ATR-IR study of skin components: Lipids, proteins and water. Part I: Temperature effect

Effect of extracorporeal circulation on structure of main components of animal plasma - ATR-IR and 2D-COS studies: Part I

Every year, more and more adults and children with severe cardiac and/or respiratory failure require connection to extracorporeal circulation (ECC). Despite a life-saving role in emergency settings, the use of ECC is associated with several serious complications, which result from structural changes in the plasma components. As yet, the molecular mechanism of these changes was not well recognized, and therefore we undertook the first spectroscopic study of structural changes in plasma during ECC. Vibrational spectroscopy coupled with two-dimensional correlation spectroscopy (2D-COS) is a powerful tool for elucidation of variations at a molecular level. The spectra of animal plasma were recorded by ATR-IR (Attenuated Total Reflection-Infrared) technique, which enables measurements of strongly absorbing samples in a non-destructive way. Moving-window and 2D-COS methods were used to obtain more detailed information about the correlation between spectral features and vibrations of functional groups. A comprehensive analysis of variations in the main plasma components requires using bands from both polar (NH, OH, CO, and CO) and non-polar groups (aliphatic and aromatic moieties). Of particular interest is the effect of the state of water on the structure and intermolecular interactions of the plasma under ECC.

Wearable transdermal drug delivery system controlled by wirelessly powered acoustic waves

Transdermal drug administration offers an alternative route for drug delivery through the skin, and surface acoustic wave (SAW) technology has recently emerged as a promising approach to enhance this process. However, conventional cable-connected SAW control units face several challenges, including inconvenience, poor wearability, limited miniaturization and integration, and restricted reusability. This study introduces a wireless-powered transport strategy for the transdermal delivery of large drug molecules using a thin-film-based SAW platform. This approach leverages interfacial acoustic stimulation, localized acoustic heating, and streaming/micro-cavitation to enhance drug penetration. By eliminating the need for physical connections, the wireless power transfer system reduces potential heating effects and localized tissue damage. To evaluate its performance, synthetic skin-like agarose gel and pig skin tissue were used as models. Hyaluronate rhodamine (5000 Da) was successfully delivered transdermally into pig skin tissue, achieving approximately 77.89 % of the efficiency observed with a conventional cable-connected SAW platform. These findings highlight wireless SAW technology as a promising alternative for enhancing transdermal drug delivery, offering a safer, more effective, and user-friendly therapeutic solution for patients.

Multi-Dimensional Assessment and Analysis of Thermal Damage in Skin Tissue by Femtosecond Laser Welding

In this study, four thermal damage assessment methods were used to investigate the thermal damage caused by femtosecond lasers on skin tissues. Collagen volume and texture characteristic parameters of the skin microstructure were calculated and analyzed by Masson staining of skin samples and grayscale covariance matrix. The skin thermal damage parameters and the degree of skin protein denaturation were analyzed by the Arrhenius equation and Raman spectroscopy. The results show that as the laser power increases or the scanning speed decreases, the collagen volume of skin tissue decreases, the angular second-order moments and correlations increase, the entropy value and contrast decrease, the parameters of thermal damage of skin tissue increase, the intensity of the characteristic peak spectral bands of the Raman spectrum of skin tissue in regions 1 and 4 decreases, and the degree of protein denaturation increases, which indicates that the degree of thermal damage of skin tissue increases.

Co-delivery of minoxidil and finasteride via ionic liquid and cyclodextrin-assisted in situ thermosensitive hydrogel for synergistic treatment of androgenic alopecia

Androgenic alopecia (AGA), the most prevalent type of progressive hair loss, currently lacks an effective topical treatment regimen. In this study, we synthesized an ionic liquid (IL) to co-solubilize minoxidil (MXD) and finasteride (FIN) and subsequently formulated them into an in situ thermosensitive ionic liquid/cyclodextrin/poloxamer hydrogel (ICPG), termed M + F@ICPG. M + F@ICPG was developed for the transdermal co-delivery of these two drugs, aiming to provide a multipath therapeutic approach for AGA while avoiding the adverse effects commonly associated with oral FIN and topical MXD tincture. The thermosensitive characteristics, skin penetration, hair follicle (HF) targeting efficiency, biosafety, and in vivo therapeutic efficacy of M + F@ICPG were evaluated using an AGA mouse model. Our results demonstrated that M + F@ICPG was a thermosensitive hydrogel, transitioning from solution to gel upon contact with the scalp. Compared to the FIN suspension and MXD tincture, M + F@ICPG significantly enhanced the skin penetration (∼2.2-fold) and retention (∼8.6-fold) of FIN and increased the relative retention of MXD (∼6.3-fold) in the skin. Moreover, M + F@ICPG exhibited a HF targeting index of 1.74 for MXD and 1.46 for FIN, indicating enhanced drug targeting to HF. M + F@ICPG showed superior in vivo efficacy in terms of hair regeneration, anagen recovery, inflammation mitigation, and microvessel reconstruction. The underlying mechanism was attributed to the upregulation of hair growth genes, downregulation of hair loss genes, and reduction of abnormally elevated inflammatory factors. These findings suggest that this novel M + F@ICPG is a promising topical co-delivery system for the synergistic treatment of AGA.

Transdermal Delivery of Valproate-Choline Ionic Liquid Induces Hair Regrowth

Alopecia treatment research has been increasingly focused on innovative materials systems and drug delivery methods. Valproic acid (VPA) has been shown to promote hair regrowth by upregulating the Wnt/β-catenin signaling pathway, a key regulator of hair papilla cell proliferation. However, topical administration of VPA typically requires organic solvents or complex transdermal devices to enhance skin penetration. Biocompatible ionic liquids have gained attention as customizable solvents for transdermal drug delivery (TDD). In this study, we introduce a novel choline-based valproic acid ionic liquid (VPA-IL) for the treatment of hair loss. Our findings demonstrate that VPA-IL significantly enhances the transdermal penetration of VPA by disrupting the lipid bilayer structure of stratum corneum (SC), due to strong hydrogen bonding between the methyl hydrogen of the choline and the carboxyl group of phospholipid molecules. In vivo pharmacodynamic assessments revealed that topical application of VPA-IL effectively promotes hair regrowth by activating the Wnt/β-catenin pathway and upregulating proliferating cell nuclear antigen (PCNA), K14, loricrin, and several hair follicle (HF) stem cell markers without causing skin irritation or systemic toxicity. This work offers a safe and promising new therapeutic option for alopecia.

