An optical nanosensor fabricated by carbon dots embedded in silica molecularly imprinted polymer for sensitive detection of ceftazidime antibiotic

Selective and Rapid Optical Detection of Citalopram Using a Fluorescent Probe Based on Carbon Quantum Dots Embedded in Silica Molecularly Imprinted Polymer

In this study, a citalopram optical nano-sensor was developed. Citalopram is a well-known antidepressant drug that reduces the reuptake of serotonin in neurons as a result, serotonin neurotransmission, the primary response to antidepressant treatments, increases in many parts of the brain. This study introduces a carbon quantum dots (CQDs)-based optical nanosensor for rapid detection of citalopram. This fluorescent nanosensor was made through the polymerization of tetraethyl orthosilicate in the presence of CQDs as the fluorescent materials and citalopram as the template molecule. Following the polymerization, the templated molecules were washed and removed from the structure, and the matrix of the polymer was left with some cavities that resembled citalopram in terms of size and shape. The final structure which is used as a chemical nanosensor, is named carbon quantum dots embedded silica molecularly imprinted polymer (CQDs-SMIP). The materials used in designing nano-sensors were characterized using FTIR, UV/Vis, and fluorescence spectroscopy, as well as high-resolution transmission electron microscopy (HR-TEM), and field emission scanning electron microscopy (FESEM). CQDs-SMIP showed a strong fluorescence emission at 420 nm in the absence of the template molecule. The fluorescence intensity of the nanosensor decreased in the presence of citalopram. The correlation between the extent of the fluorescence quenching and the concentration of citalopram provided the nano-sensor signal. The nano-sensor was used to measure citalopram in complex matrices such as human plasma and urine samples with remarkable selectivity and sensitivity. The detection limit of 10.3 µg.L-1 over a linear range of 100 to 700 µg.L-1, and RSD of 3.15% was obtained. This nano-sensor was applied to analyze of citalopram in plasma and human urine samples with remarkable results.

Synthesis of polymer dots as fluorescent nanoprobe for the detection of Ponceau 4R, an additive color abuse in food

Abusing organic dyes in industrial food products is an important issue in many countries. Rapid chemical sensing of these compounds can be of great importance during the industrial life of humans. In this work, we synthesized a new fluorescent polymer dot and successfully applied it as an optical probe for the detection of red color abuse in foodstuffs. Ponceau 4R is a red organic dye additive that is used in some foodstuffs such as tomato sauces or pastes. It is too hazardous to human health. Detection of such abusage is challenging. The development of π-conjugated polymer dots having a bright emission band at visible can be a promising probe for the detection of food color additives. A variety of methods and monomers were previously used for their synthesis. Here, the Suzuki Coupling method was employed. The limit of detection (LOD) of the method was obtained 16 nmol L-1 for the detection of Ponceau 4R.

A Review of Sensing Applications of Molecularly Imprinted Fluorescent Carbon Dots for Food and Biological Sample Analysis

Molecularly imprinted fluorescent carbon dots (MI-FCDs) find numerous applications in analytical chemistry due to their outstanding photoluminescent properties and having specific pockets for the recognition of target molecules. Despite significant advances, practical applications of MI-FCDs-based fluorescent sensors are still in their initial stages. Therefore, the topical developments in the synthesis, working, and application of MI-FCDs for sensing various target species (e.g., pharmaceuticals, biomolecules, pesticides, food additives, and miscellaneous species) in food and biological media have been highlighted. Moreover, a careful evaluation has been made to select the best methods based on their performance in terms of analytical parameters. To expand the horizons of this field, important challenges and future directions for developing MI-FCDs for practical use are also presented. This review will highlight important aspects of MI-FCDs-based fluorescent sensors for their applicability in food science, material science, environmental science, nanoscience, and biotechnology.

