Solid core drug delivery systems (SCDDS) were prepared for the oral delivery of biomolecules\nusing mesoporous silica as core, bovine haemoglobin (bHb) as model drug and supercritical fluid (SCF)\nprocessing as encapsulation technique. The use of organic solvents or harsh processing conditions\nin the development of drug delivery systems for biomolecules can be detrimental for the structural\nintegrity of the molecule. Hence, the coating on protein-immobilised particles was performed via\nsupercritical carbon dioxide (scCO2) processing at a temperature lower than the melting point of\nmyristic acid (MA) to avoid any thermal degradation of bHb. The SCDDS were prepared by bHb\nimmobilisation on mesoporous silica followed by myristic acid (MA) coating at 43 DegreeC and 100 bar in\nscCO2. bHb-immobilised silica particles were also coated via solvent evaporation (SE) to compare the\nprotein release with scCO2 processed formulations. In both cases, MA coating provided required\nenteric protection and restricted the bHb release for the first two hours in simulated gastric fluid\n(SGF). The protein release was immediate upon the change of media to simulated intestinal fluid\n(SIF), reaching 70% within three hours. The release from SCF processed samples was slower than SE\nformulations, indicating superior surface coverage ofMAon particles in comparison to the SE method.\nMost importantly, the protein conformation remained unchanged after the release from SCDDS as\nconfirmed by circular dichroism. This study clearly demonstrates that the approach involving protein\nimmobilisation on silica and scCO2 assisted melt-coating method can protect biomolecules from\ngastric environment and provide the required release of a biologic in intestine without any untoward\neffects on protein conformation during processing or after release.
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