Fullerenes solubilized by gamma-cyclodextrins (gamma-CDx) were efficiently transferred to pH-responsive nanogels when they existed in the swollen state below a critical swelling pH. The fullerene molecules subsequently remained encapsulated in the nanogels, regardless of the degree of nanogel swelling, because of their poor aqueous solubility. However, the fullerenes were not transferred from the corresponding gamma-CDx complexes to the nanogels when they existed in shrunken state. The resulting fullerene-nanogel composites also exhibited high stability and allowed for the pH-responsive generation of singlet oxygen (O-1(2)) under photoirradiation conditions.