Fiber Optic Particle Plasmon Resonance Biosensor for Label-Free Detection of Nucleic Acids and Its Application to HLA-B27 mRNA Detection in Patients with Ankylosing Spondylitis

Competitive Assay for the Ultrasensitive Detection of Organophosphate Pesticides Based on a Fiber-Optic Particle Plasmon Resonance Biosensor and an Acetylcholinesterase Binding Peptide

An acetylcholinesterase (AChE) binding-based biosensor was developed for the ultrasensitive detection of organophosphate (OP) pesticides. The biosensor integrates the technique based on fiber-optic particle plasmon resonance detection and a synthetic AChE binding peptide conjugated with gold nanoparticles on the optical fiber surface via an AChE competitive binding assay. The OP pesticides present in the solution hinder the binding of AChE to the peptide on the biosensor by competing for the binding sites present in AChE. The limit of detection obtained for parathion using this method was observed to be 0.66 ppt (2.3 pM). This method shows a wide linear dynamic range of 6 orders. Furthermore, the use of the AChE binding peptide in the biosensor can better discriminate OPs against carbamates by using only a single biosensor. The practical application of this method was tested using spiked samples, which yielded good recovery and reproducibility. The spiked sample required minimal pretreatment before analysis; hence, this biosensor may also be used in the field.

Recent Advancements of LSPR Fiber-Optic Biosensing: Combination Methods, Structure, and Prospects

Fiber-optic biosensors based on localized surface plasmon resonance (LSPR) have the advantages of great biocompatibility, label-free, strong stability, and real-time monitoring of various analytes. LSPR fiber-optic biosensors have attracted extensive research attention in the fields of environmental science, clinical medicine, disease diagnosis, and food safety. The latest development of LSPR fiber-optic biosensors in recent years has focused on the detection of clinical disease markers and the detection of various toxic substances in the environment and the progress of new sensitization mechanisms in LSPR fiber-optic sensors. Therefore, this paper reviews the LSPR fiber-optic sensors from the aspects of working principle, structure, and application fields in biosensors. According to the structure, the sensor can be divided into three categories: traditional ordinary optical fiber, special shape optical fiber, and specialty optical fiber. The advantages and disadvantages of existing and future LSPR fiber-optic biosensors are discussed in detail. Additionally, the prospect of future development of fiber-optic biosensors based on LSPR is addressed.

Trace Determination of Grouper Nervous Necrosis Virus in Contaminated Larvae and Pond Water Samples Using Label-Free Fiber Optic Nanoplasmonic Biosensor

We developed a fast (<20 min), label-free fiber optic particle plasmon resonance (FOPPR) immunosensing method to detect nervous necrosis virus (NNV), which often infects high-value economic aquatic species, such as grouper. Using spiked NNV particles in a phosphate buffer as samples, the standard calibration curve obtained was linear (R2 = 0.99) and the limit of detection (LOD) achieved was 2.75 × 104 TCID50/mL, which is superior to that obtained using enzyme-linked immunosorbent assay (ELISA). By using an enhancement method called fiber optic nanogold-linked immunosorbent assay (FONLISA), the LOD can be further improved to <1 TCID50/mL, which is comparable to that found by the conventional qPCR method. Employing the larvae homogenate samples of NNV-infected grouper, the results obtained by the FOPPR biosensor agree with those obtained by the quantitative polymerase chain reaction (qPCR) method. We also examined pond water samples from an infected container in an indoor aquaculture facility. The lowest detectable level of NNV coat protein was found to be 0.17 μg/mL, which is one order lower than the LOD reported by ELISA. Therefore, we demonstrated the potential of the FOPPR biosensor as an outbreak surveillance tool, which is able to give warning indication even when the trend of larvae death toll increment is still not clear.

