Synchrotron Fourier Transform Infrared Research Articles

Morphological and organic spectroscopic studies of a 44-million-year-old leaf beetle (Coleoptera: Chrysomelidae) in amber with endogenous remains of chitin

This study details the quality of preservation of amber deposits in the Eocene. Through Baltic amber crack-out studies using Synchrotron Micro-Computed Tomography and Scanning Electron Microscopy it was found that the cuticle of a specimen of leaf beetle (Crepidodera tertiotertiaria (Alticini: Galerucinae: Chrysomelidae)) is exceptionally well preserved. Spectroscopic analysis using Synchrotron Fourier Transform Infrared Spectroscopy suggests presence of degraded upalpha-chitin in multiple areas of the cuticle, and Energy Dispersive Spectroscopy supports the presence of organic preservation. This remarkable preservation is likely the result of several factors such as the favourable antimicrobial and physical shielding properties of Baltic amber as compared to other depositional media, coupled to rapid dehydration of the beetle early in its taphonomic process. We provide evidence that crack-out studies of amber inclusions, although inherently destructive of fossils, are an underutilised method for probing exceptional preservation in deep time.

Monitoring surface dynamics of electrodes during electrocatalysis using in situ synchrotron FTIR spectroscopy.

Monitoring the surface dynamics of catalysts under working conditions is important for a deep understanding of the underlying electrochemical mechanisms towards efficient energy conversion and storage. Fourier transform infrared (FTIR) spectroscopy with high surface sensitivity has been considered as a powerful tool for detecting surface adsorbates, but it faces a great challenge when being adopted in surface dynamics investigations during electrocatalysis due to the complication and influence of aqueous environments. This work reports a well designed FTIR cell with tunable micrometre-scale water film over the surface of working electrodes and dual electrolyte/gas channels for in situ synchrotron FTIR tests. By coupling with a facile single-reflection infrared mode, a general in situ synchrotron radiation FTIR (SR-FTIR) spectroscopic method is developed for tracking the surface dynamics of catalysts during the electrocatalytic process. As an example, in situ formed key *OOH is clearly observed on the surface of commercial benchmark IrO2 catalysts during the electrochemical oxygen evolution process based on the developed in situ SR-FTIR spectroscopic method, which demonstrates its universality and feasibility in surface dynamics studies of electrocatalysts under working conditions.

Characterization of freeze-dried oxidized human red blood cells for pre-transfusion testing by synchrotron FTIR microspectroscopy live-cell analysis.

Oxidative treatment of human red blood cells (RBCs) prior to freeze-drying appears to stabilize the RBCs to withstand dried storage at room temperature. To better understand the effects of oxidation and freeze-drying/rehydration on RBC lipids and proteins, single-cell measurements were performed by synchrotron-based Fourier transform infrared (FTIR) microspectroscopy 'live-cell' (unfixed) analysis. Lipid and protein spectral data of tert-butyl hydroperoxide (TBHP)-oxidized RBCs (oxRBCs), FDoxRBCs and control (untreated) RBCs were compared using principal component analysis (PCA) and band integration ratios. The oxRBCs and FDoxRBCs samples had similar spectral profiles that were clearly different to control RBCs. Spectral changes in the CH stretching region of oxRBCs and FDoxRBCs indicated the presence of increased saturated and shorter-chain lipids, consistent with lipid peroxidation and stiffening of the RBC membrane compared to control RBCs. The PCA loadings plot for the fingerprint region of control RBCs corresponding to the α-helical structure of hemoglobin, shows that oxRBCs and FDoxRBCs have conformational changes in the protein secondary structure to β-pleated sheets and β-turns. Finally, the freeze-drying process did not appear to compound or induce additional changes. In this context, FDoxRBCs could become a stable source of reagent RBCs for pre-transfusion blood serology testing. The synchrotron FTIR microspectroscopic live-cell protocol provides a powerful analytical tool to characterize and contrast the effects of different treatments on RBC chemical composition at the single cell level.

