When a beating heart slips into an irregular, life-threatening rhythm, the treatment is well known: deliver a burst of electric current from a pacemaker or defibrillator（去纤颤器）. But because the electricity itself can cause pain, tissue damage and other serious side-effects, a Johns Hopkins-led research team wants to replace these jolts with a kinder, gentler remedy: light. In a paper published Aug. 28 in the online journal Nature Communications, five biomedical engineers from Johns Hopkins and Stony Brook universities described their plan to use biological lab data and an intricate computer model to devise a better way to heal ailing（生病的） hearts. Other scientists are already using light-sensitive cells to control certain activities in the brain. The Johns Hopkins-Stony Brook researchers say they plan to give this technique a cardiac twist so that doctors in the near future will be able to use low-energy light to solve serious heart problems such as arrhythmia（心率不齐）.

"Applying electricity to the heart has its drawbacks," said the project's supervisor, Natalia Trayanova, the Murray B. Sachs Professor of Biomedical Engineering at Johns Hopkins. "When we use a defibrillator, it's like blasting open a door because we don't have the key. It applies too much force and too little finesse（策略，纤细）. We want to control this treatment in a more intelligent way. We think it's possible to use light to reshape the behavior of the heart without blasting it."

In this illustration, the "optrode" at left delivers blue light to the heart via a fiber-optic tip. In the enlargement at right, a heart cell (large red oval) contains an implanted light-sensitive "opsin" protein (blue oval) that works alongside the heart's own proteins (yellow ovals). This teamwork allows the cell to convert light energy into an electric kick that triggers a healthy heartbeat. Graphic by Patrick M. Boyle.

To achieve this, Trayanova's team is diving into the field of optogenetics, which is only about a decade old. Pioneered by scientists at Stanford, optogenetics refers to the insertion of light-responsive proteins called opsins into cells. When exposed to light, these proteins become tiny portals within the target cells, allowing a stream of ions -- an electric charge -- to pass through. Early researchers have begun using this tactic to control the bioelectric behavior of certain brain cells, forming a first step toward treating psychiatric disorders with light.

In the Nature Communications paper, the researchers reported that they had successfully tested this same technique on a heart -- one that "beats" inside a computer. Trayanova has spent many years developing highly detailed computer models of the heart that can simulate cardiac behavior from the molecular and cellular levels all the way up to that of the heart as a whole. At Johns Hopkins, she directs the Computational Cardiology Lab within the Institute for Computational Medicine.