Encapsulation of irregularly shaped solid forms of proteins in a high-pressure fluidized bed

By combining the advantages of a high-pressure fluidized bed with the adjuvant properties of a supercritical fluid, namely RESS-process, solid proteins could be encapsulated by paraffin. Two different irregular shaped proteins, a model protein (bovine serum albumin, BSA) and a pharmaceutical protein (insulin) were investigated. Mixing the highly non-spherical protein particles with lactose allows its usage as bed material despite the unfavourable shape properties. The paraffin encapsulation of respective bed mixtures with BSA was successful with paraffin loadings up to 9.1 g/100 gbed and yields up to nearly 100%, depending on process parameters. During the encapsulation process, breakage of the bed material occurred, resulting in mean sauter diameters of even less than 35 μm. Dissolution tests pointed out, that 100% dissolution after more than 180 min could be achieved. Thus, the particle breakage induced by the nozzle jet during the coating process seems to support the encapsulation of fines. A principle application of the process for insulin encapsulation for a selected set of process parameters has been demonstrated.