The Changes of Fourier Transform Infrared Spectrum in Rat Brain*

A methodological approach to age estimation of the intra-puparial period of the forensically relevant blow fly Calliphora vicina via Fourier transform infrared spectroscopy

Estimating the age of immature blow flies is of great importance for forensic entomology. However, no gold-standard technique for an accurate determination of the intra-puparial age has yet been established. Fourier transform infrared (FTIR) spectroscopy is a method to (bio-)chemically characterise material based on the absorbance of electromagnetic energy by functional groups of molecules. In recent years, it also has become a powerful tool in forensic and life sciences, as it is a fast and cost-effective way to characterise all kinds of material and biological traces. This study is the first to collect developmental reference data on the changes in absorption spectra during the intra-puparial period of the forensically important blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Calliphora vicina was reared at constant 20°C and 25°C and specimens were killed every other day throughout their intra-puparial development. In order to investigate which part yields the highest detectable differences in absorption spectra throughout the intra-puparial development, each specimen was divided into two different subsamples: the pupal body and the former cuticle of the third instar, that is, the puparium. Absorption spectra were collected with a FTIR spectrometer coupled to an attenuated total reflection (ATR) unit. Classification accuracies of different wavenumber regions with two machine learning models, i.e., random forests (RF) and support vector machines (SVMs), were tested. The best age predictions for both temperature settings and machine learning models were obtained by using the full spectral range from 3700 to 600 cm-1. While SVMs resulted in better accuracies for C. vicina reared at 20°C, RFs performed almost as good as SVMs for data obtained from 25°C. In terms of sample type, the pupal body gave smoother spectra and usually better classification accuracies than the puparia. This study shows that FTIR spectroscopy is a promising technique in forensic entomology to support the estimation of the minimum post-mortem interval (PMImin), by estimating the age of a given insect specimen.

A preliminary study on the development of a novel biomatrix by decellularization of bovine spinal meninges for tissue engineering applications

Here, we aim at developing a novel biomatrix from decellularized bovine spinal meninges for tissue engineering and regenerative medicine applications. Within this concept, the bovine spinal meninges were decellularized using 1% Triton X-100 for 48 h, and residual nuclear content was determined with double-strand DNA content analysis and agarose gel electrophoresis. The major matrix components such as sulfated GAGs and collagen before and after the decellularization process were analyzed with DMMB, hydroxyproline assay and SDS-PAGE. Subsequently, the native bovine spinal meninges (nBSM) and decellularized BSM (dBSM) were physiochemically characterized via ATR-FTIR spectroscopy, TGA, DMA and tensile strength test. The dsDNA content in the nBSM was 153.39 ± 53.93 ng/mg dry weight, versus in the dBSM was 39.47 ± 4.93 ng/mg (n = 3) dry weight and DNA fragments of more than 200 bp in length were not detected in the dBSM by agarose gel electrophoresis. The sulfated GAGs contents for nBSM and dBSM were observed to be 10.87 ± 1.2 and 11.42 ± 2.01 μg/mg dry weight, respectively. The maximum strength of dBSM in dry and wet conditions was found to be 19.67 ± 0.21 MPa and 13.97 ± 0.17 MPa, while nBSM (dry) was found to be 26.26 ± 0.28 MPa. MTT, SEM, and histology results exhibited that the cells attached to the surface of dBSM, and proliferated on the dBSM. In conclusion, the in vitro preliminary study has demonstrated that the dBSM might be a proper and new bioscaffold for tissue engineering and regenerative medicine applications.

Rapid Label-Free Analysis of Brain Tumor Biopsies by Near Infrared Raman and Fluorescence Spectroscopy-A Study of 209 Patients

