Biomedical subjects

Roumiana Tsenkova

Publications and source records attributed to Roumiana Tsenkova.

5 recordsLinked to original sources

PubMed2006

Comparison of the vibration mode of metals in HNO3 by a partial least-squares regression analysis of near-infrared spectra.

The near-infrared (NIR) spectra of such metals as Cu(II), Mn(II), Zn(II) and Fe(III) in HNO(3) in the 700-1,860 nm region were subjected to a partial least-squares regression analysis and leave-out cross-validation to develop chemometric models. The models yielded a coefficient of determination in cross validation of 0.9744 [Cu(II)], 0.9631 [Mn(II)], 0.9154 [Zn(II)] and 0.741 [Fe(III)]. The regression coefficients for Cu(II), Mn(II) and Zn(II), but not for Fe(III), showed strong negative peaks at around 1,050-1,200 nm, a zone where spectral bands have been reported to decrease with increasing pH value. A positive peak at around 710-750 nm, which may have been due to water absorption, was observed in regression coefficients of Cu(II), Mn(II) and Zn(II) but not in Fe(III), while a negative peak was observed in that for Fe(III) at around 710-750 nm. These results indicate that the divalent cations [Cu(II), Mn(II) and Zn(II)] showed different absorption in the NIR region from the trivalent cation [Fe(III)], suggesting that the vibration mode of water, which mirrors the interaction between cations and water, may be influenced by valency.

Cations↗

PubMed2006

Ex vivo tissue discrimination by visible and near-infrared spectra with chemometrics.

The risk of infections from zoonotic pathogens of tissues and/or tissue-derived products has been increasing. One preventive approach in reducing infection risk is tissue decontamination, where selection and screening of highly infectious tissues are strictly followed. Therefore, the development of reliable analytical methods for rapid tissue discrimination is essentially important. In the present study, a procedure has been developed for intact tissue discrimination on the basis of multivariate analysis of visible and near-infrared (Vis-NIR) spectra of certain tissues such as brain, liver, kidney and testis of mice without any pretreatment. Transmittance spectra in the 600- to 1000-nm regions were subjected to a principal component analysis (PCA), and leave-out cross-validation was employed to develop multivariate models for tissue discrimination. The plot of PCA scores against Vis-NIR spectra of brains, kidneys, livers and testes from 11 mice portrayed reliable tissue discrimination. This result suggests that Vis-NIR spectroscopy combined with chemometrics analysis may provide a potentially useful approach for rapid non-destructive discrimination of tissues.

Animals↗

PubMed2006

New method for spectral data classification: two-way moving window principal component analysis.

Two-way moving window principal component analysis (TMWPCA), which considers all possible variable regions by using variable and sample moving windows, is proposed as a new spectral data classification method. In TMWPCA, the similarity between model function and the index obtained by variable and sample moving windows is defined as "fitness". For each variable region selected by a variable moving window, the fitness is obtained through the use of a model function. By maximizing the fitness, an optimal variable region can be searched. A remarkable advantage of TMWPCA is that it offers an optimal variable region for the classification. To demonstrate the potential of TMWPCA, it has been applied to the classification of visible-near-infrared (Vis-NIR) spectra of mastitic and healthy udder quarters of cows measured in a nondestructive manner. The misclassification rate of TMWPCA has been compared with those of other chemometric methods, such as principal component analysis (PCA), soft independent modeling of class analogies (SIMCA), and principal discriminant variate (PDV). TMWPCA has yielded the lowest misclassification rate. The result indicates that TMWPCA is a powerful tool for the classification of spectral data.

Journal Article↗

PubMed2005

A novel diagnostic method for human immunodeficiency virus type-1 in plasma by near-infrared spectroscopy.

Presently, the diagnosis of virus infections is based mainly on serological assays. Although polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) have been increasingly used for the diagnosis of such viral infections, the risk of transfusion-transmitted blood-borne viruses remains. Furthermore, PCR and ELISA are expensive and time-consuming, and sometimes cause falsepositive or false-negative results. Therefore, a rapid, accurate and cost-effective diagnostic procedure is needed. We subjected plasma from individuals infected with human immunodeficiency virus type-1 (HIV-1), the causative agent of acquired immune deficiency syndrome (AIDS), as well as plasma from uninfected individuals as a control to near-infrared (NIR) spectroscopy, which may provide a rapid diagnostic method for HIV-1 infection without using any reagent. NIR spectra in the 600-1,000 nm region for plasma from pre-serologically HIV-1-infected individuals and healthy donors were subjected to partial least squares (PLS) regression analysis and leave-out cross-validation to develop a multivariate model to estimate the concentration of HIV-1. Simultaneously, the same plasma samples were examined for HIV-1 p24 by ELISA. The results obtained by the NIR spectroscopy model for HIV-1 yielded a good correlation with those obtained by the reference method (HIV-1 p24 ELISA). These results suggest that NIR spectroscopy using plasma could provide a rapid, accurate, cost-effective tool for large-scale diagnosis of HIV-1 infection.

Antigens, Viral↗

PubMed2003

Temperature-dependent near-infrared spectra of bovine serum albumin in aqueous solutions: spectral analysis by principal component analysis and evolving factor analysis.

Fourier transform near-infrared (FT-NIR) spectra have been measured for bovine serum albumin (BSA) in an aqueous solution (pH 6.8) with a concentration of 5.0 wt% over a temperature range of 45-85 degrees C. Not only conventional spectral analysis methods, such as second-derivative spectra and difference spectra, but also chemometrics, such as principal component analysis (PCA) and evolving factor analysis (EFA), have been employed to analyze the temperature-dependent NIR spectra in the 7500-5500 and 4900-4200 cm-1 regions of the BSA aqueous solution. Intensity changes of bands in the 7200-6600 cm-1 and 4650-4500 cm-1 regions in the difference spectra indicate variations of the hydration and secondary structure of BSA in the aqueous solution, respectively. The plot of a band intensity at 7080 cm-1 in the different spectra shows a clear turning point at 63 degrees C, revealing that a significant change in the hydration occurs at about 63 degrees C. The forward and backward eigenvalues (EVs) from EFA suggest that marked changes in the hydration and secondary structure of BSA take place in the temperature ranges of 61-65 degrees C and 59-63 degrees C, respectively. In addition, the temperature of 71 degrees C marked in the EFA plots may correspond to the onset temperature of increase in the intermolecular beta-sheet structure.

Animals↗