Micro-hyperspectral technology combines hyperspectral imaging and microscopic imaging technology to obtain the spatial and spectral information of samples simultaneously. Because of its rapidity and nondestructive character, micro-hyperspectral technology has shown immense potential in the biomedical field. In this study, we employed self-assembled micro-hyperspectral imaging (MHSI) system to image A549 cells (human non-small cell lung cancer), introducing gold nanoparticles (AuNPs) as the contrast agents to increase the image signal-to-noise ratio. The result shows that spectrum information distinguishes the optical absorption capabilities of nanoparticles from that of other sources in the cellular environment. Currently, given the experimental restrictions, AuNPs cannot be observed directly, but the location of gold nanoparticles can be identified by the specific spectrum. To analyze hyperspectral three-dimensional cell images and quantitatively analyze the submicroscopic structure of lung cancer cells, the space-spectral feature fusion algorithm is utilized. According to the preliminary results, micro-hyperspectral imaging technology highlights the potential application for subcellular diagnosis, but the image segmentation of cells without contrast agents yields erroneously classified results; the outcomes of cell segmentation for A549 cells' uptake of AuNPs indicate that the cellular structure is distinct. However, there are still misclassifications since AuNPs lack a specialized targeting function. Taking into consideration the current challenges, our next objective is to execute surface modification on AuNPs as probes to target particular sections of living cells to improve the resolution of cell submicroscopic structure imaging. In conclusion, MHSI technology can effectively characterize the submicroscopic structure of cells and show a wide range of potential bioimaging applications.
In this study, we have developed a kind of single-layer graphene-based surface plasmon resonance (SLG-SPR) biosensor with wavelength interrogation to detect C-reactive protein (CRP) by sandwich immunoassay. For the nature of the biosensor itself, with the decrease of the incidence angle (θ), resonance wavelength (λR) increased gradually. The refractive index sensitivity (S) and θ are inversely proportional relationship while S and λR are positively proportional relationship. Then we studied two kinds of sensitivity properties of these two SPR biosensors respectively. The refractive index (RI) sensitivity of the two biosensors is approximately the same and the high sensitivity of SLG-SPR biosensor due to the excellent adsorption properties of graphene. The experiment shows that the changes in resonance wavelength (▵λR) of SLG-SPR biosensor are higher than that of the gold film based SPR (Au-SPR) biosensor when the final sandwich structures were formed. Meanwhile, we have applied the Fresnel reflection equations and Bruggeman approximation formula to calculate the volume fractions of adsorbates in different adlayers, and the dispersion curves of the effective RI of adsorbates with different volume fractions of adlayers and the cAb isothermal adsorption curves that conforms to Langmuir equation were obtained. In conclusion, the SLG-SPR biosensor with a higher detection sensitivity than the conventional Au-SPR biosensor in detecting CRP and it has the advantages of low-cost, stability, highly efficient for the clinical determination of CRP levels.
In this work, we developed a kind of gold-silver alloy film based surface plasmon resonance (AuAg-SPR) biosensors with wavelength interrogation to detect C-reaction protein (CRP) by using gold nanoparticles (AuNPs)-enhanced sandwich immunoassay, and the limit of detection (LOD) of CRP was found to be 5 pg/ml . In conclusion, using the AuNPsenhanced sandwich immunoassay and the SPR chip of AuAg alloy film can detect CRP effectively and reduce the LOD significantly, and this improvement can also be applied for the detection of any biomarkers in low concentration accurately.
In this study, we developed a kind of gold-silver alloy film based SPR (AuAg-SPR) sensors with wavelength interrogation to detect Cancer antigen 125 (CA125) by sandwich immunoassay. The experiment shows that the changes in resonance wavelength (Δλš¯‘…) of AuAg-SPR sensors are higher than that of the gold film based SPR (Au-SPR) sensors when the final sandwich structures were formed. We have applied the Fresnel reflection equations and Bruggeman approximation formula to calculate the volume fractions of adsorbates in different adlayers, and the dispersion curves of the effective refractive index (RI) of adsorbates with different volume fractions of adlayers were obtained. Moreover, we simulated the sensitivity of RI of two kinds of sensors by using the waveguide equations, when the initial resonance wavelength (λš¯‘…) was fixed at 628nm, changing RI from 1.333 to 1.335, the Δλš¯‘… of AuAg-SPR sensor is 2.25-fold compared with that of Au-SPR sensor. Finally, the effect of the size of antigen on the detection result and effective RI were analyzed. In conclusion, the AuAgSPR sensors with a higher sensitivity than the conventional Au-SPR sensors in detecting CA125, owing to the advantages of low-cost, stability, highly efficient for the clinical determination of CA125 levels
In this paper, we report a fiber optic microphone with a large dynamic range. The probe of microphone consists of bi-fiber Fabry-Perot cavity architecture. The wavelength of the working laser is about 1552.05nm. At this wavelength, the interference spectroscopies of these two fiber Fabry-Perot cavities have a quadrature shift. So the outputs of these two fiber Fabry-Perot sensors are orthogonal signal. By using orthogonal signal demodulation method, this microphone can output a signal of acoustic wave. Due to no relationship between output signal and the linear region on interference spectroscopy, the microphones have a large maximum acoustic pressure above 125dB.
An optofluidic anti-resonant reflecting guidance has been proposed and experimental demonstrated for the measurement of liquid refractive index. Two micro-channels were fabricated for the delivery of the liquid sample in the hollow core photonic crystal fiber by using femtosecond laser micromachining, serving as an inlet and outlet. The refractive index can be detected by using the resonant condition of the Fabry-Perot resonator, which is interrogated through the wavelength shift and of the lossy dip in the transmission spectrum. The experimental results show that the sensitivity of up to 1328 nm/RIU is achieved for the refractive index in the range from 1.345 to 1.363 RIU, respectively. The proposed sensor appears to have potential applications of precise measurement in chemistry, medicine, and biology.
