532-nm Excitation Research Articles

Uncovering upconversion photoluminescence in layered PbI2 above room temperature.

As a van der Waals (vdW) layered semiconductor material, lead iodide (PbI2) possessing a direct bandgap with strong photoluminescence emission in visible range has gained wide attention in applications of photonic and optoelectronic devices. Here, upconversion photoluminescence (UPL) in exfoliated PbI2 flakes is demonstrated at room temperature and elevated temperatures. The linear power dependence of UPL emission with 532nm excitation suggests the one-photon involved multiphonon-assisted UPL emission process, which is revealed by the temperature-dependent UPL emission measurement. Meanwhile, the nonlinear power dependence of UPL emission with 561nm excitation indicates the transition of UPL emission mechanism from linear to nonlinear regime, and the temperature-dependent UPL emission study further shows that the upconversion is contributed by both the multiphonon-assisted UPL process and the two-photon absorption induced PL process. This study will provide an insight to the understanding of photon upconversion in vdW layered semiconductors and advancing applications in temperature-controlled photon upconversion, tunable photonics, photodetection and imaging.

All-fiber miniature non-contact photoacoustic probe based on photoacoustic remote sensing microscopy for vascular imaging in vivo.

Photoacoustic (PA) remote sensing (PARS) microscopy represents a significant advancement by eliminating the need for traditional acoustic coupling media in PA microscopy (PAM), thereby broadening its potential applications. However, current PARS microscopy setups predominantly rely on free-space optical components, which can be cumbersome to implement and limit the scope of imaging applications. In this study, we develop an all-fiber miniature non-contact PA probe based on PARS microscopy, utilizing a 532-nm excitation wavelength, and showcase its effectiveness in in vivo vascular imaging. Our approach integrates various fiber-optic components, including a wavelength division multiplexer, a mode field adaptor, a fiber lens, and an optical circulator, to streamline the implementation of the PARS microscopy system. Additionally, we have successfully developed a miniature PA probe with a diameter of 4 mm. The efficacy of our imaging setup is demonstrated through in vivo imaging of mouse brain vessels. By introducing this all-fiber miniature PA probe, our work may open up new opportunities for non-contact PAM applications.

Insights into the Synaptic Properties of Dopamine Release Revealed by Single Walled Carbon Nanotube Biosensors

It is thought that there are two distinct modes of chemical neurotransmission, referred to as fast (synaptic) transmission and slow (volume) transmission. Fast transmission, mediated by ligand-gated ionotropic receptors, operate with millisecond temporal and nanometer spatial precision in excitatory and inhibitory synapses, primarily mediated by glutamate and GABA, respectively. In contrast, slow transmission relies on activation of G-protein coupled receptors (GPCRs) and is mediated by several classes of neuromodulators, including dopamine. Neuromodulators are thought to operate at temporal scales that range from hundreds of milliseconds to minutes, with a spatial specificity that is insufficiently understood but generally described as “diffuse”. In this work, we provide new evidence that shows the spatial precision of dopamine transmission is highly reminiscent of the spatial properties of signaling mediated by the fast acting neurotransmitters.To gain this insight, we used an optical assay named “DopaFilm” that is based on oligonucleotide functionalized single walled carbon nanotube dopamine sensors (nanosensors). Primary dopaminergic neurons were grown on top of glass coverslips functionalized with nanosensors, which enabled visualization of dopamine exocytosis events in single release sites under a continuous 785nm excitation laser. In axonal arbors, DopaFilm can report evoked and spontaneous dopamine release events with high signal to noise ratios of up to 50. Recording on DopaFilm revealed dopamine release is fast, calcium-dependent, and reliant on similar presynaptic protein machinery employed by fast neurotransmitters. These findings challenge the notion that dopamine is a slow transmitter; however it doesn’t preclude the possibility of imprecise spatial signaling, consistent with volume transmission theory. More recent data from our lab now challenges the spatial characteristics of volume transmission model as currently understood in the literature. In this talk, I will discuss new insights gained on dopamine signaling including clear examples of precise spatial arrangements of dopamine release sites, and ultrastructural, biochemical and spatial transcriptomic data that shows that neuromodulatory action can be highly spatially precise in nature.

