High spatial resolution (1.1 μm and 20 nm) FTIR polarization contrast imaging reveals pre-rupture disorder in damaged tendon

Topical Nanoliposomal Collagen Delivery for Targeted Fibril Formation by Electrical Stimulation

Collagen is a complex, large protein molecule that presents a challenge in delivering it to the skin due to its size and intricate structure. However, conventional collagen delivery methods are either invasive or may affect the protein's structural integrity. This study introduces a novel approach involving the encapsulation of collagen monomers within zwitterionic nanoliposomes, termed Lip-Cols, and the controlled formation of collagen fibrils through electric fields (EF) stimulation. The results reveal the self-assembly process of Lip-Cols through electroporation and a pH gradient change uniquely triggered by EF, leading to the alignment and aggregation of Lip-Cols on the electrode interface. Notably, Lip-Cols exhibit the capability to direct the orientation of collagen fibrils within human dermal fibroblasts. In conjunction with EF, Lip-Cols can deliver collagen into the dermal layer and increase the collagen amount in the skin. The findings provide novel insights into the directed formation of collagen fibrils via electrical stimulation and the potential of Lip-Cols as a non-invasive drug delivery system for anti-aging applications.

Linearly Polarized Infrared Spectroscopy for the Analysis of Biological Materials

The analysis of biological samples with polarized infrared spectroscopy (p-IR) has long been a widely practiced method for the determination of sample orientation and structural properties. In contrast to earlier works, which employed this method to investigate the fundamental chemistry of biological systems, recent interests are moving toward "real-world" applications for the evaluation and diagnosis of pathological states. This focal point review provides an up-to-date synopsis of the knowledge of biological materials garnered through linearly p-IR on biomolecules, cells, and tissues. An overview of the theory with special consideration to biological samples is provided. Different modalities which can be employed along with their capabilities and limitations are outlined. Furthermore, an in-depth discussion of factors regarding sample preparation, sample properties, and instrumentation, which can affect p-IR analysis is provided. Additionally, attention is drawn to the potential impacts of analysis of biological samples with inherently polarized light sources, such as synchrotron light and quantum cascade lasers. The vast applications of p-IR for the determination of the structure and orientation of biological samples are given. In conclusion, with considerations to emerging instrumentation, findings by other techniques, and the shift of focus toward clinical applications, we speculate on the future directions of this methodology.

Digital Histopathology by Infrared Spectroscopic Imaging

Infrared (IR) spectroscopic imaging records spatially resolved molecular vibrational spectra, enabling a comprehensive measurement of the chemical makeup and heterogeneity of biological tissues. Combining this novel contrast mechanism in microscopy with the use of artificial intelligence can transform the practice of histopathology, which currently relies largely on human examination of morphologic patterns within stained tissue. First, this review summarizes IR imaging instrumentation especially suited to histopathology, analyses of its performance, and major trends. Second, an overview of data processing methods and application of machine learning is given, with an emphasis on the emerging use of deep learning. Third, a discussion on workflows in pathology is provided, with four categories proposed based on the complexity of methods and the analytical performance needed. Last, a set of guidelines, termed experimental and analytical specifications for spectroscopic imaging in histopathology, are proposed to help standardize the diversity of approaches in this emerging area.

Super-resolution mid-infrared spectro-microscopy of biological applications through tapping mode and peak force tapping mode atomic force microscope

Small biomolecules at the subcellular level are building blocks for the manifestation of complex biological activities. However, non-intrusive in situ investigation of biological systems has been long daunted by the low spatial resolution and poor sensitivity of conventional light microscopies. Traditional infrared (IR) spectro-microscopy can enable label-free visualization of chemical bonds without extrinsic labeling but is still bound by Abbe's diffraction limit. This review article introduces a way to bypass the optical diffraction limit and improve the sensitivity for mid-IR methods - using tip-enhanced light nearfield in atomic force microscopy (AFM) operated in tapping and peak force tapping modes. Working principles of well-established scattering-type scanning near-field optical microscopy (s-SNOM) and two relatively new techniques, namely, photo-induced force microscopy (PiFM) and peak force infrared (PFIR) microscopy, will be briefly presented. With ∼ 10-20 nm spatial resolution and monolayer sensitivity, their recent applications in revealing nanoscale chemical heterogeneities in a wide range of biological systems, including biomolecules, cells, tissues, and biomaterials, will be reviewed and discussed. We also envision several future improvements of AFM-based tapping and peak force tapping mode nano-IR methods that permit them to better serve as a versatile platform for uncovering biological mechanisms at the fundamental level.

