Hydroxypropyl cellulose
Hydroxypropyl cellulose (HPC) is a derivative of cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 with both water solubility and organic solubility. It is used as a topical ophthalmic protectant and lubricant.


HPC is an ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...

 of cellulose in which some of the hydroxyl groups in the repeating glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 units have been hydroxypropylated forming -OCH2CH(OH)CH3 groups using propylene oxide
Propylene oxide
Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics...

. The average number of substituted hydroxyl groups per glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 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
Lower critical solution temperature
The lower critical solution temperature or lower consolute temperature is the critical temperature below which the components of a mixture are miscible for all compositions...

 (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 mesophase
In physics, a mesophase is a state of matter intermediate between liquid and solid. Gelatin is a common example of a partially-ordered structure in a mesophase...

s according to its concentration in water. Such mesophases include isotropic, anisotropic, nematic and cholesteric
Cholesteric liquid crystal
A cholesteric liquid crystal is a type of liquid crystal with a helical structure and which is therefore chiral. Cholesteric liquid crystals are also known as chiral nematic liquid crystals. They organize in layers with no positional ordering within layers, but a director axis which varies with...

. The last one gives many colors such as violet, green and red.


Lacrisert, manufactured by Aton Pharma, is a formulation of HPC used for artificial tears
Tears are secretions that clean and lubricate the eyes. Lacrimation or lachrymation is the production or shedding of tears....

. It is used to treat medical conditions characterized by insufficient tear production such as keratoconjunctivitis sicca
Keratoconjunctivitis sicca
Keratoconjunctivitis sicca , also called keratitis sicca, xerophthalmia or dry eye syndrome is an eye disease caused by eye dryness, which, in turn, is caused by either decreased tear production or increased tear film evaporation. It is found in humans and some animals...

), recurrent corneal erosions
Corneal ulcer
A corneal ulcer, or ulcerative keratitis, is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and is sometimes seen in cats...

, decreased corneal sensitivity, exposure and neuroparalytic keratitis
Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...

. HPC is also used as a lubricant for artificial eyes.

As a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

, HPC is used as a thickener, a low level binder and as an emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

 stabiliser with E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 E463. In pharmaceuticals it is used as a disintegrant,
and a binder, in tablets.

HPC is used as a sieving matrix for DNA separations by capillary and microchip electrophoresis.

HPC is the main ingredient in Cellugel which is used in book conservation. Cellugel is described as "A safe, penetrating consolidant for leather book covers affected by red rot" and is produced by Preservation Solutions.
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