Gold Chip Surface Research Articles

High-sensitive surface plasmon resonance sensor for melamine detection in dairy products based on graphene oxide /chitosan nanocomposite

Accurate diagnosis and determination of the appropriate dose of melamine is crucial, especially in children's food, due to the potential for severe side effects such as kidney stones. This research has demonstrated the effectiveness of the graphene oxide-chitosan (GOCS) composite in modifying the gold chip surface as a sensor platform, resulting in a significant 1.17° angular change relative to the bare gold chip for the detection of melamine. The GOCS composite was analyzed using SEM, XRD, and FTIR. The GOCS sensor exhibited high sensitivity with a value of 239.1◦μM−1, a linear range (L.R) of 0.01–200 μM, affinity constant of 1.73 × 104 and an impressive limit of detection (LOD) of 10 nM. These findings highlight the potential of the GOCS sensor for accurately and precisely detecting melamine. Additionally, we compared the obtained results from the sensor with those from the standard method of HPLC, which is referred to as the gold standard in analytical chemistry, by conducting tests using GOCS/Au to identify melamine in commercial samples. The comparison showed that the GOCS sensor offers desirable features for analyzing real samples, making it a promising tool for accurately and efficiently detecting melamine in various samples.

Enhancement of Ligand Immobilization on Gold Surface by Optimizing Monolayer Concentration and Pre‐Concentration Studies for Surface Plasmon Resonance Analysis of Rutin‐Lysozyme Interaction

AbstractSurface plasmon resonance (SPR) is a versatile tool for real time monitoring of molecular interactions, providing biophysical data such as affinity and kinetics. Rutin is found in various plants and fruits and is utilized in several industries. Because of its therapeutic and industrial importance, the binding of rutin to one of the major proteins found in blood and saliva, lysozyme (LZM), was investigated to determine the affinity constants of the rutin‐LZM interaction. Chicken egg white lysozyme (CEWLZM) was selected as a model ligand. 11‐mercaptoundecanoic acid (MUA) was chosen for the self‐assembled monolayer (SAM) design on the gold chip surface. After optimizing MUA concentration and pre‐concentration studies to enhance ligand immobilization, optimum MUA concentration in SAM formation, ideal running and coupling buffers, flow rate and ligand concentration were determined to perform SPR analysis. Various concentrations of rutin (20–300 μM) were injected into the SPR for kinetic analysis. The association (ka), dissociation (kd) rate constants, and equilibrium constant (KD) were calculated from the kinetics of the binding curves. SPR binding results indicated that the KD value of rutin‐CEWLZM binding was determined as 80.07±1.22 μM. This study demonstrates the binding affinity of rutin to CEWLZM, offering potential insights for medical and pharmaceutical sciences.

Label-free and early detection of HER2 breast cancer biomarker based on UiO-66-NH2 modified gold chip (Au/UiO-66-NH2) using surface plasmon resonance technique

Breast cancer is one of the leading causes of cancer death for women worldwide. This cancer occurs when the breast cells grow abnormally and spread uncontrolled. Although there are several treatments, including chemotherapy, radiation, and surgery in a clinical setting to cure cancer, these treatments cannot provide a 100 % success rate in eliminating cancer, mainly due to the late diagnosis of the disease. Thus, early detection is the key to provide better breast cancer treatment and a higher chance for survival. Herein, simple and sensitive biosensor by combining the emerging multifunctional materials of metal-organic frameworks (MOFs) with a label-free surface plasmon resonance (SPR) instrument was developed. Two types of stable Zirconium (Zr)-based MOFs, namely Zr benzene dicarboxylic acid (Zr-BDC or UiO-66) and Zr 2-amino-benzene dicarboxylic acid (Zr-BDC-NH2 or UiO-66-NH2) were synthesized using the solvothermal method. X-ray diffractometer (XRD) and fourier transform infra red (FTIR) confirmed the formation of the prepared UiO-66 and UiO-66-NH2. The electron microscopy and nitrogen adsorption desorption isotherm characterization reveal that the MOFs have a cubic crystal structure with a high surface area of 672.4 m2/g for UiO-66 and 286.1 m2/g for UiO-66-NH2. The MOFs are then functionalized on the SPR gold (Au) chip surface to serve as a matrix of Human Epidermal Growth Factor Receptor 2(HER2) antibody receptors. Interestingly, the functionalized SPR biosensors could detect the HER2 protein target with high sensitivity in the ng/mL range and a remarkable detection limit, which is 0.457 ng/mL for UiO-66-NH2. This LOD value is significantly lower than clinical concentrations of HER2 proteins in human blood (∼15 ng/mL), which indicate that the biosensor can offer the capability of early detection test.

