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Microplastic pollution is increasingly recognised as a global environmental challenge which stems from the rapid growth of the use of petrochemical-derived plastic. As researchers and practitioners face a myriad of environmental challenges, oceanic microplastic pollution has so far dominated interest. However, airborne microplastics present an increasing environmental and public health concern. There is currently a need for research addressing this emerging challenge, and at the same time, the lack of knowledge and consensus regarding airborne microplastics presents an obstacle to action. The purpose of this study is to utilise a participatory Structured Decision-Making (SDM) approach to understand the perspectives of a range of stakeholders involved in the microplastics landscape, and subsequently refine common research priorities and knowledge gaps to advance the field. Through two participatory workshops, we first defined shared objectives of stakeholders and then negotiated best courses of action to achieve these objectives based on discussion between stakeholders and facilitators. The qualitative approach taken has enabled the full, complex and multidisciplinary aspects of the research into airborne microplastic pollution to be considered. Our findings highlight some important potential consequences of airborne microplastic pollution, including impacts on human health, and the need for more interdisciplinary research, and collaborative, integrated approaches in this area. As a result of the first workshop, five fundamental objectives on the theme of airborne microplastics were identified. As a direct consequence of this, participants identified 84 actions split across eight themes, which are outlined later in this paper.

Monoclonal antibodies (mAbs) are used extensively as biotherapeutics for chronic and acute conditions. Production of mAbs is lengthy and expensive, with protein A affinity capture the most costly step, due both to the nature of the resin and its marked reduction in binding capacity with repeated use. Our previous studies using in situ ATR-FTIR spectroscopy indicated that loss in protein A binding capacity is not the result of leaching or degradation of protein A ligand, suggesting fouling is the principal cause. Here we explore binding behavior and resin capacity loss using Raman spectroscopy. Our data reveal a distinct Raman spectral fingerprint for mAb bound to the protein A ligand of MabSelect SuRe. The results show that the drop in static binding capacity (SBC) previously observed for used protein A resin is discernible by Raman spectroscopy in combination with partial least-squares regression. The SBC is lowest (35.76 mg mL-1) for used inlet resin compared to used outlet (40.17 mg mL-1) and unused resin samples (70.35 mg mL-1). Depth profiling by Raman spectroscopy indicates that at below saturating concentrations (∼18 mg mL-1), binding of mAb is not homogeneous through used resin beads with protein binding preferentially to the outer regions of the bead, in contrast to fully homogeneous distribution through unused control MabSelect SuRe resin beads. Analysis of the Raman spectra indicates that one foulant is irreversibly bound mAb. The presence of irreversibly bound mAb and host cell proteins was confirmed by mass spectrometric analysis of used resin beads.

Heat flow generation and manipulation in nanometer-sized solids using light represents one of the up-and-coming tasks in thermonanophotonics. Enhanced light-matter interaction due to plasmon resonance permits metallic nanostructures to absorb light energy efficiently, and it results in extra optical heating. The net temperature increment of nanostructures is directly dependent on heat exchange with a thermostat. However, to the best of our knowledge, precise tailoring of optical heating at a fixed pump power is still of no practical implementation. In this paper, we focus on the tunable optical heating of a plasmonic nanostructure exposed to moderate light intensity (MW cm

Therapeutic monoclonal antibodies (mAbs) are effective treatments for a range of cancers and other serious diseases, however mAb treatments cost on average ∼$100 000 per year per patient, limiting their use. Currently, industry favours Protein A affinity chromatography (PrAc) as the key step in downstream processing of mAbs. This step, although highly efficient, represents a significant mAb production cost. Fouling of the Protein A column and Protein A ligand leaching contribute to the cost of mAb production by shortening the life span of the resin. In this study, we assessed the performance of used PrAc resin recovered from the middle inlet, center and outlet as well as the side inlet of a pilot-scale industrial column. We used a combination of static binding capacity (SBC) analysis and Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy to explore the used resin samples. SBC analysis demonstrated that resin from the inlet of the column had lower binding capacity than resin from the column outlet. ATR-FTIR spectroscopy with PLS (partial least square) analysis confirmed the results obtained from SBC analysis. Importantly, in situ ATR-FTIR spectroscopy also allowed both measurement of the concentration and assessment of the conformational state of the bound Protein A. Our results reveal that PrAc resin degradation after use is dependent on column location and that neither Protein A ligand leaching nor denaturation are responsible for binding capacity loss., A combination of static binding capacity analysis and ATR-FTIR spectroscopy reveals that loss of binding capacity is not uniform through a used Protein A column and is not due to loss of Protein A ligand.

Advances in plasmonics have been fundamentally rooted in minimizing ohmic losses in metallic nanostructures. However, the losses at resonance can play a positive role; for instance, in optical heat...

