Applied Science and Convergence Technology

Review for Device Compositions of Localized Surface Plasmon Resonance Sensors

Seong Gi Lim, Seongjae Jo, Ji Hyeon Lee, and Oh Seok Kwon

Additional article information

Abstract

The localized surface plasmon resonance (LSPR) sensor is applied in various fields and has individual detection strategies depending on the target material. The device composition of the LSPR sensor has its own characteristics depending on the detection strategy. Although many studies have been reported on the sensing principle and targets of LSPR, the components of the sensing device have not been well described. In this review, we introduce various device compositions of LSPR sensors. The LSPR sensor consists of three major parts: probe, light source, and spectrometer. First, we report various research results on chip-based LSPR sensors that are typically used. In addition, we provide studies of fiber-based LSPR sensors. Finally, this review concludes with a discussion of portable and smartphone-based LSPR sensors in place of fixed LSPR devices.

Keywords: Localized surface plasmon resonance, Sensor, Device, Chip, Optical fiber

1. Introduction

The localized surface plasmon resonance (LSPR)-based sensors are used in various fields, such as medicine, food, the environment, industrial processes, and the military [1, 2]. LSPR sensors start with the theory of a plasmon. Plasmon refers to state-free electrons that vibrate collectively on metal, and LSPR appears when a plasmon occurs locally (e.g., nanoparticle, nanostructure) [3,4]. The well-known characteristic of LSPR is that metal nanoparticles absorb light of a specific wavelength. Gold has a unique yellow color, but gold nanoparticles 20 nm in size strongly absorb the 520 nm wavelength to show red light [5,6]. In this moment, the change in dielectric constant (i.e., change in refractive index) occurring near the metal nanostructure shifts the absorbed wavelength; then, this shift of wavelength can be measured and applied to the LSPR sensor [7, 8].

Three major parts are required to compose the LSPR sensor (Fig. 1) [7]. The first part is a probe fabricated with metal nanoparticles or nanostructures that cause plasmons [912]. LSPR sensor probes can be manufactured by various methods, such as immobilizing metal nanoparticles on substrates [13,14] and generating nanostructures using sputtering, evaporation, and deposition [1517]. Another part is a light source for measuring the fabricated probe. To observe the wavelength bands of the probe, a light source with a wide wavelength band is commonly used [18,19]. The generally used tungsten halogen lamp excites white light and has a wide wavelength band of 340–850 nm [20]. Light emitting diodes are used when the desired wavelength band is limited [21, 22]. The final part is a spectrometer that observes the spectra of the probe with respect to the light source [23, 24]. The spectrometer consists of a component that splits light (e.g., prism and grating) and a photodetector that counts photons [25].

Figure F1
Composition of the LSPR device. (a) Schematic of the experimental setup used for LSPR sensing. Reproduced with permission from [7], Copyrights 2019, Elsevier. (b) LSPR setup for material detection. The ...

The LSPR sensor develops in various ways depending on how the abovementioned three parts are configured. A typical LSPR sensor probe is a form of chip. A chip-based LSPR sensor is manufactured by fixing metal nanoparticles on a substrate (e.g., Si wafer, glass, and film) or creating metal nanostructures [2628]. Another type of LSPR sensor probe applies fibers. A fiber-based LSPR sensor uses an optical fiber to fabricate a plasmonic probe. In addition, the development of a portable LSPR sensor is being studied in place of the immovable LSPR experimental setup [2931]. Studies on miniaturization of the device using a light source as an LED and a spectrometer as a photodetector have been reported [22, 32]. Moreover, with the development of smartphones in recent years, studies using smartphone cameras to apply LSPR are in progress [3335]. The early portable LSPR sensor had a large size and low sensitivity, but recently reported sensors have become much smaller and have significantly improved sensitivity. The advancement of these local surface plasmon resonance-based sensors is thought to open a new horizon for future technologies.

2. Chip-based LSPR sensor

The chip-based LSPR sensor is a commonly used method. The plasmon LSPR probe is generated by immobilizing metal nanoparticles or nanostructures on substrates [36, 37]. The manufactured chip strongly absorbs a specific wavelength by the LSPR effect, and then the material is measured by observing the absorption wavelength that changes depending on the concentration of the sensing target [3840].

