Light-Powered Biohybrid Device Synchronizes Living Heart Tissue Without Metal Electrodes

At the University of California, Irvine, a thin film of layered polymer is doing something metal wires have long done clumsily: telling heart cells when to beat. Researchers there have built a biohybrid cardiac device that uses light, rather than metal electrodes, to control living heart tissue both electrically and mechanically. The work is described in a paper in the journal Cell Biomaterials.

The device couples engineered layers of optoelectronic polymer film, a material that converts light into electrical current, directly with living cardiac cells. When the film is pulsed with gentle, visible green light, it generates photocurrents. Those currents stimulate the heart cells to contract in synchrony, mimicking a healthy human heartbeat. The result is a soft, flexible, light-driven device meant to get around the long-standing limits of traditional electrode-based cardiac stimulation.

The construction is layered. Conjugated polymers are blended and stacked on an elastomeric polymer base. The topmost layer contains donor-acceptor junctions that produce photocurrents at the surface when illuminated. A further composite layer sits between that active layer and the biological environment, improving charge transport, stability in aqueous cell culture conditions, and compatibility with living cells.

Lead author Yuyao Kuang, who recently completed a Ph.D. in chemical and biomolecular engineering at UC Irvine, described the mechanism. Submerged in cell culture medium and illuminated, the polymer blend creates a charge-transfer state that drives ionic redistribution at the interface between polymer and electrolyte. The effect is a gentle, localized electrical stimulus for heart cells growing on the surface. Kuang stressed that this differs from optogenetics, which requires genetic modification to introduce light-sensitive proteins. Because the new approach needs no such change, it can be applied to native, unmodified cardiac tissue.

Co-author Herdeline "Digs" Ardoña, an assistant professor of chemical and biomolecular engineering at UC Irvine, called it a light-powered interface that speaks in electrical and mechanical pulses, the same language as the heart. She said it avoids the drawbacks of rigid electrodes, such as tissue damage or contamination risk over long-term use.

For testing, the team cultured neonatal rat ventricular myocytes, a standard research model for human cardiac cells, on the optoelectronic substrate. The cells were arranged in an anisotropic, micropatterned layout that closely mimics the organized fiber architecture of native heart muscle. The researchers then shaped the construct into a muscular thin film with a cantilever geometry. That shape lets them watch and quantify the bending produced by each contraction in response to light pulses, measuring electrical pacing and mechanical function together.

Ardoña identified pharmaceutical drug screening and cardiac disease research as the two most immediately impactful applications. Non-animal laboratory testing of a drug's effect on heart tissue currently relies on rigid electrodes to pace contractions, which can introduce artifacts and contamination, or on simplified models that lack the complex electromechanical environment of a beating heart.

With the Irvine platform, a candidate drug can be applied directly to living, light-paced tissue. Researchers can then observe in real time how it affects the response to external electrical pacing and mechanical strain, the tissue's contractile strength, and even long-term structural remodeling of protein networks inside cells, all in one integrated experiment. According to Ardoña, that gives a more realistic picture of a drug's true effect than other existing in vitro tools.

The researchers also point toward potential treatment of life-threatening arrhythmias, though the results so far come from lab cell cultures rather than patients. Drug screening and disease modeling are the nearer-term uses to watch.