In brain surgery, novel technologies are continuously developed to achieve better tumor delineation and maximize the extent of resection. Raman spectroscopy is an optical method that enables to retrieve a molecular signature of tissue biochemical composition in order to identify tumor and normal tissue. Here, the translation of Raman spectroscopy to the surgical practice for discerning a variety of different tumor entities from non-neoplastic brain parenchyma was investigated. Fresh unprocessed biopsies obtained from brain tumor surgery were analyzed over 1.5 years including all patients that gave consent. Measurements were performed with a Raman microscope by medical personnel as routine activity. The Raman and fluorescence signals of the acquired spectra were analyzed by principal component analysis, followed by supervised classification to discriminate non-tumor tissue vs. tumor and distinguish tumor entities. Histopathology of the measured biopsies was performed as reference. Classification led to the correct recognition of all non-neoplastic biopsies (7/7) and of 97% of the investigated tumor biopsies (195/202). For instance, GBM was recognized as tumor with a correct rate of 94% if primary, and of 100% if recurrent. Astrocytoma and oligodendroglioma were recognized as tumor with correct rates of 86 and 90%, respectively. All brain metastases, meningioma and schwannoma were correctly recognized as tumor and distinguished from non-neoplastic brain tissue. Furthermore, metastases were discerned from glioma with correct rate of 90%. Oligodendroglioma and astrocytoma IDH1-mutant, which differ in the presence of 1p/19q codeletion, were discerned with a correct rate of 81%. These results demonstrate the feasibility of rapid brain tumors recognition and extraction of diagnostic information by Raman spectroscopy, using a protocol that can be easily included in the routine surgical workflow.

Evaluating the effects of causes of death on postmortem interval estimation by ATR-FTIR spectroscopy

Estimating postmortem interval (PMI) is one of the most challenging tasks in forensic practice due to the effects of many factors. Here, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy combined with chemometrics was utilized to evaluate the effects of causes of death when estimating PMI and to establish a partial least square (PLS) regression model, which can precisely predict PMI under different causes of death. First, the sensitivities to causes of death (brainstem injury, mechanical asphyxia, and hemorrhage shock) of seven kinds of organs were evaluated based on their degrees of cohesion and separation. Then, the liver was selected as the most sensitive organ to establish a PMI estimation model to compare the predicted deviations from different causes of death. It turns out that the cause of death has no significant effect on estimating PMI. Next, a PLS regression model was built with kidney tissues, which have the lowest sensitivity, and this model showed a satisfactory predictive ability and wide applicability. This study demonstrates the feasibility of using ATR-FTIR spectroscopy in conjunction with chemometrics as a powerful alternative for detecting changes in biochemistry and estimating PMI. A new perspective was also provided for evaluating the effect of causes of death when predicting PMI.

Application of Fourier transform infrared spectroscopy with chemometrics on postmortem interval estimation based on pericardial fluids

Postmortem interval (PMI) evaluation remains a challenge in the forensic community due to the lack of efficient methods. Studies have focused on chemical analysis of biofluids for PMI estimation; however, no reports using spectroscopic methods in pericardial fluid (PF) are available. In this study, Fourier transform infrared (FTIR) spectroscopy with attenuated total reflectance (ATR) accessory was applied to collect comprehensive biochemical information from rabbit PF at different PMIs. The PMI-dependent spectral signature was determined by two-dimensional (2D) correlation analysis. The partial least square (PLS) and nu-support vector machine (nu-SVM) models were then established based on the acquired spectral dataset. Spectral variables associated with amide I, amide II, COO-, C-H bending, and C-O or C-OH vibrations arising from proteins, polypeptides, amino acids and carbohydrates, respectively, were susceptible to PMI in 2D correlation analysis. Moreover, the nu-SVM model appeared to achieve a more satisfactory prediction than the PLS model in calibration; the reliability of both models was determined in an external validation set. The study shows the possibility of application of ATR-FTIR methods in postmortem interval estimation using PF samples.

UV-Vis and ATR-FTIR spectroscopic investigations of postmortem interval based on the changes in rabbit plasma

Estimating PMI is of great importance in forensic investigations. Although many methods are used to estimate the PMI, a few investigations focus on the postmortem redistribution. In this study, ultraviolet-visible (UV-Vis) measurement combined with visual inspection indicated a regular diffusion of hemoglobin into plasma after death showing the redistribution of postmortem components in blood. Thereafter, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to confirm the variations caused by this phenomenon. First, full-spectrum partial least-squares (PLS) and genetic algorithm combined with PLS (GA-PLS) models were constructed to predict the PMI. The performance of GA-PLS model was better than that of full-spectrum PLS model based on its root mean square error (RMSE) of cross-validation of 3.46 h (R2 = 0.95) and the RMSE of prediction of 3.46 h (R2 = 0.94). The investigation on the similarity of spectra between blood plasma and formed elements also supported the role of redistribution of components in spectral changes in postmortem plasma. These results demonstrated that ATR-FTIR spectroscopy coupled with the advanced mathematical methods could serve as a convenient and reliable tool to study the redistribution of postmortem components and estimate the PMI.

