We are very pleased and honored to have the opportunity to dedicate a series of papers to our dear friend, mentor and colleague, Valery V. Tuchin, to commemorate the occasion of his 70th birthday. Prof. Tuchin is one of the founders of the Biophotonics field whose remarkable work has advanced the frontiers of light- Tissue interaction. He is best known for his textbooks such as Tissue Optics: Light Scattering Methods and Instruments for Medical Diagnosis and Handbook of Biophotonics, but his research encompasses virtually all aspects of optical measurements in biomedicine with incredible 400+ peer-Reviewed publications.

For at least two decades, nanoparticles have been investigated for their capability to deliver topically applied substances through the skin barrier. Based on findings that nanoparticles are highly suitable for penetrating the blood–brain barrier, their use for drug delivery through the skin has become a topic of intense research. In spite of the research efforts by academia and industry, a commercial product permitting the nanoparticle-assisted delivery of topically applied drugs has not yet been developed. However, nanoparticles of approximately 600 nm in diameter have been shown to penetrate efficiently into the hair follicles, where they can be stored for several days. The successful loading of nanoparticles with drugs and their triggered release inside the hair follicle may present an ideal method for localized drug delivery. Depending on the particle size, such a method would permit targeting specific structures in the hair follicles such as stem cells or immune cells or blood vessels found in the vicinity of the hair follicles.

Optical coherence tomography (OCT) provides significant advantages of high resolution (approaching the histopathology level) real-time imaging of tissues without use of contrast agents. Based on these advantages, the microstructural features of tumors can be visualized and detected intra-operatively: However, it is still not clinically accepted for tumor margin delineation due to poor specificity and accuracy. In contrast, Raman spectroscopy (RS) can obtain tissue information at the molecular level, but does not provide real-time imaging capability. Therefore, combining OCT and RS could provide synergy. To this end, we present a tissue analysis and classification method using both the slope of OCT intensity signal vs depth and the principle components from the RS spectrum as the indicators for tissue characterization. The goal of this study was to understand prediction accuracy of OCT and combined OCT/RS method for classification of optically similar tissues and organs. Our pilot experiments were performed on mouse kidneys, livers, and small intestines (SIs). The prediction accuracy with fivefold cross validation of the method has been evaluated by the support vector machine (SVM) method. The results demonstrate that tissue characterization based on the OCT/RS method was superior compared to using OCT structural information alone. This combined OCT/RS method is potentially useful as a noninvasive optical biopsy technique for rapid and automatic tissue characterization during surgery.

Purpose: To provide a geographical map of choroidal thickness (CT) around the macular region among subjects with low, moderate and high myopia. Methods: 20 myopic subjects (n = 40 eyes) without other identified pathologies participated in this study: 20 eyes of ≤ 3 diopters (D) (low myopic), 10 eyes between -3 and- 6D (moderate myopic), and 10 eyes of ≥6D (high myopic). The mean age of subjects was 30.2 years (±7.6 years; range, 24 to 46 years). A 1050 nm spectral-domain optical coherence tomography (SD-OCT) system, operating at 120 kHz imaging rate, was used in this study to simultaneously capture 3D anatomical images of the choroid and measure intraocular length (IOL) in the subject. The 3D OCT images of the choroid were segmented into superior, inferior, nasal and temporal quadrants, from which the CT was measured, representing radial distance between the outer retinal pigment epithelium (RPE) layer and inner scleral border. Measurements were made within concentric regions centered at fovea centralis, extended to 5mm away from fovea at 1mmintervals in the nasal and temporal directions. The measured IOL was the distance from the anterior cornea surface to the RPE in alignment along the optical axis of the eye. Statistical analysis was performed to evaluate CT at each geographic region and observe the relationship between CT and the degree of myopia. Results: For low myopic eyes, the IOL was measured at 24.619 ± 0.016 mm. The CT (273.85 ± 49.01 μm) was greatest under fovea as is in the case of healthy eyes. Peripheral to the fovea, the mean CT decreased rapidly along the nasal direction, reaching a minimum of 180.65 ± 58.25 μm at 5mm away from the fovea. There was less of a change in thickness from the fovea in the temporal direction reaching a minimum of 234.25 ± 42.27 μm. In contrast to the low myopic eyes, for moderate and high myopic eyes, CTs were thickest in temporal region (where CT = 194.94 ± 27.28 and 163 ± 34.89 μm, respectively). Like the low myopic eyes, moderate and high myopic eyes had thinnest CTs in the nasal region (where CT = 100.84 ± 16.75 and 86.64 ± 42.6 μm, respectively). High myopic eyes had the longest mean IOL （25.983 ± 0.021 mm), while the IOL of moderate myopia was 25.413 ± 0.022 mm (**p < 0:001). The CT reduction rate was calculated at 31.28 μm/D (diopter) from low to moderate myopia, whilst it is 13.49 μm/D from moderate to high myopia. The similar tendency was found for the IOL reduction rate in our study: 0.265mm/D from low to moderate myopia, and 0.137mm/D from moderate to high myopia. Conclusion: The CT decreases and the IOL increases gradually with the increase of myopic condition. The current results support the theory that choroidal abnormality may play an important role in the pathogenesis of myopic degeneration.

