Penetration Depth Of Light Research Articles

Decoupling the Surface and Bulk Reactivities of MXenes and Catalytic Activity Tuning through Surface Chemistry Modification

MXenes, a family of two-dimensional (2D) materials based on transition metal carbides and nitrides, show great promise as electrocatalysts for electrochemical reactions but suffer from a lack of fundamental understanding of their electrocatalytic mechanisms. Decoupling the surface and bulk reactivities are key to understanding the electrocatalytic mechanisms of these emerging nanomaterials. Herein, we use Raman spectroscopy to decouple the surface and bulk reactivities of the Ti2NTx MXene. By attenuating the Raman intensity, we were able to control the penetration depth of the incident light. We show that with 5–10% laser power, we can restrict the access to the surface of the Ti2NTx MXene, which shows predominantly the oxide phase from the passivation layer. With 50–100% laser power, we can penetrate the bulk of the MXene material, as evidenced by the Ti–N bond network characteristics. By using this approach, we can study and understand the surface reactivity of MXenes, which has not been understood. To expand these findings to electrochemical reactions, we have analyzed the surface reactivities of the pristine and NaOH treated Ti2NTx MXenes using Raman spectroscopy and hydrogen evolution reaction (HER). The surface chemistry of the NaOH treated Ti2NTx MXene was different from that of the pristine ones and showed predominantly −OH termination groups and no −F. This resulted in an excellent HER activity of ∼100 mV overpotential at 10 mA cm–2 and an impressive Tafel slope of 98 mV dec–1. These results are comparable to those for the benchmark Pt/C in the alkaline electrolyte. To summarize, we propose an approach for decoupling the surface and bulk reactivities of MXenes and a simple method to tune their HER activity to match those for noble metals. This approach can be applied to other materials and systems to accelerate the discovery of electrocatalysts and electrode materials.

Realistic deformable phantoms with optical properties of biological tissues for biomedical research applications

A matrix of poly (vinyl alcohol) (PVA) slime phantoms was investigated to replicate the published optical properties of the lung carcinoma and tumorous brain tissues at 630 nm wavelength. The effective attenuation coefficients (µeff) and penetration depths of light in the tissue phantoms were deduced from measurements of its optical properties and the anisotropy factor (g), obtained using the Henyey-Greenstein (H-G) phase function and Wolfram Mathematica. The mechanical response of the fabricated phantom materials was characterized and found to be flexible and mouldable into shapes and sizes comparable to desired tissue types.In the context of accuracy and stability, the phantoms were monitored for over two months and managed to preserve their optical properties with inconsiderable changes, possibly due to dehydration. Further data analysis is required to clarify if the optical properties would significantly change for long periods. We conclude that the fabrication of deformable tissue phantoms capable of uniformly incorporating any inserted lesion-like objects with relatively available materials and clear procedure is realizable. These phantoms are promising for testing and calibrating new optical imaging systems and developing disease diagnosis and treatment techniques.

A multifunctional nanoplatform based on Fe3O4@Au NCs with magnetic targeting ability for single NIR light-triggered PTT/PDT synergistic therapy of cancer

Although simultaneous photothermal therapy (PTT) and photodynamic therapy (PDT) have been proven to be beneficial for cancer treatment, high-power laser light sources, shallow penetration depth of light and especially activation by two different light sources make it difficult to be popularized in clinical cancer therapy. Herein, the novel multifunctional Fe3O4@Au nanocomposites (NCs) have been designed and synthesized, which simultaneously act as photothermal conversion agents (PCAs) and photosensitizers (PSs) for PTT/PDT synergistic therapy of human cervical cancer (HeLa) cells using a single excitation light source. Under low-power 808 nm laser irradiation, photothermal conversion efficiency (PCE) of Fe3O4@Au NCs was as high as 39.22% and the cytotoxic singlet oxygen (1O2) could be simultaneously generated. In addition, Fe3O4@Au NCs showed relatively good biocompatibility and low cytotoxicity, which were ideal alternatives for nanotherapeutic agents for treatment of HeLa cells. Meanwhile, PTT only and PTT/PDT dual-modal therapeutic effects of Fe3O4@Au NCs on HeLa cells were compared. The experimental results confirmed that the near-infrared (NIR)-triggered PDT/PTT synergistic therapy of HeLa cells was more efficient due to the synergistic effect. Interestingly, Fe3O4@Au NCs with saturation magnetization (Ms) value of 66.5 emu/g possessed good magnetic responsivity, which could be collected easily with a magnet. The magnetic targeting of Fe3O4@Au NCs could effectively promote their accumulation at tumor sites, thus further enhancing the efficacy of PTT/PDT synergistic therapy of HeLa cells. This study provides a feasible paradigm for magnetic targeting-assisted PTT/PDT synergistic therapy of cancer cells under a single-wavelength excitation and opens up a novel direction for clinical cancer therapy.

