Alginate copolymer

The term alginate refers to the salt forms of alginic acid [9005-32-7] a copolymer of D-mannopyranosyluronic acid [56687-62-8] (1) and L-gulopyranosyluronic acid [56688-68-7] (2) residues. 

Alginic acid is a copolymer of P-D-mannopyranosyluronic acid (1) and a-L-gulopyranosyluronic acid (2) units linked 1— 4, with no detectable... 

Alginate is a copolymer of a-L-gulopyranuronic and /3-d-mannopyranuronic acid, the sugars being linked (1 4) (see formula 10). 

Fig. 5.5 (A) Alginate block copolymer structure with random sequences (B) divalent cations induced gelation of alginate (formation of egg-box structure).

Figure 2.27 Alginate which is a copolymer of D-mannuronic acid and L-...

Nondegradable polymers are also useful as matrices for ocular implants. This application requires the polymer to be hydrophilic, to minimize local tissue irritation. Need for ocular implants stems from the challenges posed to conventional ocular medicines (i.e., eye drops) such as rapid dilution, tear washout, poor patient compliance, and limited bioavailability. Ocular implants from hydrophilic polymer matrices that provide localized sustained release may overcome the above limitations. The first polymeric sustained release product to reach the market was Ocusert , a pilocarpin sustained release ocular implant developed by Alza. Ocusert has the drug reservoir as a thin disc of pilocarpine-alginate complex sandwiched between two transparent discs of microporous membrane fabricated from ethylene-vinyl acetate copolymer. The microporous membranes permit the tear fluid to penetrate into the drug reservoir compartment to dissolve pilocarpine from the complex. Pilocarpine molecules are then released at a constant rate of 20 or 40 pg/hr for a four- to seven-day management of glaucoma. 

Iskakov, R. M., Kikuchi, A., and Okano, T. Time-programmed pulsatile release of dextran from calcium-alginate gel beads coated with carboxy-re-propylacrylamide copolymers. J. Contr. Rel. 80 57-68, 2002. 

In other applications the pattern of evolution of styrene, butadiene and acrylonitrile as a function of temperature has provided a unique way for classifying different types of ABS. The loss of the antioxidant butylated hydroxytoluene (BHT) was also detected by MS preceding EVA copolymer degradation [165] BHT was identified at a concentration level of 20 ppm. Lehrle and co-workers [52] have described a successful controlled release system for the stabilisation of rubber by encapsulating efficient but rather mobile antioxidants to prevent loss from the host polymer. The performance of the controlled-release of the antioxidant BHT from alginate matrix particles was studied by means of DSC, TG and TG-MS. Polyisoprene rubber is more resistant to oxidation when protected in this way than by the equivalent concentration of unencapsulated antioxidant. 

---