Research conducted at the University of São Paulo’s Chemistry Institute demonstrated the utility of near-infrared and infrared light for use as catalysts in the control of enzymes. The work holds implications for the noninvasive treatment of diseases such as Parkinson’s and Alzheimer’s.

São Paulo researchers investigated the activity of enzymes immobilized on gold nanoparticles controlled by infrared laser radiation. That process is known as plasmonic biocatalysis. Enzymes can be controlled remotely with light by immobilizing them on the surface of nanoparticles, where they are then irradiated by laser light. The nanoparticles absorb the energy and release it back in the form of heat or electronic effects, which triggers or intensifies the enzymes’ catalytic activity.

The team used a lipase (CALB) as its model enzyme, which it immobilized on gold nanoparticles in the shapes of spheres and stars, said lead author Heloise Ribeiro de Barros, a postdoctoral researcher at the University of São Paulo. The infrared laser accelerated the enzyme’s activity in a noninvasive way by irradiating it with external light, she said.

The study demonstrated that it isn’t just the composition of the material, but the geometry as well that holds influence over the effect of the nanoparticles on the enzyme.

“The enzymatic activity was significantly enhanced when the lipase was immobilized on gold nanostars, displaying an increase of up to 58%,” Ribeiro de Barros said. “In comparison, the gold nanospheres promoted a much smaller increase of 13%.”

The larger increase, Ribeiro de Barros said, corresponded to the effect of resonance between the surfaces of the nanostars and radiation from the laser.

The magnitude considered here is localized surface plasmon resonance (LSPR). Whereas the LSPR of the nanospheres absorbs at 525 nm, the nanostars absorb at 700 nm, much closer to the infrared laser wavelength (808 nm).

“The incident light sets off energy-driven processes in the gold nanoparticles, such as a rise in temperature or electronic effects, and this affects the properties of the enzymes that are immobilized on their surfaces,” Ribeiro de Barros said. “It was possible to conclude that localized photothermal heating on the surfaces of the gold nanostars promoted by LSPR excitation led to enhanced lipase biocatalysis. This conclusion can be extended to other combinations of enzymes and plasmonic nanoparticles.”

The technology has a broad range of potential applications, including biocatalysis to accelerate industrial-scale chemical reactions and in vivo control of disease-causing enzymes.

“From the medical standpoint, the main purpose of the study was to point to solutions in the near future for the treatment of diseases without the need for invasive surgery with a specific spatial and temporal approach to avoid the side effects of current methods,” Ribeiro de Barros said.

The research was published in ACS Catalysis (www.doi.org/10.1021/acscatal.0c04919).