Biochars from Olive Stones as Carbonaceous Support in Pt/TiO2-Carbon Photocatalysts and Application in Hydrogen Production from Aqueous Glycerol Photoreforming.

Several biochars were synthesized from olive stones and used as supports for TiO2, as an active semiconductor, and Pt as a co-catalyst (Pt/TiO2-PyCF and Pt/TiO2-AC). A third carbon-supported photocatalyst was prepared from commercial mesoporous carbon (Pt/TiO2-MCF). Moreover, a Pt/TiO2 solid based on Evonik P25 was used as a reference. The biochars used as supports transferred, to a large extent, their physical and chemical properties to the final photocatalysts. The synthesized catalysts were tested for hydrogen production from aqueous glycerol photoreforming. The results indicated that a mesoporous nature and small particle size of the photocatalyst lead to better H2 production. The analysis of the operational reaction conditions revealed that the H2 evolution rate was not proportional to the mass of the photocatalyst used, since, at high photocatalyst loading, the hydrogen production decreased because of the light scattering and reflection phenomena that caused a reduction in the light penetration depth. When expressed per gram of TiO2, the activity of Pt/TiO2-PyCF is almost 4-times higher than that of Pt/TiO2 (1079 and 273 mmol H2/gTiO2, respectively), which points to the positive effect of an adequate dispersion of a TiO2 phase on a carbonaceous support, forming a highly dispersed and homogeneously distributed titanium dioxide phase. Throughout a 12 h reaction period, the H2 production rate progressively decreases, while the CO2 production rate increases continuously. This behavior is compatible with an initial period when glycerol dehydrogenation to glyceraldehyde and/or dihydroxyacetone and hydrogen predominates, followed by a period in which comparatively slower C-C cleavage reactions begin to occur, thus generating both H2 and CO2.

Analysis of Light Penetration Depth in Apple Tissues by Depth-Resolved Spatial-Frequency Domain Imaging.

Spatial-frequency domain imaging (SFDI) has been developed as an emerging modality for detecting early-stage bruises of fruits, such as apples, due to its unique advantage of a depth-resolved imaging feature. This paper presents theoretical and experimental analyses to determine the light penetration depth in apple tissues under spatially modulated illumination. Simulation and practical experiments were then carried out to explore the maximum light penetration depths in 'Golden Delicious' apples. Then, apple experiments for early-stage bruise detection using the estimated reduced scattering coefficient mapping were conducted to validate the results of light penetration depths. The results showed that the simulations produced comparable or a little larger light penetration depth in apple tissues (~2.2 mm) than the practical experiment (~1.8 mm or ~2.3 mm). Apple peel further decreased the light penetration depth due to the high absorption properties of pigment contents. Apple bruises located beneath the surface peel with the depth of about 0-1.2 mm could be effectively detected by the SFDI technique. This study, to our knowledge, made the first effort to investigate the light penetration depth in apple tissues by SFDI, which would provide useful information for enhanced detection of early-stage apple bruising by selecting the appropriate spatial frequency.

