KEYWORDS: Wavelets, Cerebral blood flow, Signal processing, Brain, Near infrared, Interference (communication), Signal analyzers, Fourier transforms, Prefrontal cortex, Data modeling
Near Infrared Imager (NIRI) has been widely used to access the brain functional activity non-invasively. We use a
portable, multi-channel and continuous-wave NIR topography instrument to measure the concentration changes of each
hemoglobin species and map cerebral cortex functional activation. By extracting some essential features from the BOLD
signals, optical tomography is able to be a new way of neuropsychological studies. Fourier spectral analysis provides a
common framework for examining the distribution of global energy in the frequency domain. However, this method
assumes that the signal should be stationary, which limits its application in non-stationary system. The hemoglobin
species concentration changes are of such kind. In this work we develop a new signal processing method using
Hilbert-Huang transform to perform spectral analysis of the functional NIRI signals. Compared with wavelet based
multi-resolution analysis (MRA), we demonstrated the extraction of task related signal for observation of activation in
the prefrontal cortex (PFC) in vision stimulation experiment. This method provides a new analysis tool for functional
NIRI signals. Our experimental results show that the proposed approach provides the unique method for reconstructing
target signal without losing original information and enables us to understand the episode of functional NIRI more
precisely.
The real-time and quantitative detection assay is important for the gene detection. With the TaqMan probes for the
detection based polymerase chain reaction (PCR), four targets could be checked in a single process in solution assay. A
new method is developed to immobilize the TaqMan probes on a microarray, which could be used to the multi-target
gene fragment quantitative detection with PCR. A new type microarray scanner is designed for the assay. A thermocycler
system was built into the scanner platform. A new type of the vessel sealed with the gene amplification solution which
could perform the thermo-cycling and scanning. To decrease the background intensity a confocal system was used as the
fluorescent intensity detection in the scanner. To calculate the gene quantity, a standard liner graph was draw with the
fluorescent intensity versus the cycles. From the standard liner, the quantity of the original gene fragment could be
calculated in time with the cycles. This scanner offers the great advantage of real-time quantitative detection of DNA
targets in a microarray.
A 16-channel near-infrared spectroscopy (NIRS) was used to measure concentration changes of oxygenated and
deoxygenated hemoglobin (oxy-HB and deoxy-HB) in prefrontal area while the subjects were performing mental works.
Thirty healthy college participants were administered two mental arithmetic tasks while the changes of concentration on
oxy-HB and deoxy-HB were measured. Oxy-HB increased during the mental works, and the increases of oxy-HB were
greater in male subjects than in female subjects during the difficult task. These results suggest that NIRS is sensitive to
evaluate the oxy-HB activity of prefrontal cortex during mental works.
KEYWORDS: Molecules, Atomic force microscopy, Silicon, Molecular self-assembly, Mica, Americium, System on a chip, Chemistry, Molecular interactions, Oxidation
We have developed a practical method to control the number of attaching biomolecules to an AFM tip. Monolayer of OEG that has little interaction with some biomolecules was self-assembled on tips. Electric pulses were used to oxidize a patch of OEG monolayer on tip and generate COOH groups for further linking at the activated area. The surface groups were detected by chemical force titration. The total numbers of molecule bound on the tip was examined by the studies of biotin/streptavidin system.
A new technique to analyze methylation patterns in several adjacent CpG sites was developed and reported here. We selected a 336bp segment of the 5’-untranslated region and the first exon of the p16Ink4a gene, which include the most densely packed CpG fragment of the islands containing 32 CpG dinucleotides, as the investigated target. The probes that include all types of methylation patterns were designed to fabricate a DNA microarray to determine the methylation patterns of seven adjacent CpG dinucleotides sites. High accuracy and reproducibility were observed in several parallel experiments. The results led us to the conclusion that the methylation oligonucleotide microarray can be applied as a novel and powerful tool to map methylation patterns and changes in multiple CpG island loci in a variety of tumors.
The shrinkage of polyurethane stamps used for the in situ synthesis of DNA microarrays via molecular stamping method was studied with Micron XYZ Scope. It was found that the polyurethane stamp fixed on the epoxy resin modified glass strongly and showed minimum linear shrinkage. The linear shrinkage of the whole polyurethane stamp and that of each feature of polyurethane stamp were controlled within 0.0341% and 0.309%, respectively, which were due to the strong van der Waals forces and hydrogen bonds between polyurethane and epoxy resin. It was also confirmed by scanning electron microscope that the polyurethane stamp fixed on the epoxy resin modified glass replicated the patterns of motherboard with a high fidelity. All these underlay the synthesis of DNA microarray through molecular stamping method.