Compliance of the fish outflow tract is altered by thermal acclimation through connective tissue remodelling

To protect the gill capillaries from high systolic pulse pressure, the fish heart contains a compliant non-contractile chamber called the bulbus arteriosus which is part of the outflow tract (OFT) which extends from the ventricle to the ventral aorta. Thermal acclimation alters the form and function of the fish atria and ventricle to ensure appropriate cardiac output at different temperatures, but its impact on the OFT is unknown. Here we used ex vivo pressure-volume curves to demonstrate remodelling of passive stiffness in the rainbow trout (Oncorhynchus mykiss) bulbus arteriosus following more than eight weeks of thermal acclimation to 5, 10 and 18°C. We then combined novel, non-biased Fourier transform infrared spectroscopy with classic histological staining to show that changes in compliance were achieved by changes in tissue collagen-to-elastin ratio. In situ gelatin zymography and SDS-PAGE zymography revealed that collagen remodelling was underpinned, at least in part, by changes in activity and abundance of collagen degrading matrix metalloproteinases. Collectively, we provide the first indication of bulbus arteriosus thermal remodelling in a fish and suggest this remodelling ensures optimal blood flow and blood pressure in the OFT during temperature change.

High-resolution infrared microspectroscopic characterization of cartilage cell microenvironment

The lateral resolution of infrared spectroscopy has been inadequate for accurate biochemical characterization of the cell microenvironment, a region regulating biochemical and biomechanical signals to cells. In this study, we demonstrate the capacity of a high-resolution Fourier transform infrared microspectroscopy (HR-FTIR-MS) to characterize the collagen content of this region. Specifically, we focus on the collagen content in the cartilage cell (chondrocyte) microenvironment of healthy and osteoarthritic (OA) cartilage. Human tibial cartilage samples (N = 28) were harvested from 7 cadaveric donors and graded for OA severity (healthy, early OA, advanced OA). HR-FTIR-MS was used to analyze the collagen content of the chondrocyte microenvironment of five distinct zones across the tissue depth. HR-FTIR-MS successfully showed collagen content distribution across chondrocytes and their environment. In zones 2 and 3 (10 - 50% of the tissue thickness), we observed that collagen content was smaller (P < 0.05) in early OA compared to the healthy tissue in the vicinity of cells (pericellular region). The collagen content loss was extended to the extracellular matrix in advanced OA tissue. No significant differences in the collagen content of the chondrocyte microenvironment were observed between the groups in the most superficial (0-10%) and deep zones (50-100%). HR-FTIR-MS revealed collagen loss in the early OA cartilage pericellular region before detectable changes in the extracellular matrix in advanced OA. HR-FTIR-MS-based compositional assessment enables a better understanding of OA-related changes in tissues. This technique can be used to identify new disease mechanisms enabling better intervention strategies. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) is the most common degenerative joint disease causing pain and disability. While significant progress has been made in OA research, OA pathogenesis is still poorly understood and current OA treatments are mainly palliative. This study demonstrates that high-resolution FTIR microspectroscopy (HR-FTIR-MS) can characterize OA-induced compositional changes in the cell microenvironment (pericellular matrix) during the early disease stages before tissue changes in the extracellular matrix become apparent. This technique may further enable the identification of new OA mechanisms and improve our current understanding of OA pathogenesis, thus, enabling the development of better treatment methods.

