Chapter 2: Design and Synthesis of Photosensitizer-Peptide Conjugates for PDT

The design and synthesis of covalently linked photosensitizer-peptide conjugates are reviewed in this chapter. Peptides of relatively small size (<50 amino acids) are most commonly used for enhancing the photosensitizer targeting specificity, due to their straightforward synthesis and ease of conjugation to photosensitizers. Porphyrin, chlorin and phthalocyanine macrocycles are the most common PDT photosensitizers used in the conjugation reactions to peptides, generally via a low molecular weight linker, following either solution or solid phase protocols. These so-called third-generation photosensitizers have shown increased selectivity for targeting specific cell enzymes or receptors, and enhanced PDT efficacy compared with unconjugated photosensitizers.