The second-order nonlinear optical (NLO) properties of three new organic stilbazolium salts (denoted by Dye1, Dye2 and Dye3) were studied by hyper-Rayleigh scattering (HRS) technique. Dye2 and Dye3 are dichromophoric systems of Dye1 with combined bridges of different lengths. Because all the samples are ionic species, the classical technique electric- field-induced second-harmonic generation (EFISHG) can not be used to measure their first hyperpolarizabilities (beta) . Further studies showed that the measured (beta) values were greatly enhanced due to the multi-photon fluorescence (MPF) emissions at 532nm, and more accurate (beta) could be estimated after grossly cutting off the MPF from their spectra. It shows that the stilbazolium salts are good candidates with very large first hyperpolarizabilities (in the range of 10-27esu) for optoelectronic applications. The results revealed the dependence of (beta) on the molecular structures such as number of chromophore, (pi) -conjugation length and molecular conformation in the solution of dimethylformamide. The two level mode was used to predict the intrinsic molecular hyperpolarizabilities of these samples.
Photopolymerized acrylamide gel microarray used to immobilize the molecular beacon for label free DNA hybridization detection is described in this paper. Polyacrylamide gel microarray was prepared by UV photopolymerization of 4% acrylamide in 40% glycerol, 0.002%methylene blue, 0.012% TEMED and 0.1M phosphate buffer (PHequals7) with a Relpel-silane pretreated quartz mask. This kind of three-dimensional gel microarray provides more than 100 times great immobilization capacity. The hybridization and other processes with it resemble a homogeneous liquid phase reaction rather than a heterogeneous liquid-solid interface reaction. The specially designed molecular beacons contain a 15 base loop sequence with 5 base pair stem, a 20 base thymine as spacer, a 5'-end amino group for immobilization, a fluorescein in the middle of the sequence as the fluorophore and a 3'-end DABCYL as the quencher. Between the 5'-end amino group and the stem, the 20 base thymine is used to minimize destability caused by 5'-end immobilization. Confocal microscope was used to investigate the fluorescence intensity of gel immobilized molecular beacon probes. After hybridization we can easily distinguish complementary and noncomplementay targets with gel-immobilized molecular beacon probes. Image analysis showed that the fluorescence intensity ratio of complementary to noncomplementay probes is great than 5. The potential applications of gel-immobilized molecular beacon microarray are mutation detection, pathogenic detection, etc. in a parallel, cost saving and label-free detection way.
A fiber optic fluorescence biosensor for choline is introduced in this paper. Choline is an important neurotransmitter in mammals. Due to the growing needs for on-site clinical monitoring of the choline, much effect has been devoted to develop choline biosensors. Fiber-optic fluorescence biosensors have many advantages, including miniaturization, flexibility, and lack of electrical contact and interference. The choline fiber-optic biosensor we designed implemented a bifurcated fiber to perform fluorescence measurements. The light of the blue LED is coupled into one end of the fiber as excitation and the emission spectrum from sensing film is monitored by fiber-spectrometer (S2000, Ocean Optics) through the other end of the fiber. The sensing end of the fiber is coated with Nafion film dispersed with choline oxidase and oxygen sensitive luminescent Ru(II) complex (Tris(2,2'-bipyridyl)dichlororuthenium(II), hexahydrate). Choline oxidase catalyzes the oxidation of choline to betaine and hydrogen peroxide while consuming oxygen. The fluorescence intensity of oxygen- sensitive Ru(II) are related to the choline concentration. The response of the fiber-optic sensor in choline solution is represented and discussed. The result indicates a low-cost, high-performance, portable choline biosensor.
Polyurethane based on polypropylene glycol (PPG) and Toluene diisocyanate (TDI) using 3,3'-dichloride-4,4'- methylenedianiline (MOCA) as the crosslinker is presented for the first time to fabricate molecular stamps (PU stamps) for the synthesis of DNA microarray with contact procedure. The predictability of the process is achieved by utilizing commercially available starting materials. SEM analysis of the morphology of PU stamps and master showed that PU elastometer could replicate subtly the motherboard's patterns with high fidelity. It was proved from the contact angle measurement that PU stamps surface has good affinity with acetonitrile, which guarantee the well-distribution of DNA monomers on patterned stamps. Laser confocal fluorescence microscopy images of oligonucleotide arrays confirmed polyurethane is an excellent material for molecular stamps.
