Application of second derivative spectroscopy for increasing molecular specificity of Fourier transform infrared spectroscopic imaging of articular cartilage

Full model selection using regression trees for numeric predictions of biomarkers for metabolic challenges in dairy cows

Dairy cows suffer poor metabolic adaptation syndrome (PMAS)¹ during early post-calving periods caused by negative energy balance. Measurement of blood beta-hydroxy butyric acid (BHBA)² and blood non-esterified fatty acids (NEFA)³ allow early and accurate detection of negative energy balance. Machine learning prediction of blood BHBA and blood NEFA using milk testing samples represents an opportunity to identify at-risk animals, using less labor than direct blood testing methods. Routine milk testing on modern dairies and computer record keeping provide an immense amount of data which can then be used in machine learning models. Previous research for predicting blood metabolites using Fourier-transform infrared spectroscopy (FTIR)⁴ milk data has focused mainly on individual models rather than a comparison among the models. Full model selection is the process of comparing different combinations of pre-processing methods, variable selection, and statistical learning algorithms to determine which model results in the lowest prediction error for a given dataset. For this project we used a full model selection approach with regression trees (rtFMS)⁵ . rtFMS uses the cross-validated performance of different model configurations to feed a regression tree for selecting a final model. A total of 384 possible model configurations (algorithms, predictors and data preprocessing options) for each outcome (blood BHBA and blood NEFA) were considered in the rtFMS technique. rtFMS allows direct comparison of multiple modeling approaches reducing bias due to empirical knowledge, modeling habits, or preferences, identifying the model with minimal root mean squared prediction error (RMSE)⁶ . An elastic net regression model was selected as the best performing model for both biomarkers. The input data for blood BHBA predictions were FTIR milk spectra, with a second derivative pre-processing, and a filter with 212 wave numbers, obtaining RMSE = 0.354 (0.328-0.392). The best performing model for blood NEFA had input data of FTIR milk spectra, with a second derivative pre-processing, and a filter with 212 wave numbers filter along with the time of milking, obtaining RMSE = 0.601 (0.564-0.654). The comparison of multiple modeling strategies, conducted by rtFMS, present an option for improved FTIR prediction models of blood BHBA and blood NEFA by reducing error due to human bias. The implementation of rtFMS to design future prediction models can guide model inputs and features. Our prediction models have the potential to increase early detection of metabolic disorders in dairy cows during the transition period.

Rapid detection of SARS-CoV-2 viral nucleic acids based on surface enhanced infrared absorption spectroscopy

Efficient point-of-care diagnosis of severe acute respiratory syndrome-corovavirus-2 (SARS-CoV-2) is crucial for the early control of novel coronavirus infections. At present, polymerase chain reaction (PCR) is primarily used to detect SARS-CoV-2. Despite the high sensitivity, the PCR process is time-consuming and complex which limits its applicability for rapid testing of large-scale outbreaks. Here, we propose a rapid and easy-to-implement approach for SARS-CoV-2 detection based on surface enhanced infrared absorption (SEIRA) spectroscopy. The evaporated gold nano-island films are used as SEIRA substrates which are functionalized with the single-stranded DNA probes for specific binding to selected SARS-CoV-2 genomic sequences. The infrared absorption spectra are analyzed using the principal component analysis method to identify the key characteristic differences between infected and control samples. The SEIRA-based biosensor demonstrates rapid detection of SARS-CoV-2, completing the detection of 1 μM viral nucleic acids within less than 5 min without any amplification. When combined with the recombinase polymerase amplification treatment, the detection capability of 2.98 copies per μL (5 aM) can be completed within 30 min. This approach provides a simple and economical alternative for COVID-19 diagnosis, which can be potentially useful in monitoring and controlling future pandemics in a timely manner.

Prediction of Crack Resistance of LFSMA-13 with and without Anti-Rut Agent Using Parameters of FTIR Spectrum under Different Aging Degrees

This paper aims to better analyze the crack resistance of lignin fiber reinforced SMA-13 (LFSMA-13) asphalt mixtures, with and without polymer anti-rut agent (ARA), under different aging degrees. IDEAL-CT test and Fourier transform infrared (FTIR) spectroscopy were utilized to analyze the relationships between the crack resistance of LFSMA-13, with and without ARA, and the parameters of the FTIR spectrum of the asphalt extracted from the test samples. A convenient testing method to predict the anti-crack ability of the mixtures in a road was also derived in this study. The test samples were prepared using the specifications listed by AASHTO. The fracture formation work (W_initial) and cracking index (CT_Index) in the IDEAL-CT test were adopted to reflect the cracking ability of the asphalt mixtures in both the crack formation stage and the crack propagation stage. The peak areas of the FTIR spectrum were utilized to reveal the chemical properties of the asphalt material inside the SMA-13 asphalt mixtures, with and without ARA under different aging degrees. Grey correlation analysis was adopted to choose the most suitable FTIR spectrum parameters to derive the prediction models of W_initial and CT_Index under different aging degrees. After conducting a series of tests, the results showed that the aging process could well affect the crack resistance of the test samples and the peak areas of the asphalt extracted from the mixtures. The FTIR parameters selected from the grey correlation analysis could be used to well predict the anti-crack ability of the asphalt mixtures.

Vibrational Spectroscopy in Assessment of Early Osteoarthritis-A Narrative Review

Osteoarthritis (OA) is a degenerative disease, and there is currently no effective medicine to cure it. Early prevention and treatment can effectively reduce the pain of OA patients and save costs. Therefore, it is necessary to diagnose OA at an early stage. There are various diagnostic methods for OA, but the methods applied to early diagnosis are limited. Ordinary optical diagnosis is confined to the surface, while laboratory tests, such as rheumatoid factor inspection and physical arthritis checks, are too trivial or time-consuming. Evidently, there is an urgent need to develop a rapid nondestructive detection method for the early diagnosis of OA. Vibrational spectroscopy is a rapid and nondestructive technique that has attracted much attention. In this review, near-infrared (NIR), infrared, (IR) and Raman spectroscopy were introduced to show their potential in early OA diagnosis. The basic principles were discussed first, and then the research progress to date was discussed, as well as its limitations and the direction of development. Finally, all methods were compared, and vibrational spectroscopy was demonstrated that it could be used as a promising tool for early OA diagnosis. This review provides theoretical support for the application and development of vibrational spectroscopy technology in OA diagnosis, providing a new strategy for the nondestructive and rapid diagnosis of arthritis and promoting the development and clinical application of a component-based molecular spectrum detection technology.

Discriminant Analysis of the Geographical Origin of Asian Red Pepper Powders Using Second-Derivative FT-IR Spectroscopy

This study aimed to discriminate between the geographical origins of Asian red pepper powders distributed in Korea using Fourier-transform infrared (FT-IR) spectroscopy coupled with multivariate statistical analyses. Second-derivative spectral data were obtained from a total of 105 red pepper powder samples, 86 of which were used for statistical analysis, and the remaining 19 were used for blind testing. A one-way analysis of variance (ANOVA) test confirmed that eight peak variables exhibited significant origin-dependent differences, and the canonical discriminant functions derived from these variables were used to correctly classify all the red pepper powder samples based on their origins. The applicability of the canonical discriminant functions was examined by performing a blind test wherein the origins of 19 new red pepper powder samples were correctly classified. For simplicity, the four most significant variables were selected as discriminant indicator variables, and the applicable range for each indicator variable was set for each geographical origin. By applying the indicator variable ranges, the origins of the red pepper powders of all the statistical and blind samples were correctly identified. The study findings indicate the feasibility of using FT-IR spectroscopy in combination with multivariate analysis for identifying the geographical origins of red pepper powders.

