Brief Review on Nanoporphyrins

Abstract

Nanotechnology is one of the most promising well established emerging sciences of nanomaterials having diameter of the order of 1–100 nm. The importance and application of nanotechnology to medicine is hot topic to the present scientific era. Nanomaterials are of great interest of researchers for a wide variety of applications particularly in medical technologies due to properties determined by size and structure with their self-aggregation. One of the most important applications of nanotechnology is nanomedicine. The important application of nanomedicine is to diagnose the particular disease and to heal a damage cell or to destroy the particular abnormally growing or performing cell in the body with safety and high efficiency. As time passes, scientists have encountered the involvement of porphyrins and metalloporphyrins in nanomedicine. Porphyrins are naturally occurring molecules involved widely in biological processes whose functions ranges from oxygen transfer to photosynthesis, from catalysis to pigmentation changes and storage to electron transfer, etc. The basic structure of porphyrin macrocycle consists of four pyrrolic subunits bridged by four mesocarbon atoms. It is an aromatic system consisting of 22-π electrons. It is structured with a basic four-fold symmetry including four nitrogen atoms at the centre. Heme, chlorophylls and vitamin B-12 are the porphyrin-based biological molecules. Porphyrins, the building block of life carries oxygen to every cell of the body. Due to their small size and large surface to volume ratios, they have extensive applications. Porphyrins have been used in large number of studies particularly in photodynamic therapy (PDT). Porphyrins and their derivatives are used as an efficient synthesiser because they possess the ability to absorb visible lights, thereby excited to the triplet state and then transfer its energy to the molecular oxygen, then it produces singlet state oxygen species that kills safely and effectively the cancer cells. The singlet state oxygen has a short life time within the infected cell and can migrate in tissues less than 20 nm after its formation, as a result, the induced injury by singlet oxygen action is highly localised and does not have significant harmful effect to the healthy cells. Therefore, over the past two decades, tremendous research projects have been taken up to synthesise and improve the properties of nanoporphyrin monomer and their derivatives. The aggregated porphyrin and metalloporphyrins are often well organised into nanoscale structure and used PDT. The nanoscale structured porphyrin can be so small that the infected body may clear them too rapidly from them to be effective in detection of diseases or imaging the affected cells. In PDT, the three components viz. oxygen, light and photosensitisers are combined to induce the destruction of the cancer cell. Nanotechnology-based treatment is needed for the early detection of cancer and to diagnose effectively. PDT has become viable option for many cancer patients who are unable to have surgery or who cannot tolerate additional chemotherapy and/or radiation due to their side effects.