In this paper, a method of microwave plasma-induced grafting to enhance PDMS surface hydrophilicity was developed and its durable hydrophilicity resulted from an oriented grafting of acrylonitrile (AN) was described. In the investigations, the microwave plasma treatment parameters and post-wet chemical grafting were optimized, and their effects on hydrophilicity were also investigated. Contact angle measurements were used to assess the hydrophilicity of the various modified PDMS surfaces. Moreover, attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopic characterization was used to evaluate PDMS samples variation. It has been found that the cyano groups bonded onto PDMS showed the best hydrophilicity among the modified surfaces, which showed a better affinity to acetonitrile. Therefore the hydrophilic surface was formed on PDMS stamps and the results implied promising applications of DNA microarray.
A polydimethylsiloxane (PDMS) stamp with well-defined features on its surface was fabricated through soft lithography. First, we intended to increase the molecular interaction between the PDMS materials and its supporting substrate through surface modification with self-assembly technique. A silane molecular monolayer has been produced on a glass plate by treatment with 5% (CH3)2SiCl2 in CH3Cl. Secondary, we optimized the thickness of the PDMS stamps between 6x10-4m and 1.0x10-3m, and the feature highness 1.5x10-5m, and thus the stamp shrinkage could be controlled within 0.0417% in linearity or within 0.286% in area, respectively. Third, we modified the surface of the master through chemical plating silver or aluminum to prevent the PDMS from sticking to the master surface. During curing process of the stamp fabrication, PDMS intends to shrink towards the silanized glass plate from the master surface, which helps to peel stamp from the master without damaging its features.
PNA has demonstrated remarkable hybridization properties towards complementary oligonucleotides. In this paper, we tested the PNA's ability of selectively discriminating against single-base mismatches. Efforts were paid to optimizing the fabrication of PNA biosensors and its hybridization to achieve better discriminating capacity. Different factors were studied such as immobilization concentration, target concentration, ion strength and hybridization temperature. An optimized procedure was produced to reliably detect DNAs with single-base mismatches in the sequences. We synthesized two 16 mer PNAs with single-base mismatch to hybridizing with complementary DNA. The complementary PNA showed 8.6 fold stronger signal intensity than mismatch one under our optimized procedure.
We report gel-immobilized molecular beacon for DNA hybridization detection in this paper. The specially designed molecular beacons were covalently immobilized in polyacrylamide gel pads array. After hybridization, the complementary noncomplementary target can be easily distinguished with gel-immobilized molecular beacon probes. The results indicate the potential applications of this new gel-immobilized molecular beacon array in parallel, cost effective and label-free DNA hybridization detection.
There are generally two kinds of DNA microarray used for genomic-scale gene expression profiling of mRNA: cDNA and DNA chip, but both of them suffer from some drawbacks. To meet more requirements, another oligonucleotide microarray with long was produced. This type of microarray had the advantages of low cost, minimal Cross-hybridization, flexible and easy to make, which is most fit for small laboratories with special purposes. In this paper, we devised different probes with different probe lengths, GC contents and gene positions to optimization the probe design. Experiments showed 70 mer probes are suitable for both sufficient sensitivity and reasonable costs. Higher G-C content produces stronger signal intensity thus better sensitivity and probes designed at 3 untranslated region of gene within the range of 300 pb should be best for both sensitivity and specificity.
Genechip engineering includes a set of techniques, such as chip fabrication, target gene preparation and hybridization, pattern detection and processing, bioinformatics related to the probe design and data analysis. In this presentation, I would like to give some present results in on-chip synthesizing the oligonucleotides microarray with molecular stamping or microfluidic molds, and developing software for probe designs.
The potential development of optoelectronic devices based on the NLO response of organic molecules has aroused much recent interest. The influence of the molecular interactions on their NLO properties is important to both basic and application study. The dye rhodamine B can form different protonation and aggregation states by changing the bulk pH, which is revealed by the UV-visible absorption spectra and the fluorescence emissions spectra. Here we also use the hyper-Rayleigh scattering (HRS) technique to probe more detailed information about the protonated forms and aggregates. Because rhodamine dye is an ionic compound, the classical technique electric-field-induced second-harmonic generation can not be used to get the first-order hyperpolarizability (beta) . Our further studies show that rhodamine has strong multi-photon fluorescence emission under the radiation of 1064nm and it overlaps the HRS signal at 532 nm. The concentration dependence of the HRS intensity shows that only in the very low concentration range the HRS signal increases linearly with the increasing concentration. In the higher range, the signal deviates from the line on the below side, which may arise for the linear absorption of the signal at 532 nm, nonlinear absorption of the incident laser beam, the intermolecular effect and distortion of the incident laser at high concentration.