The potential of FT-IR spectroscopy for improving healthcare in sepsis - An animal model study

Fourier Transform-Infrared (FT-IR) absorption spectroscopy has been used to investigate pathophysiological changes caused by sepsis. Sepsis has been defined as a potentially fatal organic dysfunction caused by a dysregulated host response to infection and can lead a patient to risk of death. This study used samples consisting of the blood plasma of mice which were induced to sepsis state, compared to a healthy group using FT-IR associated with attenuated total reflectance (ATR) spectroscopy. For statistical analysis, principal components analysis (PCA) and linear discriminant analysis (LDA) were applied, independently, to the second derivative spectra of both the fingerprint (900-1800 cm^-1) and the high wavenumber (2800-3100 cm^-1) regions. The technique efficiently differentiated the blood plasma of the two groups, sepsis and healthy mice, the analysis indicating that fatty acids and lipids in the blood samples could be an important biomarker of sepsis.

Machine learning-augmented and microspectroscopy-informed multiparametric MRI for the non-invasive prediction of articular cartilage composition

BACKGROUND

Articular cartilage degeneration is the hallmark change of osteoarthritis, a severely disabling disease with high prevalence and considerable socioeconomic and individual burden. Early, potentially reversible cartilage degeneration is characterized by distinct changes in cartilage composition and ultrastructure, while the tissue's morphology remains largely unaltered. Hence, early degenerative changes may not be diagnosed by clinical standard diagnostic tools.

METHODS

Against this background, this study introduces a novel method to determine the tissue composition non-invasively. Our method involves quantitative MRI parameters (i.e., T₁, T_1ρ, T₂ and [Formula: see text] maps), compositional reference measurements (i.e., microspectroscopically determined local proteoglycan [PG] and collagen [CO] contents) and machine learning techniques (i.e., artificial neural networks [ANNs] and multivariate linear models [MLMs]) on 17 histologically grossly intact human cartilage samples.

RESULTS

Accuracy and precision were higher in ANN-based predictions than in MLM-based predictions and moderate-to-strong correlations were found between measured and predicted compositional parameters.

CONCLUSION

Once trained for the clinical setting, advanced machine learning techniques, in particular ANNs, may be used to non-invasively determine compositional features of cartilage based on quantitative MRI parameters with potential implications for the diagnosis of (early) degeneration and for the monitoring of therapeutic outcomes.

Comparison of different protocols for demineralization of cortical bone

Bone is a biological composite material consisting of two main components: collagen and mineral. Collagen is the most abundant protein in vertebrates, which makes it of high clinical and scientific interest. In this paper, we compare the composition and structure of cortical bone demineralized using several protocols: ethylene-diamine-tetraacetic acid (EDTA), formic acid (CH₂O₂), hydrochloric acid (HCl), and HCl/EDTA mixture. The efficiencies of these four agents were investigated by assessing the remaining mineral quantities and collagen integrity with various experimental techniques. Raman spectroscopy results show that the bone demineralized by the CH₂O₂ agent has highest collagen quality parameter. The HCl/EDTA mixture removes the most mineral, but it affects the collagen secondary structure as amide II bands are shifted as observed by Fourier transform infrared spectroscopy. Thermogravimetric analysis reveals that HCl and EDTA are most effective in removing the mineral with bulk measurements. In summary, we conclude that HCl best demineralizes bone, leaving the well-preserved collagen structure in the shortest time. These findings guide on the best demineralization protocol to obtain high-quality collagen from bone for clinical and scientific applications.

High-throughput screening of oil fingerprint using FT-IR coupled with chemometrics

An important element of the oil spill emergency response is the ability to rapidly identify the properties of oil spilled. Chemometrics provides large numbers of multivariate analysis tools that allow for more extensive use of data. Fourier transformed infrared spectroscopy coupled with classification and prediction models such as partial least square (PLS) and PLS-DA (discriminant analysis) allows the rapid identification of oil type and characteristics. By searching for the maximum covariance with the variables of interest, PLS allows the visualization of relations between samples and variables. The framework of this study is based on two main steps: The first is classification of oil and the second is prediction of physicochemical properties. Separated into four main categories: crude, light fuel, heavy fuel, and lubricant, spectrums of 92 oils were calibrated to predict the oil type and physicochemical properties of 26 oils. The predictability and robustness of the model was further validated using weathered oil. The classification and prediction models have accuracy of >95%. Most of the PLS models have root mean square error of calibration and prediction ranging from 0.10-3.07 and 0.3-2.8, respectively. External cross validations using weathered oils showed high prediction accuracy (relative standard deviations <5%). By increasing the number of oil type and samples, this approach is a promising method and can be included as part of the oil spill fingerprinting protocols.

Vibrational Spectroscopic Analyses and Imaging of the Early Middle Ages Hemp Bast Fibres Recovered from Lake Sediments

Fourier Transform Infrared (FT-IR) spectroscopy and imaging combined with hierarchical cluster analysis (HCA) was applied to analyse biochemical properties of Early Middle Ages hemp (Cannabis sativa L.) bast fibres collected from lake bottom sediment of lake Słone. The examined plant macrofossil material constitutes residues of the hemp retting process that took place in the 7th–8th century. By comparison of three samples: untreated isolated bast fibres, and fibres incubated overnight at 4 and 37 °C, we were able to mimic the retting conditions. Using FT-IR qualitative and semi-quantitative assessment of the primary polysaccharides content, total protein content, and their spatial distribution was performed within the hemp fibres. The concentration of cellulose remained vastly unchanged, while the concentration of lignin and pectin was the highest in the untreated sample. The spatial distributions of compounds were heterogeneous in the untreated and 4 °C-incubated samples, and homogenous in the specimen processed at 37 °C. Interestingly, a higher amide content was detected in the latter sample indicating the highest degree of enzymatic degradation. In this study, we show that the spectroscopic methods allow for a non-destructive evaluation of biochemical composition of plant fibres without preparation, which can be an appropriate approach for studying ancient plant remains.

Applications of Vibrational Spectroscopy for Analysis of Connective Tissues

Advances in vibrational spectroscopy have propelled new insights into the molecular composition and structure of biological tissues. In this review, we discuss common modalities and techniques of vibrational spectroscopy, and present key examples to illustrate how they have been applied to enrich the assessment of connective tissues. In particular, we focus on applications of Fourier transform infrared (FTIR), near infrared (NIR) and Raman spectroscopy to assess cartilage and bone properties. We present strengths and limitations of each approach and discuss how the combination of spectrometers with microscopes (hyperspectral imaging) and fiber optic probes have greatly advanced their biomedical applications. We show how these modalities may be used to evaluate virtually any type of sample (ex vivo, in situ or in vivo) and how "spectral fingerprints" can be interpreted to quantify outcomes related to tissue composition and quality. We highlight the unparalleled advantage of vibrational spectroscopy as a label-free and often nondestructive approach to assess properties of the extracellular matrix (ECM) associated with normal, developing, aging, pathological and treated tissues. We believe this review will assist readers not only in better understanding applications of FTIR, NIR and Raman spectroscopy, but also in implementing these approaches for their own research projects.

