The fabrication of protein microbubbles with diverse gas core and the novel exploration on the role of interface introduction in protein crystallization

Abstract

Recently, microbubbles with diameters ranging from a few to tens of microns have an increasing attractive attention in various applications. For microbubbles, exploring convenient and reliable fabrication approach is crucial, in particular achieving stable microbubbles filled with diverse gas. In this work, the baffled high intensity agitation (BHIA) cell was utilized to generate bovine serum albumin (BSA)-coated microbubbles. The characteristics of generated air-filled microbubbles was explored by adjustment of operating parameters. It was found that the microbubble size mainly depends on employed agitation speed. Microbubbles filled with different gas, such as N2, O2, and CO2, also were successfully obtained and show good stability at room temperature due to the formation of thick and elastic BSA shell. It was interestingly observed that a large number of regular BSA particles scattered around the trajectory of microbubble interfaces by scanning electron microscopy, which was obviously different from the particles formed from BSA solution in absence of microbubbles. The mechanism behind the phenomenon was investigated, and it was found that the abundant gas-liquid interface introduced by microbubbles is responsible for triggering the oriented aggregation of BSA molecules. The founding may reveal a spur significant for the effect of gas-liquid interface on the formation of protein crystals.