Simple detection of gluten in wheat-containing food samples of celiac diets with a novel fluorescent nanosensor made of folic acid-based carbon dots through molecularly imprinted technique

A nanosensor is designed for rapid detection of the gluten content of wheat-containing samples. Gluten is a plant protein that causes allergy in individuals and leads to celiac disease. Since in a celiac diet trace amounts of gluten are able to prompt allergic reactions, a food-allergen label must be provided on foodstuffs and be seriously considered by food industries. Various analytical methods and commercial immunoassays are used for such analyses but prices per test, especially for low-income countries are high. Thus, a rapid, sensitive, simple, and inexpensive detecting tool seems essential. A solution can be designing a gluten optical nanosensor. The nanosensor is made of folic-acid-carbon dots and gluten molecularly templates embedded simultaneously in a silicate matrix. Adding gluten to the solution of this nanostructure and its adsorbing on the blank templated space on the nanostructure causes fluorescence enhancement. The concentration range of gluten detection was 0.36 to 2.20 µM.

N-doped carbon dots coupled with molecularly imprinted polymers as a fluorescent sensor for ultrasensitive detection of genistein in soya products

Rapid detection of genistein in soya products has remained difficult. Current methods necessitate sample handling and use of costly instruments. Here, using a simple one-pot reverse microemulsion method, a sensor based on N-doped carbon dots conjugated molecularly imprinted polymers (N-CDs@MIPs) was synthesized to analyze genistein. N-doped carbon dots were used as fluorescent component, genistein as the template molecule, and molecularly imprinted polymers as the selective sorbent in this fluorescence sensor. The sensor was then examined and optical studies demonstrated that N-CDs@MIPs not only had strong fluorescence emission and outstanding optical stability, but also had good sensitivity (detection limit 35.7 nM) and selectivity to genistein. Furthermore, the N-CDs@MIPs materials were used to analyze genistein in soya products, and the findings (which ranged from 99.77% to 106.11%) show that the N-CDs@MIPs has high potential for quickly detecting the amount of genistein in complicated food samples.

A Fusion of Molecular Imprinting Technology and Siloxane Chemistry: A Way to Advanced Hybrid Nanomaterials

Molecular imprinting technology is a well-known strategy to synthesize materials with a predetermined specificity. For fifty years, the "classical" approach assumed the creation of "memory sites" in the organic polymer matrix by a template molecule that interacts with the functional monomer prior to the polymerization and template removal. However, the phenomenon of a material's "memory" provided by the "footprint" of the chemical entity was first observed on silica-based materials nearly a century ago. Through the years, molecular imprinting technology has attracted the attention of many scientists. Different forms of molecularly imprinted materials, even on the nanoscale, were elaborated, predominantly using organic polymers to induce the "memory". This field has expanded quickly in recent years, providing versatile tools for the separation or detection of numerous chemical compounds or even macromolecules. In this review, we would like to emphasize the role of the molecular imprinting process in the formation of highly specific siloxane-based nanomaterials. The distinct chemistry of siloxanes provides an opportunity for the facile functionalization of the surfaces of nanomaterials, enabling us to introduce additional properties and providing a way for vast applications such as detectors or separators. It also allows for catalyzing chemical reactions providing microreactors to facilitate organic synthesis. Finally, it determines the properties of siloxanes such as biocompatibility, which opens the way to applications in drug delivery and nanomedicine. Thus, a brief outlook on the chemistry of siloxanes prior to the discussion of the current state of the art of siloxane-based imprinted nanomaterials will be provided. Those aspects will be presented in the context of practical applications in various areas of chemistry and medicine. Finally, a brief outlook of future perspectives for the field will be pointed out.

