Review
Recent advances in the detection of contaminants by portable glucose meter in food samples
2023 年 29 巻 1 号 p. 1-14
詳細
2023 年 29 巻 1 号 p. 1-14
Portable glucose meter (PGM) has played vital roles in the field of medicine, with advantages of accurate and quantitative results, portability, easy operation, and low cost. Recently, more and more researchers have extended the application of PGM in detecting foods contaminations. In this paper, a review of the application of PGM based on target recognition elements, such as antibody–antigen reaction, molecularly imprinted polymer, nucleic acid hybridization, enzyme recognition, and click chemistry, and amplification strategies in food safety and contaminant analysis are described in detail. The future development of the application of glucose meters in food safety supervision is also discussed.
Unsafe food causes various illnesses and even death that seriously threatens people's health (Ghanbari and Moradi, 2016). Food contamination, usually characterized by carcinogenesis, micro-toxicity, refractory degradation, and bioaccumulation, is one of the main food safety issues (Gao et al., 2020; Tarannum et al., 2020). The common food contaminants include agricultural pesticides (Chang et al., 2016), veterinary drugs (Tao et al., 2020), toxins (Eivazzadeh-Keihan et al., 2016), heavy metals (Wang et al., 2019), and so on.
There are several traditional methods to detect and monitor ultra-low concentrations of contaminations in foods, such as gas chromatography (GC) (Noij and Kooi, 2015), gas chromatography-mass spectrometry (GC-MS) (Akdoan and Gursoy, 2020; Albero et al., 2020), liquid chromatography (LC) (Legrae et al., 2019), liquid chromatography-mass spectrometry (LC-MS) (Masiá et al., 2016), enzyme linked immunosorbent assay (ELISA) (Fadlalla et al., 2020; Luo et al., 2020), and other novel technologies, such as electrochemical biosensors based on new nanomaterials or new recognition elements (Gupta et al., 2021; Huang et al., 2020). Although these new technologies have shown advantages such as high sensitivity and accuracy in food safety testing, most of the proposed methods are overpriced and need expensive equipment, complicated pretreatment steps, long processing time, and strictly personnel training, which limit its application are unable to be employed as a general screening tool (Guo et al., 2020).
Point of care testing (POCT) is one of efficient detection tools with the characters, such as accurate and quantitative results, no sample preparation, rapid detection speed and user-friendly (Hobbs et al., 2020). Since late 20th century and early 21st century, the concept of POCT was brought to the public (St-Louis, 2000), and was defined as a medical diagnostic test outside clinical laboratory (Zhang et al., 2018). Nowadays, POCT has became one of the most promising technology in medical diagnostics (Liu et al., 2020; Price et al., 2020), food safety detection (Lin et al., 2017; Wei et al., 2018), environmental monitoring (Xu et al., 2020), and public security (Hassan et al., 2020; Scherer et al., 2020), etc. Commonly, POCT systems includes lateral-flow strips by immunoassay (Hu et al., 2017; Yan et al., 2019), microfluidic lab-on-a-chip technologies (Jung et al., 2015), and electrochemical method based on glucose-level test strips (Kim et al., 2020; Zhu et al., 2017). However, most traditional lateral-flow assays suffer from low sensitivity and stability since it is very difficult to eliminate the unspecific binding and ensure the consistency of the flow rate, and only provide a qualitative and semi-quantitative result. Besides, these methods also suffer from shelf-life and relative sensitivity to humidity (Rivas et al., 2014). Microfluidic lab-on-a-chip technology has the unique peculiarity of requiring low amount of sample and fast analysis time, and draws much attention in recent years (Park et al., 2020; Schulz et al., 2020). However, they require complex analyzers and shows defect of userunfriendly, which limit its application in rigorous POCT diagnostic systems (Jung et al., 2015). The portable glucose meter (PGM) is a mature POCT technologies which be used to detect glucose, showing advantages of accurate and quantitative results, portability, low cost, and easy operation, and has played vital roles in the field of medicine (Baldo et al., 2020). Over recent decades more and more researchers have extended the use of PGM to food safety and contaminant detection. To achieve sensitive detection of the targets, many strategies has been explored by researchers, including coupling of target recognition elements with signal transduction and amplification strategies. In this paper, the development of PGM and its application in food analysis and detection were reviewed.
