Shimeng Chen

Surface Plasmon Resonance Biosensor Based on Smart Phone Platforms.

We demonstrate a fiber optic surface plasmon resonance (SPR) biosensor based on smart phone platforms. The light-weight optical components and sensing element are connected by optical fibers on a phone case. This SPR adaptor can be conveniently installed or removed from smart phones. The measurement, control and reference channels are illuminated by the light entering the lead-in fibers from the phone’s LED flash, while the light from the end faces of the lead-out fibers is detected by the phone’s camera. The SPR-sensing element is fabricated by a light-guiding silica capillary that is stripped off its cladding and coated with 50-nm gold film. Utilizing a smart application to extract the light intensity information from the camera images, the light intensities of each channel are recorded every 0.5 s with refractive index (RI) changes. The performance of the smart phone-based SPR platform for accurate and repeatable measurements was evaluated by detecting different concentrations of antibody binding to a functionalized sensing element, and the experiment results were validated through contrast experiments with a commercial SPR instrument. This cost-effective and portable SPR biosensor based on smart phones has many applications, such as medicine, health and environmental monitoring.

Compact multi-channel surface plasmon resonance sensor for real-time multi-analyte biosensing

A compact multi-channel surface plasmon resonance (SPR) biosensor is demonstrated based on a tablet as the measurement platform. The SPR biosensor employs a bundle of fiber-optic SPR sensors as the multiplexed sensing elements that are illuminated by a light-emitting diode (LED) plane light source and detected by a cordless camera. The multi-channel SPR biosensor was based on optical fiber components for precise, label-free and high-throughput detection without the use of complex, specialized or fragile instrumentation that would require optical calibration. The reference and control channels compensated for the fluctuation of the LED light source and the bulk refractive index, increasing the accuracy and reliability of the biosensor. The multi-channel SPR biosensor was applied for multi-analyte biosensing of immunoglobulin G (IgG) and concanavalin A (Con A). The channels functionalized with staphylococcal protein A (SPA) and ribonuclease B (RNase B) only showed relative intensity responses to their corresponding analytes. Moreover, the multi-channel SPR sensors responded to the specific detection of IgG and Con A with an approximately linear relative intensity response to the analyte concentration. Hence, multiple analytes were simultaneously and quantitatively detected with the multi-channel SPR biosensor. This compact, cost-effective multi-channel SPR biosensor is adapted for point-of-care tests, which are important in healthcare and environmental monitoring and for biomolecular interaction analysis.

Temperature-Compensating Fiber-Optic Surface Plasmon Resonance Biosensor

A temperature-compensating fiber-optic surface plasmon resonance (SPR) biosensor based on a Fabry-Perot (FP) interference is described and demonstrated in this letter. The sensing element includes an SPR measuring signal and an FP referencing signal, which appear on gold-coated multimode fiber and capillary, respectively. Because the FP sensing element is sensitive to temperature while insensitive to the refractive index, the referencing channel compensates for the impact of external ambient temperature and enhances the accuracy and reliability of the biosensor. The performance of the temperature-compensating SPR biosensor for accurate measurements is evaluated through the specific binding between Con A and RNase B under interference temperature. In addition, the design and fabrication of the temperature-compensating fiber SPR biosensor are cost effective and simple.

Microcapillary-Based High-Sensitivity and Wavelength-Tunable Optical Temperature Sensor

A high-sensitivity and wavelength-tunable temperature sensor based on a short piece of fused-silica microcapillary (FSC) spliced between two single mode fibers (FSCs) and immerged in ethonal solution is proposed and experimentally investigated. Using the thermo-optic effect of ethanol and high sensitivity to refractive index of the FSC modal interference, the temperature sensitivity of the sensor immerged in ethanol solutions is significantly increased over an FSC sensor in air. Besides, the sensitivity and the feature wavelength of the interferometer can be tuned by adjusting the concentration and refractive index of the filling ethonal solution, which is important for achieving the maximum measurement range.

Micro-capillary-based evanescent field biosensor for sensitive, label-free DNA detection.

We proposed and demonstrated a micro-capillary-based, high-sensitivity evanescent field biosensor for the cost-effective, rapid, and sensitive analysis and detection of specific DNA sequences. By functionalizing the surface of the tubing wall with ssDNA probe sequences, label-free DNA detection is achieved. The wavelength shift response of the surface-functionalized biosensors to DNA hybridization is monitored in real time. Our experiments show that the biosensor can operate at room temperature and is capable of performing label-free hybridization detection, analyte concentration measurement and nucleotide mismatch detection through a single sensing device. The sensor has many advantages, such as a simple manufacturing process, standardized production control, reliable quality, low cost and an economic demodulator. The compact nature and miniature size of the biosensing detection system makes it a good candidate for the rapid and highly sensitive detection of low-concentration analytes in micro-samples for cost-effective, real-time, and on-site analysis in the fields of life science, pharmaceutical chemistry, medical science and criminal investigation.