An electrochemical/SERS dual-mode immunosensor using TMB/Au nanotag and Au@2D-MoS2 modified screen-printed electrode for sensitive detection of prostate cancer biomarker

This study describes a novel dual-mode immunosensor that combines electrochemical (EC) and surface-enhanced Raman scattering (SERS) techniques for the detection of prostate-specific antigen (PSA), a biomarker associated with prostate cancer. The sensor consists of a nanocomposite of gold nanoparticles (AuNPs) deposited on two-dimensional (2D) molybdenum disulfide (Au@MoS2) modified on a working carbon electrode of a screen-printed electrode (SPE). Subsequently, the primary antibody (Ab1) is immobilized on the modified electrode, creating Ab1/Au@MoS2/SPE for specific recognition of the target PSA. In parallel, AuNPs are conjugated with a secondary antibody (Ab2) and a probe molecule, 3,3′,5,5′-tetramethylbenzidine (TMB), leading nanotags (TMB/Ab2/AuNPs) formation exhibiting strong SERS and EC responses. Upon the presence of the target, sandwich immunocomplexes can be formed through antigen-antibody interactions (Ab1-PSA-Ab2). The differential pulse voltammetry (DPV) technique is employed for EC detection mode, while a handheld Raman spectrometer with a 785 nm excitation laser is utilized to collect SERS signals. The developed system demonstrates excellent selectivity and sensitivity, with low limits of detection (LODs) of 3.58 pg mL−1 and 4.83 pg mL−1 for EC and SERS sensing, respectively. Importantly, the dual-mode immunosensor proves effective quantifying PSA protein in human serum samples with good recovery. Given its high sensitivity and proficiency in analyzing biological samples, this proposed immunosensor holds promise as an alternative tool for the early diagnosis of cancers.

Chick sexing based on the blood analysis using Raman spectroscopy

Efforts are underway to develop technology for automatically determining the sex of chick embryos, aimed at establishing a stable and efficient poultry farming system while also addressing animal welfare concerns. This study investigated the possibility of chick sexing through blood analysis using Raman spectroscopy. Raman spectra were obtained from whole blood and its constituents, such as red blood cells (RBCs) and blood plasma, collected from chicks aged 1–2 days, using a 785-nm excitation wavelength. Principal component analysis (PCA) revealed statistically significant sex-dependent spectral variations in whole blood and RBCs, whereas blood plasma showed less clear dependency. These spectral differences between male and female chicks were attributed to differences in the proportion of spectral components from oxygenated (oxy-) and deoxygenated (deoxy-) RBCs, with males exhibiting a slightly stronger contribution of oxy-RBCs compared to females. This reflects the higher oxygen affinity of hemoglobin (Hb) in males compared to females. A model for discriminating chick sex was built using the ratios of certain Raman band characteristics of oxy-RBCs and deoxy-RBCs, achieving a sensitivity of 100%. This spectroscopic method holds promise for developing technology to discriminate the sex of early chicken embryos in ovo by detecting differences in oxygen saturation of RBCs based on sex.

Molecular Vibrations in Chiral Europium Complexes Revealed by Near-Infrared Raman Optical Activity.

Raman optical activity (ROA) is commonly measured with green light (532nm) excitation. At this wavelength, however, Raman scattering of europium complexes is masked by circularly polarized luminescence (CPL). This can be avoided using near-infrared (near-IR, 785nm) laser excitation, as demonstrated here by Raman and ROA spectra of three chiral europium complexes derived from camphor. Since luminescence is strongly suppressed, many vibrational bands can be detected. They carry a wealth of structural information about the ligand and the metal core, and can be interpreted based on density functional theory (DFT) simulations of the spectra. For example, jointly with ROA experimental data, the simulations make it possible to determine absolute configuration of chiral lanthanide compounds in solution.