Development of levamlodipine long-acting patches based on an ion-pair strategy: Investigation of the mechanism for reducing skin irritation

The aim of this study was to develop a long-acting transdermal patch of levamlodipine (LAM) using an ion-pair strategy to reduce the skin irritation induced by topical application of LAM and explore the mechanism underlying the improvement of skin irritation. The formulation was optimized through porcine in vitro transdermal experiments and rabbit in vivo skin irritation tests. The obtained formulation consisted of poly (2-Ethylhexyl acrylate-co-N-Vinyl-2-pyrrolidone-co-N-(2-Hydroxyethyl) acrylamide) (PENH) as the adhesive matrix, 13.00 % levamlodipine-sorbic acid ion-pair complex (LAM-SA) (w/w), and 10 % isopropyl myristate (IPM) (w/w), with a patch thickness of 70 μm, achieving an erythema index of 188 for rabbit skin and 117-187 for human skin (264 for rabbit skin and 110-260 for human skin in the absence of sorbic acid (SA)). In vivo rabbit and human skin erythema analysis and H&E staining verified that the optimized ion-pair patch effectively reduced skin irritation. Drug distribution experiments in the skin, ATR-FTIR, and molecular simulation were used to characterize the mechanism by which the ion-pair reduced skin irritation. Excessive accumulation of LAM in the epidermis induced secondary structural changes in keratin, resulting in skin barrier damage and inflammatory response. The formation of the LAM-SA ion pair altered physicochemical properties of LAM, reducing drug retention in the epidermis and, thereby, reducing skin irritation. This study demonstrated the potential of the ion-pair strategy to improve the safety of transdermal drug delivery system (TDDS) and provided a means for reducing skin irritation caused by the active pharmaceutical ingredient (API) itself.

Sensing the Changes in Stratum Corneum Using Fourier Transform Infrared Microspectroscopy and Hyperspectral Data Processing

The stratum corneum (SC) forms the outermost layer of the skin, playing a critical role in preventing water loss and protecting against external biological and chemical threats. Approximately 90% of the SC consists of large, flat corneocytes, yet its barrier function primarily relies on the intercellular lipid matrix that surrounds these cells. Traditional methods for characterizing these lipids, such as Fourier transform infrared spectroscopy (FTIR), typically involve macroscopic analysis using attenuated total reflection (ATR) techniques. In this study, we introduce a novel approach for investigating SC samples at a microscopic level to gain detailed chemical insights and assess sample heterogeneity. Special emphasis is placed on advanced hyperspectral data pre-processing to ensure the accuracy and reliability of the results. We also evaluate methods for filtering out spectral data that significantly deviate from the mean and analyze the extracted mean spectra, the intensities of specific infrared peaks, and their ratios. The novelty of this work lies in its microscopic approach to analyzing the SC lipid matrix, diverging from the traditional macroscopic FTIR-ATR methods. By focusing on hyperspectral imaging and developing robust pre-processing techniques, this study provides more localized, high-resolution chemical insights. This microscopic perspective opens up the possibility of detecting subtle heterogeneities within the skin's lipid matrix, offering deeper, previously unattainable understanding of the SC's barrier function. Additionally, the exploration of spectral filtering methods enhances the precision of the analysis, paving the way for more refined and reliable investigations of skin structure and behavior in future research.

Non-invasive glucose extraction by a single polarization rotator system in patients with diabetes

This study utilizes a Mueller matrix-based system to extract accurate glucose levels from human fingertips, addressing challenges in skin complexity. Integration of domain knowledge and data science aims to enhance prediction accuracy using a Random Forest model. The primary goal is to improve glucose level predictions by selecting effective features based on the Pearson product-moment correlation coefficient (PPMCC). The interpolation compensates for delayed glucose concentration. This study integrates domain knowledge and data science, combining a Mueller matrix-based system and a random forest model. It is noted that 16 effective features were identified from 27 test points collected from a healthy volunteer in the laboratory. These features were divided into training and prediction sets in a ratio of 8:2. As a result, the regression coefficient, R2, was 0.8907 and the mean absolute relative difference (MARD) was 6.8%, respectively. This significantly improves prediction accuracy, demonstrating the model's robustness and reliability in accurately forecasting outcomes based on the identified features. In addition, in the Institutional Review Board (IRB) tests at NCKU's hospital, all data passed the same preprocessing and model. The measurement results from an individual diabetic patient demonstrate high accuracy for blood glucose concentrations below 150 mg/dL, with acceptable deviation at higher levels and no severe error zones. Over a three-month period, data from the participating diabetic patient showed a MARD of 4.44% with the R2 of 0.836, and the other patient recorded a MARD of 7.79% with the R2 of 0.855. The study shows the proposed approach accurately extracts glucose levels. Integrating domain knowledge, data science, and effective strategies significantly improves prediction accuracy.

Microporous electrospun nonwovens combined with green solvents for the selective peel-off of thin coatings from painting surfaces

Over the last few decades, significant research efforts have been devoted to developing new cleaning systems aimed at preserving cultural heritage. One of the main objectives is to selectively remove aged or undesirable coatings from painted surfaces while preventing the cleaning solvent from permeating and engaging with the pictorial layers. In this work, we propose the use of electrospun polyamide 6,6 nonwovens in conjunction with a green solvent (dimethyl carbonate). By adjusting the electrospinning parameters, we produced three distinct nonwovens with varying average fiber diameters, ranging from 0.4 μm to 2 μm. These samples were characterized and tested for their efficacy in removing dammar varnish from painted surfaces. In particular, the cleaning process was monitored using macroscale PL (photoluminescence) imaging in real-time, while post-application examination of the mats was performed through scanning electron microscopy. The solvent evaporation rate from the different nonwovens was evaluated using gravimetric analysis and Proton Transfer Reaction- Time-of-Flight. It was observed that the application of the nonwovens with small or intermediate pore sizes for the removal of the terpenic varnish resulted in the swollen resin being absorbed into the mats, showcasing a peel-off effect. Thus, this protocol eliminates the need for further potentially detrimental removal procedures involving cotton swabs. The experimental data suggests that the peel-off effect relates to the microporosity of the mats, which enhances the capillary rise of the swollen varnish. Furthermore, the application of these systems to historical paintings underwent preliminary validation using a real painting from the 20th century.

