Smart polymers for the food industry

From Classical to Advanced Use of Polymers in Food and Beverage Applications

Polymers are extensively used in food and beverage packaging to shield against contaminants and external damage due to their barrier properties, protecting the goods inside and reducing waste. However, current trends in polymers for food, water, and beverage applications are moving forward into the design and preparation of advanced polymers, which can act as active packaging, bearing active ingredients in their formulation, or controlling the head-space composition to extend the shelf-life of the goods inside. In addition, polymers can serve as sensory polymers to detect and indicate the presence of target species, including contaminants of food quality indicators, or even to remove or separate target species for later quantification. Polymers are nowadays essential materials for both food safety and the extension of food shelf-life, which are key goals of the food industry, and the irruption of smart materials is opening new opportunities for going even further in these goals. This review describes the state of the art following the last 10 years of research within the field of food and beverage polymer's applications, covering present applications, perspectives, and concerns related to waste generation and the circular economy.

Key aspects of the past 30 years of protein design

Proteins are the workhorse of life. They are the building infrastructure of living systems; they are the most efficient molecular machines known, and their enzymatic activity is still unmatched in versatility by any artificial system. Perhaps proteins' most remarkable feature is their modularity. The large amount of information required to specify each protein's function is analogically encoded with an alphabet of just ∼20 letters. The protein folding problem is how to encode all such information in a sequence of 20 letters. In this review, we go through the last 30 years of research to summarize the state of the art and highlight some applications related to fundamental problems of protein evolution.

Toward a Better Understanding of the Gelation Mechanism of Methylcellulose via Systematic DSC Studies

A methylcellulose (MC) is one of the materials representatives performing unique thermal-responsive properties. While reaching a critical temperature upon heating MC undergoes a physical sol-gel transition and consequently becomes a gel. The MC has been studied for many years and researchers agree that the MC gelation is related to the lower critical solution temperature (LCST). Nevertheless, a precise description of the MC gelation mechanism remains under discussion. In this study, we explained the MC gelation mechanism through examination of a wide range of MC concentrations via differential scanning calorimetry (DSC). The results evidenced that MC gelation is a multistep thermoreversible process, manifested by three and two endotherms depending on MC concentration. The occurrence of the three endotherms for low MC concentrations during heating has not been reported in the literature before. We justify this phenomenon by manifestation of three various transitions. The first one manifests water–water interactions, i.e., spanning water network breakdown into small water clusters. It is clearly evidenced by additional normalization to the water content. The second effect corresponds to polymer–water interactions, i.e., breakdown of water cages surrounded methoxy groups of MC. The last one is related to the polymer–polymer interactions, i.e., fibril hydrophobic domain formation. Not only did these results clarify the MC crosslinking mechanism, but also in the future will help to assess MC relevance for various potential application fields.

Basic concepts and recent advances in nanogels as carriers for medical applications

Nanogels in biomedical field are promising and innovative materials as dispersions of hydrogel nanoparticles based on crosslinked polymeric networks that have been called as next generation drug delivery systems due to their relatively high drug encapsulation capacity, uniformity, tunable size, ease of preparation, minimal toxicity, stability in the presence of serum, and stimuli responsiveness. Nanogels show a great potential in chemotherapy, diagnosis, organ targeting and delivery of bioactive substances. The main subjects reviewed in this article concentrates on: (i) Nanogel assimilation in the nanomedicine domain; (ii) Features and advantages of nanogels, the main characteristics, such as: swelling capacity, stimuli sensitivity, the great surface area, functionalization, bioconjugation and encapsulation of bioactive substances, which are taken into account in designing the structures according to the application; some data on the advantages and limitations of the preparation techniques; (iii) Recent progress in nanogels as a carrier of genetic material, protein and vaccine. The majority of the scientific literature presents the multivalency potential of bioconjugated nanogels in various conditions. Today's research focuses over the overcoming of the restrictions imposed by cost, some medical requirements and technological issues, for nanogels' commercial scale production and their integration as a new platform in biomedicine.

