Fingerprinting Green Curry: An Electrochemical Approach to Food Quality Control

Quality evaluation of Keteling capsules based on fingerprinting, multicomponent quantification, and quantitative prediction

The Keteling capsule (KC) is a traditional Chinese medicine (TCM) made from the dried extract of Ficus microphylla and an appropriate amount of chlorpheniramine maleate. It is widely used to treat cough and relieve asthma. Despite its extensive usage, a rapid and comprehensive quality evaluation strategy for KC remains a challenge. This study introduces an electrochemical fingerprint analysis technique, in addition to the commonly employed HPLC fingerprints, for efficient and convenient quality evaluation. Moreover, a cost-effective, rapid, and accurate multi-component quantification technique known as the "Multi-markers assay by the monolinear method (MAML)" and the "FT-IR quantitative model" were explored. The HPLC fingerprints were evaluated using a systematically quantified fingerprint method, while the electrochemical fingerprints, based on the Belousov-Zhabotinsky oscillation reaction principle, were effectively analyzed and characterized using oxidation induction times and oscillation lifetimes. Multi-component quantitative analysis was carried out through the MAML and FT-IR quantitative models. The HPLC fingerprint successfully classified the 22 samples into eight grades with excellent discrimination. Active ingredient content analysis was achieved using reliable parameters obtained from electrochemical fingerprinting. The no significant difference in the quantitative results proves the accuracy of the MAML method. Additionally, successful FT-IR quantitative prediction models were developed for chlorogenic acid, isovitexin, and chlorpheniramine maleate. This study offers a dependable and effective approach for enhancing the quality control of KC, and it can provide new insights for improving the quality analysis methods in the field of TCM.

Poly-adenine-mediated tetrahedral DNA nanostructure with multiple target-recognition sites for ultrasensitive and rapid electrochemical detection of Aflatoxin B1

Tetrahedral DNA nanostructures (TDNs) are widely used in the development of electrochemical biosensors due to their structural stability, programmability, and strong interfacial orderliness. However, the complex modifications on the electrode and the single vertex target recognition of the TDNs limit their applications in electrochemical biosensing. Herein, we developed a universal detection system based on a novel polyadenine-based tetrahedral DNA nanostructure (ATDN) using Aflatoxin B1 (AFB1) as the model target for analysis. In the absence of target AFB1, the signal probes (SP) modified with ferrocene would be anchored by five aptamers on ATDN. The target capture by aptamers led to a release of SP from the electrode surface, resulting in a significant reduction of the electrochemical signal. This new nanostructure was not only dispensed with multi-step electrode modifications and strong mechanical rigidity but also had five modification sites which enhanced the detection sensitivity for the target. As a result, this biosensor shows good analytical performance in the linear range of 1 fg mL-1 to 1 ng mL-1, exhibiting a low detection limit of 0.33 fg mL-1. Satisfactory accuracy has also been demonstrated through good recoveries (95.2%-98.9%). The proposed new tetrahedral DNA nanostructure can provide a more rapid and sensitive alternative to previous electrochemical sensors based on the conventional TDN. Since DNA sequences can be designed flexibly, the sensing platform in this strategy can be extended to detect various targets in different fields.

A wearable electrode based on copper nanoparticles for rapid determination of paraquat

The application of copper-based nanoparticles synthesized via green synthesis and their integration with a wearable electrode is reported for designing a flexible catalytic electrode on a glove for onsite electroanalysis of paraquat. A copper precursor and an orange extract from Citrus reticulata are used to synthesize an economical electrocatalytic material for supporting the selective and sensitive detection of paraquat. The electrode yields multidimensional fingerprints due to two redox couples in a square wave voltammogram, corresponding to the presence of paraquat. The developed lab-on-a-finger sensor provides the fast electroanalysis of paraquat within 10 s, covering a wide range from 0.50 to 1000 µM, with a low detection limit down to 0.31 µM and high selectivity. It is also possible to use this sensor at a fast scan rate as high as 6 V s-1 (< 0.5 s for a scan). This wearable glove sensor allows the user to directly touch and analyze samples, such as surfaces of vegetables and fruits, to screen the contamination. It is envisioned that these glove-embedded sensors can be applied to the on-site analysis of food contamination and environments.

Electrochemical-based quantitative fingerprint evaluation strategy combined with multi-markers assay by monolinear method for quality control of herbal medicine

BACKGROUND

Improving the quality control (QC) criterion of herbal medicine (HM) is an ongoing challenge. A rapid and convenient electrochemical analysis technique is now emerging as a promising application for HM QC. So far, extraction and analysis of the overall electroactive components is a key issue need to be solved to improve its application in integral HM QC.

PURPOSE

In this work, using compound liquorice tablets (CLQTs) as an example, we like to put forward a more reliable and accurate quantification method of multi-components for the precise QC of HM. Furthermore, we propose an electrochemical fingerprint-based data mining, extract and synthesis strategy for in-depth and comprehensive QC of HM, qualitatively and quantitatively.

METHODS AND DESIGN

Firstly, the electrochemical quantitative fingerprint of 54 batches of CLQTs from nine manufacturers were developed using B-Z oscillatory system. Secondly, eight characteristic parameters were recorded and compared among samples using intuitive information and PCA. Then, t_und was used to establish the correlation with sample dosage for determination of the relative content of overall electroactive components (Rc). The quantitative determination of five quality markers (Q-markers) were also performed using the novel method, called multi-markers assay by monolinear method (MAML). Finally, after using area integral calculus for electrochemical fingerprint, average linear quantitative fingerprint method (ALQFM) was successfully proposed to extract all latent characteristics for integral quality evaluation of samples.

