Gel-former

Hydrous Oxides and Hydroxides. Hydroxide addition to aqueous zirconium solutions precipitates a white gel formerly called a hydroxide, but now commonly considered hydrous zirconium oxide hydrate [12164-98-6], 7 0 - 112 0. However, the behavior of this material changes with time and temperature. 

Carbopol is widely used in cosmetic and pharmaceutical practice as a gel-former. Carbopol resins are hydrophilic polymers which swell in water solutions and transform into the gel form at neutralization. At the elaboration of special cosmetic preparations in which carbopol is used, the problem of raw materials compatibility appears. For example, some extracts of aromatic pectin containing materials destroy the gel structure of carbopol. High contents of bivalent metal ions, in particular calcium ions, destructively influence onto the gel-making ability of the system too. 

Ullmann, E., Thoma, K., and Zelfel, G. (1963), The stability of sodium penicillin G in the presence of ionic surfactants, organic gel formers, and preservatives, Pharm. Acta. Helv., 38,577-586. 

The BASF line of pharmaceutical excipients includes a gel former, viz. the polyoxamer Lutrol F 127. It allows the production of gels whose structures are stable in a pH range of 4-8. No neutralization whatever is necessary. A feature of these gels is their ther-moreversible consistency. It is apparent from Fig. 6 that the gels are liquid at low temperatures i.e. below 15 °C and at temperatures above 75 °C. In between these two values, a gel reversibly exists whose consistency depends on the concentration of the Lutrol F 127. 

Starches are used primarily in canned pet food, not in dry or semi-moist products. Canned pet foods with gravy require a stable, non-gelling thickener, so a highly-stabilized waxy maize starch is used. Fluidity com starches are used as gel formers for firm, cuttable loaf products.189... 

Pour the gel solutions down an inside edge of the gel former using a pipette or large syringe with the plates sloped to about 30° from the horizontal. Bubbles should not form but if they do they can often be dislodged by tapping the plates or rocking from side to side. 

Procedure. Follow the proportions in Table II. Mix and pour into a sealed gel former immediately. Leave room for a short upper stacking gel. With a fine pipette, layer a small amount of 0.1% SDS solution on top of the unpolymerized gel to give a flat surface and to remove bubbles. As the gel polymerizes the water interface will become indistinct and then will reappear as the gel sets. Pour off the water and add the upper gel. Immediately insert the comb for well formation. Upper stacking gels usually shrink slightly as they polymerize. Mount the gel in a vertical apparatus. Make sure the running buffer contacts both upper and lower surfaces of the gel. 

Regarding sol-gel routes, the most used reagents are those made with gel-former compositions aluminium-s-butoxide [Al(OC4Hg)3], tetraethoxysilane [Si(OC2H5)4] (and homologous methoxysilane), aluminum-silicon ester... 

In a Phase I study of an NIH-SBIR program addressing osteomyelitis, available results indicate that 1) selected gel-formers are capable of controlling the in vitro release of gentamicin and vancomycin for at least 2 weeks 2) two types of gel-formers can be formulated, with clinically relevant doses of vancomycin, into injectable forms 3) injection of the vancomycin formulation about the periosteum of the goat tibia for localized drug delivery and 4) controlled release of the vancomycin formulation is feasible without leading to toxic blood levels. 

In an SBIR (Phase I) supported by the DOD, the feasibility of using tailored gel-formers to develop an injectable, controlled release system for intraocular delivery of key drugs is being investigated. The available data indicate that ... 

Injectable gel-formers containing pilocarpine, naproxen, cyclosporin, and ganciclovir in clinically relevant doses can be prepared. 

Incisional wound repair in hairless rats can be improved when placebo gel-formers are used. 

Preliminary study on the use of certain gel-formers for the controlled release of insulin demonstrates the feasibility of this concept. ... 

In a study of skin wormd repair, using sutures or staples on rats, it was shown that covering the wormd with gel-formers allows the use of half the number of interrupted suture stitches or staples while minimizing scar formation. 

The addition of certain members of the family of gel-formers to methoxypropyl cyanoacrylate yields a series of tissue adhesive formulations, which can be used a effectively as ... 

In a recent study, gel-formers have shown to be effective carriers for the controlled release of misoprostol in a newly developed animal model for studying induced cervical ripening. 

The preliminary results of a recent study on expanded Teflon vascular grafts show that certain gel-formers can be used as sealants for these microporous implants. As sealants, they can also be used as carriers for the controlled delivery of bioactive agents to prolong patency of the grafts. 

The BASF line of pharmaceutical excipients includes a gel former, viz. the... 

Fundamental concepts of starch chemistry provide an interpretation of its function and behavior in various food uses. The characteristics of modified starches depend on granule structure and on specific size and shape of the component molecules. Most native starches contain both linear and branched polysaccharides. The linear fraction is responsible for gel formation and for various retrogradation effects, the branched fraction for high colloidal stability and good suspending qualities. Starches are employed in the food industry as gel formers, thickening agents, and colloidal emulsifiers. Desired characteristics can frequently be enhanced by choice of an appropriate modified starch. The various food uses are individually discussed from the standpoint of molecular behavior and optimal types of modification. 

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