Hierarchically Porous Biocatalytic MOF Microreactor as a Versatile Platform towards Enhanced Multienzyme and Cofactor-Dependent Biocatalysis

Metal-organic frameworks (MOFs) have recently emerged as excellent hosting matrices for enzyme immobilization, offering superior physical and chemical protection for biocatalytic reactions. However, for multienzyme and cofactor-dependent biocatalysis, the subtle orchestration of enzymes and cofactors is largely disrupted upon immobilizing in the rigid crystalline MOF network, which leads to a much reduced biocatalytic efficiency. Herein, we constructed hierarchically porous MOFs by controlled structural etching to enhance multienzyme and cofactor-dependent enzyme biocatalysis. The expanded size of the pores can provide sufficient space for accommodated enzymes to reorientate and spread within MOFs in their lower surface energy state as well as to decrease the inherent barriers to accelerate the diffusion rate of reactants and intermediates. Moreover, the developed hierarchically porous MOFs demonstrated outstanding tolerance to inhospitable surroundings and recyclability.

Linking structural and compositional changes in archaeological human bone collagen: an FTIR-ATR approach

Collagen is the main structural and most abundant protein in the human body, and it is routinely extracted and analysed in scientific archaeology. Its degree of preservation is, therefore, crucial and several approaches are used to determine it. Spectroscopic techniques provide a cost-effective, non-destructive method to investigate the molecular structure, especially when combined with multivariate statistics (chemometric approach). In this study, we used FTIR-ATR spectroscopy to characterise collagen extracted from skeletons recovered from necropoleis in NW Spain spanning from the Bronze Age to eighteenth century AD. Principal components analysis was performed on a selection of bands and structural equation models (SEM) were developed to relate the collagen quality indicators to collagen structural change. Four principal components represented: (i) Cp1, transformations of the backbone protein with a residual increase in proteoglycans; (ii) Cp2, protein transformations not accompanied by changes in proteoglycans abundance; (iii) Cp3, variations in aliphatic side chains and (iv) Cp4, absorption of the OH of carbohydrates and amide. Highly explanatory SEM models were obtained for the traditional collagen quality indicators (collagen yield, C, N, C:N), but no relationship was found between quality and δ¹³C and δ¹⁵N ratios. The observed decrease in C and N content and increase in C:N ratios is controlled by the degradation of protein backbone components and the relative preservation of carbon-rich compounds, proteoglycans and, to a lesser extent, aliphatic moieties. Our results suggest that FTIR-ATR is an ideal technique for collagen characterization/pre-screening for palaeodiet, mobility and radiocarbon research.

Characterization of organophosphatic brachiopod shells: spectroscopic assessment of collagen matrix and biomineral components

The shells of linguloid brachiopods such as Lingula and Discinisca are inorganic-organic nanocomposites with a mineral phase of calcium phosphate (Ca-phosphate). Collagen, the main extracellular matrix in Ca-phosphatic vertebrate skeletons, has not previously been clearly resolved at the molecular level in organophosphatic brachiopods. Here, modern and recently-alive linguliform brachiopod shells of Lingula and Discinisca have been studied by microRaman spectroscopy, Fourier transform infrared spectroscopy, field emission gun scanning electron microscopy, and thermal gravimetric analysis. For the first time, biomineralized collagen matrix and Ca-phosphate components were simultaneously identified, showing that the collagen matrix is an important moiety in organophosphatic brachiopod shells, in addition to prevalent chitin. Stabilized nanosized apatitic biominerals (up to ∼50 nm) permeate the framework of organic fibrils. There is a ∼2.5-fold higher wt% of carbonate (CO₃ ^2-) in Lingula versus Discinisca shells. Both microRaman spectroscopy and infrared spectra show transient amorphous Ca-phosphate and octacalcium phosphate components. For the first time, trivalent moieties at ∼1660 cm^-1 and divalent moieties at ∼1690 cm^-1 in the amide I spectral region were identified. These are related to collagen cross-links that are abundant in mineralized tissues, and could be important features in the biostructural and mechanical properties of Ca-phosphate shell biominerals. This work provides a critical new understanding of organophosphatic brachiopod shells, which are some of the earliest examples of biomineralization in still-living animals that appeared in the Cambrian radiation.

Determination and evaluation of secondary structure content derived from calcium-induced conformational changes in wild-type and mutant mnemiopsin 2 by synchrotron-based Fourier-transform infrared spectroscopy

Mnemiopsin 2 from a luminous ctenophore with two functional EF-hand motifs is a calcium-regulated photoprotein that is responsible for emitting a bright blue bioluminescence upon reacting with coelenterazine and calcium ions in Mnemiopsis leidyi. Synchrotron radiation-based Fourier-transform infrared (SR-FTIR) spectroscopy was applied to analyze the distribution of secondary structures, the conformational changes resulting from calcium binding and the structural stabilities in wild-type mnemiopsin 2, as well as its mutant type that possesses three EF-hand motifs. The distribution of secondary structures of these proteins indicates that mutant apo-mnemiopsin 2 has a more stable secondary structure than the wild-type. Analyses of the SR-FTIR spectra revealed that the conformational changes at the secondary structures of both mnemiopsin 2 depend on the calcium concentrations, such that the most noticeable changes in structures of wild-type and mutant mnemiopsin 2 occur at optimum concentrations 6 and 2 mM of calcium chloride, respectively. The addition of calcium to both proteins increases the proportions of their secondary structures in the amide I and II regions. The major amide I bands in the IR spectra of both mnemiopsin‑calcium complexes shift towards smaller wavenumbers, whereas their main amide II bands are identified at larger wavenumbers.

Astrocytes Are More Vulnerable than Neurons to Silicon Dioxide Nanoparticle Toxicity in Vitro

Some studies have shown that silicon dioxide nanoparticles (SiO₂-NPs) can reach different regions of the brain and cause toxicity; however, the consequences of SiO₂-NPs exposure on the diverse brain cell lineages is limited. We aimed to investigate the neurotoxic effects of SiO₂-NP (0–100 µg/mL) on rat astrocyte-rich cultures or neuron-rich cultures using scanning electron microscopy, Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR), FTIR microspectroscopy mapping (IQ mapping), and cell viability tests. SiO₂-NPs were amorphous particles and aggregated in saline and culture media. Both astrocytes and neurons treated with SiO₂-NPs showed alterations in cell morphology and changes in the IR spectral regions corresponding to nucleic acids, proteins, and lipids. The analysis by the second derivative revealed a significant decrease in the signal of the amide I (α-helix, parallel β-strand, and random coil) at the concentration of 10 µg/mL in astrocytes but not in neurons. IQ mapping confirmed changes in nucleic acids, proteins, and lipids in astrocytes; cell death was higher in astrocytes than in neurons (10–100 µg/mL). We conclude that astrocytes were more vulnerable than neurons to SiO₂-NPs toxicity. Therefore, the evaluation of human exposure to SiO₂-NPs and possible neurotoxic effects must be followed up.

