Determination of acrylamide in food products based on the fluorescence enhancement induced by distance increase between functionalized carbon quantum dots

Portable real-time determination of Escherichia coli O157:H7 and Staphylococcus aureus based on smartphones and hydrogels

The aptamers functionalized orange-emission carbon dots (OCDs) and green-emission carbon dots (GCDs) had dual-emission peaks with single excitation. Tungsten disulfide nanosheets (WS2 NSs)-triggered fluorescence quenching achieved the ratiometric fluorescence determination of Escherichia coli O157:H7 (E. coli O157:H7) and Staphylococcus aureus (S. aureus) with wide ranges of 18-1.8 × 106 and 37-3.7 × 107 CFU/mL and low detection limits of 8 and 20 CFU/mL, respectively. The results in real sample with recoveries of 90-101 % and RSD < 4.12 % were no significant difference from standard plate counting method. Meanwhile, the dual-color CDs were further adopted in the smartphone-assisted hydrogel platform and achieved speedy, sensitive, portable and real-time determination of E. coli O157:H7 and S. aureus in real samples. This work has not only developed ratiometric fluorescence detection and constructed a portable hydrogel platform, but also provided a unique strategy in developing a time-efficient and easy-to-use portable device in food safety monitoring.

Advancements in Chemical and Biosensors for Point-of-Care Detection of Acrylamide

Acrylamide (AA), an odorless and colorless organic small-molecule compound found generally in thermally processed foods, possesses potential carcinogenic, neurotoxic, reproductive, and developmental toxicity. Compared with conventional methods for AA detection, bio/chemical sensors have attracted much interest in recent years owing to their reliability, sensitivity, selectivity, convenience, and low cost. This paper provides a comprehensive review of bio/chemical sensors utilized for the detection of AA over the past decade. Specifically, the content is concluded and systematically organized from the perspective of the sensing mechanism, state of selectivity, linear range, detection limits, and robustness. Subsequently, an analysis of the strengths and limitations of diverse analytical technologies ensues, contributing to a thorough discussion about the potential developments in point-of-care (POC) for AA detection in thermally processed foods at the conclusion of this review.

A ratiometric fluorescent "off-on" sensor for acrylamide detection in toast based on red-emitting copper nanoclusters stabilized by bovine serum albumin

Acrylamide, as a Class 2A carcinogen, poses serious threats to human health. To achieve rapid and accurate determination of acrylamide in food, a ratiometric fluorescent "off-on" sensor was designed by incorporating red-emitting copper nanoclusters and glutathione. Copper nanoclusters with bimodal emission at 395 nm and 650 nm (excited at 310 nm) were synthesized by using bovine serum albumin as the ligand and ascorbic acid as the reductant. With glutathione addition, the fluorescence intensity at 650 nm gradually decreased, while the case at 395 nm slightly increased. The quenched fluorescence at 650 nm was subsequently restored by acrylamide through thiol-ene Michael addition reaction between acrylamide and glutathione. The constructed sensor showed excellent performance towards acrylamide detection in the range of 5-300 μM with a detection limit of 1.48 μM, and was further applied to real-sample detection of acrylamide in toast and exhibited good recoveries (90.29-101.30 %), indicating potential applications of this sensor.

QD-based fluorescent nanosensors: Production methods, optoelectronic properties, and recent food applications

Food quality and safety are crucial public health concerns with global significance. In recent years, a series of fluorescence detection technologies have been widely used in the detection/monitoring of food quality and safety. Due to the advantages of wide detection range, high sensitivity, convenient and fast detection, and strong specificity, quantum dot (QD)-based fluorescent nanosensors have emerged as preferred candidates for food quality and safety analysis. In this comprehensive review, several common types of QD production methods are introduced, including colloidal synthesis, self-assembly, plasma synthesis, viral assembly, electrochemical assembly, and heavy-metal-free synthesis. The optoelectronic properties of QDs are described in detail at the electronic level, and the effect of food matrices on QDs was summarized. Recent advancements in the field of QD-based fluorescent nanosensors for trace level detection and monitoring of volatile components, heavy metal ions, food additives, pesticide residues, veterinary-drug residues, other chemical components, mycotoxins, foodborne pathogens, humidity, and temperature are also thoroughly summarized. Moreover, we discuss the limitations of the QD-based fluorescent nanosensors and present the challenges and future prospects for developing QD-based fluorescent nanosensors. As shown by numerous publications in the field, QD sensors have the advantages of strong anti-interference ability, convenient and quick operation, good linear response, and wide detection range. However, the reported assays are laboratory-focused and have not been industrialized and commercialized. Promising research needs to examine the potential applications of bionanotechnology in QD-based fluorescent nanosensors, and focus on the development of smart packaging films, labeled test strips, and portable kits-based sensors.