RESULTS

The t_und and dosage showed a good correlation, by which the obtained Rc displayed different fluctuation among nine manufacturers. Moreover, the contents of five Q-markers obtained by MAML displayed no significant difference with the traditional quantification method. Samples evaluated by ALQFM manifested the integral information and were divided into eight quality grades. The deduced results of correlation between P_l with P_5C, Rc and P_A were more persuasive for demonstrating the reliability and integrity of ALQFM in quality evaluation of HM electrochemical fingerprint.

CONCLUSION

The study confirmed the idea that quantification of Q-markers combined electrochemical-based quality evaluation strategy could be used as a reliable method for HM QC qualitatively and quantitatively from point (precise) to face (integral).

Water Quality Carbon Nanotube-Based Sensors Technological Barriers and Late Research Trends: A Bibliometric Analysis

Water is the key element that defines and individualizes our planet. Relative to body weight, water represents 70% or more for the majority of all species on Earth. Taking care of water as a whole is equivalent with taking care of the entire biodiversity or the whole of humanity itself. Water quality is becoming an increasingly important component of terrestrial life, hence intensive work is being conducted to develop sensors for detecting contaminants and assessing water quality and characteristics. Our bibliometric analysis is focused on water quality sensors based on carbon nanotubes and highlights the most important objectives and achievements of researchers in recent years. Due to important measurement characteristics such as sensitivity and selectivity, or low detection limit and linearity, up to the ability to measure water properties, including detection of heavy metal content or the presence of persistent organic compounds, carbon nanotube (CNT) sensors, taking advantage of available nanotechnologies, are becoming increasingly attractive. The conducted bibliometric analysis creates a visual, more efficient keystones mapping. CNT sensors can be integrated into an inexpensive real-time monitoring data acquisition system as an alternative for classical expensive and time-consuming offline water quality monitoring. The conducted bibliometric analysis reveals all connections and maps all the results in this water quality CNT sensors research field and gives a perspective on the approached methods on this specific type of sensor. Finally, challenges related to integration of other trends that have been used and proven to be valuable in the field of other sensor types and capable to contribute to the development (and outlook) for future new configurations that will undoubtedly emerge are presented.

Recent progress of personal glucose meters integrated methods in food safety hazards detection

Development of personal glucose meters (PGMs) for blood glucose monitoring and management by the diabetic patients has been a long history since its first invention in 1968 and commercial application in 1975. The main reasons for its wide acceptance and popularity can be attributed mainly to the easy operation, test-to-result model, low cost, and small volume of sample required for blood glucose concentration test. During past decades, advances in analytical techniques have repurposed the use of PGMs into a general point-of-care testing platform for a variety of non-glucose targets, especially the food hazards. In this review, we summarized the recent published research using PGMs to detect the food safety hazards of mycotoxins, illegal additives, pathogen bacteria, and pesticide and veterinary drug residues detection with PGMs. The progress on PGM-based detection achieved in food safety have been carefully compared and analyzed. Furthermore, the current bottlenecks and challenges for practical applications of PGM for hazards detection in food safety have also been proposed.

A Novel Electrochemical Nanosensor for the Simultaneous Sensing of Two Toxic Food Dyes

This work reports for the first time the preparation and performance of a nanosensor for the simultaneous detection of metanil yellow and fast green, which are toxic food dyes. For the development of this sensitive platform, the surface of a glassy carbon electrode (GCE) was modified with calixarene and gold nanoparticles. The sensing ability of the designed nanosensor (calix8/Au NPs/GCE) was tested by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The influence of a number of parameters was investigated for optimizing the conditions to achieve the best response of the target analytes. Due to the synergistic activity of calix[8]arene and Au nanoparticles, the calix8/Au NPs/GCE nanocomposite was found to significantly enhance the signals of the selected food dyes in comparison to bare GCE. Under optimized conditions, limits of detection for metanil yellow and fast green were found to be 9.8 and 19.7 nM, respectively, at the calix8/Au NPs/GCE. The designed sensing platform also demonstrated figures of merit when applied for the sensing of food dyes in real water and juice samples. Moreover, high percent recovery, reproducibility, and stability suggested applicability of the designed electrochemical platform for real sample analysis.

Microfluidic Mixer with Automated Electrode Switching for Sensing Applications

An electronic tongue (e-tongue) is a multisensory system usually applied to complex liquid media that uses computational/statistical tools to group information generated by sensing units into recognition patterns, which allow the identification/distinction of samples. Different types of e-tongues have been previously reported, including microfluidic devices. In this context, the integration of passive mixers inside microchannels is of great interest for the study of suppression/enhancement of sensorial/chemical effects in the pharmaceutical, food, and beverage industries. In this study, we present developments using a stereolithography technique to fabricate microfluidic devices using 3D-printed molds for elastomers exploring the staggered herringbone passive mixer geometry. The fabricated devices (microchannels plus mixer) are then integrated into an e-tongue system composed of four sensing units assembled on a single printed circuit board (PCB). Gold-plated electrodes are designed as an integral part of the PCB electronic circuitry for a highly automated platform by enabling faster analysis and increasing the potential for future use in commercial applications. Following previous work, the e-tongue sensing units are built functionalizing gold electrodes with layer-by-layer (LbL) films. Our results show that the system is capable of (i) covering basic tastes below the human gustative perception and (ii) distinguishing different suppression effects coming from the mixture of both strong and weak electrolytes. This setup allows for triplicate measurements in 12 electrodes, which represents four complete sensing units, by automatically switching all electrodes without any physical interaction with the sensor. The result is a fast and reliable data acquisition system, which comprises a suitable solution for monitoring, sequential measurements, and database formation, being less susceptible to human errors.