Biophotonics methods are attractive since they allow for the non-invasive diagnosis of cancer. Experiments
were carried out to investigate the feasibility of detecting early pre-cancer using optical spectroscopy. However,
optimization of instrumentation design parameters remains challenging because of the lack of metrics to evaluate
the performance of certain design parameters. For example, although using angled-collection geometry has been
shown to collect depth sensitive spatial origins, the performance of devices with angled-collection geometries
are not well characterized or quantified. In this study, we use a polarization-sensitive Monte Carlo simulation
(Pol-MC) to aid in the design of instrumentation for the early detection of epithelial cancer. The tissue is
modeled in layers: (0) air outside the tissue, (1) epithelial layer, (2) thin pre-cancer layer of cells, (3) thin
basement membrane, implemented as a thin transparent layer, and (4) the stroma, implemented as a thick layer
of scattering material. We propose a new metric, Target Signal Ratio (TSR), to evaluate the proportion of signal
that is scattered from a target layer, which is the basal/pre-cancer layer. This study is a proof-of-concept for
the application of computational techniques to facilitate instrument design.
Nanoparticles such as gold and silver with plasmonic resonances in the near-infrared (NIR) optical region,
where soft tissue is the most transparent, are of great interest in biomedical applications. A major roadblock
in translation of inorganic nanoparticles to clinical practice for systemic targeting of disease is their nonbiodegradable
nature. In addition, gold nanoparticles that absorb in the NIR are typically greater than 50 nm,
which is above the threshold size of 5.5 nm required for effective excretion from the body. Here we describe
a new class of biodegradable gold nanoparticles with plasmon resonances in the NIR region. The synthesis is
based on controlled assembly of very small (less than 5 nm) primary gold particles into nanoclusters with
sub-100 nm overall diameter and an intense NIR absorbance. The assembly is mediated by biodegradable
polymers, polyethylene glycol (PEG) and polylactic acid (PLA) copolymer, and small capping ligands on the
constituent nanoparticles. Nanoclusters deaggregate into sub-5nm primary gold particles upon biodegradation
of the polymer binder in live cells over one week, as shown by dark-field reflectance and hyperspectral
imaging.
Distance dependant coupling of plasmon resonances between closely spaced metal nanoparticles offers an attractive
alternative for the imaging of molecular interactions. Here we analyzed interactions between molecular specific gold
nanoparticles and live cells using a combination of dark-field reflectance and hyperspectral imaging. The results of
optical imaging were correlated with transmittance electron microscopy of cell slices and theoretical simulations of
optical properties of gold aggregates. We showed that nanoparticles targeted to epidermal growth factor receptor (EGFR)
form closely spaced assemblies in the presence of the target molecule. Our experiments with living cells showed that
receptor mediated assembly and plasmon coupling of gold bioconjugates result in a spectral shift of more than 100 nm in
plasmon resonance frequency of the nanoparticles giving a very bright red signal. We demonstrated that plasmon
coupling can be used for imaging of EGFR activation and trafficking as formation of EGFR dimers and further
intracellular uptake in early and late endosomes is associated with progressive color changes from green to red,
respectively, with each stage of EGFR cycle being associated with a distinct color of EGFR bound nanoparticles. This
approach can allow imaging of molecular interactions ranging from protein pairs to multi-protein complexes with
sensitivity and SNR that cannot be currently achieved with any other method.
Nanoparticles such as gold and silver with plasmonic resonances in the near-infrared (NIR) optical region,
where soft tissue is the most transparent, are of great interest in biomedical applications. A major roadblock
in translation of inorganic nanoparticles to clinical practice for systemic targeting of disease is their nonbiodegradable
nature. In addition, gold nanoparticles that absorb in the NIR are typically greater than 50 nm,
which is above the threshold size of 5.5 nm required for effective excretion from the body. Here we describe
a new class of biodegradable gold nanoparticles with plasmon resonances in the NIR region. The synthesis is
based on controlled assembly of very small (less than 5 nm) primary gold particles into nanoclusters with
sub-100 nm overall diameter and an intense NIR absorbance. The assembly is mediated by biodegradable
polymers, polyethylene glycol (PEG) and polylactic acid (PLA) copolymer, and small capping ligands on the
constituent nanoparticles. Nanoclusters deaggregate into sub-5nm primary gold particles upon biodegradation
of the polymer binder in live cells over one week, as shown by dark-field reflectance and hyperspectral
imaging.
Near-field coupling between plasmonic resonant nanoparticles and the associated shifts in scattering spectra
enables the accomplishment of unprecedented observation of the co-localization dynamics of in-situ biomolecules
on nanometer length-scales. We have recently shown that resonant nanoparticles conjugated to antibodies for
cell-surface receptors provide a sensitive probe allowing the unambiguous resolution of not only the time sequence,
but also the details of the intracellular pathway, for receptor-mediated endocytosis in live cells.
In terms of general principles, the classical electrodynamics determining the scattering cross-section for
nanoparticle aggregates is straightforward. However, the specifics of the angular dependence of the differential
cross-section at a single wavelength, the wavelength dependence of this cross-section, and the correct implementation
and interpretation of statistical averages of cross-section properties over an ensemble of aggregate
morphologies are generally quite complicated, and in fact are often misinterpreted in the literature.
Despite this complexity, we have constructed a set of few-parameter formulae describing optical scattering
from nanoparticle aggregates by judicious combination of experimental results with extensive, near-exact simulation
using the T-matrix technique. These phenomenological results facilitate the practical use of nanoparticle
aggregates for biological measurement and clinical therapeutic applications.
An effective cancer control strategy requires improved early detection methods, patient-specific drug selection, and the ability to assess response to targeted therapeutics. Recently, plasmon resonance coupling between closely spaced metal nanoparticles has been used to develop ultrasensitive bioanalytical assays in vitro. We demonstrate the first in vivo application of plasmon coupling for molecular imaging of carcinogenesis. We describe molecular-specific gold bioconjugates to image epidermal growth factor receptor (EGFR); these conjugates can be delivered topically and imaged noninvasively in real time. We show that labeling with gold bioconjugates gives information on the overexpression and nanoscale spatial relationship of EGF receptors in cell membranes, both of which are altered in neoplasia. EGFR-mediated aggregation of gold nanoparticles in neoplastic cells results in more than a 100-nm color shift and a contrast ratio of more than tenfold in images of normal and precancerous epithelium in vivo, dramatically increasing contrast beyond values reported previously for antibody-targeted fluorescent dyes.
In an optical stretcher, infrared laser light is used to exert surface stress on biological cells, causing an elongation of the trapped cell body along the laser beam axis. These optically induced deformations characterize individual cells and cell lines. When integrated within a microfluidic chamber with high throughput, this enables diagnosis of diseases, on a cellular level, that are associated with cytoskeletal processes. Additionally, it allows sorting of cells with high accuracy in a non-contact manner. To determine the surface stress on the cell, ray optics calculations as well as the system transfer operator (T-matrix) approach with an appropriate incident field are used. The latter approach allows a more accurate modeling of the cell in the optical stretcher and reveals a more detailed stress profile acting on the cell surface. Analyzing the deformation behavior of normal and malignantly transformed fibroblasts, significant differences in axial elongation even for sample sizes as low as 30 cells are already measurable on a time scale of 0.1s. Here, malignant transformation of cells is discussed as an example of how any process that affects the cell's optical or mechanical properties allows classification with the optical stretcher.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.