Wide-Range SPRi Sensors Based on Aptamer/sPD-L1/anti–PD-L1 Sandwich and AuNPs Enhancement for Ultrasensitive Detection of sPD-L1

Soluble programmed death-ligand 1 (sPD-L1) levels vary widely among different stages of tumor development, so the direct quantification of sPD-L1 as a cancer biomarker is useful in cancer diagnosis, prognosis and therapeutic assessment. There is an urgent need for an sPD-L1 detection method with a broad detection range and high sensitivity for monitoring cancer progression and evaluating the effectiveness of immunotherapy in real time. Herein, we have reported an enzyme-free, label-free surface plasmon resonance imaging (SPRi) sensor based on an aptamer/sPD-L1/anti–PD-L1 sandwich structure with gold nanoparticle (AuNP) signal enhancement for the ultrasensitive quantitative measurement of sPD-L1 for the first time. The gold chip of the SPRi sensing platform was modified by DNA aptamers, sPD-L1 was specifically adsorbed on the surface of a DNA aptamer-modified gold chip and then coupled with anti–PD-L1. Thus, the detection of sPD-L1 at different concentrations was realized through the formation of an aptamer/sPD-L1/anti–PD-L1 sandwich structure. We also enhanced the SPR signal via AuNPs to further improve sensor sensitivity. The SPRi sensor is able to measure sPD-L1 within a linear range of 50 pM–10 nM and 100 fM–50 pM, and the minimum detection limit is 19 fM. The sensor is designed to be widely applicable, with better accuracy and reliability for more application scenarios. The prepared SPRi sensor shows great potential in improving the sensitivity of detecting sPD-L1. The proposed method demonstrates the excellent performance of the SPRi sensor and provides a possibility for the establishment of effective clinical assay methods in the future.

A Multiple-Array SPRi Biosensor as a Tool for Detection of Gynecological–Oncological Diseases

Diagnostics based on the determination of biomarkers in body fluids will be more successful when several biomarkers are determined. A multiple-array SPRi biosensor for the simultaneous determination of CA125, HE4, CEA, IL-6 and aromatase has been developed. Five individual biosensors were placed on the same chip. Each of them consisted of a suitable antibody covalently immobilized onto a gold chip surface via a cysteamine linker by means of the NHS/EDC protocol. The biosensor for IL-6 works in the pg mL-1 range, that for CA125 in the µg mL-1 range, and the other three within the ng mL-1 range; these are ranges suitable for the determination of biomarkers in real samples. The results obtained with the multiple-array biosensor are very similar to those obtained with a single biosensor. The applicability of the multiple biosensor was demonstrated using several examples of plasma from patients suffering from ovarian cancer and endometrial cyst. The average precision was 3.4% for the determination of CA125, 3.5% for HE4, 5.0% for CEA and IL-6, and 7.6% for aromatase. The simultaneous determination of several biomarkers may be an excellent tool for the screening of the population for earlier detection of diseases.

Lab-on-a-Chip Electrochemical Immunosensor Array Integrated with Microfluidics: Development and Characterisation

Lab-on-a-chip has recently become an alternative for in situ monitoring for its portability and simple integration with an electrochemical immunoassay. Here, we present an electrochemical cell-on-a-chip configured in a three-electrode system to detect benzo(a)pyrene (BaP) in water. 11-Mercaptoundecanoic acid (MUA), a self-assembled monolayer (SAM), was used to modify a gold chip surface to reduce the randomness of antibody binding. A carboxylic acid group was activated with -ethyl-3-(3-dimethylaminopropyl) (EDC) in combination with N-hyrodsuccinimide (NHS) before antibody immobilisation. The mechanism of the electrochemical reactions on a gold surface and SAM formation were investigated by cyclic voltammetry and contact angle measurements. The data revealed a lower contact angle in the modified chip and a scan rate of 50 mV/s. Through the addition of modification layers and thiol end groups to the SAM, our design allowed the chip surface to became more insulated. All were tested by amperometric detection using the developed Q-sense system. This novel technique detected multiple samples, and completed the analysis reasonably quickly. While the integrated system proved successful in a lab setting, the aim of the research is to use this system for in situ analysis, which can be brought into a water environment to carry out tests with existing processes. In this way, any issues that may arise from an environmental setting can be rectified in an efficient manner.