Detection of SARS-CoV-2 S protein based on FRET between carbon quantum dots and gold nanoparticles

The COVID-19 pandemic caused by SARS-CoV-2 virus brings nasty crisis for public health in the world. Until now, the virus has caused multiple infections in many people. Detecting antigen to SARS-CoV-2 is a powerful method for the diagnosis of COVID-19 and is helpful for controlling and stopping the pandemic. Herein, a rapid and quantitative detection method of SARS-CoV-2 spike(S) protein was built based on the fluorescence resonance energy transfer (FRET) phenomenon without complicated steps. In the process of detecting, the carbon quantum dots (CQDs) and gold nanoparticles (AuNPs) act as donor and acceptor. By modifying the SARS-CoV-2 antibodies on the surface of CQDs and AuNPs, we achieved S protein specific detection using the distance-based FRET phenomenon. Through the electric charge regulation, the limit of detection (LOD) is 0.05 ng/mL, the linear range is 0.1-100 ng/mL, and the detection process only takes 12 min. The proposed method exhibits several advantages such as be available for variants (B.1.1.529 and B.1.617.2) and be suitable for human serum, which is of significance for detecting viral in time and prevention the viral transmission.

Food contaminants and potential risk of diabetes development: A narrative review

The number of people diagnosed with diabetes continues to increase, especially among younger populations. Apart from genetic predisposition and lifestyle, there is increasing scientific and public concern that environmental agents may also contribute to diabetes. Food contamination by chemical substances that originate from packaging materials, or are the result of chemical reactions during food processing, is generally recognized as a worldwide problem with potential health hazards. Phthalates, bisphenol A (BPA) and acrylamide (AA) have been the focus of attention in recent years, due to the numerous adverse health effects associated with their exposure. This paper summarizes the available data about the association between phthalates, BPA and AA exposure and diabetes. Although their mechanism of action has not been fully clarified, in vitro, in vivo and epidemiological studies have made significant progress toward identifying the potential roles of phthalates, BPA and AA in diabetes development and progression. These chemicals interfere with multiple signaling pathways involved in glucose and lipid homeostasis and can aggravate the symptoms of diabetes. Especially concerning are the effects of exposure during early stages and the gestational period. Well-designed prospective studies are needed in order to better establish prevention strategies against the harmful effects of these food contaminants.

Study the interaction of amino acids, sugars, thermal treatment and cooking technique on the formation of acrylamide in potato models

This study unveiled the effect of the suspected precursors of acrylamide (asparagine, glutamine) combined/separated with different formulations of glucose, fructose, and sucrose. To better understand the interaction between acrylamide precursors, cooking technique (deep vs air frying), and temperature (170 °C vs 190 °C), seven potato models from starch, sugars, amino acids, water and hydrocolloids (alginate and agar) were formulated. In line with previous findings, the present results showed that asparagine, glucose and fructose played an important role in acrylamide formation in these synthetic potato models. Furthermore, glutamine and sodium alginate might have an inhibitory effect on acrylamide formation. A significant impact of frying technique was also revealed. On the other hand, GC-FID analysis detected acrylamide in only these three models, (glucose-fructose, sucrose and asparagine-glucose/fructose/sucrose models > LOD 333.33 µg.kg^-1).

A smartphone-assisted ultrasensitive detection of acrylamide in thermally processed snacks using CQD@Au NP integrated FRET sensor

Selective, sensitive, and accurate detection of acrylamide (AA) in thermally processed food is a great challenge for food safety. This paper describes a "turn-on" fluorescence strategy to detect AA in real samples. Herein, the fluorescence intensity of glutathione-modified carbon quantum dots (GSHCQDs) was quenched initially upon the addition of gold nanoparticles (Au NPs) via fluorescence resonance electron transfer (FRET) to form a quenched GSHCQD-Au nanoprobe. When AA was introduced to the quenched GSHCQD-Au nanoprobe, the strong thiol-ene Michael addition (M-A) reaction among the -SH group of GSHCQD and AA occurred which releases GSHCQD to the medium and FL intensity at 520 nm is regained. The GSHCQD-Au nanoprobe can detect the AA in a normal aqueous solution (pH 7) selectively over a short response time of 5 min. Under the optimized conditions, the detection limit of AA was obtained to be 0.12 pM, over a wide linear range of 0-200 nM. Especially, this FRET-based sensing method was utilized successfully for the sensitive detection of AA using an RGB app installed on a smartphone, opening a new approach for the smart sensing of food contaminants.

