Hemoglobin–Albumin Cluster Incorporating a Pt Nanoparticle: Artificial O(2) Carrier with Antioxidant Activities

A covalent core–shell structured protein cluster composed of hemoglobin (Hb) at the center and human serum albumins (HSA) at the periphery, Hb-HSA(m), is an artificial O(2) carrier that can function as a red blood cell substitute. Here we described the preparation of a novel Hb-HSA(3) cluster with antioxidant activities and its O(2) complex stable in aqueous H(2)O(2) solution. We used an approach of incorporating a Pt nanoparticle (PtNP) into the exterior HSA unit of the cluster. A citrate reduced PtNP (1.8 nm diameter) was bound tightly within the cleft of free HSA with a binding constant (K) of 1.1×10(7) M(−1), generating a stable HSA-PtNP complex. This platinated protein showed high catalytic activities for dismutations of superoxide radical anions (O(2) (•–)) and hydrogen peroxide (H(2)O(2)), i.e., superoxide dismutase and catalase activities. Also, Hb-HSA(3) captured PtNP into the external albumin unit (K = 1.1×10(7) M(−1)), yielding an Hb-HSA(3)(PtNP) cluster. The association of PtNP caused no alteration of the protein surface net charge and O(2) binding affinity. The peripheral HSA-PtNP shell prevents oxidation of the core Hb, which enables the formation of an extremely stable O(2) complex, even in H(2)O(2) solution.