Computational modeling of angle dependent raman and photoluminescence spectroscopy for investigating 2D molybdenum disulfide flakes induced by 5CB nematic liquid crystal under 532-nm laser excitation

Optical properties of sulfide-based semiconductors, especially MoS2, have gained interest in photonics. This study explored the physical and theoretical perspectives of bare and 5CB-doped MoS2 flakes deposited on a substrate using mechanical and spin coating techniques. The analysis showed that the addition of 5CB nematic liquid crystal (NLC) enhances the E2 g and A1 g modes' intensity and increases the exciton's intensity in the thin layer of MoS2 by utilizing a 532 nm laser. The compressive strain applied through the 5CB changed the optical characteristics of the 2D MoS2 crystal, providing a promising approach for developing high-performance optical devices. The theoretical model achieved through mathematical modeling provided an acceptable level of accuracy in fitting the experimental data. Overall, the study provides insights into the potential applications of MoS2 and 5CB NLC in photonics and highlights the importance of both experimental and theoretical approaches in understanding the material's properties.

Silicon Vacancy Color Centers in 6H-SiC Fabricated by Femtosecond Laser Direct Writing

As a single photon source, silicon vacancy (VSi) centers in wide bandgap semiconductor silicon carbide (SiC) are expected to be used in quantum technology as spin qubits to participate in quantum sensing and quantum computing. Simultaneously, the new direct femtosecond (fs) laser writing technology has been successfully applied to preparing VSis in SiC. In this study, 6H-SiC, which has been less studied, was used as the processed material. VSi center arrays were formed on the 6H-SiC surface using a 1030-nm-wavelength fs pulsed laser. The surface was characterized by white light microscopy, atomic force microscopy, and confocal photoluminescence (PL)/Raman spectrometry. The effect of fs laser energy, vector polarization, pulse number, and repetition rate on 6H-SiC VSi defect preparation was analyzed by measuring the VSi PL signal at 785-nm laser excitation. The results show that fs laser energy and pulse number greatly influence the preparation of the color center, which plays a key role in optimizing the yield of VSis prepared by fs laser nanomachining.

Laser-induced breakdown spectroscopy-guided synergistic phototherapy: A theranostic platform mediated by a single laser wavelength

Currently, cancer theranostic studies have only focused on integrating existing medical imaging techniques with therapeutic modalities. Obviously, this strategy is not a real theranostic method, as diagnosis and therapy are based on different principles and require independent operation. Here, a cancer theranostic method was established by laser-induced breakdown spectroscopy (LIBS)-mediated synergistic photothermal/photodynamic therapy, which was activated by a single 1064-nm light for simultaneous tumor localization and treatment. PEGylated cobalt phosphate (CoP@PEG) nanoparticles (NPs) with strong near-infrared (NIR)-II absorbance, high photothermal conversion efficiency and a reactive oxygen species generation effect were fabricated, and they produced excellent antitumor outcomes under 1064-nm excitation, as evidenced by the substantial increase in HepG2 cell death in vitro and complete tumor elimination in vivo. Meanwhile, the diagnostic method of the LIBS imaging system used in the present study also uses 1064-nm light. The LIBS imaging system can provide fast, real-time analysis and imaging of elements and facilitate the localization of the tumor site by monitoring the distribution of CoP@PEG NPs for precise tumor treatment. We postulate that this theranostic platform will promote the development of further theranostic research.

Controllable fabrication of silver-deposited polyurethane acrylate nanopillar array film as a flexible surface-enhanced Raman scattering (SERS) substrate with high sensitivity and reproducibility.

