Synergistic effect of hyperosmotic agents of dimethyl sulfoxide and glycerol on optical clearing of gastric tissue studied with near infrared spectroscopy

In an effort to find an effective concentration that could minimize the side effect for clinical applications, and to understand the potential synergistic effect of hyperosmotic agents on optical clearing of gastric tissues, porcine stomach tissues (pyloric mucosa) applied with a mixed solution of glycerol and dimethyl sulfoxide (DMSO) are investigated with near infrared reflectance spectroscopy. Five chemical solutions, containing 80% glycerol, 50% DMSO, 50% glycerol with 10% DMSO, 20% DMSO and 30% DMSO, respectively, are prepared and studied; all of which show significant improvement in light transmittance, and thus reduction of the light scattering of tissue. It is found that, among the solutions investigated, 50% glycerol with 30% DMSO achieves the best clearing effect on the improvement of light penetration. Light transmittance is increased approximately 29% and diffuse reflectance decreased approximately 31% at 30 min after the topical application of 50% glycerol with 30% DMSO. This solution shows significantly stronger effect than 80% glycerol on optical clearing even though they have the same osmolarity. 80% glycerol leads to 23% increase of light transmittance and 24% decrease of diffuse reflectance. The mixed solution of 50% glycerol and 20% DMSO has less osmolarity than the solution of 80% glycerol, but they achieve a similar degree of optical clearing. In other words, the clearing effect of glycerol is enhanced by adding DMSO into it. It is suggested that membrane penetration and carrier effect of DMSO probably accounts for this synergistic effect.