Optimal hyperosmotic agents for tissue immersion optical clearing in terahertz biophotonics

Abstract

In this work, a thorough analysis of hyperosmotic agents for the immersion optical clearing (IOC) in terahertz (THz) range was performed. It was aimed at the selection of agents for the efficient enhancement of penetration depth of THz waves into biological tissues. Pulsed spectroscopy in the frequency range of 0.1 to 2.5 THz was applied for investigation of the optical properties of common IOC agents. Using the collimated transmission spectroscopy in visible range, binary diffusion coefficients of tissue water and agent in ex vivo rat brain tissue were measured. IOC agents were objectively compared using two-dimensional nomogram, accounting for their THz-wave absorption coefficients and binary diffusion coefficients. The results of this study demonstrate an interplay between the penetration depth enhancement and the diffusion rate and allow for pointing out glycerol as an optimal agent among the considered ones for particular applications in THz biophotonics.

Terahertz radiation and the skin: a review

“…Various approaches for solving this inverse problem have been suggested and introduced recently for different geometries for experiments. [49][50][51][52][53] Thr final processing steps often include statistical analysis and dimensionality reduction of the observed data. 5,54 3 Structure and Properties of the Skin…”

In situ terahertz monitoring of an ice ball formation during tissue cryosurgery: a feasibility test

“…It is worth mentioning that several techniques enable increasing of low penetration depth of THz waves into living tissues. Among them are methods of immersion optical clearing, 19 which could also be combined with THz freezing depth detection. However, a list of hyperosmotic agents applied for tissue clearing act as cryoprotectors (e.g., glycerol, dimethyl sulfoxide, and propylene glycol), since they substitute the interstitial water.…”

“…1 To overcome this limitation, different approaches can be applied. Among them are such techniques as tissue dehydration, 15 paraffinembedding, 16 lyophilization, 17 compression, 18 immersion optical clearing, 19,20 and freezing. [21][22][23][24] It was demonstrated that the latter one helps to increase the THz-wave penetration up to 1 mm, changing at the same time dielectric properties of tissues in THz range.…”

Diagnosis of Glioma Molecular Markers by Terahertz Technologies

“…To increase the penetration depth of THz radiation into tissues, frozen and paraffin tissue slices [120] with formalin [121] or gelatin [122] fixation are used. Tissue dehydration is also carried out using immersion agents, which increase the depth of biological tissue measurements in the THz range [123][124][125][126][127].…”

“…THz radiation interaction with tumor tissue can be analyzed using the effective complex dielectric constant, which is a well-known model of the dielectric medium [25,[126][127][128][129].…”