Mechanical behavior of full-thickness burn human skin is rate-independent

Skin tissue is recognized to exhibit rate-dependent mechanical behavior under various loading conditions. Here, we report that the full-thickness burn human skin exhibits rate-independent behavior under uniaxial tensile loading conditions. Mechanical properties, namely, ultimate tensile stress, ultimate tensile strain, and toughness, and parameters of Veronda-Westmann hyperelastic material law were assessed via uniaxial tensile tests. Univariate hypothesis testing yielded no significant difference (p > 0.01) in the distributions of these properties for skin samples loaded at three different rates of 0.3 mm/s, 2 mm/s, and 8 mm/s. Multivariate multiclass classification, employing a logistic regression model, failed to effectively discriminate samples loaded at the aforementioned rates, with a classification accuracy of only 40%. The median values for ultimate tensile stress, ultimate tensile strain, and toughness are computed as 1.73 MPa, 1.69, and 1.38 MPa, respectively. The findings of this study hold considerable significance for the refinement of burn care training protocols and treatment planning, shedding new light on the unique, rate-independent behavior of burn skin.

Identification and determination of different processed products and their extracts of Crataegi Fructus by infrared spectroscopy combined with two-dimensional correlation analysis

The fruit of Crataegus sp. is known as "Shanzha (SZ)" in China and is widely used in the food, beverage, and traditional Chinese medicine (TCM) industries. SZ usually requires thermal processing to reduce the irritation of its acidity to the gastric mucosa. Different processed products of SZ resulting from thermal processing have different or even opposite functions in clinical applications. In addition, 5-hydroxymethylfurfural (5-HMF) intermediates produced during thermal processing are carcinogenic to humans. Therefore, the aim of this study was to explore a rapid and accurate method by Fourier transform infrared spectroscopy (FT-IR) for the identification of different processed products and the determination of 5-HMF in extracts. In qualitative identification, a three-stage infrared spectroscopy identification method (raw spectra, the second derivative spectra, and two-dimensional correlation (2DCOS) spectra) was developed to distinguish different processed products of SZ step by step. In quantitative determination, partial least squares regression combined with different variable selection methods, especially the 2DCOS method, was applied to determine the 5-HMF content. The results show that temperature-induced 2DCOS synchronous spectra can effectively identify different processed products of SZ by shape, intensity, and position of auto-peaks or cross-peaks, and the variables selected by power spectra from concentration-induced 2DCOS synchronous spectra have better prediction ability for 5-HMF compared to full variables. The above results demonstrate that 2D-COS analysis is a potential tool in qualitative and quantitative analysis, which can improve sample identification accuracy and determination capabilities. This study not only establishes a rapid and accurate method for the identification of different processed products but also provides a practical reference for food safety and the efficient use of TCM.

Effect of femtosecond laser process parameters on the thermal denaturation degree of skin tissue

The influence of femtosecond laser parameters on the degree of thermal denaturation was studied experimentally. The relationship between the degree of thermal denaturation and the characteristic parameters of skin microstructure and the secondary structure of skin tissue proteins in characterizing the degree of thermal damage was analyzed. The results showed the interaction of laser power, laser power, and scanning speed had a significant effect on the degree of thermal denaturation; greater degrees of thermal denaturation were associated with larger second-order moments of the texture angle of the skin microtissue and smaller entropy values and contrast, indicating a greater degree of thermal damage; and higher peak temperature, the lower peak intensity of Raman spectra, decrease in the percentage area of α-helix fitted curves and increase in the percentage area of β-sheet and β-turn fitted curves indicate that the protein is denatured to a large extent that means thermal damage is large.

Exploration of macromolecular phenotype of human skeletal muscle in diabetes using infrared spectroscopy

Introduction

The global burden of diabetes mellitus is escalating, and more efficient investigative strategies are needed for a deeper understanding of underlying pathophysiological mechanisms. The crucial role of skeletal muscle in carbohydrate and lipid metabolism makes it one of the most susceptible tissues to diabetes-related metabolic disorders. In tissue studies, conventional histochemical methods have several technical limitations and have been shown to inadequately characterise the biomolecular phenotype of skeletal muscle to provide a holistic view of the pathologically altered proportions of macromolecular constituents.

Materials and methods

In this pilot study, we examined the composition of five different human skeletal muscles from male donors diagnosed with type 2 diabetes and non-diabetic controls. We analysed the lipid, glycogen, and collagen content in the muscles in a traditional manner with histochemical assays using different staining techniques. This served as a reference for comparison with the unconventional analysis of tissue composition using Fourier-transform infrared spectroscopy as an alternative methodological approach.

Results

A thorough chemometric post-processing of the infrared spectra using a multi-stage spectral decomposition allowed the simultaneous identification of various compositional details from a vibrational spectrum measured in a single experiment. We obtained multifaceted information about the proportions of the different macromolecular constituents of skeletal muscle, which even allowed us to distinguish protein constituents with different structural properties. The most important methodological steps for a comprehensive insight into muscle composition have thus been set and parameters identified that can be used for the comparison between healthy and diabetic muscles.

Conclusion

We have established a methodological framework based on vibrational spectroscopy for the detailed macromolecular analysis of human skeletal muscle that can effectively complement or may even serve as an alternative to histochemical assays. As this is a pilot study with relatively small sample sets, we remain cautious at this stage in drawing definitive conclusions about diabetes-related changes in skeletal muscle composition. However, the main focus and contribution of our work has been to provide an alternative, simple and efficient approach for this purpose. We are confident that we have achieved this goal and have brought our methodology to a level from which it can be successfully transferred to a large-scale study that allows the effects of diabetes on skeletal muscle composition and the interrelationships between the macromolecular tissue alterations due to diabetes to be investigated.

