An investigation on microfluidic preparation of aluminum phosphate adjuvant

Abstract

Aluminum adjuvants have been used for almost a century due to their good record of safety and efficacy. However, their preparation is rather traditional and usually exhibits batch-to-batch variations. To achieve optimal adjuvanticity, the controllable and consistent preparation of aluminum adjuvants is desired, but remains a great challenge to date. Here, the preparation of aluminum phosphate (AP) adjuvant through a microfluidic approach is investigated. A chaotic micromixer is applied to enhance the mixing between the reactants. In addition, the effects of magnetic stirring and continuous-flow shearing during the settling of the AP precipitate are compared. The influences of the concentration of reactants, flow rate, residence time, as well as the heating temperature and shear intensity in the stabilizing stage are analyzed. Results show that the current method provides better control over the particle size distribution. The median particle size Dv(50) is tunable in the range of 1.6–3.4 µm, and the uniformity index varies from 0.24 to 0.45. The isoelectric point (IEP) and the adsorption capacity are also examined. Relevant findings provide useful references for the development and optimization of AP-adjuvanted vaccines.