PubMed · 9691669
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W P Olson. Opinion: aseptic processing and parametric release.. https://pubmed.ncbi.nlm.nih.gov/9691669/
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Roller compaction (RC) is an important dry granulation technique. Since pilot and commercial scale roller compactors, which operate continuously on a large scale, usually require kilograms of material per run, formulation and process development directly on such roller compactors is not practical. In contrast, a compaction simulator (CS) can produce ribblets, also known as "slugs", using only a few grams of material with sinusoidal displacement profile replicating the motion of a specific point on the roll surface. Thus, it is possible to develop RC formulation and process in laboratory using a CS-based material-sparing approach. However, because of the inherently different configurations for applying pressure between die compression and roll compression, translating uniaxial pressure from CS experiments to roll pressure during RC is often unreliable, leading to significant uncertainties in the critical quality attributes of ribbons, such as ribbon solid fraction (or porosity) and mechanical strength. The objective of this study was to identify a correction factor (Kp = uniaxial die compression pressure/roll pressure), by correlating the compressibility profiles from CS and a roller compactor of interest, to enable more reliable process translation from CS to roller compactor. In this study, a Kp value of 0.5 was determined for Alexanderwerk WP120 and validated for Gerteis Mini-Pactor and Bepex Pharmapactor. This value may serve as a starting point for translating the optimal compaction pressure identified based on CS investigation to common roller compactors, requiring only minor adjustments to attain optimal RC process parameters (i.e., roll force and roll gap) for a chosen roller compactor.
Interferon-alpha (IFN) was pegylated and encapsulated in biodegradable microspheres to achieve a long-acting formulation. IFN was pegylated with methoxy-polyethylene glycol (mPEG, MW 2000 or 5000). The conjugation procedures were optimized in terms of concentration of the reactants and the pH condition of the medium. The conjugates (IFN-mPEG(2000) and IFN-mPEG(5000)) were characterized using SDS-PAGE, size-exclusion-HPLC (SE-HPLC) and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectroscopy. The optimized IFN-mPEG conjugates consisted of mono- and multi-pegylated derivatives along with a small amount of native IFN (</=5%). In the simulation studies for microencapsulation, pegylated IFN showed better stability when exposed to dichloromethane as compared to native IFN. In vitro release profiles of IFN and IFN-mPEG from biodegradable poly(D,L-lactide-co-glycolide) microspheres were quite different. Native IFN was released only 16.3+/-0.4% after 3 weeks, but IFN-mPEG(2000) and IFN-mPEG(5000) were released 72.5+/-2.1 and 56.8+/-2.5%, respectively after the same period. It was found that in contrast to native IFN, the pegylated IFN was able to largely retain its native aqueous solubility after being exposed to detrimental conditions of microencapsulation, resulting in a continuous release in vitro. These studies show the possibility of preparation of a long-acting dosage form for IFN using a combination of pegylation and microencapsulation techniques.
Trypsin-encapsulated sol-gel was fabricated in situ onto a plastic microchip to form an on-chip bioreactor that integrates tryptic digestion, separation, and detection. Trypsin-encapsulated sol-gel, which is derived from alkoxysilane, was fabricated within a sample reservoir (SR) of the chip. Fluorescently labeled ArgOEt and bradykinin were digested within the SR followed by electrophoretic separation on the same chip. The plastic microchip, which is made from poly(methyl methacrylate), generated enough electroosmotic flow that substrates and products could be satisfactorily separated. The sol-gel in the SR did not alter the separation efficiency of each peak. With the present device, the analytical time was significantly shortened compared to conventional tryptic reaction schemes. This on-chip microreactor was applicable to the digestion of protein with multiple cleavage sites and separation of digest fragments. Furthermore, the encapsulated trypsin exhibits increased stability, even after continuous use, compared with that in free solution.