Effect of dextran-induced changes in refractive index and aggregation on optical properties of whole blood

Abstract

The purpose of the present study is to investigate systematically the mechanisms of alterations in the optical properties of whole blood immersed in the biocompatible agent dextran, and to define the optimal concentration of dextrans required for blood optical clearing in order to enhance the capability of light penetration depth for optical imaging applications. In the experiments, dextrans with different molecular weights and various concentrations were employed and investigated by the use of the optical coherence tomography technique. Changes in light attenuation, refractive index and aggregation properties of blood immersed in dextrans were studied. It was concluded from the results that the mechanisms for blood optical clearing are characteristic of the types of dextrans employed, their concentrations and the application stages. Among the substances applied, Dx500 at a concentration at 0.5 g dl(-1) gives the best result in improving light penetration depth through the blood. The increase of light transmission at the beginning of the addition of dextrans is mainly attributed to refractive index matching between the scattering centres and the ground matter. Thereafter, the transmission change is probably due to a dextran-induced aggregation-disaggregation effect. Overall, light scattering in the blood could be effectively reduced by the application of dextrans. It represents a promising approach to increasing the imaging depth for in vivo optical imaging of biological tissue, for example optical coherence tomography.

Effects of optical clearing agents on noninvasive blood glucose monitoring with optical coherence tomography: a pilot study

“…Therefore, BGC can be measured by analyzing the glucoseinduced changes in the OCT signal slope detected from the biological tissues, such as the dermis area of the skin. 38 The skin consists of three major layers: stratum corneum (SC), epidermis, and connective tissue of dermis, which is the only layer containing a developed blood microvessel network. The OCT technique allows measurement of glucoseinduced changes in the skin-scattering coefficient directly from the dermis.…”

Optical clearing of flowing blood using dextrans with spectral domain optical coherence tomography

“…7 Our previous OCT study demonstrated that dextrans with various molecular weights (MWs) led to optical clearing in stationary blood samples from 52.1% to 150.5%. 8,9 The optical properties of blood are altered by two effects induced by dextrans: refractive index matching and erythrocyte aggregation. [9][10][11] However, the effect of erythrocyte aggregation on optical clearing of blood was not mentioned in Brezinski's work, 7 where only index matching was discussed for circulation of blood in a high flow rate using only one dextran with MW 70 kDa.…”

Elliptical optical tweezers for trapping a red blood cell aggregate

“…Scattering properties are dependent on the refractive index of the scatterers as well as that of the base medium (extracellular medium or blood plasma) which affect blood osmolarity [1]. Scattering and light propagation are also affected by the size and shape of RBCs and their aggregation properties [1]- [5]. Optical clearing is a promising technique to decrease light scattering in a biological tissue [6].…”

“…However, optimal concentrations of OCAs serve to reduce the scattering properties of blood [7], which have been studied extensively both experimentally [8]- [10] and theoretically [11], [12]. In addition, several groups are investigating the optical properties of whole blood [1], [13], [14] as well as RBC aggregates at the whole blood level [3]- [5] and in RBC suspensions [15]. This helps the analysis and understanding of optical measurement results.…”