Semester of Graduation

Fall 2018


Master of Science in Mechanical Engineering (MSME)


Mechanical and Industrial Engineering

Document Type



Orientation of plasmonic nanostructures is an important feature in many nanoscale applications such as photovoltaics, catalyst, biosensors DNA interactions, protein detections, hotspot of surface-enhanced Raman spectroscopy (SERS), and fluorescence resonant energy transfer (FRET) experiments. Silver nanocubes with significant spectral signatures between 400-700 nm are observed in this experimental research. Whereas study of single cells will enable the analysis of cell-to-cell variations within a heterogeneous population. These variations are important for further analysis and understanding of disease propagation, drug development, stem cell differentiation, embryos development, and how cells respond to each other and their environment. Adipose-derived mesenchymal stem cells possess the capability to undergo differentiation into adipocytes, chondrocytes, and adipocytes and convert to adipose tissues, bones, and cartilages respectively. This regenerative ability has augmented stem-cell research and the need to characterize them quickly with minimal invasiveness. An imaging and spectroscopic technology supported with correlative techniques which can address the capability to probe single stem-cell and single nanostructure non-invasively, without photo bleaching, is accurate, quick, cost-efficient, requires simple sample preparation, and curbs diffraction limitations are implemented in this research.

Almost a decade ago, Hyperspectral Imaging (HSI) was employed by the NASA in satellite imaging applications such as remote sensing technology. This technology has since been extensively used in the exploration of minerals, agricultural purposes, water resources, and urban development needs. Due to recent advancements in optical re-construction, imaging, and advance computing technologies, HSI can now be applied down to micro- and nano-meter scales possibly allowing for exquisite control and quantitative spectral analysis of single nanostructures to ensemble spectroscopy and single cell to complex biological systems.

In this work, we use transmitted dark field imaging technique to locate individual nanostructure and single stem-cell on a glass substrate. Then we employ a hyperspectral imaging technique within Vis-NIR spectrum (400-900 nm) at the same spot to collect spectral response of a single silver nanoparticle and single ASCs. No special tagging or staining of the nanoparticle or biological cell has been done, as more likely required in traditional microscopy techniques. Different orientations exhibiting dissimilar dipole moments and differentiated stem-cells with variable tissue scattering have been identified by carefully understanding and analyzing shift in spectral response from the sample.

The orientations measured by hyperspectral microscopy were validated using the finite difference time domain (FDTD) electrodynamics calculations and correlative scanning electron microscopy (SEM) analysis. The combination of high resolution nanometer-scale imaging techniques and the modern numerical modeling capacities thus enables a meaningful advance in our knowledge of manipulating plasmon response and fabricating shaped nanostructures. To obtain insight of single molecule-level proteins, fats, and other constituents, matrix-assisted laser deposition/ionization (MALDI) was performed on stem-cells. Spectra collected from these mono-constituents were required to create libraries. Using the library data, then cells were mapped via single angle mapping (SAM) algorithms. The optical images were characterized using template match and edge detection algorithms to analyze the cell differentiation. Developing this label-free protocol enables the possibility to non-invasively analyze stem cell differentiation.

This work has advanced our understanding of the behavior of small nanoparticle clusters and single stem cell probing protocol useful for sensing, nanomedicine, tissue regeneration, cellular morphological analysis, and surface sciences.



Committee Chair

Gartia, Manas