Cancer cell membrane functionalized gold nanoparticles: Natural receptor Tenascin-C as biomimetic probe for sensitive detection of circulating exosomes

Circulating exosomes (crEVs) have attracted increasing interest in non-invasive cancer diagnosis and monitoring of treatment response. In this paper, cancer cell membrane functionalized AuNPs (CCM@AuNPs) containing overexpressed Tenascin-C (TNC) were synthesized as a biomimetic probe for crEVs. crEVs containing fibronectin 1 (FN1) could be recognized through the specific interaction between FN1 and TNC. CCM@AuNPs were immobilized on the gold chip surface to decrease nonspecific interactions and enhance the surface plasmon resonance signal to ensure the sensor’s accuracy and specificity. The ultra-sensitive crEVs detection was achieved through CCM@AuNPs with a low detection limit of 18.1 particles/mL−1 and the linear range of 3 × 104∼3 × 107 particles mL−1. Owing to its simple and direct detection of crEVs, this biomimetic strategy for detecting crEVs offers new possibilities for clinical non-invasive cancer diagnosis.

Surface Plasmon Resonance Monitoring of Mono-Rhamnolipid Interaction with Phospholipid-Based Liposomes.

The interactions of mono-rhamnolipids (mono-RLs) with model membranes were investigated through a biomimetic approach using phospholipid-based liposomes immobilized on a gold substrate and also by the multiparametric surface plasmon resonance (MP-SPR) technique. Biotinylated liposomes were bound onto an SPR gold chip surface coated with a streptavidin layer. The resulting MP-SPR signal proved the efficient binding of the liposomes. The thickness of the liposome layer calculated by modeling the MP-SPR signal was about 80 nm, which matched the average diameter of the liposomes. The mono-RL binding to the film of the phospholipid liposomes was monitored by SPR and the morphological changes of the liposome layer were assessed by modeling the SPR signal. We demonstrated the capacity of the MP-SPR technique to characterize the different steps of the liposome architecture evolution, i.e., from a monolayer of phospholipid liposomes to a single phospholipid bilayer induced by the interaction with mono-RLs. Further washing treatment with Triton X-100 detergent left a monolayer of phospholipid on the surface. As a possible practical application, our method based on a biomimetic membrane coupled to an SPR measurement proved to be a robust and sensitive analytical tool for the detection of mono-RLs with a limit of detection of 2 μg mL-1.

One dimensional magneto-optical nanocomplex from silver nanoclusters and magnetite nanorods containing ordered mesocages for sensitive detection of PD-L1

Programmed death ligand 1 (PD-L1) is a typical immune checkpoint protein, whose up-regulation on the membrane of different tumor cells inhibits the immune response of T cells and leads to the escape of tumor cells. In this work, we designed a facile and highly specific surface plasmon resonance (SPR) biosensor to detect PD-L1 in human plasma based on magnetite nanorods containing ordered mesocages (MNOM) and silver nanoclusters (AgNCs). Magneto-optical nanocomplex MNOM@AgNCs with superior magneto-optical properties and high signal-to-noise ratio were fabricated to improve the detection sensitivity owing to the high specific surface area of MNOM and excellent localized SPR of AgNCs. The PD-L1 Antibody on the surface of gold chip and the PD-L1 aptamer on MNOM@AgNCs could realize dual selective recognition of PD-L1, providing the specificity of the sensor and reducing non-specific binding. The SPR sensor showed a good linear range of PD-L1 from 10 ng/mL to 300 ng/mL with the detection limit of 3.29 ng/mL. The practical performance of this immunosensing platform had been successfully verified by clinical samples which included healthy donors and cancer patients. Based on the analysis, the developed immunosensor provided a new strategy for point-of-care detection of PD-L1 and could be used as clinical companion diagnosis of PD-1/PD-L1 inhibitor therapy.

