Provided herein relates to self-assembling peptides and various nanostructures self-assembled from the isolated peptides. In some embodiments, the self-assembling peptides can form a nanostructure, e.g., a nanoparticle or microparticle, for use in various biomedical applications such as drug delivery or tissue engineering. In some embodiments, the nanostructures can comprise an agent, e.g., a biological molecule. The agent can be encapsulated or entrapped in the nanostructures during formation of the nanostructures. Alternatively or additionally, the agent can be integrated directly or indirectly (e.g., via a linker or a conjugation or crosslinking agent) to the self-assembling peptide structure, prior to formation of the nanostructures. In some embodiments where the agent is a peptide-based agent, unitary peptide nano structures, rather than nanoparticles that are formed and later covalently modified, can be generated.