6 research outputs found
ΠΡΡΠΎΡΠΈΠΊΠΎ-ΠΏΠ΅Π΄Π°Π³ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΎΠ±Π·ΠΎΡ Π΄Π΅ΡΡΠΊΠΎΠΉ Π±Π΅ΡΠΏΡΠΈΠ·ΠΎΡΠ½ΠΎΡΡΠΈ Π² ΠΡΠ΅Π²Π½Π΅ΠΉ Π ΡΡΠΈ ΠΈ ΠΈΠΌΠΏΠ΅ΡΠ°ΡΠΎΡΡΠΊΠΎΠΉ Π ΠΎΡΡΠΈΠΈ
Axially resolved microphotoluminescence mapping of semiconductor
nanowires held in an optical tweezers reveals important new experimental
information regarding equilibrium trapping points and trapping stability
of high aspect ratio nanostructures. In this study, holographic optical
tweezers are used to scan trapped InP nanowires along the beam direction
with respect to a fixed excitation source and the luminescent properties
are recorded. It is observed that nanowires with lengths on the range
of 3β15 ΞΌm are stably trapped near the tip of the wire
with the long segment positioned below the focus in an inverted trapping
configuration. Through the use of trap multiplexing we investigate
the possibility of improving the axial stability of the trapped nanowires.
Our results have important implication for applications of optically
assisted nanowire assembly and optical tweezers based scanning probes
microscopy
Paper-Based Sensor for Monitoring Sun Exposure
An
easy to use and easy to fabricate sun exposure sensor was prepared
via the inkjet printing of titanium dioxide (TiO<sub>2</sub>), polyvinylpyrrolidone
(PVP), and food dye on paper. The sun exposure sensor works by employing
titanium dioxide (TiO<sub>2</sub>) as a photocatalyst to degrade the
food dyes resulting in gradual discoloration of this film. The PVP
serves as a binder to allow film formation. The discoloration can
be observed by the naked eye or quantitatively monitored using UVβvis
reflectance spectra. Finally, discoloration of the films was calibrated
to match UV exposure time of different skin types, by using different
UV neutral density filters with the ability to transmit between 1.5%
and 70% of the irradiant UV light from the sources to the photoactive
film
Antibody Modified Porous Silicon Microparticles for the Selective Capture of Cells
Herein, the ability of porous silicon
(PSi) particles for selectively
binding to specific cells is investigated. PSi microparticles with
a high reflectance band in the reflectivity profile are fabricated,
and subsequently passivated and modified with antibodies via the CuΒ(I)-catalyzed
alkyneβazide cycloaddition reaction and succimidyl activation.
To demonstrate the ability of the antibody-modified PSi particles
to selectively bind to one cell type over others, HeLa cells were
transfected with surface epitopes fused to fluorescent proteins. The
antibody-functionalized PSi particles showed good selectivity for
the corresponding surface protein on HeLa cells, with no significant
cross-reactivity. The results are important for the application of
PSi particles in cell sensing and drug delivery
Media 2: Spectroscopy of 3D-trapped particles inside a hollow-core microstructured optical fiber
Originally published in Optics Express on 07 May 2012 (oe-20-10-11232
Ultrasensitive and Specific Measurement of Protease Activity Using Functionalized Photonic Crystals
Herein
is presented a microsensor technology as a diagnostic tool
for detecting specific matrix metalloproteinases (MMPs) at very low
concentrations. MMP-2 and MMP-9 are detected using label free porous
silicon (PSi) photonic crystals that have been made selective for
a given MMP by filling the nanopores with synthetic polymeric substrates
containing a peptide sequence for that MMP. Proteolytic cleavage of
the peptide sequence results in a shift in wavelength of the main
peak in the reflectivity spectrum of the PSi device, which is dependent
on the amount of MMP present. The ability to detect picogram amounts
of MMP-2 and MMP-9 released by primary retinal pigment epithelial
(RPE) cells and iris pigment epithelial (IPE) cells stimulated with
lipopolysaccharide (LPS) is demonstrated. It was found that both cell
types secrete higher amounts of MMP-2 than MMP-9 in their stimulated
state, with RPE cells producing higher amounts of MMPs than IPE cells.
The microsensor performance was compared to conventional protease
detection systems, including gelatin zymography and enzyme linked
immunosorbent assay (ELISA). It was found that the PSi microsensors
were more sensitive than gelatin zymography; PSi microsensors detected
the presence of both MMP-2 and MMP-9 while zymography could only detect
MMP-2. The MMP-2 and MMP-9 quantification correlated well with the
ELISA. This new method of detecting protease activity shows superior
performance to conventional protease assays and has the potential
for translation to high-throughput multiplexed analysis
Versatile βClick Chemistryβ Approach to Functionalizing Silicon Quantum Dots: Applications toward Fluorescent Cellular Imaging
In this study, we describe a solution
procedure for the preparation
and surface modification of photostable colloidal silicon quantum
dots (SiQDs) for imaging of cancer cells. Photoluminescent SiQDs were
synthesized by reduction of halogenated silane precursors using a
microemulsion process. It was shown that 1,8-nonadiyne molecules could
be grafted onto the surface of hydrogen-terminated SiQDs via ultraviolet
(UV)-promoted hydrosilylation, demonstrated by Fourier transform infrared
spectroscopy (FTIR) measurements. In addition, various azide molecules
were coupled onto nonadiyne-functionalized particles, rendering particles
dispersible in selected polar and nonpolar solvents. The photoluminescence
of functionalized SiQDs was stable against photobleaching and did
not vary appreciably within biologically applicable pH and temperature
ranges. To demonstrate compatibility with biological systems, water-soluble
SiQDs were used for fluorescent imaging of HeLa cells. In addition,
the SiQDs were shown to be non-cytotoxic at concentrations up to 240
ΞΌg/mL. The results presented herein provide good evidence for
the versatility of functionalized SiQDs for fluorescent bioimaging
application