Oh et al. [41] developed an LSPR sensor chip using the cuvette system to sensitively detect biomarkers such as C-reactive protein. The manufactured LSPR sensor chip was able to detect biomarkers in the range of 0.01–10 µg/mL [Fig. 2(a)]. Funari et al. [23] showed a LSPR sensing platform based on Au nanospikes, which detected antibodies specific to the SARS-CoV-2 spike protein. Kim et al. [24] performed molecular diagnosis through a real-time label-free LSPR biosensor. The LSPR biosensor fabricated with gold nanoparticles detected DNA hybridization with an limit of detection (LOD) of 12.3 ng/mL. Takimoto et al. [42] fabricated porous silica covered Au-nanopatterned chips capable of detecting ppm level SO2. The manufactured chip can detect up to 20 ppm of SO2 through the LSPR sensing system. Ortega et al. [43] developed a platform to detect insulin secretion in situ by importing organ-on-a-chip technology to LSPR [Fig. 2(b)]. Barbir et al. [44] developed an Au nanoparticle-based LSPR chip based on a microfluidic chamber [Fig. 2(c)]. Through this LSPR chip, the interaction between nanoparticles and proteins was characterized. Shang et al. [45] developed an Au nanoislands LSPR chip detecting cis-jasmone to monitoring of growth pressure in plants. Austin Suthanthiraraj et al. [46] detected the dengue NS1 antigen using silver nanostructures LSPR chip prepared by thermal annealing on a metal film. Chen et al. [47] developed an LSPR chip by synthesizing Au@Ag core-shell nanourchins and depositing them on indium tin oxide (ITO) glass to detect volatile organic acids.

Figure F2
Chip-based LSPR device. (a) Schematic illustration of the LSPR sensor chip for biomarker detection. Reproduced with permission from [41], Copyrights 2019, Frontiers Media SA. (b) Schematic overview of the on-chip ...

3. Fiber-based LSPR sensor

The fiber-based LSPR sensor is one of the LSPR-based detection strategies. The configuration of the light source and spectrometer is the same as that of the chip-based LSPR sensing method, but the plasmonic substrate is manufactured with optical fibers. In particular, the advantage of the fiber-based LSPR device is that the light source is protected through the fiber, so materials in the aqueous sample can be measured effectively through the above advantage.

Halkare et al. [30] fabricated a fiber-based LSPR sensor using E. coli B40 bacteria to detect Hg2+ ions and Cd2+ ions, which are representative heavy metal ions. E. coli B40 bacteria were immobilized on the optic fiber coated with gold nanoparticles (AuNPs) using two bilayers of separately charged polyelectrolytes. The refractive index of the fiberbased LSPR sensor was shifted by heavy metal ions. These ions are interacted with surface groups on the surface of bacterial cells. In another study, Halkare et al. [48] developed a fiber-optic platform using bacteriophage as a biorecognition element to detect aquatic pathogenic bacteria (e.g., E. coli B40). E. coli B40 was randomly attached to AuNPs coated on the optic fiber but uniformly detected by bacteriophage in the range of 102 to 107 cfu/mL [Fig. 3(a)]. Nag et al. [29] fabricated a fiber-based LSPR sensor using optical fibers coated with AuNPs functionalized via bacteria (e.g., P. aeruginosa). The bacteria are decomposed by antibiotics, and this mechanism was used to diagnose the degree of exposure to antibiotics in the body. Huang et al. [49] presented a fiber-based LSPR sensor based on citrate-stabilized Au@AgPt core-shell nanospheres capable of sensitively detecting Cu2+ ions. The surface of the optical fiber probe is functionalized with polyethylenimine (PEI), which is a chelator of copper. The proposed fiber-based LSPR sensor obtained 10−16 mol/L LOD. Luo et al. [50] developed a fiber-based LSPR sensor detect N-glycan expression occurring on the cancer cell surface. Concanavalin A immobilized on AuNPs through mercaptoundecanoic acid binds with N-glycans, and cancer cells can be detected using this mechanism. The fabricated fiber-based LSPR sensor has a sensitive LOD of 30 cells/mL [50]. Antohe et al. [31] fabricated a polyaniline (PANI)/platinum (Pt)-coated fiber sensor to detect 4-nitrophenol (4NP), a toxic substance [Fig. 3(b)]. After coating a Pt thin film on optical fibers using the DC magnetron sputtering technique, the PANI layer reacting with 4NP was synthesized by polymerization method. These fiber-based LSPR sensors can detect 4NP with an LOD of 0.34 pM. Boruah et al. [51] detected Pb2+ ions in aqueous medium using an optical fiber coated with oxalic acid functionalized AuNPs. This optical fiber sensor showed a linear detection range from 1–20 ppb. Sadani et al. [52] developed an optical fiber platform that can detect Hg2+ ions using chitosan-capped gold nanoparticles and bovine serum albumin (BSA). H2+ ions binding to BSA were detected in the range of 0.1–540 ppb in biological and environmental samples. Sharma et al. [53] produced a fiber optic biosensor using taurine dioxygenase enzyme and AuNPs to detect taurine. This fiber optic biosensor has an LOD of 53 µM.