Generally, blood glucose meters have undergone a transition from photoelectric-type meters, which are photons are measured in optical methods, to electrode-type, which are measured in electrochemistry. The first PGM was invented by Anton Clemens in 1968. Compared to current PGM, the first model was bulky and expensive, and critical operation procedure, including sample treatment and time control, was needed to ensure detection precision (Clarke and Foster, 2012; Vashist et al., 2011). In 1981, wiped blood glucose meter was developed with advantages of lightweight and portable, but still suffered from disadvantages of wiping process (Zhang et al., 2018). In 1987, a colorimetry glucose meter was introduced by the Johnson & Johnson Group, and it did not need complex wiping process (Leroux and Desjardins, 1988). At the same time, a new concept of electrode sensing of blood glucose, which used an enzyme electrode strip, caused the wide attentions of researchers. Abbott Laboratories purchased the concept in 1996, and became the world leader in the glucose meters' market (Burritt, 1990). Since then, more and more researchers paid attention on decreasing sample volume and realizing multiple site sample collection.
Up to now, electrode-type blood glucose meter was still the mainstream and have been widely investigated and utilized. Electrode-type glucose sensing includes nonenzymatic sensing and enzymatic biosensing (Chen et al., 2013). Based on direct electrochemistry of glucose via metallic redox centers, nonenzymatic sensing of glucose shows advantages of cost-effective and long-term stability (Hwang et al., 2018). Due to the high electrocatalytic capacity and sensitivity to glucose electrooxidation, noble metals such as Au (Lee et al., 2019) and Pt (Song et al., 2018) are widely used in nonenzymatic glucose sensing. However, poor selectivity has limited the wide applications of nonenzymatic glucose sensing since some endogenous substance could be oxidized via glucose oxidation pathway, and further weakening the activity of noble metal electrodes (Chen et al., 2013). Recently, non-enzymatic glucose sensors were innovatived by nanotechnology. Many nanostructured materials (Hyeong et al., 2020; Wang et al., 2020) with advanced characteristics were reported to be applied in non-enzymatic glucose sensors, which suggest new chances and inspirations to electrochemical non-enzymatic glucose meter. The enzymatic biosensing of glucose shows advantages of high selectivity and sensitivity, since possible interferences has no effect on the transformation of the enzymatic recognition events of glucose to amperometric signal. Glucose oxidase (GOx) and glucose dehydrogenase (GDH) are the most commonly used enzymes in this technology (Vashist et al., 2011). GOx is highly selective towards glucose molecules, and could be oxidized by oxidizing substances. However, when pH was less than 2 or greater than 8 or when temperatures was higher than 40°C, GOx could quickly lose activity. Compared with GOx-based sensors, GDH-based amperometric biosensors have advantages of relatively higher activity, since the oxygen level in the analyte solution do not affect their performance (Oubrie, 2014).
Though PGM has been widely used in many situations with technical advancement, more attention should be paid on increasing the accuracy of meter values via developing meter and strip technology, controlling environmental factors, and reducing interfering element (Ginsberg, 2009). With the further efforts of researchers, PGM will have better performance in the field of analysis with higher stability, selectivity and sensitivity.
Detection of foodborne pathogenic bacteria Pathogenic bacterial contamination in food is a crucial food safety issue, which can cause great morbidity and mortality (Choi et al., 2018). Common foodborne pathogenic bacteria causing human disease include Staphylococcus aureus (S. aureus), Campylobacter, Salmonella, Listeria monocytogenes, Shigella, and enterohemorrhagic and enteropathogenic strains of Escherichia coli (E. coli) (Adley et al., 2010; Tauxe et al., 2002). Mostly, pathogenic bacterial contamination is connected with raw or undercooked meats or eggs, sometimes they can also be found in prepared foods, dairy products, leafy vegetables, and shellfish (Heredia and García, 2018).
