Atopic dermatitis (AD) and psoriasis are the two most prevalent skin disorders, often assessed through subjective questionnaires or visual evaluations conducted by clinicians, which can be subject to interpersonal variations. This study aims to explore the distinctions between these skin conditions and healthy skin using a portable confocal Raman spectroscopy (CRS) system for objective assessment. Spectral measurements at 671 nm and 785 nm on 9 AD, 6 psoriasis, and 11 healthy subjects reveal lower water content in AD compared to psoriasis and healthy skin. Ceramide subclasses show disease-specific trends, distinguishing AD, and psoriasis. Cholesterol levels further differentiate these conditions, with lower concentrations in lesional AD and significantly higher concentrations in lesional psoriasis compared to healthy skin. These differences contribute to the objective differentiation of skin conditions aiding in thorough assessment and treatment monitoring. Furthermore, it offers valuable insights for developing targeted disease-specific topical treatments.
Vulvar skin, distinct from other areas, undergoes changes due to aging, causing symptoms like dryness and itchiness. While much research focuses on facial or forearm skin, vulva skin properties are underexplored. This study uses an in-house developed fiber-based Diffuse Reflectance Spectroscopy (DRS) system to assess vulva skin changes in 100 women. This objective evaluation includes analyzing tissue chromophores—water, lipid, oxyhemoglobin, and deoxyhemoglobin providing insights into moisture content, lipid levels, oxygen saturation, and blood fraction. DRS, compared to invasive methods, achieved a 65% accuracy in estimating estrogen levels, suggesting its potential for objective diagnosis and monitoring of genitourinary skin conditions.
The growing demand for innovative agricultural technologies drives our research on photonics-based solutions for non-destructive plant analysis. Our work introduces two techniques to overcome the limitations of conventional methods. The first part presents a portable VIS-NIR handheld spectrometer, showcasing strong correlations (0.84 and 0.77) for quantifying anthocyanin and chlorophyll content. In the second part, a customized fiber optic probe using ATR-FTIR enables measurements of plant parameters (water content, antioxidant activity, lignin, and cellulose). Statistical analysis of high-resolution spectra introduces the novel index NDMRI for effective phytochemical differentiation. These non-destructive, rapid, and objective methods promise to optimize agriculture and drive advancements in this field.
Non-melanoma skin cancers (NMSC) pose challenges with current clinical approaches. In this context, Multispectral Optoacoustic Tomography (MSOT) offers a promising non-invasive imaging solution. With high isotropic resolution and contrast-enhanced capabilities, MSOT provides a 3D tumor map by resolving melanin and haemoglobin signals. Our feature extraction and automated level-set image segmentation algorithm enables tumor profiling and precise boundary delineation of width, depth, and volume. Validated against histology, these metrics aid preoperative tumor mapping and surgical planning as it fosters a comprehensive understanding of tumor morphology and metabolic activities. Thus, clinicians can optimize NMSC management, revolutionizing diagnostics and treatment for improved patient outcomes.
We report on fluorescence enhancement using a suspended core photonic crystal fiber (PCF) as an optofluidic platform. By employing metallic nanoparticles and an organic spacer, we achieved a thirty-fold signal enhancement of Cy5 dye at picomolar concentrations. The combination of fluorescence enhancement and PCF offers robustness, ease of use, and high sensitivity. This comprehensive study explores fluorescence enhancement using PCF, highlighting the significant enhancement achieved through metallic nanoparticles and organic spacers associated by the long length of light-analyte interactions offered by the PCF. These findings might contribute to the development of highly sensitive optical fiber-platforms for biomedical applications.
Breast cancer is the most common cancer worldwide. Mammography screening and biopsy procedures for abnormal mammograms are the gold standard detection method, however, it is invasive, time-consuming, and labor-intensive. RNA biomarkers in circulating blood may be an alternative to the gold standard. We have adopted a multi-modal approach using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy that provides a complete characterization of RNA biomarker fingerprints in the full spectrum. We have measured 99 patients’ serum samples and achieved a higher accuracy, specificity, and sensitivity using the multi-modal approach combined with machine learning analysis than using the individual techniques alone.
