Controlling Toxicity with 'Light' to Target 'Only Cancer Cells'! ... UNIST Research Team Develops 'Nano-Gel Photosensitizer System'

Schematic diagram of the nano-gel (P-IrNG) photosensitizer system.

[Asia Economy Yeongnam Reporting Headquarters Reporter Hwang Dooyul] A safe method for photodynamic therapy, which attacks cancer cells by irradiating them with light, has been developed.

Professor Tae-Hyuk Kwon's team from the Department of Chemistry at UNIST developed a ‘nano-gel photosensitizer system’.

The system stably stores anticancer drugs in normal cell environments and releases the anticancer drugs only in cancer cell environments exposed to light.

Photodynamic therapy is a method that kills cancer cells using a ‘photosensitizer’ that produces toxic reactive oxygen species in response to light.

To increase the production of reactive oxygen species by the photosensitizer, methods connecting heavy metals are often used, but connecting heavy metals causes side effects in the body.

The inherent toxicity of photosensitizers linked to heavy metals can impair the function of normal cells during blood circulation.

To solve the problem of normal cell function impairment, Professor Kwon’s team chose to encapsulate the photosensitizer with a ‘polymer-based nano-gel’ that is water-soluble and biocompatible.

The nano-gel protects the photosensitizer in normal environments, reducing toxicity in the body, and when light is irradiated on cancer cells requiring treatment, it activates and increases toxicity.

Lee Chaekyu, the first author and a combined master's and doctoral course researcher in the Department of Chemistry at UNIST, said, “The fact that the toxicity of the photosensitizer appears only at desired sites such as tumors using light is the result of understanding and precisely controlling the ‘reversibility of redox reactions’ and the ‘hydrophobic interactions of the nano-gel.’”

The nano-gel material developed this time consists of hydrophobic aromatic rings and hydrophilic polymer structures. The more hydrophobic rings there are, the more photosensitizer can be stably contained.

Also, the nano-gel material maintained its shape and size for 24 hours in both normal and cancer cell environments without light exposure.

Professor Kim Byung-su, Yonsei University.

Professor Byung-Soo Kim of Yonsei University, who jointly led the research, explained, “In the process of making the nano-gel using biocompatible polymers, we utilized the reversible redox reaction between thiol groups (-SH) and disulfide bonds (S-S). The reversible redox reaction that occurs when these two substances are close to each other greatly helps the nano-gel maintain its shape in dark environments.”

The nano-gel, which maintained its shape well, begins to operate when exposed to light in cancer cells.

The photosensitizer exposed to light generates a large amount of reactive oxygen species, and due to the effect of reactive oxygen species generation, the thiol groups inside the nano-gel are converted into sulfonic acid groups.

Sulfonic acid groups carry a negative charge and repel each other, causing the nano-gel to decompose. At this time, the toxic photosensitizer is released and attacks the cancer cells.

Professor Tae-Hyuk Kwon said, “We controlled the decomposition of the nano-gel containing the photosensitizer spatiotemporally by using light and the environment inside cancer cells. By increasing the selectivity so that the photosensitizer attacks only cancer, this will be an important molecular engineering strategy to reduce side effects in cancer patient treatment.”

The research was published online on the 12th in the prestigious chemistry journal ‘Angewandte Chemie International Edition.’

The research was conducted with support from the National Research Foundation of Korea (NRF) through the ‘Mid-career Researcher Support Project,’ TIPS, the National Cancer Center, Ulsan National Institute of Science and Technology, and others.

(Photo from right) Professor Kwon Tae-hyuk, Researcher Lee Chae-gyu, and Researcher Lee Chae-heon are taking a photo.

This content was produced with the assistance of AI translation services.