SPR nanosensor based on molecularly imprinted polymer film with gold nanoparticles for sensitive detection of aflatoxin B1

Aflatoxins which are highly toxic, immunosuppressive and carcinogenic secondary metabolites produced naturally by Aspergillus flavus fungal species have a harm effect on human and animal health. Label free and rapid sensing of aflatoxin B1 (AFB1) has drawn the increased interest of highly sensitive and selective research. A highly sensitive and selective plasmonic sensing method was developed for the detection of AFB1 based on enhance-surface plasmon resonance nanosensor. Firstly, AFB1 and N-methacryloyl-l-phenylalanine were pre-complexed as a template molecule and functional monomer. Molecularly imprinted polymers with gold nanoparticles were coated onto surface plasmon resonance (SPR) gold chip surface. The AFB1 imprinted nanosensor shown a wide linear range, between 0.0001 ng mL−1 and 10.0 ng mL−1, and the limit of detection is 1.04 pg mL−1. Compared to the non-imprinted nanosensor, the imprinting factor was found to be 5.91. Also, detection studies of AFB1 were performed using various food samples. Finally, SPR nanosensors were performed selectivity, reusability and storage stability analysis.

A surface plasmon resonance biosensor in conjunction with a DNA aptamer-antibody bioreceptor pair for heterogeneous nuclear ribonucleoprotein A1 concentrations in colorectal cancer plasma solutions

A new DNA aptamer and antibody pair was incorporated into surface plasmon resonance (SPR) sensing platform to detect heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) in plasma at clinically relevant native concentrations for the diagnosis of colorectal cancer (CRC). SPR detection of hnRNP A1 was realized via formation of the surface sandwich complex of aptamer/hnRNP A1/anti-hnRNP A; the specific adsorption of hnRNP A1 onto a gold chip surface modified with a DNA aptamer followed by the adsorption of anti-hnRNP A1. Changes in the refractive unit (RU) with respect to the hnRNP A1 concentration in buffer solutions were monitored at a fixed anti-hnRNP A1 concentration of 90 nM, resulting in a dynamic range of 0.1–10 nM of hnRNP A1. The surface sandwich SPR biosensor was further applied to the direct analysis of undiluted human normal and pooled CRC patient plasma solutions. Our plasma analysis results were compared to those obtained with a commercial enzyme-linked immunosorbent assay kit.

Detection of CD133-marked cancer stem cells by surface plasmon resonance: Its application in leukemia patients

Here, we reported the development of a label-free and real-time surface plasmon resonance (SPR) based biosensor for cancer stem cells (CSCs) detection using cell surface biomarker; CD133. The fabricated biosensor was used for detection of this marker in some acute myeloid leukemia (AML) patients and the results were compared with those obtained from flow cytometry (FC) method. CD133 antibody was immobilized on the gold chip surface via EDC/NHS coupling method and binding of the candidate cells to the modified gold sensor surface was monitored after isolation of mononuclear cells from bone marrow of the patients. The method was validated in terms of various parameters such as CD133- antibody concentration and cell density. The CD133-marked cells were investigated in seven AML patients. All SPR results were compared with those obtained from FC method. A very good correlation (R2 = 0.96) was obtained between SPR and FC responses related to CD133-marked cells densities. In conclusion, in this study, a label-free and real-time SPR cytometry method was developed to detect CD133 and it was successfully applied to follow this cancer stem cell biomarker in AML patients.

On‐Gold Recombinase Polymerase Primer Elongation for Electrochemical Detection of Bacterial Genome: Mechanism Insights and Influencing Factors

AbstractThe detection of bacterial pathogens may be accomplished through their genome material. With that aim, current methods usually rely on polymerase chain reaction (PCR) amplifications, which are time consuming and require specialist equipment. Here, we optimized an on‐chip isothermal recombinase polymerase amplification (RPA) with chronoamperometric detection, which could be run with simple equipment. A short thiol‐modified oligonucleotide, complementary to a fragment of bipA gene of Salmonella spp., is chemisorbed onto the gold chip surface together with p‐aminothiophenol as a blocking agent. Remarkably, we demonstrate that, in the presence of Salmonella genome, this oligonucleotide, acting as a primer in RPA, is directly elongated on the surface, copying the genome and giving rise to an on‐surface enzyme‐tagged dsDNA. After 30 min of isothermal amplification, the chronoamperometric signal, related to one of the products of the enzyme reaction, increased with the amount of Salmonella genome, which allowed the detection of 105 copies. The results of this study may be of general utility in the design of sensors for detecting other bacteria.