Salt Cocrystal of Diclofenac Sodium-L-Proline: Structural, Pseudopolymorphism, and Pharmaceutics Performance Study

Previously, we have reported on a zwitterionic cocrystal of diclofenac acid and L-proline. However, the solubility of this multicomponent crystal was still lower than that of diclofenac sodium salt. Therefore, this study aimed to observe whether a multicomponent crystal could be produced from diclofenac sodium hydrate with the same coformer, L-proline, which was expected to improve the pharmaceutics performance. Methods involved screening, solid phase characterization, structure determination, stability, and in vitro pharmaceutical performance tests. First, a phase diagram screen was carried out to identify the molar ratio of the multicomponent crystal formation. Next, the single crystals were prepared by slow evaporation under two conditions, which yielded two forms: one was a rod-shape and the second was a flat-square form. The characterization by infrared spectroscopy, thermal analysis, and diffractometry confirmed the formation of the new phases. Finally, structural determination using single crystal X-ray diffraction analysis solved the new salt cocrystals as a stable diclofenac-sodium-proline-water (1:1:1:4) named NDPT (natrium diclofenac proline tetrahydrate), and unstable diclofenac-sodium-proline-water (1:1:1:1), named NDPM (natrium diclofenac proline monohydrate). The solubility and dissolution rate of these multicomponent crystals were superior to those of diclofenac sodium alone. The experimental results that this salt cocrystal is suitable for further development.

A Systematic Review on Classification, Identification, and Healing Process of Burn Wound Healing

Because of the intrinsic complexity, the classification of wounds is important for the diagnosis, management, and choosing the correct treatment based on wound type. Generally, burn injuries are classified as a class of wounds in which injury is caused by heat, cold, electricity, chemicals, friction, or radiation. On the other hand, wound healing is a complex process, and understanding the biological trend of this process and differences in the healing process of different wounds could reduce the possible risk in many cases and greatly reduce the future damage to the injured tissue and other organs. The aim of this review is to provide a general perspective for the burn wound location among the other types of injuries and summarizing as well as highlighting the differences of these types of wounds with emphasizing on factors affecting thereof.

Visualizing Different Crystalline States during the Infrared Imaging of Calcium Phosphates

Methods utilizing relatively simple mathematical operations during physical analyses to enable the visualization of otherwise invisible correlations and effects are of particular appeal to researchers and students in pedagogical settings. At the same time, discerning the amorphous phase from its crystalline counterpart in materials is challenging with the use of vibrational spectroscopy and is nowhere as straightforward as in phase composition analytical methods such as X-ray diffraction. A method is demonstrated for the use of first- and second-order differentiation of Fourier transform infrared spectra of calcium phosphates to distinguish their amorphous states from the crystalline ones based on the exact line positioning rather than on comparatively vaguer band broadening and splitting effects. The study utilizes a kinetic approach, focusing on the comparison of spectral features of amorphous precursors annealed in air at different temperatures and aged for different periods of time in an aqueous solution until transforming to one or a mixture of crystalline phases, including hydroxyapatite and α- and β-tricalcium phosphate. One of the findings challenges the concept of the nucleation lag time preceding the crystallization from amorphous precursors as a "dead" period and derives a finite degree of constructive changes occurring at the atomic scale in its course. The differential method for highlighting spectral differences depending on the sample crystallinity allows for monitoring in situ the process of conversion of the amorphous calcium phosphate phase to its crystalline analogue(s). One such method can be of practical significance for synthetic solid state chemists testing for the chemical stability and/or concentration of the reactive amorphous phase in these materials, but also for biologists measuring the maturity of bone and medical researchers evaluating its phase composition and, thus, the state of metabolic and mechanical stability.

Biomimetic polyvinyl alcohol/type II collagen hydrogels for cartilage tissue engineering

Type II collagen (Col-II) is one of the important organic components of the cartilage extracellular matrix (ECM). Such natural material is known for its good biocompatibility, but it could not provide a good supporting environment for seed cells due to its rapid degradation and poor strength. In the present work, different contents of Col-II were incorporated into porous polyvinyl alcohol (PVA) to fabricate porous PVA/Col-II composite hydrogels for cartilage tissue engineering. The results illustrate that, after incorporation of Col-II, the elasticity modulus of the composite hydrogels firstly increases, and then decreases (under moisture state). The elasticity modulus of PVA/Col-II (at the ratio of 1:1) hydrogels reaches 11 ± 1.7 KPa, about two-fold higher than pure PVA hydrogels (4.9 ± 0.6 KPa). Meanwhile, all hydrogels exhibit relatively high water content (> 95%) and porosity (> 75%). The degradation analysis indicates that Col-II incorporation induce a high degradation ratio of the composite hydrogels. Cell culture results show PVA/Col-II hydrogels have no negative effects on cells viability and proliferation. The PVA/Col-II hydrogels may possess a potential application in the field of articular cartilage tissue engineering and regeneration.

Autotrophic and Heterotrophic Growth Conditions Modify Biomolecole Production in the Microalga Galdieria sulphuraria (Cyanidiophyceae, Rhodophyta)

Algae have multiple similarities with fungi, with both belonging to the Thallophyte, a polyphyletic group of non-mobile organisms grouped together on the basis of similar characteristics, but not sharing a common ancestor. The main difference between algae and fungi is noted in their metabolism. In fact, although algae have chlorophyll-bearing thalloids and are autotrophic organisms, fungi lack chlorophyll and are heterotrophic, not able to synthesize their own nutrients. However, our studies have shown that the extremophilic microalga Galderia sulphuraria (GS) can also grow very well in heterotrophic conditions like fungi. This study was carried out using several approaches such as scanning electron microscope (SEM), gas chromatography/mass spectrometry (GC/MS), and infrared spectrophotometry (ATR-FTIR). Results showed that the GS, strain ACUF 064, cultured in autotrophic (AGS) and heterotrophic (HGS) conditions, produced different biomolecules. In particular, when grown in HGS, the algae (i) was 30% larger, with an increase in carbon mass that was 20% greater than AGS; (ii) produced higher quantities of stearic acid, oleic acid, monounsaturated fatty acids (MUFAs), and ergosterol; (iii) produced lower quantities of fatty acid methyl esters (FAMEs) such as methyl palmytate, and methyl linoleate, saturated fatty acids (SFAs), and poyliunsaturated fatty acids (PUFAs). ATR-FTIR and principal component analysis (PCA) statistical analysis confirmed that the macromolecular content of HGS was significantly different from AGS. The ability to produce different macromolecules by changing the trophic conditions may represent an interesting strategy to induce microalgae to produce different biomolecules that can find applications in several fields such as food, feed, nutraceutical, or energy production.

