SERS-based Lateral Flow Immunoassay Research Articles

SERS-Based Lateral Flow Immunoassay Combined with Enzymatic Recombinase Amplification for Quantitative, High-Sensitive Detection of Influenza A Virus

SERS-Based Lateral Flow Immunoassay Combined with Enzymatic Recombinase Amplification for Quantitative, High-Sensitive Detection of Influenza A Virus

Portable SERS-based lateral flow immunoassay strips with self-calibration for detection of a prostate cancer biomarker

Serum prostate-specific antigen (PSA) is thought to be the most vital indicator for early identification, staging and monitoring of prostate cancer (PCa). Although lateral flow immunoassay (LFA) has demonstrated limitless promise for point-of-care testing (POCT) and has drawn increasing interest and attention, there are significant restrictions on the assay's sensitivity and quantitative capability. Surface-enhanced Raman spectroscopy-based LFA (SERS-LFA) technique integrates the great sensitivity of SERS with the simplicity, rapidity, and usability of the LFA technique, making it ideal for POCT. In this paper, we propose a sensitive self-calibrating SERS-LFA platform, which uses Au@MBN@Ag@PSA NPs as a SERS immunoprobe for the specific recognition of PSA and loads graphene oxide/gold nanoparticles (GO/Au NPs) on nitrocellulose (NC) membranes as an internal standard (IS) molecule. The SERS-LFA platform's detection accuracy is increased through dynamic calibration of the characteristic signals, which is accomplished by detecting the immunoprobe and IS signals simultaneously and computing their respective signal intensity ratios. The self-calibrated SERS-LFA platform demonstrated a 1.65-fold improvement in reproducibility over the conventional SERS-LFA, and PSA could only be detected to a limit of 0.08 ng/mL, meaning that it was 3.5-fold lower than the conventional SERS-LFA platform. The spike recovery experiments yielded recoveries of 96.16∼104.53% with RSD values of 9.37%, 8.66%, and 3.49%, respectively, demonstrating that our self-calibrated SERS-LFA platform for PSA quantification has an acceptable level of precision and has great prospect for early screening of PCa and other diseases.

Simultaneously ultrasensitive and quantitative detection of influenza A virus, SARS-CoV-2, and respiratory syncytial virus via multichannel magnetic SERS-based lateral flow immunoassay

Respiratory viruses usually induced similar clinical symptoms at early infection. Herein, we presented a multichannel surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-based LFA) using high-performance magnetic SERS tags for the simultaneous ultrasensitive detection of respiratory viruses, namely influenza A virus (H1N1), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and respiratory syncytial virus (RSV) in biological samples. As-prepared magnetic SERS tags can directly enrich and capture target viruses without pretreatment of samples, avoiding the interference of impurities in the samples as well as improving the sensitivity. With the capture-detection method, the detection limits of the proposed assay reached 85 copies mL−1, 8 pg mL−1, and 8 pg mL−1 for H1N1, SARS-CoV-2 and RSV, respectively. Moreover, the detection properties of the proposed method for target viruses in throat swab samples were verified, suggesting its remarkable potential for the early and rapid differential diagnosis of respiratory viruses.

SERS-based lateral flow immunoassay strip for ultrasensitive and quantitative detection of acrosomal protein SP10

Ultrasensitive and quantitative detection of acrosomal protein SP10 is of great significance in diagnosis of male infertility. Herein, a novel point of care testing (POCT) device composed of surface enhanced Raman scattering-based lateral flow immunoassay strip (SERS-LFA) was first developed for ultrasensitive and quantitative detection of SP10. In the design, the SP10 could be authenticated by gold-silver core–shell nanorod SERS nanotags, and the as-proposed device employed the LFA as a carrier. It is found that the POCT device exhibited excellent properties for the SP10 detection with a good linearity in the range of 100 fg mL−1 to 10 ng mL−1, and detection limit of 25.12 fg mL−1, which corresponds to several hundred sperm per milliliter. We anticipate this device will be widely used in the field of male reproductive diagnosis and provide guidance to the fertility planning of age-appropriate couples.