A Fast and Easy Probe Based on CMC/Eu (Ⅲ) Nanocomposites to Detect Acrylamide in Different Food Simulants Migrating from Food-Contacting Paper Materials

The residual acrylamide in food paper packaging can be transferred into water and food, which will cause harmful effects on human beings. In this paper, a rapid and easily available fluorescent probe based on carboxymethyl cellulose (CMC)/Eu (Ⅲ) nanocomposites was designed to detect the residue acrylamide with high sensibility. The probe could respond in 1 min. The concentration of acrylamide was linearly correlated to the fluorescence intensity of the probe at the emission wavelength of 615 nm in the concentration range of 0.1–100 μmol/L. The limit of detection (LOD) of the probe was 0.085 μg/L, which is lower than the guideline value of the European Union, the U.S. EPA, and the WHO. An experiment was performed to simulate the acrylamide migrating from food-contacting paper materials to different foods, including waterborne food, alcohol beverage, acidic food, and greasy food. The recoveries and RSDs of acrylamide in all samples indicated that the CMC/Eu (Ⅲ) fluorescent probe was efficient for acrylamide detection. The possible mechanism of the probe for acrylamide detection involved both dynamically quenching and static quenching by forming of non-fluorescent substances.

Ratiometric Fluorescent Metal-Organic Framework Biosensor for Ultrasensitive Detection of Acrylamide

Acrylamide is a neurotoxin and carcinogen that forms during the thermal processing of food, inflicting irreversible harm to human health. Herein, a ratiometric fluorescence biosensor based on a 6-carboxyfluorescein-labeled aptamer (FAM-ssDNA) and porphyrin metal-organic framework (PCN-224) was developed. PCN-224 exhibits strong adsorption capacity for FAM-ssDNA and also quenches the fluorescence of FAM-ssDNA via fluorescence resonance energy transfer and photoinduced electron transfer. FAM-ssDNA hybridizes with complementary DNA to form double-stranded DNA (FAM-dsDNA), which is liberated from the PCN-224 surface, resulting in fluorescence recovery. However, the intrinsic fluorescence of the ligand remains unchanged. Acrylamide can create an adduct with FAM-ssDNA and inhibit the hybridization of FAM-dsDNA, thus realizing ratiometric sensing of acrylamide. The proposed biosensor displays excellent detection performance from 10 nM∼0.5 mM with a limit of detection of 1.9 nM. In conclusion, a fabricated biosensor was successfully applied to detect acrylamide in thermally processed food, and the results were consistent with those of high-performance liquid chromatography.

A fluorescence biosensor based on double-stranded DNA and a cationic conjugated polymer coupled with exonuclease III for acrylamide detection

As a toxic substance on human health produced in food thermal treatment, simple analytical approaches are highly desired for the detection of acrylamide (ACR) in foods. With the aid of exonuclease III (Exo III), a simple fluorescence sensor was proposed based on carboxyfluorescein-labeled double-stranded DNA (FAM-dsDNA) and a cationic conjugated polymer (PFP). Fluorescence resonance energy transfer (FRET) efficiency between FAM and PFP was changed with and without ACR. When ACR was present, ACR and single-stranded DNA (P1, ssDNA) formed an adduct, allowing free FAM-labeled complementarity strand DNA (P2, FAM-csDNA) to appear in the solution and avoiding the digestion of P2 by Exo III. After the addition of PFP, the interaction of PFP and FAM induced strong FRET. Under optimized conditions, ACR was detected with a limit of detection (LOD) of 0.16 μM. According to this biosensor, a LOD of 1.3 μM in water extract samples was observed with a good recovery rate (95-110 %).

A portable kit based on thiol-ene Michael addition for acrylamide detection in thermally processed foods

Accurate, sensitive, and selective analysis of acrylamide generated in thermally processed foods is of great significance for food safety. Herein, a novel acrylamide sensing platform is designed for both sensitive on-site colorimetric analysis and accurate UV-vis spectroscopy quantification, by integrating thiol-ene Michael addition with gold nanoparticles-mediated catalytical oxidation. The Michael addition reaction between acrylamide and glutathione efficiently alleviates glutathione-induced catalytic activity inhibition of gold nanoparticles, evoking the chromogenic reaction of H₂O₂-mediated 3,3',5,5'-tetramethylbenzidine. With increasing the concentration of acrylamide, the oxidation of 3,3',5,5'-tetramethylbenzidine is accelerated, presenting a series of shades from colorless to blue. The sensing platform exhibits excellent detection performance of acrylamide in the range of 0.5-175 μM with a detection limit of 0.16 μM, and is successfully employed in food samples. Especially, a portable assay kit based on the proposed platform is developed for visual determination of acrylamide, opening an avenue for smart sensors of food safety hazards.