Pterostilbene administration improves the recovery potential of extremely low-frequency magnetic field in acute renal ischemia-reperfusion injury: an FTIR spectroscopic study

Renal ischemia-reperfusion (I/R) injury, one of the drastic outcomes of renal failure and organ transplantation, tends to deteriorate over time; therefore, noninvasive therapeutic strategies will avail the progression-free survival of the patients. Magnetic field has been proposed as a noninvasive treatment strategy; however, with recent scientific advances, many controversies have arisen regarding its efficacy. Pterostilbene, a natural analog of resveratrol, was documented to be effective in treatment of I/R injuries. This study aims to assess the acute therapeutic effects of combined extremely low-frequency magnetic field (ELF-MF) and pterostilbene treatment on renal I/R injury. After induction of renal I/R in Wistar rats, treatments of 50 Hz, 1 mT ELF-MF applied alone or in combination with pterostilbene were applied for 5 consecutive days. Kidney homogenates were analyzed by Fourier transform infrared spectroscopy. I/R injury resulted in an altered protein and lipid structure with the dominance of longer acyl chains; a slight decrease in lipid, protein, unsaturated lipid, and unsaturated/saturated lipid content; and an increase in membrane fluidity and lipid peroxidation in rat kidneys. Although ELF-MF treatment alone was not sufficient to restore all ischemia-induced alterations, the combined treatment strategy of pterostilbene administration in the presence of ELF-MF was successful and warrants further investigation.

Biochar bound urea boosts plant growth and reduces nitrogen leaching

Over use of N fertilizers, most commonly as urea, had been seriously concerned as a major source of radiative N (Nr) for severe environment impacts through leaching, volatilization, and N₂O emission from fertilized croplands. It had been well known that biochar could enhance N retention and use efficiency by crops in amended croplands. In this study, a granular biochar-mineral urea composite (Bio-MUC) was obtained by blending urea with green waste biochar supplemented with clay minerals of bentonite and sepiolite. This Bio-MUC material was firstly characterized by microscopic analyses with FTIR, SEM-EDS and STEM, subsequently tested for N leaching in water in column experiment and for N supply for maize in pot culture, compared to conventional urea fertilizer (UF). Microscopic analyses indicated binding of urea N to particle surfaces of biochar and clay minerals in the Bio-MUC composite. In the leaching experiment over 30 days, cumulative N release as NH₄⁺-N and of dissolved organic carbon (DOC) was significantly smaller by >70% and by 8% from the Bio-MUC than from UF. In pot culture with maize growing for 50 days, total fresh shoot was enhanced by 14% but fresh root by 25% under Bio-MUC compared to UF. This study suggested that N in the Bio-MUC was shown slow releasing in water but maize growth promoting in soil, relative to conventional urea. Such effect could be related mainly to N retention by binding to biochar/mineral surfaces and partly by carbon bonds of urea to biochar in the Bio-MUC. Therefore, biochar from agro-wastes could be used for blending urea as combined organo/mineral urea to replace mineral urea so as to reduce N use and impacts on global Nr. Of course, how such biochar combined urea would impact N process in soil-plant systems deserve further field studies.

Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis

Fourier transform infrared (FTIR) and Raman spectroscopic techniques were employed to analyze the biomolecular transitions and lipid accumulation in three freshwater green microalgal species, Monoraphidium contortum (M. contortum), Pseudomuriella sp. and Chlamydomonas sp. during various phases of their growth. Biomolecular transitions and lipid [hydrocarbons, triacylglycerides (TAGs)] accumulation within the microalgal cells were identified using second derivatives of the FTIR absorption spectroscopy. Second derivative analysis normalized and resolved the original spectra and led to the identification of smaller, overlapping bands. Both relative and absolute content of lipids were determined using the integrated band area. M. contortum exhibited higher accumulation of lipids than the other two species. The integrated band area of the vibrations from saturated (SFA) and unsaturated lipids (UFA) enabled quantification of fatty acids. The percentage of SFA and UFA was determined using GC, FTIR and Raman spectroscopy. From the spectral data, the order of increasing concentration of SFA among the three microalgal species was M. contortum > Chlamydomonas sp. >Pseudomuriella sp. The spectral results on fatty acids were consistent with the separation of lipids by gas chromatography. The results emphasized the significance of FTIR and Raman spectroscopic methods in monitoring the biomolecular transitions and rapid quantification of lipids, without the need for extraction of lipids.

Biochemical similarity between cultured chondrocytes and in situ chondrocytes by chemometric analysis from FTIR microspectroscopy

Background aims

Fourier Transform Infrared Micro-spectroscopy (FTIRM) is an emerging tool that obtains images with biochemical information of samples that are too small to be chemically analyzed by conventional Fourier transform infrared (FTIR) spectroscopy techniques. So, the central objective of this project was to study the biochemical similarity between articular and cultured chondrocytes by chemometric analysis from FTIRM.

Methods

Nine samples of knee articular cartilage were obtained; each sample was divided into two fragments, one portion was used for FTIRM characterization in situ, and from another part, chondrocytes were obtained to be cultured (in vitro), which were subjected to an FTIRM to characterize their biomolecular components. The FTIRM spectra were normalized, and the second derivative was calculated. From these data, principal component analysis (PCA) and a chemometric comparison between in situ and cultured chondrocytes were carried out. Finally, the biochemical mapping was conducted obtaining micro-FTIR imaging.

Results

FTIRM spectra of in situ and in vitro chondrocytes were obtained, and different biomolecules were detected, highlighting lipids, proteins, glycosaminoglycans, collagen, and aggrecan. Despite slight differences in the FTIR spectra, the PCA proved the organic similarity between in situ chondrocytes and cultured chondrocytes, which was also observed in the analysis of the ratios related to the degradation of the articular cartilage and collagen. In the same way, the ability of the FTIRM to characterize the molecular biodistribution was demonstrated.

Conclusion

The biochemical composition and biodistribution analysis using FTIRM have been useful for comparing cultured chondrocytes and in situ chondrocytes.

Histochemical quantification of collagen content in articular cartilage

Background

Articular cartilage (AC) is mainly composed of water, type II collagen, proteoglycans (PGs) and chondrocytes. The amount of PGs in AC is routinely quantified with digital densitometry (DD) from Safranin O-stained sections, but it is unclear whether similar method could be used for collagens.

Objective

The aim of this study was to clarify whether collagens can be quantified from histological AC sections using DD.

Material and methods

Sixteen human AC samples were stained with Masson’s trichrome or Picrosirius red. Optical densities of histological stains were compared to two commonly used collagen parameters (amide I and collagen CH₂ side chain peak at 1338cm^-1) measured using Fourier Transform Infrared (FTIR) spectroscopic imaging.

Results

Optical density of Modified Masson’s trichrome staining, which included enzymatic removal of PGs before staining, correlated significantly with FTIR-derived collagen parameters at almost all depths of cartilage. The other studied staining protocols displayed significant correlations with the reference parameters at only few depth layers.

Conclusions

Based on our findings, modified Masson’s trichrome staining protocol is suitable for quantification of AC collagen content. Enzymatic removal of PGs prior to staining is critical as us allows better staining of the collagen. Further optimization of staining protocols may improve the results in the future studies.

The use of Fourier-transform infrared spectroscopy to characterize connective tissue components in skeletal muscle of Atlantic cod (Gadus morhua L.)