Investigation of a Capillary-Based Surface Plasmon Resonance Sensor for Biosensing

We report a capillary-based surface plasmon resonance sensor that integrates sample collection, injection, and measurement. The sensor reported here can be fabricated at low cost and possesses a small and robust package. The hollow structure of the capillary not only can be used as a fluid channel but also allows light to travel along a spiral and straight line, which is very helpful for reducing the length of the sensing region. The operation wavelength of the sensor can be tuned with a harmless high-index dielectric layer, which makes it possible to generate a reference signal to correct the effect of changes in the bulk refractive index or temperature. Our experiments show that the sensor can operate at room temperature and is capable of performing label-free detection and real-time monitoring through a single sensing device. Furthermore, similar to needles and insertable probes, the sensor could also potentially be used for minimally invasive medical diagnostics and monitoring. As a biosensor, it will be a practical and specific detection device that can be widely used, such as in biological and life sciences research, and rapid diagnostics.

Localized Surface Plasmon Resonance-Based Micro-Capillary Biosensor

A highly sensitive localized surface plasmon resonance (LSPR)-based micro-capillary biosensor for micro-measurement was described in this letter. The sensing strategy relies on the interrogation of changes in transmission intensity due to the evanescent field absorption of gold nanoparticles immobilized on the inner wall of micro-capillary. The absorbance due to the LSPR was found to be linear to refractive index changes between 1.328 and 1.3617, and the sensitivity was calculated to be 937%RIU-1 . Then, to evaluate the biosensing performance of the LSPR sensor, we demonstrated the capture of transferrin protein by a layer of anti-transferrin solution immobilized on the LSPR sensor at different concentrations. Experimental results suggest that the biosensor we reported presents a good performance in real-time biochemical detection. In addition, with the advantages of low cost, simplicity, high sensitivity, and less amount of samples required, the biosensor we reported can be used for rapid micro measurement in chemical, biological, and medical applications.

Self-Reference Surface Plasmon Resonance Biosensor Based on Multiple-Beam Interference

We demonstrated a novel self-reference surface plasmon resonance (SPR) fiber biosensor, which provided a multiple-beam interference referencing signal for refractive index (RI) compensating. The sensor was fabricated by splicing a capillary to a multimode fiber (MMF) coated with a gold film. The gilded MMF acts as the measuring channel while the capillary is used as referencing channel. The experiment result showed that the measuring signal has an irreversible change corresponding specific binding and referencing signal has reversible change. It indicated that the measuring signal can inspect biomolecular interactions in real time and the referencing signal can be used to compensate for interference effects due to bulk RI changes. The sensor provides a high sensitivity of 1470.291 nm/RIU and a resolution about 3.536 × 10-5 RIU. In addition, this self-reference SPR biosensor we proposed is low cost, simple, and reproduction, which can be applied in biochemical sensing field.

A Low-Cost and Portable Dual-Channel Fiber Optic Surface Plasmon Resonance System

A miniaturization and integration dual-channel fiber optic surface plasmon resonance (SPR) system was proposed and demonstrated in this paper. We used a yellow light-emitting diode (LED, peak wavelength 595 nm) and built-in web camera as a light source and detector, respectively. Except for the detection channel, one of the sensors was used as a reference channel to compensate nonspecific binding and physical absorption. We packaged the LED and surface plasmon resonance (SPR) sensors together, which are flexible enough to be applied to mobile devices as a compact and portable system. Experimental results show that the normalized intensity shift and refractive index (RI) of the sample have a good linear relationship in the RI range from 1.328 to 1.348. We used this sensor to monitor the reversible, specific interaction between lectin concanavalin A (Con A) and glycoprotein ribonuclease B (RNase B), which demonstrate its capabilities of specific identification and biochemical samples concentration detection. This sensor system has potential applications in various fields, such as medical diagnosis, public health, food safety, and environment monitoring.

Simple method for self-referenced and lable-free biosensing by using a capillary sensing element

We demonstrated a simple method for self-reference and label free biosensing based on a capillary sensing element and common optoelectronic devices. The capillary sensing element is illuminated by a light-emitting diode (LED) light source and detected by a webcam. Part of gold film that deposited on the tubing wall is functionalized to carry on the biological information in the excited SPR modes. The end face of the capillary was monitored and separate regions of interest (ROIs) were selected as the measurement channel and the reference channel. In the ROIs, the biological information can be accurately extracted from the image by simple image processing. Moreover, temperature fluctuation, bulk RI fluctuation, light source fluctuation and other factors can be effectively compensated during detection. Our biosensing device has a sensitivity of 1145%/RIU and a resolution better than 5.287 × 10-4 RIU, considering a 0.79% noise level. We apply it for concanavalin A (Con A) biological measurement, which has an approximately linear response to the specific analyte concentration. This simple method provides a new approach for multichannel SPR sensing and reference-compensated calibration of SPR signal for label-free detection.