PubMed · 7249942
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1981-05-22. Morphine in slow-release tablets.. https://pubmed.ncbi.nlm.nih.gov/7249942/
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The purpose of this study was to test the utility of infrared (IR) spectroscopy to determine protein secondary structure in biodegradable microspheres. Encapsulation of proteins within biodegradable polymers, [e.g. poly(lactic-co-glycolic acid) (PLGA)] for controlled drug release has recently been the subject of intense research effort. The ability to assess protein integrity after microsphere production is necessary to successfully produce microspheres that release native proteins. We used IR spectroscopy, a noninvasive method-as opposed to conventional organic solvent extraction or in vitro release at elevated temperature-to assess the secondary structure of recombinant human growth hormone (rhGH) within dry and rehydrated microspheres. PLGA microspheres containing rhGH with different excipients were prepared by a conventional double-emulsion method. The protein IR spectra indicated that the encapsulation process could perturb the structure of rhGH and that excipients could inhibit this damage to varying degrees. A strong positive correlation was found between intensity of the dominant alpha-helical band in the spectra of rhGH in rehydrated microspheres and the percent monomer released from microspheres during incubation in buffer. We also studied microspheres prepared with zinc-precipitated rhGH. The addition of Zn2+ during microsphere processing partially inhibited protein unfolding and fostered complete refolding of rhGH upon rehydration. In conclusion, IR spectroscopy can serve as a valuable tool to assess protein structure within both dried and rehydrated microspheres.
Human immunoglobulin G (IgG) serves as an important chemotherapeutic agent for a number of immunological ailments and as a carrier in the targeted delivery of other therapeutic agents. This paper deals with the characterization of IgG-dispersed monolithic matrixes of different geometries, prepared using a nonbiodegradable polymer carrier EVAc. The morphological changes associated with the matrix during drug release was studied using scanning electron microscopy, polarizing microscopy, atomic force microscopy, and X-ray photoelectron microscopy, and the results were compared. The study answered the burst effect problem significantly and illustrated the potential of these techniques in understanding the morphological structure of matrixes and mode of release kinetics.