The different binding behavior of some fluorescence dyes to DNA has been primarily investigated by absorption, fluorescence and atomic force microscopy (AFM). The results indicate that the AFM study of the complexes of DNA in their native conformation can be explored to reveal the special nanostructural information of the complexation of the biopolymer supramolecular system, which may directly provide some fresh structural evidence in relation to the binding modes of the ligand-DNA complex.
Large third-order susceptibilities, (chi) (3) or (gamma) , have been observed for II-VI semiconductor nanoparticles. However, there are only few studies on the second-order susceptibilities because it is usually believed that the centrosymmetry or near-centrosymmetry of the particles eliminate the (beta) to zero or very small vale, Here the Hyper-Rayleigh scattering (HRS) technique is used to measure the second-order NLO response of nanoscale CdS Colloids with different surfaces in solution, which are denoted by CdS/Cd2+, CdS/S2-, CdS/SC(NH2)2 CdS/AOT- and CdS/Py. The result shows that the 'per particle' (beta) values for CdS nanoparticles are very large. And the (beta) values are different for CdS nanoparticles with different surfaces. Time dependent experiment show that the HRS signal deceases remarkably as time goes by. Further studies reveal that it has mutli-photon fluorescence (MPF) emission under the radiation of 1064 nm for newly made samples, but for aged stable sample the MPF is rather weak. All these experiments show that the HRS and MPF signals are very sensitive to the changes of the nanoparticle surface or the nanoparticle/solution interface. They also give the evidences proving that the surface termination of the crystalline lattice that creates a condition of non- centrosymmetry is contributing to the large (beta) values for CdS nanoparticles.
The capability of the time-resolved photoacoustic (PA) technique for glucose concentration measurement in the near-infrared range was demonstrated. Both experimental and theoretical studies shown that the concentration dependence of the sound velocity, optical absorption coefficient and thermal property of glucose solution can be simultaneously determined by the time-resolved PA techniques. Good agreement between theory and experiment has been obtained.
Real-time immunological interaction analysis is of great importance for the understanding of relationship between the structure and function of immunomolecules. A fluorimetric evanescent wave optical fiber immunosensor has been developed for the quantitative analysis of ligand-reactor binding kinetics in real-time. The specific immunological reaction between IgG molecules and fluorescein isothiocyanate (FITC)-labeled anti-IgG antibodies was chosen as a model system. The optical fiber immunosensor probe used in this study consisted of a piece of silanized quartz optical fiber core on which IgG molecules were immobilized. The immunological reactions were monitored fluorimetrically in situ to follow the reaction dynamics on the optical fiber surface. A gradually increase in fluorescence signal was found upon binding of fluorescein isothiocyanate (FITC)-labeled anti-IgG antibodies to the surface immobilized IgG molecules. This signal was directly related to the surface concentration of the analyte and immunological reaction kinetic properties. Thus any change in analytical signal in this study would reflect the real process of ligand-receptor binding on the optical fiber probe surface. A flow injection system was introduced into the experiments to shift the immunological reaction from mass transport to reaction rate limited. The quantitative information obtained from the initial reaction phase of a immunological reaction was then studied with a theoretical model using one to one binding, which was a significant of the real-time binding events to evaluate the binding kinetic parameters. The association and dissociation rate constants for IgG/anti-IgG antibody were calculated to be 1.4 X 106 M-1s-1 and 2.1 X 10-4s-1, respectively. The results presented in this paper confirmed that the optical fiber immunosensor described in this study might be used as a tool for rapid and sensitive biospecific interaction analysis.
The potential development of optoelectronic devices based on the nonlinear optical response of organic donor-acceptor molecules has aroused much recent interest. In this paper, two new ionic species in the classes of merocyanine dye and stilbazolium salt are studied by the newly developed Hyper-Rayleigh scattering (HRS) technique. Both compounds are dissolved in methanol under the 1064 nm-laser radiation in the experiments. The results show that the value of the first-order hyperpolarizability (beta) for the merocyanine dye is very large and for the stabilization salt is abnormally too large. Further studies reveal that both the merocyanine dye and the stabilization salt has multi-photon fluorescence (MPF) emission which overlaps the HRS signal at 532 nm under the radiation of 1064 nm but the merocyanine dye's MPF is weaker. If we cut off the MPF from the HRS signal, the (beta) value for the merocyanine dye is in the range of 10-28 esu and the (beta) value for the stilbazolium salt is approximately equals 10-27 esu, which is among the largest solution value of (beta) for organic species.