In the present study, Fourier-transform infrared spectroscopy (FTIR) is investigated as a method to measure connective tissue components that are important for the quality of Atlantic cod filets (Gadus morhua L.). The Atlantic cod used in this study originated from a feeding trial, which found that fish fed a high starch diet contained relative more collagen type I, while fish fed a low starch (LS) diet contained relative more glycosaminoglycans (GAGs) in the connective tissue. FTIR spectra of pure commercial collagen type I and GAGs were acquired to identify spectral markers and compare them with FTIR spectra and images from connective tissue. Using principal component analysis, high and LS diets were separated due to collagen type I in the spectral region 1800 to 800 cm-1 . The spatial distribution of collagen type I and GAGs were further investigated by FTIR imaging in combination with immunohistochemistry. Pixel-wise correlation images were calculated between preprocessed connective tissue images and preprocessed pure components spectra of collagen type I and GAGs, respectively. For collagen, the FTIR images reveal a collagen distribution that closely resembles the collagen distribution as imaged by immunohistochemistry. For GAGs, the concentration is very low. Still, the FTIR images detect the most GAGs rich regions.

Dataset on equine cartilage near infrared spectra, composition, and functional properties

Near infrared (NIR) spectroscopy is a well-established technique that is widely employed in agriculture, chemometrics, and pharmaceutical engineering. Recently, the technique has shown potential in clinical orthopaedic applications, for example, assisting in the diagnosis of various knee-related diseases (e.g., osteoarthritis) and their pathologies. NIR spectroscopy (NIRS) could be especially useful for determining the integrity and condition of articular cartilage, as the current arthroscopic diagnostics is subjective and unreliable. In this work, we present an extensive dataset of NIRS measurements for evaluating the condition, mechanical properties, structure, and composition of equine articular cartilage. The dataset contains NIRS measurements from 869 different locations across the articular surfaces of five equine fetlock joints. A comprehensive library of reference values for each measurement location is also provided, including results from a mechanical indentation testing, digital densitometry imaging, polarized light microscopy, and Fourier transform infrared spectroscopy. The published data can either be used as a model of human cartilage or to advance equine veterinary research.

Fourier transform infrared spectroscopy research on subchondral bone in osteoarthritis

Osteoarthritis (OA) is not only related to the degradation of articular cartilage, but also possibly to the changes of subchondral bone. The purpose of this study was to assess whether specific differences could be resolved from bone composition, as also contributed to OA. These differences were assessed by using Fourier transform infrared spectroscopy (FTIRS). The main parameters including mineral content, carbonate content, crystallinity, collagen cross-linking ratio (XLR) and acid phosphate content were represented with characteristic peak integration. It was found that mineral and carbonate content varied significantly with depths at different OA stages. Mineral content increased with depth in healthy samples, while carbonate content showed opposite trend. The mineral content reduced obviously with OA duration, which was different with carbonate decreasing only at early stage of OA. In addition, the content of acid phosphate, collagen maturity (XLR) and crystallinity slight varied with the OA aggravation. Therefore, the changes in subchondral bone were significantly associated with cartilage degeneration and OA, the associated parameters should be targeted for OA therapies.

Understanding Secondary Structures of Silk Materials via Micro- and Nano-Infrared Spectroscopies

The secondary structures (also termed conformations) of silk fibroin (SF) in animal silk fibers and regenerated SF materials are critical in determining mechanical performance and function of the materials. In order to understand the structure-mechanics-function relationships of silk materials, a variety of advanced infrared spectroscopic techniques, such as micro-infrared spectroscopies (micro-IR spectroscopies for short), synchrotron micro-IR spectroscopy, and nano-infrared spectroscopies (nano-IR spectroscopies for short), have been used to determine the conformations of SF in silk materials. These IR spectroscopic methods provide a useful toolkit to understand conformations and conformational transitions of SF in various silk materials with spatial resolution from the nano-scale to the micro-scale. In this Review, we first summarize progress in understanding the structure and structure-mechanics relationships of silk materials. We then discuss the state-of-the-art micro- and nano-IR spectroscopic techniques used for silk materials characterization. We also provide a systematic discussion of the strategies to collect high-quality spectra and the methods to analyze these spectra. Finally, we demonstrate the challenges and directions for future exploration of silk-based materials with IR spectroscopies.

Nitrate sorption to biochar following chemical oxidation

Biochar amendments can reduce nitrate (NO₃) leaching in agricultural soil. It has been hypothesized that functional groups on the biochar surface from oxidation can increase NO₃ sorption. This study evaluates the effect of chemical oxidation of biochar on NO₃ sorption characteristics. Eight biochars, made from wood and corn cobs, underwent sodium hypochlorite (NaClO) and hydrogen peroxide (H₂O₂) oxidation and then assessed for NO₃ sorption capacity using batch isotherm methods. The unoxidized and oxidized biochar produced at low temperatures (400 °C) had no significant NO₃ sorption. Oxidized biochars produced at higher temperatures (600 °C and 700 °C) had calculated maximum NO₃ sorption capacities (S_max) ranging from 0.50 to 3.97 mg NO₃-N g^-1. Biochar oxidations with 50 mmol NaClO g^-1 (N50) in combination with an acid wash (AW) had the largest estimated sorption capacities of 3.68, 3.97, and 1.46 mg NO₃-N g^-1 for CT_N50,AW, BW3_N50,AW, and CC3_N50,AW, respectively. Sorption capacity of wood-based biochars was higher than corn cob biochars due to increased oxidation as measured by total acid group content (TAGC). Wood biochar Smax values were correlated with ΔTAGC (R²= 0.86), with a slope of 1.2 μmol NO₃-N μmol TAGC^-1 suggesting that cationic bridging of NO₃ to oxidized sites is the primary mechanism for NO₃ sorption.

A Second Derivative Fourier-Transform Infrared Spectroscopy Method to Discriminate Perilla Oil Authenticity

The aim of this study was to discriminate the authenticity of perilla oils distributed in Korea using their Fourier-Transform infrared spectroscopy (FT-IR) spectra with attenuated total reflectance accessory. By using orthogonal projections for latent structures discriminant analysis (OPLS-DA) technique, the =C-H cis-double bond, -C-H asymmetric and -C-H symmetric stretching are determined to be the best variables for discriminating the perilla oil authenticity. Comparing the integral and the second derivative methods between authentic and adulterated perilla oil samples, the most obvious and significant differences among the three variables is =C-H cis-double bond stretching. The procedure for applying the second derivative range of variables found in authentic perilla oil samples correctly discriminated between the adulterated samples of perilla oils with soybean oils and/or corn oils added at concentrations of ≥ 5 vol%. These results showed that the second derivative FT-IR analysis can be used as a simple and alternative method for discriminating the authenticity of perilla oil.

Spectroscopic Analysis of Human Tracheal Tissue during Decellularization

OBJECTIVE

To use mid-infrared (IR) spectroscopy to assess changes in the cartilaginous framework of human trachea during decellularization.

STUDY DESIGN

Laboratory-based study.

SETTING

Research laboratory.

METHODS

Six cadaveric human tracheas were decellularized using a detergent enzymatic method (DEM). Tissue samples were obtained from each specimen after 0, 1, 10, and 25 DEM cycles for histologic and spectroscopic analysis. Decellularization was confirmed using hematoxylin and eosin (H&E) and 2-(4-amidinophenyl)-1H-indole-6-carboxamidine (DAPI) staining. Changes in cartilaginous framework were examined using Fourier transform infrared imaging spectroscopy (FT-IRIS) and an attenuated total reflectance (ATR) probe in the mid-IR frequencies. Results were statistically analyzed using 1-way analysis of variance (ANOVA) and principal component analysis (PCA).