Acontrollable method for fabricating flexible surface-enhanced Raman scattering (SERS) substrates is demonstratedby depositing silver onto a flexible nanopillar array film. The flexible nanopillar array film was cost-effectively prepared by replicating an anodic aluminum oxide (AAO) template with UV-curable polyurethane acrylate (PUA) over a large area. Then, the deposition of silver was done by an Ar-assisted thermal evaporation. In the deposition process, the partial pressure of Ar was optimized because it has a significant influence on the SERS intensity through the microstructural changes of silver deposited on PUA nanopillars. In addition, the increase in the nanopillar diameter and height enhanced the SERS intensity obtained at 785-nm excitation because of the increased number of hot spots. However, the agglomeration of Ag-deposited nanopillars, which is caused by high aspect ratios, negatively affected the SERS performance in terms of intensity and standard deviation. The optimized Ag-deposited nanopillar array film with nanopillar diameters and heights of 80nm and 200nm exhibited excellent SERS sensitivity and signal reproducibility with stable mechanical flexibility. For application in food and biomedical analysis, it was used for detecting saccharin and peptide and showed a good linear relationship between the SERS intensity and concentration. These findings demonstrate the suitability of our method for the controllable fabrication and optimization of flexible SERS substrates with high sensitivity and reproducibility.

Modeling laser-induced incandescence of Diesel soot\u2014Implementation of an advanced parameterization procedure applied to a refined LII model accounting for shielding effect and multiple scattering within aggregates for {varvec{alpha}}_{{varvec{T}}} and {varvec{E}}left( {varvec{m}} right) assessment

An extensive set of LII signals measured in a Diesel spray flame has been simulated using a refined LII model built upon a comprehensive version of soot heat- and mass-balance equations. This latter includes terms standing for saturation of linear, single- and multi-photon absorption processes, cooling by sublimation, conduction, radiation and thermionic emission in addition to mechanisms depicting soot oxidation and annealing, non-thermal photodesorption of carbon clusters as well as corrective factors allowing considering shielding effect and multiple scattering (MS) within aggregates. A complete parameterization of the so-proposed model has been achieved by means of an advanced optimization procedure coupling design of experiments with a genetic algorithm-based solver. Doing so, the values of different factors involved in absorption and sublimation terms have been assessed for a 1064-nm laser excitation wavelength including the multi-photon absorption cross section for C2 photodesorption and the saturation coefficients for linear- and multi-photon absorption, among others. This parameterized model has then been demonstrated to effectively reproduce signals measured in different combustion media including a CH4/O2/N2 premixed flat flame and a diffusion ethylene flame. As a result of the data derived from the analysis of the Diesel flame, a thermal accommodation coefficient value of 0.49 has been assessed against 0.34 when neglecting the shielding effect. In addition, values of the soot absorption function (Eleft( m right)) comprised between 0.18 and 0.31 have been inferred depending on the particle maturation stage. On the other hand, Eleft( m right) 24% higher on average have been estimated when neglecting MS thus illustrating the importance of aggregate characteristics on soot properties derived through LII modeling. Eventually, the Eleft( m right) evolution observed herein has been compared with results issued from studies conducted with varied hydrocarbons which led to highlight the crucial role played by the soot maturity level over the nature of the burnt fuel as far as optical properties are concerned.

The cause of limited photoelectrochemical water reduction performance of Co3O4 photocathodes

Spinel cobalt oxide Co 3 O 4 has broad light absorption that extends into the near-infrared, making it promising for photoelectrochemical applications (PEC). However, its PEC water reduction performance is modest, and the reason for this has not been clearly explained. In this work, we compare the PEC water reduction performance of Co 3 O 4 photocathodes prepared by two different routes, electrodeposition and spin-coating, and investigate their optical and electronic properties in detail. Despite the two types of Co 3 O 4 films having different interfacial morphologies, surface areas, and optical absorbances, both yield limited photocurrent densities of 6.5 μA cm −2 . The reason for the low PEC water reduction performance of Co 3 O 4 is elucidated by various spectroscopic techniques and ascribed to an unfavorable conduction band edge position. Thus, photogenerated electrons in Co 3 O 4 lack the thermodynamic driving force to reduce water. This research identifies a fundamental characteristic of Co 3 O 4 that is crucial in its development for PEC water reduction. • Co 3 O 4 photocathodes were prepared by electrodeposition and spin-coating. • Various spectroscopic methods were used to study optical and electronic properties. • A definitive energy diagram is obtained and confirmed by spectroelectrochemistry. • Photogenerated electrons in Co 3 O 4 face a large energy barrier to reduce water. • 532-nm excitation possibly causes Co 2+ → Co 3+ via hole transfer from O 2− .