Photodynamic therapy (PDT) has been commonly used in treating many diseases, such as cancer and infectious diseases. We investigated the different effects of PDT on three main pathogenic bacteria of periodontitis — Prevotella melaninogenica (P.m.), Porphyromonas gingivalis (P.g.) and Aggregatibacter actinomycetemcomitans (A.a.). The portable red light-emitting diode (LED) phototherapy device was used to assess the exogenous PDT effects with different light doses and photosensitizer concentrations (Toluidine blue O, TBO). The portable blue LED phototherapy device was used to assess the endogenous PDT effects with the use of endogenous photosensitizers (porphyrin) under different light doses. We found out that both exogenous and endogenous PDT were able to restrict the growth of all the three bacteria significantly. Moreover, the optimal PDT conditions for these bacteria were obtained through this in vitro screening and could guide the clinical PDT on periodontitis.

Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for noninvasive and direct assessment of the viscoelastic properties of materials. Recent advances of background-free confocal Brillouin spectrometer allows investigators to acquire the Brillouin spectra for turbid samples as well as transparent ones. However, due to strong signal loss induced by the imperfect optical setup, the Brillouin photons are usually immersed in background noise. In this report, we proposed and experimentally demonstrated multiple approaches to enhance the signal collection efficiency. A signal enhancement by >4 times can be observed, enabling observation of ultra-weak signals.

Multivariate calibration is an important tool for spectroscopic measurement of analyte concentrations. We present a detailed study of a hybrid multivariate calibration technique, constrained regularization (CR), and demonstrate its utility in noninvasive glucose sensing using Raman spectroscopy. Similar to partial least squares (PLS) and principal component regression (PCR), CR builds an implicit model and requires knowledge only of the concentrations of the analyte of interest. Calibration is treated as an inverse problem in which an optimal balance between model complexity and noise rejection is achieved. Prior information is included in the form of a spectroscopic constraint that can be obtained conveniently. When used with an appropriate constraint, CR provides a better calibration model compared to PLS in both numerical and experimental studies.

The molar entropy (△S） and molar enthalpy (△H） for the denaturation event that triggers cutaneous erythema was determined to be △S = 190 J/(mole K) and △H = 146.9 × 10³ J/mole. The experiment involved placing heated water against the skin of the forearm, for a range of temperatures and exposure times. Exposing the skin to 45℃ for 22 s was at the threshold for producing erythema, which was similar to the threshold for a slight degree of pain.