Figure F3
Fiber-based LSPR device. (a) Experimental scheme of different stages for the detection of bacteria and schematic about optical fiber LSPR setup. Reproduced with permission from [48], Copyrights 2021, American Chemical ...

4. Smartphone-based LSPR sensor

As LSPR sensors develop, various studies have attempted to produce portable LSPR devices. Neužil et al. [32] presented a lab-on-a-chip system based on multiplexed electrical current detection [Fig. 4(a)]. The absorption wavelength could be inferred using four LEDs as a light source. Cappi et al. [22] introduced a palm-sized transmission- LSPR setup [Fig. 4(b)]. This portable device was fabricated by depositing aptamer-functionalized gold nanoislands on a glass substrate covered with fluorine-doped tin oxide. This device detected tobramycin up to 0.5 µM in real-time.

Figure F4
Portable LSPR device. (a) Schematic of the handheld, battery-operated application specific lab-on-a-chip system. Reproduced with permission from [32], Copyrights 2014, The Royal Society of Chemistry. (b) Custom-made T-LSPR setup. i) ...

In particular, research on portable LSPR sensors based on smartphones is being actively conducted in accordance with the precise development of smartphones. Dutta et al. [33] demonstrated a colorimetric quantification platform for biological macromolecules using a smartphone. The sensor detected carbohydrates, enzyme, and BSA protein via D-glucose. Dutta et al. [54] fabricated another LSPR sensor using a smartphone [Fig. 5(a)]. The shift of the LSPR spectra caused by the conjugation between gold nanoparticles and analytes such as protein and enzyme. Then this spectrum was analyzed with the smartphone LSPR sensor. Using this sensor, the LOD of BSA protein is 0.28 µM and trypsin enzyme is 1.10 µM. Wang et al. [34] demonstrated plasmonic sensing platform based on smartphone. This platform presents colorimetric sensing by image processing and self referencing method achieving 100 times improved LOD on microplate reader [Fig. 5(b)]. The platform was tested with urine sample for evaluating under high protein concentrations. Sajed et al. [35] developed a precise colorimetric sensor based on smartphone compensated with machine learning algorithm. This smartphone sensor shows good linearity for Pb2+ detection under the concentration range of 0.5–2,000 ppb. Yang et al. [55] introduced a plasmonic immunoassay for detecting myoglobin via enzyme functionalized gold nanorods [Fig. 5(c)]. The linear detection range of the plasmonic immunoassay was 0.1– 1,000 ng/mL, and the LOD was 0.057 ng/mL. Fan et al. [56] developed a multitesting unit smartphone biosensor based on LSPR and multichannel microfluidics. The LOD of the biosensor was 4.2 U/mL on CA125 and 0.87 U/mL on CA15-3 through several clinical serum specimens. Li et al. [57] developed a smartphone-based volatile organic compound fingerprinting platform for the noninvasive diagnosis of late blight caused by Phytophthora infestans. This handheld device integrates plasmonic nano colorants and a disposable colorimetric sensor array to detect key plant volatiles at the ppm level within 1 min of reaction. Fu et al. [58] developed a portable smartphonebased plasmonic sensor readout platform for accurate quantification of plasmonic nanosensors. This platform detects the carcinoembryonic antigen by morphology change of triangular silver nanoprisms, and adenosine triphosphate by aggregation of gold nanoparticles. The research on Image J that analyzes images taken with smartphones is as follows. Aydindogan et al. [59] developed cancer biomarkers detecting immunoassay using Image J that calculate color changes depending on the biomarker concentration. By detecting the changes about color of AuNP, tumor biomarker was demonstrated on smartphone. In addition, a smartphone-integrated paper device fabricated from AuNPs/SuC using a smartphone and Image J software was used as a nanoprobe for the quantitative measurement of As3+. The results of colorimetry detection show linear region from 10 to 800 µg/L, and LOD is 4 µg/L [60].

