An artificial red blood cells are disclosed comprising a thin film encapsulating a core, the core comprising hemoglobin, wherein the film comprises a plurality of layers of polypeptides, opposing layers comprising alternating oppositely charged polypeptides, and wherein at least half of the amino acid residues in the oppositely charged polypeptides have the same charge. In one embodiment, a first layer comprises a first layer polypeptide comprising one or more first amino acid sequence motifs, wherein the one or more amino acid sequence motifs consist of n amino acids, at least x of which are positively charged, or at least x of which are negatively charged, wherein x is greater than or equal to approximately one-half of n.