Fourier Transform Infrared Spectroscopy in Oral Cancer Diagnosis

Oral cancer is one of the most common cancers worldwide. Despite easy access to the oral cavity and significant advances in treatment, the morbidity and mortality rates for oral cancer patients are still very high, mainly due to late-stage diagnosis when treatment is less successful. Oral cancer has also been found to be the most expensive cancer to treat in the United States. Early diagnosis of oral cancer can significantly improve patient survival rate and reduce medical costs. There is an urgent unmet need for an accurate and sensitive molecular-based diagnostic tool for early oral cancer detection. Fourier transform infrared spectroscopy has gained increasing attention in cancer research due to its ability to elucidate qualitative and quantitative information of biochemical content and molecular-level structural changes in complex biological systems. The diagnosis of a disease is based on biochemical changes underlying the disease pathology rather than morphological changes of the tissue. It is a versatile method that can work with tissues, cells, or body fluids. In this review article, we aim to summarize the studies of infrared spectroscopy in oral cancer research and detection. It provides early evidence to support the potential application of infrared spectroscopy as a diagnostic tool for oral potentially malignant and malignant lesions. The challenges and opportunities in clinical translation are also discussed.

Fourier Transform Infrared Polarization Contrast Imaging Recognizes Proteins Degradation in Lungs upon Metastasis from Breast Cancer

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.

Orientation Matters: Polarization Dependent IR Spectroscopy of Collagen from Intact Tendon Down to the Single Fibril Level

Infrared (IR) spectroscopy has been used for decades to study collagen in mammalian tissues. While many changes in the spectral profiles appear under polarized IR light, the absorption bands are naturally broad because of tissue heterogeneity. A better understanding of the spectra of ordered collagen will aid in the evaluation of disorder in damaged collagen and in scar tissue. To that end, collagen spectra have been acquired with polarized far-field (FF) Fourier Transform Infrared (FTIR) imaging with a Focal Plane Array detector, with the relatively new method of FF optical photothermal IR (O-PTIR), and with nano-FTIR spectroscopy based on scattering-type scanning near-field optical microscopy (s-SNOM). The FF methods were applied to sections of intact tendon with fibers aligned parallel and perpendicular to the polarized light. The O-PTIR and nano-FTIR methods were applied to individual fibrils of 100–500 nm diameter, yielding the first confirmatory and complementary results on a biopolymer. We observed that the Amide I and II bands from the fibrils were narrower than those from the intact tendon, and that both relative intensities and band shapes were altered. These spectra represent reliable profiles for normal collagen type I fibrils of this dimension, under polarized IR light, and can serve as a benchmark for the study of collagenous tissues.

Effect of testing temperature on the nanostructural response of tendon to tensile mechanical overload

Despite many in vitro mechanical experiments of tendon being conducted at room temperature, few assessments have been made to determine how the structural response of tendon to mechanical overload may vary with ambient temperature. We explored whether damage to the collagen nanostructure of tendon resulting from tensile rupture varies with temperature. Use of bovine tail tendons in combination with NaBH₄ crosslink stabilization treatment allowed us to probe the mechanisms underlying the observed changes. Untreated tendons and NaBH₄-stabilized tendons were pulled to rupture at temperatures of 24, 37, and 55 °C. Of nine mechanical parameters measured from the resulting stress-strain curves, only yield stress differed between the tendons tested at 37 and 24 °C. When tested at 55 °C, untreated tendons showed large reductions in ultimate strength and toughness, while NaBH₄-stabilized tendons showed smaller reductions. Differential scanning calorimetry was used to assess damage to the collagen fibril nanostructure of tendons resulting from rupture, with samples from the ruptured tendons compared to samples from the same tendons removed prior to loading. While there was indication that overload-induced molecular packing disruption to collagen fibrils may be heightened at 37 °C, statistical increases in damage compared to that occurring at 24 °C were only seen when testing was conducted at 55 °C. The results show that the temperature sensitivity of tendon to ramp loading depends on crosslinking within the tissue. In poorly crosslinked tissues, collagen may be more susceptible to mechanical damage when tested at physiologic temperature compared to room temperature. For tendons with a high density of thermally stable crosslinks, such as the human Achilles or patellar tendons, testing at room temperature should produce comparable results to testing at physiologic temperature.

