Mucins viscosity

Glycoproteins are needed as lubricants, and also function as protective agents of surfaces. The viscosity of mucins is due to the carbohydrate moiety.393 Some species of arctic fish contain an antifreeze glycoprotein that lowers the freezing point of their blood408 by preventing the lattice fonnation of water-ice clusters, a step that is a prerequisite... 

In conclusion, the remarkable influence on DAP activity exerted by the low-viscosity PGA vehicles is an issue deserving further attention, in view of the possible implication of a muco-adhesive mechanism. A closer study of the potential interactive properties of polyuronic acids and of their drug salts with the precorneal mucin might lead to a better understanding of the bioadhesive properties of these and other similar anionic polymeric materials, and of their influence on ocular drug bioavailability. 

Chitosan has been shown to increase precorneal drug residence times. The cationic chitosan slows tear drainage by increasing viscosity and by mucoadhesion with the negatively charged mucin. Up to a threefold increase of the corneal residence time has been achieved by the addition of chitosan to topical vehicles [5]. Carbomer gels at 0.3% have also been shown to be effective in prolonging the tear film break-up time [6]. Hyaluronic acid has been reported to... 

Other Vinyl Derivatives. PVP is a nonionic surfactant used in 3% to 5% concentrations to increase viscosity of solutions. Although it exhibits surface-active properties similar to the cellulose ethers, PVP appears to have less abiUty to lower the interfacial tension at a water-oil interface. Nevertheless, in contrast to the cellulose ethers, PVP appears capable of forming hydrophilic coatings in the form of adsorbed layers. Because conjunctival mucin is believed to interact with the ocular surfece to form an adsorbing surface for aqueous tears, the formation by artificial means of a hydrophilic layer that would mimic conjimctival mucin (mucomimetic) appears to be clinically desirable. Both mucin- and aqueous-deficient dry eyes would benefit, because the wetting ability of the corneal surfece would be enhanced. 

Besides taking part in acquired pellicle formation on tooth (denture, implant) surfaces, MUC5B type mucins cover all oral surfaces with a 10-20- im thick layer. In addition, MUC5B type mucins form a hydrophilic viscoelastic gel (already in low concentration) that causes a high viscosity matrix of saliva. 

Intrinsic viscosity [q] can be related to complex size via MFIKS, a coefficient Diffusion coefficient, D, can be related to complex size via MFIKS c. coefficient SEC malls particularly useful for determining MW of mucin, turbidity, semiquantitative indicator... 

The viscosity of mucus is affected by binding between calcium and the mucus, which probably arises from an ionic interaction with the sialic acid in the mucin. These variations are indicated by a change in the pH, viscoelastic properties, water, and protein content of cervical mucus. Calcium is needed to establish an intercellular contact and the assembly of tight junction in the cervical epithelium. Changes in extracellular calcium affect the permeability of tight junctions and play a role in regulating the production of cervical mucus.Prostaglandin concentrations... 

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