Surface enhanced Raman scattering (SERS) is a powerful biosensing technique allowing direct detection of target molecules thanks to their vibrational fingerprint Raman spectra. SERS is usually performed on nano roughened plamonic planar substrates/colloidal nanoparticles. However, the irregularities of plasmonic nanostructures lead to measurement reliability limitations. We have recently demonstrated that SERS-probes based on opto-fluidic photonic crystal fiber (PCF) composed of a silica-core surrounded by large air channels are remarkable sensing platforms leading to tremendous SERS sensitivity and excellent measurement reliability (98% in reproducibility and 95% in repeatability). However, a major limitation occurs when looking for highly reliable and easy-to-use biosensing platform. Actual SERS biosensors (planar substrate or fiber probe) require their alignment under a microscope, which could restrict on-field practical use. Here, we address this issue by developing a tapered opto-fluidic PCF allowing excellent reliability, efficient and easy coupling through a Plug-&-Play type modality. This novel type of SERS probe realized by reducing the fiber diameter, which increases the SERS sensitivity while enabling efficient light coupling to the Raman spectrometer with a relative standard deviation (RSD) of only 3.5% in reproducibility and 3.84% in repeatability. We demonstrate this easy Plug-&-Play type coupling based on a simple bare fiber connector, with a RSD of 4.5% in reproducibility measurements (i.e. removing and reconnecting the fiber SERS-probe to the Raman spectrometer without any additional alignment). We envision that this easy-to-use platform can be translated to - clinically viable SERS probes for liquid biopsy.
Surface enhanced Raman spectroscopy (SERS) allows sensitive detection of analytes, thanks to their vibrational Raman spectra. Planar SERS substrates often lack the reliability in measurement due to larger variations in signal intensity contributed by irregularities in nanostructures. In this context, photonic crystal fibers (PCFs) that combine excellent light guiding properties and the possibility to incorporate nanostructures and liquid or gas analytes into their axially aligned air holes, offer tremendous promise as an opto-fluidic SERS platform. Such sensors possess the enormous signal enhancement inherent to SERS and the flexibility of optical fibers. In addition, PCFs offer improved reproducibility, repeatability and sensitivity in measurement compared to planar substrates, due to the larger volume of interaction between the guided light and the analyte, and to highly reliable light couplings into the fiber core. Here, we present a novel design of PCF called ring core fiber (RCF), which is specifically engineered to further increase the interaction area in order to improve the sensitivity and reliability of the sensor. Preliminary experimental results showed that sensitivity of SERS sensing is improved by 115% compared to the best SuC-PCFs. Ongoing numerical simulations indicate that by further optimizing the dimensions of the ring, sensitivity could be improved by at least one order of magnitude with RCF. We envision that this new design with increased sensitivity and measurement reliability could be the next major step towards a clinically viable liquid biopsy fiber probe.
Atopic dermatitis (AD) is a common inflammatory skin disorder which affects ~20% of children and ~3% adults worldwide. There lacks a direct, non-invasive method of evaluating atopic dermatitis (AD) accurately. Here, the use a multispectral raster-scanning optoacoustic mesoscopy (MS-RSOM) as an objective imaging tool for AD is proposed. MS-RSOM is a novel, non-invasive optoacoustic imaging modality which can provide label-free, high resolution imaging up to 1.5 mm below the skin. It can provide useful information on melanin, oxyhemoglobin (HbO2), deoxyhemoglobin (Hb) and oxygen saturation (sO2) from the skin layers. This preliminary study was conducted on 4 AD patients and 2 healthy volunteers using MS-RSOM system. From the MS-RSOM images, the epidermis thickness and oxygen saturation were computed from the healthy volunteers as well as from the non-lesional and eczema lesional areas of the eczema subjects.
