Chapter 4. Innovative Design of Antimicrobial Photosensitizers

In recent years the desirable structural features of effective antimicrobial photosensitizers (PS) have become better understood. In addition to the normal requirements of a efficient PS such as a high absorption band in the red/NIR region of the spectrum and a good triplet yield that allows production of reactive oxygen species upon illumination, additional molecular features are needed. The most important structural feature is either a constitutive cationic charge provided by quaternary nitrogen groups or a set of basic amino groups provided by a cationic polymer. Additional features may include a correct balance between lipophilicity and hydrophilicity and a certain degree of molecular asymmetry. This chapter will review four groups of antimicrobial PS that our laboratory has published: (A) conjugates between PS and poly-L-lysine or polyethylenimine; (B) cationic functionalized fullerenes; (C) cationic functionalized bacteriochlorins; (D) chalcogen substituted benzo[a]phenoxazinium dyes.