Chemically Modified Nanosheets with High Potency for Biomedical Applications: IISc

Surface modifications of two-dimensional molybdenum disulfide nanosheets can lead to highly potent applications such as drug delivery to diseased cells, according to a study by the Indian Institute of Science (IISc) Department of Organic Chemistry (OC) and Materials Research Center (MRC). .

Depending on the application, nanomaterials usually need to be modified or adapted to improve efficiency. They are chemically modified by functionalization, in which ligands (small or large molecules) are attached to the surface of the nanomaterial.

“Thiols can be exchanged with naturally occurring thiols in biological systems, which could allow for the release of drugs bound to these nanosheets. It was also found that these chemically modified nanosheets can be safely used in living cells,” reads the press release shared by the IISc. In the new study, the researchers modified the surface of 2D MoS2 nanosheets with thiol (sulphur-containing) ligands.

“Our study shows that thiol exchange is effective on 2D MoS2 nanosheets and the nanomaterial is stable in the presence of various biomolecules. This is an important observation as this nanomaterial will be of great benefit for biomedical applications such as drug delivery,” said Mrinmoy De, associate professor at the Institute of Organic Chemistry and senior author of the study published in ACS Nano.

To modify the surface of the 2D MoS2 nanosheets to create a functional version (BOD-MoS2), the team first used a fluorescent thiol called boron-dipyrromethene (BOD-SH). They then tested the possibility of thiol-to-thiol swapping on BOD-MoS2 using glutathione (GSH), a naturally occurring thiol that is abundant in cancer cells. “GSH molecules swapped places with BOD-SH on the surface of the nanosheet – a process they confirmed using fluorescence techniques.”

Researchers attached an anti-cancer drug doxorubicin (DOX) to the nanosheet surface. They found the possibility of a thiol exchange between GSH and DOX, allowing DOX to be delivered to the diseased site. “Because the exchange only occurs in the presence of high levels of GSH in diseased cells, drugs like DOX can be targeted to cancer cells without affecting normal cells, potentially reducing side effects as well.”

Previous efforts have focused on using gold nanoparticles for such biomedical applications, according to the researchers. Nevertheless, these nanoparticles are expensive and have limited efficiency due to their nonselectivity between monothiols and disulfides.

“Our experiments show that 2D MoS2 nanosheets can be an effective substitute for gold nanoparticles, and they will be of great use in the field of nanomedicine,” said Pradipta Behera, a researcher at IISc. In addition, the MoS2 nanosheets were found to be stable in biofluids. They also have a larger surface area than gold nanoparticles, meaning they can be more efficient.

Going forward, the team said they plan to improve the nanomaterial’s stability in the presence of various thiol-containing liquids and explore alternative surface modification approaches to adapt the nanosheets for other applications. “This work on 2D MoS2 nanosheets can be developed in the future as an alternative to RNA and DNA delivery applications that may be useful for detecting and treating infections like COVID-19,” Behera added.