A research team at Texas A&M University is using nanomaterials that absorb near-infrared (NIR) light to develop and manipulate light-responsive hydrogels. The NIR light to which the nanomaterials respond in the research enables therapeutic hydrogels to form in the body. Their functions inside the body include targeted drug delivery, among other biomedical applications. NIR radiation penetrates tissue at a greater depth than ultraviolet (UV) and visible light wavelengths, and with minimal side effects, making it well suited for the application. In previous work published in Advanced Materials (www.doi.org/10.1002/adma.201702037), the researchers presented their investigation of certain polymers that can interact with molybdenum disulfide (MoS2) nanosheets to form hydrogels. Building on the discovery, researcher Patrick Lee and professor Akhilesh Gaharwar used MoS2 nanoassemblies and a thermoresponsive polymer to form and control hydrogel under NIR light. MoS2, a class of 2D nanomaterials that has demonstrated low toxicity to cells and high NIR absorption, provided efficient photothermal conversion. When the researchers exposed MoS2 to NIR light, it connected with the polymer through click chemistry (essentially, small molecule reactions). This process activated interactions between the nanomaterial and the polymer. “This work leverages light to activate the dynamic polymer-nanomaterials interactions,” Gaharwar said. “Upon NIR exposure, MoS2 acts as a crosslink epicenter by connecting with multiple polymeric chains via defect-driven click chemistry, which is unique.” The conventional approach to forming crosslinked biomaterials uses a photo-initiator to generate reactive species such as free radicals when it is exposed to UV or visible light. This approach can harm the surrounding cells and tissue, the researchers said. The researchers demonstrated the use of NIR light to trigger hydrogels in vitro and in vivo. They said that the crosslinked hydrogel could potentially enable NIR-light-responsive release of encapsulated therapeutics. Hydrogels can help in tissue regeneration and drug delivery. However, once inside the body, they can be challenging to control. Because light can be confined to a predefined area and the intensity and duration of light exposure can be fine-tuned, light is a preferred energy source for controlling hydrogels in the research. Patrick Lee (shown) is working with associate professor Akhilesh Gaharwar to develop new methods for working with light-responsive hydrogels, which have applications in drug delivery and regenerative medicine. Courtesy of Texas A&M Engineering. NIR light additionally allows the internal formation of therapeutic hydrogels in the body for precise drug delivery. When used for cancer therapy, most drugs could be retained within the tumor, which could ease the side effects of chemotherapy. Moreover NIR light could be used to generate heat inside the tumors of patients to ablate cancer cells — a process known as photothermal therapy. Combining photothermal therapy and chemotherapy has been shown to be efficacious in destroying cancer cells. Light-responsive biomaterials like those being developed by the Texas A&M team could also be used for biomedical applications such as artificial muscle development, smart actuators, and 3D/4D printing. The research was published in Advanced Materials (www.doi.org/10.1002/adma.202101238).