Label-Free High-Resolution Photothermal Optical Infrared Spectroscopy for Spatiotemporal Chemical Analysis in Fresh, Hydrated Living Tissues and Embryos

Label-free chemical imaging of living and functioning systems is the holy grail of biochemical research. However, existing techniques often require extensive sample preparation to remove interfering molecules such as water, rendering many molecular imaging techniques unsuitable for in situ structural studies. Here, we examined freshly extracted tissue biopsies and living small vertebrates at submicrometer resolution using optical photothermal infrared (O-PTIR) microspectroscopy and demonstrated the following major advances: (1) O-PTIR can be used for submicrometer structural analysis of unprocessed, fully hydrated tissue biopsies extracted from diverse organs, including living brain and lung tissues. (2) O-PTIR imaging can be performed on living organisms, such as salamander embryos, without compromising their further development. (3) Using O-PTIR, we tracked the structural changes of amyloids in functioning brain tissues over time, observing the appearance of newly formed amyloids for the first time. (4) Amyloid structures appeared altered following standard fixation and dehydration procedures. Thus, we demonstrate that O-PTIR enables time-resolved submicrometer in situ investigation of chemical and structural changes in diverse biomolecules in their native conditions, representing a technological breakthrough for in situ molecular imaging of biological samples.

Spectral Features Differentiate Aging-Induced Changes in Parchment-A Combined Approach of UV/VIS, µ-ATR/FTIR and µ-Raman Spectroscopy with Multivariate Data Analysis

From the moment of production, artworks are constantly exposed to changing environmental factors potentially inducing degradation. Therefore, detailed knowledge of natural degradation phenomena is essential for proper damage assessment and preservation. With special focus on written cultural heritage, we present a study on the degradation of sheep parchment employing accelerated aging with light (295-3000 nm) for one month, 30/50/80% relative humidity (RH) and 50 ppm sulfur dioxide with 30/50/80%RH for one week. UV/VIS spectroscopy detected changes in the sample surface appearance, showing browning after light-aging and increased brightness after SO₂-aging. Band deconvolution of ATR/FTIR and Raman spectra and factor analysis of mixed data (FAMD) revealed characteristic changes of the main parchment components. Spectral features for degradation-induced structural changes of collagen and lipids turned out to be different for the employed aging parameters. All aging conditions induced denaturation (of different degrees) indicated by changes in the secondary structure of collagen. Light treatment resulted in the most pronounced changes for collagen fibrils in addition to backbone cleavage and side chain oxidations. Additional increased disorder for lipids was observed. Despite shorter exposure times, SO₂-aging led to a weakening of protein structures induced by transitions of stabilizing disulfide bonds and side chain oxidations.

Characterization of Different Types of Epiretinal Proliferations by Synchrotron Radiation-Based Fourier Transform Infrared Micro-Spectroscopy

Pathological tissue on the surface of the retina that can be of different etiology and pathogenesis can cause changes in the retina that have a direct consequence on vision. Tissues of different etiology and pathogenesis have different morphological structures and also different macromolecule compositions usually characteristic of specific diseases. In this study, we evaluated and compared biochemical differences among samples of three different types of epiretinal proliferations: idiopathic epiretinal membrane (ERMi), membranes in proliferative vitreoretinopathy (PVRm), and proliferative diabetic retinopathy (PDRm). The membranes were analyzed by using synchrotron radiation-based Fourier transform infrared micro-spectroscopy (SR-FTIR). We used the SR-FTIR micro-spectroscopy setup, where measurements were set to achieve a high resolution that was capable of showing clear biochemical spectra in biological tissue. We were able to identify differences between PVRm, PDRm, and ERMi in protein and lipid structure; collagen content and collagen maturity; differences in proteoglycan presence; protein phosphorylation; and DNA expression. Collagen showed the strongest expression in PDRm, lower expression in ERMi, and very low expression in PVRm. We also demonstrated the presence of silicone oil (SO) or polydimethylsiloxane in the structure of PVRm after SO endotamponade. This finding suggests that SO, in addition to its many benefits as an important tool in vitreoretinal surgery, could be involved in PVRm formation.

Effects and Mode of Action of Oleic Acid and Tween 80 on Skin Permeation of Disulfiram

Oral disulfiram (DSF) has been used clinically for alcohol dependence and recently has been found to have antitumor activity. A transdermal delivery system would be useful for maintaining drug concentration and reducing the frequency of administration of DSF for cancer treatment. Penetrating the stratum corneum (SC) barrier is a challenge to the transdermal delivery of DSF. Therefore, we investigated the promoting effects and mechanism of action of the combination of oleic acid (OA) and Tween 80 on the skin permeation of DSF. Hairless mouse skin was exposed to OA and Tween 80, combined in various ratios (1:0, 2:1, 1:1, 1:2, and 0:1). A permeation experiment was performed, and total internal reflection infrared spectroscopic measurements, differential scanning calorimetry, and synchrotron radiation X-ray diffraction measurements were taken of the SC with each applied formulation. The combination of OA and Tween 80 further enhanced the absorption-promoting effect of DSF, compared with individual application. The peak of the CH₂ inverse symmetric stretching vibration near the skin surface temperature was shifted by a high frequency due to the application of OA, and DSF solubility increased in response to Tween 80. We believe that the increased fluidity of the intercellular lipids due to OA and the increased solubility of DSF due to Tween 80 promoted the absorption of DSF. Our study clarifies the detailed mechanism of action of the skin permeation and promoting effect of DSF through the combined use of OA and Tween 80, contributing to the development of a transdermal preparation of DSF.

Will repeated Intense Pulsed Light (IPL) treatment sessions affect facial skin sensitivity? Results of a twelve-Month, prospective, randomized split-face study

BACKGROUND

Despite the widespread use of intense pulsed light (IPL) technology in cosmetic dermatology, the effects of its repeated use on facial skin sensitivity in healthy individuals remains unknown.

METHODS

Seventeen healthy female volunteers were included in the study. We measured objective biophysical parameters of the skin, including transepidermal water loss (TEWL), skin glossiness, thickness and density of the epidermis and dermis, sensory nerve current perception threshold (CPT), and regional blood flow before and after treatment at different time points.