Salmonella is a Gram-negative enterobacterium which can cause serious food poisoning. Joo et al. (2013) developed a novel method for the detection of Salmonella bacteria in milk using PGM (as shown in Fig. 1). In which, Salmonella bacteria in milk sample was captured and separated from mixture by antibody-functionalized magnetic nanoparticle clusters under an external magnetic field. After reacted with polyclonal antibody-functionalized invertase, the complex was transferred to a sucrose solution for catalytic reaction. Finally, the amount of catalysate, glucose, was analyzed by PGM. The result demonstrated the fabricated method could be applied in fast and sensitively detecting Salmonella bacteria in milk with a detection limit of 10 CFU/mL, making PGMs a promising analytical tool in the food safety industry.
Schematic illustration of the experimental procedure for detecting pathogenic bacteria using personal glucose meters.
In Joo's study, polyclonal antibody was directly conjugated with invertase, however, enzymes are sensitive to denaturalization or inactivation by extreme pH and temperature (Datta et al., 2013). Considering the fact that enzymes are susceptible to external factors, silica nanoparticles was used to increase the stability of glucose oxidase in Luo's study (Luo et al., 2017; Wu et al., 2009). In his study, the pathogenic bacteria were captured and enriched by monoclonal antibody-functionalized magnetic nanoparticles, and polyclonal antibodies and glucose oxidase were lorded onto silica nanoparticles to prepare trace tag. When there was bacteria residue, a sandwich-type immunoassay would proceed, then the formed composites were dispersed in glucose solution to perform the catalyzed reaction. Finally, a facile and sensitive method was established by using PGM. The detection limit was as low as 7.2 × 10 CFU/mL for both Salmonella Pullorum and Salmonella Gallinarum.
E. coli, another kind of gram-negative bacteria that also shows great threat to human health. Chavali's group report an application of PGM in detecting E. coli in potable water (Chavali et al., 2014). The method was established based on the principle that glucose is the preferred carbon source to E. coli compared with lactose. Firstly, water sample and glucose were put into a small container with additives (such as LTB or tryptone). Afterwards the glucose test strips were dipped in the sample which was taken as the initial PGM reading. After reacting for 8 h, another PGM reading were obtained. If PGM reading changed a lot, indicating that the water sample is contaminated with high amount of E. coli. Though it showed disadvantages of time-consuming, the developed method showed advantages of easy to operate, low cost, no need of special training and environment-friendly.
Wang et al. (2015) proposed a novel method to determine E. coli based on PGM with glucoamylase, and the protocol was also extended in detecting S. aureus. The proposed method was based on the fact that when pathogenic bacteria was added, electrostatic interactions between glucoamylase and quaternized magnetic nanoparticles would be disrupted, resulting in the release of glucoamylase. Then the glucoamylase was used to catalyze the hydrolysis of amylose to glucose which could be detected by PGM. The established method showed advantages of simplicity, portability, sensitivity (the detection limit was 20 cells/mL).
Immunochromatographic assay, with advantages of convenient operation, simple operation and short analysis time, is one of the traditional POCT methods, and has been widely used in laboratories without precision instruments (Hu et al., 2017). Huang et al. (2018) reports a portable immunochromatographic assay (ICA) conjugated with PGM as readout for E. coli O157:H7 detection (as shown in Fig. 2). Invertase and antibody conjugated with magnetic nanoparticles (MNPs) was used to capture E. coli O157:H7. Then the conjugated compounds was dropped onto sample pad, they will be firstly captured by coating antigen on T line, while the uncombined compounds would continue driving to absorbent pad, which was soaked in sucrose solution before loading onto the backboard. After catalytic reaction was performed for enough time, the absorbent pad was taken off and the reaction solution was squeezed out and detected by PGM. The detection limit of E. coli O157:H7 was 6.2 × 104 CFU/mL by using this method.
chematic illustration of a portable and quantitative immunochromatographic assay (ICA) with a personal glucose meter (PGM) as readout for the detection of Escherichia coli O157:H7.
