Supramolecular Approach for Tumor Imaging and Photodynamic Therapy

Photodynamic therapy (PDT) is based on the concept that certain photosensitizers can be localized preferably in neoplastic tissue, and subsequently, these photosensitizers can be activated with the appropriate wavelength of light to generate active molecular species, such as free radicals and singlet oxygen (1O2), which are toxic to cells and tissues. Selectivity can be further enhanced by binding photosensitizers to molecular delivery systems and or by conjugating them with targeting agents such as monoclonal antibodies, integrin antagonists, carbohydrates and other moieties known to have high affinity to target tissues. Most photosensitizers are hydrophobic in nature and therefore require a shuttle to deliver them to a given target cell or tissue. Block copolymers, ceramic, vesicles, liposomes, gel encapsulation and pro-drug approaches are common examples for delivery of hydrophobic drugs. Supramolecular approaches (e.g. nanoparticles) are promising drug delivery systems for improving the bioavailability of poorly water soluble drugs. Functionalities can be added to nanomaterials by interfacing them with biological molecules or structures. Current trends are focused on developing supramolecular delivery systems in which biologically active species are covalently linked, encapsulated or postloaded to the biodegradable and biocompatible nanoparticles. Efforts are also underway in various laboratories to develop multifunctional agents (theranostics) for tumor-imaging and therapy. This particular chapter is focused on the recent advances of various synthetic and supramolecular (nanoparticles) approaches in molecular imaging and PDT and in particular the importance of polyacrylamide-based nanoplatforms in tumor-imaging and therapy.