Solubilizer, in a broad sense, refers to the addition of a substance to the system to accelerate the dissolution of the substance to be dissolved into the solvent or to increase the solubility of the insoluble substance in the solvent. The solubilization mechanism of solubilizer mainly depends on the intermolecular force or intermolecular reversible binding, so the extraction process will not affect the structure and biological activity of the solute. The selection of solubilizer can be made according to the structural characteristics, physicochemical properties and other properties of the compounds. The common solubilization includes complexation, association, latent solubilization, solubilization of surfactants and so on. At present, solubilizer is widely used in the preparation, food industry, dye dyeing, medicine extraction and other fields.

Applications:

Solubilizer can effectively accelerate the dissolution of substances into solvents or increase the solubility of insoluble substances in solvents, so it is widely used in toothpaste, dental cleaners, disinfectants and other products. In addition, solubilizer is also widely used in the solubilization of insoluble drugs, such as "cresol soap solution". Other organic compounds, such as oil-soluble vitamins, hormones, antibiotics, alkaloids, volatile oils and so on, can be solubilized to obtain high concentration clarification or clear solutions suitable for treatment, which can be used for external use, internal administration, intramuscular or subcutaneous injection, etc. Among all the solubilizers, polysorbate is the most widely used, which can solubilize both non-polar compounds and compounds containing polar groups.

Figure 1. Polysorbate 20.

Classification:

• Cationic type: The main part of the cationic solubilizer structure is a pentavalent nitrogen atom, represented by quaternary ammonium salts, which is characterized by high water solubility, good surface activity and strong disinfection and sterilization. Such as bromobenzylammonium (bromogeramine).
• Anionic type: The surface-active part of anionic solubilizer is an anion, which is generally used in topical preparations because of its strong physiological effects, such as hemolysis, irritation and so on. Such solubilizers include soaps, sulfates (such as sodium dodecyl sulfate), sulfonates (such as sodium dodecylbenzene sulfonate, sodium taurocholate) and so on.

Figure 2. Sodium lauryl sulfate.

• Amphoteric ion type: Zwitterionic solubilizer molecules have both cationic and anionic atomic groups, cations are mainly quaternary ammonium salts, and anions are mainly carboxylic acid, sulfonic acid, phosphoric acid, sulfate and other atomic groups. This kind of solubilizer has the property of anionic surfactant in alkaline aqueous solution with the good foaming ability and strong decontamination power. It has the property of cationic surfactant in acidic aqueous solution and has strong bactericidal power.

Figure 3. Amphoteric conjugated polyelectrolyte solubilizers prepared high-quality perovskite films.

• Nonionic type: The nonionic solubilizer does not dissociate in water, the hydrophilic groups in the molecules are polyols and their polymers, and the lipophilic groups are composed of various higher fatty acids or higher fatty alcohols and alkyl or aryl groups. They combine with hydrophilic groups by ester or ether bonds, and there are many different varieties. Due to the chemical in dissociation, this kind of solubilizer is not easily affected by electrolytes and pH value of the solution and has less toxicity and hemolysis. It is the most widely used at present and can be used for internal administration, external use, injection and other dosage forms. Nonionic solubilizers are mainly divided into the following four categories: (1) polyoxyethylene dehydrated sorbitol fatty acid esters (polysorbate), such as polysorbate 80. (2) polyoxyethylene fatty acid esters (sellers), such as polyoxyethylene Laurate. (3) polyoxyethylene fatty acid alcohol ethers (benzyl esters), such as Pingjia O. (4) polyoxyethylene polyoxypropylene copolymers, such as Poloxamer.

References:

1. Xu Yanli. (2003) “The function of surfactant.” Daily Chemical Industry Information. (14): 18-18.