The surface plasmon resonance (SPR) biosensor has become a powerful analytical tool for investigating biomolecular interactions. There are several methods to excite surface plasmon, such as coupling with prisms, fiber optics, grating, nanoparticles, etc. The challenge in developing this type of biosensor is to increase its sensitivity. In relation to this, graphene is one of the materials that is widely studied because of its unique properties. In several studies, this material has been proven theoretically and experimentally to increase the sensitivity of SPR. This paper discusses the current development of a graphene-based SPR biosensor for various excitation methods. The discussion begins with a discussion regarding the properties of graphene in general and its use in biosensors. Simulation and experimental results of several excitation methods are presented. Furthermore, the discussion regarding the SPR biosensor is expanded by providing a review regarding graphene-based Surface-Enhanced Raman Scattering (SERS) biosensor to provide an overview of the development of materials in the biosensor in the future.

Since graphene was first isolated in 2004, research related to graphene-based 2D material for surface plasmon resonance (SPR) biosensor applications has increased. Recently, other types of 2D materials such as Transition Metal Dichalcogenides have also been investigated. This 2D material has exceptional optical and electronic properties and can be utilized to improve the performance of biosensors. The performance of SPR biosensors can be determined based on their sensitivity and detection accuracy (DA). To find out the sensitivity and DA, simulation approach can be done. In this paper, we perform SPR simulations on monolayer and multilayer structures of 2D material, namely graphene, graphene oxide, molibdenum disulfida, and tungsten diselenide. In addition, we also investigated the sensitivity and DA of SPR biosensors on hybrid structures. The results obtained indicate that the use of 2D material can increase the sensitivity of the SPR up to 5 times when compared to conventional structures. Of the four types of 2D material investigated, GO is the material with the best accuracy. If the SPR biosensor performance is determined based on the FOM value, the best performance is owned by the GO-based SPR structure with a sensitivity of 151.87 deg/RIU and DA 0.22 deg-1.

Background: Due to educational, social and economic reasons, more and more women are delaying childbirth. However, advanced maternal age is associated with several adverse pregnancy outcomes, and in particular a high risk of Down’s syndrome (DS). Hence, it is increasingly important to be able to detect fetal Down’s syndrome (FDS). Methods: We developed an effective, highly sensitive, surface plasmon resonance (SPR) biosensor with biochemically amplified responses using carboxyl-molybdenum disulfide (MoS₂) film. The use of carboxylic acid as a surface modifier of MoS₂ promoted dispersion and formed specific three-dimensional coordination sites. The carboxylic acid immobilized unmodified antibodies in a way that enhanced the bioaffinity of MoS₂ and preserved biorecognition properties of the SPR sensor surface. Complete antigen pregnancy-associated plasma protein-A2 (PAPP-A2) conjugated with the carboxyl-MoS₂-modified gold chip to amplify the signal and improve detection sensitivity. This heterostructure interface had a high work function, and thus improved the efficiency of the electric field energy of the surface plasmon. These results provide evidence that the interface electric field improved performance of the SPR biosensor. Results: The carboxyl-MoS₂-based SPR biosensor was used successfully to evaluate PAPP-A2 level for fetal Down’s syndrome screening in maternal serum samples. The detection limit was 0.05 pg/mL, and the linear working range was 0.1 to 1100 pg/mL. The women with an SPR angle > 46.57 m° were more closely associated with fetal Down’s syndrome. Once optimized for serum Down’s syndrome screening, an average recovery of 95.2% and relative standard deviation of 8.5% were obtained. Our findings suggest that carboxyl-MoS₂-based SPR technology may have advantages over conventional ELISA in certain situations. Conclusion: Carboxyl-MoS₂-based SPR biosensors can be used as a new diagnostic technology to respond to the increasing need for fetal Down’s syndrome screening in maternal serum samples. Our results demonstrated that the carboxyl-MoS₂-based SPR biosensor was capable of determining PAPP-A2 levels with acceptable accuracy and recovery. We hope that this technology will be investigated in diverse clinical trials and in real case applications for screening and early diagnosis in the future.

Until now, two-dimensional (2D) nanomaterials have been widely studied and applied in the biosensor field. Some of the advantages offered by these 2D materials include large specific surface area, high conductivity, and easy surface modification. This review discusses the use of 2D material in surface plasmon resonance (SPR) biosensor for diagnostic applications. Two-dimensional material reviewed includes graphene and molybdenum disulfide (MoS₂). The discussion begins with a brief introduction to the general principles of the SPR biosensor. The discussion continues by explaining the properties and characteristics of each material and its effect on the performance of the SPR biosensor, in particular its sensitivity. This review concludes with some recent applications of graphene- and MoS₂-based SPR biosensor in diagnostic applications.

The development of sensitive and specific exosome detection tools is essential because they are believed to provide specific information that is important for early detection, screening, diagnosis, and monitoring of cancer. Among the many detection tools, surface-plasmon resonance (SPR) biosensors are analytical devices that offer advantages in sensitivity and detection speed, thereby making the sample-analysis process faster and more accurate. In addition, the penetration depth of the SPR biosensor, which is <300 nm, is comparable to the size of the exosome, making the SPR biosensor ideal for use in exosome research. On the other hand, another type of nanoplasmonic sensor, namely a localized surface-plasmon resonance (LSPR) biosensor, has a shorter penetration depth of around 6 nm. Structural optimization through the addition of supporting layers and gap control between particles is needed to strengthen the surface-plasmon field. This paper summarizes the progress of the development of SPR and LSPR biosensors for detecting exosomes. Techniques in signal amplification from two sensors will be discussed. There are three main parts to this paper. The first two parts will focus on reviewing the working principles of each sensor and introducing several methods that can be used to isolate exosomes. This article will close by explaining the various sensor systems that have been developed and the optimizations carried out to obtain sensors with better performance. To illustrate the performance improvements in each sensor system discussed, the parameters highlighted include the detection limit, dynamic range, and sensitivity.

Effect of Fe₃O₄ magnetic nanoparticle concentration on the signal of surface plasmon resonance (SPR) spectra has been successfully observed. The Fe₃O₄ nanoparticles with a particle size of about 10.5 ± 0.2 nm were used as active materials to increase the SPR response. X-ray diffraction (XRD) pattern showed that Fe₃O₄ nanoparticles have a high degree of crystallinity with spinel structure. The SPR system was successfully set up by using a glass prism coupler in a Kretschmann configuration in which gold (Au) thin film was thermally evaporated on the prism base. A green laser of wavelength 543 nm was used as light source. The angular scan in the attenuated total reflection (ATR) spectra showed a dropping intensity. Those things clearly indicated the appearance of SPR coupling phenomenon on the interface of Au thin film. The SPR spectra of fixed Au masses were also performed with same angular positions of dips. The Fe₃O₄ nanoparticles were deposited on gold thin film as a third layer which was synthesized via co-precipitation method. Hence, it was observed that the variation of Fe₃O₄ concentration affected the SPR spectra profile. The concentrations of Fe₃O₄ nanoparticles are 1, 3, 5, 7, 9, and 11 mg/ml which correspond to the angle shift of 0.1°, 0.3°, 0.5°, 0.7°, 0.9°, and 1.0°, respectively. The SPR angle of the dip was shifted to higher value due to change of refractive index of the medium as Fe₃O₄ nanoparticles concentration increases. Based on this result, we can conclude that the angle shift of SPR increases with increasing concentration of Fe₃O₄ nanoparticles.