Ms. Yahira M. Rivera-Lopez Profile

Yahira M. Rivera-Lopez

at Delaware State Univ

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Proceedings Article | 13 March 2024 Presentation

LIBS and Raman scattering studies of alginate solutions and gels

Hacene Boukari, Yahira Lopez, Shehu-Alimi Elelu, Cleon Barnett

Proceedings Volume PC12859, PC1285908 (2024) https://doi.org/10.1117/12.3003370

KEYWORDS: Laser induced breakdown spectroscopy, Raman scattering, Raman spectroscopy, Chemical analysis, Vibration, Toxicity, Strontium, Principal component analysis, Plasma, Oxygen

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We applied laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy to assess the structural content of alginate solutions and gels prepared at various concentrations (1.0 to 40 mg/mL). Alginate is a natural biopolymer typically extracted from brown seaweed and has been applied in diverse biomedical applications. LIBS measurements in Alginate solutions show spectral lines that can be attributed to calcium (422.6, 393.3, and 396.8 nm), magnesium (279.5 nm), strontium (460.7 nm), and C-N bond (~388.3 nm). Crosslinking the alginate solutions into hydrogels tends to reduce emission intensity, and many LIBS lines are not discerned. Measured Raman spectra show several peaks in addition to those of water and dissolved oxygen and nitrogen. The higher the alginate concentration, the higher the intensity of the alginate peaks. We combined the intensity correlation analysis (ICA), principal component analysis, and first-order derivative method to assess changes of the Raman peaks. Altogether, the results demonstrate how both techniques can provide complementary insight for chemical analysis of alginate solutions and gels.

Proceedings Article | 4 March 2022 Presentation + Paper

Intensity correlation analysis of Raman spectra of concentrated Ficoll solutions

Y. Lopez, M. Salih, F. Boukari, C. Barnett, H. Boukari

Proceedings Volume 11944, 119440B (2022) https://doi.org/10.1117/12.2609947

KEYWORDS: Raman spectroscopy, Molecules, Chemical analysis, Statistical analysis, Spectroscopy, Molecular interactions

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The intracellular environment is crowded with diverse biomacrolecules (~80-400 mg/ml), likely affecting various biological processes such as protein folding, binding of small molecules, enzymatic activity, and pathological protein aggregation. As a model we have been using solutions of Ficoll, a highly branched polysaccharide, to mimic the environment. Besides its biomedical applications (e.g. blood separation), it has been used as a macromolecular crowder in studies of protein folding and stability, cell volume signaling, tissue engineering, and nanotransport. In this study, our goal is to identify and assess Raman spectral signatures associated with Ficoll molecules and Ficoll-Ficoll interactions for future investigations of crowding effects. In addition to the Raman peaks of water (~1640 cm^-1 and ~3200 cm^-1) and dissolved O₂ (~1556 cm-1) and N2 (~2331 cm-1) we identified a distinct Raman peak (~2900 cm^-1) in the 1500-3500 cm^-1 wavenumber range, which is associated with Ficoll and CH and CH₂ stretching modes. As the Ficoll concentration increases, the intensity of the Ficoll Raman peaks increases while the intensity of the water Raman peaks decreases, the latter likely due to reduction of water content. Further, we have applied the intensity correlation analysis (ICA) method to assess systematic changes of Raman spectra with Ficoll concentration (up to 1000 mg/ml). ICA indicates an overall linear trend over the full wavenumber range, but also shows closed loops that can be attributed to slight changes of the profiles of certain peaks. The results demonstrate ICA as a potential insightful tool for identifying Ficoll in chemical analysis of crowded biological samples.

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