Diffusion characteristics of ethylene glycol in skeletal muscle

Abstract

Part of the optical clearing study in biological tissues concerns the determination of the diffusion characteristics of water and optical clearing agents in the subject tissue. Such information is sufficient to characterize the time dependence of the optical clearing mechanisms-tissue dehydration and refractive index (RI) matching. We have used a simple method based on collimated optical transmittance measurements made from muscle samples under treatment with aqueous solutions containing different concentrations of ethylene glycol (EG), to determine the diffusion time values of water and EG in skeletal muscle. By representing the estimated mean diffusion time values from each treatment as a function of agent concentration in solution, we could identify the real diffusion times for water and agent. These values allowed for the calculation of the correspondent diffusion coefficients for those fluids. With these results, we have demonstrated that the dehydration mechanism is the one that dominates optical clearing in the first minute of treatment, while the RI matching takes over the optical clearing operations after that and remains for a longer time of treatment up to about 10 min, as we could see for EG and thin tissue samples of 0.5 mm.

Optical and structural properties of biological tissues under diabetes mellitus

“…Therefore, the change of the agent diffusion rate in a tissue during a certain time interval can reflect the change of the tissue structure and, thus, can be used as a biomarker of the glycation degree [40, 95,159]. The study of permeability of biological tissues for different agents is aimed at extracting information on the mechanisms of interaction of tissues with different chemicals, on the transport of drugs in tissues, on the effect of the agents on the optical, diffusion, morphological, and functional properties of biological tissues [48,49,52,146,147,[160][161][162]. These data are necessary for efficient application of different pharmacological preparations to treat diabetes mellitus and for developing noninvasive optical methods of disease diagnostics and monitoring [48,163], since efficiency of treatment (diagnostics) is determined by drug (agent) diffusion rate, i.e., the time during which the drug (agent) molecules reach the target part of the organism.…”

Software development for estimation of optical clearing agent’s diffusion coefficients in biological tissues

“…This mechanism is in general fast, usually contained within the first two minutes of treatment [18]. At the same time, but with a slower pace, the agent in the solution begins to diffuse into the outer layers of the tissue [18]. The difference in viscosity properties and molecular size between water molecules and agent molecules provide that the diffusion of agent into deeper layers of tissue to create the RI matching mechanism takes a longer time [10].…”

“…This is the dehydration mechanism, which initiates immediately as the treatment is applied to the tissue sample. This mechanism is in general fast, usually contained within the first two minutes of treatment [18]. At the same time, but with a slower pace, the agent in the solution begins to diffuse into the outer layers of the tissue [18].…”

“…Such technique originates a decrease in the natural scattering coefficient and an increase of the natural scattering anisotropy factor of the tissue, creating a temporary transparency that can be later reversed [12][13]. Such temporary tissue transparency is obtained by a stimulated tissue dehydration and consequent replacement of the water in the interstitial space by a biocompatible agent that has a higher RI, better matched to the RI of the other tissue components [14][15][16][17][18]. Recent research work demonstrated that this technique can be used in vivo with imaging techniques such as optical coherence tomography [19], speckle methods to monitor blood flow in dermis or cortical tissues [20], and second harmonic generation imaging (SHG) to improve tissue depth and resolution [21].…”

“…This way, the individualization of the two mechanisms needs a refined method that produces accurate results. Such a method is described in literature [8,13] and we have recently proven its concept experimentally as described in our recent publications [7,10,18]. In those papers we describe how we have used thickness and collimated transmittance (Tc) measurements made from thin muscle samples under treatment with glucose and ethylene glycol (EG) solutions to estimate the diffusion time, diffusion coefficient and viscosity of these agents in muscle.…”