Inter- and intramolecular interactions in multicomponent polymer systems influence their physical and chemical properties significantly and thus have implications on their synthesis and processing. In the present study, chemical images were obtained by plotting the peak position of a spectral band from the data sets generated using in situ attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopic imaging. This approach was successfully used to visualize changes in intra- and intermolecular interactions in poly(3-hydroxybutyrate)/poly(L-lactic acid) (PHB/PLLA) blends during the isothermal melt crystallization. The peak position of ν(C＝O) band, which reflects the nature of the intermolecular interaction, shows that the intermolecular interactions between PHB and PLLA in the miscible state (1733 cm−1) changes to the inter- and intramolecular interaction (CH3⋯O=C, 1720 cm−1) within PHB crystal during the isothermal melt crystallization. Compared with spectroscopic images obtained by plotting the distribution of absorbance of spectral bands, which reveals the spatial distribution of blend components, the approach of plotting the peak position of a spectral band reflects the spatial distribution of different intra- and intermolecular interactions. With the process of isothermal melt-crystallization, the disappearance of the intermolecular interaction between PHB and PLLA and the appearance of the inter- and intramolecular interactions within the PHB crystal were both visualized through the images based on the observation of the band position. This work shows the potential of using in-situ ATR FT-IR spectroscopic imaging to visualize different types of inter- or intramolecular interactions between polymer molecules or between polymer and other additives in various types of multicomponent polymer systems., Graphical Abstract

Exposing polymers to high-pressure and supercritical CO2 is a useful approach in polymer processing. Consequently, the mechanisms of polymer–polymer interaction under such conditions are worthy of further investigation. Two-dimensional correlation analysis and two-dimensional disrelation mapping were applied to datasets of polycaprolactone –poly(lactic acid) blend with or without high-pressure CO2 obtained using in situ attenuated total reflection Fourier transform spectroscopic imaging. The relatively weak dipole–dipole intermolecular interactions between polymer molecules were visualized through the disrelation maps for the first time. Because of the specially designed polymer interface, the interactions between the same type of polymer molecules and different types of polymer molecules were differentiated. Under exposure to high-pressure CO2, all three types of interactions: interaction between polycaprolactone molecules and poly(lactic acid) molecules, interaction between polycaprolactone molecules and interaction between poly(lactic acid) molecules become weaker than those in the polymer interface without high-pressure CO2. The resulting increase in the Flory interaction parameter is the main cause of phase separation in the PCL–PLA blend under high-pressure CO2. The findings from this study will be of benefit for polymer processing with high-pressure and supercritical CO2.

The detection of phase separation and crystallization in biopolymer blends is an important aspect of biopolymer processing. In this study, attenuated total reflection (ATR)-Fourier transform infrar...

This paper presents the results of study of titanium–magnesium catalysts often used in polymerization processes, by photoluminescence spectroscopy (PL) in combination with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The interaction of dibutyl phthalate (DBP) with MgCl2was studied at DBPadded/Mg = 0–1 (mol/mol). The luminescence spectra with excitation at 278 nm and the excitation spectra for main emission bands were recorded. It was shown that DBP adsorbed on magnesium chloride, both in the form of donor–acceptor complexes (D+A–) and in the form of molecular complexes. At DBPadded/Mg +A–complexes occur predominantly; with an increase in DBPadded/Mg, the fraction of molecular complexes increases. Molecular complexes are destroyed during the treatment of the support by TiCl4. In this case, the structure of magnesium chloride is disordered and new coordination–unsaturated sites are formed. This work is a first attempt to apply PL spectroscopy in combination with DRIFTS spectroscopy to study titanium–magnesium Ziegler–Natta catalysts. The application of PL spectroscopy to such systems made it possible to detect interactions within and between donor molecules, which would be particularly challenging to achieve using other spectroscopic methods. Both spectroscopic methods provided crucial information about the existence of two types of complexes on the sample surface which is important for tuning the synthesis procedure of the titanium–magnesium catalysts for olefin polymerization.

The effects of hydration on the DNA conformation in the colon biopsy tissues at different disease stages, hyperplasia, dysplasia, and cancer, and their subsequent classifications were investigated in this study. FTIR spectroscopic imaging was used to study the tissues while controlling the humidity from 16% RH to 88% RH using saturated salt solutions. A nonuniform uptake of water into the tissue at its maximum hydrated state was observed in the chemical images showing the distribution of the absorbance of the νas OH spectral band. The regions of high absorbance of this band in the tissues overlap with the regions of high absorbance of predominantly the phosphate (1143-1100 cm-1) and lipid (2879-2844 cm-1) bands. Analysis of the second derivative spectra of the hydrated and dehydrated colon tissues further revealed significant peak shifts and changes in absorbance of the spectral bands that correspond to the vibrations of the phosphate group of DNA. These findings showed some disparities when compared to the effect of hydration on the infrared spectra of live cells and pure isolated DNA, possibly due to the presence of DNA mostly in its A-form in the formalin fixed tissues. Coupled with principal component analysis, the spectral biomarkers that differentiate the healthy colon tissues from the diseased tissues were identified to be in the phosphodiester spectral region (1300-1000 cm-1). This differentiation varied under different humidity conditions, with the highest sensitivity of ∼98% found at the dehydrated state of the tissues with random forest supervised classification.

