The invention relates to a peptide that includes a plurality of amino acid residues and an enzymatically cleavable moiety including taurine or hypotaurine, the enzymatically cleavable-moiety being linked to the peptide via covalent bond, wherein the peptide is capable of self-assembly to form nanofibrils in the presence of an enzyme that hydrolyzes the enzymatically cleavable-moiety. Compositions containing the enzymatically responsive peptide, and the use thereof for forming a nanofibril network internally of cells, for treating a cancerous condition, and imaging cells are also disclosed.
