Spray-coating of rhDNase on lactose: Effect of system design, operational parameters and protein formulation

The feasibility of spray-coating fine lactose powders with recombinant human deoxyribonuclease (rhDNase) using a bench-top fluid-bed processor (STREA-1) was studied. The effect of operating parameters, system design and protein formulation on coating performance was evaluated and compared with a laboratory-scale, Wurster processor (GPCG-1), as reported previously (Maa and Hsu, 1996a). Protein denaturation occurred during spray-coating in both processors, though to a lesser degree in STREA-1 than in GPCG-1. The cause of protein denaturation during coating was determined to be thermally induced and most likely occurred during drying. The combined effect of shear and heat on protein aggregation during atomization was found to be insignificant. GPCG-1 outperformed STREA-1 in terms of particle agglomeration and product yield. Particle agglomeration in the latter could be reduced by increasing the atomizing pressure and decreasing the liquid feed rate. Overall, this report demonstrates that it is feasible to use the bench-top fluid-bed processor for protein spray-coating, but the application on fine carriers (< 100 mu m) is limited.