Confocal Raman spectroscopy (CRS) technology has wide applications, especially in the biomedical field. CRS provides non-destructive, contrast-free and molecule-specific quantitative measurement of samples, including biological tissues. These advantages make it ideal for human skin characterization. We present a portable dual-wavelength CRS system with a handheld measurement probe which connected to the console by optical fibers. To achieve fast switching between the two wavelengths, a fast 2-to-1 fiber array multiplexing module was used. A large bandwidth could be covered at each measurement point in real time. We performed system characterization for this proposed CRS system and measured different samples.
A comprehensive analysis using three machine-learning models for an AI-aided atopic dermatitis (AD) diagnosis and sub-classifying AD severities with 3D Raster Scanning Optoacoustic Mesoscopy (RSOM) images, extracted features from volumetric vascular structures and clinical information.
A flexible membrane based Surface-Enhanced Raman Spectroscopy (SERS) sensor was developed as a viable point-of-care platform to monitor changes of these surrogate indicators of healing status in chronic wounds, such as tumor necrosis factor alpha (TNFα) and matrix metalloproteinase (MMPs). In terms of performance, SERS approach is superior to enzyme-based assays, which are resource intensive. We demonstrated the efficiency of this flexible SERS platform for the sensitive detection of TNFα and MMP9 in the nM to pM range. These substrates may be incorporated into wound dressings to permit routine monitoring of wound status.
Inflammatory skin disorder, eczema, is usually assessed by subjective disease scoring systems such as SCORAD and EASI. These scoring systems are based on clinical observations and questionnaires and hence it is subjected to inter and intra-assessor variability. Here, for the first time, we used optoacoustic imaging to image the structural and morphological changes of the skin in a non-invasive manner. Through a clinical study, we computed specific metrics such as epidermis thickness, total blood volume, vessel diameter in the dermis, ratio of low and high frequency signals. We trained a linear kernel-based support vector machine model for eczema classification using these metrics. We could achieve an accuracy of 86.6% and high sensitivity and specificity of 96.2% and 82.1% respectively. We also formulated a novel Eczema Vascular and Structural Index (EVSI) to objectively assess the severity of eczema.
We report a label-free Surface Enhanced Raman Spectroscopy (SERS) for pleural fluid analysis to distinguish Lung cancer from controls patients. Herein, we have used a novel silver coated silicon Nanopillar (SCSNP) as SERS substrate to acquire multiple SERS spectra for each pleural fluid sample and advanced chemometrics methods. We report a classification accuracy of 85% along with sensitivity and specificity of 87% and 83% respectively for the detection of Lung cancer over control pleural fluid samples with a receiver operating characteristics (ROC) area under curve value of 0.92 using PLS-DA binary classifier to distinguish between lung cancer over control subjects.
The hemodynamics and oxygen saturation status of vascular are very important biomarkers for disease, such as brain glioma tumor and ischemia-reperfusion ulcer. Therefore, a high spatial resolution imaging tool for vascular imaging is demanded. Conventional optical imaging modalities, including confocal microscopy and two-photon microscopy, require external contrast agent to image blood vessels and are not sensitive to oxygen saturation. The development of photoacoustic microscopy provides a contrast-free, high-spatial resolution and functional vascular imaging tool. It’s gaining more and more popularity in biomedical research. In this paper, we introduce a dual-wavelength opticalresolution photoacoustic microscopy (OR-PAM) system for functional imaging of vasculature. This system has demonstrated its application in brain glioma tumor imaging, as well as skin ischemia-reperfusion imaging.
Gold-coated array patterned with tightly-packed nanospheres was developed as a substrate base for constructing SERSenriched
nanogaps with Au-nanoparticles (GNPs). Using 1,2-ethanedithiol as a linker, Au-NPs (=17-40nm) were
anchored covalently on the sphere-array. Thin Au layer was sputtered on the substrate to mask the citrate coating of
GNPs that could demote the sensing mechanism. The negatively-charged GNP surface warrants the colloidal stability,
but the resulting repulsive force keeps the immobilized NPs apart by about 40nm. The attained gap size is inadequately
narrow to sustain any intense enhancement owing to the near-field nature of SERS. Minimal amount of NaCl was then
added to slightly perturb the colloidal stability by reducing their surface charge. Notably, the interparticle-gap reduces at
increasing amount of salt, giving rise to increased packing density of GNPs. The SERS enhancement is also found to
exponentially increase at decreasing gap size. Nevertheless, the minimum gap achieved is limited to merely 7nm.
