Caltech unveils enzyme-powered bubble robots for tumor targeting

Tuesday 03 February 2026 - 12:50

By: Dakir Madiha

Caltech unveils enzyme-powered bubble robots for tumor targeting

Scientists at the California Institute of Technology and the University of Southern California have pioneered microscopic bubble-shaped robots that autonomously seek out tumors and deliver anticancer drugs, marking a significant leap in practical medical microrobotics. Led by Wei Gao, a professor of medical engineering at Caltech, the research team detailed their breakthrough in a study published on February 2, 2026, in Nature Nanotechnology. These bubble robots reduced bladder tumor weight in mice by about 60 percent over 21 days, outperforming traditional drug delivery methods.

The innovation lies in its remarkable simplicity, diverging from prior techniques that demanded intricate 3D printing and cleanroom fabrication. Researchers generated thousands of protein-shelled microbubbles by sonicating a solution of bovine serum albumin, a widely used protein. These bubbles double as robotic structures and ultrasound imaging contrast agents. "We wondered if we could push simplicity further by turning the bubble itself into a robot," Gao explained. "They're easy to make, highly biocompatible, and can burst on demand."

Propulsion stems from urease enzymes anchored unevenly on the bubble surface. The enzyme reacts with urea, a common metabolic waste throughout the body, producing ammonia and carbon dioxide. This chemical imbalance generates a net thrust, propelling the robots forward. The team developed two variants: one incorporating magnetic nanoparticles for external magnet guidance alongside ultrasound tracking, and another enabling fully autonomous navigation. The latter uses catalase enzymes that respond to elevated hydrogen peroxide levels in tumors, driving chemotactic movement toward the malignancy. "No imaging or external control is needed; the robot is smart enough to find the tumor," Gao noted.

Upon reaching the target, focused ultrasound bursts the bubbles, releasing the drug payload while mechanical forces enhance tissue penetration. "This bubble robot platform is straightforward yet packs in everything required for therapy: biocompatibility, controllable motion, imaging guidance, and an on-demand trigger for deeper drug infiltration," said lead author Songsong Tang, soon to join the University of Science and Technology of China as a professor. Building on the team's December 2024 work in Science Robotics on more complex hydrogel microrobots, this design edges closer to real-world clinical use.