Surface Plasmon Resonance Imaging System Research Articles

Coffee Ring Effect Enhanced Surface Plasmon Resonance Imaging Biosensor via 2-λ Fitting Detection Method.

SPR biosensors have been extensively used for investigating protein-protein interactions. However, in conventional surface plasmon resonance (SPR) biosensors, detection is limited by the Brownian-motion-governed diffusion process of sample molecules in the sensor chip, which makes it challenging to detect biomolecule interactions at ultra-low concentrations. Here, we propose a highly sensitive SPR imaging biosensor which exploits the coffee ring effect (CRE) for in situ enrichment of molecules on the sensing surface. In addition, we designed a wavelength modulation system utilizing two LEDs to reduce the system cost and enhance the detection speed. Furthermore, a detection limit of 213 fM is achieved, which amounts to an approximately 365 times improvement compared to traditional SPR biosensors. With further development, we believe that this SPR imaging system with high sensitivity, less sample consumption, and faster detection speed can be readily applied to ultra-low-concentration molecular detection and interaction analysis.

Surface Plasmon Resonance Biosensors: A Review of Molecular Imaging with High Spatial Resolution.

Surface plasmon resonance (SPR) is a powerful tool for determining molecular interactions quantitatively. SPR imaging (SPRi) further improves the throughput of SPR technology and provides the spatially resolved capability for observing the molecular interaction dynamics in detail. SPRi is becoming more and more popular in biological and chemical sensing and imaging. However, SPRi suffers from low spatial resolution due to the imperfect optical components and delocalized features of propagating surface plasmonic waves along the surface. Diverse kinds of approaches have been developed to improve the spatial resolution of SPRi, which have enormously impelled the development of the methodology and further extended its possible applications. In this minireview, we introduce the mechanisms for building a high-spatial-resolution SPRi system and present its experimental schemes from prism-coupled SPRi and SPR microscopy (SPRM) to surface plasmonic scattering microscopy (SPSM); summarize its exciting applications, including molecular interaction analysis, molecular imaging and profiling, tracking of single entities, and analysis of single cells; and discuss its challenges in recent decade as well as the promising future.

Anti-allergic drug screening in single living mast cells by means of a novel surface plasmon resonance imaging system

In recent years, phenotypic drug screening has achieved renewed prominence, because it can develop drugs for some rare diseases with unknown etiology and without effective therapeutic drugs. Combined with biochip microarray technology, surface plasmon resonance imaging (SPRi) technology based on changes in reflected light intensity has been widely used to analyze interactions between biomolecules, especially for in vitro drug screening. However, changes in reflected light intensity are merely derivative of changes in surface plasmon resonance angles, so current SPRi technology suffers from low accuracy, poor sensitivity, and narrow linear range. In this study, we built an improved SPR microscopic imaging system capable of directly detecting SPR resonance angle (SPR-dip) shifts, with a sensitivity of 8.14 × 10−6 RIU, and a stability less than ± 2 m°. By optimizing the optical path system, the linear correlation coefficient of the system within the scanning range of 3800 m° is 0.9975. Based on this imaging system, we established a reliable screening system for single living mast cell allergy drugs. By developing small molecule microarray chips, we achieved high-throughput screening of 2400 sample points at one time. Our SPR microscopic imaging system integrates the comparative advantages of existing angle-scanning SPRi systems and opens the possibility of new applications in phenotypic drug screening.

Cellular analyses for label-free and rapid HER2-positive cancer diagnosis based on SPRi-modified with nanobody

Overexpression of human epidermal growth factor receptor-2 (HER2) is an important prognostic indicator for clinical diagnosis, as it results in more invasive cancer cells and lower survival rates. In this study, we developed a novel immunosensor based on surface plasmon resonance imaging (SPRi) modified with nanobody 2 (NB2) to detect the HER2 expression of various cancer cells. Firstly, we established a multi-channel intensity interrogation SPRi system with a refractive index resolution (RIR) of 1 × 10−6 RIU. Then, we fabricated the immunosensor by immobilizing NB2 nanobody on the sensor chip through affinity-based orientation. The NB2 exhibited high specificity for HER2 extracellular domain, enabling specific capture of HER2-positive cancer cells. The results revealed that the sensor could detect the HER2 expression of various living cancer cells by directly injecting cell suspensions. Compared with flow cytometry, SPRi system could obtain similar HER2 expression results with better performance, such as faster response time (<30 min), smaller sample volume (<200 μL), and lower cell concentration (105 cells/mL). The most important of all is that researchers do not need to take complex fluorescent labeling pretreatment of cell samples. Therefore, such immunosensors may offer great potential for rapid personalized treatment planning and enhanced patient outcomes.