In this study, the novel application of ATR-FTIR spectroscopy and macro ATR-FTIR spectroscopic imaging overcame an analytical challenge in conservation science: the time-resolved, chemical, and spatial investigation of the reaction of inorganic treatments for stone conservation (ammonium oxalate, AmOx; ammonium phosphate, DAP) occurring in water-based solutions. The aim was to (1) assess the composition and localization of reaction products and their phase variation during the reaction in real time and directly in an aqueous environment and (2) investigate the reaction of AmOx and DAP with calcite and the transformations induced to the substrate with a time-resolved approach. The new analytical results showed that for both treatments, the formation of new crystalline phases initiated at the early stages of the reaction. Their composition changed during the treatment and led to more stable phases. The reactivity of the stone substrate to the treatments varied as a function of the stone material features, such as the specific surface area. A clear influence of post-treatment rinsing on the final composition of reaction phases was observed. Above all, our research demonstrates the actual feasibility, practicality, and high potential of an advanced ATR-FTIR spectroscopic approach to investigate the behavior of conservation treatments and provided new analytical tools to address the choices of conservation in pilot worksites. Lastly, this study opens novel analytical perspectives based on the new possible applications of ATR-FTIR spectroscopic imaging in the field of conservation science, materials science, and analytical chemistry.

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements.

Fourier transform infrared (FTIR) spectroscopic imaging of colon biopsy tissues in transmission combined with machine learning for the classification of different stages of colon malignancy was carried out in this study. Two different approaches, an optical and a computational one, were applied for the elimination of the scattering background during the measurements and compared with the results of the machine learning model without correction for the scattering. Several different data processing pathways were implemented in order to obtain a high accuracy of the prediction model. This study demonstrates, for the first time, that C–H stretching and amide I bands are of little to no significance in the classification of the colon malignancy, based on the Gini importance values by random forest (RF). The best prediction outcome is found when supervised RF classification was carried out in the fingerprint region of the spectral data between 1500 and 1000 cm−1 (excluding the contribution of amide I and II bands). An overall prediction accuracy higher than 90% is achieved through the RF. The results also show that dysplastic and hyperplastic tissues are well distinguished. This leads to the insight that the important differences between hyperplastic and dysplastic colon tissues lie within the fingerprint region of FTIR spectra. In this study, computational correction performed better than optical correction, but the findings show that the disease states of colon biopsies can be distinguished effectively without elimination of Mie scattering effect. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00216-019-02069-6) contains supplementary material, which is available to authorized users.

The depth of penetration and effective thickness in ATR-FTIR spectroscopic imaging are dependent on the wavelength and angle of incidence of the incoming light beam. We have demonstrated, for the first time, that variable angle micro ATR-FTIR, which is created via the insertion of circular apertures, is intrinsic at examining embedded components within a prostate tissue specimen. This is done by constructing a 3D model from the stacks of 2D chemical images obtained, each of which represents the spatial distribution of a chosen spectral band assigned to the component of interest at a different probing depth. ATR-FTIR imaging is also shown to have the ability to resolve subcellular components of cells such as organelles. For differentiation of diseased and non-diseased tissues, statistical tests are employed to analyse the spectral datasets obtained. When the second derivative of the spectral datasets was subjected to t-test analysis, the spectral differences between both samples in the fingerprint region are shown to be more significant at a shallow depth of penetration, with the greatest variance at the spectral band of 1235 cm-1 (vasPO2-), depicted by plotting the scores of PCA on its first two PCs. Overall, this paper demonstrates a non-destructive, label-free approach for examining heterogeneous biological samples in the z-direction to construct a 3D model using micro ATR-FTIR imaging, in a qualitative and semi-quantitative manner.

Superlensing plays a crucial role in near- and far-field optical imaging with sub-wavelength resolution. One of the ways to expand optical bandwidth is surface plasmon resonances in layered metal-dielectric nanostructures. These resonances are commonly excited at a tunable single frequency. In this study, we propose the concept of a multimode far-field superlens made of a titanium oxynitride (TiON) thin film, that is a disordered metal-dielectric refractory nano-composite. These films exhibit a double epsilon-near-zero (2-ENZ) behavior near the percolation threshold and, therefore, favor super-coupling the incident laser light to surface plasmon resonances, not using such couplers as a prism, a grating, etc. We experimentally observe stimulated Raman gain emission from nano-structured TiON thin films exposed to low-power continuous-wave laser light. It is shown that superresolution of

Biopharmaceuticals are used to treat a range of diseases from arthritis to cancer, however, since the advent of these highly specific, effective drugs, there have been challenges involved in their production. The most common biopharmaceuticals, monoclonal antibodies (mAbs), are vulnerable to aggregation and precipitation during processing. Freeze thaw cycles (FTCs), which can be required for storage and transportation, can lead to a substantial loss of product, and contributes to the high cost of antibody production. It is therefore necessary to monitor aggregation levels at susceptible points in the production pathway, such as during purification and transportation, thus contributing to a fuller understanding of mAb aggregation and providing a basis for rational optimisation of the production process. This paper uses attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and spectroscopic imaging to investigate the effect of these potentially detrimental FTCs on protein secondary structure in both static wells and under flowing conditions, using lysozyme as a model protein. The results revealed that the amount of protein close to the surface of the ATR crystal, and hence level of aggregates, increased with increasing FTCs. This was observed both within wells and under flow conditions, using conventional ATR-FTIR spectroscopy and ATR-FTIR spectroscopic imaging. Interestingly, we also observed changes in the Amide I band shape indicating an increase in β-sheet contribution, and therefore an increase in aggregates, with increasing number of FTCs. These results show for the first time how ATR-FTIR spectroscopy can be successfully applied to study the effect of FTC cycles on protein samples. This could have numerous broader applications, such as in biopharmaceutical production and rapid diagnostic testing., ATR-FTIR spectroscopy and spectroscopic imaging was used in combination with PDMS flow cells, and effectively applied to monitor the effect of repeat freeze thaw cycles (FTCs) on protein secondary structure, revealing higher aggregate levels with increasing FTCs.