An aptamer-aptamer sandwich assay with nanorod-enhanced surface plasmon resonance for attomolar concentration of norovirus capsid protein

A Gold nanorod (NR) enhanced surface sandwich assay utilizing a novel pair of aptamers for the attomolar concentration of norovirus (NoV) capsid protein was developed in conjunction with surface plasmon resonance (SPR). A total of four different DNA aptamer sequences (aptamer I-IV) known to be specific for the NoV protein were examined using SPR for individual binding strength with the NoV protein and for the formation of surface sandwich with the NoV protein, meaning that the chosen aptamer pair possesses different binding epitope towards the NoV protein. One of the aptamer (aptamer II) sequences with the strongest binding constant was covalently tethered onto a chemically modified thin gold chip surface, while the other aptamer I was used for tethering onto the Au NR surface. The surface sandwich complex was formed via the sequential adsorption of NoV capsid protein and Au NR coated aptamer I onto the aptamer II surface. As low as a 70 aM concentration of the NoV protein in buffer solution could be detected, which is 105 times better than that of using the aptamer-aptamer sandwich platform without any gold NR particles. As a demonstration, the aptamer-NR coated aptamer sandwich assay was applied to analyze NoV capsid protein concentrations spiked in human serum solutions.

A simple surface plasmon resonance biosensor for detection of PML/RAR\u03b1 based on heterogeneous fusion gene-triggered nonlinear hybridization chain reaction

In this work, a simple and enzyme-free surface plasmon resonance (SPR) biosensing strategy has been developed for highly sensitive detection of two major PML/RARα (promyelocytic leukemia, retinoic acid receptor alpha) subtypes based on the heterogeneous fusion gene-triggered nonlinear hybridization chain reaction (HCR). On the gold chip surface, the cascade self-assembly process is triggered after the introduction of PML/RARα. The different fragments of PML/RARα can specifically hybridize with capture probes (Cp) immobilized on the chip and the hybridization DNA1 (H1). Then, the nonlinear HCR is initiated by the complex of Cp-PML/RARα-H1 with the introduction of two hybridization DNA chains (H2 and H3). As a result, a dendritic nanostructure is achieved on the surface of chip, leading to a significant SPR amplification signal owing to its high molecular weight. The developed method shows good specificity and high sensitivity with detection limit of 0.72 pM for “L” subtype and 0.65 pM for “S” subtype. Moreover, this method has been successfully applied for efficient identification of clinical positive and negative PCR samples of the PML/RARα subtype. Thus, this developed biosensing strategy presents a potential platform for analysis of fusion gene and early diagnosis of clinical disease.

In situ formed copper nanoparticles templated by TdT-mediated DNA for enhanced SPR sensor-based DNA assay

For the efficient surface plasmon resonance (SPR)-based DNA assay researching, signal amplification tactics were absolutely necessary. In this work, a sensitive SPR-DNA sensor was developed by employing in situ synthesis of copper nanoparticles (CuNPs) templated by poly-T sequences DNA from terminal deoxynucleotidyl transferase (TdT)-mediated extension, and synergistically with nano-effect deposition as the mass relay. The objective of this strategy was manifold: firstly, tDNA hybridized with the optimal designed probes to active the TdT-mediated DNA extension onto the surface of SPR chip, resulted a long poly-T sequences ssDNA chain in dsDNA terminal onto surface of gold chip and characterized by SPR signal amplitudes. Secondly, copper ion (Cu2+) adsorbed into the skeleton of poly-T sequences DNA, with the aid of ascorbic acid (VC) to achieve the Cu2+ reduction, copper nanostructures (CuNPs) was synchronously generated onto the single nucleotide chain anchoring in dsDNA derivatives and the formation was featured by transmission electron micrographs (TEM) and electrochemistry. Lastly, dsDNA-complexed CuNPs (CuNPs@dsDNA) triggered the final signal amplification via real-time conversion of the additive catechol violet (CV) into oligomer or chelation precipitation by CuNPs-tagged reporters. With the proposed setups, a precise and replicable DNA sensing platform for specific target oligo was obtained with a detection limit down to 3.21 femtomolar, demonstrating a beneficial overlapping exploitation of nanomaterials and biochemical reaction as unique SPR infrastructure. Such triple-amplification strategic setups, the possibility of various methods abutment and biocompatibility weight reactor was amassed and adapted to more biological detection field.

