Robust size control of bovine serum albumin (BSA) nanoparticles by intermittent addition of a desolvating agent and the particle formation mechanism

• Size of BSA nanoparticles is controlled by pH adjustment of desolvation condition.
• Intermittent addition of ethanol improves particle size control reproducibly.
• Sufficient stabilisation time allows the equilibrated size of BSA nanoparticles.
• Desolvation of BSA molecules begins forming in loose-structured nanoparticles.
• Thereafter density of BSA nanoparticles increases but their size remains unchanged.

In polymeric nanoparticle preparation, despite similar conditions, large fluctuations in particle size distributions are usually observed. Herein, we demonstrate that the intermittent addition of a desolvating agent can improve reproducibility in the preparation of polymeric bovine serum albumin (BSA) nanoparticles. Using this modification, BSA nanoparticles of controlled size can be manufactured with narrow particle size distributions. In our study, ethanol as a desolvating agent was added intermittently to 1% BSA solutions at different pHs with stirring at 700 rpm. The effect of the preparation parameters on size and optical density of the fabricated nanoparticles were studied. The average particles sizes of BSA nanoparticles prepared at pH values of 6, 7 and 9 were approximately 100, 200 and 300 nm, respectively. As ethanol addition increased, desolvation of BSA molecules resulted in formation of loose-structured particles with pH-dependent size. Beyond that, only particle density increased, but size remained unchanged with further addition of ethanol. Consistently uniform particle size distribution was achieved by adding ethanol intermittently.