Mass spectrometry and synchrotron-FTIR microspectroscopy reveal the anti-inflammatory activity of Bua Bok extracts.

Bua Bok or Centella asiatica (CA) is an Asian vegetable with anti-inflammatory benefits. Asiaticoside, asiatic acid, madecassoside and madecassic have been characterised as major active ingredients with a wide range of pharmacological advantages. In manufacturing processes, high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LCMS) are used to routinely determine the active compounds in raw materials. This research aims to explore anti-inflammatory properties, characterise metabolites and observe the biochemical changes of the inflammatory induced macrophages after pretreatment with the potential extracted fractions. Bua Bok leaf extracts were prepared. Macrophages were pretreated with non-toxic fractions to determine the anti-inflammatory action. Tentative metabolites of effective fractions were identified by LC-MS. Synchrotron fourier-transform infrared (S-FTIR) microspectroscopy was utilised to observe the biochemical change of the lipopolysaccharide (LPS)-induced cells after pretreatment with potential fractions. Fractions of ethyl acetate, 30% and 100% ethanol highly increased the nitrile scavenging and suppressed the function of phospholipase A2 . Fractions of 70% and 100% ethanol strongly decreased nitric oxide production. The comparison of 39 chemical compounds was presented. The change of proteins was improved after pretreatment of macrophages with fraction 70% ethanol. Fraction of 100% ethanol revealed the lipid accumulation was lower than 70% ethanol and diclofenac. While the anti-inflammatory actions of 70% and 100% ethanol were similar. S-FTIR expressed they inhibited inflammatory response with the distinct features of biomolecules. The S-FTIR, LC-MS and biological assay confidently provided the efficient strategies to inform the advantage of herbal extract on cellular organisation instead of a single compound.

Cation-Vacancy-Enriched Nickel Phosphide for Efficient Electrosynthesis of Hydrogen Peroxides.

Electrocatalytic hydrogen peroxide (H2 O2 ) synthesis via the two-electron oxygen reduction reaction (2e ORR) pathway is becoming increasingly important due to the green production process. Here, cationic vacancies on nickel phosphide, as a proof-of-concept to regulate the catalyst's physicochemical properties, are introduced for efficient H2 O2 electrosynthesis. The as-fabricated Ni cationic vacancies (VNi )-enriched Ni2- x P-VNi electrocatalyst exhibits remarkable 2e ORR performance with H2 O2 molar fraction of >95% and Faradaic efficiencies of >90% in all pH conditions under a wide range of applied potentials. Impressively, the as-created VNi possesses superb long-term durability for over 50 h, suppassing all the recently reported catalysts for H2 O2 electrosynthesis. Operando X-ray absorption near-edge spectroscopy (XANES) and synchrotron Fourier transform infrared (SR-FTIR) combining theoretical calculations reveal that the excellent catalytic performance originates from the VNi -induced geometric and electronic structural optimization, thus promoting oxygen adsorption to the 2e ORR favored "end-on" configuration. It is believed that the demonstrated cation vacancy engineering is an effective strategy toward creating active heterogeneous catalysts with atomic precision.

Investigating the molecular structure of plasma in type 2 diabetes mellitus and diabetic nephropathy by synchrotron Fourier-transform infrared microspectroscopy

Diabetes mellitus (DM) is associated with a high incidence of morbidity and mortality which, in many cases, is derived from the progressive kidney dysfunction due to diabetic nephropathy (DN). In this study, synchrotron-Fourier-transform infrared (SR-FTIR) microspectroscopy was used to identify molecular changes in the lipid and protein regions in the plasma of patients with different stages of DN (mild, moderate, severe and end-stage), and patients with type 2 diabetes mellitus (T2DM) without DN. Our results revealed different conformational changes in the proteins secondary structure between DN stages, and between DN and T2DM groups illustrated by peak shifts and intensity alterations. End-stage DN showed the highest CH2/CH3 ratio and intensity of the carbonyl group in protein-carbonyl region compared to other DN stages indicating high level of unsaturation and lipid peroxidation and oxidation conditions. Moreover, end-stage DN group was characterized by a decrease in amide I and amide II absorption signals which reflected a sign of hypoalbuminemia. When compared to T2DM, DN group demonstrated a higher oxidation state as confirmed via the high intensity of the carbonyl group and the high level of malondialdehyde. The current study highlights the promising role of SR-FTIR microspectroscopy as a new sensitive analytical approach that can be used to provide better understanding of the pathophysiology of DN, and guide the development of new preventive therapies and treatments.

