Laser-irradiated Coating Augments Nonsurgical Treatment of Obesity

A multi-institutional research team in South Korea has enhanced the existing functionality of appetite-suppressing implants in the stomach with photodynamic therapy, coating such an implant with light-activated dye that kills cells that produce ghrelin, known as the “hunger hormone.” The researchers used and coated intragastric satiety-inducing devices, or ISDs in the work. The researchers in the current work designed and introduced these implants in 2019.

Appetite-suppressing implants, which can act like miniature balloons in the stomach, are nonsurgical alternatives for obesity treatment. These implants can be inserted into the stomach through the mouth. ISDs consist of a stent that lodges in the lower esophagus and is attached to a disk that rests in the opening to the stomach. The disk contains a hole in its center that lets food through.

Though tests in pigs showed that the ISDs lowered food intake and weight gain by enhancing the feeling of fullness and reducing levels of ghrelin, which is produced by cells near the top of the stomach, the device caused complications, including acid reflux.

The current work aimed to further suppress ghrelin by first coating an ISD with a compound that could kill some of the ghrelin-producing cells upon light interaction. The researchers’ design in the work was to then remove the implant to avoid the side effects associated with their initial device design.

An implant (blue and gray) creates a feeling of fullness by pressing on the stomach and, when activated by a laser (black), kills cells that produce ghrelin, called the 'hunger hormone.' The research advances work from 2019 that led to the development of a device to treat obesity in a nonsurgical way, but that yielded side effects including acid reflux. Courtesy of ACS Applied Materials & Interfaces.

The researchers coated ISDs with methylene blue, which is a photosensitizer and FDA-approved drug. They then placed them in the stomachs of young pigs. When they exposed the coated ISDs to laser light, the coating released singlet oxygen that killed ghrelin-producing cells located nearby and then rapidly disappeared.

After one week, the treatment reduced ghrelin cells and body weight gain by half compared to an untreated pig, although the researchers said that these differences declined in the following weeks unless the light treatment was repeated. Still, with further development, they believe the procedure could become a minimally invasive treatment to help obese patients lose weight.

The paper authors were supported by the Korea Medical Device Development Fund grant funded by the Korean government.

The research was published in ACS Applied Materials & Interfaces (www.doi.org/10.1021/acsami.2c00532).