SERS-based lateral flow immunoassay for sensitive and simultaneous detection of anti-SARS-CoV-2 IgM and IgG antibodies by using gap-enhanced Raman nanotags

The lateral flow immunoassay (LFIA) has played a crucial role in early diagnosis during the current COVID-19 pandemic owing to its simplicity, speed and affordability for coronavirus antibody detection. However, the sensitivity of the commercially available LFIAs needs to be improved to better prevent the spread of the infection. Here, we developed an ultra-sensitive surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-based LFIA) strip for simultaneous detection of anti-SARS-CoV-2 IgM and IgG by using gap-enhanced Raman nanotags (GERTs). The GERTs with a 1 nm gap between the core and shell were used to produce the “hot spots”, which provided about 30-fold enhancement as compared to conventional nanotags. The COVID-19 recombinant antigens were conjugated on GERTs surfaces and replaced the traditional colloidal gold for the Raman sensitive detection of human IgM and IgG. The LODs of IgM and IgG were found to be 1 ng/mL and 0.1 ng/mL (about 100 times decrease was observed as compared to commercially available LFIA strips), respectively. Moreover, under the condition of common nano-surface antigen, precise SERS signals proved the unreliability of quantitation because of the interference effect of IgM on IgG.

SERS-Based Lateral Flow Immunoassay Strip for Ultrasensitive and Quantitative Detection of Acrosomal Protein SP10

SERS-Based Lateral Flow Immunoassay Strip for Ultrasensitive and Quantitative Detection of Acrosomal Protein SP10

Development of a SERS-based lateral flow immunoassay for rapid and ultra-sensitive detection of anti-SARS-CoV-2 IgM/IgG in clinical samples

The accurate and rapid screening of serum antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the key to control the spread of 2019 coronavirus disease (COVID-19). In this study, we reported a surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-LFIA) for the simultaneous detection of anti-SARS-CoV-2 IgM/IgG with high sensitivity. Novel SERS tags labeled with dual layers of Raman dye were fabricated by coating a complete Ag shell on SiO2 core (SiO2@Ag) and exhibited excellent SERS signals, good monodispersity, and high stability. Anti-human IgM and IgG were immobilized onto the two test lines of the strip to capture the formed SiO2@Ag-spike (S) protein-anti-SARS-CoV-2 IgM/IgG immunocomplexes. The SERS signal intensities of the IgM and IgG test zones were easily recorded by a portable Raman instrument and used for the high-sensitivity analysis of target IgM and IgG. The limit of detection of SERS-LFIA was 800 times higher than that of standard Au nanoparticle-based LFIA for target IgM and IgG. The SERS-LFIA biosensor was tested on 19 positive serum samples from COVID-19 patients and 49 negative serum samples from healthy people to demonstrate the clinical feasibility of our proposed assay. The results revealed that the proposed method exhibited high accuracy and specificity for patients with SARS-CoV-2 infection.

Rapid, Quantitative, High-Sensitive Detection of Escherichia coli O157:H7 by Gold-Shell Silica-Core Nanospheres-Based Surface-Enhanced Raman Scattering Lateral Flow Immunoassay.

Escherichia coli O157:H7 is regarded as one of the most harmful pathogenic microorganisms related to foodborne diseases. This paper proposes a rapid-detection biosensor for the sensitive and quantitative analysis of E. coli O157:H7 in biological samples by surface-enhanced Raman scattering (SERS)-based lateral flow immunoassay (LFIA). A novel gold-shell silica-core (SiO2/Au) nanosphere (NP) with monodispersity, good stability, and excellent SERS activity was utilized to prepare high-performance tags for the SERS-based LFIA system. The SiO2/Au SERS tags, which were modified with two layers of Raman reporter molecules and monoclonal antibodies, effectively bind with E. coli O157:H7 and form sandwich immune complexes on the test lines. E. coli O157:H7 was quantitatively detected easily by detecting the Raman intensity of the test lines. Under optimal conditions, the limit of detection (LOD) of the SiO2/Au-based SERS-LIFA strips for the target bacteria was 50 cells/mL in PBS solution, indicating these strips are 2,000 times more sensitive than colloidal Au-based LFIA strips. Moreover, the proposed assay demonstrated high applicability in E. coli O157:H7 detection in biological samples, including tap water, milk, human urine, lettuce extract and beef, with a low LOD of 100 cells/mL. Results indicate that the proposed SERS-based LFIA strip is applicable for the sensitive and quantitative determination of E. coli O157:H7.

