Optical clearing effect on gastric tissues immersed with biocompatible chemical agents investigated by near infrared reflectance spectroscopy

In order to understand the role of water desorption in optical clearing effect on gastric tissues after the application of hyperosmotic agents, dynamics of water loss in porcine stomach administrated with glycerol was investigated with the near infrared reflectance spectroscopy. It is found that the progress of optical clearing of various samples corresponds very well with the individual pattern of water desorption. The changes in optical properties are almost linear with time in frozen-thawed cardiac mucosa immersed in 80% glycerol whilst the water inside the tissue is displaced at the same rate. For the same samples immersed in 50% glycerol, after 30 min, when the dehydration equilibrates with time, optical clearing tends to lever out. The overall water loss in frozen porcine stomach at 60 min after the immersion of 80% and 50% glycerol is approximately 38% and 13%, respectively. The more significant effect of optical clearing by 80% glycerol is due to its high refractive index and high dehydration capability. In fresh pyloric mucosa samples, treated with 50% glycerol through the topical application, the changes of optical properties at the initial stage are very slow due to the mucous barrier. However, once the solution has penetrated into tissue, optical clearing is achieved significantly with time. The results indicate that optical clearing induced by hyperosmotic agents is strongly correlated with dehydration.