Disclosed are peptide conjugates comprising an active agent, a spacer moiety, and a peptide, wherein the peptide comprises the sequence (Xaa1-Xaa2-Xaa3)n1-Xaa4-Xaa5-Xaa6-(Xaa7-Xaa8-Xaa9)n2, wherein Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9 is glycine, proline, a modified proline or aza-glycine, and at least one of Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, or Xaa9 is aza-glycine. Disclosed are peptide conjugates comprising an active agent, a spacer moiety, and a peptide, wherein the peptide comprises the sequence (X1−Y1−Z1)-(X2−Y2−Z2)-(Xn−Yn−Zn) (SEQ ID NO:1-39, 82), wherein n=1-41, and X, Y, and Z are glycine, proline, a modified proline and/or aza-glycine, and at least one of the amino acids in the sequence is aza-glycine. Also disclosed are compositions and nanoparticles comprising these peptide conjugates. Also disclosed are methods of detecting and methods of treating using the peptide conjugates or compositions comprising the peptide conjugates.