Simple Summary Several lung extracellular matrix (ECM) proteins are involved in the formation of a metastatic niche in pulmonary metastasis and they accompany the cancer progression. Its gradual remodeling does not induce compositional changes of its components, but it is related to the re-distribution of individual proteins, their cross-linking and spatial arrangement within the tissue. The combination of FTIR and FTIR polarization contrast (PCI) imaging, as rapid, non-destructive, and label-free techniques, allows for the determination of protein alternations occurring in lungs that are affected by breast cancer metastasis. Both have the potential to characterize biochemical changes of the metastatic target, can determine phenotypes of tissue structures, and deliver a novel spectroscopic marker panel for the recognition of metastasis environment. Abstract The current understanding of mechanisms underlying the formation of metastatic tumors has required multi-parametric methods. The tissue micro-environment in secondary organs is not easily evaluated due to complex interpretation with existing tools. Here, we demonstrate the detection of structural modifications in proteins using emerging Fourier Transform Infrared (FTIR) imaging combined with light polarization. We investigated lungs affected by breast cancer metastasis in the orthotopic murine model from the pre-metastatic phase, through early micro-metastasis, up to an advanced phase, in which solid tumors are developed in lung parenchyma. The two IR-light polarization techniques revealed, for the first time, the orientational ordering of proteins upon the progression of pulmonary metastasis of breast cancer. Their distribution was complemented by detailed histological examination. Polarized contrast imaging recognised tissue structures of lungs and showed deformations in protein scaffolds induced by inflammatory infiltration, fibrosis, and tumor growth. This effect was recognised by not only changes in absorbance of the spectral bands but also by the band shifts and the appearance of new signals. Therefore, we proposed this approach as a useful tool for evaluation of progressive and irreversible molecular changes that occur sequentially in the metastatic process.

Metal soaps are formed in paint layers thorough the reaction of metal ions of pigments and fatty acids of organic binders. In this study, micro-ATR-FTIR spectroscopic imaging was used to analyse the formation of lead soaps in oil-based paint layers in relation to their exposure to moisture sources. The investigations were carried out on authentic samples of complex stratigraphies from cold painted terracotta statues (Sacred Mount, Varallo, UNESCO) and different IR-active lead white pigments, organic materials, and lead soaps were discriminated. The saponification of selected paint layers was correlated to the conservation history, the manufacturing technique, and the build-up of layers. The presence of hydrophilic layers within the stratigraphy and their role as a further water source are discussed. Furthermore, the modifications experienced by lead-based pigments from the core of an intact grain of pigment towards the newly formed decay phases were investigated via a novel approach based on shift of the peak for the corresponding spectral bands and their integrated absorbance in the ATR-FTIR spectra. Qualitative information on the spatial distribution from the chemical images was combined with quantitative information on the peak shift to evaluate the different manufacture (lead carbonate, basic lead carbonate) or the extent of decay undergone by the lead-based pigments as a function of their grain size, contiguous layers, and moisture source. Similar results, having a high impact on heritage science and analytical chemistry, allow developing up-to-date conservation strategies by connecting an advanced knowledge of the materials to the social and conservation history of artefacts. Supplementary Information The online version of this article (10.1007/s00216-020-03016-6) contains supplementary material, which is available to authorized users.

Molecular orientation of aromatic polyimides (PIs) and their precursor of poly(amic ester)s (PAE) in the biaxially oriented films were analyzed by polarized microscopic attenuated-total-reflection Fourier-transform infrared absorption spectroscopy (micro pATR-FTIR) imaging. The films were prepared by shearing a lyotropic liquid crystal (LC) solution of the PAE on a glass substrate and subsequent drying under a N2 flow, and the long axis of polymer chains were distributed around the shear direction. In the film, streak-shaped defects were observed along the shear direction with optical microscopy. Such structural heterogeneities on the micrometer (μm) scale are expected to be visualized in spatial distribution map of molecular orientation order acquired with micro pATR-FTIR imaging. In this study, uniaxial orientation order parameter, S, and a mean square cosine value, ⟨cos2ψ⟩, were used to quantify the degree of orientation of the PI main chain and that of aromatic imide plane, respectively. It was revealed that the films are apparently homogeneous in the spatial distribution map of the S, while the films exhibited obvious heterogeneity in that of ⟨cos2ψ⟩, in which “face-on” and “edge-on” orientation domains coexist. The results indicate that orientation direction of the rigid PI chains is fixed in the averaged orientation direction of the oriented PAE matrix during thermal imidization, while the aromatic imide ring can be rotated around the main chain. Furthermore, cracks in the PI film were successfully visualized by ATR-FTIR imaging, and the orientation distribution inside the cracks was investigated. Through this structural study, we validated the quantitative capability of the micro pATR-FTIR imaging method thorough the analyses of highly oriented PI films and demonstrated its ability to investigate μm-scale heterogeneity on the basis of molecular orientation analyses.

