SOME FACTORS ASSOCIATED WITH THE ULTRASONIC NEBULIZATION OF PROTEINS

Ultrasonic nebulization of lactate dehydrogenase (LDH) was investigate d using a DeVilbiss ''Aerosonic'' nebulizer. The enzyme (8ml, 0.025mg/ ml Na2HPO4, pH 7.0) was completely inactivated after 20 minutes of ope ration. However, the inactivation profile observed during ultrasonic n ebulization was different from that previously observed using air-jet nebulization. At least two mechanisms are involved, one associated wit h heating and the other with aerosol production. By preventing heating of the nebulizer fluid during operation, the denaturation profile was dramatically altered. By additionally including 0.01% w/v Tween 80 or 1%w/v PEG 8000, almost all activity was retained. Similar results wer e obtained by preventing aerosol production and heating. However, 100% of activity was lost when heating was allowed to occur without aeroso l formation. The results demonstrate that cooling in conjunction with a surfactant is one approach that could be used to stabilize proteins to ultrasonic nebulization. However, cooling also significantly reduce d solute output from the nebulizer. When operated at 10 degrees C outp ut was negligible. At 50 degrees C the output was 5x greater than that found at room temperature. The median droplet size (mu m) was not sig nificantly influenced by the operating temperature of the nebulizer fl uid (3.6+/-0.4, 21 degrees C; 3.9+/-0.2, 50 degrees C, p = NS (n = 6)) although the size distribution was noted to increase at the higher te mperature.