9 research outputs found
Nanostructured Antagonist of Extrasynaptic NMDA Receptors
Glutamatergic
cytotoxicity mediated by overactivation of <i>N</i>-methyl-d-aspartate receptors (NMDARs) is implicated in numerous neurological
disorders. To be therapeutically viable, NMDAR antagonists must preserve
physiological role of synaptic NMDARs (sNMDARs) in synaptic transmission
and block only excessive pathological activation of NMDARs. Here we
present a novel NMDAR antagonist that satisfies this two-fold requirement
by exploiting spatial differences in NMDAR subcellular locations.
Specifically, we designed a hybrid nanodrug (AuM) to be larger than
the synaptic cleft by attaching memantine, NMDAR antagonist, via polymer
linkers to a gold nanoparticle. We show that AuM efficiently and selectively
inhibited extrasynaptic NMDARs (eNMDARs), while having no effect on
sNMDARs and synaptic transmission. AuM exhibited neuroprotective properties
both in vitro and ex vivo during such neurotoxic insults as NMDAR-mediated
cytotoxicity in cerebrocortical cell culture and oxygen-glucose deprivation
in acute hippocampal slices. Furthermore, AuM prevented dendritic
spine loss triggered by AĪ² oligomers in organotypic hippocampal
slices and was more effective than free memantine. Using a novel rational
design strategy, we demonstrate a proof of concept for a new class
of neuroprotective drugs that might be beneficial for treatment of
several neurological disorders
Biotags Based on Surface-Enhanced Raman Can Be as Bright as Fluorescence Tags
Surface enhanced Raman spectroscopy
(SERS) is a powerful analytical technique that has been proposed as
a substitute for fluorescence for biological imaging and detection
but is not yet commercially utilized. The reason lies primarily in
the lower intensity and poor reproducibility of most metal nanoparticle-based
tags as compared to their fluorescence-based counterparts. Here, using
a technique that scrupulously preserves the same number of dye molecules
in both the SERS and fluorescence measurements, we show that SERS-based
biotags (SBTs) with highly reproducible optical properties can be
nanoengineered such that their brightness is at least equal to that
of fluorescence-based tags
Robust SERS Enhancement Factor Statistics Using Rotational Correlation Spectroscopy
We characterize the distribution of surface-enhanced
Raman spectroscopy
(SERS) enhancement factors observed in individual hot spots of single
Ag ānanocapsulesā, encapsulated Ag nanoparticle dimers
formed via controlled nanoparticle linking, polymer encapsulation,
and small molecule infusion. The enhancement factors are calculated
for over 1000 individual nanocapsules by comparing Raman scattering
intensities of 4-mercaptobenzoic acid (MBA) measured from single SERS
hot spots to intensities measured from high-concentration solutions
of MBA. Correlation spectroscopy measurements of the rotational diffusion
identify nanocapsules with signals dominated by single hot spots via
their strong polarization response. Averaging over the entire surface
of the nanocapsules, the distribution of enhancement factors is found
to range from 10<sup>6</sup> to 10<sup>8</sup>, with a mean of 6 Ć
10<sup>6</sup>. Averaging only over nanoparticle junctions (where
most SERS signals are expected) increases this average value to 10<sup>8</sup>, with a range from 2 Ć 10<sup>7</sup> to 2 Ć 10<sup>9</sup>. This significant statistical sampling shows that very high
SERS enhancement factors can be obtained on a consistent basis using
nanoparticle linking
Rapid Identification by Surface-Enhanced Raman Spectroscopy of Cancer Cells at Low Concentrations Flowing in a Microfluidic Channel
Reliable identification and collection of cells from bodily fluids is of growing interest for monitoring patient response to therapy and for early detection of disease or its recurrence. We describe a detection platform that combines microfluidics with surface-enhanced Raman spectroscopy (SERS) for the identification of individual mammalian cells continuously flowing in a microfluidics channel. A mixture of cancerous and noncancerous prostate cells was incubated with SERS biotags (SBTs) developed and synthesized by us, then injected into a flow-focused microfluidic channel, which forces the cells into a single file. The spectrally rich SBTs are based on a silver nanoparticle dimer core labeled with a Raman-active small reporter molecule paired with an affinity biomolecule, providing a unique barcode whose presence in a composite SERS spectrum can be deconvoluted. Individual cancer cells passing through the focused laser beam were correctly identified among a proportionally larger number of other cells by their Raman signatures. We examine two deconvolution strategies: principal component analysis and classical least-squares. The deconvolution strategies are used to unmix the overall spectrum to determine the relative contributions between two SBT barcodes, where one SBT barcode indicates neuropilin-1 overexpression, while a second SBT barcode is more universal and indicates unspecific binding to a cellās membrane. Highly reliable results were obtained for all of the cell mixture ratios tested, the lowest being 1 in 100 cells
Composite Porous SiliconāSilver Nanoparticles as Theranostic Antibacterial Agents
A theranostic
nanoparticle with biochemically triggered antibacterial
activity is demonstrated. Metallic silver is deposited onto porous
silicon nanoparticles (pSiNPs) by galvanic displacement. When aqueous
diaminesilver ([AgĀ(NH<sub>3</sub>)<sub>2</sub>]<sup>+</sup>) is used
as a silver source, the pSiNPs template the crystalline silver as
small (mean diameter 13 nm) and well-dispersed nanoparticles embedded
within and on the larger (100 nm) pSiNPs. The silver nanoparticles
