Porphyrin-Based Compounds in Medicine: From Photodynamic Therapy to Theranostics

Porphyrins and their derivatives represent one of the most adaptable classes of compounds in contemporary biomedical research, bridging the crucial gap between diagnostic imaging and therapeutic intervention. This comprehensive review examines the evolution of porphyrin-based compounds and their therapeutic applications, from their fundamental role in photodynamic therapy to their status as sophisticated theranostic platforms. The unique photophysical properties of porphyrins, which are characterized by intense Soret band absorption, tunable fluorescence emission, and the generation of reactive oxygen species upon light activation, underpin their dual functionality as both imaging and therapeutic agents. The structural basis of porphyrin photochemistry, their progression through the first, second, and third generation of photosensitizers, and the transformative impact of nanotechnology, especially in overcoming intrinsic limitations such as poor aqueous solubility, aggregation-caused quenching, as well as limited tumor specificity, are discussed. Attention is devoted to emerging nanoplatforms such as porphyrin-based metal–organic frameworks (MOFs), covalent–organic frameworks (COFs), and electrospun nanofibers, which enable multimodal imaging, synergistic therapies, and controlled drug delivery. The challenges that impede clinical translation, including phototoxicity, tissue penetration limitations, and biosafety concerns, are critically examined, along with promising strategies for their resolution. By integrating porphyrin-based theranostic capabilities within single molecular platforms, these systems are ready to advance personalized cancer medicine while enabling real-time treatment monitoring and precision-guided interventions, which could substantially improve patient outcomes.