Light-driven oxygen generation by thylakoid membranes attenuates reperfusion-induced apoptosis in human cardiomyocytes

Myocardial ischemia-reperfusion injury (IRI) remains a major cause of cardiomyocyte loss despite timely restoration of blood flow. Biomaterials capable of locally supplying oxygen represent a promising strategy to mitigate ischemic damage while limiting the detrimental effects of reperfusion. Here, isolated spinach thylakoid membranes are investigated as a cell-free, light-responsive biomaterial for oxygen generation in a human in vitro model of oxygen-glucose deprivation/reperfusion (OGD/R). Across three independent thylakoid preparations, illuminated membranes sustained oxygen evolution for more than 1.5 h at 25 °C, with an initial rate of approximately 60 nmol O₂ × mL−1 × min−1 at 100 μg chlorophyll × mL−1 and cumulative oxygen production of about 800 nmol O₂ × mL−1. Because photosynthetic activity rapidly declined at 37 °C, a spatially separated platform was developed in which thylakoids and AC16 human cardiomyocytes were maintained in independent compartments connected through a shared gaseous phase, enabling remote oxygen delivery during ischemia. Photosynthetic oxygen supplementation markedly attenuated reperfusion-induced apoptosis, reducing the fraction of cleaved caspase-3-positive cells from 71.52 ± 12.37% in untreated OGD/R cultures to 15.79 ± 3.94%, the latter comparable to normoxic controls. These findings demonstrate that isolated thylakoid membranes preserve the essential functionality of oxygenic photosynthesis, providing a simple, cell-free platform for oxygen supplementation. Although improved thermal stability will be required for clinical translation, this work establishes a proof of concept that a plant-derived platform can modulate IRI, presenting thylakoid membranes as biomaterials for light-triggered oxygen delivery.