Assessing collagen fibrils molecular damage after a single stretch-release cycle

Mechanical testing of connective tissues such as tendons and ligaments can lead to collagen denaturation even in the absence of macroscale damage. The following tensile loading protocols, ramp loading to failure, overloading and release, cyclic overloading and cyclic fatigue loading, all yield molecular damage in rat or bovine tendons. Single collagen fibrils extracted from the positional common digital extensor tendon of the forelimb also show molecular damage after tensile loading to failure. Using fibrils from the same source we assess changes to the molecular and supramolecular structure after tensile stress relaxation at strains between 4 and 22% followed by release. We observe no broken fibril and no significant change in D-band spacing. However, we observe significant binding of a fluorescent collagen hybridizing peptide to the fibrils indicating that collagen denaturation occurs in a strain dependent way for relaxation times between 1 s and 1500 s. We also show that peptide binding is associated with a decrease of the cross-sectional area of the fibrils providing an estimate of the dry volume loss due to molecular denaturation as well as an estimate of the mechanical energy density required, 25-110 MJ m^-3. In summary we show that collagen molecular damage can occur in the absence of fibril failure and without visible changes to the supramolecular structure.

Quantifying Polymer Chain Orientation in Strong and Tough Nanofibers with Low Crystallinity: Toward Next Generation Nanostructured Superfibers

Advanced fibers revolutionized structural materials in the second half of the 20th century. However, all high-strength fibers developed to date are brittle. Recently, pioneering simultaneous ultrahigh strength and toughness were discovered in fine (<250 nm) individual electrospun polymer nanofibers (NFs). This highly desirable combination of properties was attributed to high macromolecular chain alignment coupled with low crystallinity. Quantitative analysis of the degree of preferred chain orientation will be crucial for control of NF mechanical properties. However, quantification of supramolecular nanoarchitecture in NFs with low crystallinity in the ultrafine diameter range is highly challenging. Here, we discuss the applicability of traditional as well as emerging methods for quantification of polymer chain orientation in nanoscale one-dimensional samples. Advantages and limitations of different techniques are critically evaluated on experimental examples. It is shown that straightforward application of some of the techniques to sub-wavelength-diameter NFs can lead to severe quantitative and even qualitative artifacts. Sources of such size-related artifacts, stemming from instrumental, materials, and geometric phenomena at the nanoscale, are analyzed on the example of polarized Raman method but are relevant to other spectroscopic techniques. A proposed modified, artifact-free method is demonstrated. Outstanding issues and their proposed solutions are discussed. The results provide guidance for accurate nanofiber characterization to improve fundamental understanding and accelerate development of nanofibers and related nanostructured materials produced by electrospinning or other methods. We expect that the discussion in this review will also be useful to studies of many biological systems that exhibit nanofilamentary architectures and combinations of high strength and toughness.

Ultrastructural and SINS analysis of the cell wall integrity response of Aspergillus nidulans to the absence of galactofuranose

With lethal opportunistic fungal infections on the rise, it is imperative to explore new methods to examine virulence mechanisms. The fungal cell wall is crucial for both the virulence and viability of Aspergillus nidulans. One wall component, Galf, has been shown to contribute to important fungal processes, integrity of the cell wall and pathogenesis. Here, we explore gene deletion strains lacking the penultimate enzyme in Galf biosynthesis (ugmAΔ) and the protein that transports Galf for incorporation into the cell wall (ugtAΔ). In applying gene deletion technology to the problem of cell wall integrity, we have employed multiple micro- and nano-scale imaging tools, including confocal fluorescence microscopy, electron microscopy, X-Ray fluorescence and atomic force microscopy. Atomic force microscopy allows quantification of ultrastructural cell wall architecture while near-field infrared spectroscopy provides spatially resolved chemical signatures, both at the nanoscale. Here, for the first time, we demonstrate correlative data collection with these two emerging modalities for the multiplexed in situ study of the nanoscale architecture and chemical composition of fungal cell walls.

