Hydrogel‐Integrated Quantum Dot Biointerfaces for Near‐Infrared Cardiac Photostimulation

Cardiovascular diseases are a leading global cause of mortality and bradycardia, a slow heart rate due to impaired cardiac conduction that poses significant health risks. While conventional pacemakers restore heart rate, their dependence on leads and battery lifetime remain major drawbacks. Cardiac photostimulation emerges as a transformative alternative, enabling wireless, battery‐free pacing. Here, a hydrogel‐integrated optoelectronic biointerface based on AgBiS 2 quantum dots (QDs) is presented for near‐infrared (NIR) cardiac photostimulation. The incorporation of a thin (≈0.1 µm), conductive (≈200 mS cm −1 ), and soft (390 kPa) PEDOT:PSS hydrogel enhanced ionic charge transfer by 52.8‐fold (reaching 28 µC cm −2 ) under pulsed infrared illumination compared to hydrogel‐free controls. The biointerface generated photocurrent loops between the stimulation and return electrodes that are predominantly capacitive and charge‐balanced, with minimal faradaic contribution (≈1%) and negligible thermal effects (Δ T ≈ 0.2 K). Cardiac motion analysis using a custom image‐processing algorithm confirmed modulation of beating frequency of cardiac tissue explants, ranging from bradycardic (<60 bpm) to physiological (≈120 bpm) rates. This work establishes a compelling strategy for integrating the optoelectronic properties of quantum dots with soft organic materials, paving the way for next‐generation, minimally invasive bioelectronic devices.