Excessive addition of salt would eventually induce complete aggregation of particles, forming clustered NPs on the
array. A simple sputtering-growth approach is therefore proposed to further minimize the interparticle gap by enlarging
the seeded NPs based on mild sputtering. The SEM images confirm that the gap below 7nm is achievable. With advent
of the colloidal chemistry, the combined salt-induced aggregation and sputtering-growth techniques can be applied to
engineer interparticle gap that is crucial to realize an ultrasensitive SERS biosensor. The proposed two-step preparation
can be potentially adopted to fabricate the SERS-enriched nanogaps on the microfluidics platform.
Nanostructure substrates are effective biosensor to spectrally differentiate multiple compounds by Surface-enhanced
Raman scattering (SERS). Metal film over nanosphere (MFON) has been demonstrated to exhibit reproducible and
predictable Raman enhancement. MFON can be fabricated using an economical process in which polystyrene (PS)
nanospheres are self-assembled on a planar solid supports and then followed by metal coating. In this work, we
investigate the MFON substrates with bimetallic coating to combine the optical-enhancing and stability features from Ag
and Au layers. The SERS responses are then quantified from the resultant bimetallic structures with 2-Naphthalenethiol.
We show that the bimetallic substrate of optimal Au/Ag thickness ratio renders SERS enhancement and stability
exceeding those of the Au-coated MFON. Compared to Au array, the bimetallic substrate exhibits quasi-bimetallic
nanoparticles of surpassing SERS (2.5 times) with enhancement factor determined to be 2×107. As a proof-of-concept for
biosensing in microfluidics, SERS nanotag was prepared and tested on the optimized BMFON. In addition, we propose a
fabrication scheme to construct MFON with alternating sizes (100nm and 400nm) of nanosphere. At optimal
proportional amount, the 100nm-spheres were packed within the gaps between the 400nm-spheres. The resultant
morphology renders additional nanogaps that could possibly lead to increment in SERS enhancement.
Fluorescence spectroscopy is a powerful and widely used technique, which finds extensive applications in biochemistry
and molecular biology. In many cases, detection of fluorescence from biological samples at low concentration demands
for a sensitive technique that can enhance the weak fluorescence signal. In order to realize this, metal enhanced
fluorescence technique is employed where an increase in fluorescence is observed when the fluorophore is in close
proximity to a metallic surface. In order to achieve this, nano-roughened silver surfaces such as fractal structures or
silver colloid-coated surfaces can be employed. However, preparation of such surfaces not only involves lengthy
chemical procedures but also result in poor reproducibility. To overcome these limitations, nanosphere lithography
(NSL) is proposed, which is an inexpensive, simple to implement and high throughput nanofabrication technique. In this
technique, polystyrene (PS) nano-beads are used to form a 2D monolayer of nanoparticle array followed by deposition of
silver to form a roughened metallic surface. The surface roughness of the silver coating is determined by the close
packing and arrangement of the nanobeads. In this work, substrates are fabricated using different sizes of PS beads to
result in different nanometric surface roughening for silver layer and its optimization to achieve better fluorescence
enhancement is carried out.
Temporal changes in signal intensity of Surface Enhanced Raman Scattering (SERS) upon laser excitation is an
interesting phenomenon in plasmonics. In-depth understanding of the phenomena is highly important especially when
developing a SERS sensor based on the intensity variation of particular Raman peak/band. One of the main challenges in
such a technique is the intensity reduction at a given location upon consecutive measurements. Previously, signal loss in
SERS measurement was attributed to the electric-field induced roughness relaxations in the SERS active surface. In such
cases, as the surface is smoothened out, signals are completely lost. In our observation, the reduction in the spectral
intensity is irreversible but never completely lost and a major part of it can be attributed to the plasmon induced heating
effect. Here, we experimentally demonstrate this effect by studying the SERS signal from four different Raman active
molecules adsorbed onto substrates that contain uniform nano-roughened bi-metallic silver/gold coating. Possible
mechanism that leads to irreversible signal loss is explained. Moreover, solutions for minimising such plasmonic heating
when developing a biosensor are also discussed.