Analysis of molecular orientation in polymeric spherulite using polarized micro attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic imaging

Micro ATR-FTIR spectroscopic imaging enables the visualization of two-dimensional chemical distribution at a higher spatial resolution than macro-transmission FTIR imaging approach. In this study, micro ATR-FTIR imaging was applied for analysis of a specific morphology in a spherulite of poly(3-hydroxybutyrate) (PHB). The PHB spherulites crystallized at an isothermal condition, showed the fine band structure due to the twisting lamellar crystals during the spherulite growth under the polarized optical microscope (POM). In addition, the band structure observed in the PHB spherulite was the double band pattern in which the higher and lower birefringence banded areas alternatively appear due to the three-dimensional orientation of crystallographic axes and the biaxial refractive index ellipsoid of PHB crystalline structure. Micro ATR-FTIR spectroscopic imaging was employed for detecting the double band structure in the PHB spherulite. However, the obtained spectral images did not indicate any band structures. To detect the difference of molecular orientation among the double band structures, the micro ATR-FTIR imaging was performed with a linear polarizer at four different angles. The mean values of absorbance in each measured area changed depending on the polarizer angle. The in-plane molecular orientation to the tangential direction of spherulite, caused by the dependence of the average absorbance on the polarizer angles, was determined by the position of measured area in the spherulite and the linear dicroism of each of the spectral band used. To visualize the small difference of molecular orientation in the double band structure, micro ATR-FTIR images of the dichroic differences at three spectral bands were calculated from two different sets of polarizer angles. The micro ATR-FTIR images representing the dichroic differences displayed their corresponding distributions among three spectral bands. The complementary distributions of the dichroic difference were caused by the crystallographic orientation of b- and c-axes and were successfully visualized to reveal the pattern with the features less than 10 μm in size. The results achieved in this study were due to two advantages of the polarized micro ATR-FTIR imaging: the high spatial resolution of micro ATR-FTIR imaging technique, and the high sensitivity of polarization measurements. Thus, this work demonstrates the power of this spectroscopic approach for such analytical investigation.

Advanced glycation end-product cross-linking inhibits biomechanical plasticity and characteristic failure morphology of native tendon

Advanced glycation end-products (AGEs) are formed in vivo from the nonenzymatic reaction between sugars and proteins. AGEs accumulate in long-lived tissues like tendons, cross-linking neighboring collagen molecules, and are in part complicit in connective tissue pathologies experienced in aging and with diabetes. We have previously described discrete plasticity: a characteristic form of nanoscale collagen fibril damage consisting of serial fibril kinking and collagen denaturation that occurs in some mechanically overloaded tendons. We suspect that this failure mechanism may be an adaptive trait of collagen fibrils and have published evidence that inflammatory cells may be able to recognize and digest the denatured collagen produced by overload. In this study, we treated bovine tail tendons with ribose to simulate long-term AGE cross-linking in vitro. We hypothesized that a high degree of cross-linking would inhibit the intermolecular sliding thought to be necessary for discrete plasticity to occur. Tendons were mechanically overloaded, and properties were investigated by differential scanning calorimetry and scanning election microscopy. Ribose cross-linking treatment altered the mechanical response of tendons after the yield point, significantly decreasing postyield extensibility and strain energy capacity before rupture. Coincident with altered mechanics, ribose cross-linking completely inhibited the discrete plasticity failure mechanism of tendon. Our results suggest that discrete plasticity, which may be an important physiological mechanism, becomes pathologically disabled by the formation of AGE cross-links in aging and diabetes. NEW & NOTEWORTHY We have previously shown that mechanically overloaded collagen fibrils in mammalian tendons accrue nanoscaled damage. This includes development of a characteristic kinking morphology within a shell of denatured collagen: discrete plasticity. Here, using a ribose-incubation model, we show that advanced glycation end-product cross-linking associated with aging and diabetes completely inhibits this mechanism. Since discrete plasticity appears to cue cellular remodeling, this result has important implications for diabetic tendinopathy.

