng mL(-1) and a low detection limit of 3 pg mL(-1) (S/N = 3) with good stability, reproducibility and applicability for PCP detection in real water samples. Thus, it can be expected that GQDs-based composites with excellent performance may play a more important role in pesticide determination.

A visible light photoelectrochemical biosensor coupling enzyme-inhibition for organophosphates monitoring based on a dual-functional Cd(0.5)Zn(0.5)S-reduced graphene oxide nanocomposite.

A novel visible light photoelectrochemical (PEC) platform coupled with enzyme-inhibition for rapid and sensitive determination of organophosphates (OPs) was constructed based on a dual-functional Cd0.5Zn0.5S-reduced graphene oxide (Cd0.5Zn0.5S-rGO) nanocomposite. Due to the inherent biocompatibility of the Cd0.5Zn0.5S-rGO nanocomposite, acetylcholinesterase (AChE) immobilized on the Cd0.5Zn0.5S-rGO modified electrode can hydrolyze acetylthiocholine chloride into thiocholine, which could increase the photocurrent of the enzyme electrode, and the further inhibition of OPs on the enzyme electrode could decrease the photocurrent response. Based on the notable change in the PEC response of the AChE-Cd0.5Zn0.5S-rGO modified electrode and using Dursban as a model, a simple and effective way for PEC monitoring of OPs is proposed, which showed a wide linear range of 0.001-1 µg mL(-1) with a low detection limit of 0.3 ng mL(-1) (S/N = 3). Moreover, the biosensor was successfully challenged with water samples, demonstrating a new method for rapid and sensitive screening/evaluating exposure to organophosphorus pesticides and other hazardous substances.

Clinical value of ultrasound-guided full-needle path anesthesia in transperineal prostate biopsy: An observational study.

BACKGROUND: The pain sensation in a transperineal prostate biopsy was obvious. This study explored the clinical value of ultrasound-guided full-needle path anesthesia in transperineal prostate biopsy. METHODS: Two hundred patients who underwent ultrasound-guided transperineal prostate biopsy at our department were randomly divided into 2 groups. The control group received routine local infiltration anesthesia, and the experimental group received ultrasound-guided full-needle path anesthesia. Immediately after biopsy, visual analog scoring was used to evaluate pain during the biopsy process. Seven days postbiopsy, telephone follow-up revealed symptoms, such as hematuria and discomfort during urination. The measured data were expressed as x ±â€…s. The 2 groups were compared using the t test, and the differences were statistically significant (P < .05). RESULTS: There were no significant differences in age, prostate-specific antigen (PSA) level, or prostate volume between the 2 groups, and all patients underwent prostate biopsy. The pain score of visual analog score was (2.55 ±â€…0.88), urination discomfort was (1.86 ±â€…0.67) days and hematuria time was (2.87 ±â€…0.91) days in the experimental group after biopsy. In the control group, the pain score of visual analog scale was (4.32 ±â€…0.94), the urination discomfort was (2.3 ±â€…0.77) days, and the hematuria time was (2.85 ±â€…0.83) days. Pain scores and urination discomfort were compared between the 2 groups (P < .01). Pain and urination discomfort associated with prostate biopsy in the experimental group were significantly lower than those in the control group. CONCLUSION: Ultrasound-guided full needle path anesthesia can alleviate pain sensation in patients undergoing transperineal prostate biopsy and has high clinical value.

Dual function of magnetic nanocomposites-based SERS lateral flow strip for simultaneous detection of aflatoxin B1 and zearalenone.

Aflatoxin B1 (AFB1) and zearalenone (ZEN) are two mycotoxins that often co-occur in corn. A surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-LFIA) that can simultaneously detect AFB1 and ZEN in corn samples was developed employing the core-interlayer-satellite magnetic nanocomposites (Fe3O4@PEI/AuMBA@AgMBA) as dual-functional SERS tags. Under the optimal conditions, the detection ranges of AFB1 and ZEN in corn samples were 0.1-10 µg/kg and 4-400 µg/kg, respectively. Moreover, the test results for two mycotoxins in contaminated corn samples employing the suggested SERS-LFIA was in line with those of the HPLC technique. In view of its satisfactory sensitivity, accuracy, precision and short testing time (20 min), the developed system has a promising application prospect in the on-site simultaneous detection of AFB1 and ZEN.

Air and argon cold plasma effects on lipolytic enzymes inactivation, physicochemical properties and volatile profiles of lightly-milled rice.

