Subcategory: STEM Research
Hacene Boukari - Delaware State University
Co-Author(s): Yury Markushin and Qi Lu, Physics and Engineering Department, Delaware State University Noureddine Melikechi, Optical Science Center for Applied Research, Delaware State University
As one of three subprojects supported by our CREOSA center, we have assembled a collaborative team of researchers to devise and implement an integrative, optical-based approach for precise detection, accurate identification, and in-situ characterization of specific biomacromolecules embedded in various biologically-relevant matrices. Our overarching goal is the development and/or application of high-resolution optical and imaging methods such as laser-induced breakdown spectroscopy, photothermal lensing spectroscopy, fluorescence correlation spectroscopy, and fast sheet illumination microscopy to investigate in-situ biomacromolecular interactions in the presence of a host matrix. We will design novel immunoassays to label the biomacromolecules with suitable fluorescent or metallic probes, allowing efficient and accurate detection of several biomacromolecules simultaneously. As an example, we have focused on understanding the dynamics of various nanoparticles (e.g. fluorescent Alexa488; amino-acids) embedded in a host Ficoll solutions prepared at different concentrations (up to 1200 mg/ml). Ficoll is a water-soluble, branched polysaccharide. We applied several techniques (fluorescence correlation spectroscopy, fluorescence anisotropy, dynamic light scattering, and rotational viscosity method) to measure the effect of ficoll crowding on the rotational and translational diffusion of Alexa488 (MW=665Da). We find the rotational and translational diffusion times to depend exponentially with on the ficoll concentration. This dependence cannot be accounted for by the changes of the bulk viscosity as would suggest the Stokes-Einstein model. Rather, they can be attributed to changes of the local microviscosity created by the ficoll-water system. However, Alexa488 appears to “observe” a reduced microviscosity (~ ½) for its rotational motion different from that “observed” while translating. In a second experiment, we assessed the possibility of resolving the structural differences between three amino-acids (L-Serine, L-Cysteine, and L-Glutamine) while embedded in a host ficoll solution. Here, we used laser-induced breakdown spectroscopy (LIBS) and measured the spectra emitted by the mixtures of ficoll and amino-acid. Data analysis yields subtle differences in the spectra, allowing classification of the spectra. Although additional work is needed, these preliminary results indicate the potential use of LIBS as a detection and characterization tool.
Funder Acknowledgement(s): National Science Foundation (NSF-CREST grant # 1242067)
Faculty Advisor: None Listed,