Surfactant-like Peptide Self-Assembled into Hybrid Nanostructures for Electronic Nose Applications.

An electronic nose (e-nose) utilizes a multisensor array, which relies on the vector contrast of combinatorial responses, to effectively discriminate between volatile organic compounds (VOCs). In recent years, hierarchical structures made of nonbiological materials have been used to achieve the required sensor diversity. With the advent of self-assembling peptides, the ability to tune nanostructuration, surprisingly, has not been exploited for sensor array diversification. In this work, a designer surfactant-like peptide sequence, CG7-NH2, is used to fabricate morphologically and physicochemically heterogeneous "biohybrid" surfaces on Au-covered chips. These multistructural sensing surfaces, containing immobilized hierarchical nanostructures surrounded by self-assembled monolayers, are used for the detection and discrimination of VOCs. Through a simple and judicious design process, involving changes in pH and water content of peptide solutions, a five-element biohybrid sensor array coupled with a gas-phase surface plasmon resonance imaging system is shown to achieve sufficient discriminatory capabilities for four VOCs. Moreover, the limit of detection of the multiarray system is bench-marked at <1 and 6 ppbv for hexanoic acid and phenol (esophago-gastric biomarkers), respectively. Finally, the humidity effects are characterized, identifying the dissociation rate constant as a robust descriptor for classification, further exemplifying their efficacy as biomaterials in the field of artificial olfaction.

Unraveling the binding microprocess of individual Streptococcus mutans cells via sucrose-dependent adhesion based on surface plasmon resonance imaging

ABSTRACT The initial microprocess of a major cariogenic bacterium Streptococcus mutans forming biofilm at a single-cell level via sucrose-dependent adhesion has not been observed because the cells’ high moisture content caused measurement challenges. To develop a high-sensitivity biosensor chip and a real-time, label-free method to observe bioactive molecule interactions with single cells from oral biofilms. We made the chips of immobilized bacteria by micronano-processing. A surface plasmon resonance imaging (SPRI) system was used to detect and record the association and dissociation microprocess of S. mutans with sucrose/dextran solutions of various concentrations, and the calculus model was adopted to treat the data. At the location of S. mutans, a unique ‘comet-tail’ SPRI signal was observed. The binding patterns of S. mutans differed between individual cells exposed to the same solution as well as between sucrose and dextran. The different cells exhibited different affinities with dissociation constants for sucrose being 5.697 × 10−3 to 3.689 M and for dextran 1.235 × 10−3 to 1.282 M, indicating cell-to-cell heterogeneity. Our SPRI detection method is effective in investigating microbial binding, initial biofilm formation, and oral microecology. It offers new possibilities for studying oral microorganism characteristics and development of oral diseases.

Smartphone surface plasmon resonance imaging for the simultaneous and sensitive detection of acute kidney injury biomarkers with noninvasive urinalysis.

A surface plasmon resonance imaging (SPRi) platform integrated with a smartphone was constructed for the simultaneous and sensitive detection of acute kidney injury (AKI) biomarkers. The smartphone SPRi platform was developed without the requirement of additional light and power sources. The LED flash of the smartphone was used as the light source for the excitation of surface plasmon resonance of a gold sensor chip based on the Kretschmann configuration, while the reflected light was collected by the camera of the smartphone. This smartphone SPRi system was conveniently fabricated by 3D printing and showed a sensitivity of 1.78 × 10-5 refractive index unit (RIU). In addition, based on a magnetic nanoparticle-enhanced sandwich immunoassay, the smartphone SPRi system with a gold array chip was employed for the detection of multiple AKI biomarkers, with a low limit of detection (LOD) of 0.19 ng ml-1, 0.51 ng ml-1 and 0.7 ng ml-1 for the simultaneous detection of neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18) and retinol-binding protein (RBP) in urine, respectively. The biosensors demonstrated high specificity and sensitivity for the simultaneous detection of multiple AKI biomarkers in PBST and urine. The smartphone SPRi system provided a portable and cost-effective platform for point-of-care diagnosis, in-field healthcare and environmental monitoring.