Molecularly imprinted polymer for selective determination of Δ9-tetrahydrocannabinol and 11-nor-Δ9-tetrahydrocannabinol carboxylic acid using LC-MS/MS in urine and oral fluid

The use of molecularly imprinted polymers (MIPs) for solid phase extraction (MISPE) allows a rapid and selective extraction compared with traditional methods. Determination of Δ(9)-tetrahydrocannabinol (THC) and 11-nor-Δ(9)-tetrahydrocannabinol carboxylic acid (THC-COOH) in oral fluid (OF) and urine was performed using homemade MISPEs for sample clean-up and liquid chromatography tandem mass spectrometry (LC-MS/MS). Cylindrical MISPE shaped pills were synthesized using catechin as a mimic template. MISPEs were added to 0.5 mL OF or urine sample and sonicated 30 min for adsorption of analytes. For desorption, the MISPE was transfered to a clean tube, and sonicated for 15 min with 2 mL acetone:acetonitrile (3:1, v/v). The elution solvent was evaporated and reconstituted in mobile phase. Chromatographic separation was performed using a SunFire C18 (2.5 μm; 2.1 × 20 mm) column, and formic acid 0.1% and acetonitrile as mobile phase, with a total run time of 5 min. The method was fully validated including selectivity (no endogenous or exogenous interferences), linearity (1-500 ng/mL in OF, and 2.5-500 ng/mL in urine), limit of detection (0.75 and 1 ng/mL in OF and urine, respectively), imprecision (%CV <12.3%), accuracy (98.2-107.0% of target), extraction recovery (15.9-53.5%), process efficiency (10.1-46.2%), and matrix effect (<-55%). Analytes were stable for 72 h in the autosampler. Dilution 1:10 was assured in OF, and Quantisal™ matrix effect showed ion suppression (<-80.4%). The method was applied to the analysis of 20 OF and 11 urine specimens. This is the first method for determination of THC and THC-COOH in OF using MISPE technology.

Molecularly imprinted polymer beads for nicotine recognition prepared by RAFT precipitation polymerization: a step forward towards multi-functionalities

Molecularly imprinted polymer beads synthesized by RAFT precipitation polymerization enable versatile surface functionalization and new applications.

Molecularly imprinted polymers: present and future prospective

Molecular Imprinting Technology (MIT) is a technique to design artificial receptors with a predetermined selectivity and specificity for a given analyte, which can be used as ideal materials in various application fields. Molecularly Imprinted Polymers (MIPs), the polymeric matrices obtained using the imprinting technology, are robust molecular recognition elements able to mimic natural recognition entities, such as antibodies and biological receptors, useful to separate and analyze complicated samples such as biological fluids and environmental samples. The scope of this review is to provide a general overview on MIPs field discussing first general aspects in MIP preparation and then dealing with various application aspects. This review aims to outline the molecularly imprinted process and present a summary of principal application fields of molecularly imprinted polymers, focusing on chemical sensing, separation science, drug delivery and catalysis. Some significant aspects about preparation and application of the molecular imprinting polymers with examples taken from the recent literature will be discussed. Theoretical and experimental parameters for MIPs design in terms of the interaction between template and polymer functionalities will be considered and synthesis methods for the improvement of MIP recognition properties will also be presented.

Mimicking Biological Delivery Through Feedback-Controlled Drug Release Systems Based on Molecular Imprinting

Intelligent drug delivery systems (DDS) are able to rapidly detect a biological event and respond appropriately by releasing a therapeutic agent; thus, they are advantageous over their conventional counterparts. Molecular imprinting is a promising area that generates a polymeric network which can selectively recognize a desired analyte. This field has been studied for a variety of applications over a long period of time, but only recently has it been investigated for biomedical and pharmaceutical applications. Recent work in the area of molecularly imprinted polymers in drug delivery highlights the potential of these recognitive networks as environmentally responsive DDS that can ultimately lead to feedback controlled recognitive release systems.

