**5. Conclusions and perspectives**

In the first parts of the paper, PDT as one of the applications of photodynamic function is addressed, then gold and silver nanomaterials-based PDT and finally, the challenges of metal nanomaterial-based PDT. Photodynamic is determined as

*Metal-Based Nanomaterials Photodynamic Action with a Focus on Au and Ag Nanomaterials DOI: http://dx.doi.org/10.5772/intechopen.109220*

an action in which cells react with oxygen, light, and PS. Utilizin effective PS is an important agents in improving of PDT efficacy. There are different generations of PSs. Due to limitations of organic PSs, the attention toward metal-based nanomaterials for PDT has been increasing, due to their unique properties such as relatively narrow size, shape distribution, simplified functionalization, and consequently, active absorption, stability, and SPR. Metal nanomaterial-based PDT has challenges, including accumulation and long retention time of PSs, hypoxia and low PDT efficiency, low therapeutic penetration of light, brief half-life of 1 O2 and shorter diffusion amplitude in comparison with cell and organelles size, and metal nanomaterials toxicity. These challenges, especially nanotechnology risks, must be addressed in future studies. However, photodynamic techniques are frontier approaches for diagnosis and treatment of disease such as cancer and microbial resistances. Photodynamic applications and nanomedicine are the multidisciplinary fields that could design improved novel PSs with usage of different areas such as biology, physics, engineering, electronic, chemistry, informatics, pharmaceutic, and medicine. Therefore, PDT, especially along with other therapies (combination therapy), deserves attention in future research studies and clinical applications.