Photothermal‐Responsive Crosslinked Liquid Crystal Polymers

AbstractCrosslinked liquid crystal polymers (CLCPs) are a promising type of smart polymer material with excellent two‐way shape memory behavior under the stimulation of various external conditions. Among the various external stimuli, light with the advantages of instantaneity, high accuracy, remote controllability, pollution‐free, etc., has been widely used in the control of CLCPs. Traditional photoresponsive CLCP systems based on photoisomerization are limited by the penetration depth of ultraviolet light, the number of useful photochemical reactions, and long‐term stability. Recently, a strategy for designing photoresponsive CLCPs based on the photothermal effect has attracted scientific attention. Photothermal materials in the CLCP matrix can convert light into heat through plasma resonance or energy transition under the light irradiation of a certain wavelength, and locally heat the CLCP matrix to beyond the liquid crystal‐to‐isotropic phase transition temperature, thus achieving reversible macroscopic deformation. Combining photothermal materials and CLCPs can decrease the dependence on specific photosensitive groups such as azobenzene mesogens and endow photoresponsive CLCPs with design flexibility. Herein, the photothermal‐responsive CLCPs under the stimulations of different light wavelengths and their application fields are reviewed. In addition, the current challenges in the field of photothermal‐responsive CLCPs are summarized, and a brief outlook on future development is proposed.

Melanin Stacking Differences in Pigmented and Non-Pigmented Melanomas: Quantitative Differentiation between Pigmented and Non-Pigmented Melanomas Based on Light-Scattering Properties.

Cutaneous melanoma is a cancer with metastatic potential characterized by varying amounts of pigment-producing melanocytes, and it is one of the most aggressive and fatal forms of skin malignancy, with several hundreds of thousands of cases each year. Early detection and therapy can lead to decreased morbidity and decreased cost of therapy. In the clinic, this often translates to annual skin screenings, especially for high-risk patients, and generous use of the ABCDE (asymmetry, border irregularity, color, diameter, evolving) criteria. We have used a new technique termed vibrational optical coherence tomography (VOCT) to non-invasively differentiate between pigmented and non-pigmented melanomas in a pilot study. The VOCT results reported in this study indicate that both pigmented and non-pigmented melanomas have similar characteristics, including new 80, 130, and 250 Hz peaks. Pigmented melanomas have larger 80 Hz peaks and smaller 250 Hz peaks than non-pigmented cancers. The 80 and 250 Hz peaks can be used to quantitative characterize differences between different melanomas. In addition, infrared light penetration depths indicated that melanin in pigmented melanomas has higher packing densities than in non-pigmented lesions. Using machine learning techniques, the sensitivity and specificity of differentiating skin cancers from normal skin are shown to range from about 78% to over 90% in this pilot study. It is proposed that using AI on both lesion histopathology and mechanovibrational peak heights may provide even higher specificity and sensitivity for differentiating the metastatic potential of different melanocytic lesions.

3D quantitative assessment for nuclear morphology in osteocytic spheroid with optical clearing technique.

In recent years, three-dimensional (3D) cell culture has been attracting attention as a cell culture model that mimics an environment closer to that of a living organism. It is known that there is a close relationship between cell nuclear shape and cellular function, which highlights the importance of cell nucleus shape analysis in the 3D culture. On the other hand, it is difficult to observe the cell nuclei inside the 3D culture models because the penetration depth of the laser light under a microscope is limited. In this study, we adopted an aqueous iodixanol solution to the 3D osteocytic spheroids derived from mouse osteoblast precursor cells to make the spheroids transparent for 3D quantitative analysis. With a custom-made image analysis pipeline in Python, we found that the aspect ratio of the cell nuclei near the surface of the spheroid was significantly greater than that at the center, suggesting that the nuclei on the surface were deformed more than those at the center. The results also quantitatively showed that the orientation of nuclei in the center of the spheroid was randomly distributed, whereas those on the surface of the spheroid were oriented parallel to the surface of the spheroid. Our 3D quantitative method with an optical clearing technique will contribute to the 3D culture models including various organoid models to elucidate the nuclear deformation during the development of the organs. Insight box Although 3D cell culture has been a powerful tool in the fields of fundamental biology and tissue engineering, it raises the demand for quantification techniques for cell nuclear morphology in the 3D culture model. In this study, we attempted to optically clear a 3D osteocytic spheroid model using iodixanol solution for the nuclear observation inside the spheroid. Moreover, using a custom-made image analysis pipeline in Python, we successfully quantified the nuclear morphology regarding aspect ratio and orientation. Our quantitative method with the optical clearing technique will contribute to the 3D culture models such as various organoid models to elucidate the nuclear deformation during the development of the organs.

The Regioselective Solid-State Photo-Mechanochemical Synthesis of Nanographenes with UV light.