Transient absorption spectroscopy to explore cellular pathways to photobiomodulation.

Photobiomodulation (PBM) describes the use of low irradiance light in the red to near-infrared wavelength range to stimulate biological effects in tissue, and many biological and spectroscopic techniques are used to study PBM. However, these techniques focus on the products or downstream effects rather than the electronic transitions that initiate the PBM processes. This study presents a novel approach to studying low irradiance light exposures on individual proteins and/or protein complexes by combining a continuous wave (CW) laser diode with femtosecond transient absorption spectroscopy (TAS), coined here as CW-TAS, and tests the system on reduced cytochrome c (Cyt c) for proof of principle. TAS was conducted using a 532-nm excitation pump beam and a 350-600nm supercontinuum probe. CW laser diodes with wavelengths of 450nm, 635nm, and 808nm were interchangeably fiber coupled into the HELIOS Fire. Samples of Cyt c were tested by TAS using a pump power of 15μW, both with and without CW exposure. CW exposures were carried out with irradiances of 1.60 and 3.20mW/cm2, except for 808nm, which was only tested at 1.60mW/cm2. Both kinetic and global analyses were performed on the TAS data and the time constants for sets with and without CW exposures were compared. The TAS data for Cyt c with the full dosage of CW exposures did not alter the TAS data distinguishably from the control data. No new electronic transient signals were observed beyond the background when testing Cyt c with the CW exposures. Kinetic analysis confirmed that existing transients did not deviate beyond uncertainty. Global time constants for Cyt c were calculated to be 0.25±0.03ps and 5.1±0.3ps for the control study, and the time constants for the CW exposed Cyt c were not significantly different. This study concludes that CW irradiation, at doses delivered, does not alter the transient absorption data of Cyt c. The CW-TAS method provides a new tool for studying PBM effects in other proteins and protein complexes that might respond to the CW wavelengths, such as Complex IV, in future studies.

Optimization of time domain diffuse correlation spectroscopy parameters for measuring brain blood flow.

.Significance: Time domain diffuse correlation spectroscopy (TD-DCS) can offer increased sensitivity to cerebral hemodynamics and reduced contamination from extracerebral layers by differentiating photons based on their travel time in tissue. We have developed rigorous simulation and evaluation procedures to determine the optimal time gate parameters for monitoring cerebral perfusion considering instrumentation characteristics and realistic measurement noise.Aim: We simulate TD-DCS cerebral perfusion monitoring performance for different instrument response functions (IRFs) in the presence of realistic experimental noise and evaluate metrics of sensitivity to brain blood flow, signal-to-noise ratio (SNR), and ability to reject the influence of extracerebral blood flow across a variety of time gates to determine optimal operating parameters.Approach: Light propagation was modeled on an MRI-derived human head geometry using Monte Carlo simulations for 765- and 1064-nm excitation wavelengths. We use a virtual probe with a source–detector separation of 1 cm placed in the pre-frontal region. Performance metrics described above were evaluated to determine optimal time gate(s) for different IRFs. Validation of simulation noise estimates was done with experiments conducted on an intralipid-based liquid phantom.Results: We find that TD-DCS performance strongly depends on the system IRF. Among Gaussian pulse shapes, pulse length appears to offer the best performance, at wide gates (500 ps and larger) with start times 400 and 600 ps after the peak of the TPSF at 765 and 1064 nm, respectively, for a 1-s integration time at photon detection rates seen experimentally (600 kcps at 765 nm and 4 Mcps at 1064 nm).Conclusions: Our work shows that optimal time gates satisfy competing requirements for sufficient sensitivity and sufficient SNR. The achievable performance is further impacted by system IRF with quasi-Gaussian pulse obtained using electro-optic laser shaping providing the best results.

Intraoperative detection of human meningioma using a handheld visible resonance Raman analyzer.

