Abstract: The present disclosure provides methods for determining collagen content using collagen hybridizing peptides. The present disclosure provides methods for quantifying an amount of disrupted collagen (e.g., collagen with disrupted triple helicity) and/or total collagen. The present disclosure provides methods for quantifying an amount of disrupted collagen (e.g., collagen with disrupted triple helicity) as a portion of total collagen.

Abstract: 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.