RESULTS

Six decellularized tracheal scaffolds were successfully created using a DEM protocol. Histologic examination showed near-complete nuclear loss following 25 DEM cycles. As observed with FT-IRIS analysis, the collagen absorbance signal (1336 cm-1) was predominantly in the perichondria and remained stable after 25 DEM cycles ( P = .132), while the absorbance from sugar rings in proteoglycans and nucleic acids in hyaline cartilage (1080 cm-1) showed a significant decrease after 1 DEM cycle ( P = .0007). Examination of the luminal surface of the trachea with an ATR probe showed raw mid-IR spectra consistent with cartilage. PCA showed significant separation of spectra corresponding to treatment cycle along the principal components 1 and 2.

CONCLUSION

Mid-IR spectroscopy is a viable method of monitoring changes in extracellular matrix components during the decellularization of human trachea.

Biochemical alterations of Candida albicans during the phenotypic transition from yeast to hyphae captured by Fourier transform mid-infrared-attenuated reflectance spectroscopy

Candida albicans is an opportunistic human pathogen that can become virulent due to its ability to switch from a benign yeast to virulent hyphae phenotype. The emergence of C. albicans resistant to commonly used antifungal agents has necessitated the development of innovative treatments, which must be accompanied by an understanding of the molecular changes that occur during the phenotypic shift. For this purpose, Fourier transform mid-infrared spectroscopy in attenuated total reflectance mode (FT-mIR-ATR) was applied to monitor the structural and compositional changes in C. albicans during the yeast-to-hyphae transition. FT-mIR-ATR measurements were completed on the whole cell of C. albicans (SC5314) during hyphal formation induced by N-acetylglucosamine at 0, 1, 2, 3, 6 and 24 h. Principal component analysis separated the FT-mIR-ATR spectra into four groups that were aligned with the morphological changes captured by microscopic imaging. Spectral signatures indicating the structural and compositional modifications during the transition were identified mainly in the fatty acid region (3100-2800 cm-1), the protein and peptide region (1800-1500 cm-1), the mixed region (1500-1200 cm-1) and the polysaccharide region (1200-900 cm-1). A spectral fingerprint of the transition via a heat map was generated based on the peak shift in position. Quantitative evaluation of the spectra by curve fitting further revealed the dynamics of the cell's main components during the transition. This work provides valuable structural and functional information on the C. albicans phenotypic transition to hyphae, which has diagnostic implications.

Near infrared spectroscopic assessment of developing engineered tissues: correlations with compositional and mechanical properties

Articular cartilage degeneration causes pain and reduces the mobility of millions of people annually. Regeneration of cartilage is challenging, due in part to its avascular nature, and thus tissue engineering approaches for cartilage repair have been studied extensively. Current techniques to assess the composition and integrity of engineered tissues, including histology, biochemical evaluation, and mechanical testing, are destructive, which limits real-time monitoring of engineered cartilage tissue development in vitro and in vivo. Near infrared spectroscopy (NIRS) has been proposed as a non-destructive technique to characterize cartilage. In the current study, we describe a non-destructive NIRS approach for assessment of engineered cartilage during development, and demonstrate correlation of these data to gold standard mid infrared spectroscopic measurements, and to mechanical properties of constructs. Cartilage constructs were generated using bovine chondrocyte culture on polyglycolic acid (PGA) scaffolds for six weeks. BMP-4 growth factor and ultrasound mechanical stimulation were used to provide a greater dynamic range of tissue properties and outcome variables. NIR spectra were collected daily using an infrared fiber optic probe in diffuse reflectance mode. Constructs were harvested after three and six weeks of culture and evaluated by the correlative modalities of mid infrared (MIR) spectroscopy, histology, and mechanical testing (equilibrium and dynamic stiffness). We found that specific NIR spectral absorbances correlated with MIR measurements of chemical composition, including relative amount of PGA (R = 0.86, p = 0.02), collagen (R = 0.88, p = 0.03), and proteoglycan (R = 0.83, p = 0.01). In addition, NIR-derived water content correlated with MIR-derived proteoglycan content (R = 0.76, p = 0.04). Both equilibrium and dynamic mechanical properties generally improved with cartilage growth from three to six weeks. In addition, significant correlations between NIRS-derived parameters and mechanical properties were found for constructs that were not treated with ultrasound (PGA (R = 0.71, p = 0.01), water (R = 0.74, p = 0.02), collagen (R = 0.69, p = 0.04), and proteoglycan (R = 0.62, p = 0.05)). These results lay the groundwork for extension to arthroscopic engineered cartilage assessment in clinical studies.

Coupling Photoluminescence and Ionic Conduction Properties Using the Different Coordination Sites of Ureasil-Polyether Hybrid Materials

In this article, we demonstrate that each functional group of ureasil organic-inorganic hybrid (OIH) materials can act as a specific coordination site for a given active guest species, hence allowing the possibility of combining different functional properties. To illustrate this concept, the sol-gel process was used to produce diurea cross-linked siloxane-polyethylene oxide (U-PEO) and siloxane-polypropylene oxide (U-PPO) hybrid host frameworks with similar molecular weights (1900 and 2000 g mol^-1 for PEO and PPO, respectively), with Li⁺ and Eu³⁺ as active guest ions providing ionic conduction and photoluminescence (PL) properties, respectively. Comparison of Fourier transform infrared spectra and small-angle X-ray scattering results for single-doped (using Li⁺ or Eu³⁺) and co-doped (using Li⁺ and Eu³⁺) U-PEO and U-PPO hosts showed that in every case, there was specific coordination of Eu³⁺ by the carbonyl group of the urea bridge and of Li⁺ by ether-type oxygen of the PEO and PPO chains. Optical analyses demonstrated that loading with Li⁺ did not affect the luminescence properties of the Eu³⁺-loaded OIH. Although loading with Eu³⁺ had a small effect on ionic transport, co-doping with Li⁺ ions ensured macroscopic ion-conduction of the transparent and luminescent hybrid material. The results suggested that the combination of both properties in a transparent elastomeric material could be useful for the development of multifunctional devices. The results suggested that the combination of both properties in a transparent elastomeric material could be useful for the development of multifunctional polyelectrolytes applied in the field of dual luminescent devices such as photoelectrochromic smart windows.

