Liquid droplets of protein–polyelectrolyte complexes (PPCs) have been developed as a new candidate for stabilization and concentration of protein drugs. However, it remains unclear whether additives affect the precipitation and redissolution yields of PPCs. In the present study, we investigated the PPC formation of human immunoglobulin G (IgG) and poly-L-glutamic acid (polyE) in the presence of various additives that have diverse effects, such as protein stabilization. Alcohols, including ethanol, successfully increased the PPC precipitation yield to over 90%, and the PPCs formed were completely redissolved at physiological ionic strength. However, poly(ethylene glycol), sugars, and amino acids did not improve the precipitation and redissolution yields of PPCs over those observed when no additives were included. Circular dichroism spectrometry showed that the secondary structure of polyE as well as electrostatic interactions play important roles in increasing the PPC precipitation yield when ethanol is used as an additive. The maximum concentration of IgG reached 100 mg/ml with the use of ethanol, which was 15% higher efficiency of the protein yield after precipitation and redissolution than that in the absence of additives. Thus, the addition of a small amount of ethanol is effective for the concentration and stabilization of precipitated PPCs containing IgG formulations.

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We have previously demonstrated that feeding a diet with a high amino acid (60% AA diet) content, as a mixture simulating casein, induced pancreatic growth and pancreatic protease production in rats. In the present study, we examined the effects of an increasing dietary content of essential amino acids (EAA, x1-x3 in exp. 1 and x1 -x3.3 in exp. 2) and non-essential amino acids (NEAA, x1 -x3 in exp. 1 and x1 -x5.2 in exp. 2) on pancreatic growth, amylase and protease adaptation using casein-type amino acid mixtures (exp.1, basal diet; 20% AA diet) and egg white-type amino acid mixtures (exp.2, basal diet; 12% AA diet). Pancreatic growth and trypsin activity were induced as the dietary content of NEAA was increased in experiments