A fluorescence aptasensor based on carbon quantum dots and magnetic Fe3O4 nanoparticles for highly sensitive detection of 17β-estradiol

Trace amounts of 17β-estradiol (E2) in food and the environment poses a threat to human health, which has created the demand for sensitive analytical methods to detect E2. In this study, a novel fluorescent aptasensor was developed for sensitive detection of E2 based on double-chain hybridization between carbon quantum dots-labelled with E2 aptamer (CQDs-aptamer) and Fe₃O₄ nanoparticles modified by complementary DNA (Fe₃O₄-cDNA). Under the optimal conditions, the aptasensor displayed a good linear range of 10^-11-10^-6 M for E2 with the coefficient of determination (R²) of 0.996, and a low detection limit of 3.48 × 10^-12 M was obtained. Besides, the aptasensor showed high selectivity and good reproducibility for E2 detection, which was successfully applied to the sensitive detection of E2 in milk as compared with tap water and lake water with satisfactory recoveries from 85.21% to 114.80%, suggesting the great significance of this aptasensor for detecting food contaminants in the food industry.

Nanomaterials Enabled and Bio/Chemical Analytical Sensors for Acrylamide Detection in Thermally Processed Foods: Advances and Outlook

Acrylamide, a food processing contaminant with demonstrated genotoxicity, carcinogenicity, and reproductive toxicity, is largely present in numerous prominent and commonly consumed food products that are produced by thermal processing methods. Food regulatory bodies such as the U.S. Food and Drug Administration (U.S. FDA) and European Union Commission regulations have disseminated various acrylamide mitigation strategies in food processing practices. Hence, in the wake of such food and public health safety efforts, there is a rising demand for economic, rapid, and portable detection and quantification methods for these contaminants. Since conventional quantification techniques like liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) methods are expensive and have many drawbacks, sensing platforms with various transduction systems have become an efficient alternative tool for quantifying various target molecules in a wide variety of food samples. Therefore, this present review discusses in detail the state of robust, nanomaterials-based and other bio/chemical sensor fabrication techniques, the sensing mechanism, and the selective qualitative and quantitative measurement of acrylamide in various food materials. The discussed sensors use analytical measurements ranging from diverse and disparate optical, electrochemical, as well as piezoelectric methods. Further, discussions about challenges and also the potential development of the lab-on-chip applications for acrylamide detection and quantification are entailed at the end of this review.

A fluorescence biosensor based on single-stranded DNA and carbon quantum dots for acrylamide detection

As a potential carcinogen produced in food thermal processing, acrylamide (AM) can cause irreversible harm to human health. For the detection of AM in food products, a simple fluorescent biosensor based on single-stranded DNA (ssDNA) and carbon quantum dots (CQDs) was developed. Reduced fluorescence intensity of CQDs at 445 nm (excitation at 350 nm) was induced by the attachment of ssDNA. In the presence of AM, ssDNA was preferentially bound to AM by hydrogen bonding and the degree of fluorescence reduction was smaller than that without AM. Under optimized conditions, results showed that the sensing approach for detecting AM had a low detection limit of 2.41 × 10^-8 M in the standard solution, and a linear relationship ranging from 5 × 10^-3 to 1 × 10^-7 M with the determination coefficient (R²) of 0.9895 was obtained. Furthermore, a good recovery percentage (91.36-98.11%) in bread crust showed the potential for practical applications of this proposed biosensor.

Sensor and Bioimaging Studies Based on Carbon Quantum Dots: The Green Chemistry Approach

Since carbon quantum dots have high photoluminescent efficiency, it has been a desired material in sensor and bioimaging applications. In recent years, the green chemistry approach has been preferred and the production of quantum dots has been reported in many studies using different precursors from natural, abundant, or waste sources. Hydrothermal, chemical oxidation, microwave supported, ultrasonic, solvothermal, pyrolysis, laser etching, solid-state, plasma, and electrochemical methods have been reported in the literature. In this review article, green chemistry strategies for carbon quantum dot synthesis is summarized and compared with conventional methods using methodologic and statistical data. Furthermore, a detailed discussion on sensor and bioimaging applications of carbon quantum dots produced with green synthesis approaches are presented with a special focus on the last decade.