Natalia A. Trunina

Optical Clearing for OCT Image Enhancement and In-Depth Monitoring of Molecular Diffusion

In this paper, we overview the basic principles, recent results, advantages, limitations, and future of the optical clearing method in application to many fields of biology and medicine. We also discuss the possibility of noninvasive assessment of molecular diffusion in tissues using the optical coherence tomography technique. Issues of safety and toxicity of application of different endogenous and exogenous molecules to tissues are outlined.

Finger tissue model and blood perfused skin tissue phantom

Measurements of optical properties of fingernail and underlying tissues using OCT are presented. Review and measurements of Raman spectra of tissue and phantom compounds were done. Updating of modeling algorithm for scattering coefficient calculation on the basis of integrating sphere measurements accounting for particle size-distribution was also done. The adequate fingernail and underlying tissue optical model at 830 nm was evaluation. Tissue phantoms potentially suitable for calibration of Raman instrumentation for glucose sensing were designed and tested on the basis of epoxy resin, TiO2-nanoparticles and micron-sized silica particles with the capillary net-work.

Photoinduced cell morphology alterations quantified within adipose tissues by spectral optical coherence tomography

Abstract. Morphological changes of the adipose tissue at phototreatment are studied in vitro using optical coherence tomography. The 200 to 600 μm fat tissue slices are used in the experiments. The observed change in the tissue structure was associated with fat cell lipolysis and destruction caused by the photodynamic effect. It is found that overall heating of a sample from room to physiological temperature leads to deeper and faster morphology tissue changes if other processing conditions are kept constant. These data support the hypothesis that photodynamic/photothermal treatment induces fat cell lipolysis during some period after treatment.

OPTICAL COHERENCE TOMOGRAPHY OF ADIPOSE TISSUE AT PHOTODYNAMIC/PHOTOTHERMAL TREATMENT IN VITRO

Temporal changes in structure and refractive-index distribution of adipose tissue at photodynamic/photothermal treatment were studied with OCT in vitro. Ethanol–water solutions of indocyanine green (ICG) and brilliant green (BG) were used for fat tissue staining. CW laser diode (808 nm) and LED light source (442 and 597 nm) were used for irradiation of stained tissue slices. The data received supporting the hypothesis that photodynamic/photothermal treatment, induces fat cell lipolysis during a certain period of time after light exposure.

OCT monitoring of diffusion of water and glycerol through tooth dentine in different geometry of wetting

In our previous work optical coherence tomography (OCT) has been proved to be a useful tool for monitoring of diffusion of chemical agents (water, glycerol) within human tooth dentine. Such diffusion studies are interesting for tooth therapy (diffusion of medicinal preparations) and cosmetics (chemical whitening agents). Here we compare different wetting schemes in which the sample is either merged in the liquid agent so that the probe beam is to pass through a layer of liquid, or subjected to wetting through a special window from the back side. In spite of certain difference revealed, the order of magnitude of the diffusion time constant and the permeability coefficient are shown to be the same in both cases.

Study of water diffusion in human dentin by optical coherent tomography

The diffusion of chemical agents in dental tissues is of interest for many problems of dental tissue physiology (diffusion of liquor and water), dental healing (diffusion of preparations), and cosmetic dental treatment (diffusion of whitening agents). The water diffusion in samples of human dentin was monitored using optical coherent tomography (OCT). This diffusion manifests itself as a change in the slope and amplitude of the OCT signal from the sample. It is shown that the average dentin permeability with respect to water is (15.11 ± 21.73) × 10−6 cm/s. These experimental results demonstrate the OCT efficiency for studying the diffusion in hard biological tissues.

Monitoring of TiO

Penetration of nanoparticles into tooth enamel and dentine is of significant interest upon solving problems related to reduction of tooth sensitivity, enamel strengthening, disinfection, restoration as well as cosmetic bleaching. This paper aims at studying the process of nanoparticle penetration into tooth enamel and dentine samples using nonlinear optical microscopy and at investigating the influence of the same nanoparticles on the generation of free radicals using the electronic paramagnetic resonance technique. We presented in vitro measurements demonstrating that nonlinear optical microscopy, namely, two-photon-excited autofluorescence, second harmonic generation, and hyper-Rayleigh scattering-based microscopy can be used for monitoring and imaging TiO2 and ZnO nanoparticle penetration into tooth tissues. The results indicate that ZnO nanoparticles penetrated into the human tooth enamel and dentine up to a depth of 12 and 45 μm, respectively, and TiO2 nanoparticles penetrated into dentine to a depth of 5 μm. The penetration mainly occurs along either enamel rods or dentinal tubules. Permeability of the dentine was found to be higher than that of enamel (for ZnO particles) by one order of magnitude and the diffusion rate was affected by the particle size being higher for smaller, submicron particles (ZnO) than for micron-sized aggregates (TiO2). Nitrogen-doped TiO2 nanoparticles generate more radicals in the UV-VIS spectral range in comparison to pristine TiO2 (anatase) and ZnO nanoparticles, therefore, they can potentially be used for disinfection purposes of superficial tooth areas (up to 5-μm deep).

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Time variation of the adipose tissue refractive index under photodynamic treatment was studied using OCT. Fat tissue slices 200-500 μm thick were used in in vitro experiments. To stain the fat tissue we used water-ethanol solutions of indocyanine green (ICG) and brilliant green (BG) with the concentration 1 mg/ml and 6 mg/ml, respectively. The CW laser diode (VD-VII DPSS, 808 nm) and the dental diode irradiator Ultra Lume Led 5 (442 and 597 nm) were used for irradiation of tissue slices. The irradiation time was 5 min for the laser and 15 min for the diode lamp. The experiments were carried out at room temperature. It was discovered the immersion optical clearing of fat tissue slices due to fat cell lipolysis under photodynamic treatment. Released cell content works as an immersion agent, thus the relative refractive index of tissue scatterers decreasing with the time elapsed after the treatment. These data support the hypothesis that photodynamic treatment induces fat cell lipolysis for some period after treatment.

and ZnO Nanoparticle Penetration Into Enamel and Dentine of Human Tooth IN VITRO and Assessment of Their Photocatalytic Ability

Monitoring of agent diffusion within tooth tissues is important in a wide context of tooth therapy (diffusion of medicinal preparations) and cosmetics (chemical whitening agents). We report here the results of optical coherence tomography (OCT) monitoring of diffusion of water and glycerol as clearing agents in samples of human tooth tissue. The diffusion process is analyzed by monitoring the changes in the OCT signal slope and the depth-resolved amplitude of OCT signal from a sample. Slow temporal kinetics of the mean attenuation coefficient was measured to monitor a saturable optical clearing due to the diffusion of the agent. The average permeability coefficient was estimated by dividing the measured thickness of the selected region by the time it took for the agent to diffuse through. The experimental results demonstrate that OCT can be an efficient tool in the study of agent diffusion through hard tissues.

Time variation of adipose tissue refractive index under photodynamic treatment: in vitro study using OCT

Dentinal permeation is of interest in a wide context of tooth care and treatment, in particular, tooth color improvement using combination of chemical whitening agents and light activation. A simple model of dentinal permeation accounting for the morphology of human tooth dentine and including dentinal tubules, more dense and homogeneous peritubular dentine, and less dense and less homogeneous intertubular dentin is proposed. Calculation of permeability of dentine layer is carried out for H2O and H2O2 versus the tubule diameter and tubule density taken from the microphotograph analysis. This opens the possibility to calculate the distribution of permeability over the tooth surface taking into account the variations of tubule diameter and density as well as those of the diffusion coefficients and layer thickness