Measuring cell growth on adhesive substrates is critical for understanding cell biophysical properties and drug response. Traditional optical techniques have low sensitivity and vary in reliability depending on cell type, while microfluidic technologies rely on cell suspension. In this study, a new platform has been developed that is able to measure the weight and growth of individual cells in real−time. The platform can determine the growth rates of cells in just 10 minutes and map the growth of cell populations in short intervals. It can also identify differences in the growth of different subpopulations within a larger group. The platform was used to study the growth of MCF−7 cells and the impact of two intracellular metabolic processes on cell proliferation. The platform demonstrated the negative effect of serum starvation on cell growth and the role of a particular enzyme, ornithine decarboxylase (ODC), in cell proliferation. It was also able to show the ability of an external factor, putrescine, to rescue cells from the inhibitory effects of low osmolarity. In addition to measuring intracellular processes, the platform can determine the response of cancer cells to drug treatment. It showed the susceptibility of MCF−7 cells to a particular drug, difluoromethylornithine (DFMO), and the ability of a resistant subpopulation to survive in the presence of the drug. The platform’s ability to quickly measure cell growth in small samples makes it a potential tool for both research and clinical use.
The development of rapid diagnostic kits is very critical for the early diagnosis and treatment of infectious diseases. In this study, a lightweight and field-portable biosensor that uses a plasmonic chip based on nanohole arrays integrated into a lens-free imaging framework was presented for label-free virus detection in field settings. A high-efficiency CMOS camera was used in the biosensor platform to observe the diffraction field patterns of nanohole arrays under uniform illumination from a spectrally-tuned LED source, which is specifically configured to excite the plasmonic mode supported by the nanohole arrays. The portable biosensor presented reliable labelfree detection of H1N1 viruses and produced accurate results at medically relevant concentrations. A low-cost and user-friendly sample preparation kit was developed in order to prepare the surface of the plasmonic chip for analyte binding, e.g., virus-antibody binding. A Python-based graphical user interface (GUI) was also developed to make it easy for the user to access the biosensor hardware, capture and process diffraction field images, and present virus information to the end-user. The portable biosensor platform employs nanohole arrays and lens-free imaging for highly sensitive virus detection with an LOD of 103 TCID50/mL. It is accurate and efficient, making it suitable for diagnostic use in resource-limited settings where access to advanced equipment may be limited. The presented platform technology could quickly adapt to capture and detect other different viral diseases, e.g., COVID-19 or influenza by simply coating the plasmonic chip surface with an antibody possessing affinity to the virus type of interest.
In this work, we studied the multi-band plasmonic UT graphene antenna arrays. The proposed model shows three different resonance frequencies. We show nearfield distributions of corresponding resonance frequencies and investigate the effect of the geometrical parameters, chemical potential, relaxation time, thickness of the substrate and different refractive index of the material on the spectral position of the UT-shaped graphene antenna.
We demonstrate a composite metamaterial composed of two asymmetrically oriented π-shaped structures that
exhibits plasmonic analogue of electromagnetically induced transparency (EIT). The structure exhibits fine
tuning of EIT-like spectral behavior and spatial control of near-field intensity distribution. Originated from the
asymmetric design, we introduce a more compact system which possesses the similar EIT-like spectral response
as well as much smaller optical mode volumes.
KEYWORDS: Antennas, Metamaterials, Near field, Plasmonics, Nanolithography, Optical properties, Electron beam lithography, Reactive ion etching, Scanning electron microscopy, Optical filters
In this paper, we present numerical and experimental results on optical properties of a multi-resonant UT-shaped
plasmonic nanoaperture antenna for enhanced optical transmission and near-field resolution. We propose different
structure designs in order to prove the effect of geometry on resonance spectrum and near-field enhancement.
Theoretical calculations of transmission spectra and field distributions of UT-shaped nano-apertures are performed by
using three-dimensional finite-difference time-domain method. The results of these numerical calculations show that
transmission through the apertures is indeed concentrated in the gap region. In addition to theoretical calculations, we
also performed a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography
(EBL) and reactive ion etching in order to fabricate UT-shaped nanostructures. For further confirmation of the multiresonant
behavior, we checked the individual U-and T-shaped nano-aperture antenna responses. We also studied the
parameter dependence of the structure to determine the control mechanism of the spectral response. Theoretical
calculations are supported with experimental results to prove the enhanced field distribution and multi-resonant behavior
which can be suitable for infrared detection of biomolecules, wavelength-tunable filters, optical modulators, and ultrafast
switching devices.teInp
In this work, we propose a unique plasmonic substrate that combine the strength of localized and extended surface
plasmons for optical trapping, spectroscopy and biosensing, all in the same platform. The system is based on
periodic arrays of gold nanopillars fabricated on a thin gold sheet. The proposed periodic structure exhibits high
refractive index sensitivities, as large as 675 nm/RIU which is highly desirable for biosensing applications. The
spectrally sharp resonances, we determine a figure of merit, as large as 112.5. The nanopillar array also supports
easily accessible high near-field enhancements, as large as 10.000 times, for surface enhanced spectroscopy. The
plasmonic hot spots with high intensity enhancement lead to large gradient forces, 350 pN/W/μm2, needed for
optical trapping applications.
KEYWORDS: Antennas, Metamaterials, Nanolithography, Near field optics, Transmittance, Metals, Electron beam lithography, Nanostructures, Near field, Optical resolution
The subject of light transmission through optically thin metal films perforated with arrays of subwavelength nanoholes
has recently attracted significant attention. In this work, we present experimental and calculated results on optical
transmission/reflection of the U-shaped nanoapertures for enhanced optical transmission and resolution. We propose
different structure designs in order to prove the effect of geometry on resonance and enhanced fields. Theoretical
calculations of transmission/reflection spectra and field distributions of U-shaped nano-apertures are performed by using
3-dimensional finite-difference time-domain method. The results of these numerical calculations show that transmission
through the apertures is indeed concentrated in the gap region. Added to theoretical calculations we also performed a liftoff
free plasmonic device fabrication technique based on positive resist electron beam lithography and reactive ion
etching in order to fabricate U-shaped nanostructures. After transferring nanopattern on 80 nm thick suspended SiNx
membrane using EBL followed by dry etching, a directional metal deposition processes is used to deposit 5 nm thick Ti
and 30 nm thick Au layers. Theoretical calculations are supported with experimental results to prove the tunability of
resonances with the geometry at the mid-infrared wavelengths which could be used for infrared detection of
biomolecules.
We have studied the surface plasmon theory with Bloch's hydrodynamic model. The results of the analysis
done by Bloch model have been compared with the ones done with Drude model and the dominant differences
between two models in valid frequency range have been shown. The transmittance of the slit embedded in a
metal layer has been investigated by these models and the differences have been emphasized. An electron density
dependent parameter defined by Bloch model has been used to control the transmission behavior of the light
through nano-apertures. A system consisting of a nano-slit formed in a metal layer with a periodically textured
surface used for beam focusing has been introduced and how the focusing capacity of the system is controlled
by the parameter defined by Bloch model has been shown.
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