(AgNPs) quench intrinsic photoluminescence (PL) from the porous silicon
(pSi) matrix. When exposed to an aqueous oxidant, the AgNPs are preferentially
etched, Ag<sup>+</sup> is released into solution, and PL from the
pSi carrier is recovered. The released Ag<sup>+</sup> results in 90%
killing of (Gram-negative) <i>Pseudomonas aeruginosa</i> and (Gram-positive) <i>Staphylococcus aureus</i> within
3 h. When conjugated with the TAT peptide (sequence RKKRRQRRR), the
silver-deposited porous silicon (pSi-Ag) nanocomposite shows distinct
targeting toward <i>S. aureus</i> bacteria in vitro. Intravenously
injected TAT-conjugated pSi-Ag nanoparticles accumulate in the liver,
spleen, and lungs of mice, and the in vivo release of Ag<sup>+</sup> and recovery of PL from pSi are demonstrated by the subsequent intraperitoneal
administration of a hexacyanoferrate solution. The released Ag<sup>+</sup> leads to a significant bacterial count reduction in liver
tissue relative to the control. The data demonstrate the feasibility
of the targeted and triggered delivery of antibacterial Ag<sup>+</sup> ion in vivo, using a self-reporting and nontoxic nanocarrier
Modular Plasmonic Nanocarriers for Efficient and Targeted Delivery of Cancer-Therapeutic siRNA
We have combined a versatile and
powerful route to deliver nucleic
acids with peptide-based cell-specific targeting. siRNA targeting
the polo-like kinase gene is in clinical trials for cancer treatment,
and here we deliver this RNA selectively to cancer cells displaying
the neuropilin-1 epitope using gold nanoshells. Release of the siRNA
from the nanoparticles results from irradiation with a pulsed near-infrared
laser, which also provides efficient endosomal escape within the cell.
As a result, our approach requires 10-fold less material than standard
nucleic acid transduction materials and is significantly more efficient
than other particle-based methods. We also describe a particleānucleic
acid design that does not rely on modified RNA, thereby making the
preparation of these materials more efficient and much less expensive.
These improvements, when combined with control over when and where
the siRNA is released, could provide the basis for diverse cell biological
studies
Targeted Intracellular Delivery of Proteins with Spatial and Temporal Control
While
a host of methods exist to deliver genetic materials or small
molecules to cells, very few are available for protein delivery to
the cytosol. We describe a modular, light-activated nanocarrier that
transports proteins into cells by receptor-mediated endocytosis and
delivers the cargo to the cytosol by light triggered endosomal escape.
The platform is based on hollow gold nanoshells (HGN) with polyhistidine
tagged proteins attached through an avidity-enhanced, nickel chelation
linking layer; here, we used green fluorescent protein (GFP) as a
model deliverable cargo. Endosomal uptake of the GFP loaded nanocarrier
was mediated by a C-end Rule (CendR) internalizing peptide fused to
the GFP. Focused femtosecond pulsed-laser excitation triggered protein
release from the nanocarrier and endosome disruption, and the released
protein was capable of targeting the nucleoli, a model intracellular
organelle. We further demonstrate the generality of the approach by
loading and releasing Sox2 and p53. This method for targeting of individual
cells, with resolution similar to microinjection, provides spatial
and temporal control over protein delivery
Thermoswitchable Nanoparticles Based on Elastin-like Polypeptides
The design of biocompatible particles
with defined size on the nanometer scale has proven to be a challenging
task in current biomedical research. Here we present an approach toward
temperature-responsive nanoparticles by covalently cross-linking micelles
based on trimeric constructs of elastin-like polypeptides. These trimers
can be triggered to assemble into micelles by heating the solution
above a specific transition temperature (<i>T</i><sub>t</sub>) which was shown in previous studies. Here we show that the disassembly
of the micelles below the <i>T</i><sub>t</sub> can be prevented
by the incorporation of covalent cross-links in the core of the micelles.
This facilitates a temperature-triggered swelling and collapsing by
around 35% in diameter, as determined by dynamic light scattering.
Size distribution was confirmed by fluorescence correlation spectroscopy,
atomic force microscopy, and transmission electron microscopy. We
show switchable nanoparticles with reversible volume changes in the
temperature region between 30 and 40 Ā°C, making these particles
promising candidates for switchable drug delivery carriers
Mesoporous Multifunctional Upconversion Luminescent and Magnetic āNanorattleā Materials for Targeted Chemotherapy
Nanorattles consisting of hydrophilic, rare-earth-doped NaYF<sub>4</sub> shells each containing a loose magnetic nanoparticle were fabricated through an ion-exchange process. The inner magnetic Fe<sub>3</sub>O<sub>4</sub> nanoparticles are coated with a SiO<sub>2</sub> layer to avoid iron leaching in acidic biological environments. This multifunctional mesoporous nanostructure with both upconversion luminescent and magnetic properties has excellent water dispersibility and a high drug-loading capacity. The material emits visible luminescence upon NIR excitation and can be directed by an external magnetic field to a specific target, making it an attractive system for a variety of biological applications. Measurements on cells incubated with the nanorattles show them to have low cytotoxicity and excellent cell imaging properties. In vivo experiments yield highly encouraging tumor shrinkage with the antitumor drug doxorubicin (DOX) and significantly enhanced tumor targeting in the presence of an applied magnetic field