Figure F5
Smartphone-based LSPR device. (a) Schematic of the proposed sensor, snapshot of the handheld smartphone integrated LSPR sensing tool and dispersed spectrum of the broadband source. Reproduced with permission from [54], ...

5. Conclusions

Here, we have reviewed the device composition of LSPR sensors. The first part of this review introduced the overview and basic configuration of the LSPR sensor. This section explained the three major parts of LSPR sensors and the pros and cons of device composition. In the second part, we investigated the chip-based LSPR sensor. With the various reported LSPR sensors, the configuration and measurement results of the sensors can be compared. The third part of our review described the fiber-based LSPR sensor. The fiber-based LSPR sensor, which has the advantage that the light source is protected against water, has shown efficient measurement results in water. The last part introduced the smartphone-based LSPR sensor. The application of LSPR sensors to smartphones is expected to increase in value as the device develops.

Article information

Applied Science and Convergence Technology.Mar 31, 2022; 31(2): 35-39.
Published online 2022-03-31. doi:  10.5757/ASCT.2022.31.2.35
aInfectious Disese Reserch Center, Kore Reserch Institute of Bioscience nd Biotechnology (KRIBB), Dejeon 34141, Republic of Kore
bNanoiotechnology and Bioinformatics (Major), University of Science & Technology (UST), Daejeon 34141, Repulic of Korea
*Corresponding author E-mail:oskwon79@kribb.re.kr
Received December 27, 2021; Accepted February 7, 2022.
Articles from Applied Science and Convergence Technology are provided here courtesy of Applied Science and Convergence Technology

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Figure 1


Composition of the LSPR device. (a) Schematic of the experimental setup used for LSPR sensing. Reproduced with permission from [ 7], Copyrights 2019, Elsevier. (b) LSPR setup for material detection. The setup includes a light source, a stage, and a spectrometer.

Figure 2


Chip-based LSPR device. (a) Schematic illustration of the LSPR sensor chip for biomarker detection. Reproduced with permission from [ 41], Copyrights 2019, Frontiers Media SA. (b) Schematic overview of the on-chip LSPR sensing platform integrated with islet-on-a-chip. Reproduced with permission from [ 43], Copyrights 2021, Multidisciplinary Digital Publishing Institute. (c) Customdesigned LSPR setup with a microfluidic chamber. Reproduced with permission from [ 44], Copyrights 2021, American Chemical Society.

Figure 3


Fiber-based LSPR device. (a) Experimental scheme of different stages for the detection of bacteria and schematic about optical fiber LSPR setup. Reproduced with permission from [ 48], Copyrights 2021, American Chemical Society. (b) Schematic of the FO-SPR sensing platform and photograph of the fabricated Pt-coated LSPR sensor inserted into the SMA connector. Reproduced with permission from [ 31], Copyrights 2021, Nature.

Figure 4


Portable LSPR device. (a) Schematic of the handheld, battery-operated application specific lab-on-a-chip system. Reproduced with permission from [ 32], Copyrights 2014, The Royal Society of Chemistry. (b) Custom-made T-LSPR setup. i) Digital rendering of the components of the T-LSPR setup. ii) Side view with relative distances indicated. iii) Picture of the complete setup. Reproduced with permission from [ 22], Copyrights 2015, American Chemical Society.

Figure 5


Smartphone-based LSPR device. (a) Schematic of the proposed sensor, snapshot of the handheld smartphone integrated LSPR sensing tool and dispersed spectrum of the broadband source. Reproduced with permission from [ 54], Copyrights 2016, The Royal Society of Chemistry. (b) Smartphone based portable colorimetric sensing platform and real image of optical detection setup. Reproduced with permission from [ 34], Copyrights 2017, American Chemical Society. (c) Schematic diagram of the AuNRs-based plasmonic immunoassay for Myo detection. Reproduced with permission from [ 55], Copyrights 2018, Springer Nature.