This study investigated the effectiveness of cold-plasma treatment using air and argon as input gas on deactivation of lipolytic enzymes in lightly-milled-rice (LMR). The results showed no significant inactivation in lipase and lipoxygenase using air-plasma. However, using argon as input gas, the residual activities of lipase and lipoxygenase were reduced to 64.51 % and 29.15 % of initial levels, respectively. Argon plasma treatment resulted in more substantial augmentation in peak and breakdown viscosities of LMR starch, suggesting an enhancement in palatability of cooked LMR with increased stickiness and decreased hardness. In contrast to the decrease in volatile compounds in LMR following argon plasma treatment, the concentrations of several prevalent aroma compounds, including 1-hexanol, 1-hexanal, and 2-pentylfuran, exhibited significant increments, reaching 1489.70 ng/g, 3312.10 ng/g, and 58.80 ng/g, respectively. These findings suggest the potential for enhancing various facets of the commercial qualities of LMR by utilizing different input gases during plasma treatment.

[Simplification of NIR model for citrus's sugar content based on sensory methods].

The prediction of sugar content (SC) in citrus by near-infrared spectroscopy (NIRS) and sensory test was investigated the validation whether the result of non-destructive determination methods by NIRS can meet the request of consumers' sensory or not, and the simplification of the prediction model of NIRS for citrus's SC with variables selection on the basis of meeting their demands. Result of the latter analyzed by one-way ANOVA shows that there was a significant difference influenced by individual diversity, but not by gender. After excluding the sensuous outliers, root mean standard error of deviation (RMSED) of every participator was calculated and the minimum equaled to 0.633, which was chosen as borderline of NIR model's RMSEP to meet the sensory request Then, combined with spectral preprocessing and variables selection methods, SPA-MLR model was obtained by its robustness with Rp = 0.86, as well as RMSEP = 0.567 for prediction set, furthermore, prediction time just costs 6.8 ms. The achievement that not only meets the customers' sensory, but also simplifies the prediction model can be a good reference for real time application in future.

Bisphenol A detection based on nano gold-doped molecular imprinting electrochemical sensor with enhanced sensitivity.

A facile electrochemical sensor based on nano gold-doped molecularly imprinted polymer (MIP) was proposed to realize the selective detection of bisphenol A (BPA) with enhanced sensitivity. Initially, gold-doped MIP (Au@MIP) film was constructed by electropolymerizing p-aminobenzoic acid (PABA) and BPA with in situ gold reduction to distribute gold nanoparticles nearby the imprinted cavities. Subsequently, the template molecules were further extracted from the polymer film, then the MIP could rebind with the template molecules to achieve specific detection of BPA. The nano gold-doped MIP increased the effective surface area and promoted conductivity when BPA was oxidized in the imprinted cavities, which improved the determination sensitivity. Under optimal conditions, the prepared sensor displayed a linear range from 0.5 to 100 µM for BPA detection with a detection limit of 52 nM. The designed sensor was further used to detect BPA in food samples, obtaining satisfactory recoveries from 96.7% to 107.6%.

Research on the correlation between three-dimensional morphology and temperature changes in potato slices during drying.

Drying is an effective method to reduce potato storage loss. However, potatoes have high porosity with high water content. Shrinkage during drying can lead to folding and cracking of the dried product form. Therefore, this study explored the correlation between the 3D morphology and temperature distribution changes of potato slices during drying, with the aim of providing a reference for the detection of quality changes. An online automatic acquisition device to obtain 3D morphology and temperature information was designed and built. Hot air-drying experiments were conducted on the potato slices. 3D morphology images and temperature images of the potato slices were acquired by 3D and temperature sensors, and the two images were registered using the random sample consensus (RANSAC) algorithm. The region of interest of each image was extracted by algorithms such as threshold segmentation, hole filling and morphological erosion, and the 3D morphology information and temperature information were obtained. The mapping, range and average of each acquisition point were calculated for correlation analysis. Spearman's rank correlation coefficients and Maximum Information Coefficient (MIC) values were selected as measures for the correlation study. The results showed that the Spearman's rank correlation coefficients between average height and average temperature were mostly above 0.7 in absolute value, and the MICs were mostly above 0.9. The average values of the 3D information and temperature information exhibited an extremely strong correlation. This paper gives a new approach to investigate the morphological changes in the drying process by quantifying the relationship between 3D morphology and temperature distribution. This can guide the improvement of potato drying and processing methods.

Custom-Developed Reflection-Transmission Integrated Vision System for Rapid Detection of Huanglongbing Based on the Features of Blotchy Mottled Texture and Starch Accumulation in Leaves.

