Total Reflection Spectroscopy Research Articles

Quantification of Recycled PET in Commercial Bottles by IR Spectroscopy and Chemometrics

A novel approach for the quantification of recycled polyethylene terephthalate (r-PET) in commercial bottles is presented. Fifty-eight bottle samples from several brands and producers containing different percentages of r-PET were purchased from the market. Samples were analyzed by two spectroscopic methods: near-infrared (NIR) spectroscopy and attenuated total reflection (ATR) spectroscopy in the mid-infrared (MIR) region. No chemical pre-treatment was applied before analyses. The spectra were analyzed by partial-least squares (PLS) regression, and two models for NIR and MIR data were computed. Then, a multi-block regression was applied to join the two datasets. All models were validated by cross-validation and by excluding and projecting onto the model the replicated spectra of one sample at a time. Results demonstrated the potential of this approach, especially considering the variability of commercial samples in terms of additives, shape, or thickness of the bottles: for samples close to the centroids of the models (i.e., from 10 to 50% r-PET), the predictions of multi-block method seldom departed from the expected values of ±10%. Only for samples with 0% declared r-PET, the models showed poor prediction abilities.

Experimental evaluation of atmospheric plasma treatment effects on different textures of CFRP composite for aircraft applications

This article examines the impact of Atmospheric Plasma Treatment (APL) on the chemical composition and fracture properties of various textured surfaces (tool and bag side) of carbon fiber/epoxy (CFRP) composites utilized in aircraft applications. For this purpose, parameters of atmospheric plasma (APL) surface treatment were evaluated in comparison to chemical cleaning and peel-ply applications, taking into account its effects on surface properties and adhesive bond strength. A comprehensive variety of surface characterization techniques were utilized to analyze surface modifications, including water and diiodomethane contact angle measurements for assessing surface hydrophilicity, Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR) and X-ray Photoelectron Spectroscopy (XPS) for analyzing chemical composition and functional groups, and Profilometry, Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM) for evaluating surface topography and morphology. Experimental results indicated that the reduction in the contact angle following plasma treatment correlated with the elevated oxygen concentration and the presence of polar functional groups (e.g. -OH, -NH2, -NH3, C=O, O-C=O) on the composite surface. Plasma treatment, especially at low nozzle speeds, increased surface roughness on the bag side surfaces. This prevented adhesive penetration and led to gas entrapment, resulting in adhesive failure mode and reduced single lap shear strength for the bag side. In contrast, on the tool side surfaces, the plasma treatment led to a remarkable 19.7% enhancement in shear strength, highlighting its effectiveness.

Laser-irradiating infrared attenuated total reflection spectroscopy of articular cartilage: Potential and challenges for diagnosing osteoarthritis

ObjectiveA prototype infrared attenuated total reflection (IR-ATR) laser spectroscopic system designed for in vivo classification of human cartilage tissue according to its histological health status during arthroscopic surgery is presented. Prior to real-world in vivo applications, this so-called osteoarthritis (OA) scanner has been tested at in vitro conditions revealing the challenges associated with complex sample matrices and the accordingly obtained sparse spectral datasets. MethodsIn vitro studies on human knee cartilage samples at different contact pressures (i.e., 0.2–0.5 ​MPa) allowed recording cartilage degeneration characteristic IR signatures comparable to in vivo conditions with high temporal resolution. Afterwards, the cartilage samples were assessed based on the clinically acknowledged osteoarthritis cartilage histopathology assessment (OARSI) system and correlated with the obtained sparse IR data. ResultsAmide and carbohydrate signal behavior was observed to be almost identical between the obtained sparse IR data and previously measured FTIR data used for sparse partial least squares discriminant analysis (SPLSDA) to identify the spectral regions relevant to cartilage condition. Contact pressures between 0.3 and 0.4 ​MPa seem to provide the best sparse IR spectra for cylindrical (d ​= ​3 ​mm) probe tips. ConclusionLaser-irradiating IR-ATR spectroscopy is a promising analytical technique for future arthroscopic applications to differentiate healthy and osteoarthritic cartilage tissue. However, this study also revealed that the flexible connection between the laser-based analyzer and the arthroscopic ATR-probe via IR-transparent fiberoptic cables may affect the robustness of the obtained IR data and requires further improvements.

Prediction of Deoxynivalenol Contamination in Wheat via Infrared Attenuated Total Reflection Spectroscopy and Multivariate Data Analysis.