A group of variously colored proteins belonging to the green fluorescent protein (GFP) family are responsible for coloring coral tissues. Corals of the Great Barrier Reef were studied with the custom-built fiber laser fluorescence spectrometers. Spectral analysis showed that most of the examined corals contained multiple fluorescent peaks ranging from 470 to 620 nm. This observation was attributed to the presence of multiple genes of GFP-like proteins in a single coral, as well as by the photo-induced post-translational modifications of certain GFP-like proteins. We isolated a novel photo-convertible fluorescent protein (FP) from one of the tested corals. We propose that two processes may explain the observed diversity of the fluorescent spectra in corals: (1) dark post-translational modification (maturation), and (2) color photo-conversion of certain maturated proteins in response to sunlight.

Solid phases of visible fluorescence substance (VFS) of biological fluids (blood, urine, hemodialysate) which was proposed earlier as a morbidity and mortality marker by renal failure and diabetes were investigated in-depth by the methods of electron and confocal microscopy, optical spectroscopy and matrix assisted laser desorption-ionization (MALDI) mass spectroscopy. It is shown that dry VFS exists predominantly in the form of carbon–oxygen–nitrogen (N ≈ 8.7 wt. %) nanoparticles (NPs) (5 ≤ d ≤ 100 nm). For the first time the existence of the threshold energy Eg ≈ 2.15 eV for excitation of VFS was observed experimentally and confirmed by semi-empirical calculations of the bathochromic shift. A good accordance with the earlier autonomous theoretical calculations was achieved. Thus, the long wavelength limit (575 nm) of the spectral range where the VFS can be used as a fluorescent marker was reliably determined. A pilot MALDI comparative study of graphene oxide (GO) and urine VFS was carried out. Six kinds of nitrogenfree particles (412 ≤ M ≤ 456 Da) were observed in each substance and possible computer models of those have been composed. It is established that along with nitrogen-containing advanced glycation end products (AGEs) also nitrogen-free carbon–oxygen–hydrogen particles (probably toxic) with the composition and structure related to GO can exist in biofluids. Both types of particles should be taken into account in search for the reasons of high mortality among end stage renal disease patients.

Laser ektacytometry is a technique widely used for measuring the deformability of red blood cells (erythrocytes) in blood samples in vitro. In ektacytometer, a flow of highly diluted suspension of erythrocytes in variable shear stress conditions is illuminated with a laser beam to obtain a diffraction pattern. The diffraction pattern provides information about the shapes (shear-induced elongations) of the cells under investigation. This paper is dedicated to developing the technique of laser ektacytometry so that it would enable one to measure the distribution of the erythrocytes in deformability. We discuss the problem of calibration of laser ektacytometer and test a novel data processing algorithm allowing to determine the parameters of the distribution of erythrocytes deformability. Experimentally, we examined 12 specimens of blood of rats under the action of 4 shear stresses. Analysis of the data shows that in conditions of a limited range of digitizing the diffraction patterns, the measurement errors for the mean deformability, deformability scatter and the skewness of erythrocytes distribution in deformability by our method are respectively 15%, 20% and 20%.

The ideal treatment modality for metastatic cancer would be a local treatment that can destroy primary tumors while inducing an effective systemic anti-tumor response. To this end, we developed laser immunotherapy, combining photothermal laser application with an immunoadjuvant for the treatment of metastatic cancer. Additionally, to enhance the selective photothermal effect, we integrated light-absorbing nanomaterials into this innovative treatment. Specifically, we developed an immunologically modified carbon nanotube combining single-walled carbon nanotubes (SWNTs) with the immunoadjuvant glycated chitosan (GC). To determine the effectiveness of laser irradiation, a series of experiments were performed using two different irradiation durations — 5 and 10 min. Rats were inoculated with DMBA-4 cancer cells, a metastatic cancer cell line. The treatment group of rats receiving laser irradiation for 10 min had a 50% longterm survival rate without residual primary or metastatic tumors. The treatment group of rats receiving laser irradiation for 5 min had no long-term survivors; all rats died with multiple metastases at several distant sites. Therefore, LasertSWNT–GC treatment with 10 min of laser irradiation proved to be effective at reducing tumor size and inducing long-term anti-tumor immunity.