Huanglongbing (HLB) is a highly contagious and devastating citrus disease that causes huge economic losses to the citrus industry. Because it cannot be cured, timely detection of the HLB infection status of plants and removal of diseased trees are effective ways to reduce losses. However, complex HLB symptoms, such as single HLB-symptomatic or zinc deficiency + HLB-positive, cannot be identified by a single reflection imaging method at present. In this study, a vision system with an integrated reflection-transmission image acquisition module, human-computer interaction module, and power supply module was developed for rapid HLB detection in the field. In reflection imaging mode, 660 nm polarized light was used as the illumination source to enhance the contrast of the HLB symptoms in the images based on the differences in the absorption of narrow-band light by the components within the leaves. In transmission imaging mode, polarization images were obtained in four directions, and the polarization angle images were calculated using the Stokes vector to detect the optical activity of starch. A step-by-step classification model with four steps was used for the identification of six classes of samples (healthy, HLB-symptomatic, zinc deficiency, zinc deficiency + HLB-positive, magnesium deficiency, and boron deficiency). The results showed that the model had an accuracy of 96.92% for the full category of samples and 98.08% for the identification of multiple types of HLB (HLB-symptomatic and zinc deficiency + HLB-positive). In addition, the classification model had good recognition of zinc deficiency and zinc deficiency + HLB-positive samples, at 92.86%.

Dual-layers Raman reporter-tagged Au@Ag combined with core-satellite assemblies for SERS detection of Zearalenone.

Zearalenone (ZEN) is a prevalent mycotoxin identified in corn. A SERS-based immunosensor by constructing core-satellite assemblies was developed for ZEN detection. ZEN monoclonal antibody modified gold nanostars (AuNSs) were fabricated as the capture probe (core). The Raman signal probes (satellites) utilized ZEN antigen linked to the core-shell structures loaded with two layers of Raman reporter molecules (AuMBA@AgMBANPs). The coupling between AuNSs and AuMBA@AgMBANPs can produce a poweful electromagnetic field, thus considerably amplifying the Raman signal. The detection range of ZEN for corn samples under the optimal conditions was 5 âˆ¼ 400 µg/kg with a LOD of 3 µg/kg, which completely satisfying the requirement of maximum residual level (60 µg/kg). Moreover, the proposed SERS method was consistent with the HPLC-FLD method for the detection of ZEN in naturally contaminated corn samples (90.58% ∼ 105.29%). Conclusively, fabricated immunosensor with exceptional sensitivity and specificity broaden the application of SERS in mycotoxin detection.

Development of a Sensitive SERS Method for Label-Free Detection of Hexavalent Chromium in Tea Using Carbimazole Redox Reaction.

Tea plants absorb chromium-contaminated soil and water and accumulate in tea leaves. Hexavalent chromium (Cr6+) is a very toxic heavy metal; excessive intake of tea containing Cr6+ can cause serious harm to human health. A reliable and sensitive surface-enhanced Raman spectroscopy (SERS) method was developed using Au@Ag nanoparticles as an enhanced substrate for the determination of Cr6+ in tea. The Au@AgNPs coated with carbimazole showed a highly selective reaction to Cr6+ in tea samples through a redox reaction between Cr6+ and carbimazole. The Cr6+ in the contaminated tea sample reacted with methimazole-the hydrolysate of carbimazole-to form disulfide, which led to the decrease in the Raman intensity of the peak at 595 cm-1. The logarithm of the concentration of Cr6+ has a linear relationship with the Raman intensity at the characteristic peak and showed a limit of detection of 0.945 mg/kg for the tea sample. The carbimazole functionalized Au@AgNPs showed high selectivity in analyzing Cr6+ in tea samples, even in the presence of other metal ions. The SERS detection technique established in this study also showed comparable results with the standard ICP-MS method, indicating the applicability of the established technique in practical applications.

Spoilage Monitoring and Early Warning for Apples in Storage Using Gas Sensors and Chemometrics.