Near-field infrared nanospectroscopy and super-resolution fluorescence microscopy enable complementary nanoscale analyses of lymphocyte nuclei

Recent super-resolution fluorescence microscopy (3D-Structured Illumination Microscopy, 3D-SIM) studies have revealed significantly altered nuclear organization between normal lymphocyte nuclei and those of classical Hodgkin's Lymphoma. Similar changes have been found in Multiple Myeloma (MM) nuclei, as well as in a premalignant condition, Monoclonal Gammopathy of Unknown Significance (MGUS). Using 3D-SIM, an increase in DNA-poor and DNA-free voids was evident in reconstructed 3D-SIM images of diseased nuclei at 40 nm pixel resolution (x,y: 40 nm, z: 80 nm). At best, far-field FTIR imaging yields spatially resolved images at ∼500 nm spatial resolution; however, near-field infrared imaging breaks the diffraction limit at a scale comparable to that of 3D-SIM, providing details on the order of 30 nm spatial resolution. We report here the first near-field IR imaging of lymphocyte nuclei, and far-field IR imaging results of whole lymphocytes and nuclei from normal human blood. Cells and nuclei were mounted on infrared-compatible substrates, including CaF2, undoped silicon wafers, and gold-coated silicon wafers. Thermal source far-field FTIR images were obtained with an Agilent-Cary 620 microscope, 15× objective, 0.62 NA and 64 × 64 array Focal Plane Array detector (University of Manitoba), or with a similar microscope equipped with both 15× and 25× (0.81 NA) objectives, 128 × 128 FPA and either thermal source or synchrotron source (single beam) infrared light at the Advanced Light Source (ALS), LBNL, Berkeley CA. Near-field IR spectra were acquired at the ALS, on the in-house SINS equipment, as well as with a Neaspec system, both illuminated with synchrotron light. Finally, some near-field IR spectra and images were acquired at Neaspec GmbH, Germany. Far-field IR spectra of normal cells and nuclei showed the characteristic bands of DNA and proteins. Near-field IR spectra of nuclei showed variations in bands assigned to protein and nucleic acids including single and double-stranded DNA. Near-field IR images of nuclei enabled visualization of protein and DNA distribution in spatially-resolved chromosome territories and nuclear pores.

Ultrastructure of tendon rupture depends on strain rate and tendon type

Previous research has shown that both the mechanics and elongation mechanisms of tendon and ligament vary with strain rate during tensile loading. In this study, we sought to determine if the ultrastructural damage created during tendon rupture also varies with strain rate. A bovine forelimb model was used, allowing two anatomically proximate but physiologically distinct tendons to be studies: the positional common digital extensor tendon, and the energy storing superficial digital flexor tendon. Samples from the two tendon types were ruptured at rates of either 1%/s or 10%/s. Relative to unruptured control samples, changes to collagen fibril structure were assessed using scanning electron microscopy (SEM), and changes to collagen molecule packing were studied using differential scanning calorimetry (DSC). Rupture at 1%/s caused discrete plasticity damage that extended along the length of collagen fibrils in both the extensor and flexor tendons. Consistent with this, DSC showed molecular packing disruption relative to control samples. Both SEM and DSC showed that extensor tendon fibrils sustained more severe damage than the more highly crosslinked flexor tendon fibrils. Increasing strain rate during rupture decreased the level of longitudinal disruption experienced by the collagen fibrils of both tendon types. Disruption to D-banding was no longer seen in the extensor tendon fibrils, and discrete plasticity damage was completely eliminated in the flexor tendon fibrils, indicating a transition to localized point failure. Ultrastructural damage resulting from tendon rupture depends on both strain rate and tendon type. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2842-2850, 2018.

Low-aberration beamline optics for synchrotron infrared nanospectroscopy

Synchrotron infrared nanospectroscopy is a recently developed technique that enables new possibilities in the broadband chemical analysis of materials in the nanoscale, far beyond the diffraction limit in this frequency domain. Synchrotron infrared ports have exploited mainly the high brightness advantage provided by electron storage rings across the whole infrared range. However, optical aberrations in the beam produced by the source depth of bending magnet emission at large angles prevent infrared nanospectroscopy to reach its maximum capability. In this work we present a low-aberration optical layout specially designed and constructed for a dedicated synchrotron infrared nanospectroscopy beamline. We report excellent agreement between simulated beam profiles (from standard wave propagation and raytracing optics simulations) with experimental measurements. We report an important improvement in the infrared nanospectroscopy experiment related to the improved beamline optics. Finally, we demonstrate the performance of the nanospectroscopy endstation by measuring a hyperspectral image of a polar material and we evaluate the setup sensitivity by measuring ultra-thin polymer films down to 6 nm thick.