Optical fiber biosensors offer great promise for rapid and sensitive detection of a variety of chemical and biological analyte. In this paper, we report our progress in developing an optical fiber biosensor for the characterization of solid phase nucleic acid hybridization. The principle of the measurement is based on the combination of photon counting and laser induced fluorescence in the evanescent field on the optical fiber surface. We used long, fused silica fibers that had several centimeters of cladding removed along the distal end for the fabrication of sensor probe. 5'-amino-terminal oligonucleotide probes were covalently immobilized via glutaraldehyde cross- linking to an aminosilane on the exposed fiber core to form a thin layer of oligonucleotide probes. The evanescent excitation of fluorescence was achieved through the evanescent wave penetrating into the oligonucleotide probes layer when an Ar ion laser beam was guided in the optical fiber. In situ hybridization of 5'-fluorescein isothiocyanate (FITC)-labeled complementary oligonucleotides to their immobilized probes was monitored at the proximal end of the sensing fiber through the fluorescent signal which generated in the evanescent wave region of the uncladded portion as they coupled back to the fiber core. Hybridization specificity was tested by addition of fluorescein isothiocyanate (FITC)-labeled noncomplementary oligonucleotides to the immobilized probes. Regeneration of the surface-immobilized probe was possible, allowing reuse without a significant loss of hybridization activity. Dilution experiments showed an apparent lower limit of detection at 1 nM oligonucleotides. This performance was comparable to other previously reported DNA biosensors.
A new optical bio-molecular sensors was developed for bio- molecular sensing based on light-excited surface plasmon resonance. Thickness of bio-molecule films absorbed onto a gold film is measured by the resonance condition of the surface plasmon on the sensing mental surface. The resonance condition is given by thickness of bio-molecule films faced on the mental. The developed sensor can be compact and simple, because of the absence of mechanical moving parts, by using a wedge of laser beam to obtain incident angle scanning and multi-channel angular light intensity detection with a charge coupled device. The sensor using Kretschmann configuration includes three parts: an optical measuring unit, a power source of laser, and a microcomputer used as data collection and handling. The adsorption of ferritin from phosphate buffered saline onto a gold film has been examined using the sensor. Application of the sensor allows elucidation of the surface layer thickness of dry ferritin on gold. Experiment results suggest less than monolayer coverage of ferritin on gold.
An all solid-state electrochromic smart window employing TiO2 particulate film and electrodeposited WO3 film with PEO gel electrolyte with high conductivity has been fabricated. The smart window has been found to be excellent for electrochromism and memory characteristics.
A thiol-terminated phenylazonaphthalene derivative, namely 1-mercapto-6-[1-(4-phenylazonaphthoxy)]hexane 1, was synthesized by diazo coupling of aniline with 1-naphthol, etherification with 1,6-dibromohexane and thiol derivatization, subsequently. By self-assembly technology, the compound was spontaneously absorbed in thin, optically transparent gold film and formed stable self-assembled monolayer (SAM). The self-assembly course was monitored by UV-visible absorption spectra which gave direct evidence for the self-assembly mechanism of self-assembled monolayer, i.e., chemically adsorbed firstly, then came through a long- time orientation. Meanwhile, cyclic voltammogram was employed to study the electrochemical reduction and oxidation of the immobilized phenylazonaphthalene. The single molecular area obtained using the two methods was almost the same: ca. 0.9 nm2. The irreversibility of the electrode process, sluggish reaction and reduction peak splitting all were originated from the well molecular orientation, not the dense packing in the SAM. This implied the process of oxidation and reduction accompanied the molecular conformation change which needed more free space for the movement of the molecular chain during the electrode processes.
A series of phthalocyanine complex Langmuir-Blodgett films were fabricated to align nematic liquid crystals. The antiparallel type, twisted nematic type and hybrid-alignment nematic type cells were realized and their corresponding electro-optic characteristics were investigated adopting the He-Ne laser as the light source.
Surface corrugations with periodic of 2 micrometers and a depth of approximately 150 nm have been fabricated in lithium tantalate (LiTaO3) monocrystal wafers. Morphologies of the corrugations were studied with an atomic force microscope. These corrugations were first produced by a single excimer laser pulse through a diffractive optical element, and the optical quality of the periodic structures is demonstrated by its characteristics as a gratings coupler in a LiTaO3 planar waveguide.
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