RESULTS

Sixteen volunteers completed a follow-up of 12 months. The treated side of the face showed a decreased TEWL on D1 and D3, which reverted to normal on D7. Epidermal thickness increased and skin glossiness decreased on the treated side on D1, but returned to normal on D3. We found no statistically significant differences in CPT values or in regional blood flow volume and velocity, with the exception of D1, which exhibited a higher regional blood flow volume on the treated side.

CONCLUSION

Repeated IPL treatments had no effects on facial skin barrier function, skin nerve sensitivity, or local microcirculation among healthy individuals. IPL is a safe skin care procedure that does not affect skin sensitivity.

Use of ATR-FTIR Spectroscopy and Chemometrics for the Variation of Active Components in Different Harvesting Periods of Lonicera japonica

Lonicera japonica Thunb is a commonly used Chinese herbal medicine, which belongs to the family Caprifoliaceae. The active components varied greatly during bud development. Research on the variation of the main active components is significant for the timely harvesting and quality control of Lonicera japonica. In this study, the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) combined with the chemometric method was performed to investigate the variability of different harvesting periods of Lonicera japonica. The preliminary characterization from ATR-FTIR fingerprints showed various characteristic absorption peaks of the main active components from the different harvesting times, such as flavonoids, organic acids, iridoids, and volatile oils. Additionally, principal component analysis (PCA) scatter plots showed that there was a clear clustering trend in the samples of the same harvesting period, and the samples of the different harvesting periods could be well distinguished. Finally, further analysis by the orthogonal partial least-squares discriminant analysis (OPLS-DA) showed that there were regular changes in flavonoids, phenolic acids, iridoids, and volatile oils in different harvesting periods. Therefore, ATR-FTIR, as a novel and convenient analytical method, could be applied to evaluate the quality of Lonicera japonica.

Infrared Spectroscopy in Aqueous Solutions: Capabilities and Challenges

Fourier-transform infrared (FTIR) spectroscopy provides rapid, reliable, quantitative, and qualitative analysis of samples in different aggregation states, i.e., gases, thin films, solids, liquids, etc. However, when analyzing aqueous solutions, particular issues associated with the rather pronounced IR absorption characteristics of water appear to interfere with the solute determination. In this review, Fourier-transform infrared spectroscopic techniques and their analytical capabilities for analyzing aqueous solutions are reviewed, and highlight examples are discussed.

Anti-ageing peptides and proteins for topical applications: a review

Skin ageing is a cumulative result of oxidative stress, predominantly caused by reactive oxygen species (ROS). Respiration, pollutants, toxins, or ultraviolet A (UVA) irradiation produce ROS with 80% of skin damage attributed to UVA irradiation. Anti-ageing peptides and proteins are considered valuable compounds for removing ROS to prevent skin ageing and maintenance of skin health. In this review, skin ageing theory has been illustrated with a focus on the mechanism and relationship with anti-ageing peptides and proteins. The effects, classification, and transport pathways of anti-ageing peptides and proteins across skin are summarized and discussed. Over the last decade, several novel formulations and advanced strategies have been developed to overcome the challenges in the dermal delivery of proteins and peptides for skin ageing. This article also provides an in-depth review of the latest advancements in the dermal delivery of anti-ageing proteins and peptides. Based on these studies, this review prospected several semi-solid dosage forms to achieve topical applicability for anti-ageing peptides and proteins.

Development and evaluation of the effect of ethanol and surfactant in vesicular carriers on Lamivudine permeation through the skin

The skin embodies a relatively large and readily accessible surface area to absorb a drug through a non-invasive procedure. The vesicular carrier systems such as liposomes, ethosomes, and transethosomes have been explored as non-invasive systems for transdermal delivery of drugs. In the present study, different vesicular carriers were prepared by the thin-film hydration method with modification, and various parameters like size, elasticity, and release profiles were evaluated. Ethosomes and transethosomes have shown the smaller size of 362.21 ± 55.76 and 314.34 ± 41.21 nm, with deformity of 19.34% and 25.04%, respectively, compared with liposomes. The FTIR study of the skin before and after the application of vesicular formulation was performed. The ethosomes and transethosomes changed the orthorhombic phase to the liquid crystalline phase to move the vesicular carrier with the drug to cross the stratum corneum (SC) of the skin. The thermotropic behaviour of drug and vesicular carrier ingredients was studied using differential scanning calorimetry (DSC). Fluorescence images of vesicular-skin permeation have revealed that ethosome and transethosome formulation have shown deeper penetration across the SC and epidermis. The in vitro drug release from the ethosomes and transethosomes has shown 93.34 ± 1.23% and 95.45 ± 2.67% of drug release using Franz diffusion cell and porcine skin as a membrane. The nanostructured flexible vesicular carrier containing ethanol alone and a combination of ethanol and edge activator is a perfect carrier for drug penetration to the deeper skin layer and maintaining the sustained release of drug for a prolonged time.

Analysis of Saliva Lipids in Breast and Prostate Cancer by IR Spectroscopy

We have developed a method for studying the lipid profile of saliva, combining preliminary extraction and IR spectroscopic detection. The case-control study involved patients with a histologically verified diagnosis of breast and prostate cancer and healthy volunteers. The comparison group included patients with non-malignant pathologies of the breast (fibroadenomas) and prostate gland (prostatic intraepithelial neoplasia). Saliva was used as a material for biochemical studies. It has been shown that the lipid profile of saliva depends on gender, and for males it also depends on the age group. In cancer pathologies, the lipid profile changes significantly and also depends on gender and age characteristics. The ratio of 1458/1396 cm-1 for both breast and prostate cancer has a potential diagnostic value. In both cases, this ratio decreases compared to healthy controls. For prostate cancer, the ratio of 2923/2957 cm-1 is also potentially informative, which grows against the background of prostate pathologies. It is noted that, in all cases, changes in the proposed ratios are more pronounced in the early stages of diseases, which increases the relevance of their study in biomedical applications.