Exposing polymers to high-pressure and supercritical CO2 is a useful approach in polymer processing. Consequently, the mechanisms of polymer–polymer interaction under such conditions are worthy of further investigation. Two-dimensional correlation analysis and two-dimensional disrelation mapping were applied to datasets of polycaprolactone –poly(lactic acid) blend with or without high-pressure CO2 obtained using in situ attenuated total reflection Fourier transform spectroscopic imaging. The relatively weak dipole–dipole intermolecular interactions between polymer molecules were visualized through the disrelation maps for the first time. Because of the specially designed polymer interface, the interactions between the same type of polymer molecules and different types of polymer molecules were differentiated. Under exposure to high-pressure CO2, all three types of interactions: interaction between polycaprolactone molecules and poly(lactic acid) molecules, interaction between polycaprolactone molecules and interaction between poly(lactic acid) molecules become weaker than those in the polymer interface without high-pressure CO2. The resulting increase in the Flory interaction parameter is the main cause of phase separation in the PCL–PLA blend under high-pressure CO2. The findings from this study will be of benefit for polymer processing with high-pressure and supercritical CO2.

It is believed that ionic liquids (IL) can be a promising sorbent for separating a mixture of olefins and paraffins due to their unique properties. Understanding the interaction between IL and sorbed gases plays a key role in the development of selective separation processes. In this work, for the first time, in situ ATR-FTIR spectroscopy was used to study the interaction of light hydrocarbons (C2H6, C2H4) and a series of 1-alkyl-3-methylimidazolium tetrafluoroborate CnMIMBF4 (n = 2, 4, 6, 8, 10, 12) ILs. The spectra of liquid ethane and ethylene were obtained, as well as the spectra of IL under the pressure of hydrocarbons. An increase in the length of the alkyl chain of the cation leads to an increase in the solubility of both ethane and ethylene. The data obtained demonstrate a significant interaction between ethylene and IL, which leads to a greater dissolution of ethylene relative to ethane. A blue-shift of the bands of sorbed ethylene relative to liquid ethylene is observed. At the same time, an increase in the length of the alkyl chain of the cation leads to a shift in the wavenumber of sorbed ethylene towards lower wavenumbers, which is the result of a decrease in the interaction between IL and ethylene and the dissolution of ethylene in the free volume of IL. In addition, it has been found that it is possible for two hydrogen atoms of ethylene to interact to form a hydrogen bond between the anion of the IL and ethylene.

Modern bone tissue engineering is based on the use of implants in the form of biomaterials, which are used as scaffolds for osteoprogenitor or stem cells. The task of the scaffolds is to temporarily sustain the function, proliferation and differentiation of bone tissue to enable its regeneration. The aim of this work is to use the macro ATR-FTIR spectroscopic imaging for analysis of the ceramic-based biomaterial (chitosan/β-1,3-glucan/hydroxyapatite). Specifically, during long-term culture of mesenchymal cells derived from adipose tissue (ADSCs) and bone marrow (BMDSCs) on the surface of scaffold. Infrared spectroscopy allows the acquisition of information on both the organic and inorganic parts of the tested composite. This innovative spectroscopic approach proved to be very suitable for studying the formation of new bone tissue and ECM components, sample staining and demineralization are not required and consequently the approach is rapid and cost-effective. The novelty of this study focuses on the innovatory use of ATR-FTIR imaging to evaluate the molecular structure and maturity of collagen as well as mineral matrix formation and crystallization in the context of bone regenerative medicine. Our research has shown that the biomaterial investigated on this work facilitates the formation of valid bone ECM of the stem cells types studied, as a result of the synthesis of type I collagen and mineral content deposition. Nevertheless, ADSC cells have been proven to produce a greater amount of collagen with a lower content of helical secondary structures, at the same time showing a higher mineralization intensity compared to BMDSC cells. Considering the above results, it could be stated that the developed scaffold is a promising material for biomedical applications, including modification of bone implants to increase their biocompatibility.