Tracking biochemical changes induced by iron loading in AML12 cells with synchrotron live cell, time-lapse infrared microscopy

Hepatocytes are essential for maintaining the homeostasis of iron and lipid metabolism in mammals. Dysregulation of either iron or lipids has been linked with serious health consequences, including non-alcoholic fatty liver disease (NAFLD). Considered the hepatic manifestation of metabolic syndrome, NAFLD is characterised by dysregulated lipid metabolism leading to a lipid storage phenotype. Mild to moderate increases in hepatic iron have been observed in ∼30% of individuals with NAFLD; however, direct observation of the mechanism behind this increase has remained elusive. To address this issue, we sought to determine the metabolic consequences of iron loading on cellular metabolism using live cell, time-lapse Fourier transform infrared (FTIR) microscopy utilising a synchrotron radiation source to track biochemical changes. The use of synchrotron FTIR is non-destructive and label-free, and allowed observation of spatially resolved, sub-cellular biochemical changes over a period of 8 h. Using this approach, we have demonstrated that iron loading in AML12 cells induced perturbation of lipid metabolism congruent with steatosis development. Iron-loaded cells had approximately three times higher relative ester carbonyl concentration compared with controls, indicating an accumulation of triglycerides. The methylene/methyl ratio qualitatively suggests the acyl chain length of fatty acids in iron-loaded cells increased over the 8 h period of monitoring compared with a reduction observed in the control cells. Our findings provide direct evidence that mild to moderate iron loading in hepatocytes drives de novo lipid synthesis, consistent with a role for iron in the initial hepatic lipid accumulation that leads to the development of hepatic steatosis.

Monitoring the Progression of Liver Fluke-Induced Cholangiocarcinoma in a Hamster Model Using Synchrotron FTIR Microspectroscopy and Focal Plane Array Infrared Imaging.

Cholangiocarcinoma (CCA) is a bile duct cancer that originates in the bile duct epithelium. Northeastern Thailand has the highest incidence of CCA, and there is a direct correlation with liver fluke (Opisthorchis viverrini) infection. The high mortality rate of CCA is a consequence of delayed diagnosis. Fourier transform infrared (FTIR) spectroscopy is a powerful technique that detects the absorbance of molecular vibrations and is perfectly suited for the interrogation of biological samples. In this study, we applied synchrotron radiation-FTIR (SR-FTIR) microspectroscopy and focal plane array (FPA-FTIR) microspectroscopy to characterize periductal fibrosis and bile duct cells progressing to CCA induced by inoculating O. viverrini metacercariae into hamsters. SR-FTIR and FPA-FTIR measurements were performed in liver sections harvested from 1-, 2-, 3-, and 6-month post-infected hamsters compared to uninfected liver tissues. Principal component analysis (PCA) of the tissue samples showed a clear discrimination among uninfected and early-stage (1 and 2 months) and cancerous-stage (3 and 6 months) tissues. The discrimination is based on intensity changes in the phosphodiester band (1081 cm-1), amino acid residue (∼1396 cm-1), and C═O stretching carboxylic esters (1745 cm-1). Infected tissues also show definitive bands at ∼1280, 1234, and 1201 cm-1 characteristic of the collagen triplet and indicative of fibrosis. Hierarchical cluster analysis (HCA) was performed on the FPA data and showed a classification into specific cell types. Hepatocyte, fibrotic lesion, and bile duct (cancer) were classified and HCA mapping showed similar cellular distribution pattern compared to Sirius red staining. This study was also extended to less invasive sample analysis using attenuated total reflectance-FTIR (ATR-FTIR) spectroscopy. Sera from O. viverrini-infected and uninfected hamsters were analyzed using multivariate analysis, including principal component analysis (PCA), and partial least squares-discriminant analysis (PLS-DA). PCA was able to classify spectra of normal, early-stage CCA, and CCA, while the PLS-DA gave 100% accuracy for the validation. The model was established from 17 samples (11 normal, 6 cancer) in the calibration set and 9 samples in the validation set (4 normal, 2 cancer, 3 precancerous). These results indicate that FTIR-based technology is a potential tool to detect the progression of CCA, especially in the early stages of the disease.