Magneto-plamonic nanoparticles enhanced surface plasmon resonance TB sensor based on recombinant gold binding antibody

The magneto-plamonic nanoparticles (MPNs) have been employed to enhance the signal of surface plasmon resonance (SPR) spectroscopy to gain new insight into MPN and gold film SPR interaction. Three different morphologies MPNs (sphere, short spiky and long spiky) of Fe3O4@Au nanoparticles with good dispersion were synthesized and characterized carefully. A sandwich SPR immunosensor was constructed by immobilizing gold binding anti-CFP-10 (Ab1) onto a gold chip surface via Au-S bond firstly. Gold binding anti-CFP-10 (Ab2) captured on MPN surface was utilized to amplify the SPR signals specifically. Compared with spiky MPNs, the structure of spherical MPN, which concentrates the electric charge density and immobilize more Abs on its surface coverage, could enhance the electronic coupling effect significantly. Attribute to the super paramagnetism of MPNs, a facile solution route was fabricated to capture and separate analyte from the real sample by outside extend magnetic field. Implementation of MPNs results in 30-fold enlargement of the SPR signal at the limit of detection. To this end, an immunoassay is carried out that couples the specificity of antibody-antigen interactions with the high sensitivity based on spherical MPNs signal enhancement SPR.

Signal amplification and dual recognition strategy for small-molecule detection by surface plasmon resonance based on calix[4]arene crown ether-modified gold nanoparticles

A signal-amplification and dual-recognition strategy was designed to construct a signal-enhanced surface plasmon resonance (SPR) platform for the highly sensitive detection of dopamine. This strategy was based on the specific recognition of boronic acid to diol and that of calix[4]arene crown ether-modified gold nanoparticles (CAL[4]-AuNPs) to amine groups. A 3-aminophenyl boronic acid monohydrate probe was immobilized onto a gold chip surface as capture probes via covalent bonds with 11-mercaptoundecanoic acid. CAL[4]-AuNPs were designed as signal probes and characterized by transmission electron microscopy and spectroscopic techniques. Upon the binding of dopamine with boronic acid followed by CAL[4]-AuNPs, the AuNPs were captured on the chip surface to enhance the SPR signal, thereby producing an ultra-low background signal. Signal amplification and dual recognition were used to quantify dopamine concentration from 0.1nM to 1μM, with a detection limit of 1.17pM. This strategy is a new concept for the design of highly selective analytical methods to detect small biomolecules.

MicroRNA-mediated signal amplification coupled with GNP/dendrimers on a mass-sensitive biosensor and its applications in intracellular microRNA quantification

Here, a mass-sensitive microRNA sensing surface is developed by utilizing a probe DNA/gold nanoparticles (GNP)/dendrimer composite coupling with an enzymatic amplification process. The probe DNA/GNP/dendrimer composite is prepared via the covalent coupling between the NH2 groups in PAMAM or DNA and the COOH group on GNP. Target microRNA binds to a stem-loop-structured DNA on maganatic NPs, forming a heteroduplex. By enzyme recycling amplification, a large number of linker sequences are produced on MNPs. Via the combination of probe DNA, the linker DNA on MNPs and a capture DNA on gold chip, the DNA/GNP/dendrimer probe could be assembled on the surface of gold chip inducing a sensitive frequency response. It presents an excellent performance in microRNA-203 quantification with a detection linear range of 1.0×10−11–1.0×10−9M. Both the success in discriminating expressing miroRNA-203 in MCF-7 cell and the well agreement with the commercial qRT-PCR detection method implied its potential application in early cancer diagnosis for future.

CB[7]-mediated signal amplification approach for sensitive surface plasmon resonance spectroscopy

Cucurbit[7]uril (CB[7]) has received increasing attention because of its unique structure and multiple recognition properties. To improve the sensitivity of surface plasmon resonance (SPR) biosensors, we designed a novel strategy in which caspase-3 serves as the model analyte and CB[7]-modified AuNPs (CB[7]-AuNPs) act as the intermedium. The substrate peptides can be cleaved and replaced with a new N-terminal Phe residue in presence of caspase-3. The CB[7]-AuNPs combine with the N-terminal Phe on the gold chip surface through incorporating the side chain within the nonpolar CB[7] cavity and chelating the N-terminal ammonium group with CB[7] carbonyl oxygen. Then CB[7]-AuNPs integrate with short peptide-modified AuNPs containing Phe at the N-terminal of the peptide. SPR signals are significantly improved through the layer-by-layer assembly of AuNPs. The well-designed sensing platform allows the detection of caspase-3 in a linear range from 10fg/mL to 103fg/mL with a detection limit of 2.2 fg/mL. Given its high specificity and desirable sensitivity, this CB[7]-assisted SPR method may be a useful tool for the assay of caspase-3 in the future. This work may also afford a new model to improve the sensitivity and selectivity of SPR biosensors in other protein detection experiments and disease diagnosis.