Abstract Laboratory investigations of aerosol physico-chemical properties are usually initiated by spray-drying processes. Morphology of the generated particles may vary largely under different spray-drying conditions, which may further affect the characterization of particle properties. However, only limited data is available on the morphology of nebulized submicron particles, particularly for protein particles. To fill this gap, a centrifugal particle mass analyzer coupled with a scanning mobility particle sizer was used to analyze the effective density, an indicator of particle morphology, of nebulized protein particles (bovine serum albumin and ovalbumin) in a size range from 40 to 200 nm. Results indicate that the effective density of the protein particles generated via spray-drying processes is mainly determined by the competition between the removal of liquid water and the redistribution of the solute monomers in the sprayed droplets. Factors increasing the time needed for solute monomers redistribution (e.g. lower solution concentration and larger particle dry size) or decreasing the time needed for liquid water removal (e.g. higher drying rate) may result in a lower particle effective density, meaning a semi-solid structure or partially hollow morphology. This is also confirmed by the particle hygroscopicity measured with a nano-particle hygroscopic tandem differential mobility analyzer and a high humidity tandem differential mobility analyzer. Our results suggest that the factors affecting the morphology of particles may be complex and coupled with each other, highlighting the importance of monitoring particle effective densities in studies using aerosol particles generated via spray-drying processes.

中文翻译：

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喷雾干燥过程产生的蛋白质颗粒的有效密度和吸湿性

摘要 气溶胶理化性质的实验室研究通常由喷雾干燥过程开始。在不同的喷雾干燥条件下，生成的颗粒的形态可能会有很大差异，这可能会进一步影响颗粒特性的表征。然而，关于雾化亚微米颗粒的形态学数据有限，特别是对于蛋白质颗粒。为了填补这一空白，使用离心式颗粒质量分析仪和扫描迁移率粒度仪分析雾化蛋白质颗粒（牛血清白蛋白和卵清蛋白）的有效密度，颗粒形态指标，粒径范围为 40 至 200纳米。结果表明，通过喷雾干燥过程产生的蛋白质颗粒的有效密度主要取决于液态水的去除和喷雾液滴中溶质单体的重新分布之间的竞争。增加溶质单体重新分布所需时间的因素（例如较低的溶液浓度和较大的颗粒干燥尺寸）或减少去除液态水所需的时间（例如较高的干燥速率）可能导致较低的颗粒有效密度，这意味着半固体结构或部分空心形态。用纳米颗粒吸湿串联微分迁移率分析仪和高湿串联微分迁移率分析仪测量的颗粒吸湿性也证实了这一点。