Investigation of molecular mechanisms of experimental compounds in murine models of chronic allergic airways disease using synchrotron Fourier-transform infrared microspectroscopy

The ovalbumin-induced (OVA) chronic allergic airways murine model is a well-established model for investigating pre-clinical therapies for chronic allergic airways diseases, such as asthma. Here, we examined the effects of several experimental compounds with potential anti-asthmatic effects including resveratrol (RV), relaxin (RLN), l-sulforaphane (LSF), valproic acid (VPA), and trichostatin A (TSA) using both a prevention and reversal model of chronic allergic airways disease. We undertook a novel analytical approach using focal plane array (FPA) and synchrotron Fourier-transform infrared (S-FTIR) microspectroscopic techniques to provide new insights into the mechanisms of action of these experimental compounds. Apart from the typical biological effects, S-FTIR microspectroscopy was able to detect changes in nucleic acids and protein acetylation. Further, we validated the reduction in collagen deposition induced by each experimental compound evaluated. Although this has previously been observed with conventional histological methods, the S-FTIR technique has the advantage of allowing identification of the type of collagen present. More generally, our findings highlight the potential utility of S-FTIR and FPA-FTIR imaging techniques in enabling a better mechanistic understanding of novel asthma therapeutics.

The effect of pH on the fat and protein within cream cheese and their influence on textural and rheological properties.

The effect of variation in acid gel pH during cream cheese production was investigated. The gel microstructure was denser and cheese texture firmer, as the pH decreased from pH 5.0 to pH 4.3, despite the viscoelasticity of these gels remaining similar during heating. Protein hydration and secondary structure appeared to be key factors affecting both cheese microstructure and properties. Proteins within the matrix appeared to swell at pH 5.0, leading to a larger corpuscular structure; greater β-turn structure was also observed by synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy and the cheese was softer. A decrease in pH led to a denser microstructure with increased aggregated β-sheet structure and a firmer cheese. The higher whey protein loss at low pH likely contributed to increased cheese hardness. In summary, controlling the pH of acid gel is important, as this parameter affects proteins in the cheese, their secondary structure and the resulting cream cheese.

Direct Observation of Native Silk Fibroin Conformation in Silk Gland of Bombyx mori Silkworm.

To understand the natural silk spinning mechanism, synchrotron Fourier transform infrared (S-FTIR) microspectroscopy was employed in this study to monitor the conformation changes of silk protein in the silk gland of Bombyx mori silkworm. The ultrahigh brightness of S-FTIR microspectroscopy allowed the imaging of the silk gland with micrometer-scale spatial resolution. Herein, tissue sections of a silk gland, including cross-section slices and longitudinal-section slices, were characterized. The results obtained clearly confirm that the conformation of the silk fibroin changes gradually along the silk gland from the tail to the spinneret. In the middle silk gland, silk fibroin mainly contains random coil/helix conformation. When it comes to the spinneret through the anterior silk gland, the content of β-sheet increases, but the content of random coil/helix instead reduces gradually. Further, the β-sheet distribution in the cross-section of the anterior silk gland was imaged using S-FTIR mapping technique. The results show that the structural distribution of the silk fibroin in cross-section is uniform without significant shell-core structure, which implies that the primary driving force to induce the conformation transition of silk fibroin from random coil/helix to β-sheet during the spinning process is elongational flow of silk fibroin in the silk gland and not the shear force between the silk fibroin and the lumen wall of silk gland. These direct pieces of evidence of silk fibroin structure in the silk gland would definitely promote a deeper understanding of the natural spinning process.

