This thesis focuses on the development of porphyrin-based complexes as multi-modal bio-imaging probes. Detailed studies of photophysical and biological properties were included.;In chapter 1, the general background of porphyrin and its derivatives, their structure specialty, synthetic methods, photophysical properties, and applications in biological system were described.;Curcumin-bridged porphyrin-copper complex (Por-Cu-Cur) which can permeate through the high blood-brain barrier, accumulate fast in brain tissues, and emit brilliant and stable two photon excited emission has been developed. Apart from this, Por-Cu-Cur shows high binding affinity for Ab fibrils, and decent inhibitory effect on the fibrillation of Ab1-42 peptides, as well as low toxicity to neuro-derived SK-N-SH cells in vitro and particularly in vivo in transgenic mice.;The design and synthesis of amphiphilic porphyrin linked ruthenium complexes were described. We focus on the photophysical studies of its UV-Vis absorption spectrum, fluorescence spectrum, solvatochromism, and singlet oxygen phosphorescence. The converse energy transfer mechanism of porphyrin-ruthenium complexes and zinc-porphyrin-ruthenium complexes has been clearly studied. Subcellular localization, dark cytotoxicity and photodynamic therapy has been well studied, which efficiency correspond to the energy transfer mechanism.;Based on the previous study, we would like to provide a proof-of-concept model - labelling (hot/cold) gallium in porphyrin-based complex with a short reaction time (but with high reaction yield) and aim to develop a multi-modal bioprobe for photodynamic therapy, optical imaging and positron emission tomography in one piece. An amphiphilic hot gallium-porphyrin-ruthenium compound has been synthesized (GaporRu-1) with reaction time of 15 minute and 85 % yield. The acidity of GaporRu-1 enables selective subcellular localization in lysosome. It also has an good singlet oxygen quantum yield (61.4 %), which proves its great potential for further in vivo study for as both PDT and PET agents.;Experimental details are shown in chapter 5. Including details of photophysical measurements, instrumentation and biological measurements.