Hydroxypropylcellulose is a water-soluble non-ionic cellulose ether, a semi-crystalline polymer with very low glass transition amorphous polymer domains along with crystalline domains and obtained by chemical reaction of the hydroxyl groups at the 2, 3 and/or 6 positions of the cellulose glucose residues.
The name defines the structure of the molecule:
- Hydroxypropyl refers to a group derived from propylene, a three-carbon alkene, with an attached hydroxyl (-OH) group.
- Cellulose refers to a type of polysaccharide that is the main component of plant cell walls. Cellulose is a large molecule consisting of many smaller glucose units linked together.
The synthesis process takes place in several stages:
- Cellulose purification. The first step in the synthesis of HPC is the purification of cellulose, derived from plant sources. This involves the removal of impurities such as lignin, hemicellulose and other components.
- Alkaline treatment. Purified cellulose is treated with an alkali, sodium hydroxide. This process, known as mercerization, increases the reactivity of cellulose by breaking down its crystalline structure.
- Reaction to propylene oxide. The alkali-treated cellulose is reacted with propylene oxide. This introduces hydroxypropyl groups (-CH2CHOHCH3) on the cellulose molecule. The degree of substitution, or the average number of hydroxypropyl groups connected to each unit of glucose in cellulose, can be controlled by adjusting the reaction conditions.
- Neutralization and washing. After the reaction, the mixture is neutralized, usually with an acid such as hydrochloric acid. The product is then washed to remove unreacted reagents and by-products.
- Drying and grinding process. The wet mass is then dried and ground into a fine powder to produce the final product, hydroxypropylcellulose.
- Quality control. The final product is then tested to ensure it meets the required specifications. This may involve testing for parameters such as degree of replacement, viscosity, and moisture content.
It appears in the form of a white powder.
What it is used for and where
Medical
In the pharmaceutical industry, it is used for its biocompatibility as a drug carrier, emulsion stabilizer, binder, thickener. In particular, since hydroxypropylcellulose exhibits organic and water solubility, it is suitable for solvent methods of drug release to produce solid dispersions. At low viscosity, hydroxypropylcellulose is an excellent pharmaceutical excipient. Due to its bioadhesive and hydrophilic properties it can be mainly used in topical and oral pharmaceutical formulations.
It affects the solubility, dissolution and oral bioavailability of drugs (1).
This study reports the behavior of hydroxypropylcellulose and carrageenan used in ophthalmics for use in cataract surgery due to their viscoelastic properties (2).
To reduce intraoperative and postoperative complications after surgery, Hydroxypropylcellulose was added in order to prepare a submucosal injection agent that can gel during endoscopic mucosal dissection and adhere to the wound surface (3).
Hydroxypropylcellulose was used as an artificial ligament coating in a case of anterior cruciate ligament injury and significantly improved the regeneration of ligamentous tissue. hydroxypropylcellulose coating can significantly improve the cytocompatibility and graft-to-bone healing of a polyethylene terephthalate artificial ligament for anterior cruciate ligament reconstruction (4).
Food
Ingredient on the European food additives list as E463, stabiliser, thickener.
Cosmetics
Binder agent. Ingredient that is used in cosmetic, food and pharmaceutical products as an anti-caking agent with the function of making the product in which it is incorporated silky, compact and homogenous. The binder, either natural such as mucilage, gums and starches or chemical, may be in the form of a powder or liquid.
Emulsion stabilizer. Emulsions are thermodynamically unstable. Emulsion stabilisers improve the formation and stability of single and double emulsions. It should be noted that in the structure-function relationship, molar mass plays an important role.
Film-forming agent. It produces a continuous ultra-thin film with an optimal balance of cohesion, adhesion and stickiness on the skin or hair to counteract or limit damage from external phenomena such as chemicals, UV rays and pollution.
Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable and are used to soothe or soften the skin and emulsify, so they need a specific, stabilising ingredient. This ingredient forms a film, lowers the surface tension and makes two immiscible liquids miscible. A very important factor affecting the stability of the emulsion is the amount of the emulsifying agent. Emulsifiers have the property of reducing the oil/water or water/oil interfacial tension, improving the stability of the emulsion and also directly influencing the stability, sensory properties and surface tension of sunscreens by modulating the filmometric performance.
Viscosity control agent. It controls and adapts viscosity to the required level for optimal chemical and physical stability of the product and dosage in gels, suspensions, emulsions, solutions.
The most relevant studies on this ingredient have been selected with a summary of their contents:
Hydroxypropylcellulose studies
- Molecular Formula: C12H20N2
- Molecular Weight: 192.30
- CAS: 9004-64-2
- UNII
- EC Number: 265-995-8
- DSSTox Substance ID:
- MDL number MFCD00132688
- PubChem Substance ID
- NACRES NA.24
Synonyms :
- Cellulose, hydroxypropyl ether
- Hydroxypropyl cellulose
- HPC
References_______________________________________________________________________
(1) Rashid R, Kim DW, Din FU, Mustapha O, Yousaf AM, Park JH, Kim JO, Yong CS, Choi HG. Effect of hydroxypropylcellulose and Tween 80 on physicochemical properties and bioavailability of ezetimibe-loaded solid dispersion. Carbohydr Polym. 2015 Oct 5;130:26-31. doi: 10.1016/j.carbpol.2015.04.071.
(2) Jones DS, Rafferty GP, Andrews GP. Design of binary polymeric platforms containing ɩ-carrageenan and hydroxypropylcellulose for use in cataract surgery. Carbohydr Polym. 2016 Dec 10;154:296-304. doi: 10.1016/j.carbpol.2016.06.042.
(3) Tang B, Shan J, Yuan T, Xiao Y, Liang J, Fan Y, Zhang X. Hydroxypropylcellulose enhanced high viscosity endoscopic mucosal dissection intraoperative chitosan thermosensitive hydrogel. Carbohydr Polym. 2019 Apr 1;209:198-206. doi: 10.1016/j.carbpol.2018.12.103.
(4) Yang J, Dong Y, Wang J, Chen C, Zhu Y, Wu Y, Zhang P, Chen T, Zhou W, Wu P, Thanh NTK, Ngoc Quyên Trân, Chen J, Chen S. Hydroxypropylcellulose Coating to Improve Graft-to-Bone Healing for Anterior Cruciate Ligament Reconstruction. ACS Biomater Sci Eng. 2019 Apr 8;5(4):1793-1803. doi: 10.1021/acsbiomaterials.8b01145.
Hydroxypropylcellulose 
