Application of Quantum Dot-Molecularly Imprinted Polymer Core-Shell Particles Sensitized with Graphene for Optosensing of N(ε)-Carboxymethyllysine in Dairy Products

Recent advances in molecularly imprinted polymers (MIPs) for visual recognition and inhibition of α-dicarbonyl compound-mediated Maillard reaction products

α-Dicarbonyl compounds (α-DCs) are important intermediates and precursors of harmful Maillard reaction products (e.g., acrylamide and late glycosylation end-products), and they exist widely in thermoprocessed sugar- or fat-rich foods. α-DCs and their end-products are prone to accumulation in the human body and lead to the development of various chronic diseases. Therefore, detection of α-DCs and their associated hazards in food samples is crucial. This paper reviews the preparation of molecularly imprinted polymers (MIPs) enabling visual intelligent responses and the strategies for recognition and capture of α-DCs and their associated hazards, and provides a comprehensive summary of the development of visual MIPs, including integration strategies and applications with real food samples. The visual signal responses as well as the mechanisms for hazard recognition and capture are highlighted. Current challenges and prospects for visual MIPs with advanced applications in food, agricultural and environmental samples are also discussed. This review will open new horizons regarding visual MIPs for recognition and inhibition of hazards in food safety.

Magnetically Controlled Nanorobots Based on Red Emissive Peptide Dots and Artificial Antibodies for Specific Recognition and Smart Scavenging of Nε-(Carboxymethyl)lysine in Dairy Products

Food-borne advanced glycation end products (AGEs) are highly related to various irreversible diseases, and N^ε-(carboxymethyl)lysine (CML) is the typical hazardous AGE. The development of feasible strategies to monitor and reduce CML exposure has become desirable to address the problems. In this work, we proposed magnetically controlled nanorobots by integrating an optosensing platform with specific recognition and binding capability, realizing specific anchoring and accurate determination as well as efficient scavenging of CML in dairy products. The artificial antibodies offered CML imprinted cavities for highly selective absorption, and the optosensing strategy was designed based on electron transfer from red emissive self-assembling peptide dots (r-SAPDs) to CML, which was responsible for the identity, response, and loading process. The r-SAPDs overcame the interference from autofluorescence, and the limit of detection was 0.29 μg L^-1, which bestowed accuracy and reliability for in situ monitoring. The selective binding process was accomplished within 20 min with an adsorption capacity of 23.2 mg g^-1. Through an external magnetic field, CML-loaded nanorobots were oriented, moved, and separated from the matrix, which enabled their scavenging effects and reusability. The fast stimuli-responsive performance and recyclability of the nanorobots provided a versatility strategy for effective detection and control of hazards in food.

Molecularly Imprinted Polymer-Quantum Dot Materials in Optical Sensors: An Overview of Their Synthesis and Applications

In the last decades analytical methods have focused on the determination of target analytes at very low concentration levels. This has been accomplished through the use of traditional analytical methods that usually require high reagent consumption, expensive equipment and long pretreatment steps. Thus, there is a demand for simple, rapid, highly selective and user-friendly detection procedures. Quantum dots (QDs) are semiconductor fluorescent nanomaterials with unique optoelectronic properties that have shown great potential for the development of fluorescence probes. Besides, the combination of QDs with molecularly imprinted polymer (MIPs), synthetic materials with selective recognition, have been proposed as useful materials in the development of optical sensors. The resulting MIP-QDs optical sensors integrate the advantages of both techniques: the high sensitivity of QDs-based fluorescence sensors and the high selectivity of MIPs. This review gives a brief overview of the strategies for the synthesis of MIPs-QDs based optical sensors, highlighting the modifications in the synthesis procedure that improve the sensor performance. Finally, a revision of recent applications in sensing and bioimaging is presented.

A novel enhanced fluorescence method based on multifunctional carbon dots for specific detection of Hg2+ in complex samples

Carbon quantum dots (CQDs), especially originated from biomass, have emerged as a rising star for the construction of metal ion sensor because they can serve as sensitive, selective and biocompatible probes. The present work describes a novel kind of ascorbic acid (AA)-enhanced CQDs which are synthesized with a kind of famous green teas, Maojian, serving as carbon source. Compared with the CQDs only based on Maojian teas, citric acid (CA)-enhanced and ascorbic acid (AA)-enhanced CQDs had the enhanced fluorescence intensity, and different response characteristics. In addition, the (AA)-enhanced CQDs showed more sensitive and specific fluorescence response to Hg²⁺ than simple ones, with a detection limit of 6.32 × 10^-9 nmol·L^-1. A linear response range from 2.00 × 10^-7 mol·L^-1 to 6.00 × 10^-5 mol·L^-1 was also achieved. The (AA)-enhanced CQDs also demonstrate good stability. They could effectively sense the Hg²⁺ in complex samples including waste water, tea and rice. Therefore, these versatile (AA)-enhanced CQDs fluorescence method hold a promising potential in other promising applications such as pharmaceutical quality, environmental quality, and food safety monitoring.