Antimicrobial peptides are promising biometric probe, since they have high affinity and specificity for bacterial cells. Bai et al. (2020) established a new method to detect E. coli O157:H7 in milk samples by PGM. In the study, copper phosphate nanocomposites was embedded with magainins I and Fe3O4 to prepare capturing probes, and calcium phosphate nanocomplexes were conjugated with cecropin P1 and invertase to prepare signal tags, a sandwich immunocomplex was formed when there was E. coli O157:H7 contamination, and the invertase in the immunocomplex hydrolyzed sucrose to glucose, which could be quantified on PGM to reflect E. coli O157:H7 level. The detection limit was 10 CFU/mL with linear range from 10 to 107 CFU/mL.
Aptamers, which are single-stranded oligonucleotides that could specifically bind with targets, has attracted much attention in recent years (Chang et al., 2016; Pieta et al., 2020). Taking advantages of aptamer, Wan et al. (2016) developed a novel system based on invertase-promoted hydrolysis of sucrose by using PGM for the detection of S. aureus. Limit of detection of the method could reach to 1.0 × 105 CFU/mL with linear relationship ranging from 1.2 × 105 to 1.2 × 108 CFU/mL. With the help of new molecular recognition element, aptamer, the study demonstrated a new approach for bacteria detection with glucose meter. Yang et al. (2021) also developed a novel method for the determination of S. aureus with aptamer based on PGM platform. Aptamer was immobilized onto the surface of magnetic bead by hybridization with the capture probe. When there was S. aureus contamination, the aptamer would separate from magnetic bead, and then the capture probe would be exposed and conjugated with a biotinylated probe, triggering DNA hybridization chain reaction, and realizing amplification of signal. Under these conditions, the detection limit was improved to 2 CFU/mL, which provided an alternative choice for the detection of bacterial pathogens.
Detection of mycotoxin Mycotoxins are secondary metabolites of fungal species, and some species of mycotoxins can trigger serious health hazards, such as cancers, deformity and mutation (Yang et al., 2020), and researchers are working tirelessly to investigate mycotoxins.
Lu's research group (Xiang and Lu, 2012) was on the first try to apply PGM in qualitative and quantitative detection of mycotoxins based on the hybridization reaction between DNA and cDNA. In his study, anti-ochratoxin A(OTA) antibody was modified onto magnetic bead (MBs). OTA was connected with DNA to prepare OTA-DNA conjugate, and based on antigenantibody reaction, then OTA-DNA was loaded onto MBs to further capture cDNA-invertase conjugate which can produce PGM detectable glucose. When there was OTA residues, less DNA-OTA conjugates would conjugate with antibody on the surface of MBs, which would cause less DNA-invertase binding, and finally cause the less production of glucose. The detection limit was 6.8 ng/mL, indicating the fabricated method could be efficient way to determine OTA.
Click chemistry shows advantages of high yielding and inoffensive byproducts, selective and modular process and wide in scopeand, and has been widely used in chemical reactions nowadays (Bevilacqua et al., 2014; Parker and Pratt, 2020). Qiu et al. (2019) established a DNA template-mediated click chemistry-based method to detect Ochratoxin A (OTA) (as shown in Fig. 3). Azido-OTA aptamer-biotin (DNA1) is conjugated with magnetic beads (MBs). By hybridizing with DNA1, alkylnyl-DNA-invertase (DNA2) could combine with MBs, forming a short dsDNA. Based on “click” ligation, generated by the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction between DNA1 and DNA2, great improvement of sensitivity and selectivity for the detection of OTA were realized .
Schematic illustration of a DNA template-mediated click chemistry-based portable signal-on sensor for the detection of ochratoxin A.
