The mixture of glycerin with tartrazine: a solution to reversibly increase tissue transparency for in vitro quantitative phase imaging

Abstract: Thick tissue sections strongly scatter and absorb light, which limits transmission-based label-free examination via quantitative phase imaging (QPI) modalities. Here we introduce a simple, room-temperature optical clearing medium - glycerol and tartrazine solution (GTS; 60 percent glycerol, 10 percent tartrazine) - that increases the transparency of 50-80 micron murine liver and kidney slices while preserving tissue morphology and enabling rapid, label-free quantitative phase imaging. Using Fourier ptychographic microscopy (FPM) and lensless digital holographic microscopy with pixel super-resolution (LDHM-PSR), we demonstrate markedly improved high-throughput visualization of microstructural features after GTS immersion compared with phosphate-buffered saline (PBS). The improvement is confirmed quantitatively by a significant increase in the one-pixel-lag autocorrelation of phase-gradient values, indicating reduced scattering-driven phase artifacts and enhanced structural continuity in reconstructed phase maps. We further show that GTS is stable for months at room temperature, provides instant yet durable clearing that improves over time, and can be removed by brief PBS washing, enabling downstream multimodal analyses on the same specimen. Finally, we benchmark GTS against the state-of-the-art clearing agent Ce3D, highlighting GTS as a low-cost, safe, operationally straightforward alternative with strong potential for routine, high-throughput QPI-based histopathology workflows.