Background of β-cyclodextrin
β-Cyclodextrin (β-CD) has attracted widespread attention due to its good biocompatibility and biodegradability. With the wide application of β-cyclodextrin, the modification of β-cyclodextrin has also received attention. Under the action of cyclodextrin glycosyltransferase produced by Bacillus, cyclodextrin is the general name for a series of cyclic oligosaccharides containing 6 to 12 D-glucopyranoside units connected through 1,4-glycosidic bonds produced by amylose, includes three types of cyclodextrins: α-, β-, and γ-. The white powdery β-cyclodextrin structure contains many hydroxyl groups, making it highly polar. Its solubility in ethyl acetate, ether, ethanol, and methanol is very small, and its solubility in dimethyl sulfoxide, N, N -Easily soluble in highly polar solvents such as dimethylformamide and pyridine.
Figure 1. Structural characteristics of β-cyclodextrin. (Maria Chatzidaki, et al.; 2020)
β-Cyclodextrin has many advantages: (1) It has good emulsification and dispersion properties; (2) It can reduce volatilization, reduce toxicity, and improve solubility; (3) It can prevent moisture, moisturize, and prolong the effectiveness of preparations. Research has found that large closed hydrogen bonding bands are formed between adjacent hydroxyl groups in the β-cyclodextrin molecule. Although free hydroxyl groups are also present, the solubility in water is very low compared with the other two cyclodextrins. In addition, β-cyclodextrin exists stably in alkaline solutions, and part of β-cyclodextrin will be hydrolyzed into a series of acyclic maltose and glucose series under acidic conditions. β-Cyclodextrin does not have a clear melting point, but it begins to decompose when the temperature rises to 200°C. β-cyclodextrin can be extracted from natural polymer materials. It has many advantages, such as wide sources, low toxicity, low production cost, and biodegradability. And because of its special structure of hydrophilic on the outside and hydrophobic on the inside, it can be modified properties, in order to obtain better characteristics and greatly improve the application effect. As a clean and green carrier material, β-cyclodextrin has the advantages of being non-toxic, odorless and harmless to the human body, and is widely used in medicine, food, water treatment and other fields.
Research on Modification of β-cyclodextrin
The modification of β-cyclodextrin refers to the introduction of new substituents or functional groups on its hydroxyl group under the condition that the macromolecule skeleton of β-cyclodextrin remains basically unchanged and the cavity structure has good accommodation performance, so that β-cyclodextrin Cyclodextrin has better properties and functions. The modification of β-cyclodextrin can be divided into more complicated and cumbersome enzymatic methods, chemical methods and physical methods. Here we mainly introduce chemical grafting and cross-linking, as well as physical blending.
Chemical grafting is a chemical reaction between the reactive group of the reactant and the grafted monomer or macromolecular chain, thereby achieving chemical grafting. In order to improve the properties of chemical substances, most materials are modified to improve their properties. Because the structure of β-cyclodextrin is hydrophobic inside and hydrophilic outside, it is widely used to improve its hydrophobicity. β-cyclodextrin is grafted onto silica gel, chitosan, etc., which can be used for adsorption in water treatment. In addition, β-cyclodextrin grafted onto polyester fiber can improve its hydrophilicity.
Some researchers prepared a folic acid-grafted β-CD complex and characterized the product through ultraviolet, electron microscopy and laser particle size analyzer. They found that the synthesized complex was spherical and evenly dispersed, with an average particle size of (157. 8±8.9) nm. In addition, someone grafted β-CD and L-glutamic acid to finally synthesize β-CD-g-poly-L-glutamic acid complex. Through experimental data analysis, it was found that the solid content of the hydrogel is one of the factors that affects its properties. Important factors, as its content increases, not only shortens the gelation time of β-CD-g-poly-L-glutamic acid, improves its mechanical strength, but also slows down its degradation rate and reduces its swelling degree.
Blending modification refers to a macroscopically uniform and continuous solid polymer material formed by mixing two or more polymers together through physical methods. Ionically branched β-CD was obtained through the condensation polymerization of β-CD monomers and mixed with poly(L-lactide) (PLLA) to develop poly(L-lactide)/branched β-CD co-mixture (PLLA/bβ-CD). Through analysis, it was found that there are separate single phases in the blend, and by changing the ratio of the two, different characteristics of the material can be obtained. This work opens new prospects for the development of natural polymer materials with tunable functional properties.
Application of β-cyclodextrin Particles
In recent years, with the continuous development of nanomaterials, research on targeted controlled release of drugs has received widespread attention. The emerging β-cyclodextrin nanoparticles have good biocompatibility and degradability. They use β-cyclodextrin to react with small molecular substances and then graft them with magnetic particles. They can be used in drug delivery, medical treatment, environmental protection, etc. fields are widely used.
Composite materials composed of β-cyclodextrin, magnetic Fe3O4, and other small molecule substances can be used in areas such as targeted therapy, drug delivery, and medical testing. The carboxyl-modified β-cyclodextrin was grafted onto the surface of aminated Fe3O4-loaded polyester fabric, and menthol was included in the β-cyclodextrin cavity. By characterizing its drug-loading performance, it was found that the polyester appearance There is no obvious change, but there are obvious cracks between the polyester fibers, and some small particles appear; the compound elements do not change before and after inclusion; the particles show weak magnetism, and the inclusion effect is very good, the drug can be released slowly, and has good Prospects. The researchers prepared pH-sensitive composite micelles of chitosan grafted β-cyclodextrin (CS-g-CD) and poly(ε-caprolactone) (BM-PCL) terminated with benzimidazole, using to control drug release. The composite micelle has a core-shell structure. The core is formed by BM-PCL and CD through host-guest interaction, and the shell is formed by chitosan chains. Doxorubicin (DOX) is a model anticancer drug that is efficiently loaded into complex micelles through hydrophobic interactions. Experimental results show that the DOX encapsulation rate reaches 75%. The release experiments of DOX in micelles show that the release is inhibited in neutral pH solutions and accelerated in acidic solutions and high temperatures. Such pH-sensitive micelles may have potential applications in the delivery of anticancer drugs using smart nanocarriers.
References
- Maria Chatzidaki, et al.; β-Cyclodextrin as carrier of novel antioxidants: A structural and efficacy study. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2020, Volume 603:125262.
- Sahu KM, et al.; Host-guest drug delivery by β-cyclodextrin assisted polysaccharide vehicles: A review. Int J Biol Macromol. 2023, 240:124338.