Gu et al. (2016) report a new method for the detection of OTA in red wine with PGM. Invertase-labeled competitor DNA, which was partly complementary to the aptamer, was hybridized with OTA-aptamer on the surface of magnetic beads (MBs) to form competitive DNA-aptamer-MB complex. The addition of OTA would trigger the structure-switching of the aptamer to the aptamer-OTA complex, making invertaselabeled competitor DNA release, which could produce detectable glucose solution. Under optimal conditions, the detection limit of OTA could reach to 3.31 µg/L in standard buffer and 3.66 µg/L in samples. Besides, the fabricated aptasensor also showed possibility in detecting aflatoxins B1 and B2. Zhang et al. (2021) developed an aptasensing platform incorporating magnetic beads and a DNAzyme to further increase the sensitivity for detecting OTA with PGM. In this study, biotin-labeled OTA aptamer and biotin-labeled substrate strand were conjugated with magnetic beads to prepare aptamer probes, and substrate cleavage activity could be blocked by the hybridization between DNAzyme strand and aptamer probes. While when there was OTA contamination, OTA would specifically bind with aptamer probe, inducing the hybridization between the DNAzyme strand and substrate strand. Then Zn2+ was added to induce the signal amplification reaction of hydrolysis and cleavage of the substrate chain. With invertase labelled substrate strand, the detection of OTA is successfully transformed into the measurement of glucose by PGM. The platform is shown with a low detection limit of 0.88 pg/mL, and can be used as a potential choice for quantitative analysis of small molecules, at home or under point-of-care settings.
Aflatoxin B1 (AFB1) is another most toxic and carcinogenic mycotoxins and can lead severe liver-related disease in human beings and animals (Lu et al., 2017). Based on DNA walking machine and PGM, Yang et al. (2018) developed a novel aptasensor of AFB1 in bread. In this system, the aptamer DNA were modified onto electrode. With AFB1, the aptamer DNA would leave away from the electrode surface due to the specific binding of AFB1 to the aptamer DNA. Then the walker DNA solution was added, causing the release of short DNA fragment labeled with invertase. Finally, glucose catalyzed by invertase was to be detected by PGM. The minimum detection limit of this method is 10 pM. Meanwhile, the method shows advantages of no need of multiple separation and washing steps, low cost, portability and sensitivity.
Aptamers-gated mesoporous silica nanoparticles (MSNs) as a glucose controlled release nanovessel with PGM readout function has attracted more and more attention. They show merits of controllable, low background, and high glucose loading capability (Fu et al., 2013). Wang et al. (2019) report a novel sensing platform to detect AFB1 in pearl rice, corn and wheat with PGM using a “Dual Gates” locked, target-triggered nanodevice. Through target-triggered glucose (GO) release from aminated magnetic MSMs, “dual gates” aminated magnetic MSMs bearing polydopamine (PDA)-aptamer (Apt) two-tier shells is designed and used to detect AFB1 with low background and high accuracy. When there is AFB1 contamination in the sample, the self-degradation and the specific Apt-target reaction of PDA process, causing the departure of “dual gates” and the opening of pores to release the loaded GO, which could be detected by PGM. Due to the use of controlled GO-release nanocontainers, the platform showed higher sensitivity, reproducibility and stability for the detection of AFB1 than the commercialized ELISA kits, and the detection limit of the proposed method is less than 2 ppb.
AFM1, as the major metabolite of AFB1, has shown great threat to human beings and was reclassified as Group 1 carcinogenic agent recently (Khoury et al., 2011). Giovanni et al. (2019) developed a sensor assay based on nitrocellulose strips to detect low amounts of AFM1 directly in whole milk with PGM. In this study, anti-AFM1 antibody was produced and conjugated to invertase. When there was no toxin in the milk, the antibody-inverse conjugation would conjugate with the strip modified with glutamine-binding protein, causing the production of large amount of PGM detectable glucose. And the detection limit of AFM1 in whole milk was as low as 27 ppt, demonstrating an efficient method for detecting AFM1 sensitively.
Liposomes are formed by dispersing amphipathic molecules in water with spherical bilayer structures. They have various advantages, such as easy preparation, large internal volume, acceptable stability and easy modification with chemical functional groups (Mahmoudi et al., 2020). To increase the versatility of the PGM, Nie et al. (2020) devised a novel strategy, based on grafting functional groups onto liposome surface, to develop the relationship between patulin and glucose generation (as shown in Fig. 4). The approach overcame interference from endogenous glucose and other mycotoxins with a low detection limit of 0.05 ng/mL, and could be applied in the analysis of mycotoxins in wide range of samples.
Schematic illustration of a flexible assay strategy based on sulfhydryl-terminated liposomes combined with personal glucometer.