Development of a Surface Plasmon Resonance and Fluorescence Imaging System for Biochemical Sensing.

Surface plasmon resonance (SPR) biosensors are an extremely sensitive optical technique used to detect the changes in refractive index occurring at the sensor interface. Fluorescence involves the emission of light by a substance that has absorbed light or other electromagnetic radiation, and the parameters of the absorbed and emitted radiation are used to identify the presence and the amount of specific molecules in a specimen. SPR biosensors and fluorescence analysis are both effective methods for real-time detection. The combination of these technologies would improve the quantitative detection sensitivity of fluorescence analysis and the specificity of SPR detection. We designed and developed an SPR and fluorescence synchronous detection system. The SPR module was based on two kinds of modulation methods, and the fluorescence module was capable of switching between four wavelengths. The fluorescence microspheres and A549 cells of different concentration were both detected by the SPR and fluorescence method synchronously in real time. The fluorescent signal and the optical signal of the SPR were shown to correlate. The correlation coefficient for fluorescent microspheres detection reached up to 0.9866. The system could be used in cell analysis and molecule diagnosis in the future.

Performance improvement of plasmonic sensors using a combination of AC electrokinetic effects for (bio)target capture.

Analytes concentration techniques are being developed with the appealing expectation to boost the performance of biosensors. One promising method lies in the use of electrokinetic forces. We present hereafter a new design for a microstructured plasmonic sensor which is obtained by conventional microfabrication techniques, and which can easily be adapted on a classical surface plasmon resonance imaging (SPRI) system without further significant modification. Dielectrophoretic trapping and electro-osmotic displacement of the targets in the scanned fluid are performed through interdigitated 200μm wide gold electrodes that also act as the SPR-sensing substrate. We demonstrate the efficiency of our device's collection capabilities for objects of different sizes (200nm and 1μm PS beads, as well as 5-10μm yeast cells). SPRI is relevant for the spatial analysis of the mass accumulation at the electrode surface. We demonstrate that our device overcomes the diffusion limit encountered in classical SPR sensors thanks to rapid collection capabilities (<1 min) and we show a consequent improvement of the detection limit, by a factor >300. This study of an original device combining SPRI and electrokinetic forces paves the way to the development of fully integrated active plasmonic sensors with direct applications in life sciences, electrochemistry, environmental monitoring and agri-food industry.

Aluminum Nanostructures for Surface-Plasmon-Resonance-Based Sensing Applications

Surface plasmon resonance imaging (SPRi) is capable of real-time, label-free, and high-throughput detection for many sensing applications. The conventional prism-based SPRi system is operated with ...

Surface plasmon resonance imaging of excitable cells

Surface plasmons (SPs) are surface charge density oscillations occuring at a metal/dieletric interface and are highly sensitive to refractive index variations adjacent to the surface. This sensitivity has been exploited successfully for chemical and biological assays. In these systems, a surface plasmon resonance (SPR)-based sensor detects temporal variations in the refractive index at a point. SPR has also been used in imaging systems where the spatial variations of refractive index in the sample provide the contrast mechanism. SPR imaging systems using high numerical aperture (NA) objective lenses have been designed to image adherent live cells with high magnification and near-diffraction limited spatial resolution. Addressing research questions in cell physiology and pharmacology often requires the development of a multimodal microscope where complementary information can be obtained.In this paper, we present the development of a multimodal microscope that combines SPR imaging with a number of additional imaging modalities including bright-field, epifluorescence, total internal reflection microscopy and SPR fluorescence microscopy. We used a high NA objective lens for SPR and TIR microscopy and the platform has been used to image live cell cultures demonstrating both fluorescent and label-free techniques. Both the SPR and TIR imaging systems feature a wide field of view (~300 µm) that allows measurements from multiple cells whilst maintaining a resolution sufficient to image fine cellular processes. The capability of the platform to perform label-free functional imaging of living cells was demonstrated by imaging the spatial variations in contractions from stem cell-derived cardiomyocytes. This technique shows promise for non-invasive imaging of cultured cells over very long periods of time during development.

