Gold Nanoparticles’ Role in Photodynamic Therapy for Cancer Treatment

A review of studies described recent developments in photodynamic therapy (PDT) and the use of gold nanoparticles in the treatment of cancer. Results revealed that gold nanoparticles generate singlet oxygen alone; referred to as photothermal therapy (PTT), with photosensitizer as a component of PDT. The photosensitizer encapsulation in gold nanoparticles creates synergistic PTT and PDT effects, according to a poster presentation at the 2022 International National Community Oncology Dispensing Association (NCODA) Spring Forum by Tavi Shah, MD, School of Pharmacy, MCPHS University, Boston, Massachusetts.

Research reveals that nanoparticle delivery systems are beneficial for use in photodynamic therapy (PDT) due to their low cost and easy synthesis. PDT is utilized to treat breast, brain, intraocular, esophageal, gastric, head, neck, and colorectal cancers, as well as noncancerous conditions such as atherosclerosis, rheumatoid arthritis, and macular degeneration. Studies also indicate that gold nanoparticles (GNP) are also chemically inert and have marginal cytotoxicity and also demonstrate the surface plasmon resonance phenomenon. Thus when GNPs are irradiated with light, the light can be converted into heat and is scattered to generate death of cancer cells.

In this study, Dr Shah conducted a search of published literature utilizing PubMed and Google Scholar to find studies involving photodynamic therapy, cancer, and gold nanoparticles. In one study, gold-gold sulfide nanoshells were conjugated to indocyanine green and their effects were tested on HeLa cells derived from cervix cancers. The compound exhibited a stronger photodynamic and photothermal effect on the cells, exhibiting the synergism between these therapies. 

In another study, meso-tetrahydroxyphenylchlorin-conjugated gold nanoparticles (mTHPC) was loaded into gold nanoparticles and tested in human neuroblastoma (SHSY5Y) cells. The study revealed that the conjugate demonstrated elevated rates of cell death in tissue treated with the gold nanoconjugates compared to the free photosensitizer. The free mTHPC usually shows nonspecific cytotoxicity at higher concentrations, the conjugate only demonstrated cell death upon irradiation. Due to minimal toxicity, the conjugated compound can be given at a higher dose and can yield a robust effect. The conjugate also demonstrated better solubility in water, greater cell death rate, and was most effective with multiple irradiation sessions.

In conclusion, Dr Shah wrote, “Historically, photodynamic therapy has not been very popular clinically due to its inability to target deep tumors. However, with the development of photosensitizers responding to deeper wavelengths of photodynamic therapy, many of these agents are expected to translate well into clinical trials. In the coming years we hope to see more clinical trials involving photodynamic therapy, especially gold nanoparticles since they have a dual mechanism of PDT and PTT.” Dr Shah also mentioned that providers need to be more cognizant of advancements in the use of PDT, in order to provide a less invasive, more efficacious way to treat cancer patients.

Reference

Shah T. Use of Gold Nanoparticles in Photodynamic Therapy for the Treatment of Cancer. Presented at the: 2022 NCODA International Spring Forum; April 27-29, 2022; Atlanta, GA.