Hydroxypropyl cellulose

HPC is an ether of cellulose in which some of the hydroxyl groups in the repeating glucose units have been hydroxypropylated forming -OCH₂CH(OH)CH₃ groups using propylene oxide. The average number of substituted hydroxyl groups per glucose unit is referred to as the degree of substitution (DS). Complete substitution would provide a DS of 3. Because the hydroxypropyl group added contains a hydroxyl group, this can also be etherified during preparation of HPC. When this occurs, the number of moles of hydroxypropyl groups per glucose ring, moles of substitution (MS), can be higher than 3.

Because cellulose is very crystalline, HPC must have an MS about 4 in order to reach a good solubility in water. HPC has a combination of hydrophobic and hydrophilic groups, so it has a lower critical solution temperature (LCST) at 45 °C. At temperatures below the LCST, HPC is readily soluble in water; above the LCST, HPC is not soluble.

HPC forms liquid crystals and many mesophases according to its concentration in water. Such mesophases include isotropic, anisotropic, nematic and cholesteric. The last one gives many colors such as violet, green and red.{{cite journal |last1=Barty-King |first1=Charles |last2=Chan |first2=Chun Lam Clement |last3=Parker |first3=Richard |last4=Bay |first4=Mélanie |last5=Vadrucci |first5=Roberto |last6=De Volder |first6=Michael |last7=Vignolini |first7=Silvia |title=Mechanochromic, Structurally Colored, and Edible Hydrogels Prepared from Hydroxypropyl Cellulose and Gelatin |journal=Advanced Materials |date=29 July 2021 |volume=33 |issue=37 |page=2102112 |doi=10.1002/adma.202102112 |pmid=34323315 |bibcode=2021AdM....3302112B |s2cid=236497081 |url=https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202102112|pmc=11468689 }}

Lacrisert, manufactured by Aton Pharma, is a formulation of HPC used for artificial tears. It is used to treat medical conditions characterized by insufficient tear production such as keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis. HPC is also used as a lubricant for artificial eyes.{{cite journal |vauthors=Luchs J, Nelinson D, Macy J | title = Efficacy of hydroxypropyl cellulose inserts (LACRISERT®) in subsets of patients with dry eye syndrome (DES): Findings from a patient registry | journal = Cornea | date = December 2010 | volume = 29 | issue = 12 | pages = 1417–1427| pmid = 20847657 | doi = 10.1097/ICO.0b013e3181e3f05b | s2cid = 40120861 }}{{cite journal |author1=McDonald M |author2=D’Aversa G |author3=Perry D |author4=Wittpenn J |author5=Nelinson D | title = Correlating patient-reported response to Hydroxypropyl cellulose ophthalmic insert (LACRISERT®) therapy with clinical outcomes: tools for predicting response | journal = Curr Eye Res | date = Oct 2010 | volume = 35 | issue = 10 | pages = 880–887| pmid = 20858108 | doi = 10.3109/02713683.2010.495811 |s2cid=207450381 }}{{cite journal |vauthors=Koffler B, McDonald M, Nelinson D | title = Improvement in clinical signs, symptoms, and QoL associated with DES: Hydroxypropyl Cellulose Ophthalmic Insert Patient Registry | journal = Eye & Contact Lens | date = May 2010 | volume = 36 | issue = 3 | pages = 170–176| pmid = 20351555 | doi = 10.1097/ICL.0b013e3181db352f | s2cid = 1751728 }}

HPC is used as a thickener, a low level binder and as an emulsion stabiliser with E number E463. In pharmaceuticals it is used as a binder

{{Cite book

| isbn = 978-0-8247-8210-8

| page = [https://archive.org/details/excipienttoxicit103wein/page/8 8]

| last = Weiner

| first = Myra L.

| author2 = Lois A. Kotkoskie

| title = Excipient Toxicity and Safety

| year = 1999

| publisher = Taylor & Francis

| url-access = registration

| url = https://archive.org/details/excipienttoxicit103wein/page/8

}} in tablets.

HPC is used as a sieving matrix for DNA separations by capillary and microchip electrophoresis.{{cite journal |last1=Sanders |first1=Joshua C. |last2=Breadmore |first2=Michael C. |last3=Kwok |first3=Yien C. |last4=Horsman |first4=Katie M. |last5=Landers |first5=James P. |title=Hydroxypropyl Cellulose as an Adsorptive Coating Sieving Matrix for DNA Separations: Artificial Neural Network Optimization for Microchip Analysis |journal=Analytical Chemistry |date=February 2003 |volume=75 |issue=4 |pages=986–994 |id={{INIST|14571070}} |doi=10.1021/ac020425z |pmid=12622396 }}

HPC is used as a thickener, emulsifier, and stabilizer in cosmetic formulations such as shampoos, conditioners, and lotions.{{Cite web|url=https://www.kimachemical.com/news/is-hydroxypropyl-cellulose-toxic|title=Hydroxypropyl Cellulose|website=kimachemical.com|access-date=7 March 2023}}

HPC is the main ingredient in Cellugel, described as a "safe, penetrating consolidant for leather book covers affected by red rot" by Preservation Solutions, and used in book conservation.{{cite web|url=https://www.conservationresources.com/cellugel.html |title=Cellugel |publisher=Conservationresources.com |accessdate=2021-12-20}}

HPC was used by conservators at the Firearms Museum at the Buffalo Bill Center of the West on the Forgotten Winchester, a Winchester Model 1873 lever-action centerfire rifle discovered in 2014 leaning against a tree in Great Basin National Park, Nevada.[https://centerofthewest.org/2015/07/02/forgotten-winchester-now-on-display-in-center-of-the-wests-cody-firearms-museum/ Forgotten Winchester visits the Center of the West’s Cody Firearms Museum], Buffalo Bill Center of the West

• Carboxymethyl cellulose
• Methyl cellulose
• Hypromellose

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Category:Excipients

Category:Cellulose

Category:Cellulose ethers

Category:E-number additives