Effect of stress on the molecular structure and mechanical properties of supercontracted spider dragline silks.

Supercontraction is one of the most interesting properties of spider dragline silks. In this study, changes in the secondary structures of the Nephila edulis spider dragline silk after it was subjected to different supercontraction processes were investigated by integrating synchrotron Fourier transform infrared (S-FTIR) microspectroscopy and mechanical characterization. The results showed that after free supercontraction, the β-sheet lost most of its orientation, while the helix and random coils were almost totally disordered. Interestingly, by conducting different types of supercontractions (i.e., stretching of the free supercontracted spider dragline silk to its original length or performing constrained supercontraction), it was found that although the molecular structures all changed after supercontraction, the mechanical properties almost remained unchanged when the length of the spider dragline silk did not change significantly. The other interesting conclusion obtained is that the manual stretching of a poorly oriented spider dragline silk cannot selectively improve the orientation degree of the β-sheet in the spider silk, but increase the orientation degree of all conformations (β-sheet, helix, and random). These experimental findings not only help to unveil the structure-property-function relationship of natural spider silks, but also provide a useful guideline for the design of biomimetic spider fiber materials.

Synchrotron FTIR spectromicroscopy as a tool for studying populations and individual living cells of green algae.

Fourier transform infrared (FTIR) spectromicroscopy was used to study individual living cells of three closely-related species of the green algal genus Chlamydomonas. Three types of spectral variation were observed between individual cells within a single culture, as well as between different cultures: variation around a mean, individual outliers, and the presence of subpopulations. By understanding and controlling this variation, we were able to spectroscopically differentiate between the three closely-related species. Spectral differences were confirmed using principal component analysis, leading to an understanding of the biochemical differences between species. This work highlights the additional information obtained by studying individual cells, and has implications for more traditional bulk measurements.

Synthesis and characterisation of isothiocyanate functionalised silicon nanoparticles and their uptake in cultured colonic cells.

The functionalisation of silicon nanoparticles with a terminal thiocyanate group, producing isothiocyanate-capped silicon nanoparticles (ITC-capped SiNPs) has been successfully attained. The procedure for the synthesis is a two-step process that occurs via thermally induced hydrosilylation of hydrogen terminated silicon nanoparticles (H-SiNPs) and further reaction with potassium thiocyanate (KSCN). The synthesis was confirmed by Fourier transform infrared (FTIR) spectroscopy and X-Ray photoelectron spectroscopy (XPS). At the same time, the internalisation and the cytotoxicity of the ITC-capped SiNPs in vitro were assessed in two cell lines: Caco-2, human colorectal cancer cells and CCD-841, human colon "normal" cells. The results showed that above concentrations of 15 µg ml-1, the cell viability of both cell lines was depleted significantly when treated with ITC SiNPs, particularly over a 48 hour period, to approximately 20% cell viability at the highest treatment concentration (70 µg ml-1). Flow cytometry was employed to determine cellular uptake in Caco-2 cells treated with ITC SiNPs. It was observed that at lower SiNP concentrations, uptake efficiency was significantly improved for time periods under 12 hours; overall it was noted that cellular uptake was positively dependent on the period of incubation and the temperature of incubation. As such, it was concluded that the mechanism of uptake of ITC SiNPs was through endocytosis. Synchrotron FTIR spectroscopy, by means of line spectral analysis and IR imaging, provided further evidence to suggest the internalisation of ITC SiNPs displays a strong localisation, with an affinity for the nucleus of treated Caco-2 cells.