Detection of pesticide and veterinary drug residues Pesticide and veterinary drug residues have become one focus of widespread concern in the fields of food safety, since largescale agricultural production is performed (Zhou et al., 2018). These drug residues may present great hazards to human health, such as cancer, interruptions of hormone functions and a reduction in the efficiency for treating infection in humans, etc (Xu et al., 2017). Given their toxicity and side effects, many countries have set maximum residue levels to protect the health of consumers (Masiá et al., 2016).
Tang et al. (2019) proposed a portable and user-friendly method for on-site quantitative detection of organophosphorus pesticide (taking paraoxon as a model) by using PGM. The study was based on the fact that acetylcholinesterase could hydrolyze acetylthiocholine chloride to thiocholine, which would trigger the reduction of [Fe(CN)6]3- to [Fe(CN)6]4-. [Fe(CN)6]4- was then reoxidized on the surface of the glucose strip electrode to generate a current. Then the current would be detected by PGM. The detection limit was 5 mg/L for paraoxon, and the whole detection time was about 40 min. The developed method show advantages of fast reaction, but the sensitivity needs to be improved further.
Above all, most of the developed sensors based on PGM use antibody or aptamer as recognition molecule. However, these molecules have disadvantages of expensive and difficult to prepare, poor storage stability and poor anti-interference. Therefore, it is necessary to develop an alternative strategy based on abioticl material with property of antigen recognition.
Molecularly imprinted polymers (MIPs) are economical and stable synthetic receptors to recognize target molecules (Rycke et al., 2021). Chen et al. (2015) designed a novel sandwich-type strategy with PGM based on magnetic MIP nanoparticles and a β-cyclodextrin/invertase-functionalized signal probes for the specific and sensitive detection of chloramphenicol in animal-derived foods. The detection limit of the strategy was 0.16 ng/mL with a dynamic range from 0.5 to 50 ng/mL. Besides, compared with competitive ELISA, the detection time was obviously shorter, which was about 1 h.
Based on the antibacterial activity of enrofloxacin (as shown in Fig. 5), Kwon et al. (2018) developed a simple method for enrofloxacin detection in water and milk with PGM. Firstly, E. coli was cultured in lysogeny broth and glucose, and concentration of glucose would change because of bacterial metabolism. When there was enrofloxacin residues in the sample, the bacterial metabolism would be obstructed, causing the consumption of glucose decrease, which could be measured with PGM. The limit of detection for enrofloxacin reached to 5 ng/mL within 2 h in this reported work.
Schematic illustration of enrofloxacin detection in a solution of test sample, glucose, and Escherichia coli O157:H7 using a personal glucose meter or glucose paper test strips.
Quinine is an old antimalarial drug discovered in the 17th century. Up to now, it was an important anti-malarial drug, but it shows many side effects, such as carcinogenesis and worse resistance to antibiotics (Achan et al., 2011). Qiu et al. (2018) built an aptamer-invertase biosensor to quantify quinine in reclaimed wastewater with PGM. The proposed method shows advantages of low cost and simplify, and could be an alternative method to determine quinine in water management.
Li et al. (2020) report a novel method based on PGM for ampicillin detection in milk with aptamer as the recognition element and the streptavidin as the bridge to link the invertase and the aptamer. The proposed methods could be used in simple, sensitive and selective detection of ampicillin with detection limit of 2.5 × 10−10 mol/L.
Detection of heavy metal ion Heavy metal ions are an important pollutant to human health and the environment. One particular concern is toxic metal ions-lead (Pb2+), which can damage many organs and cause some permanent learning and behavior disorders in children (Xiang and Lu, 2012). Thus, it is of high demand to develop sensitive method to quantify it. Based on the fact that target-responsive cargo releasing from Pb2+-specific DNAzyme-capped mesoporous silica nanoparticles (MSNs) could cause the release of glucose, Fu et al. (2013) designed a simple strategy with PGM for Pb2+ detection in drinking water. Under optimum conditions, the method allows detection of Pb2+ at 1.0 pM with characters of simpleness, on-site, user-friendly and low-cost.