Semiconductor nanocrystal-polymer hybrid nanomaterials and their application in molecular imprinting

Quantum dots (QDs) are attractive semiconductor fluorescent nanomaterials with remarkable optical and electrical properties. The broad absorption spectra and high stability of QD transducers are advantageous for sensing and bioimaging. Molecular imprinting is a technique for manufacturing synthetic polymeric materials with a high recognition ability towards a target analyte. The high selectivity of the molecularly imprinted polymers (MIPs) is a result of the fabrication process based on the template-tailored polymerization of functional monomers. The three-dimensional cavities formed in the polymer network can serve as the recognition elements of sensors because of their specificity and stability. Appending specific molecularly imprinted layers to QDs is a promising strategy to enhance the stability, sensitivity, and selective fluorescence response of the resulting sensors. By merging the benefits of MIPs and QDs, inventive optical sensors are constructed. In this review, the recent synthetic strategies used for the fabrication of QD nanocrystals emphasizing various approaches to effective functionalization in aqueous environments are discussed followed by a detailed presentation of current advances in QD conjugated MIPs (MIP-QDs). Frontiers in manufacturing of specific imprinted layers of these nanomaterials are presented and factors affecting the specific behaviour of an MIP shell are identified. Finally, current limitations of MIP-QDs are defined and prospects are outlined to amplify the capability of MIP-QDs in future sensing.

In-Taken Labeling and in Vivo Tracing Foodborne Probiotics via DNA-Encapsulated Persistent Luminescence Nanoprobe Assisted Autofluorescence-Free Bioimaging

An in vivo probing strategy that can real-time and in situ trace target probiotics inside the living body is herein proposed by employing plasmid-like DNA as in-taken assistance, persistent luminescence nanophosphors (PLNPs) as optical labeling, and background-free fluorescence bioimaging as signal readout. PLNPs with superlong afterglow and excellent biocompatibility and stability were surface-modified by DNA molecules with a specific sequence, which greatly promoted the nanoparticle penetration into the bacteria and facilitated the in vivo bioimaging with high sensitivity and signal-to-noise ratio. Compared with the previous surface-labeling strategy by antibody recognition, the in-taken optical labeling demonstrated improved stability, and reached ideal results of real-time and in situ monitoring the in vivo behaviors of target probiotics, supporting the further development of in vivo investigation methodology for foodborne probiotics. Moreover, such a strategy offers a promising platform that leverage nanoscience to food nutrition as well as food-safety research, aiming to collect more accurate and fresh information from the living body.

A high photoluminescence sensor for selective detection of cartap based on functionalized VBimBF4B ionic liquid-strengthened sulfur-doped carbon nanodots

A photoluminescence sensor based on functionalized room temperature ionic liquid-strengthened sulfur-doped carbon nanodots is developed for real-time monitoring of cartap.

Effects of Highland Barley Bran Extract Rich in Phenolic Acids on the Formation of Nε-Carboxymethyllysine in a Biscuit Model

Highland barley, a staple food in northwest China, is a well-known source of bioactive phytochemicals, including phenolic compounds. This study evaluated the inhibitory effects of highland barley bran extract (HBBE) on the advanced glycation end product (AGE) levels in a biscuit model, as measured by N^ε-carboxymethyllysine (CML) content. CML was detected in all inhibition models using HBBE extracted with different solvents. Under optimal conditions, CML formation in the heated model system composed of glucose/lysine/linoleic acid was effectively inhibited by HBBE. This inhibition effect using extracts from 60% acetone solution was 45.58%. Five major phenolic acids from HBBE (ferulic, syringic, sinapic, p-coumaric, and caffeic acids) were further tested for their trapping and scavenging abilities of glyoxal, a reactive carbonyl species and a key intermediate compound for forming CML. This study has demonstrated that HBBE can potentially control CML formation during food processing, therefore effectively reducing glycation in foods and benefiting those with chronic diseases.

Upconversion Nanophosphor-Involved Molecularly Imprinted Fluorescent Polymers for Sensitive and Specific Recognition of Sterigmatocystin

Originated from the bottom-up synthetic strategy, molecularly imprinted polymers (MIPs) possess the inherent ability of selective and specific recognition and binding of the target analytes, with their structural cavities that can match the target molecules in respect to size, shape, and functional groups. Herein, based on the high selectivity of MIPs and the fluorescence properties of the β-NaYF₄:Yb3+, Er3+ upconversion nanoparticles, MIPs with both specificity and fluorescent signals are fabricated to recognize trace sterigmatocystin (ST) with high selectivity and sensitivity. The structure analogue of ST, 1,8-dihydroxyanthraquinone (DT), was employed as the template molecule, acrylamide as the functional monomer, 3-methacryloyloxypropyltrimethoxysilane as the crosslinking agent, and a new molecular imprinting technique of non-aqueous sol-gel method is used to synthesize a molecularly imprinted material with high selectivity to ST. Under optimal conditions, the fluorescence enhancement of fluorescent MIPs increased as the concentration of ST increased. In the range of 0.05⁻1.0 mg L-1, fluorescence enhancement and the concentration showed a good linear relationship with a detection limit of 0.013 mg L-1. Real sample analysis achieved the recoveries of 83.8⁻88.8% (RSD 5.1%) for rice, 82.1⁻87.5% (RSD 4.6%) for maize, and 80.6⁻89.2% (RSD 3.0%) for soybeans, respectively, revealing the feasibility of the developed method.