The climate crisis further exacerbates the challenges for food production. For instance, the increasingly unpredictable growth of fungal species in the field can lead to an unprecedented high prevalence of several mycotoxins, including the most important toxic secondary metabolite produced by Fusarium spp., i.e., deoxynivalenol (DON). The presence of DON in crops may cause health problems in the population and livestock. Hence, there is a demand for advanced strategies facilitating the detection of DON contamination in cereal-based products. To address this need, we introduce infrared attenuated total reflection (IR-ATR) spectroscopy combined with advanced data modeling routines and optimized sample preparation protocols. In this study, we address the limited exploration of wheat commodities to date via IR-ATR spectroscopy. The focus of this study was optimizing the extraction protocol for wheat by testing various solvents aligned with a greener and more sustainable analytical approach. The employed chemometric method, i.e., sparse partial least-squares discriminant analysis, not only facilitated establishing robust classification models capable of discriminating between high vs low DON-contaminated samples adhering to the EU regulatory limit of 1250 μg/kg but also provided valuable insights into the relevant parameters shaping these models.

Enhancing biological properties with straightforward deposition of durable heparin/chitosan surface coatings on wettable poly(ε-caprolactone)/Tween-20 electrospun fibers

Poly(ε-caprolactone) (PCL) is a hydrophobic aliphatic polyester commonly used as a biomaterial due to its cytocompatibility and biodegradability. However, PCL-based materials are hydrophobic and susceptible to bacterial adhesion and proliferation. To address these disadvantages, this study proposes a direct and practical method for functionalizing the surface and enhancing the biological properties of electrospun PCL fibers using Tween-20 surfactant, followed by the deposition of polyelectrolyte multilayers (PEMs). Tween-20, a neutral and cytocompatible surfactant, was directly incorporated into the fibers without prior surface modifications. The surfactant significantly increased the wettability of the PCL fibers, resulting in water contact angles of 0 degrees, facilitating subsequent functionalization with heparin and chitosan PEMs (with 10, 20, and 30 layers). The materials were characterized through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), water contact angle and mechanical measurements, Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The PEMs remain stable on the fiber surfaces for up to 14 days in a buffer at 37°C. The samples supported high cell viability with no observed cytotoxicity toward human adipose-derived stem cells and no hemolytic activity toward human red blood cells. Antibacterial assays (live/dead and proliferation tests) demonstrated that the coated PCL fibers inhibited the proliferation of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). The PEM coatings significantly enhanced the antimicrobial activity, resulting in a high number of damaged and dead bacterial cells attached to the coated fibers. Therefore, the heparin/chitosan PEMs on Tween-20-modified PCL fibers can prevent bacterial infections while supporting viable mammalian cells.

Lignocellulosic Membranes Grafted with N-Vinylcaprolactam Using Radiation Chemistry: Load and Release Capacity of Vancomycin.

Radiation chemistry presents a unique avenue for developing innovative polymeric materials with desirable properties, eliminating the need for chemical initiators, which can be potentially detrimental, especially in sensitive sectors like medicine. In this investigation, we employed a radiation-induced graft polymerization process with N-vinylcaprolactam (NVCL) to modify lignocellulosic membranes derived from Agave salmiana, commonly known as maguey. The membranes underwent thorough characterization employing diverse techniques, including contact angle measurement, degree of swelling, scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), nuclear magnetic resonance (CP-MAS 13C-NMR), X-ray photoelectron spectroscopy (XPS), and uniaxial tensile mechanical tests. The membranes' ability to load and release an antimicrobial glycopeptide drug was assessed, revealing significant enhancements in both drug loading and sustained release. The grafting of PNVCL contributed to prolonged sustained release by decreasing the drug release rate at temperatures above the LCST. The release profiles were analyzed using the Higuchi, Peppas-Sahlin, and Korsmeyer-Peppas models, suggesting a Fickian transport mechanism as indicated by the Korsmeyer-Peppas model.

