Liquid Crystal Based Optical pH Sensor for Esophageal Monitoring

Inserting pH probes into precise location of deep tissue yields important possibilities for biomedical science purposes and medical diagnosis. A micro/nanoscale pH sensor can be used as a diagnostic tool, a drug delivery module for point-of-care therapy, an imaging instrument or a combination of these three modalities depending on the sensor's design and range of sensitivity. We established the fundamental investigations for building up an optical pH sensor using a type of food-grade Lyotropic Liquid Crystal (LLC) nanoparticles. The pH sensor operates based on the liquid crystal reconfiguration upon variation of hydronium concentration in the surrounding solution. The mesophase matrices can be loaded with fluorescent agents as a drug and release it with different rates depending on the pH of the volume. The release rate can be used as a correlation factor in combination with the guest fluorescence optical attributes, such as color, and help us designing an accurate ratiometric pH sensor for monitoring esophageal acid reflux. Here, the release behavior of the mesophase loaded with Rhodamine 6G (a fluorescent model dye) was examined in standard buffers. The rapid response of a few milliseconds and pH sensitivity of the host mesophase between normal to acidic conditions in esophagus offers possibility for real time monitoring of pH values in such biological interface. The effect of pH, temperature, and dye concentration on the release rate were investigated in this research.