Characterization of postmortem biochemical changes in rabbit plasma using ATR-FTIR combined with chemometrics: A preliminary study

Postmortem interval (PMI) determination is one of the most challenging tasks in forensic medicine due to a lack of accurate and reliable methods. It is especially difficult for late PMI determination. Although many attempts with various types of body fluids based on chemical methods have been made to solve this problem, few investigations are focused on blood samples. In this study, we employed an attenuated total reflection (ATR)-Fourier transform infrared (FTIR) technique coupled with principle component analysis (PCA) to monitor biochemical changes in rabbit plasma with increasing PMI. Partial least square (PLS) model was used based on the spectral data for PMI prediction in an independent sample set. Our results revealed that postmortem chemical changes in compositions of the plasma were time-dependent, and various components including proteins, lipids and nucleic acids contributed to the discrimination of the samples at different time points. A satisfactory prediction within 48h postmortem was performed by the combined PLS model with a good fitting between actual and predicted PMI of 0.984 and with an error of ±1.92h. In consideration of the simplicity and portability of ATR-FTIR, our preliminary study provides an experimental and theoretical basis for application of this technique in forensic practice.

Investigation of gene expressions in differentiated cell derived bone marrow stem cells during bone morphogenetic protein-4 treatments with Fourier transform infrared spectroscopy

A model was set up to predict the differentiation patterns based on the data extracted from FTIR spectroscopy. For this reason, bone marrow stem cells (BMSCs) were differentiated to primordial germ cells (PGCs). Changes in cellular macromolecules in the time of 0, 24, 48, 72, and 96h of differentiation, as different steps of the differentiation procedure were investigated by using FTIR spectroscopy. Also, the expression of pluripotency (Oct-4, Nanog and c-Myc) and specific genes (Mvh, Stella and Fragilis) were investigated by real-time PCR. However, the expression of genes in five steps of differentiation was predicted by FTIR spectroscopy. FTIR spectra showed changes in the template of band intensities at different differentiation steps. There are increasing changes in the stepwise differentiation procedure for the ratio area of CH2, which is symmetric to CH2 asymmetric stretching. An ensemble of expert methods, including regression tree (RT), boosting algorithm (BA), and generalized regression neural network (GRNN), was the best method to predict the gene expression by FTIR spectroscopy. In conclusion, the model was able to distinguish the pattern of different steps from cell differentiation by using some useful features extracted from FTIR spectra.

Fourier-transform infrared spectroscopy as a novel approach to providing effect-based endpoints in duckweed toxicity testing

Traditional duckweed toxicity tests only measure plant growth inhibition as an endpoint, with limited effects-based data. The present study aimed to investigate whether Fourier-transform infrared (FTIR) spectroscopy could enhance the duckweed (Lemna minor L.) toxicity test. Four chemicals (Cu, Cd, atrazine, and acetochlor) and 4 metal-containing industrial wastewater samples were tested. After exposure of duckweed to the chemicals, standard toxicity endpoints (frond number and chlorophyll content) were determined; the fronds were also interrogated using FTIR spectroscopy under optimized test conditions. Biochemical alterations associated with each treatment were assessed and further analyzed by multivariate analysis. The results showed that comparable x% of effective concentration (ECx) values could be achieved based on FTIR spectroscopy in comparison with those based on traditional toxicity endpoints. Biochemical alterations associated with different doses of toxicant were mainly attributed to lipid, protein, nucleic acid, and carbohydrate structural changes, which helped to explain toxic mechanisms. With the help of multivariate analysis, separation of clusters related to different exposure doses could be achieved. The present study is the first to show successful application of FTIR spectroscopy in standard duckweed toxicity tests with biochemical alterations as new endpoints. Environ Toxicol Chem 2017;36:346-353. © 2016 SETAC.