RAPID DETECTION OF RAT MEAT ADULTERATION IN BEEF SAUSAGES USING FTIR‑ATR SPECTROSCOPY AND CHEMOMETRICS FOR HALAL AUTHENTICATION

Objective: The objective of this study was to employ Fourier Transform Infrared-Attenuated Total Reflectance (FTIR‑ATR) spectroscopy in combination with chemometrics for the analysis of rat meat adulteration in beef sausages.
 Methods: Lipid components in sausages were extracted using three extraction methods, namely Bligh and Dyer, Folch, and Soxhlet methods. The lipid components extracted were then analysed using FTIR‑ATR spectroscopy, and their spectra obtained were used as variables during chemometrics modeling. Samples were prepared by mixing beef with adulterant of rat meat in the concentration range of 0-100% of rat meat. Each sample was scanned using FTIR-Attenuated Total Reflectance (ATR) spectroscopy in three replicates at 4000-650 cm-1 wavenumber region.
 Results: The absorbance values at wavenumbers regions of 3100-700 cm-1 were used to discriminate lipid components extracted by the Bligh Dyer, Folch, and Soxhlet Method with an accuracy level of 100%. The prediction of rat sausages was successfully determined using multivariate calibrations of Partial Least Square (PLS) and Principle Component Regression (PCR) using optimised conditions.
 Conclusion: FTIR-ATR spectroscopy coupled with chemometrics is a rapid and accurate method for detecting and quantifying rat meat in beef sausages for halal authentication.

ATR-FTIR spectroscopy and LDA: a rapid, non-destructive and cost effective strategy to trace the geographical origin of Cannabis sativa L

Abstract Cannabis recreational and/or medicinal use have been legalized in the past years in many states and countries. As a consequence, many Cannabis growers and product developers have emerged in a new market throughout the world; at the same time, issues regarding questionable quality control have also risen, as several reports on Cannabis users’ health-related problems caused by inaccurate labeling content in Cannabis-based medicines, edibles or other derivatives are being published and brought out to the public’s attention. These facts make traceability methodologies crucial whether for forensic use, such as drug trafficking eradication, or for quality control purposes of legal Cannabis and of products derived from it. Hence, the objective of this study was to analyze Cannabis by means of Attenuated Total Reflection Spectroscopy (ATR-FTIR) in order to assess the capability of this technique to trace the geographical origin of Cannabis cultivated in Brazil and in Colorado, United States of America. Forty-seven samples from Brazil and 18 samples from Colorado were analyzed by ATR-FTIR. Linear Discriminant Analysis (LDA) was employed to source the samples. The combination of ATR-FTIR and LDA achieved up to 95.23% accuracy in assigning Cannabis samples to their geographical locations of origin in Brazil and up to 100% in Colorado.

Detection and estimation of adulterated gasoline fuel in India using FTIR-ATR spectroscopy with chemometric methods

In this work, Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) spectroscopy was combined with multivariate techniques, such as Principal Component Analysis (PCA), Soft Independent Modelling of Class Analogy (SIMCA), and Partial Least Squares Discriminant Analysis (PLS-DA), to classify and quantify the gasoline adulteration with kerosene. The Calibration models of Kerosene blended on gasoline fuel of 12 standard samples (2–24% v/v) were prepared. The chemometric tools were used to compare 142 samples from Mizoram and 12 samples from neighbouring states. The PCA and SIMCA approaches did not detect adulteration. The PLS-DA classification model found 7 samples were adulterated, with excellent specificity and sensitivity. The PLS regression model had the ability to predict adulterant concentrations with prediction errors less than 2% for all adulterants. The predicted concentration range of the PLS-R model is 0.3–13 % v/v, with high significant values of R-Square (0.996) and RMSE (0.405).

In situ Fourier transform infrared-attenuated total reflection spectroscopy and modeling investigation of protein adsorption: Case of expanded bovine serum albumin on titanium dioxide anatase.

The purpose of this experimental and modeling research is to study the pH effect and to determine the surface coverage plus the adsorption constant (Ka) of bovine serum albumin (BSA) protein adsorbed on TiO2 anatase surface, respectively. In situ Fourier transform infrared-attenuated total reflection spectroscopy in a flow-through cell was used to study the BSA adsorption on porous TiO2 anatase films. The experiments were performed in water solution, under different pH values, at a concentration of 10-6 mol/l. Theoretically, we extended the two-state model, based on a system of coupled differential equations, by adding a desorption parameter Kd2, for unfolded state. The model was solved taking into account the adsorption (Ka), desorption (Kd1,2), transformation (Kf) coefficients, and the initial solution protein concentration (C0). The findings clearly illustrated that the solution pH drastically changed the behavior of BSA adsorption, whereas the mathematical analytical solutions allowed us to determine the native state (θ1), the unfolded state (θ2), and the full one (θ) surface coverages. Finally, a good application of the approximated model on the experimental work, expanded BSA adsorbed on TiO2 anatase at pH = 1.7, indicated a value of Ka = (408.36 ± 0.996) × 102 mol-1 l min-1.

