Porphyrins represent a class of compounds that are biologically compatible, their metal complexes are both thermodynamically and kinetically stable and are considered as excellent agents, both for the photodynamic therapy (PTD) and as labels for cancer detection. Photodynamic therapy (PDT) refers to the administration of photosensitizers, light and oxygen molecules to generate cytotoxic reactive oxygen species (ROS), mainly singlet oxygen, which is responsible for killing cancer cells. Due to the high yield of singlet oxygen generation upon light activation, porphyrins are promising and clinically approved photosensitizers (PSs) for use in biomedical applications [1]. Well defined structures of self-assembling peptides, such as hydrogels, can be used as scaffolds to chelate and deliver porphyrin and metalloporphyrins to cells. In order to label peptides with porphyrin-based fluorophores, we carried out self-assembling studies of amino acid peptide sequences. As a proof of concept, we worked with peptide sequences which consist of histidine residues in their backbone, in order to mimic the His6-tag. The peptide sequences have the ability to self-assemble forming various nanostructures such as fibrils and spheres, that could possibly coordinate with porphyrin-NTA hybrids via Ni²⁺ and could be applied as chromophores for target detection into the cells [2]. Moreover, we recently harnessed the antimicrobial properties of porphyrins and encapsulated them in peptide hydrogel scaffolds. The release kinetics of the encapsulated porphyrins, as well as their antimicrobial activity against Escherichia coli bacteria upon light irradiation, were studied. 

[1] A. G. Sampedro J. Porphyrins Phthalocyanines Multimodal use of the porphyrin TMPyP: From cancer therapy to antimicrobial applications, 2019, 23, 1-17. 

[2] E. Glymenaki AS Omega Design and Synthesis of Porphyrin–Nitrilotriacetic Acid Dyads with Potential Applications in Peptide Labeling through Metallochelate Coupling, 2022, 7,1803-1818.