Tracing Selenium Uptake in Wheat Leaves via Liposome-Mediated Delivery: A Confocal Microscopy and Synchrotron Micro-X-ray Fluorescence Insight

The integration of nanoencapsulation techniques with foliar application presents a promising approach to enhance selenium (Se) biofortification in agriculture. This study examined the foliar uptake of liposome-encapsulated Se in wheat leaves (Triticum aestivum) using synchrotron-based micro-X-ray fluorescence (μ-XRF) and confocal microscopy. μ-XRF mapping showed Se accumulation at leaf edges after 24 h, suggesting initial uptake via stomata, while free Se was absorbed and transported more rapidly, highlighting the slow-release effect provided by liposomal encapsulation, longer than the analyzed time. No immediate translocation of Se to the stem was observed, suggesting that more time is required for this internal movement. Micro-X-ray absorption near-edge structure (μ-XANES) speciation analysis demonstrated that Se was metabolized into organic forms within the plant. Finally, confocal fluorescence microscopy confirmed liposome absorption through the plant surface within 24 h, corroborating the μ-XRF findings. These results are crucial for optimizing liposome formulation to maximize Se transfer to edible parts.