A poly(${gamma}$-glutamic acid) (${gamma}$PGA)-cholesterol conjugate was synthesized and its properties were then evaluated. The conjugate exhibited an amphiphilic nature derived from the hydrophilic ${gamma}$PGA backbone and the hydrophobic cholesterol side chain. The conjugate spontaneously formed nanoparticles, becoming an aqueous solution when at low concentrations, and at high concentrations the result was the formation of a physical gel. By utilizing the self-aggregating properties of the conjugate in water, an artificial chaperone was developed. A complex of protein, with the nanoparticles of the conjugate, was formed and the protein was released upon the dissociation of the nanoparticles through the addition of ${eta}$-cyclodextrin. For denatured carbonic anhydrase, the activity was recovered in the artificial chaperone of the nanoparticle conjugate.