Fourier transform infrared (FT-IR) spectroscopic imaging and microscopy of single living cells are established label-free technique for the study of cell biology. The constant driver to improve the spatial resolution of the technique is due to the diffraction limit given by infrared (IR) wavelength making subcellular study challenging. Recently, we have reported, with the use of a prototype zinc sulfide (ZnS) transmission cell made of two hemispheres, that the spatial resolution is improved by the factor of the refractive index of ZnS, achieving a λ/2.7 spatial resolution using the synchrotron–IR microscopy with a 36× objective with numerical aperture of 0.5. To refine and to demonstrate that the ZnS hemisphere transmission device can be translated to standard bench-top FT-IR imaging systems, we have, in this work, modified the device to achieve a more precise path length, which has improved the spectral quality of the living cells, and showed for the first time that the device can be applied to study live cells with three different bench-top FT-IR imaging systems. We applied focal plane array (FPA) imaging, linear array, and a synchrotron radiation single-point scanning method and demonstrated that in all cases, subcellular details of individual living cells can be obtained. Results have shown that imaging with the FPA detector can measure the largest area in a given time, while measurements from the scanning methods produced a smoother image. Synchrotron radiation single-point mapping produced the best quality image and has the flexibility to introduce over sampling to produce images of cells with great details, but it is time consuming in scanning mode. In summary, this work has demonstrated that the ZnS hemispheres can be applied in all three spectroscopic approaches to improve the spatial resolution without any modification to the existing microscopes.

Monoclonal antibodies (mAbs) have been used as therapeutics for the last few decades. It is necessary to investigate the stability of these mAbs under stress conditions and to elucidate aggregation mechanisms as a means of developing approaches which minimize the problem. Attenuated total reflection (ATR)-FTIR spectroscopic imaging allows probing of a sample at a depth of penetration of around 0.5-5 μm, which makes it suitable for the study of aggregated proteins when accumulated as a layer close to the surface of the ZnSe internal reflection element (IRE). Here, macro ATR-FTIR spectroscopic imaging, along with a variable angle of incidence accessory, have been used to differentiate between the secondary structure of proteins in bulk solution and those that have precipitated onto or near the ZnSe IRE surface. IgG spectra obtained from protein samples in individual wells have been averaged, extracted, and preprocessed, and the Amide I bands of the protein samples were compared and further analyzed to reveal protein distribution at the ZnSe IRE surface. These findings show depth profiling of IgG aggregates at the ZnSe IRE surface (0.5-5 μm) and do not follow a trend of decreasing protein presence with an increasing angle of incidence or increasing depth of penetration, suggesting an irregular distribution of aggregates in the z-direction.

Over the past decades, considerable progress has been made toward far-field optical imaging beyond the diffraction limit. However, most working proof-of-concepts are based on either time-consuming scanning of a subdiffraction focal spot over a sample or postrecovery treatment using a priori information on a sought image. To our knowledge, none of these can be regarded as being close to a perfect far-field superlensing system capable of real-time color imaging with subwavelength resolution. In this paper, we suggest a proof-of-concept for far-field nonlinear metalens that is made of a disordered metal–dielectric nanocomposite. Postoxidation of a refractory titanium nitride (TiN) thin film, used as a nonlinear plasmonic material, results in the formation of a titanium oxynitride (TiON) film comprising a mixture of multiple phases of TiOxNy. Due to a double epsilon-near-zero behavior near the percolation threshold, the TiON favors supercoupling of the incident light to surface plasmon resonance within the vi...

This chapter describes applications of attenuated total reflection (ATR)–Fourier transform infrared (FTIR) spectroscopy and ATR-FTIR spectroscopic imaging to studies of proteins. The latter method combines ATR-FTIR spectroscopy with an infrared array detector for obtaining both spatial and chemical information from protein samples. Two imaging modes, micro- and macro-ATR, provide a range of imaging fields of view and spatial resolutions. Micro-ATR-FTIR imaging has been successfully used to study hanging drop protein crystallization with high spatial resolution imaging, while macro-ATR-FTIR imaging provided new opportunities for in situ studies of protein crystallization and aggregation, as well as the effect of different wettability surface properties on protein adsorption and crystallization. Recent pioneering applications of ATR-FTIR spectroscopy involve analysis of protein ligand denaturation on chromatography columns, critical for improved industrial purification of biotherapeutics. These and other new high-throughput chemical imaging approaches are discussed in this chapter.

Drug amorphisation by loading to inorganic mesoporous carriers represents an emerging area of improving the dissolution rate and bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). In this work, for the first time, a molecular-level insight into the process of API loading to mesoporous SiO2 (silica) carriers by the hot-melt impregnation method and its subsequent release during dissolution was obtained using ATR-FTIR spectroscopic imaging. A physical mixture of ibuprofen crystals and mesoporous silica particles was heated and the dynamics of melt loading into the silica pore structure was directly observed in situ by ATR-FTIR spectroscopic imaging. The loss of crystallinity, the redistribution of the API in the silica pore network and the subsequent stabilisation of the amorphous form upon cooling were proven. The API was involved in two different kinds of molecular-level interactions: API dimers in the amorphous bulk, and individual API molecules adsorbed on the silica surface. The melt-loaded silica carriers were comprehensively characterised by DSC, SEM and dissolution tests, which proved dissolution rate enhancement due to amorphisation of the API. Drug release form the hot-melt loaded mesoporous silica carriers was observed in real time and the conditions leading to local re-crystallisation of super-saturated solution of the API were identified.