In the process of storage and cold chain logistics, apples are prone to physical bumps or microbial infection, which easily leads to spoilage in the micro-environment, resulting in widespread infection and serious post-harvest economic losses. Thus, development of methods for monitoring apple spoilage and providing early warning of spoilage has become the focus for post-harvest loss reduction. Thus, in this study, a spoilage monitoring and early warning system was developed by measuring volatile component production during apple spoilage combined with chemometric analysis. An apple spoilage monitoring prototype was designed to include a gas monitoring array capable of measuring volatile organic compounds, such as CO2, O2 and C2H4, integrated with the temperature and humidity sensor. The sensor information from a simulated apple warehouse was obtained by the prototype, and a multi-factor fusion early warning model of apple spoilage was established based on various modeling methods. Simulated annealing-partial least squares (SA-PLS) was the optimal model with the correlation coefficient of prediction set (Rp) and root mean square error of prediction (RMSEP) of 0.936 and 0.828, respectively. The real-time evaluation of the spoilage was successfully obtained by loading an optimal monitoring and warning model into the microcontroller. An apple remote monitoring and early warning platform was built to visualize the apple warehouse's sensors data and spoilage level. The results demonstrated that the prototype based on characteristic gas sensor array could effectively monitor and warn apple spoilage.

Detection of wheat toxigenic Aspergillus flavus based on nano-composite colorimetric sensing technology.

Volatile organic compounds (VOCs) are an important indicator for fungal-infected wheat identification. This work proposes a novel approach for toxigenic Aspergillus flavus infected wheat identification through characteristic VOCs analyzed by nano-composite colorimetric sensors. Nanoparticles of poly styrene-co-acrylic acid (PSA), porous silica nanoparticles (PSN), and metal-organic framework (MOF) were combined with boron dipyrromethene (BODIPY) to fabricate nano-composite colorimetric sensors. The combination mechanisms for nanoparticles and the information extracted from nano-colorimetric sensors by digital images were analyzed in the current work. Furthermore, linear discriminant analysis (LDA) and k-nearest neighbor (KNN) were used comparatively to analyze the data from images, and toxigenic Aspergillus flavus infected wheat samples could be 100.00% correctly identified when using the optimal KNN model. This research contributes to the practical analysis of VOCs and the detection of toxigenic Aspergillus flavus infected wheat.

Three-Dimensional Appearance and Physicochemical Properties of Pleurotus eryngii under Different Drying Methods.

This study investigated the effects of different drying methods on the drying characteristics, three-dimensional (3D) appearance, color, total polysaccharide content (TPC), antioxidant activity, and microstructure of Pleurotus eryngii slices. The drying methods included hot air drying (HAD), infrared drying (ID), and microwave drying (MD). The results showed that the drying method and conditions significantly influenced the drying time, with MD having a significant advantage in reducing the drying time. The 3D appearance of P. eryngii slices was evaluated based on shrinkage and roughness as quantitative indexes, and the best appearance was obtained by hot air drying at 55 and 65 °C. HAD and ID at lower drying temperatures obtained better color, TPC, and antioxidant activity, but MD significantly damaged the color and nutritional quality of P. eryngii. The microstructure of dried P. eryngii slices was observed using scanning electron microscopy, and the results showed that drying methods and conditions had an obvious effect on the microstructure of P. eryngii slices. Scattered mycelia were clearly observed in P. eryngii samples dried by HAD and ID at lower drying temperatures, while high drying temperatures led to the cross-linking and aggregation of mycelia. This study offers scientific and technical support for choosing appropriate drying methods to achieve a desirable appearance and quality of dried P. eryngii.

Electrochemical Self-Assembled Gold Nanoparticle SERS Substrate Coupled with Diazotization for Sensitive Detection of Nitrite.

The accurate determination of nitrite in food samples is of great significance for ensuring people's health and safety. Herein, a rapid and low-cost detection method was developed for highly sensitive and selective detection of nitrite based on a surface-enhanced Raman scattering (SERS) sensor combined with electrochemical technology and diazo reaction. In this work, a gold nanoparticle (AuNP)/indium tin oxide (ITO) chip as a superior SERS substrate was obtained by electrochemical self-assembled AuNPs on ITO with the advantages of good uniformity, high reproducibility, and long-time stability. The azo compounds generated from the diazotization-coupling reaction between nitrite, 4-aminothiophenol (4-ATP), and N-(1-naphthyl) ethylenediamine dihydrochloride (NED) in acid condition were further assembled on the surface of AuNP/ITO. The detection of nitrite was realized using a portable Raman spectrometer based on the significant SERS enhancement of azo compounds assembled on the AuNP/ITO chip. Many experimental conditions were optimized such as the time of electrochemical self-assembly and the concentration of HAuCl4. Under the optimal conditions, the designed SERS sensor could detect nitride in a large linear range from 1.0 × 10-6 to 1.0 × 10-3 mol L-1 with a low limit of detection of 0.33 µmol L-1. Additionally, nitrite in real samples was further analyzed with a recovery of 95.1-109.7%. Therefore, the proposed SERS method has shown potential application in the detection of nitrite in complex food samples.