A successful detection of inherently weak Raman signal from molecules is possible with giant enhancement of signal by the process of surface-enhanced Raman scattering (SERS). The SERS-induced enhancement is typically achieved when the molecules adsorbed onto the surface of a noble-metal substrate with nanometric roughness. Such SERS-substrate could be economically fabricated by convective assembly of polystyrene beads followed by metal deposition. The
characterization of mono-metallic substrate showed that the SERS enhancement factor increases with increasing
thickness of Ag or Au, with Ag-substrate giving the greatest SERS enhancement. However, the formation of silver oxide
layer could reduce the shelf-life of the Ag-substrate. Alternatively, Au is also used as the coating material owing to its
chemical inertness and biocompatibility. Despite the decent enhancement of the Au-substrate, Au-layer was found to be
unstable after prolonged incubation in crystal violet solution. The inherent deficiency in adhesiveness of Au to the glass
limits its use as a reliable and cost-effective substrate. In an attempt to improve the SERS-substrate, bimetallic substrate
was fabricated by depositing the Au-film, as a protective layer, on the Ag-substrate. In this case, the top layer of Au of
the bimetallic substrate remained intact after chemical treatment. Furthermore, the bimetallic substrate was shown to
give comparable level of enhancement as an Ag-substrate by choosing a proper thickness ratio of the bimetallic layers.
The result suggests that the design of bimetallic substrate could be optimized to maximize the SERS enhancement while
retaining a decent stability after laser illumination and chemical treatment. Our findings suggest that bimetallic substrates
are potentially useful for a reliable SERS-based biosensing.
Surface Enhanced Raman Scattering (SERS) technique is used as an indispensable and sensitive modality for bio-sensing
due to its ability to distinguish the analyte molecules based on their distinct 'fingerprint' spectra. One of the most
promising SERS substrates for biosensing was fabricated by coating noble metal film over orderly packed nanospheres.
However, the major challenge in developing such a sensor is to achieve reproducible SERS substrate. Here, we report a
new class of SERS substrate with ordered 3D nanostructures fabricated on silicon wafer by deep UV lithography
technique followed by bi-metallic coating of silver and gold. Compared to the substrate fabricated by conventional
nanosphere lithography, this approach allows better control of the nanostructures, which in turn gives uniform surface
roughness for the metal film to provide adequate SERS enhancement with high reproducibility. Significance of this
substrate for biomedical application was demonstrated by glucose sensing under physiologically relevant conditions.
Partitioning and localization of glucose molecules within the first few nanometers of active SERS substrate was achieved
by a self assembled monolayer (SAM) on the surface of substrate.
We present the implementation of a fluorescence lifetime imaging microscopy (FLIM) system for cellular
characterisation. FLIM system can be used as an investigative tool to identify minor biochemical changes in cellular
abnormalities. These subtle changes could possibly alter cellular fluorescence properties such as emission wavelength
and lifetime. In this study, the fluorescence lifetime of haematoxylin and eosin (H&E)-stained tissues were investigated
using a wide-field time-domain FLIM system. The transient response of epithelial fluorescence was investigated and the
lifetime extracted using a bi-exponential model. It was found that the fluorescence lifetimes of eosin can be correlated to
the tissue histology. The preliminary result suggests that tumor-associated molecules are retained in the tissues even after
tissue fixation and staining. The developed FLIM system was successfully applied to detect the histological changes in
the tissue samples. Optimization of system parameters is also discussed.
A novel homodyne signal processing assisted phase-resolved optical system for the imaging of latent fingerprints is proposed. A multistep phase shifting method is introduced to remove the DC part of the fluorescence signals. Experiments are carried out with simulated fingerprint samples where their lifetime and emission wavelength are in close range to that of background fluorescence. The proposed phase-resolved technique can suppress the background fluorescence provided there is lifetime difference between two emissions.
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