Surface imprinted beads for the recognition of human serum albumin

The synthesis of poly-aminophenylboronic acid (ABPA) imprinted beads for the recognition of the protein human serum albumin (HSA) is reported. In order to create homogeneous recognition sites, covalent immobilisation of the template HSA was exploited. The resulting imprinted beads were selective for HSA. The indirect imprinting factor (IF) calculated from supernatant was 1.6 and the direct IF, evaluated from the protein recovered from the beads, was 1.9. The binding capacity was 1.4 mg/g, which is comparable to commercially available affinity materials. The specificity of the HSA recognition was evaluated with competitive experiments, indicating a molar ratio 4.5/1 of competitor was necessary to displace half of the bound HSA. The recognition and binding of the imprinted beads was also tested with a complex sample, human serum and targeted removal of HSA without a loss of the other protein components was demonstrated. The easy preparation protocol of derivatised beads and a good protein recognition properties make the approach an attractive solution to analytical and bio-analytical problems in the field of biotechnology.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Over 1450 references to original papers, reviews and monographs have herein been collected to document the development of molecular imprinting science and technology from the serendipitous discovery of Polyakov in 1931 to recent attempts to implement and understand the principles underlying the technique and its use in a range of application areas. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats. Thereafter, literature describing attempts to apply these polymeric materials to a range of application areas is presented.

Molecular imprinting: a dynamic technique for diverse applications in analytical chemistry

Continuous advances in analyzing complex matrices, improving reliability and simplicity, and performing multiple simultaneous assays with extreme sensitivity are increasing. Several techniques have been developed for the quantitative assays of analytes at low concentrations (e.g., high-pressure liquid chromatography, gas chromatography, immunoassay and the polymerase chain reaction technique). To achieve highly specific and sensitive analysis, high affinity, stable, and specific recognition agents are needed. Although biological recognition agents are very specific and sensitive they are labile and/or have a low density of binding sites. During the past decade molecular imprinting has emerged as an attractive and highly accepted tool for the development of artificial recognition agents. Molecular imprinting is achieved by the interaction, either noncovalent or covalent, between complementary groups in a template molecule and functional monomer units through polymerization or polycondensation. These molecularly imprinted polymers have been widely employed for diverse applications (e.g., in chromatographic separation, drug screening, chemosensors, catalysis, immunoassays etc.) owing to their specificity towards the target molecules and high stability against physicochemical perturbations. In this review the advantages, applications, and recent developments in molecular imprinting technology are highlighted.

Molecularly imprinted materials--receptors more durable than nature can provide

The chapter describes the concept of molecular imprinting. This technology allows the fabrication of artificial polymeric receptors applicable in many areas of biotechnology. Polymers imprinted with selected template molecules can be used as specific recognition elements in sensors or as selective stationary phases in affinity chromatography or in capillary electrochromatography. However, also in solid phase extraction or immunoassays these polymers (MIP) are able to compete with traditional materials such as biological antibodies. Furthermore, polymers molecularly imprinted with so-called transition state analogue templates can be applied as catalysts. In other words, these kind of polymers may be used as artificial antibodies (plastibodies) or biomimicking enzymes (plastizymes). Compared to their biological counterparts, MIP offer different advantages such as simplicity in manufacturing and durability. Thus, the author expects MIP to have a major impact on the whole area of biotechnology.

Non-covalent and semi-covalent molecularly imprinted polymers for selective on-line solid-phase extraction of 4-nitrophenol from water samples

Two molecularly imprinted polymers (MIPs) have been synthesised for the selective extraction of 4-nitrophenol (4-NP) from water samples. One polymer was synthesised via a non-covalent approach and the other via a semi-covalent approach. The selectivity of the polymers for 4-NP was evaluated when these polymers were applied in on-line solid-phase extraction (MISPE) coupled to reversed-phase HPLC. The MISPE conditions for both MIPs were optimised and a clean-up step was included to eliminate non-specific interactions. Differences between the two MIPs were observed with the non-covalent MIP being the more selective of the two, whereas the recoveries were slightly higher for the semi-covalent MIP. The performance of the imprinted polymers in the MISPE of real water samples was also evaluated.