The triblock copolymer L121 [poly(ethylene glycol)5-block-poly(propylene glycol)68-block-poly(ethylene glycol)5], the room temperature ionic liquid BMIM BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) and the polymer PEG-400 (polyethylene glycol-400) have been compared in their liquid state to test their sorption capability of CO2 by exposure to high-pressure gas for 3 h in a controlled system. The presence of the gas in the studied systems has been determined at atmospheric pressure in the temperature range 288.15–313.15 K by using near-infrared (NIR) spectroscopy. The CO2 sorption in BMIM BF4 and PEG-400 was very small and detectable up to 293.15 K, only L121 showed the CO2 typical bands in the NIR region of the spectra up to 313.15 K, thus a linear correlation can be obtained by plotting the CO2 absorbance of those bands as a function of temperature. The effect induced by temperature on the swelling degree of L121 copolymer has also been investigated.

High-pressure and supercritical CO2 (scCO2) have the potential to be employed as alternatives to organic solvents for processing polymeric materials. High-pressure and scCO2 offer advantages for polymer processing that include, inter alia, plasticisation, phase separation in blends, crystal modification, and swelling of polymers. These effects can be useful for selectively treating polymeric samples for a range of applications. This opinion paper will discuss the importance of Fourier transform infrared (FTIR) spectroscopy, in attenutated total reflection (ATR) mode, to aid the understanding of polymeric processing based on their unique molecular vibrations. This information is integral for developing more efficient processing pathways which will mean that the full potential of high-pressure and scCO2 processing can be realised. The current state-of-the-art will be reported that will include an overview of key recent advances utilising FTIR spectroscopy. Challenges and future areas of research will be outlined where new and exciting opportunities using this “green” processing technology will be predicted.

We report a new approach for infrared spectroscopic analysis of fiberglass materials using a mirror substrate, which allowed the specular reflection from the sample surface to be minimized and detect the light passing through the sample. The application of this technique for platinum-containing fiberglass catalysts made it possible for the first time to identify sulfate compounds formed in glass fibers during the oxidation reaction of sulfur dioxide. The developed technique can be applied for a number of research samples that are difficult to analyze by conventional IR spectroscopic methods.

In this work, the first use of a cellulose hydrogel film reconstituted from ionic liquid (IL) 1-butyl-3-methylimidazolium chloride for the fluorescent determination of a plant antimalarial endopero...

In situ characterisation of ionic liquids under a controlled environment has been performed in a high throughput manner using macro ATR-FTIR spectroscopic imaging. 14 different ionic liquids with cations 1-butyl-3-methylimidazolium ([C4mim]), 1-butyl-2,3-dimethylimidazolium ([C4mmim]) and 1-butyl-3-methylpyrrolidinium ([C4C1pyrr]) and anions hexafluorophosphate ([PF6]), tetrafluoroborate ([BF4]), bis(trifluoromethylsulfonyl)imide ([NTf2]), perchlorate ([ClO4]), trifluoromethanesulfonate ([CF3SO3]), nitrate ([NO3]), methanesulfonate ([CH3SO3]) and trifluoroacetate ([TA]) were studied. The ionic liquids were deposited onto the measuring surface of the ATR crystal in the corresponding accessory hosted in the FTIR imaging system. Then these samples were exposed to a controlled environment of toluene and water vapour and spectra acquired simultaneously. Changing the structure of the cation head group from [C4mim] to [C4mmim] or [C4C1pyrr] only had a small effect on the toluene absorption while increasing the length of the alkyl chain of the cation (e.g. [C10mim]) has shown a significant increase in toluene absorption. The ionic liquids with the anion [NTf2] were found to absorb the highest amount of toluene followed by [CF3SO3], then [PF6], [ClO4], [NO3] and [TA], and the lowest amount of toluene was absorbed in ionic liquids with [BF4] or [CH3SO3] anions. The amount of water absorbed increases in the order: [C4mim][CH3SO3] > [C4mim][TA] > [C4mim][NO3] > [C4mim][CF3SO3] > [C4mim][ClO4] ~ [C4mim][BF4] ~ [C4mmim][BF4] > [C10mim][BF4] > [C4mim][PF6] ~ [C4mmim][PF6] > [C4mim][NTf2] ~ [C4mmim][NTf2] ~ [C4C1pyrr][NTf2]. This work has demonstrated that spectroscopic imaging provides a platform for the simultaneous screening of multiple ionic liquids in situ, when under controlled environments.

Spectroscopic imaging of biomaterials and biological systems has received increased interest within the last decade because of its potential to aid in the detection of disease using biomaterials/biopsy samples and to probe the states of live cells in a label-free manner. The factors behind this increased attention include the availability of improved infrared microscopes and systems that do not require the use of a synchrotron as a light source, as well as the decreasing costs of these systems. This article highlights the current technical challenges and future directions of mid-infrared spectroscopic imaging within this field. Specifically, these are improvements in spatial resolution and spectral quality through the use of novel added lenses and computational algorithms, as well as quantum cascade laser imaging systems, which offer advantages over traditional Fourier transform infrared systems with respect to the speed of acquisition and field of view. Overcoming these challenges will push forward spectroscopic imaging as a viable tool for disease diagnostics and medical research. Graphical abstract Absorbance images of a biopsy obtained using an FTIR imaging microscope with and without an added lens, and also using a QCL microscope with high-NA objective.