Polymer based nanocomposites: A strategic tool for detection of toxic pollutants in environmental matrices

A large fraction of population is suffering from waterborne diseases due to the contaminated drinking water. Both anthropogenic and natural sources are responsible for water contamination. Revolution in industrial and agriculture sectors along with a huge increase in human population has brought more amount of wastes like heavy metals, pesticides and antibiotics. These toxins are very harmful for human health, therefore, it is necessary to sense their presence in environment. Conventional strategies face various problems in detection and quantification of these pollutants such as expensive equipment and requirement of high maintenance with limited portability. Recently, nanostructured devices have been developed to detect environmental pollutants. Polymeric nanocomposites have been found robust, cost effective, highly efficient and accurate for sensing various environmental pollutants and this is due to their porous framework, multi-functionalities, redox properties, great conductivity, catalytic features, facile operation at room temperature and large surface area. Synergistic effects between polymeric matrix and nanomaterials are responsible for improved sensing features and environmental adaptability. This review focuses on the recent advancement in polymeric nanocomposites for sensing heavy metals, pesticides and antibiotics. The advantages, disadvantages, operating conditions and future perspectives of polymeric nanocomposites for sensing toxic pollutants have also been discussed.

A Brief Review of Carbon Dots-Silica Nanoparticles Synthesis and their Potential Use as Biosensing and Theragnostic Applications

Carbon dots (CDs) are carbon nanoparticles with sizes below 10 nm and have attracted attention due to their relatively low toxicity, great biocompatibility, water solubility, facile synthesis, and exceptional photoluminescence properties. Accordingly, CDs have been widely exploited in different sensing and biomedical applications, for example, metal sensing, catalysis, biosensing, bioimaging, drug and gene delivery, and theragnostic applications. Similarly, the well-known properties of silica, such as facile surface functionalization, good biocompatibility, high surface area, and tunable pore volume, have allowed the loading of diverse inorganic and organic moieties and nanoparticles, creating complex hybrid nanostructures that exploit distinct properties (optical, magnetic, metallic, mesoporous, etc.) for sensing, biosensing, bioimaging, diagnosis, and gene and drug delivery. In this context, CDs have been successfully grafted into diverse silica nanostructures through various synthesis methods (e.g., solgel chemistry, inverse microemulsion, surfactant templating, and molecular imprinting technology (MIT)), imparting hybrid nanostructures with multimodal properties for distinct objectives. This review discusses the recently employed synthesis methods for CDs and silica nanoparticles and their typical applications. Then, we focus on combined synthesis techniques of CD-silica nanostructures and their promising biosensing operations. Finally, we overview the most recent potential applications of these materials as innovative smart hybrid nanocarriers and theragnostic agents for the nanomedical field.

Heteroatom-free conjugated tetraphenylethylene polymers for selectively fluorescent detection of tetracycline

The antibiotic tetracycline (Tc) is a major contaminant in food and water, with adverse effects on both ecosystems and human health. The development of novel sensors for tetracycline detection is of great importance. In this work, we develop a novel heteroatom-free conjugated tetraphenylethylene polymer (TPE-CMP) fluorescence sensor for the detection of tetracycline. In the presence of Tc, the emission fluorescence of TPE-CMP was quenched by the photoinduced electron transfer mechanism to achieve high sensitivity. The polymers can detect tetracycline at a concentration of 0-100 μg/mL with a good linear correlation (0.99), and the limit of detection (LOD) is 1.23 μg/mL. Furthermore, TPE-CMP has excellent selectivity in detecting Tc in the presence of various anti-interference analytes, including ions and antibiotics. In addition, the practical feasibilities of TPE-CMP for Tc sensing were further investigated in milk, urine and wastewater samples with satisfactory recoveries (from 94.96% to 112.53% for milk, from 96.41% to 99.31% for urine and from 98.54% to 100.52% for wastewater). We have designed and synthesized TPE-CMP based on heteroatom-free for the specific fluorescence detection of tetracycline, expanding the range of fluorescence detection sensors and offering great promise for practical applications.

A review of the incorporation of QDs and imprinting technology in optical sensors – imprinting methods and sensing responses

This review aims to cover the simultaneous method of using molecularly imprinted technology and quantum dots (QDs) as well as its application in the field of optical sensors.