Casein-based conjugates and graft copolymers. Synthesis, properties, and applications.

Biobased natural polymers, including polymers of natural origin such as casein, are growing rapidly in the light of the environmental pollution caused by many mass-produced commercial synthetic polymers. Although casein has interesting intrinsic properties, especially for the food industry, numerous chemical reactions have been carried out to broaden the range of its properties, most of them preserving casein's nontoxicity and biodegradability. New conjugates and graft copolymers have been developed especially by Maillard reaction of the amine functions of the casein backbone with the aldehyde functions of sugars, polysaccharides, or other molecules. Carried out with dialdehydes, these reactions lead to the cross-linking of casein giving three-dimensional polymers. Acylation and polymerization of various monomers initiated by amine functions are also described. Other reactions, far less numerous, involve alcohol and carboxylic acid functions in casein. This review provides an overview of casein-based conjugates and graft copolymers, their properties, and potential applications.

Synthesis of a New Poly(ε-caprolactone)-g-Chitosan Amphiphilic Graft Copolymer with a "Reverse" Structure.

Hydrophilic chitosan (CHT) and hydrophobic polyε-caprolactone (PCL) are well-known biocompatible and biodegradable polymers that have many applications in the biomedical and pharmaceutical fields. But the mixtures of these two compounds are considered incompatible, which makes them not very interesting. To avoid this problem and to further extend the properties of these homopolymers, the synthesis of a new graft copolymer, the fully biodegradable amphiphilic poly(ε-caprolactone-g-chitosan) (PCL-g-CHT) is described, with an unusual "reverse" structure formed by a PCL backbone with CHT grafts, unlike the "classic" CHT-g-PCL structure with a CHT main chain and PCL grafts. This copolymer is prepared via a copper-catalyzed 1,3-dipolar Huisgen cycloaddition between propargylated PCL (PCL-yne) and a new azido-chitosan (CHT-N3 ). In order to obtain an amphiphilic copolymer regardless of the pH, chitosan oligomers, soluble at any pH, are prepared and used. The amphiphilic PCL-g-CHT copolymer spontaneously self-assembles in water into nanomicelles that may incorporate hydrophobic drugs to give novel drug delivery systems.

Poly(ε-caprolactone)-Based Graft Copolymers: Synthesis Methods and Applications in the Biomedical Field: A Review.

Synthetic biopolymers are attractive alternatives to biobased polymers, especially because they rarely induce an immune response in a living organism. Poly ε-caprolactone (PCL) is a well-known synthetic aliphatic polyester universally used for many applications, including biomedical and environmental ones. Unlike poly lactic acid (PLA), PCL has no chiral atoms, and it is impossible to play with the stereochemistry to modify its properties. To expand the range of applications for PCL, researchers have investigated the possibility of grafting polymer chains onto the PCL backbone. As the PCL backbone is not functionalized, it must be first functionalized in order to be able to graft reactive groups onto the PCL chain. These reactive groups will then allow the grafting of new reagents and especially new polymer chains. Grafting of polymer chains is mainly carried out by "grafting from" or "grafting onto" methods. In this review we describe the main structures of the graft copolymers produced, their different synthesis methods, and their main characteristics and applications, mainly in the biomedical field.

Poly(Lactic Acid)-Based Graft Copolymers: Syntheses Strategies and Improvement of Properties for Biomedical and Environmentally Friendly Applications: A Review.

As a potential replacement for petroleum-based plastics, biodegradable bio-based polymers such as poly(lactic acid) (PLA) have received much attention in recent years. PLA is a biodegradable polymer with major applications in packaging and medicine. Unfortunately, PLA is less flexible and has less impact resistance than petroleum-based plastics. To improve the mechanical properties of PLA, PLA-based blends are very often used, but the outcome does not meet expectations because of the non-compatibility of the polymer blends. From a chemical point of view, the use of graft copolymers as a compatibilizer with a PLA backbone bearing side chains is an interesting option for improving the compatibility of these blends, which remains challenging. This review article reports on the various graft copolymers based on a PLA backbone and their syntheses following two chemical strategies: the synthesis and polymerization of modified lactide or direct chemical post-polymerization modification of PLA. The main applications of these PLA graft copolymers in the environmental and biomedical fields are presented.

Is artemisinin the only antiplasmodial compound in the Artemisia annua tea infusion? An in vitro study.

In our ongoing investigation into Artemisia annua for the treatment of malaria, we decided to study the possibility that synergism might enhance the efficacy of artemisinin. Our main objective was to test tea infusions and nonpolar extracts prepared from different A. annua varieties against Plasmodium falciparum in vitro in order to determine if synergism will increase the effectiveness of artemisinin in the samples as compared to pure artemisinin. We found that the IC50 of artemisinin in the tea and nonpolar extracts was not significantly different to the IC50 of pure artemisinin. We could show that the year and country of harvest or storage conditions did not have any influence on the activity and that it narrowly followed the concentration of artemisinin in all the extracts. In conclusion, based on these in vitro results, artemisinin seems to be the only active antiplasmodial compound in A. annua.

Experimental assessment of an innovative process for simultaneous PAHs and Pb removal from polluted soils.

This paper tests a soil washing process using flotation in its effectiveness for the removal of both polycyclic aromatic hydrocarbons (PAHs) and Pb from three polluted soils (soils A, B and C). The optimal flotation conditions were defined as: pulp density=10%, Cocamidopropylhydroxysultaine (CAS)=0.2% ww(-1), [NaCl]=5.5M, pH=3, flotation time=15 min, air flow rate=3l min(-1), stirring speed=1800 rpm and temperature=20 degrees C. Under these conditions, successive flotation stages (n), decreased the contaminant content to below permitted levels (up to 90% PAHs and Pb removal). Thus, a more contaminated matrix required the addition of a growing number of successive flotation stages to lower contamination levels below legal thresholds. While PAHs were distributed within the solid fractions of the process, Pb was mainly present in the liquid fractions. Electrodeposition allowed a total recovery of Pb after 60 min using a 2A electrical current.