Photochemical reactors inherently suffer from the low penetration depth of light and therefore rely on high dilutions to enable chemical reactions. Here we present the first method of UV (ultraviolet) photochemistry in the complete absence of bulk solvents in a ball mill. Triphenylene was synthesized by two routes, the Mallory reaction and the cyclodehydrochlorination (CDHC), resulting in yields of 81 and 92 %, respectively. The reaction was successfully scaled up to the gram scale and the robustness of the method was demonstrated for several different substrates. Finally, the regioselective assembly of nanographenes by mechanochemistry was demonstrated for larger systems. Thus, the mechanochemical approach presented here provides a powerful new tool for the atomically precise construction of nanographenes.

Optical coherence tomography application for assessing variation in bone mineral content: a preclinical study.

Optical Coherence Tomography (OCT) is a non-invasive imaging technique that produces cross-sectional images through biological tissues, allowing three-dimensional reconstruction and analysis. Aim was to evaluate if OCT may discriminate among tissues with different bone density and composition, by measuring the depth of light penetration in porcine and rat bone samples. Two carpal bone samples (2 cm length) were harvested from the porcine forelimb and fixed overnight in 3.7% buffered formal saline. Following fixation, one sample was decalcified in a 1:1 mixture of 8% hydrochloric acid and 8% formic acid solution for three days, with solution changes each day. Samples were imaged using an OCT microscope. Furthermore, the calvaria, ulnar, alveolar and basal bone of the mandible of 6 male and 6 female rats were cleared of overlying soft tissues and scanned under OCT. The light penetration depth in each sample was measured using the software Image J, and Scattering Attenuation Microscopy. In the mineralized bone the average depth (µm) and standard deviation (SD) of light penetration were 790.1±18.05 and 410.4±21.7 for periosteal and endosteal surface, respectively, and 507.3±21.03 for cross-section surfaces, while it was 858.4±32.03 for periosteal surface, 1150±26.9 for endosteal, and 627.3±31.8 for cross-section bone surfaces in demineralized porcine bone. There was a significant difference (p<0.001) in depth of light penetration between normal and de-mineralized bone for all regions evaluated. No systematic significant difference in light penetration depth between-gender was found at any site evaluated, while there were variations between sites (p<0.001). The OCT detected differences in bone mineral and porosity among gender (p<0.0001) CONCLUSIONS: This study suggests that OCT may represent a valuable technique to estimate local variations in bone mineral content.

Verhoeff van Gieson staining in laser-irradiated gingival tissues

ABSTRACT There have been several studies on the use of the Verhoeff van Gieson staining method to demonstrate thermal effects on tissues. However, this method has rarely been used for the analysis of periodontal tissues. This study was undertaken to compare the quality and effectiveness of the Verhoeff van Gieson (VVG) staining method with conventional hematoxylin & eosin (H&E) in measuring the thermal effects in gingival tissues. Periodontal tissues around bovine mandibular teeth were treated using different surgical lasers (wavelengths of 10,600 nm, 970 nm, and 445 nm) at 2 W power setting. Measurements of the depth of the coagulation zone were recorded for all treatment groups in sample tissues stained with H&E as well as the VVG-staining method. Measures were interpreted by a trained pathologist. A statistical analysis was performed using the Wilcoxon signed-rank test to determine if there was a statistically significant difference between values recorded for the light penetration depth on tissues stained with each of the two staining methods. It was determined that there was no significant difference in the recorded values (P = 0.23). We have concluded that the VVG-stained tissues were better able to visualize the depth of thermal damage and thus may make it easier for someone not well trained to interpret the depth of light penetration in these tissues.

Specific and Long-Term Luminescent Monitoring of Hydrogen Peroxide in Tumor Metastasis.

Luminescent monitoring of endogenous hydrogen peroxide (H2 O2 ) in tumors is conducive to understanding metastasis and developing novel therapeutics. The clinical transformation is obstructed by the limited light penetration depth, toxicity of nano-probes, and lack of long-term monitoring modes of up to days or months. New monitoring modes are introduced via specific probes and implantable devices, which can achieve real-time monitoring with a readout frequency of 0.01 s or long-term monitoring for months to years. Near-infrared dye-sensitized upconversion nanoparticles (UCNPs) are fabricated as the luminescent probes, and the specificity to reactive oxygen species is subtly regulated by the self-assembled monolayers on the surfaces of UCNPs. Combined with the passive implanted system, a 20-day monitoring of H2 O2 in the rat model of ovarian cancer with peritoneal metastasis is achieved, in which the limited light penetration depth and toxicity of nano-probes are circumvented. The developed monitoring modes show great potential in accelerating the clinical transformation of nano-probes and biochemical detection methods.

