Attenuated total reflectance fourier transform infrared spectroscopy: an analytical technique to understand therapeutic responses at the molecular level

Rapid monitoring of the response to treatment in cancer patients is essential to predict the outcome of the therapeutic regimen early in the course of the treatment. The conventional methods are laborious, time-consuming, subjective and lack the ability to study different biomolecules and their interactions, simultaneously. Since; mechanisms of cancer and its response to therapy is dependent on molecular interactions and not on single biomolecules, an assay capable of studying molecular interactions as a whole, is preferred. Fourier Transform Infrared (FTIR) spectroscopy has become a popular technique in the field of cancer therapy with an ability to elucidate molecular interactions. The aim of this study, was to explore the utility of the FTIR technique along with multivariate analysis to understand whether the method has the resolution to identify the differences in the mechanism of therapeutic response. Towards achieving the aim, we utilized the mouse xenograft model of retinoblastoma and nanoparticle mediated targeted therapy. The results indicate that the mechanism underlying the response differed between the treated and untreated group which can be elucidated by unique spectral signatures generated by each group. The study establishes the efficiency of non-invasive, label-free and rapid FTIR method in assessing the interactions of nanoparticles with cellular macromolecules towards monitoring the response to cancer therapeutics.

Effects of increasing neuromuscular electrical stimulation current intensity on cortical sensorimotor network activation: a time domain fNIRS study

Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements activate regions of the cortical sensorimotor network, including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), and secondary somatosensory area (S2), as well as regions of the prefrontal cortex (PFC) known to be involved in pain processing. The aim of this study, on nine healthy subjects, was to compare the cortical network activation profile and pain ratings during NMES of the right forearm wrist extensor muscles at increasing current intensities up to and slightly over the individual maximal tolerated intensity (MTI), and with reference to voluntary (VOL) wrist extension movements. By exploiting the capability of the multi-channel time domain functional near-infrared spectroscopy technique to relate depth information to the photon time-of-flight, the cortical and superficial oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations were estimated. The O2Hb and HHb maps obtained using the General Linear Model (NIRS-SPM) analysis method, showed that the VOL and NMES-evoked movements significantly increased activation (i.e., increase in O2Hb and corresponding decrease in HHb) in the cortical layer of the contralateral sensorimotor network (SMC, PMC/SMA, and S2). However, the level and area of contralateral sensorimotor network (including PFC) activation was significantly greater for NMES than VOL. Furthermore, there was greater bilateral sensorimotor network activation with the high NMES current intensities which corresponded with increased pain ratings. In conclusion, our findings suggest that greater bilateral sensorimotor network activation profile with high NMES current intensities could be in part attributable to increased attentional/pain processing and to increased bilateral sensorimotor integration in these cortical regions.

Cerebral oxygenation in mechanically ventilated early cardiac arrest survivors: The impact of hypercapnia

BACKGROUND : Optimal cerebral oxygenation is considered fundamental to cerebral protection in cardiac arrest (CA) patients. Hypercapnia increases cerebral blood flow and may also improve cerebral oxygenation. It is uncertain, however, whether this effect occurs in mechanically ventilated early survivors of CA. METHODS: We enrolled mechanically ventilated resuscitated patients within 36 h of their cardiac arrest. We performed a prospective double cross-over physiological study comparing the impact of normocapnia (PaCO2 35-45 mmHg) vs. mild hypercapnia (PaCO2 45-55 mmHg) on regional cerebral tissue oxygen saturation (SctO2) assessed by near infrared spectroscopy (NIRS).RESULTS: We studied seven adult CA patients with a median time to return of spontaneous circulation of 28 min at a median of 26 h and 30 min after CA. During normocapnia (median EtCO2 of 32 mmHg [30-41 mmHg] and PaCO2 of 37 mmHg [32-45 mmHg]) the median NIRS-derived left frontal SctO2 was 61% [52-65%] and the right frontal SctO2 was 61% [54-68%]. However, during mild hypercapnia (median EtCO2 of 49 mmHg [40-57 mmHg] and PaCO2 of 52 mmHg [43-55 mmHg) the median left frontal SctO2 increased to 69% [59-78%] and the right frontal SctO2 increased to 73% [61-76%])(p = 0.001, for all comparisons). CONCLUSION: During the early post-resuscitation period, in mechanically ventilated CA patients, mild hypercapnia increases cerebral oxygenation as assessed by NIRS. Further investigations of the effect of prolonged mild hypercapnia on cerebral oxygenation and patient outcomes appear justified.

Bond length dependence on quantum states as shown by spectroscopy

Undergraduate students often have the misconception that molecules have fixed, unchanging bond lengths. This article discusses how linear-molecule rotational band spacings in infrared spectroscopy can be used as a qualitative, visual demonstration of the elongation of average bond lengths on vibrational excitation. The method does not depend on a detailed mathematical analysis of the spectra. In UV–vis spectroscopy, the rotational band spacings give rise to distinctive linear-molecule rotational contours, which easily show whether the average bond length has increased or decreased. The method is based on a spreadsheet simulation of the vibration–rotation or rovibronic (electronic–vibration–rotation) spectrum and is applied to hydrogen chloride IR, iodine UV–vis, and nitrogen UV–vis spectra in this article.

Rapid discrimination and determination of polyunsaturated fatty acid composition in marine oils by FTIR Spectroscopy and Multivariate Data Analysis

A rapid analytical approach for discrimination and quantitative determination of polyunsaturated fatty acid (PUFA) contents, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in a range of oils extracted from marine resources has been developed by using attenuated total reflection Fourier transform infrared spectroscopy and multivariate data analysis. The spectral data were collected without any sample preparation; thus, no chemical preparation was involved, but data were rather processed directly using the developed spectral analysis platform, making it fast, very cost effective, and suitable for routine use in various biotechnological and food research and related industries. Unsupervised pattern recognition techniques, including principal component analysis and unsupervised hierarchical cluster analysis, discriminated the marine oils into groups by correlating similarities and differences in their fatty acid (FA) compositions that corresponded well to the FA profiles obtained from traditional lipid analysis based on gas chromatography (GC). Furthermore, quantitative determination of unsaturated fatty acids, PUFAs, EPA and DHA, by partial least square regression analysis through which calibration models were optimized specifically for each targeted FA, was performed in both known marine oils and totally independent unknown n - 3 oil samples obtained from an actual commercial product in order to provide prospective testing of the developed models towards actual applications. The resultant predicted FAs were achieved at a good accuracy compared to their reference GC values as evidenced through (1) low root mean square error of prediction, (2) good coefficient of determination close to 1 (i.e., R 2≥ 0.96), and (3) the residual predictive deviation values that indicated the predictive power at good and higher levels for all the target FAs. © 2014 Springer Science+Business Media New York.

Hydrothermal synthesis of dioctahedral smectites: The Al-Fe3+chemical series. Part II: crystal-chemistry

The crystal-chemistry of a series of synthetic Al-Fe3+ smectites was studied in detail using near and mid infrared spectroscopy. Chemical and NIR data indicated a quite complete range of octahedral Al for Fe3+ substitution, and therefore, the solid-solution between beidellite and nontronite end-members was continuous and complete. The wavenumbers of several infrared absorption bands were correlated with the chemistry of the synthetic smectites, providing a useful tool to constrain their structural formulae and also for assisting in assignments of similar bands in natural smectites. The Al and Fe3+ cations were shown to be randomly distributed in the octahedral sheet of synthesized smectites. Despite the high availability of iron during synthesis, generally only a small amount of tetrahedral Fe3+ was observed.