Research progress in the estimation of the postmortem interval by Chinese forensic scholars

The determination of time since death or the postmortem interval (PMI) is one of the most important and frequently asked questions in forensic medicine. Medicolegal scholars and forensic pathologists around the world have studied the estimation of PMI extensively in the past, and many novel methods and advanced technologies have now been applied in the field. For several centuries, Chinese forensic examiners have also worked on the estimation of the PMI, and there are a large number of excellent studies published in Chinese rather than in English, and these are not easily accessible or known internationally. Therefore we have conducted a review of relevant studies published by Chinese forensic scholars in the last few decades. The scope of this review is to provide a concise summary of the current progress in the estimation of PMI by Chinese forensic researchers using molecular biology, spectroscopic technology, entomological methods, energy changes, thanatochemistry and other methods.

Animal experimentation in forensic sciences: How far have we come?

In the third millennium where ethical, ethological and cultural evolution seem to be leading more and more towards an inter-species society, the issue of animal experimentation is a moral dilemma. Speaking from a self-interested human perspective, avoiding all animal testing where human disease and therapy are concerned may be very difficult or even impossible; such testing may not be so easily justifiable when suffering-or killing-of non human animals is inflicted for forensic research. In order to verify how forensic scientists are evolving in this ethical issue, we undertook a systematic review of the current literature. We investigated the frequency of animal experimentation in forensic studies in the past 15 years and trends in publication in the main forensic science journals. Types of species, lesions inflicted, manner of sedation or anesthesia and euthanasia were examined in a total of 404 articles reviewed, among which 279 (69.1%) concerned studies involving animals sacrificed exclusively for the sake of the experiment. Killing still frequently includes painful methods such as blunt trauma, electrocution, mechanical asphyxia, hypothermia, and even exsanguination; of all these animals, apparently only 60.8% were anesthetized. The most recent call for a severe reduction if not a total halt to the use of animals in forensic sciences was made by Bernard Knight in 1992. In fact the principle of reduction and replacement, frequently respected in clinical research, must be considered the basis for forensic science research needing animals.

Infrared (IR) spectral markers of bronchial epithelia in victims of fatal burns

Changes in the infrared spectra of bronchial epithelia in victims of fatal burns were investigated. The mechanism of spectral changes on the basis of cellular morphological changes was considered. The ability of spectral parameters to diagnose fatal burns was assessed. Ten cases of fatal burns and 20 control cases were selected. Their lung tissues were removed, and sections were cut and mounted on glass and barium fluoride slides. Spectra of polarized bronchial epithelia were obtained by microscopy based on their morphological changes. In the spectra, 16 major absorbance bands were evaluated to determine their ability to act as positive markers for exposure to fire. Compared with the control group, the bronchial epithelia of the fatal burn victims showed three spectral results. (1) The absorbance of 16 major bands from the spectra of polarized bronchial epithelia in fatal burn victims significantly increased. (2) For the same cell number, the absorbance at 2850, 2920, 2959, and 3084 cm(-1) decreased. (3) The degree of increased or decreased absorbance of bands is related to the degree of polarization. These spectral results suggest that there is a vital reaction induced by the inhalation of hot fumes that includes an increase in the number of bronchial epithelia and a polarization effect. Overall, Fourier transform infrared (FT-IR) microspectroscopy was shown to be a convenient and reliable method to provide objective spectral markers to assist the diagnosis of fatal burns by simultaneously monitoring several specific parameters, although these observations have yet to be applied at forensic scenes.

Estimation of PMI depends on the changes in ATP and its degradation products

Estimating the time since death, or postmortem interval (PMI), has been one of the biggest difficulties in modern forensic investigation. This study tests if the concentrations of breakdown products of adenosine triphosphate (ATP) correlate with PMI in multiple organs from rat. Brains, spleens, and kidneys of rats were harvested at different time points in carcasses maintained at 4°C or 20°C. High Performance Liquid Chromatography (HPLC) was used to quantify concentrations of metabolites related to ATP degradation. A K value (Kv=100×(Hx+HxR)/(ATP+ADP+AMP+IMP+HxR+Hx)) was calculated and correlated with PMI for each organ and temperature. The results indicate that the K value is a robust index for the estimation of PMI based on highly significant linear correlations between PMI and concentrations of ATP breakdown products. Compared with other current research methods, the changing tendency of ATP and its degradation products may be potentially a better way for the estimation of PMI in medico-legal practice.