Mismatch between Bioluminescence Imaging (BLI) and MRI When Evaluating Glioblastoma Growth: Lessons from a Study Where BLI Suggested "Regression" while MRI Showed "Progression".

Orthotopic glioblastoma xenografts are paramount for evaluating the effect of innovative anti-cancer treatments. In longitudinal studies, tumor growth (or regression) of glioblastoma can only be monitored by noninvasive imaging. For this purpose, bioluminescence imaging (BLI) has gained popularity because of its low cost and easy access. In the context of the development of new nanomedicines for treating glioblastoma, we were using luciferase-expressing GL261 cell lines. Incidentally, using BLI in a specific GL261 glioblastoma model with cells expressing both luciferase and the green fluorescent protein (GL261-luc-GFP), we observed an apparent spontaneous regression. By contrast, the magnetic resonance imaging (MRI) analysis revealed that the tumors were actually growing over time. For other models (GL261 expressing only luciferase and U87 expressing both luciferase and GFP), data from BLI and MRI correlated well. We found that the divergence in results coming from different imaging modalities was not due to the tumor localization nor the penetration depth of light but was rather linked to the instability in luciferase expression in the viral construct used for the GL261-luc-GFP model. In conclusion, the use of multi-modality imaging prevents possible errors in tumor growth evaluation, and checking the stability of luciferase expression is mandatory when using BLI as the sole imaging modality.

Light Conversion Nanomaterials for Wireless Phototherapy.

ConspectusPhototherapy including optogenetics, photodynamic therapy (PDT), photothermal therapy (PTT), and photoimmunotherapy (PIT) has been proven to be effective against different diseases. However, as the name suggests, phototherapy requires light irradiation, thus its therapeutic efficiency is often restricted by limited depth of light penetration within biological tissue. This light penetration limitation is significantly adverse to PDT and optogenetics because both therapies are usually activated with UV and visible light of very poor tissue penetration efficiency. Current light delivery methods usually involve cumbersome setups and require optical fiber or catheter insertion, which not only restrict the movement of patients but also impose incompatibility issues with chronic implantation. To address the existing challenges, wireless phototherapy was developed through various approaches over recent years, which usually relies on implantable wireless electronic devices. However, the application of wireless electronic devices is limited by invasion during implantation, unwanted heat generation, and adverse immunogenicity of these devices.Over the recent years, applying light conversion nanomaterials as light transducers for wireless phototherapy has garnered much interest. Compared with implantable electronic devices and optical fiber, nanomaterials can be easily injected into the body with minimal invasiveness and can also be surface functionalized to increase their biocompatibility and cell accumulation efficiency. Commonly applied light conversion nanomaterials include upconversion nanoparticles (UCNPs), X-ray nanoscintillators, and persistent luminescence nanoparticles (PLNPs). UCNPs and X-ray nanoscintillators can respectively convert near-infrared (NIR) light and X-ray, which have good tissue penetration efficiency, to UV or visible light, which is suitable for activating phototherapy. PLNPs can be excited by external light such as X-rays and NIR light and retain long afterglow luminescence after the removal of the excitation light source. As a result, applying PLNPs in phototherapy can potentially reduce irradiation time from external light sources, thus minimizing tissue photodamage. This Account aims to briefly discuss (i) the mechanisms of different phototherapies, (ii) the development and mechanisms of light conversion nanomaterials, (iii) the application of light conversion nanomaterials in wireless phototherapy, highlighting how they relieve current challenges in phototherapy, and (iv) perspectives for future development of light conversion nanomaterials for wireless phototherapy.