An application of disrelation mapping to Fourier transform infrared (FT-IR) spectroscopic imaging datasets is provided to reveal different H-bonded water species within a mammalian cell. 2D correlation analysis revealed a disrelation peak at (3420 cm-1, 3220 cm-1), showing the existence of a specific water band at around 3220 cm-1 whose variation of absorbance did not follow the trend of water molecules with a well-coordinated H-bonding network. Disrelation maps constructed with disrelation intensities between (3420 cm-1, 3220 cm-1) and (3420 cm-1, 1540 cm-1) reveal that the disruption of the water network occurs around the interfacial regions between the cell and media, indicating the disintegration of the H-bonding network of bulk water due to the entrapment of water by the protein inside the cell. This hydration effect also becomes apparent around the area adjacent to the cellular nucleus, reflecting the fact that protein synthesis mainly occurs in this region. These results clearly show the presence of different molecular states of water inside living cells, which are not readily identified by conventional analysis methods.

Non-equilibrium behavior of liquid mixture of polyethylene glycol (PEG) and polypropylene glycol (PPG) is studied. During the phase variation of PEG/PPG mixture, time-resolved Fourier transform infrared (FTIR) spectra were collected by attenuated total reflection (ATR) technique to selectively capture the development and subsequent variation of PEG-rich phase, appearing within a layer of the sample adjacent to the measuring surface of the ATR diamond prism. The FTIR spectra were then subjected to a two-dimensional (2D) correlation method to elucidate subtle but important changes in the absorbance of spectral bands. 2D correlation spectra revealed fine details of the non-equilibrium system. During the phase variation, dissociation between PEG and PPG generates free PEG molecules first. The emergence of the free PEG molecules triggers the subsequent self-assembly via the development of intermolecular H-bonding between PEG molecules, which eventually generates bigger PEG aggregates.

The approach for quantitative estimation of asphaltene sizes in crude oils in situ via precise simulation of electron spin resonance (ESR) spectra of the slowly rotating VO2+-containing fragments was developed. The method is based on the correlation between the size of the paramagnetic particles and their characteristic rotational time that can be determined by ESR in situ while incomplete averaging of anisotropic hyperfine interactions is observed. The precise simulation of the ESR spectra of heavy molecules, labeled naturally with vanadyl ions, allows one to find their size distribution in crude oils. In particular, the method is demonstrated to be an effective tool for the quantitative determination of the asphaltene sizes in different oil fractions in situ.

A new large-area germanium ATR crystal is utilised with an FTIR microscope to improve the acquired images of de-paraffinized colon biopsy sections, without recourse to a synchrotron source. The large crystal (⌀ = 28 mm) offers significant improvements compared to slide-on small germanium crystal (⌀ = 3.5 mm); for example, it facilitates more uniform distribution of higher signal intensity within the field of view and more rapid acquisition time. Mapping of a larger sample area up to ca. 350 × 350 μm2 with this new set-up, coupled with imaging using an FPA detector, is demonstrated for the first time on biological specimens. The performance of k-means clustering algorithm applied to classify the different anatomical structures of the colon biopsies is greatly improved with mapping. Comparison of H&E stained adjacent tissue sections with false-colour k-means images strongly support differentiation of five distinct regions within tissues. The efficiency of the methodology to categorise colon tissues at various stages of malignancy is analysed via multivariate chemometrics. The second derivative spectra extracted from the crypt region of the colon were subjected to Partial Least Squares classification. Good separation between data in clusters occurs when projecting spectra on a PLS score plot on a plane made by the first 3 principal components. Important spectral biomarkers for colon malignancy classification were identified to exist mostly in the fingerprint region of the FTIR spectrum based on the chemometrics analysis.

Activated carbons (ACs) show great potential for selective adsorption removal of sulfur (SARS) from hydrocarbon fuels but require improvements in uptake and selectivity. Moreover, systematic equilibria and kinetic analyses of ACs for desulfurization are still lacking. This work examines the influence of modifying a commercial-grade activated carbon (AC) by CO2 and steam treatment for the selective adsorption removal of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 323 K. An untreated AC and a charcoal Norit carbon (CN) were used for comparative purposes. Physicochemical characterization of the samples was carried out by combining N2-physisorption, X-ray diffractometry, microscopy, thermogravimetric and infrared analyses. The steam and CO2 treated ACs exhibited higher sulfur uptakes than the untreated AC and CN samples. The steam treated AC appears to be especially effective to remove sulfur, showing a remarkable sulfur uptake (~24 mgS·gads−1 from a mixture of 1500 ppmw of DBT and 1500 ppm 4,6-DMDBT) due to an increased surface area and microporosity. The modified ACs showed similar capacities for both DBT and the sterically hindered 4,6-DMDBT molecules. In addition, they were found to be selective in the presence of sulfur-free aromatics and showed good multicycle stability. Compared to other adsorbents, the modified ACs exhibited relatively high adsorption capacities. The combination of batch and fixed bed measurements revealed that the adsorption sites of the samples are characterized as heterogeneous due to the better fit to the Freundlich isotherm. The kinetic breakthrough profiles were described by the linear driving force (LDF) model.