An automatic multi-thread image segmentation embedded system for surface plasmon resonance sensor

In order to reduce the uncertainties associated with manual selection of regions of interest (ROIs) commonly used in Surface Plasmon Resonance (SPR) imaging system, we proposed and implemented an automatic image segmentation method in an embedded system to facilitate the potential real-time applications. Intuitive marker-controlled watershed algorithm is developed to segment ROIs (reaction, blank, and background regions) from images acquired from an experimental image SPR system. The marker assignment algorithms and pre-processing algorithms are executed in parallel by multi-threading programming on the multi-core embedded system to both real-time and good quality of segmentation. This method exhibited a good robustness in a series of ROIs segmentation test. Furthermore, the intensity response from triplicate detection of glucose standard solutions indicated a good reproducibility of data. The linear range was from 2.5 mg/mL to 20.4 mg/mL, with a correlation coefficient (R2) of 0.999 and sensitivity of 2.69 a.u./mg/mL. In conclusion, the proposed automatic image segmentation method effectively makes the measurement more precise and simplified.

Real-time SPR imaging based on a large area beam from a wavelength-swept laser.

We demonstrate a real-time surface plasmon resonance imaging (SPRi) system based on a wavelength-swept laser. Compared to conventional spectral-modulation SPRi using white light source and spectral filtering, the proposed system has a higher scan rate to detect rapid changes in refractive index and a higher output power for large-area illumination. This SPRi system achieves scan rates faster than 12Hz, simultaneously obtaining SPR dip positions over full illumination fields of 12×12 mm. Using the wavelength-swept laser, two-dimensional biomolecular array imaging can be acquired with a high dynamic detection range (7.67×10-3 refractive index unit (RIU)) as well as high sensitivity (6501nm/RIU) and resolution (1.89×10-6 RIU).

Spatial resolution versus contrast trade-off enhancement in high-resolution surface plasmon resonance imaging (SPRI) by metal surface nanostructure design.

Surface plasmon resonance imaging (SPRI) is an optical near-field method used for mapping the spatial distribution of chemical/physical perturbations above a metal surface without exogenous labeling. Currently, the majority of SPRI systems are used in microarray biosensing, requiring only modest spatial resolution. There is increasing interest in applying SPRI for label-free near-field imaging of biological cells to study cell/surface interactions. However, the required resolution (sub-µm) greatly exceeds what current systems can deliver. Indeed, the attenuation length of surface plasmon polaritons (SPP) severely limits resolution along one axis, typically to tens of µm. Strategies to date for improving spatial resolution result in a commensurate deterioration in other imaging parameters. Unlike the smooth metal surfaces used in SPRI that support purely propagating surface modes, nanostructured metal surfaces support "hybrid" SPP modes that share attributes from both propagating and localized modes. We show that these hybrid modes are especially well-suited to high-resolution imaging and demonstrate how the nanostructure geometry can be designed to achieve sub-µm resolution while mitigating the imaging parameter trade-off according to an application-specific optimum.

Surface Plasmon Resonance is an Analytically Sensitive Method for Antigen Profiling of Extracellular Vesicles.

Identification, enumeration, and characterization of extracellular vesicles (EVs) are hampered by the small size of EVs, a low refractive index, and low numbers of antigens on their surface. We investigated the potential of a 48-multiplex surface plasmon resonance imaging (SPRi) system to perform EV phenotyping. Antigen surface density of 11 antigens was measured on the human breast cancer cell lines HS578T, MCF7, and SKBR3 and their EVs by use of both SPRi and the widely used flow cytometry (FCM). For cells, the SPRi and FCM signals for antigen exposure correlated (RHS578T cells2 = 0.66, RMCF7 cells2 = 0.78, RSKBR3 cells2 = 0.60). With regard to EVs, SPRi detected 31 out of 33 tested antibody-EV pairs, whereas our flow cytometer detected 5 antibody-EV pairs because of high blank and isotype control signals. For HS578T-derived EVs, the SPRi and FCM signals correlated (R2HS578T EVs = 0.98). However, on MCF7- and SKBR3-derived EVs, insufficient antigens were detected by our flow cytometer. To confirm that the SPRi responses correlated with mean antigen density on EVs, the SPRi responses of EVs were correlated with antigen density on parental cells as measured by FCM (RHS578T2 = 0.77, RMCF72 = 0.49, RSKBR32 = 0.52). SPRi responses correlate with mean antigen density. Moreover, SPRi detects lower antigen-exposure levels than FCM because SPRi measures an ensemble of EVs binding to the sensor surface, whereas FCM detects antigens of single EV.