Efficient, fast, simple, and eco-friendly methods for separation of toxic chromium(VI) ions based on ion exchangers and polymer materials impregnated with Cyphos IL 101, Cyphos IL 104, or D2EHPA

In this study, we present the results of the first comparison of the elimination of toxic Cr(VI) ions, which are hazardous contamination of the environment, from aqueous solutions using ion exchangers (IEs) and polymer materials (PMs) impregnated with D2EHPA or ionic liquids (Cyphos IL 101 and Cyphos IL 104). Sorption of Cr(VI) ions and desorption from the formulated sorption materials were carried out. In comparison, classical solvent extraction was accomplished. Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and atomic force microscopy (AFM) have been used for characterization of the structure of developed IEs and PMs. The highest efficiency of adsorption of Cr(VI) ions was obtained using PMs with ionic liquids (>82%). Desorption from these materials were also very efficient (>75%). On the contrary, the application of IEs allowed for obtaining the best results of both, sorption and desorption processes when using D2EHPA (75% and 72%, respectively). The application of PMs and IEs is part of the green chemistry, and the conducted elimination of chromium(VI) ions using developed materials allows for the conclusion that they can potentially be used on a larger scale, e.g., for the treatment of industrial wastewater rich in Cr(VI) ions.

Preparation of Co–CaCO3 catalysts for improved hydrogen production from sodium borohydride

Ca1-xCoxCO3 nanoparticle catalysts (x = 0.0, 0.1, 0.2 and 0.3 %) were prepared by the sol-gel method. The samples were characterized using various techniques such as X-ray diffraction (XRD), attenuated total reflectance spectroscopy (ATR), environmental scanning electron microscopy (ESEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analysis. The XRD peaks of Ca1-xCoxCO3 displayed a significant level of conformity with the rhombohedral calcite structure. The average crystal size of Ca1-xCoxCO3 nanoparticles was found to be 14 nm. The ESEM micrographs of Ca1-xCoxCO3 showed rhombic calcite shapes. The most prominent peaks in the XPS spectra of Ca1-xCoxCO3 are the Ca 2p, C 1s, Co 2p and O 1s peaks. The sample Ca1-xCoxCO3 has the highest surface area (58.27 m2/g) and large pore size (20.25 Å). The rates of hydrogen production for CaCO3, Ca0.9Co0.1CO3, Ca0.8Co0.2CO3 and Ca0.7Co0.3CO3 were 5204, 4381, 6666 and 6136 mL/g.min. The Ca0.8Co0.2CO3 catalyst revealed an activation energy for hydrogen catalytic reaction of 34.56 kJ/mol. The recyclability tests of Ca1-xCoxCO3 catalysts showed a reduction of efficiency by 7 % over 5 reaction cycles. Accordingly, the prepared Ca1-xCoxCO3 catalysts are promising for improved hydrogen production systems. This research contributes to advancements in hydrogen production technology.

Quick response‐encoded chip engraved onto multifunctional aspirin loaded enteric films by fused filament fabrication‐3D printing

AbstractDigital fabrication technology revolutionizing the pharmaceutical industry, offering patient‐centric personalized medicine with tailored pharmacotherapy. In this study, we demonstrated fused filament fabrication coupled with hot melt extrusion for the fabrication of aspirin (ASP) loaded enteric film engraved onto QR‐encoded polylactic acid films for enteric intestinal specific ASP delivery. Further, QR‐encoded films (QRFs) were formulated and its physicochemical properties were assessed systematically. All the QRFs were scannable and readable. Interestingly, due to the advantage of the plasticizing effect of ASP, the formulation was optimized with drug and polymer ratio excluding the usage of any filler and plasticizers. The compatibility study was assessed by attenuated total reflectance and Raman spectroscopy. The physicochemical evaluation was further performed by scanning electron microscopy, x‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Gastric resistance was assessed via performing dissolution study at gastric pH for 4 h, with a lag phase followed by radical increase in an alkaline for next 8 h. Korsmeyer–Peppas model was found to be the best‐fit mathematical kinetic model (R2 > 0.9475 and n = 0.514). This type of QRFs can help the tailoring doses and patients can know the details of the drug that has to be taken.