A wavelength-interrogated surface plasmon resonance (SPR) sensor overlaid with a Teflon AF2400 film was prepared for rapid and sensitive detection of Benzo[a]pyrene (BaP) in water. The thickness of the Teflon AF 2400 film is much larger than the penetration depth of plasmon field, making the SPR sensor insensitive to refractive index (RI) of bulk solution and particle adsorption on the film surface. The sensor is only responsive to changes in RI of the Teflon film. The Teflon AF 2400 film is highly hydrophobic, enabling to effectively absorb nonpolar BaP molecules in water. Since BaP is a high-RI (n = 1.887) compound, its enrichment in the Teflon film can result in a considerable increase of the film RI. Consequently, the SPR sensor operating in the visible-near infrared reflection (NIR) wavelength range can be used to detect very low concentration of BaP in water. According to the simulation results, the thickness of the Teflon film should exceed 1000 nm to eliminate the SPR sensitivity to RI of bulk solution. The experimental results indicate that the resonance-wavelength shift (ΔλR) of the SPR sensor linearly increases with increasing the BaP concentration from C = 20 nmolĀ·L-1 up to 100 nmolĀ·L-1. ΔλR is about 0.9 nm at C = 20 nmolĀ·L-1, which is very close to the minimum ΔλR detectable with the CCD spectrometer used. The resonance wavelength stabilized 6 seconds after the sample injection, indicating that the diffusion of BaP molecules in the Teflon film is quite quick, which is attributable to the nanoporous structure of the Teflon film. It is anticipated that the sensitivity of SPR sensor to BaP and its detection limit can be further improved by optimization of the thickness of the Teflon film.
Thin films of nanoporous gold (NPG) have both localized and propagating surface plasmon resonance (SPR) effects. The propagating SPR effect of NPG film combined with its huge internal surface area makes it applicable as an evanescent wave sensor with high sensitivity. In this work, NPG films with controlled thicknesses were fabricated on glass substrates by sputtering deposition of AuAg films followed by dealloying in nitric acid. By using of the NPG films as the sensing layer, a broadband wavelength-interrogated SPR sensor was prepared for chemical and biological detection. The propagating SPR absorption band in the visible-near infrared region was clearly observed upon exposure of the NPG film to air, and this band was detected to move to longer wavelengths in response to adsorption of molecules within the NPG film. Simulations based on Fresnel equations combined with Bruggeman approximation were carried out for optimizing the propagating SPR property of NPG film. The sensorā€™s performance was investigated using both bisphenol A (BPA) and lead (II) ions as analytes. According to the experimental results, the detection limits of the sensor are 5 nmolĀ·L-1 for BPA and 1 nmolĀ·L-1 for lead (II) ions. The work demonstrated the outstanding applicability of the NPG film based SPR sensor for sensitive environmental monitoring.
Plasmon waveguides were fabricated by coating sol-gel copolymer templated nanoporous TiO2 films on gold layers sputtered on glass substrates, and they were used to construct wavelength-interrogated plasmon waveguide resonance (PWR) sensors with Kretschmann configuration. The cross-sectional image of the plasmon waveguide obtained with scanning electron microscope indicates that the gold and nanoporous TiO2 films are about 40 nm and 290 nm thick. The resonance wavelength (λR) of the PWR sensor at a given incident angle is determined from either the reflected light intensity spectrum or the absorption spectrum. The porosity of TiO2 film was determined to be ca. 0.42 by a comparison between simulation and experimental results. The PWR sensor operates with transverse electric mode. The in-situ and ex-situ responses of the PWR sensor to glutathione (GSH) adsorption were investigated theoretically and experimentally. The simulation results show that with either in-situ or ex-situ measurement the resonance wavelength linearly increases with increasing GSH concentration and the slope with ex-situ method is 6 times larger than that with in-situ method. The PWR sensorā€™s response to GSH adsorption from the 100 μmol/L solution was measured to be ΔλR = 31 nm with ex-situ detection and ΔλR = 6.1 nm with in-situ detection. Both the experimental and simulation investigations reveal that the ex-situ detection sensitivity is much higher than the in-situ one for the PWR sensor. The work suggests that the ex-situ detection method can offer the PWR sensor a lower detection limit in contrast with the in-situ method.
Layer-by-layer self-assembly ultrathin films continue to be of significant interest among researchers for its broad application in diverse areas. Based on electrostatic attraction between materials with opposite charges, multilayer films of (PSS/Cyt c) 6, (GNPs/Cyt c) 5 and (PDDA/DNA) 6 had been successfully fabricated on the surface of gold chip, respectively. The adsorption process had been followed by in suit spectral surface plasmon resonance (SPR) technique in real time. The experimental results demonstrate that adsorption of materials onto the gold chip can induce a redshift of resonance wavelength and the amount of adsorption can be determined by the change of resonance wavelength. Kinetics studies suggest that adsorption of cytochrome c (Cyt c) or deoxy ribonucleic acid (DNA) obeys Langmuir-isotherm theory, while adsorption of gold nanoparticles (GNPs) obey diffusion-controlled model. These results also indicate that GNPs need more time to reach adsorption equilibrium than Cyt c and DNA, due to a small value of diffusion coefficient.0 increasing with the layer, however, (GNPs/Cyt c) 5 and (PDDA/DNA) 6 show a nonlinearly increase. Moreover, through controlling the number of assembled layer, the thickness of multilayer films can be precise designed.
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