Common-path digital holographic microscopy for near-field phase imaging based on surface plasmon resonance.

We develop a common-path digital holographic microscopy based on prism-coupling surface plasmon resonance (SPR) for near-field phase imaging. A single beam splitter with specific configuration is introduced in an SPR imaging system to realize off-axis holographic recording. By measuring the phase shift difference of the reflected light at SPR exploiting the proposed holographic microscopy with high temporal stability, near-field characteristic measurement can be realized. With its simplicity, vibration isolation, and inherent capability of phase curvature compensation, the recommended system shows advanced performance in monitoring tiny refractive index variations and imaging biological tissues.

Simultaneous assay of platelet adhesion at multiple shear rates within a single microfluidic channel

Cardiovascular diseases are currently the major causes of mortality in the world, especially in developed nations. As a predominant one, thrombosis is the platelet aggregation induced by a high shear rate. Platelet aggregation assay can clarify the occurrence mechanism of thrombosis, as well as be used as an important tool in the clinical diagnosis, personalized treatment, and screening of anticoagulants. Thus, relevant studies attracted considerable attention. As an important step in platelet aggregation, platelet adhesion and its detection also attract intensive concern. Thus, some analytical methods have been developed for platelet adhesion assay, and the impact of shear rate is one of the focuses. Compared with other devices, biosensors can give a more accurate result within a shorter time. Furthermore, some biosensors can achieve real-time analysis. However, only one or several shear rates can be tested at the same time, which may decrease the analytical efficiency. Meanwhile, in most cases, only the average platelet adhesion effect within a reactor is detected, and the impact of the distribution of shear rates is improperly neglected. In this study, a microfluidic device with a single channel is designed and fabricated for platelet adhesion assay. When the platelet-rich plasma flows through the collagen-modified sensing surface of the channel bottom, the interaction between platelets and collagen molecules on the entire surface can be simultaneously monitored by using a surface plasmon resonance imaging (SPRi) system. A gradient of the shear rate (0–546 s-1) could be formed within the channel by choosing a suitable depth-to-width ratio (1:5), so platelet adhesion at multiple shear rates could be monitored simultaneously. This method enables the measurement of the adhesion process of unlabeled platelets on the entire sensing surface, in vitro, at multiple shear rates. Such a system can obtain more accurate platelet adhesion result at a given shear rate than traditional methods. Furthermore, in an individual operation, platelet adhesion can be repeatedly tested at multiple points with an equal shear rate, so a much higher analytical efficiency can also be achieved.

Two-Dimensional Surface Plasmon Resonance Imaging System for Cellular Analysis.

Optical biosensors based on surface plasmon resonance (SPR) phenomenon have received a great deal of attention in cellular analysis applications. Sensitive and high-resolution SPR imaging (SPRi) platforms are very useful for real-time monitoring and measurement of individual cell responses to various exogenous substances. In cellular analysis, mainstream SPR-based sensors have potential for investigations of cell responses under ambient conditions. Evaluations that account only for the average response of cell monolayers mask the understanding of precise cell-molecular interactions or intracellular reactions at the level of individual cells. SPR/SPRi technology has attracted a great deal of attention for detecting the response of cell monolayers to various substances cultivated on the gold sensor chip. To unleash the full strength of SPRi technology in complex cell bio-systems, the applied SPR imaging system needs to be sufficiently effective to allow evaluation of a compound's potency, specificity, selectivity, toxicity, and effectiveness at the level of the individual cell. In our studies, we explore the utility of high-resolution 2D-SPR imaging for real-time monitoring of intracellular translocation of protein kinase C (PKC), and detection of neuronal differentiation in live cells at the level of individual cells. The PC12 cell line, which is one of the most commonly used neuronal precursor cell lines for research on neuronal differentiation, was chosen as a nerve cell model. Two dimensional SPR (2D-SPR) signals/images are successfully generated. We have found that cells treated with the differentiation factor nerve growth factor (NGF) showed a remarkable enhancement of SPR response to stimulation by muscarine, a nonselective agonist of the muscarinic acetylcholine receptor.