Quantitative and amplification-free detection of SOCS-1 CpG methylation percentage analyses in gastric cancer by fiber optic nanoplasmonic biosensor

A new innovative approach is essential for early and effective diagnosis of gastric cancer, using promoter hypermethylation of the tumor suppressor, SOCS-1, that is frequently inactivated in human cancers. We have developed an amplification-free fiber optic nanoplasmonic biosensor for detecting DNA methylation of the SOCS-1 human genome. The method is based on the fiber optic nanogold-linked sorbent assay of PCR-free DNA from human gastric tumor tissue and cell lines. We designed a specific DNA probe fabricated on the fiber core surface while the other probe is bioconjugated with gold nanoparticles in free form to allow percentage determination and differentiating the methylated and unmethylated cell lines, further demonstrating the SOCS-1 methylation occurs in cancer patients but not in normal cell lines. The observed detection limit is 0.81 fM for methylated DNA, and the detection time is within 15 min. In addition, our data were significantly correlated to the data obtained from PCR-based pyrosequencing, and yet with superior accuracy. Hence our results provide new insight to the quantitative evaluation of methylation status of the human genome and can act as an alternative to PCR with a great potential.

Integration of Power-Free and Self-Contained Microfluidic Chip with Fiber Optic Particle Plasmon Resonance Aptasensor for Rapid Detection of SARS-CoV-2 Nucleocapsid Protein

The global pandemic of COVID-19 has created an unrivalled need for sensitive and rapid point-of-care testing (POCT) methods for the detection of infectious viruses. For the novel coronavirus SARS-CoV-2, the nucleocapsid protein (N-protein) is one of the most abundant structural proteins of the virus and it serves as a useful diagnostic marker for detection. Herein, we report a fiber optic particle plasmon resonance (FOPPR) biosensor which employed a single-stranded DNA (ssDNA) aptamer as the recognition element to detect the SARS-CoV-2 N-protein in 15 min with a limit of detection (LOD) of 2.8 nM, meeting the acceptable LOD of 10⁶ copies/mL set by the WHO target product profile. The sensor chip is a microfluidic chip based on the balance between the gravitational potential and the capillary force to control fluid loading, thus enabling the power-free auto-flowing function. It also has a risk-free self-contained design to avoid the risk of the virus leaking into the environment. These findings demonstrate the potential for designing a low-cost and robust POCT device towards rapid antigen detection for early screening of SARS-CoV-2 and its related mutants.

Determination of the Highly Sensitive Carboxyl-Graphene Oxide-Based Planar Optical Waveguide Localized Surface Plasmon Resonance Biosensor

This study develops a highly sensitive and low-cost carboxyl-graphene-oxide-based planar optical waveguide localized surface plasmon resonance biosensor (GO-OW LSPR biosensor), a system based on measuring light intensity changes. The structure of the sensing chip comprises an optical waveguide (OW)-slide glass and microfluidic-poly (methyl methacrylate) (PMMA) substrate, and the OW-slide glass surface-modified gold nanoparticle (AuNP) combined with graphene oxide (GO). As the GO has an abundant carboxyl group (–COOH), the number of capture molecules can be increased. The refractive index sensing system uses silver-coated reflective film to compare the refractive index sensitivity of the GO-OW LSPR biosensor to increase the refractive index sensitivity. The result shows that the signal variation of the system with the silver-coated reflective film is 1.57 times that of the system without the silver-coated reflective film. The refractive index sensitivity is 5.48 RIU⁻¹ and the sensor resolution is 2.52 ± 0.23 × 10⁻⁶ RIU. The biochemical sensing experiment performs immunoglobulin G (IgG) and streptavidin detection. The limits of detection of the sensor for IgG and streptavidin are calculated to be 23.41 ± 1.54 pg/mL and 5.18 ± 0.50 pg/mL, respectively. The coefficient of variation (CV) of the repeatability experiment (sample numbers = 3) is smaller than 10.6%. In addition, the affinity constants of the sensor for anti-IgG/IgG and biotin/streptavidin are estimated to be 1.06 × 10⁷ M⁻¹ and 7.30 × 10⁹ M⁻¹, respectively. The result shows that the GO-OW LSPR biosensor has good repeatability and very low detection sensitivity. It can be used for detecting low concentrations or small biomolecules in the future.

