Abstract:The triblock copolymer delivery systems controlled the release of sCT in vitro and in vivo in chemically and conformationally stable as well as biologically active and therapeutically effective form.
“…The duration of in vivo release was shorter in comparison with in vitro release due to the presence of enzymes in vivo, leading to faster polymer degradation of polymer. [13][14]49,50 But, in vivo release seems to be consistent with the blood glucose profile and the insulin release pattern observed in the in vitro release.…”
“…The duration of in vivo release was shorter in comparison with in vitro release due to the presence of enzymes in vivo, leading to faster polymer degradation of polymer. [13][14]49,50 But, in vivo release seems to be consistent with the blood glucose profile and the insulin release pattern observed in the in vitro release.…”
“…As shown in Fig. 6, the native PEG-sCT presents a typical negative band at ~199 nm and a low magnitude of ellipticity at 222 nm, suggesting a major random coil structure with a small helical content 36, 37 . The CD spectra of sCT-PEG released from the film were similar to that of the native drug, suggesting the secondary structure of the peptide remains unchanged.Figure 6CD spectra of a solution of native PEG-sCT, mixed solution of PEG-sCT and TA, and release media into which PEG-sCT and TA released.
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Peptides have great potential as therapeutic agents, however, their clinic applications are severely hampered by their instability and short circulation half-life. Zero-order release carriers could not only extend the circulation lifetime of peptides, but also maintain the plasma drug level constant, and thus maximize their therapeutic efficacy and minimize their toxic effect. Here using PEGylated salmon calcitonin (PEG-sCT)/tannic acid (TA) film as an example, we demonstrated that hydrogen-bonded layer-by-layer films of a PEGylated peptide and a polyphenol could be a platform for zero-order peptide release. The films were fabricated under mild conditions. The second component, TA, is a natural product and presents potential therapeutic activities itself. Unlike common carriers, the new carrier releases the peptide via gradual disintegration of the film because of its dynamic nature. The release of PEG-sCT follows a perfect zero-order kinetics without initial burst release. In addition the release rate could be tuned via external stimuli, such as pH and temperature. When implanted in rats, the films could remain the plasma level of PEG-sCT constant over an extended period. Accordingly, the serum calcium level was reduced and maintained constant over the same period, suggesting an improved therapeutic efficacy of the released drug.
“…Various temperatureresponsive polymers have been extensively investigated for the controlled delivery of insulin because these polymers can improve patient compliance due to simplicity of administration by a simple injection without surgery. [3][4][5][6] Even though these polymeric systems have many advantages, the issues such as high initial burst release, relatively short release duration of the incorporated drug, and incomplete release make their development difficult. Some of the approaches that have been tried in order to reduce the initial burst of insulin and to control the release duration and stabilization of insulin are PEGylation of insulin and addition of zinc salts, ethanol and/or glycerol, hydroxypropyl-$-cyclodextrins, sugars, salts, cationic polyelectrolyte, and nonionic and ionic surfactants to insulin.…”
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