To report for the first time the preliminary results for the evaluation of a VRR-LRR™ analyzer based on visible resonance Raman technique to identify human meningioma grades and margins intraoperatively. Unprocessed primary and recurrent solid human meningeal tissues were collected from 33 patients and underwent Raman analysis during surgeries. A total of 1180 VRR spectra were acquired from fresh solid tissues using a VRR-LRR™ analyzer. A confocal HR Evolution (HORIBA, France SAS) Raman system with 532-nm excitation wavelength was also used to collect data for part of the ex vivo samples after they were thawed from - 80°C for comparison. The preliminary analysis led to the following observations. (1) The intensity ratio of VRR peaks of protein to fatty acid (I2934/I2888) decreased with the increase of meningioma grade. (2) The ratio of VRR peaks of phosphorylated protein to amid I (I1588/I1639) decreased for the higher grade of meningioma. (3) Three RR vibration modes at 1378, 3174, and 3224cm-1 which were related to the molecular vibrational bands of oxy-hemeprotein, amide B, and amide A protein significantly changed in peak intensities in the two types of meningioma tissues compared to normal tissue. (4) The changes in the intensities of VRR modes of carotenoids at 1156 and 1524cm-1 were also found in the meningioma boundary. The VRR-LRR™ analyzer demonstrates a new approach for label-free, rapid, and objective identification of primary human meningioma in quasi-clinical settings. The accuracy for detecting meningioma tissues using support vector machines (SVMs) was over 70% based on Raman peaks of key biomolecules and up to 100% using principal component analysis (PCA).

F-mode ultraviolet photoacoustic remote sensing for label-free virtual H&E histopathology using a single excitation wavelength.

Photoacoustic remote sensing (PARS) is a novel all-optical imaging modality that allows for non-contact detection of initial photoacoustic pressures. Using 266-nm excitation pulses, ultraviolet PARS (UV-PARS) has previously demonstrated imaging contrast for cell nuclei in histological samples with <400nm resolution. In prior PARS-based imaging schemes, the signal amplitude at an interrogation point was determined by the maximum deflection from the DC scattering signal in response to a pulsed excitation. This method, however, does not take into consideration additional information encoded in the frequency domain of the recorded PARS signals. Here, we present a frequency domain technique called F-mode PARS that can be used to generate images with nuclear and cytoplasmic enhanced contrast, enabling label-free virtual hematoxylin-and-eosin-like microscopy, using only a single excitation wavelength. With F-mode processing, we have been able to demonstrate contrast-to-noise ratios of up to 38 dB between cell nuclei and surrounding cytoplasm, which represents up to a 25-dB improvement over previous implementations of UV-PARS systems.

Fiber-based photoacoustic remote sensing microscopy and spectral-domain optical coherence tomography with a dual-function 1050-nm interrogation source.

.Significance: Spectral-domain optical coherence tomography (SD-OCT) offers depth-resolved imaging of optical scattering contrast but is limited in sensitivity to optical absorption. Dual-modality imaging combined with the noncontact absorption contrast of photoacoustic remote sensing (PARS) microscopy can augment SD-OCT applications with specific molecular and functional contrasts in an all-optical, fiber-based platform.Aim: To develop a fiber-based multimodal PARS and SD-OCT imaging system, which efficiently uses a common 1050-nm light source for SD-OCT and PARS interrogation.Approach: PARS microscopy has predominantly utilized a 1310-nm interrogation light source to date. Hence, a recent dual-modality PARS and 1050-nm SD-OCT imaging system required three distinct wavelengths including a 532-nm PARS excitation, necessitating a free-space optical architecture with discrete subsystems. Here, we validate the first use of a 1050-nm interrogation wavelength for PARS. This enables the transition to fiber-based interferometry as is standard in modern SD-OCT systems, though infeasible with inclusion of an additional 1310-nm wavelength. PARS interrogation functionality is integrated using a broadband optical circulator.Results: Dual-modality imaging is demonstrated in carbon fiber phantoms and a mouse ear in vivo. SD-OCT provided a lateral resolution, axial resolution in air, and of sensitivity, and PARS contributed 532-nm optical absorption contrast with a 47-dB SNR, and lateral and axial resolutions of 2.4 and , respectively. Total interrogation power was reduced from 90% to 58% of the ANSI limit compared to a previous three-wavelength approach.Conclusions: Adapting PARS to use the 1050-nm SD-OCT light source for interrogation enabled implementation of a fiber-based dual-modality system configuration, with image quality maintained. This will facilitate development of potential applications demanding handheld, catheter-based, or endoscopic form factors.

