Preparation of protein loaded chitosan microparticles by combined precipitation and spherical agglomeration

• Spherical agglomeration was carried out in EtOAc–EtOH–H2O ternary system.
• The model drug was human serum albumin.
• The paper describes the effects of the most important process variables.
• Under given conditions nearly spherical shape agglomerates was achieved.
• The paper proposes a probable mechanism of formation of the composite microparticle.

Combined precipitation and spherical agglomeration was carried out in the non-miscible region of ethyl acetate–ethanol–water ternary solvent system. At first, w/o type quasi emulsion was prepared by sequential introduction of aqueous solutions of human serum albumin (HSA), chitosan (CS), and poly(4-styrenesulfonate) (PSS) into an ethyl acetate–ethanol solvent mixture. HSA was used to model a protein type drug, while CS and PSS served as matrix material in the obtained composite particles. PSS also served as chemical precipitation agent for both of the HSA and CS. The solubility of all these substances was reduced by introduction of additional amounts of ethyl acetate–ethanol mixture and/or ethanol as poor solvents. Due to the counter-diffusion of the good and poor solvents between the water rich droplets and the ethyl acetate–ethanol rich continuous phase, the aqueous phase gradually disappeared and partial agglomeration of the precipitated solids and their transfer to the continuous organic phase took place. The paper gives a report on the effect of several process variables on the quality of the obtained microparticles, such as their shape and stability against disintegration. The effects of the composition of the ternary solvent mixture, the route of its variation, the feeding method and composition of the added poor solvents, the stirring rate and the duration of agitation were studied.

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