Interfacial chemistry of a fly ash geopolymer and aggregates

The environmental and accessibility concerns associated with the increasing use of river sand in construction have diverted the attention of scientists to alternative materials. Waste glass has been widely investigated as a replacement for sand in geopolymer concretes, and the chemical and mechanical properties of the resulting materials are investigated. Since glass is rich in amorphous silica, it is believed that the surface of glass aggregates can take part in the reaction and make a stronger geopolymer matrix compared to that of sand aggregates. An improvement of 30% in compressive strength was obtained by replacing sand aggregates with glass aggregates. While the mechanical properties support interfacial reaction with glass aggregates, the nature of the chemical bonding structure at the interface has not been revealed. In this research, synchrotron Fourier transform infrared (SR-FTIR) microspectroscopy has been used for the first time to map the distribution of the chemical bonding structures at the geopolymer interface with aggregates. While in-situ FTIR shows the development of geopolymer gel over time, SR-FTIR results show clear differences in gel chemistry around the glass compared to the sand. The study reveals that there is a relatively higher degree of silica-rich gels close to the sand aggregates and a higher extent of geopolymeric gels around glass aggregates. The alkaline content of glass makes the area surrounding the glass aggregates more suitable for maintaining monomeric silica. These small silica species help to develop a higher degree of geopolymer networks in the vicinity of the glass aggregates compared to the sand. This level of visibility is very useful for understanding the behaviour of geopolymer concretes, which is critically important for nano-engineering of materials towards a desirable distribution of the binding gels.

Synchrotron-Based Infra-Red Spectroscopic Insights on Thermo-Catalytic Conversion of Cellulosic Feedstock to Levoglucosenone and Furans.

Thermo-catalytic conversion of cellulosic feedstock, such as lignocellulose, to platform chemicals offers a renewable alternative to fossil-based chemicals. Mechanistic insights behind thermochemical conversion of lignocellulose would facilitate thermo-catalytic process development for bio-based chemicals. This study employed synchrotron-based Fourier transform infrared (FTIR) microspectroscopy to investigate chemical changes in acid-catalyzed cellulose and lignocellulose and glucose during pyrolysis. Major changes in glucose occurred at 200 °C, where it underwent reactions including ring opening and tautomerization. Acid treatment did not change the molecular structure of cellulose but disrupted the lignocellulose network. The observed synchrotron FTIR spectral features provided evidence for acceleration of catalytic dehydration of cellulose and lignocellulose to levoglucosenone and furans. Catalytic passivation of alkali and alkaline earth metals in lignocellulose was also observed at low acid concentration.

Analysis of xanthyletin and secondary metabolites from Pseudomonas stutzeri ST1302 and Klebsiella pneumoniae ST2501 against Pythium insidiosum

BackgroundPythium insidiosum is a member of the oomycetes class of aquatic fungus-like microorganisms. It can infect humans and animals through skin wounds and the eyes, causing pythiosis, an infectious disease with high morbidity and mortality rates. Antifungal agents are ineffective as pythiosis treatments because ergosterol, the target site of most antifungal agents, is not found in the P. insidiosum cytoplasmic membrane. The best choice for treatment is surgical removal of the infected organ. While natural plant products or secretory substances from bacterial flora have exhibited in vitro anti-P. insidiosum activity, their mechanism of action remains unknown. Therefore, this study hypothesized that the mechanism of action could be related to changes in P. insidiosum biochemical composition (such as lipid, carbohydrate, protein or nucleic acid) following exposure to the inhibitory substances. The biochemical composition of P. insidiosum was investigated by Synchrotron radiation-based Fourier-transform infrared (FTIR) microspectroscopy.ResultsFraction No.6 from the crude extract of P. stutzeri ST1302, fraction No.1 from the crude extract of K. pneumoniae ST2501 and xanthyletin were used as anti-P. insidiosum substances, with MFCs at 3.125, 1.57–1.91, 0.003 mg/ml, respectively. The synchrotron FTIR results show that the deconvoluted peak distributions in the amide I, amide II, and mixed regions were significantly different between the treatment and control groups.ConclusionsXanthyletin and the secondary metabolites from P. stutzeri ST1302 and K. pneumoniae ST2501 exerted anti-P. insidiosum activity that clearly changed the proteins in P. insidiosum. Further study, including proteomics analysis and in vivo susceptibility testing, should be undertaken to develop a better understanding of the mechanism of anti-P. insidiosum activity.