Detection of prohibited additive Melamine is often used as a starting point in synthetic resin manufacturing and was illegally added to milk to boost protein levels. It could cause serious healthy problems especially for infant (Chen et al., 2017). Therefore, establishing sensitive melamine detection method is of great need. Based on an in vitro selected structure-switching aptamer, Gu et al. (2015) proposed a simple method for detecting melamine in milk using PGM. The binding of melamine triggered the release of the invertase-DNA that is complementary to part of the aptamer, which could hydrolyze sucrose into glucose. The glucose produced was then measured directly with PGM, and the detection limit was 67.5 µg kg−1 in 80% whole milk.
Ractopamine (RAC), as one kind of β-agonists, is always used illegally as adulterants in feed since it can improve growth rate and reduce carcass fat (Lockard et al., 2019). Based on the use of PGM, Chen et al. (2015) establish an onsite ultrasensitive sandwich immunoassay for RAC detection (as shown in Fig. 6). In the study, magnetic nanoparticles coated with β-cyclodextrin (Fe3O4@SiO2-CD) were used to preconcentrate RAC, and an Envision reagent, which is a polymer containing many anti-IgG antibodies, was used to modify gold nanoparticles with invertase and anti-RAC antibodies. When RAC was present in the sample, sandwich immunocomplex was formed, the more RAC residues, the more immunocomplex formed, and the more glucose obtained from the hydrolysis of sucrose, which could cause significant PGM signal change. The method exhibited high sensitivity with a low detection limit of 0.34 µg/kg in samples. Clenbuterol (CLB) is another kind of β-agonist drug that is illegally added as a growth-promoting agent in livestock. Li et al. (2017) developed a facile and sensitive method for the detection of CLB in pork based on antigen-antibody reaction with PGM. The detection limit of the method for CLB was 0.1 ng/mL, demonstrating the proposed method could be a potentially valuable tool for food contamination determine.
Schematic illustration of an on-site immunosensor for ractopamine based on a personal glucose meter.
Detection of food composition Food composition analysis is an effect way to evaluate the nutrition and safety of food, comprehensively. Histidine is one of the 20 natural amino acids, playing important roles in central nervous system repair. The amount of histidine was strongly associated with many disease in human, such as psychological disorders, Parkinson's disease, and neurodeafness (Ma et al., 2010). Thus, it is significant and indispensable to monitor the amount of histidine in the food samples. Zhou et al. (2014) report a novel sensor for sensitive determination of histidine by combining PGM with click chemistry. Through copper(I) catalyzed azidealkyne cycloaddition (CuAAC) reaction, invertase-labeled alkynyl-DNA was conjugated with streptavidin magnespheres paramagnetic particles (PMPs), forming invertasefunctionalized PMPs complex. When there was histidine, CuAAC reaction was inhibited, resulting the decrease of PGM signal. The detection limit was 3.4 nmol/L and the linear range was 0.01–100 µM.
Nowadays more and more researchers expanded the application of PGM in sensitive and selective detect and ultra-low concentrations of contaminations in foods, with merits of no need of expensive and complicated instrumentation, low cost, portability, sensitivity and robustness towards interference (as shown in Table 1). However, they also shows some disadvantages and the direction of future development of PGM in analysis should be eliminating these shortcomings. (1) The existing methods based on PGM are limited when be applied in real food samples containing endogenous glucose, thus more efficient strategy should be designed to eliminate interference of endogenous glucose to further expand the application range of PGM in real food samples. (2) Analysis of multiple targets at the same time were not achieved by the existing methods based on PGM. In the future, research about detection of multiple targets could be performed by combining glucose meters with other analysis methods. (3) These meters are mainly used in detecting foodborne pathogens and mycotoxins. More effort should be made on expanding the application of PGM in the detecting pesticides drugs, illegal additive, and food composition. (4) New transduction and amplification pathways like based on novel nanomaterials and biomaterials like novel nanocomposites encapsulated with magnetic beads, liposome and DNA nanomaterials, should be further investigated to further enhance the sensitivity of the sensors based on PGM. (5) Novel recognition strategy based on peptide chain and click chemistry should be developed in the future. (6) Exploiting new strategy that can short the detection time. As a conclusion, there is still a long way to go to realize the wide application of PGM in the field of food analysis.