Synchrotron-based FTIR microspectroscopy of protein aggregation and lipids peroxidation changes in human cataractous lens epithelial cells

Cataract is the leading cause of blindness worldwide but the mechanisms involved in the process of cataractogenesis are not yet fully understood. Two most prevalent types of age-related cataracts are nuclear (N) and cortical (C) cataracts. A common environmental factor in most age-related cataracts is believed to be oxidative stress. The lens epithelium, the first physical and biological barrier in the lens, is build from lens epithelial cells (LECs). LECs are important for the maintenance of lens transparency as they control energy production, antioxidative mechanisms and biochemical transport for the whole lens. The purpose of this study is to characterize compounds in LECs originated from N and C cataracts, by using the synchrotron radiation-based Fourier Transform Infrared (SR-FTIR) microspectroscopy, in order to understand the functional importance of their different bio-macromolecules in cataractogenesis. We used the SR-FTIR microspectroscopy setup installed on the beamline MIRAS at the Spanish synchrotron light source ALBA, where measurements were set to achieve single cell resolution, with high spectral stability and high photon flux. The results showed that protein aggregation in form of fibrils was notably pronounced in LECs of N cataracts, while oxidative stress and the lipids peroxidation were more pronounced in LECs of C cataracts.

Effect of elevated temperature and UV radiation on molecular structure of linoleic acid by ATR-IR and two-dimensional correlation spectroscopy

The effect of elevated temperature (44 °C) and ultraviolet (UV) radiation on molecular structure of linoleic acid (LA) was studied by Attenuated Total Reflection Infrared (ATR-IR) spectroscopy. To obtain more detailed information on molecular mechanism of these changes we applied moving-window analysis and two-dimensional correlation spectroscopy (2DCOS). Analysis of the time-dependent ATR-IR spectra of LA before and after UV irradiation revealed the structural changes in molecules of LA. The extent of these changes was significantly higher after an application of UV radiation. During 24 h experiment temperature was constant, therefore the spectral changes result from relatively slow processes (and requiring more energy), e.g. cis/trans isomerization, disruption of the C=C double bonds and partial breaking of hydrogen bonds in the cyclic dimers. As a side effect of these structural changes one can observe variations in the orientation of the chains. It is of note that the methyl and methylene groups reveal slightly different behaviour.

Polyoliposomes: novel polyol-modified lipidic nanovesicles for dermal and transdermal delivery of drugs

Various lipid nanovesicular systems have been developed with the aim to enhance the delivery of drugs via transdermal route. However, their clinical applications are often limited due to the barrier nature of skin and lack of flexibility. Herein, we have modified the conventional nanoliposomes (CLs) prepared by a thin-film hydration method by the addition of a polyol (glycerol) to form novel lipid nanovesicular structures termed 'POLYOLIPOSOMES' (PLs). They were further named as PL-B (before film formation) and PL-A (after film formation), depending on the stage of glycerol addition during production. Optimized CLs, PL-B and PL-A showed spherical nanovesicles and hydrodynamic diameter of 181.3 ± 4.11 nm, 114.2 ± 7.21 nm and 170.2 ± 6.51 nm, respectively. PLs showed significantly higher % entrapment efficiency and deformability index in comparison to CLs, indicating their higher flexibility. Furthermore, DSC and attenuated total relection (ATR)-Fourier transform infrared (FTIR) studies revealed the intercalation of glycerol into the lipid bilayer of PLs and interaction between nanovesicles and skin. Moreover, ex vivo and in vivo skin permeation studies confirmed the enhanced drug delivery of PLs via the transdermal route. Taken together, these results illustrate the potential of PLs as a novel lipid nanovesicular system for drug delivery via the transdermal route for both systematic (PL-B) as well as cutaneous diseases (PL-A).

Impact of physiologically relevant temperatures on dermal absorption of active substances - an ex-vivo study in human skin

Skin temperature plays a certain role in the dermal absorption of substances, but the extent and mechanisms of skin temperatures-induced modulation in ranges caused by physiological thermoregulation or environmental conditions are largely unknown. The influence of dermal temperature on the absorption of the model lipophilic compound (anisole) and the model hydrophilic compounds (1,4-dioxane, ethanol) through human skin was investigated at three dermal temperatures (25, 32 and 39 °C) in an ex-vivo diffusion cell model. The substances were applied to the skin and transdermal penetration was monitored. All substances showed temperature dependent variations in their penetration behavior (3 h: 25-39 °C: 202-275% increase in cumulative, transdermally penetrated amounts). The relative differences in absorption in relation to temperature were greatest within 45 min after exposure (25-39 °C: 347-653% rise in cumulated penetration), although absolute amounts absorbed were small (45 min vs. 3 h: 4.5-14.5%). Regardless of blood circulation, skin temperature significantly influences the amount and kinetics of dermal absorption. Substance-dependent, temperature-related changes of the lipid layer order or the porous pathway may facilitate penetration. The early-stage modulation of transdermal penetration indicates transappendageal absorption, which may be relevant for short-term exposures. For both, toxicological evaluation and perfusion cell studies, it is important to consider the thermal influence on absorption or to perform the latter at a standardized temperature (32±1 °C).

Nanoscale investigation of human skin and study of skin penetration of Janus nanoparticles

Janus nanoparticles (JNP) are innovative nanocarriers with an interesting pharmaceutical and cosmetic potential. They are characterized by the presence of a lipid compartment associated with an aqueous compartment delimited by a phospholipid bilayer containing phospholipids and non-ionic surfactants. The hydrodynamic diameter of JNP varies between 150 and 300 nm. The purpose of this study was to answer the following questions: after cutaneous application, are JNP penetrating? If so, how deep? And in which state, intact or degraded? It was essential to understand these phenomena in order to control the rate and kinetics of diffusion of active ingredients, which can be encapsulated in this vehicle for pharmaceutical or cosmetic purposes. An innovative technique called AFM-IR, was used to elucidate the behavior of JNP after cutaneous application. This instrument, coupling atomic force microscopy and IR spectroscopy, allowing to perform chemical analysis at the nanometer scale thanks to local absorption measurements. The identification of organic molecules at the nanoscale is possible without any labelling. Before cutaneous application of JNP, the nano-structure of untreated human skin was investigated with AFM-IR. Then, in vitro human skin penetration of JNP was studied using Franz cells, and AFM-IR allowed us to perform ultra-local information investigations.

