In this work, the synthesis of gallic acid-chitosan and catechin-chitosan conjugates was carried out by adopting a free radical-induced grafting procedure. For this purpose, an ascorbic acid/hydrogen peroxide redox pair was employed as radical initiator. The formation of covalent bonds between antioxidant and biopolymer was verified by performing UV, FT-IR, and DSC analyses, whereas the antioxidant properties of chitosan conjugates were compared with that of a blank chitosan, treated in the same conditions but in the absence of antioxidant molecules. The good antioxidant activity shown by functionalized materials proved the efficiency of the reaction method.

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A novel, simple, and cheap method to synthesize antioxidant-protein conjugates by grafting reaction was developed employing a hydrogen peroxide-ascorbic acid pair as radical initiator system. Our challenge was to covalently bind molecules with tested antioxidant activity, as gallic acid (GA) and catechin (CT) to a biomacromolecule, as gelatin, extensively used in the pharmaceutical, cosmetic, and food industry. In this way, two gelatin conjugates, bearing GA and CT covalently bounded to a side chain of protein, were synthesized. Calorimetric, UV-vis, and fluorescence analyses were performed to verify the covalent bond between antioxidant molecules and gelatin, and the antioxidant activity of conjugates was compared to that of a control polymer submitted to the same reaction conditions without antioxidant molecule. The ability of synthesized materials to inhibit 2,2'-diphenyl-1-picrylhydrazyl, hydroxyl radicals, and linoneic acid peroxidation was determined and, to well characterized antioxidant properties of grafted biomacromolecules, disposable phenolic equivalents and total antioxidant activity were calculated. The conjugates showed a good antioxidant activity, confirming the efficiency of the synthetic strategy proposed in this paper. The results clearly showed that antioxidant moieties covalently bounded to a natural polymer allow to introduce in the macromolecule peculiar features for specific industrial applications.

Abstract:In agricultural field, polymers are widely used for many applications. Although they were used, in the first time, just as structural materials (inhert polymers), in the last decades functionalized polymers revolutionized the agricultural and food industry with new tools for several applications. Smart polymeric materials and smart delivery systems helped the agricultural industry to combat viruses and other crop pathogens, functionalized polymers were used to increase the efficiency of pesticides and herbicides, allowing lower doses to be used and to indirectly protect the environment through filters or catalysts to reduce pollution and clean-up existing pollutants. This report will review the key aspects of used polymers in agricultural area, highlighting current research in this field and the future impacts they may have.

Molecular imprinting is an efficient technique for introducing regions with a highly specific molecular arrangement into a polymeric matrix. The first example of a molecularly imprinted polymer (MIP) was reported half a century ago; however, the use of molecular imprinting has become a well established practical tool only in the last decade. Recently, MIPs are widely used, for example, in chromatographic applications or enzyme antibody mimics. MIPs have also been used in biological applications such as drug delivery systems (DDS), and they have also been successfully applied as excipients in controlled delivery systems. Their huge potential could bring about intelligent drug release; this refers to the release, in a predictable way, of therapeutic agents in response to specific environmental stimuli (the presence of another molecule, pH changes, temperature, etc.). This review is focused on particular intelligent devices of this type that exhibit selective recognition (traps for toxic molecules) and release (of drugs in order to prolong the duration of pharmacological action) in response to specific stimuli. The "stimuli-responsive molecularly imprinted polymers" reviewed in this paper are expected to contribute significantly to the exploration and development of new generations of intelligent and self-regulated drug delivery systems.