| Analytical method | Target | Sample | Detecting time | LOD | Reference |
|---|---|---|---|---|---|
| Immunoassay with PGM as readout | Salmonella | milk | About 2 h | 10 CFU/mL in milk | Joo et al. 2013 |
| Biological method with PGM as readout | E. coli | Potable water | About 19 h | 2 CFU/mL in Potable water | Chavali et al. 2014 |
| Immunochromatographic assay with PGM as readout | E. coli | Milk | 15 min | 6.2×104 CFU/mL in standard buffer | Huang et al. 2018 |
| Immunoassay based on antimicrobial peptide-mediated nanocomposite pair with PGM as readout | E. coli | Milk | About 1.8 h | 10 CFU/mL in milk | Bai et al. 2020 |
| Aptasensor with PGM as readout | S. aureus | - | About 1.6 h | 1.0×105 CFU/mL in milk | Wan et al. 2016 |
| An invasive DNA approach with PGM as readout | OTA | - | - | 6.8 ng/mL in standard buffer | Xiang and Lu, 2012 |
| DNA template-mediated click chemistry-based method with PGM as readout | OTA | Feed samples | About 1.7 h | 72 pg/mL in standard buffer | Qiu et al. 2019 |
| Aptasensor with PGM as readout | OTA | Red wine | About 1.3 h | 3.31 µg/L in standard buffer; 3.66 µg/L in samples | Gu et al. 2016 |
| Aptasensor with PGM as readout | OTA | Red wine | More than 1.3 h | 0.88 pg/mL in standard buffer | Zhang et al. 2021 |
| Aptasensor based on PGM and DNA walking machine | AFB1 | Bread | About 16.5 h | 10 pM in standard buffer; | Yang et al. 2018 |
| Nanodevice with PGM as readout | AFB1 | Wheat, maize | About 0.5 h | 0.02 ng/mLin standard buffer | Wang et al. 2019 |
| Immuno-sensor with PGM as readout | AFM1 | Milk | About 2 h | 27 ng/L in samples | Giovanni et al. 2019 |
| A novel strategy based on liposomes and PGM | Patulin | Apple and grape juice samples | More than 2 h | 0.05 ng/mL in standard buffer | Nie et al. 2020 |
| [Fe(CN)6] 3-based sensor with PGM as readout | Paraoxon | Apples and cucumbers samples | About 0.6 h | 5 mg/L in standard buffer | Tang et al. 2019 |
| Antibody-free sandwich-type strategy with PGM as readout | Chloramphenicol | Fish and pork samples | About 1 h | 0.16 ng/mL in standard buffer | Chen et al. 2015 |
| An assay based on glucose consumption by E. coli with PGM as readout | Enrofloxacin | Milk | Within 2 h | 5 ng/mL in standard buffer | Kwon et al. 2018 |
| Aptamer-invertase biosensor with PGM as readout | Quinine | Pure water and wastewater | About 1.3 h | 0.13 µM in pure water; 0.32 µM in reclaimed wastewater | Qiu et al. 2018 |
| A strategy based on DNAzyme-capped mesoporous silica nanoparticles with PGM as readout | Pb2+ | Drinking water | About 0.6 h | 1.0 pM in standard buffer | Fu et al. 2013 |
| A strategy based on an in vitro selected structure-switching aptamer | Melamine | Milk | About 1.5 h | 41.1 µg/L in standard buffer; 67.5 µg/kg in samples | Gu et al. 2015 |
| Immunosensor with PGM as readout | RAC | Pork samples | About 1.75 h | 0.34 ng/mL in standard buffer | Chen et al. 2015 |
| Immunosensor with PGM as readout | CLB | Pork and liver samples | About 1.8 h | 0.1 ng/mL in standard buffer | Li et al. 2017 |
| Chemical sensor based on click chemistry and PGM | Histidine | Milk | About 1.8 h | 3.4 nM in standard buffer | Zhou et al. 2014 |
Acknowledgements This research was Funded by Science and Technology Project of Hebei Education Department (QN2020177), Hebei University of Science and Technology Graduate Innovation Funding Program (XJCXZZSS2022007).
Conflict of interest There are no conflicts of interest to declare.
