In this paper, we present an original concept of plasmonic-related instrumentation platform dedicated to diagnostic biosensing tests out of the laboratory. The developed instrumental platform includes both disposable one-use microfluidic affinity biochip and compact optical readout device for biochip monitoring involving mobile Internet devices for data processing and communication. The biochip includes both microfluidic and optical coupling structures formed into a single plastic slab. The microfluidic path of the biochip operates in passive capillary pumping mode. In the proof-of-concept prototype, we address specifically the sensing format involving Surface Plasmon Resonance phenomenon. The biochip is plugged in the readout device without the use of an index matching fluid. An essential advantage of the developed biochip is that its implementation involves conventional hot embossing and thin film deposition process, perfectly suited for mass production of low-cost microfluidic biochip for biochemical applications.
In this paper some basic investigations about laser-induced contamination are reported. As contamination materials pure
aromatic hydrocarbons (naphthalene and anthracene) were used. A particular focus of the tests was to investigate the
impact of laser-induced contamination on damage threshold. Onset and evolution of deposit formation and damage were
observed in-situ by laser-induced fluorescence and transmission monitoring. As optical samples uncoated fused silica
substrates and AR and HR coated optics with different coating morphology, depending on coating process (e-beam,
magnetron sputtering) were investigated. Ex-situ characterization of deposits and damage morphology was performed by
differential interference contrast, fluorescence, and atomic force microscopy. The tests were run with pulsed UV light at
355 nm. Partial pressure of contamination material in the range of 10-4 mbar induced a drastic reduction of laser damage threshold compared to values obtained without contamination.
Pathogens could be inactivated via a light source coupled with a photosensitizing agent in photodynamic
antimicrobial chemotherapy (PACT). This project studied the effect of non-homogenous substrate on cell
colony. The non-homogeneity could be controlled by iron oxide nano-particles doping in porous glassy
substrates such that each cell would experience tens of hot spots when illuminated with additional light source.
The substrate non-homogeneity was characterized by Atomic Force Microscopy, Transmission Electron
Microscopy and Extended X-Ray Absorption Fine Structure at Brookhaven Synchrotron Light Source.
Microscopy images of cell motion were used to study the motility. Laboratory cell colonies on non-homogenous
substrates exhibit reduced motility similar to those observed with sub-lethal PCAT treatment. Such motility
reduction on non-homogenous substrate is interpreted as the presence of thermal stress. The studied pathogens
included E. coli and Pseudomonas aeruginosa. Non-pathogenic microbes Bacillus subtilis was also studied for
comparison. The results show that sub-lethal PACT could be effective with additional non-homogenous thermal
stress. The use of non-uniform illumination on a homogeneous substrate to create thermal stress in sub-micron
length scale is discussed via light correlation in propagation through random medium. Extension to sub-lethal
PACT application complemented with thermal stress would be an appropriate application.
Human (and other mammals) would secrete cerumen (ear wax) to protect the skin of the ear canal against
pathogens and insects. The studies of biodiversity of pathogen in human include intestine microbe colony, belly
button microbe colony, etc. Metals such as zinc and iron are essentials to bio-molecular pathways and would be
related to the underlying pathogen vitality. This project studies the biodiversity of cerumen via its metal content
and aims to develop an optical probe for metal content characterization. The optical diffusion mean free path and
absorption of human cerumen samples dissolved in solvent have been measured in standard transmission
measurements. EXFAS and XANES have been measured at Brookhaven Synchrotron Light Source for the
determination of metal contents, presumably embedded within microbes/insects/skin cells. The results show that
a calibration procedure can be used to correlate the optical diffusion parameters to the metal content, thus
expanding the diagnostic of cerumen in the study of human pathogen biodiversity without the regular use of a
synchrotron light source. Although biodiversity measurements would not be seriously affected by dead microbes
and absorption based method would do well, the scattering mean free path method would have potential to
further study the cell based scattering centers (dead or live) via the information embedded in the speckle pattern
in the deep-Fresnel zone.
Blood protein molecules could be embedded in porous glassy substrate with 10-nm pores. The embedding
principle is based on blood cell dehydration with the destruction of the cell membrane, and reconstitution and
centrifuge could yield a suitable solution for doping into a porous glassy medium. The doped glassy substrate
speckle pattern under laser illumination could be used to characterize the protein size distribution. Calibration
with known protein embedded samples would result in an optical procedure for the characterization of a blood
sample. Samples embedded with larger kilo-Dalton protein molecule show more variation in the speckle
patterns, consistent with protein folding interaction inside a pore cavity. A regression model has been used to
correlate the protein molecule sizes with speckle sizes. The use of diffusion mean free path information to study
protein folding in the embedding process is briefly discussed.
Cell density is an important parameter in the question of bio-variation and the studying of cell scattering could
be a viable tool. The development of spatially resolved optical fiber probe would enable the characterization of
optical scattering from cells within a colony. Single mode fiber probe would be budget friendly as compared to a
50-nm sub-cellular fiber probe. This project develops a calibration procedure to correlate the optical scattering
measured by a single mode fiber probe to that of a 50-nm sub-cellular fiber probe in the context of cell density
variation. The Fourier transform of intensity angular transmission would give correlation information in the Efield
in the spatial coordinate. Monte Carlo simulation could be used to constrain the input intensity function
spatial content resembling microscopy. The use of a 50-nm sub-cellular fiber probe for detailed study of
biological samples would give sub-micron scale length information.
Macro-bending fiber optic based heart-rate and pulse pressure shape monitors have been fabricated and tested for
non-invasive measurement. Study of fiber bending loss and its stability and variations are very important
especially for sensor designs based on optical fiber bending. Wavelengths from 1300 nm to 1550 nm have been
used with fabrication based on multimode fiber, single mode fiber, and photonic crystal fiber. The smallest
studied curvature would demand the use of single mode standard fibers. The collected data series show high
quality suitable for random series analysis. Fractal property of optically measured pulse pressure data has been
observed to correlate with physical activity. Correlation to EKG signal suggests that the fabricated monitors are
capable of measuring the differential time delays at wrist and leg locations. The difference in time delay could
be used to formulate a velocity parameter for diagnostics. The pulse shape information collected by the fiber
sensor provides additional parameters for the analysis of the fractal nature of the heart. The application to real
time measurement of blood vessel stiffness with this optical non-invasive fiber sensor is discussed.
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