Expanding the Potential of Self-Assembled Silk Fibroin as Aerogel Particles for Tissue Regeneration.

A newly produced silk fibroin (SF) aerogel particulate system using a supercritical carbon dioxide (scCO2)-assisted drying technology is herein proposed for biomedical applications. Different concentrations of silk fibroin (3%, 5%, and 7% (w/v)) were explored to investigate the potential of this technology to produce size- and porosity-controlled particles. Laser diffraction, helium pycnometry, nitrogen adsorption-desorption analysis and Fourier Transform Infrared with Attenuated Total Reflectance (FTIR-ATR) spectroscopy were performed to characterize the physicochemical properties of the material. The enzymatic degradation profile of the SF aerogel particles was evaluated by immersion in protease XIV solution, and the biological properties by cell viability and cell proliferation assays. The obtained aerogel particles were mesoporous with high and concentration dependent specific surface area (203-326 m2/g). They displayed significant antioxidant activity and sustained degradation in the presence of protease XIV enzyme. The in vitro assessment using human dermal fibroblasts (HDF) confirm the particles' biocompatibility, as well as the enhancement in cell viability and proliferation.

Thermoelectric properties investigation of Tungsten carbide-filled poly (vinyl alcohol)/Polypyrrole ternary composites

ABSTRACT Many researchers have recently focused their attention on conductive polymer-based flexible thermoelectric (TE) materials. One of the most popular approaches for improving TE efficiency is the addition of inorganic components to conductive polymers. In this work, the TE properties of tungsten carbide-filled poly (vinyl alcohol)/polypyrrole (PVA/PPy/WC) ternary composites were examined for the first time. First, composites with varying WC weight ratios were produced by the solvent casting process. Scanning electron microscopy (SEM) investigations demonstrated the homogenous dispersion of WC particles in the composite structure, while X-ray diffraction (XRD) analyses determined the influence of WC addition on the crystal structure of the composite. The electrostatic interactions of each component were revealed by Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR) and UV-vis studies. Additionally, with the addition of WC, the energy bandgap of PVA/PPy reduced from 5.71 eV up to 2.07 eV. From TE studies, it was obtained that the electrical conductivity of PVA/PPy increased from 3.35 × 10−3 up to 58 Sm−1 with the addition of 30% WC, while the power factor (PF) of PVA/PPy increased from 8,6 × 10−9 μWm−1K−2 up to 1.71 × 10−3 μWm−1K−2. Both composite samples had negative Seebeck coefficients, which are typical of n-type conductors.

Influence Analysis of Polyvinyl Alcohol on the Degradation of Artificial Leather with Cellulose Nitrate Coating Originating from a Suitcase Stored in the Collection of the Auschwitz-Birkenau State Museum in Oświęcim, Poland.

The aim of this study was to assess the influence of a protective layer of polyvinyl alcohol on the degradation process of artificial leather based on cellulose nitrate. Samples of the artificial leather were obtained from a suitcase dating back to the first half of the 20th century, not considered a historical artifact. The analysis involved Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Artificial aging was employed for the study. The artificial leather sample with a protective coating of polyvinyl alcohol on a cellulose nitrate base exhibited the lowest degree of degradation due to minimal chemical changes in cellulose esters. The obtained FTIR-ATR spectrum indicated significantly higher nitration of cellulose and, consequently, a lower degree of polymer degradation. The sample without the protective polyvinyl alcohol coating and the sample with the coating removed before artificial aging showed similar reactions.

Thermal Gradient Infrared Spectroscopy for Diffusion in Polymers.

Time-resolved Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR) was used to measure diffusion in opaque and translucent samples. FTIR-ATR was used to measure the change in the absorbance near the heated ATR crystal surface. The infrared absorbance was then related to the concentration through the Beer-Lambert law. The sample used is a polymer electrolyte composed of lithium bis-trifluoromethanesulfonylimide (LiTFSI) salt in a block copolymer polystyrene-poly(ethylene oxide) (SEO). A new approach to introduce concentration gradients is presented using a temperature gradient that creates a small salt concentration gradient due to thermally driven mass diffusion (the Soret effect). This first method was compared to a second method that we reported using two laminated polymer electrolyte films of different salt concentrations. The thermal gradient study (method 1) covered three temperature differences of 10, 15, and 20 °C, while the second study (method 2) used three average molar ratios across isothermal temperatures ranging from 80 to 120 °C. The benefits and limitations of the new approach are reported, as is the activation energy for salt diffusion in this and similar SEO electrolytes. Developing new techniques to measure diffusion coefficients effectively will aid in the development of a variety of devices, including solid-state batteries and thermogalvanic cells, that are able to convert waste heat into electricity and improve the efficiency of power-generating systems. FTIR-ATR overcomes previous limitations in experimental techniques measuring diffusion coefficients. The results prove that thermal gradient FTIR-ATR is an effective and repeatable approach for determining Fickian diffusion coefficients in viscoelastic solids.