Advanced solid phase extraction using molecularly imprinted polymers for the determination of quercetin in red wine

Solid phase extraction (SPE) based on molecularly imprinted polymers (MIPs) is a novel approach for sample preparation and preconcentration, gaining increased interest in the fields of environmental, clinical, and food analysis. The first application combining MIPs with SPE for advanced beverage analysis is reported. MIPs for the flavonoid quercetin have been generated, using quercetin as a template molecule in a self-assembly approach and yielding imprinting of 1% of the used template. The MIP achieved a capacity of 0.4 g quercetin per gram polymer and a recovery rate of 98.2%. The application of these synthetic receptors as SPE material for the selective extraction and preconcentration of quercetin from synthetic and red wine samples was investigated. Red wine samples from a French Merlot were directly applied onto the SPE cartridge. The collected fractions were analyzed by high-pressure liquid chromatography. For verification of the obtained results, a similarly prepared nonimprinted polymer and a classical octadecyl silane reversed-phase cartridge were applied as the SPE matrix during control experiments. The MIP enabled the selective extraction of quercetin from a complex matrix, such as red wine, spiked with 8.8 mg per liter quercetin, demonstrating the potential of molecularly imprinted solid phase extraction for rapid, selective, and cost-effective sample pretreatment.

Food analyses using molecularly imprinted polymers

Molecular imprinting technology (MIT) is a technique for generating polymers bearing biomimetic receptors. It offers several advantages to the agrofood industry in areas such as analysis, sensoring, extraction, or preconcentration of components. It has the potential of becoming a tool for acquiring truly simple, rapid, and robust direct measurements. In this review, the special features of MIT that have bearing on food science and technology are highlighted.

Towards the rational design of molecularly imprinted polymers

Efforts to elucidate the mechanisms underlying the formation of binding sites in molecularly imprinted polymers (MIPs) and of MIP-ligand binding events are presented in the context of a thermodynamic treatment of MIP recognition phenomena.

Synthesis and catalysis by molecularly imprinted materials

Molecularly imprinted materials have been demonstrated to possess a very high degree of selectivity towards targeted substrates. In addition to such tailor-made molecular recognition, progress has been made in introducing reactive groups into the recognition sites. Putting teeth into imprinted matrices is one method of making true enzyme mimics or plastizymes, which are plastic polymer enzyme mimics.

Imprinted polymers as tools for the recovery of secondary metabolites produced by fermentation

Imprinted polymers were synthesized using a mixture of pigments, N-glutamyl-rubropuctamine, and N-glutamyl-monascorubramine (I) as the template, and 2-methacrylamido-6-picoline or 4-aminostyrene as functional monomers, to obtain recognition materials capable of forming hydrogen bonds and charge interactions, respectively, with carboxyl groups of target I in the binding sites. The polymers were prepared thermally at a template loading of 5 mol% using ethylene-glycol dimethacrylate or trimethylolpropane trimethacrylate as crosslinkers and acetonitrile or tetrahydrofuran as porogens. The selective binding of I to both types of polymer was demonstrated, although aminostyrene-based materials showed higher overall adsorption and were studied in more detail. It was shown that the kinetics of binding of I from ethyl-acetate extracts of fermented Monascus sp. was very rapid and virtually all the pigment adsorbed can be released by washing the polymer with ethanol-water mixtures. The feasibility of reusing imprinted polymer in consecutive adsorption/desorption cycles was also demonstrated. Copyright 1999 John Wiley & Sons, Inc.

Separation and sensing based on molecular recognition using molecularly imprinted polymers

Molecular recognition-based separation and sensing systems have received much attention in various fields because of their high selectivity for target molecules. Molecular imprinting has been recognized as a promising technique for the development of such systems, where the molecule to be recognized is added to a reaction mixture of a cross-linker(s), a solvent(s), and a functional monomer(s) that possesses a functional groups(s) capable of interacting with the target molecule. Binding sites in the resultant polymers involve functional groups originating from the added functional monomer(s), which can be constructed according to the shape and chemical properties of the target molecules. After removal of the target molecules, these molecularly imprinted complementary binding sites exhibit high selectivity and affinity for the template molecule. In this article, recent developments in molecularly imprinted polymers are described with their applications as separation media in liquid chromatography, capillary electrophoresis, solid-phase extraction, and membranes. Examples of binding assays and sensing systems using molecularly imprinted polymers are also presented.