Surface coat, mucins

The major surface coat component of Toxocara larvae runs as a set of four closely migrating bands with apparent mobility of 120 kDa on SDS-PAGE. One of these was cloned and sequenced, identified as a serine-rich mucin and designated MUC-1 (Gems and Maizels, 1996). We have now established that there are at least five distinct mucin genes in this parasite, which bear general similarity but important distinctions. Thus, MUC-2, MUC-3, MUC-4 and MUC-5 are all threonine-rich rather than serine-rich, and all five differ in the repeat motifs within the mucin domains. All have similar non-mucin, cysteine-rich domains originally termed NC6 (nematode six-cysteine) domains, and since renamed SXC (six-cysteine), as described below. All mucins have a pair of SXC domains at their C-terminus, while MUC-3 and MUC-5 also have paired N-terminal SXC domains. 

Gems, D.H. and Maizels, R.M. (1996) An abundantly expressed mucin-like protein from Toxocara canis infective larvae the precursor of the larval surface coat glycoproteins. Proceedings of the National Academy of Sciences USA 93,1665-1670. 

Another approach is that of bioadhesive materials. The principle is to administer a device with adhesive polymers having an affinity for the gastric surface, most probably the mucin coat [12]. Bioadhesives have demonstrated utility in the mouth, eye, and vagina, with a number of commercially available products. To date, use of bioadhesives in oral drug delivery is a theoretical possibility, but no promising leads have been published. 

Q9 The stomach secretes a very acid gastric juice with a pH of 1.5-2. The mucosa is normally protected from acid by a number of mechanisms. Mucus is produced by the large number of mucous cells in the body and fundus. It contains glycoproteins called mucins, and the mucus produced forms a kind of gel which coats the mucosal surface. In addition these cells secrete HCO3-, which is trapped in the mucus and increases the local pH to form a less acidic environment at the surface of the epithelial cells. 

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. 

C. A. Buscaglia, V. A. Campo, A. C. C. Frasch, and J. M. Di Noia, Trypanosoma cruzi surface mucins host-dependent coat diversity, Nat. Rev. Microbiol, 4 (2006) 229-236 A. C. C. Frasch, Functional diversity in the trans-sialidase and mucin families in Trypanosoma cruzi, Parasitol. Today, 16 (2000) 282-286. 

An approach to noncovalent functionalization takes advantage of attractive van der Waals forces to coat the outer surface of a nanotube with a substance that bears the functionality. This approach was successfully demonstrated using a synthetic polymer designed to mimic the properties of mucin. (Mucin is the main substance responsible for the lubricating properties of... 

Mucin A glycoprotein in mucus that coats bacteria and prevents their attaching to surfaces. 

A potential mucoadhesive effect of GMO has been used as a rationale to develop GMO-based particles for administration to mucosal surfaces such as present in the GI tract. The interaction of simple, GMO/PX407-based cubosomes with mucin and mucin-coated surfaces was, however, weak. Modification of the cubo-some surface by the adsorption of chitosan led to an increased interaction with mucin-coated surfaces and may thus be an option to improve the drug delivery properties of such particles. Whether surface modification by chitosan adsorption has an effect on the internal structure of the particles remains, however, to be clarified. 

The Effect of Salt Concentration and Cation Valency on Interactions Between Mucin-Coated Hydrophobic Surfaces... 

Adsorption of and Interaction Between Mucin-Coated Surfaces in 30 mM NaNOs... 

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