New way to assemble bionanoparticles via shrinkage of light-induced bubbles

The process of building structures with increasing complexity, called bottom-up processing, is a common theme in many biological functions, such as the synthesis of DNA and vesicles for metabolism and neural sensing. The creation and measurement of these nanobiomaterials often require pico-scale precision. The new work, taking its cues from the physics of bubble gum, reports a new way to achieve these goals.

Ueda et al. present a new method for producing macroscopic-assembled structures of nanoparticles from protein molecules. They took advantage of the foaming properties of proteins and used an asymmetric pressure-driven flow in a microchannel to facilitate light-induced bubble (LIB) generation by assembling nanoparticles that exhibit broadband light absorption.

The experimental system was inspired by the inflation and shrinkage of bubblegum. Studying the dynamics of such a system allowed the group to measure changes in bubble behavior across different conditions. Instead of directly pumping air into the bubbles, the authors turned to using infrared photon pressure and the photothermal effect to control the bubbles. The size of the resulting assembly can be controlled by changing the amount of protein. For instance, in more diluted protein solutions, shrinking a single LIB can trigger microscale aggregation of metallic nanoparticle-fixed beads.

“When the amount of protein was large, it was surprising that multi-bubbles were efficiently generated like whipping egg whites to make meringue for cake, and that the foaming property of proteins is maintained even in the micron region,” said Dr. Takuya Iida, an author on the paper.

The authors state their findings can be used not only for assembling broadband optical nanocomposites but also for detecting an extremely small amount of protein without the use of fluorophores.

Iida said the group hopes their findings will provide paths forward in areas such as point-of-care medical testing, food safety and materials informatics.

Source: “Microflow-mediated optical assembly of nanoparticles with femtogram protein via shrinkage of light-induced bubbles,” by Mayu Ueda, Yushi Nishimura, Mamoru Tamura, Syoji Ito, Shiho Tokonami, and Takuya Iida, APL Photonics (2019). The article can be accessed at https://doi.org/10.1063/1.5079306 .