PubMed · 9066212
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S Zakaria. 1997. Removable prosthesis.. https://doi.org/10.14219/jada.archive.1997.0178
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The release of insulin hexamer (39 kD) and amyloglucosidase (AMG, 97 kD), entrapped in spherical Ca-alginate beads, was investigated. While the release of insulin could be described solely by diffusion this was not the case for the 1.6 (rm/rm) larger AMG protein, where rm is the Stokes-Einstein effective molecular radius. Because the alginate bead size was not constant during the release experiments, it was hypothesised that in addition to the diffusional mass transfer, a non-negligible convective flow of liquid in or out of the beads was present due to swelling or shrinkage, respectively. Although it should be expected that the effective diffusion coefficient of AMG is only slightly lower than that of insulin, the results show that the effective diffusions coefficient of AMG was found to be much smaller. In the case of AMG, it was shown that including bead size changes and the resulting convective flow in the numerical model, release could be described more accurately. The numerical model was able to describe the release characteristics from both shrinking, swelling, and non-swelling alginate beads. To evaluate the effect of bead swelling on the protein release rate, a swelling modulus and a release index was defined, describing the different effects on release of smaller and larger proteins.
Occlusion and elasticity were combined in a novel cotton-based alginate dressing containing a nontoxic elastase inhibitor. Cotton gauzes were modified with a textile finishing process for incorporating alginate to yield a dressing material that retains elasticity while enhancing absorption. The algino-cellulose conjugates were formed through citric acid crosslinking of cellulose and alginate. The alginate-citrate finishes were applied to cotton gauzes in various formulations containing citric acid, sodium hypophosphite, and polyethylene glycol. The modified gauzes contain a citrate conjugate of alginate and cellulose that gels upon hydration. The alginate-citrate finishes were combined with the neutrophil elastase inhibitor, oleic acid, to demonstrate the ability of the algino-cellulose fibers to release the inhibitor and neutralize destructively high levels of neutrophil elastase found in nonhealing and burn wounds. Four types of gauzes were examined for the effect of the algino-cellulose finish on cotton gauze absorbency and elasticity. Fourier transform infrared (FTIR) spectroscopy of the film and alginate-citrate finished cotton showed formation of the alginate and citrate cellulose esters. Scanning electron microscopy analysis revealed large areas of the yarn surface covered by the alginate film with a smooth surface on the original fibers. Wetting of the gauze surface resulted in formation of a hydrated gel on the yarns with apparent swelling of the film and the fiber-coated alginate.
An Azotobacter vinelandii mutant lacking alginate-lyase (SML2) and the wild type (ATCC 9046) were used to discriminate between the roles of the polymerase complex and alginate-lyase in the synthesis of alginate in cultures conducted under controlled dissolved oxygen tension (DOT). To avoid the presence of pre-synthesized alginates, all cultures were inoculated with washed cells. For cultures carried out at 3% DOT using the mutant, a well defined family of alginates of high mean molecular weight (MMW) were obtained (985 kDa). Under 1% and 5% DOT, the mutant produced unique families of alginates with lower MMW (150 and 388 kDa). A similar behavior was observed using the wild type: a production of well defined families of alginates of high MMW at 3% DOT (1,250 kDa) and lower MMW at 1% and 5% DOT (370 and 350 kDa). At the end of the ATCC 9046 fermentations, alginate was depolymerized by the action of lyases. Overall, the evidence indicated that polymerization of alginate is carried out by producing families of polysaccharide in a narrow MMW range, and that it is highly dependent on DOT. The role of alginate-lyase (present in the wild type) is restricted to a post-polymerization step.