Biomolecular and bioanalytical applications of infrared spectroscopy - A review

Infrared (IR; or mid-infrared, MIR; 4000-400 cm^-1; 2500-25,000 nm) spectroscopy has become one of the most powerful and versatile tools at the disposal of modern bioscience. Because of its high molecular specificity, applicability to wide variety of samples, rapid measurement and non-invasivity, IR spectroscopy forms a potent approach to elucidate qualitative and quantitative information from various kinds of biological material. For these reasons, it became an established bioanalytical technique with diverse applications. This work aims to be a comprehensive and critical review of the recent accomplishments in the field of biomolecular and bioanalytical IR spectroscopy. That progress is presented on a wider background, with fundamental characteristics, the basic principles of the technique outlined, and its scientific capability directly compared with other methods being used in similar fields (e.g. near-infrared, Raman, fluorescence). The article aims to present a complete examination of the topic, as it touches the background phenomena, instrumentation, spectra processing and data analytical methods, spectra interpretation and related information. To suit this goal, the article includes a tutorial information essential to obtain a thorough perspective of bio-related applications of the reviewed methodologies. The importance of the fundamental factors to the final performance and applicability of IR spectroscopy in various areas of bioscience is explained. This information is interpreted in critical way, with aim to gain deep understanding why IR spectroscopy finds extraordinarily intensive use in this remarkably diverse and dynamic field of research and utility. The major focus is placed on the diversity of the applications in which IR biospectroscopy has been established so far and those onto which it is expanding nowadays. This includes qualitative and quantitative analytical spectroscopy, spectral imaging, medical diagnosis, monitoring of biophysical processes, and studies of physicochemical properties and dynamics of biomolecules. The application potential of IR spectroscopy in light of the current accomplishments and the future prospects is critically evaluated and its significance in the progress of bioscience is comprehensively presented.

Precursors to non-invasive clinical dengue screening: Multivariate signature analysis of in-vivo diffuse skin reflectance spectroscopy on febrile patients in Malaysia

Dengue diagnostics have come a long way. Attempts at breaking away from lab-oriented dengue detection, such as NS1 antigen, IgM or IgG antibodies detection have extensively received numerous coverage. As a result, rapid detection tests (RDTs) have started to gain inroads in medical practice. Rapid detection tests notwithstanding, analysis of blood serum is still a relatively complicated task. This includes the necessity of phlebotomy, centrifugation for blood serum, and other reagent-based tests. Therefore, a non-invasive method of dengue detection was considered. In this study, we present the utility of diffuse reflectance skin spectroscopy (bandwidth of 200-2500nm) on the forearm during the triaging period for dengue screening potential. This is performed with multivariate analysis of 240 triaged febrile/suspected dengue patients. The data is then scrutinized for its clinical validity to be included as either confirmed or probable dengue, or a control group. Based on discriminant analysis of several data normalization models, we can predict the patients' clinical dengue-positivity at ranges of accuracy between ~93-98% depending on mode of the data, with a probably optimal sensitivity and specificity to the clinical diagnosis of ~89% and ~100% respectively. From the outcomes of this study, we recommend further trials with cautious optimism. With these findings, it is hoped that the elusive non-invasive detection of tropical diseases may gain platform in the near future.

An in vitro Raman study on compositional correlations of lipids and protein with animal tissue hydration

Raman spectroscopy is a powerful non-invasive tool for detection and classification of chemical composition of materials including biological tissues. In this work, we report an in vitro Raman study on animal skin samples with a focus on high-frequency vibrations such as symmetric CH₃ stretching mode at 2934 cm^-1, and the symmetric CH₂ vibration mode at 2854 cm^-1, OH stretching modes near 3412 cm^-1, and bounded OH mode near 3284 cm^-1. Raman data was acquired with a customized InGaAs based Raman spectrometer that consolidates the NIR (866 nm) light and the InGaAs detector and is particularly suitable for probing high-frequency vibrations. The Raman spectra of fat, tendon, and muscle tissues are also analyzed to determine the spectroscopic identities of CH and OH groups in skin. Our results suggest that the protein is beneficial for the maintenance of skin hydration, as it has higher water capacity and greater capability to retain water than lipids. This conclusion is consistent with the additional discovery that water exists in fat mainly as unbound type, while part of water exists as bound type in muscle.

Mannosylerythritol Lipid B Enhances the Skin Permeability of the Water-Soluble Compound Calcein via OH Stretching Vibration Changes

We confirmed that mannosylerythritol lipid B (MEL-B), a biosurfactant, enhances the skin permeability of the model water-soluble compound calcein. MEL-B liposomes were prepared by the thin-layer evaporation technique, and then applied to the skin. Although we attempted to adjust the size by extrusion, we could not control the particle diameter of the liposomes. However, the MEL-B liposome particle diameter remained the same over the 7-day study period. We observed an endothermic peak, with 74.7 °C as the transition temperature by differential scanning calorimetry. We also performed a fusion experiment with a fluorescence resonance energy transfer. A high amount of fusion of intercellular lipid liposomes and MEL-B liposomes occurred in a short period of time. After applying the MEL-B liposomes containing calcein to the skin, we measured the degree of calcein permeation and the amount of calcein within the skin. The resulting values were higher than those of an aqueous solution. The results obtained using a confocal laser scanning microscope suggested that calcein had been delivered deeply into the skin. Using the attenuation of total reflectance Fourier-transform infrared spectrometry, we observed that the OH stretching vibration had shifted to a higher wavenumber; however, this did not affect the CH stretching vibration. The measurement of transepidermal water loss after four days of continuous application of 1% MEL-B to animals revealed no changes. Our results suggest that MEL-B increases the skin permeability of compounds (calcein) that are difficult to deliver transdermally by changing the OH stretching vibration, which shifts to a higher wavenumber.