TiO2–SiO2 Self-Standing Materials bearing Hierarchical Porosity: MUB-200(x) Series toward 3D-Efficient VOC Photoabatement Properties

Three-dimensional photoactive self-standing porous materials have been synthesized through the integration of soft chemistry and colloids (emulsions, lyotrope mesophases, and P25 titania nanoparticles). Final multiscale porous ceramics bear 700-1000 m2 g-1 of micromesoporosity depending on the P25 nanoparticle contents. The applied thermal treatment does not affect the P25 anatase/rutile allotropic phase ratio. Photonic investigations correlated with the foams' morphologies suggest that the larger amount of TiO2 that is introduced, the larger the walls' density and the smaller the mean size of the void macroscopic diameters, with both effects inducing a reduction of the photon transport mean free path (lt) with the P25 content increase. A light penetration depth in the range of 6 mm is reached, thus depicting real 3D photonic scavenger behavior. The 3D photocatalytic properties of the MUB-200(x) series, studied in a dynamic "flow-through" configuration, show that the highest photoactivity (concentration of acetone ablated and concentration of CO2 formed) is obtained with the highest monolith height (volume) while providing an average of 75% mineralization. These experimental results validate the fact that these materials, bearing 3D photoactivity, are paving the path for air purification operating with self-standing porous monolith-type materials, which are much easier to handle than powders. As such, the photocatalytic systems can now be advantageously miniaturized, thereby offering indoor air treatment within vehicles/homes while drastically limiting the associated encumbrance. This volumetric counterintuitive acting mode for light-induced reactions may find other relevant advanced applications for photoinduced water splitting, solar fuel, and dye-sensitized solar cells while both optimizing photon scavenging and opening the path for the miniaturization of the processes where encumbrance or a foot-print penalty would be advantageously circumvented.

Oxygen-vacancy-rich molybdenum carbide MXene nanonetworks for ultrasound-triggered and capturing-enhanced sonocatalytic bacteria eradication

Incurable bacterial infection and intractable multidrug resistance remain critical challenges in public health. A prevalent approach against bacterial infection is phototherapy including photothermal and photodynamic therapy, which is unfortunately limited by low penetration depth of light accompanied with inevitable hyperthermia and phototoxicity damaging healthy tissues. Thus, eco-friendly strategy with biocompatibility and high antimicrobial efficacy against bacteria is urgently desired. Herein, we propose and develop an oxygen-vacancy-rich MoOxin situ on fluorine-free Mo2C MXene with unique neural-network-like structure, namely MoOx@Mo2C nanonetworks, in which their desirable antibacterial effectiveness originates from bacteria-capturing ability and robust reactive oxygen species (ROS) generation under precise ultrasound (US) irradiation. The high-performance, broad-spectrum microbicidal activity of MoOx@Mo2C nanonetworks without damaging normal tissues is validated based on systematic in vitro and in vivo assessments. Additionally, RNA sequencing analysis illuminates that the underlying bactericidal mechanism is attributed to the chaotic homeostasis and disruptive peptide metabolisms on bacteria instigated by MoOx@Mo2C nanonetworks under US stimulation. Considering antibacterial efficiency and a high degree of biosafety, we envision that the MoOx@Mo2C nanonetworks can serve as a distinct antimicrobial nanosystem to fight against diverse pathogenic bacteria, especially eradicating multidrug-resistant bacteria-induced deep tissue infection.

Quantitative Comparison of Analytical Solution and Finite Element Method for Investigation of Near-infrared Light Propagation in Brain Tissue Model.