Dual-functional gold-iron oxide core-satellite hybrid nanoparticles for sensitivity enhancement in biosensors via nanoplasmonic and preconcentration effects

A common strategy to improve the sensitivity of a biosensor for the detection of a low abundance analyte is to preconcentrate the analyte molecules before detection. A dual-functional gold-iron oxide core-satellite hybrid nanoparticle structure is proposed in this work to overcome the drawbacks of traditional sample pretreatment methods and the methods using non-magnetic nanomaterials for sample pretreatment. The new dual-functional hybrid nanoparticle structure can simultaneously serve as a signal reporter of a biorecognition event and a preconcentrator of a target at an extremely low concentration in a nanoplasmonic biosensor. By utilizing a fiber optic nanogold-linked sorbent assay in the fiber optic particle plasmon resonance (FOPPR) biosensor and an arbitrary DNA sequence as a target, we have demonstrated that the use of the new hybrid nanoparticle structure with magnetic preconcentration improves the limit of detection (LOD) for the DNA by 18 times as compared to the same method without magnetic preconcentration, so that the LOD for detecting the DNA can be as low as 2.6 fM. The new hybrid nanoparticle structure is easy to prepare and its use in the high-sensitivity and low-cost FOPPR biosensor provides vast opportunities in point-of-care applications.

MutS protein-based fiber optic particle plasmon resonance biosensor for detecting single nucleotide polymorphisms

A new biosensing method is presented to detect gene mutation by integrating the MutS protein from bacteria with a fiber optic particle plasmon resonance (FOPPR) sensing system. In this method, the MutS protein is conjugated with gold nanoparticles (AuNPs) deposited on an optical fiber core surface. The target double-stranded DNA containing an A and C mismatched base pair in a sample can be captured by the MutS protein, causing increased absorption of green light launching into the fiber and hence a decrease in transmitted light intensity through the fiber. As the signal change is enhanced through consecutive total internal reflections along the fiber, the limit of detection for an AC mismatch heteroduplex DNA can be as low as 0.49 nM. Because a microfluidic chip is used to contain the optical fiber, the narrow channel width allows an analysis time as short as 15 min. Furthermore, the label-free and real-time nature of the FOPPR sensing system enables determination of binding affinity and kinetics between MutS and single-base mismatched DNA. The method has been validated using a heterozygous PCR sample from a patient to determine the allelic fraction. The obtained allelic fraction of 0.474 reasonably agrees with the expected allelic fraction of 0.5. Therefore, the MutS-functionalized FOPPR sensor may potentially provide a convenient quantitative tool to detect single nucleotide polymorphisms in biological samples with a short analysis time at the point-of-care sites.

Integrated Graphene Oxide with Noble Metal Nanoparticles to Develop High-Sensitivity Fiber Optic Particle Plasmon Resonance (FOPPR) Biosensor for Biomolecules Determination

In this research, a direct, simple and ultrasensitive fiber optic particle plasmon resonance (FOPPR) biosensing platform for immunoglobulin G (IgG) detection was developed using a gold nanoparticle/graphene oxide (AuNP/GO) composite as signal amplification element. To obtain the best analytical performance of the sensor, experimental parameters including the surface concentration of GO on the AuNPs, formation time of the GO, the concentration of the anti-IgG and incubation time of anti-IgG were optimized. The calibration plots displayed a good linear relationship between the sensor response (ΔI/I₀) and the logarithm of the analyte concentrations over a linear range from 1.0 × 10⁻¹⁰ to 1.0 × 10⁻⁶ g/mL of IgG under the optimum conditions. A limit of detection (LOD) of 0.038 ng/mL for IgG was calculated from the standard calibration curve. The plot has a linear relationship (correlation coefficient, R = 0.9990). The analytical performance of present work’s biosensor was better than that of our previously reported mixed self-assembled monolayer of 11-mercaptoundecanoic acid/6-mercapto-1-hexanol (MUA/MCH = 1:4) method by about three orders of magnitude. The achieved good sensitivity may be attributed to the synergistic effect between GO and AuNPs in this study. In addition, GO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Furthermore, we also demonstrated that the results from this sensor have good reproducibility, with coefficients of variation (CVs) < 8% for IgG. Therefore, the present strategy provides a novel and convenient method for chemical and biochemical quantification and determination.