The Potential Prognostic Markers for Myelodysplatic Syndromes Studied By Surface Plasmon Resonance Imaging and Mass Spectrometry

IntroductionMyelodysplastic syndromes are clonal hematopoetic stem cell disorders characterized by refractory cytopenias with displasia as a result of ineffective hematopoiesis. Approximately 30 percent of MDS cases progress to acute myeloid leukemia. Excess blasts are the strongest predictors for poor outcome and are associated with disease progression. Because of its heterogeneity and lack of molecular and protein markers that effectively monitor disease progression, clinical management of MDS patients is challenging.The concentrations of several proteins were found elevated during MDS disease. Their interaction with receptors/ligands is a part of signaling pathways that may play a crucial role in pathogenesis of the disease. Serum levels of vascular cell adhesion protein 1 (VCAM1) and intercellular adhesion molecule 1 (ICAM1) were found higher in MDS patients in comparison with control group and were related to MDS severity. Alpha-2-HS-glycoprotein (FETUA) was analyzed in plasma of MDS patients. Leucine-rich alpha-2-glycoprotein (LRG) was found increased in RAEB-I and RAEB-II patients by proteomic studies.In this work we developed a protein chip for study of molecular interactions in plasma of MDS patients using surface plasmon resonance (SPR) imaging. Interacting proteins were analyzed and identified using LC-MS/MS.MethodsPatients with diagnosis of refractory anemia and refractory anemia with ringed sideroblasts (RA/RARS, n=13), refractory cytopenia with multilineage dysplasia (RCMD, n=16), and refractory anemia with excess blasts (RAEB, n=15) as a subgroup of MDS, and MDS patients who progress to acute myeloid leukemia (AML, n=8) were chosen for this study.The high-resolution SPR imaging (SPRi) system with polarization contrast and internal referencing combined with dispersionless microfluidics was used to study protein interactions. Passive mixing structures were employed to further improve the sensing performance of this SPRi biosensor.The respective biomarkers (ICAM1, VCAM1, FETUA and LRG) were covalently attached to the functionalized sensor surface and interaction with their counterparts in MDS plasma samples were monitored.Interacting proteins were removed from the chip surface by diluted NaOH, treated by trypsin, analyzed by nanoLC-MS/MS (TripleTOF 5600) and identified using ProteinPilot database.Results and ConclusionSignificant differences were observed between analyzed MDS subtypes for VCAM1, FETUA, and LRG (ANOVA: P = 0,00755, P = 0,0306 and P < 0.001 respectively). Using post hoc Tukey contrasts tests we ascertained that sensor responses were significantly higher in group RCMD and AML with respect to the healthy donors for immobilized VCAM1 and in group RA/RARS, RCMD, RAEB and AML with respect to the healthy donors for LRG. Moreover sensor responses were significantly higher in group AML with respect to the RA, RCMD or RAEB for immobilized LRG. Based on our results LRG seems to be a suitable marker of MDS progression.The identified proteins presented in MDS plasma samples unlike in healthy donor plasma are clusterin, protein S100-A8, serum amyloid A-1 protein, annexin A2, and zinc-alpha-2-glycoprotein among others. S100-A8 and clusterin have been connected with MDS or AML previously; it could be tested as a new protein marker of MDS by SPRi. The results show that SPR biosensors combined with nanoLC-MS/MS are a promising tool for improvement of the diagnosis in complex heterogeneous malignancies. DisclosuresNo relevant conflicts of interest to declare.

Biosensing of BCR/ABL fusion gene using an intensity-interrogation surface plasmon resonance imaging system

In this work, a custom-made intensity-interrogation surface plasmon resonance imaging (SPRi) system has been developed to directly detect a specific sequence of BCR/ABL fusion gene in chronic myelogenous leukemia (CML). The variation in the reflected light intensity detected from the sensor chip composed of gold islands array is proportional to the change of refractive index due to the selective hybridization of surface-bound DNA probes with target ssDNA. SPRi measurements were performed with different concentrations of synthetic target DNA sequence. The calibration curve of synthetic target sequence shows a good relationship between the concentration of synthetic target and the change of reflected light intensity. The detection limit of this SPRi measurement could approach 10.29nM. By comparing SPRi images, the target ssDNA and non-complementary DNA sequence are able to be distinguished. This SPRi system has been applied for assay of BCR/ABL fusion gene extracted from real samples. This nucleic acid-based SPRi biosensor therefore offers an alternative high-effective, high-throughput label-free tool for DNA detection in biomedical research and molecular diagnosis.