Functional near-infrared spectroscopy (fNIRS) is an imaging method in which a light source and detector are installed on the head; consequently, the re-emission of light from human skin contains information about cerebral hemodynamic alteration. The spatial probability distribution profile of photons penetrating tissue at a source spot, scattering into the tissue, and being released at an appropriate detector position, represents the spatial sensitivity. Modeling light propagation in a human head is essential for quantitative near-infrared spectroscopy and optical imaging. The specific form of the distribution of light is obtained using the theory of perturbation. An analytical solution of the perturbative diffusion equation (DE) and finite element method (FEM) in a Slab media (similar to the human head) makes it possible to study light propagation due to absorption and scattering of brain tissue. The simulation result indicates that sensitivity is slowly decreasing in the deep area, and the sensitivity below the source and detector is the highest. The depth sensitivity and computation time of both analytical and FEM methods are compared. The simulation time of the analytical approach is four times larger than the FEM. In this paper, an analytical solution and the performance of FEM methods when applied to the diffusion equation for heterogeneous media with a single spherical defect are compared. The depth sensitivity along with the computation time of simulation has been investigated for both methods. For simple and Slab modes of the human brain, the analytical solution is the right candidate. Whenever the brain model is sophisticated, it is possible to use FEM methods, but it costs a higher computation time. Analytical and finite element method (FEM) depth sensitivity are almost the same.FEM requires more computation time, but can handle complicated head models.The analytical method is proposed for the first step and simple head models. The functional near-infrared spectroscopy (fNIRS) is a type of neuromonitoring that uses near-infrared light to measure brain activity indirectly and is similar to electroencephalography (EEG). A single-channel fNIRS system contains a near-infrared light source, which emits near-infrared light (NIR), and a detector is placed near the source. A light intensity change received by detectors indicates brain activity when NIR light penetrates into the gray matter. It is necessary to have a prior understanding of light penetration depth in order to measure brain activity more accurately. fNIRS can be better understood, optimized, and investigated through modeling light propagation in brain tissue. In order to study light in tissues, analytical and numerical methods can be used. In this work, we compared these two approaches quantitatively in a simple slab medium. We concluded that the numerical method takes too much time to calculate the results, but it can be applied to complicated head models. The results of these studies provide researchers with new insights into the modeling and simulation of fNIRS and diffuse optical tomography.

Electric field effect on the light penetration depth and switching times in liquid crystal cells with nonuniform director orientation

Electric field effect on the light penetration depth and switching times in liquid crystal cells with nonuniform director orientation

Engineering nanofusiform Iron-doped polydiaminopyridine boost intratumoral penetration for immunogenic cell Death-mediated synergistic Photothermal/Chemo therapy

Photothermal therapy (PTT) featured the advantages of convenient operation, high selectivity and little side effects has been as a non-invasive and promising treatment that converts near infrared light into heat energy through photothermal agents, which however is also trouble with limited penetration depth of near-infrared light, low treatment efficiency and et.al. Considering this situation, we synthesized iron-doped poly (2, 6-diaminopyridine) nanoparticles (FDAP NPs) with fusiform morphology by one-step oxidative polymerization of Fe3+. To improve therapeutic outcome, the chemotherapeutic drug doxorubicin (DOX) was further decorated on the fusiform surface by hydrophobic interaction to get the expectant FDAP@DOX nanosystem. The collaborative design endowed FDAP@DOX with good photothermal conversion rate, which could convert light energy into heat energy under the irradiation of 808 nm wavelength laser, and then further increased the temperature of the tumor site and leaded to strong immunogenic cell death (ICD) and tumor cell apoptosis. Meanwhile, the increase of temperature also promoted the release of superficial DOX, realizing the synergistic therapeutic modalities of photothermal/chemo therapy and making the tumor weight losing more thorough in 4T1 breast tumor animal model. Thus, this study shows a facile but effective idea for the construction of multimodal therapy-based integrated nanomedicine, and offers a service for the field of photothermal/chemo tumor therapy.

AIEgens/Mitochondria Nanohybrids as Bioactive Microwave Sensitizers for Non-Thermal Microwave Cancer Therapy.

Aggregation-induced emission luminogens (AIEgens) are widely used as photosensitizers for image-guided photodynamic therapy (PDT). Due to the limited penetration depth of light in biological tissues, the treatments of deep-seated tumors by visible-light-sensitized aggregation-induced emission(AIE) photosensitizers are severely hampered. Microwave dynamic therapy attracts much attention because microwave irradiation can penetrate very deep tissues and sensitize the photosensitizers to generate reactive oxygen species (ROS). In this work, a mitochondrial-targeting AIEgen (DCPy) is integrated with living mitochondria to form a bioactive AIE nanohybrid. This nanohybrid can not only generate ROS under microwave irradiation to induce apoptosis of deep-seated cancer cells but also reprogram the metabolism pathway of cancer cells through retrieving oxidative phosphorylation (OXPHOS) instead of glycolysis to enhance the efficiency of microwave dynamic therapy. This work demonstrates an effective strategy to integrate synthetic AIEgens and natural living organelles, which would inspire more researchers to develop advanced bioactive nanohybrids for cancer synergistic therapy.