Sucrose Polymer Overview

Sucrose is a disaccharide with a unique structure. It is a non-reducing sugar formed by removing a molecule of water from the glycoside hydroxyl group of a molecule of α-D-(+)-glucopyranose and a molecule of β-D-(-)-fructofuranose. During the hydrolysis process, the specific optical rotation of sucrose gradually changes from dextrorotatory to levorotatory, so the hydrolysis of sucrose is also commonly referred to as a conversion reaction. There are 8 chemically active hydroxyl groups and glycosidic bonds in the sucrose molecule, through which these groups can theoretically undergo oxidation, reduction, decomposition, esterification, polycondensation, etherification, substitution, degradation, etc. with other compounds or itself. This reaction provides the possibility to form a wide variety of sucrose polymers. In addition, many valuable sucrose derivatives can also be obtained through enzyme engineering and fermentation engineering. The following is an introduction to the recent major sucrose polymer products.

Sucrose-based Hydrogels

At present, the most widely used sucrose-based polymers are sucrose-based hydrogels. Sucrose-based hydrogels refer to a class of hydrogel materials synthesized from sucrose, which are mainly used in the field of biomedicine. A hydrogel can be defined as a cross-linked polymer that can swell in water and retain a large amount of water without dissolving it. Because the polymer network is filled with a lot of water, the whole material has a fluid property, which is very similar to the body tissue filled with a lot of aqueous liquid. The soft, wet surface of the hydrogel and its affinity for tissue greatly reduces the material’s irritation to surrounding tissues, making the polymer good biocompatibility. Hydrophilic small molecules are able to diffuse in the hydrogel. Since the 1940s, researches on the synthesis, physicochemical properties and application of hydrogels in biochemistry, medicine and other fields have been very active.

There are three preparation methods for hydrogels, such as monomer polymerization and cross-linking, polymer cross-linking and graft copolymerization of carrier. Hydrogels can be obtained by polymerizing and crosslinking one or more monomers using ionizing radiation, ultraviolet radiation, or chemical initiation. Generally, a small amount of cross-linking agent needs to be added during the formation of the hydrogel. There are two types of hydrogels prepared from polymers: physical crosslinking and chemical crosslinking. Physical crosslinks are formed by physical forces such as electrostatic interactions, ionic interactions, hydrogen bonding, entanglement of chains, and the like. Chemical crosslinking is the addition of a crosslinking agent to an aqueous polymer solution. The best way to synthesize hydrogels from polymers is radiation cross-linking. The so-called radiation cross-linking means that the polymer is irradiated so that the main chain linear molecules are connected by chemical bonds. Many water-soluble polymers can be prepared for hydrogels by irradiation, such as PVA, Poly-NIPAAM, polyvinylpyrrolidone (PVP), polyacrylic acid (PAAc), polyacrylamide (PAAM), polyoxyethylene (PEO), polyvinylpyrrolidone (PVP) Hydroxyethyl methacrylate (PHEMA), etc. Synthesis of hydrogel by radiation method does not need to add initiator, and the product is purer. The mechanical strength of the hydrogel is generally poor. In order to improve the mechanical strength of the hydrogel, the hydrogel can be attached to a carrier with a certain strength. The generation of free radicals on the support surface is the most efficient technique for preparing grafted hydrogels, and the monomers can be covalently attached to the support.

Ficoll

Ficoll is a typical sucrose polymer, which is prepared by polymerization under alkaline conditions using sucrose as raw material and epichlorohydrin as a cross-linking agent. It is a water-soluble white powdery polymer with a particle size of about 10nm in solution and can be stored at room temperature. At present, ficoll with trade names of Ficoll400 and Dormacoll has been widely used as a density gradient agent and therapeutic agent for cell separation; researchers have made ficoll and other water-soluble degradable polymers into polymer matrix, which are used as the controlled release system of vaccines. Experiments show that the protective layer formed by ficoll makes the vaccine microspheres more resistant to enzymatic degradation. Scientists have used ficoll as a vaccine adjuvant and found that it has good stability and is also very helpful to vaccines (for example, it is better than the previously used mineral oil-based adjuvant). In addition, some researchers have used ficoll as a new type of intestinal polymer permeability marker by taking advantage of its water-soluble, non-toxic, spherical, and resistance to intestinal enzymes, and its molecular weight distribution is similar to that of proteins in food.

Applications of Sucrose-Based Polymers

The main areas of application for sucrose-based polymers focus on drug release formulations.

In the field of drug release, the hydrophilicity of drug carrier materials is an important factor affecting drug efficacy. The so-called drug efficacy refers to the following effects after drug use: eliminating pathogenic microorganisms that invade the body, such as cells and viruses; Substances neutralize or decompose and make them non-toxic; inhibit and kill malignant cells such as cancer; activate weakened immune cells; supplement necessary substances that are gradually decreasing or inhibit allergic physiological substances; promote regeneration of damaged tissues. In order to exert the drug effect and ensure the dissolution and dispersion of the drug in intracellular and extracellular fluids, the carrier material needs to have good hydrophilicity. Sucrose-based polymers have become ideal raw materials for carriers due to their advantages of good hydrophilicity, non-toxicity, good biocompatibility and simple production process. The researchers focused on the reticular skeleton structure of ficoll acrylate hydrogels. This hydrogel is prepared by a chemoenzymatic method, that is, sucrose acrylate is synthesized by an enzymatic method, and then a macroporous hydrophilic matrix is ​​directly obtained by free radical polymerization. The substrate contains a polyacrylic acid backbone that is shielded by the ester pendant groups of the sugar. This shielding structure can give these materials better biocompatibility, which suggests that it is suitable for a variety of biomedical applications. The researchers focused on the release kinetics of bovine serum albumin and γ-globulin in sucrose-based polymer hydrogels with different initial monomer concentrations. All these gels have common characteristics when released. The study found an initial large release of protein in the first 25 hours, followed by a long-term sustained release (>500 hours). This indicates that the sucrose-based polymer hydrogel is a very effective sustained release agent.