Creating Nature-Inspired Surface Roughness and Modifying Surface Chemistry of PVDF Electrospun Fibers Using Low-Pressure Plasma towards Omniphobic Membrane for Long-term Distillation

Today, water scarcity as one of the world's most pressing challenges, has caused many concerns. Seawater desalination based on membrane distillation (MD) has been introduced as an effective solution to deal with this problem. The surface of membranes used in MD is required to be modified to guarantee long-term performance via creating resistance against membrane wetting by low surface tension feeds. In this regard, beetle skin-inspired roughness was created on the surface of poly(vinylidene fluoride) (PVDF) electrospun fibers using low-pressure plasma technique. Synergistically, 1H, 1H, 2H, 2H-perfluorooctyl acrylate (PFOA) was polymerized on the fiber surface to modify its chemistry. In other words, using the plasma polymerization technique, the membrane surface energy was reduced thanks to (1) the increase in membrane surface roughness and (2) the change in the membrane surface chemistry, as confirmed by field-emission scanning electron microscope (FESEM) imaging, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. These changes led to an omniphobic membrane repelling water, engine oil and isopropanol with contact angles of 150°, 135°, and 119°, respectively. The long-term performance of the developed omniphobic membrane was demonstrated by conducting air gap membrane distillation (AGMD) for a duration as long as 600 min using a feed solution containing 3.5 wt% NaCl and 0.6 mM sodium dodecyl sulfate (SDS), which is ten times better than the performance of pristine membrane (60 min). Overall, the surface modification technique considered in this work yields an omniphobic membrane with stable long-term performance without compromising the membrane flux and salt rejection.

Non-Steroidal Anti-Inflammatory Drugs Loaded to Micelles for the Modulation of Their Water Solubility.

The low water solubility of aspirin (ASPH) is well known, creating research challenges regarding both its composition and its delivery. Therefore, the development of new aspirin-based formulations that are water soluble is a research, technological, and financial issue. With the aim to improve the water solubility of ASPH, the micelle of formula SLS@ASPH (SLS = Sodium Lauryl Sulfate) was formed. The Critical Micelle Concentration (CMC) of SLS in the presence of ASPH was determined by ultrasonic velocity, complementary, and transient birefringence measurements. The SLS@ASPH was characterized by the melting point (m.p.), attenuated total reflection spectroscopy (FT-IR-ATR), and X-ray fluorescence spectroscopy (XRF) in a solid state and in a solution by ultraviolet-visible (UV-Vis) and 1H NMR spectroscopies. The SLS/ASPH molar ratio was determined to be 5/1 in SLS@ASPH. The inhibitory activity of SLS@ASPH towards lipoxygenase (LOX), an enzyme that takes part in the inflammation mechanism, was studied. The inhibitory activity of SLS@ASPH against LOX is 3.5-fold stronger than that of free SLS. The in vitro toxicity of the SLS@ASPH was tested on immortalized human keratinocyte (HaCaT) cells.

Rotational Isomerism of the Side Chains of Hydroxypropyl Cellulose in Aqueous Solution Observed Using Attenuated Total Reflectance Infrared Spectroscopy

Etherified cellulose derivatives, in contrast to cellulose, are soluble in water at room temperature and have a wide variety of applications. One of their most important characteristics is their decrease in solubility with temperature. The objective of this work was to study the rotational isomerism of the side chains of hydroxypropyl cellulose (HPC) in aqueous solution as sole solute and in the presence of chloride, sulfate, and barium ions as a function of temperature. Infrared Attenuated Total Reflectance spectroscopy was used to measure changes in the side-chain rotational isomerism using the structurally sensitive methylene wagging region as the probe. Decreases in end-gauche and kink conformers were observed. Principal component analysis revealed the presence of multiple forms of HPC at higher molecular weight. The precipitation of HPC as the temperature was increased was accompanied by a reduction in the numbers of end-gauche and kink conformers.