We have designed new double stimuli-responsive polyelectrolyte microcapsules to be useable under physiological conditions to handle biomacromolecules while avoiding the risk of denaturation. They are made of poly(4-vinylpyridine hydrochloride) (PVP) and poly(sodium styrene sulfonate) (PSS). The microcontainers are sensitive to temperature variation, as they irreversibly shrink under heating. In addition, the capsules reversibly swell at pH > 6, making it possible to encapsulate human serum proteins by diffusion through the polymer membrane. Encapsulation efficiency is quantified by fluorescence techniques.