Burn-related Collagen Conformational Changes in ex vivo Porcine Skin using Raman Spectroscopy

This study utilizes Raman spectroscopy to analyze the burn-induced collagen conformational changes in ex vivo porcine skin tissue. Raman spectra of wavenumbers 500-2000 cm^-1 were measured for unburnt skin as well as four different burn conditions: (i) 200 °F for 10 s, (ii) 200 °F for the 30 s, (iii) 450 °F for 10 s and (iv) 450 °F for 30 s. The overall spectra reveal that protein and amino acids-related bands have manifested structural changes including the destruction of protein-related functional groups, and transformation from α-helical to disordered structures which are correlated with increasing burn severity. The deconvolution of the amide I region (1580-1720 cm^-1) and the analysis of the sub-bands reveal a change of the secondary structure of the collagen from the α-like helix dominated to the β-aggregate dominated one. Such conformational changes may explain the softening of mechanical response in burnt tissues reported in the literature.

Effect of propylene glycol on the skin penetration of drugs

Propylene glycol (PG) has been used in formulations as a co-solvent and/or to enhance drug permeation through the skin from topical preparations. Two skin in vitro permeation approaches are used to determine the effect of PG on drug penetration. The in vitro Skin-PAMPA was performed using 24 actives applied in aqueous buffer or PG. PG modulates permeability by increasing or diminishing it in the compounds with poor or high permeability, respectively. Percutaneous absorption using pigskin on Franz diffusion cells was performed on seven actives and their commercial formulations. The commercial formulations evaluated tend to have a lower permeability than their corresponding PG solutions but maintain the compound distribution in the different strata: stratum corneum, epidermis and dermis. The results indicate the enhancer properties of PG for all compounds, especially for the hydrophilic ones. Additionally, the Synchrotron-Based Fourier Transform Infrared microspectroscopy technique is applied to study the penetration of PG and the molecular changes that the vehicle may promote in the different skin layers. Results showed an increase of the areas under the curve indicating the higher amount of lipids in the deeper layers and altering the lipidic order of the bilayer structure to a more disordered lipid structure.

Classification of aggressive and classic mantle cell lymphomas using synchrotron Fourier Transform Infrared microspectroscopy

Mantle cell lymphoma (MCL) is regarded as an incurable neoplasm, even to the novel drug strategies. It is known MCL has two morphological variants- classic and aggressive. Aggressive MCL is characterized by a higher mitotic index and proliferation rate, and poor overall survival in comparison to classic subtype. The insight into the detailed biochemical composition of MCL is crucial in the further development of diagnostic and treatment guidelines for MCL patients; therefore Synchrotron radiation Fourier Transform Infrared (S-FTIR) microspectroscopy combined with Principal Component Analysis (PCA) was used. The major spectral differences were observed in proteins and nucleic acids content, revealing a classification scheme of classic and aggressive MCLs. The results obtained suggest that FTIR microspectroscopy has reflected the histopathological discrimination of both MCL subtypes.

The consequences of overcoming the human skin barrier by siloxanes (silicones) Part 1. Penetration and permeation depth study of cyclic methyl siloxanes

Dynamic production of cyclic siloxanes: octamethylcyclotetrasiloxane D4, decamethylcyclopentasiloxane D5 and dodecamethylcyclohexasiloxane D6 increases their concentrations in environment. It is considered that both environmental pollution and the usage of personal care products and cosmetics containing cyclic siloxanes can be the main source of the human exposure by transdermal route. The aim of the study was to verify the possibility to overcome the skin barrier by cyclic siloxanes (ATR-FTIR and GC-FID), evaluation of diffusion pathway to stratum corneum SC (Fluorescence microscopy), and determination of depth of permeation to deeper skin layers: epidermis and dermis (ATR-FTIR) and also of potential interaction with SC lipids and proteins (Fluorescence microscopy, ATR-FTIR) and the cytotoxicity studies against HaCaT cells (MTT test). The results show that D4, D5 and D5 can penetrate to SC and permeate into the deeper layers of the skin: epidermis and dermis. The quantitative analysis (GC-FID) showed that total cumulative doses for D4, D5 and D6 were: 42.50; 95.37 and 77.19 μg/cm2/24 h, respectively. The microscopic analysis proved, transepidermal route through the lipid matrix as well as through the canyons (intercluster spaces) were a diffusion pathway to the SC as well as disruption of human SC lipid structure by: D4 (the most), D5 and D6 (the least). The cytotoxicity studies demonstrated that the tested range of concentrations of D5 and D6 (up to 300 mM, 111 300 mg and 133 500 mg respectively) did not impaired the HaCaT growth, while D4 had IC50 value of 40 098 mM ± 7.94 (10 906 ± 872,5 mg).

ATR-FTIR Characterization of Janus Nanoparticles-Part II: Follow-Up Skin Application

Attenuated total reflection by Fourier transform infrared (ATR-FTIR) was used to implement reliable infrared descriptors over time of Janus nanoparticles (JNP), to follow their behavior before and after cutaneous application. In the last study, ATR-FTIR spectroscopic analysis allowed us to identify the evolution of intensity ratio of ν(C=O) at 1739 cm^-1 and δ(H-O-H) at 1639 cm^-1 as a spectroscopic descriptor, for JNP before cutaneous application (on the CaF₂ window). This descriptor can be used to follow the physical stability (presence) of nanoparticles over time. The purpose of this study was to understand the behavior of JNP on the surface of the human skin. Therefore, a comparative study with the untreated skin and the skin after cutaneous application of lipophilic phase (Labrafil) of JNP was conducted using Franz cells. The suitability of the ATR-FTIR descriptor of JNP was evaluated, and a research of other descriptors was performed to understand the interaction that may exist between nanoparticles and the skin.

ATR-IR study of skin components: Lipids, proteins and water. Part II: Near infrared radiation effect

Near infrared (NIR) radiation has been widely used in medicine and biomedical engineering. In spite of numerous studies the molecular mechanism of NIR radiation on biological systems has not been established as yet. The objective of this work was examination of the effect of NIR irradiation on the skin components. Modifications of lipid organization after NIR exposure vs. temperature (from 20 to 90 °C) have been investigated using Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy. This work is a continuation of our previous studies on the temperature effect on skin components [1]. After NIR exposure a temperature shift of the phase transition from the orthorhombic to hexagonal packing (≈40 °C) has been observed. In contrast, the second phase transition temperature (≈70 °C) is almost invariable. The phase transitions in lipids were correlated with modifications of the structure of water and proteins. To our knowledge, for the first time the temperatures of the phase transitions after NIR exposure were investigated.