The characterisation of Mozzarella cheese microstructure using high resolution synchrotron transmission and ATR-FTIR microspectroscopy

Synchrotron Fourier transform infrared (S-FTIR) microspectroscopy allows the label-free examination of material microstructure but has not been widely applied to dairy products. Here, S-FTIR microspectroscopy was applied to observe the microstructure of Mozzarella cheese and assess the protein and lipid distribution within individual cheese blocks. High lipid and high protein areas were identified in transmission and attenuated total reflectance (ATR) analysis modes and the secondary structures of cheese proteins determined. Hierarchical cluster analysis and principal component analysis identified variation in random coil, water content, lipid carbonyl and methylene stretching across the sampled area. Similar spectral features were obtained in both analysis modes; spatial resolution was higher with ATR and small differences were noted, potentially as a result of differences in sample preparation. S-FTIR is a useful microscopy tool that can detect structural alterations that may affect product properties and may assist reverse engineering of a range of dairy products.

Observation of Mie ripples in the synchrotron Fourier transform infrared spectra of spheroidal pollen grains

Conceptually, biological cells are dielectric, photonic resonators that are expected to show a rich variety of shape resonances when exposed to electromagnetic radiation. For spheroidal cells, these shape resonances may be predicted and analyzed using the Mie theory of dielectric spheres, which predicts that a special class of resonances, i.e., whispering gallery modes (WGMs), causes ripples in the absorbance spectra of spheroidal cells. Indeed, the first tentative indication of the presence of Mie ripples in the synchrotron Fourier transform infrared (SFTIR) absorbance spectra of Juniperus chinensis pollen has already been reported [Analyst140, 3273 (2015)ANLYAG0365-488510.1039/C5AN00401B]. To show that this observation is no isolated incidence, but a generic spectral feature that can be expected to occur in all spheroidal biological cells, we measured and analyzed the SFTIR absorbance spectra of Cunninghamia lanceolata, Juniperus chinensis, Juniperus communis, and Juniperus excelsa. All four pollen species show Mie ripples. Since the WGMs causing the ripples are surface modes, we propose ripple spectroscopy as a powerful tool for studying the surface properties of spheroidal biological cells. In addition, our paper draws attention to the fact that shape resonances need to be taken into account when analyzing (S)FTIR spectra of isolated biological cells since shape resonances may distort the shape or mimic the presence of chemical absorption bands.

Investigation of oil distribution in spray-dried chia seed oil microcapsules using synchrotron-FTIR microspectroscopy

In this study, chia seed oil (CSO) microcapsules were produced using three types of shell materials, including chia seed protein (CPI), chia seed gum (CSG) and CPI-CSG complex coacervates. Synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy was used to investigate the effect of shell materials on the distribution of CSO both on the surface and in the interior of the solid microcapsules. S-FTIR measurements were carried out in macroscopic attenuated total reflection (macro ATR) and transmission modes, to determine the surface lipid and the encapsulated lipid fractions, respectively. The amounts of lipid and protein distributed on the surface and in the interior of the microcapsules were compared based on the average spectra extracted from S-FTIR chemical images obtained from each type of the microcapsules. The unsaturated fatty acids (UFAs) to total oil ratios in all the three types of the microcapsules were closely similar to the original non-processed CSO, suggesting an effective encapsulation and thereby shielding protection of UFAs from oxidative damage during microencapsulation process. The type of the shell materials was found to affect the distribution of CSO on the surface and within the microcapsules. The complex coacervation based microcapsules had a significantly lower oil content (∼2% w/w) on the surface compared to those observed for the other two types of microcapsules (>5%, w/w).