The effects of short term hyperglycemia on human red blood cells studied using Raman spectroscopy and optical trap.

Management of postprandial hyperglycemia is important for preventing severe complications like cardiovascular disease in diabetes patients. The associated glycemic instability in postprandial hyperglycemia may also cause disorders in circulating red blood cells (RBCs). Therefore, effects of short-term hyperglycemic stress on RBCs such as occur in the postprandial condition, have been studied here ex vivo using single-cell Raman spectroscopy and optical trapping. RBCs incubated in high glucose containing media relevant to postprandial hyperglycemia were studied for changes with respect to controls by analyzing the single-cell Raman spectra acquired with Raman optical tweezers with 532nm excitation light. Use of 532nm light for exciting Raman spectra also results in simultaneous photoreduction of intracellular hemoglobin (Hb). The level of photoreduction was noticed to be limited in hyperglycemia-exposed cells in comparison to the control. Since this suggests formation of permanently oxidized Hb in hyperglycemia-exposed RBCs, a fluorescence study was performed which showed elevated levels of oxidative stress in these cells. The changes in the RBC membrane, which may result due to higher levels of oxidative stress, were investigated using optical stretching experiments under the laser trap. The results indicated a loss of elasticity for the RBC membrane due to hyperglycemic exposure.

Ex-vivo confocal Raman microspectroscopy of porcine skin with 633/785-NM laser excitation and optical clearing with glycerol/water/DMSO solution

Confocal Raman microspectroscopy (CRM) with 633- and 785-nm excitation wavelengths combined with optical clearing (OC) technique was used for ex-vivo study of porcine skin in the Raman fingerprint region. The optical clearing has been performed on the skin samples by applying a mixture of glycerol and distilled water and a mixture of glycerol, distilled water and chemical penetration enhancer dimethyl sulfoxide (DMSO) during 30[Formula: see text]min and 60[Formula: see text]min of treatment. It was shown that the combined use of the optical clearing technique and CRM at 633[Formula: see text]nm allowed one to preserve the high probing depth, signal-to-noise ratio and spectral resolution simultaneously. Comparing the effect of different optical clearing agents on porcine skin showed that an optical clearing agent containing chemical penetration enhancer provides higher optical clearing efficiency. Also, an increase in treatment time allows to improve the optical clearing efficiency of both optical clearing agents. As a result of optical clearing, the detection of the amide-III spectral region indicating well-distinguishable structural differences between the type-I and type-IV collagens has been improved.

Virtual hematoxylin and eosin histopathology using simultaneous photoacoustic remote sensing and scattering microscopy.

Hematoxylin and eosin (H&E) staining is the gold standard for most histopathological diagnostics but requires lengthy processing times not suitable for point-of-care diagnosis. Here we demonstrate a 266-nm excitation ultraviolet photoacoustic remote sensing (UV-PARS) and 1310-nm microscopy system capable of virtual H&E 3D imaging of tissues. Virtual hematoxylin staining of nuclei is achieved with UV-PARS, while virtual eosin staining is achieved using the already implemented interrogation laser from UV-PARS for scattering contrast. We demonstrate the capabilities of this dual-contrast system for en-face planar and depth-resolved imaging of human tissue samples exhibiting high concordance with H&E staining procedures and confocal fluorescence microscopy. To our knowledge, this is the first microscopy approach capable of depth-resolved imaging of unstained thick tissues with virtual H&E contrast.