The present invention provides a self-assembling peptide comprising: (a) a first amino acid domain that mediates self-assembly, wherein the domain comprises alternating hydrophobic and hydrophilic amino acids that are complementary and structurally compatible and self-assemble into a macroscopic structure when present in unmodified form; and (b) a second amino acid domain that does not mediate self-assembly in isolated form, wherein the second amino acid domain comprises at least one minimal biologically active sequence. Such self-assembling peptides are described herein as “modified self-assemblingpeptides.” The present invention also provides pharmaceutical compositions, kits and matrices comprising a modified self-assembling peptide, and methods of using and making such compositions, kits and matrices.