Infrared Spectroscopic Quantification of Methacrylation of Hyaluronic Acid: A Scaffold for Tissue Engineering Applications

Methacrylated hyaluronic acid (MeHA) has been used extensively in tissue engineering and drug delivery applications. The degree of methacrylation (DM) of HA impacts hydrogel crosslinking, which is of pivotal importance for cell interactions. The methacrylation reaction occurs over several hours, and DM is currently assessed post reaction and after dialysis of the solution, using nuclear magnetic resonance (1H NMR) data. Thus, there is little control over exact DM in a specific reaction. Here, infrared (IR) spectroscopy in attenuated total reflection (ATR) mode was investigated as an alternate modality for assessment of the DM of HA hydrogels, including during the reaction progression. Attenuated total reflection is a low-cost technique that is widely available in research and industry labs that can be used online during the reaction process. Strong correlations were achieved with IR-derived peak heights from dialyzed and lyophilized samples at 1708 cm-1 (from the methacrylic ester carbonyl vibration), and 1H NMR values ( R = 0.92, P = 6.56E-11). Additional IR peaks of importance were identified using principal component analysis and resulted in significant correlations with the 1H NMR DM parameter: 1454 cm-1 ( R = 0.85, P = 2.81E-8), 1300 cm-1 ( R = 0.95, P = 4.50E-14), 950 ( R = 0.85, P = 3.55E-8), 856 cm-1 ( R = 0.94, P = 1.20E-12), and 809 cm-1 ( R = 0.93, P = 3.54E-12). A multiple linear regression model to predict 1H NMR-derived DM using the 1708, 1300, and 1200 cm-1 peak heights as independent variables resulted in prediction with an error of 3.2% using dialyzed and lyophilized samples ( P < 0.001). Additionally, a multilinear regression model to predict the DM in undialyzed liquid MeHA samples obtained during the reaction process using similar peak height positions as independent variables resulted in a prediction error of 0.81% ( P < 0.05). Thus, IR spectroscopy can be utilized as an alternate modality to 1H NMR for quantification of the DM of MeHA while sampling either on-line during the methacrylation reaction as well as in post-lyophilized products. This could greatly simplify workflow for tissue engineering and other applications.

Early changes in the extracellular matrix of the degenerating intervertebral disc, assessed by Fourier transform infrared imaging

OBJECTIVE

Mechanical overloading induces a degenerative cell response in the intervertebral disc. However, early changes in the extracellular matrix (ECM) are challenging to assess with conventional techniques. Fourier Transform Infrared (FTIR) imaging allows visualization and quantification of the ECM. We aim to identify markers for disc degeneration and apply these to investigate early degenerative changes due to overloading and katabolic cell activity.

DESIGN

Three experiments were conducted; Exp 1.: In vivo, lumbar spines of seven goats were operated: one disc was injected with chondroitinase ABC [cABC (mild degeneration)] and compared to the adjacent disc (control) after 24 weeks. Exp 2a: Ex vivo, caprine discs received physiological loading (n = 10) or overloading (n = 10) in a bioreactor. Exp 2b: Cell activity was diminished prior to testing by freeze-thaw cycles, 18 discs were then tested as in Exp 2a. In all experiments, FTIR images (spectral region: 1000-1300 cm^-1) of mid-sagittal slices were analyzed using multivariate curve resolution.

RESULTS

In vivo, FTIR was more sensitive than biochemical and histological analysis in identifying reduced proteoglycan content (P = 0.046) and increased collagen content in degenerated discs (P < 0.01). Notably, FTIR analysis additionally showed disorganization of the ECM, indicated by increased collagen entropy (P = 0.011). Ex vivo, the proteoglycan/collagen ratio decreased due to overloading (P = 0.047) and collagen entropy increased (P = 0.047). Cell activity affected collagen content only (P = 0.044).

CONCLUSION

FTIR imaging allows a more detailed investigation of early disc degeneration than traditional measures. Changes due to mild overloading could be assessed and quantified. Matrix remodeling is the first detectable step towards intervertebral disc degeneration.

Spatial correlation of native and engineered cartilage components at micron resolution

Tissue engineering (TE) approaches are being widely investigated for repair of focal defects in articular cartilage. However, the amount and/or type of extracellular matrix (ECM) produced in engineered constructs does not always correlate with the resultant mechanical properties. This could be related to the specifics of ECM distribution throughout the construct. Here, we present data on the amount and distribution of the primary components of native and engineered cartilage (i.e., collagen, proteoglycan (PG), and water) using Fourier transform infrared imaging spectroscopy (FT-IRIS). These data permit visualization of matrix and water at 25 μm resolution throughout the tissues, and subsequent colocalization of these components using image processing methods. Native and engineered cartilage were cryosectioned at 80 μm for evaluation by FT-IRIS in the mid-infrared (MIR) and near-infrared (NIR) regions. PG distribution correlated strongly with water in native and engineered cartilage, supporting the binding of water to PG in both tissues. In addition, NIR-derived matrix peaks correlated significantly with MIR-derived collagen peaks, confirming the interpretation that these absorbances arise primarily from collagen and not PG. The combined use of MIR and NIR permits assessment of ECM and water spatial distribution at the micron level, which may aid in improved development of TE techniques.

Composition, structure and tensile biomechanical properties of equine articular cartilage during growth and maturation

Articular cartilage undergoes structural and biochemical changes during maturation, but the knowledge on how these changes relate to articular cartilage function at different stages of maturation is lacking. Equine articular cartilage samples of four different maturation levels (newborn, 5-month-old, 11-month-old and adult) were collected (N = 25). Biomechanical tensile testing, Fourier transform infrared microspectroscopy (FTIR-MS) and polarized light microscopy were used to study the tensile, biochemical and structural properties of articular cartilage, respectively. The tensile modulus was highest and the breaking energy lowest in the newborn group. The collagen and the proteoglycan contents increased with age. The collagen orientation developed with age into an arcade-like orientation. The collagen content, proteoglycan content, and collagen orientation were important predictors of the tensile modulus (p < 0.05 in multivariable regression) and correlated significantly also with the breaking energy (p < 0.05 in multivariable regression). Partial least squares regression analysis of FTIR-MS data provided accurate predictions for the tensile modulus (r = 0.79) and the breaking energy (r = 0.65). To conclude, the composition and structure of equine articular cartilage undergoes changes with depth that alter functional properties during maturation, with the typical properties of mature tissue reached at the age of 5-11 months.

Differential Diagnosis of the Etiologies of Bacterial and Viral Infections Using Infrared Microscopy of Peripheral Human Blood Samples and Multivariate Analysis

Human viral and bacterial infections are responsible for a variety of diseases that are still the main causes of death and economic burden for society across the globe. Despite the different responses of the immune system to these infections, some of them have similar symptoms, such as fever, sneezing, inflammation, vomiting, diarrhea, and fatigue. Thus, physicians usually encounter difficulties in distinguishing between viral and bacterial infections on the basis of these symptoms. Rapid identification of the etiology of infection is highly important for effective treatment and can save lives in some cases. The current methods used for the identification of the nature of the infection are mainly based on growing the infective agent in culture, which is a time-consuming (over 24 h) and usually expensive process. The main objective of this study was to evaluate the potential of the mid-infrared spectroscopic method for rapid and reliable identification of bacterial and viral infections based on simple peripheral blood samples. For this purpose, white blood cells (WBCs) and plasma were isolated from the peripheral blood samples of patients with confirmed viral or bacterial infections. The obtained spectra were analyzed by multivariate analysis: principle component analysis (PCA) followed by linear discriminant analysis (LDA), to identify the infectious agent type as bacterial or viral in a time span of about 1 h after the collection of the blood sample. Our preliminary results showed that it is possible to determine the infectious agent with high success rates of 82% for sensitivity and 80% for specificity, based on the WBC data.