Portable and multiplexed lateral flow immunoassay reader based on SERS for highly sensitive point-of-care testing

A portable surface-enhanced Raman scattering (SERS)-based lateral flow immunoassay (LFIA) reader with multiplexed detection was developed using an integrated LFIA reaction column. The proposed LFIA reader was designed to simultaneously detect multiple samples or samples with multiple biomarkers. With the integrated LFIA reaction column, we achieved the specific detection of alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and prostate-specific antigen (PSA) with a detection limit of 0.01 ng/mL, which was three orders of magnitude lower than that of the visual signal. We also investigated the uniformity of channels based on an eight-channel integrated LFIA reaction column. The relative standard deviation values of the SERS intensity of the eight-channel for measuring the AFP, CEA, and PSA antigens at 1323 cm−1 were 13%, 4.8%, and 5%, respectively. We detected 45 clinical serum samples of the three antigens using the proposed portable SERS-based LFIA reader to further confirm its applicability to clinical samples. The SERS signals of the positive sera were higher than those of the negative sera and their thrice standard deviation. This result indicated the practicality of the developed integrated reaction column and the proposed portable and multiplexed Raman reader. This work provides a new high-sensitivity, multiplexed, and automated SERS-based LFIA detector for use in the point-of-care setting.

The simultaneous detection of the squamous cell carcinoma antigen and cancer antigen 125 in the cervical cancer serum using nano-Ag polydopamine nanospheres in an SERS-based lateral flow immunoassay.

The accurate analysis of tumor related biomarkers is extremely critical in the diagnosis of the early stage cervical cancer. Herein, we designed a novel and inexpensive surface-enhanced Raman scattering-based lateral flow assay (SERS-based LFA) strip with a single test line, which was applied for the rapid and sensitive quantitative simultaneous analysis of SCCA and CA125 in serum samples from patients with cervical cancer. In the presence of target antigens, the monoclonal antibody-coupled and Raman reporter-labeled nano-Ag polydopamine nanospheres (PDA@Ag-NPs) aggregated on the test line modified by the polyclonal antibody to form a double-antibody sandwich structure. The finite difference time domain simulation demonstrated that large number of “hot spots” was generated among the nanogaps of aggregated PDA@AgNPs, which resulted in a huge enhancement of the signal of the Raman reporters. Accordingly, the limit of detection was determined to be 7.156 pg mL−1 for SCCA and 7.182 pg mL−1 for CA125 in phosphate buffer and 8.093 pg mL−1 for SCCA and 7.370 pg mL−1 for CA125 in human serum, revealing high sensitivity of this SERS-based LFA strip. Significantly, the detection of SCCA and CA125 using the SERS-based LFA was observed to have high specificity and reproducibility, and the whole detection was completed within 20 min. Furthermore, the SERS-based LFA and enzyme-linked immunosorbent assay were also employed in serum samples obtained from patients with cervical cancer, cervical intraepithelial neoplasia and healthy subjects, and perfect agreement existed between both the methods. Thus, clinically, the developed SERS-based LFA strip has strong potential for the simultaneous detection of multiple cancer biomarkers in serum.

Sub-100 nm multi-shell bimetallic gap-enhanced Raman tags

Gap-enhanced Raman tags (GERTs) with built-in Raman molecules show excellent surface-enhanced Raman scattering (SERS) performance and great potential for biomedical applications. In this work, we add a silver (Ag) shell to gold (Au) single-shell GERTs (Au@BDT@Au) to form Au-Ag hybrid multi-shell nanoparticles. It is found that this modification enhances the SERS performance of the NPs and that the thickness of the Ag shell is a key factor in determining the enhancement. Double-shell bimetallic GERTs with a Au core, Au shell and exterior 2 nm-thickness silver shell (Au@BDT@Au@BDT@Ag) show the best SERS performance and good photostability. Moreover, we utilize the double-shell bimetallic GERTs to develop a new kind of SERS-based lateral flow immunoassay (LFIA), acheiving limit of detection as low as 0.7 mIU/mL (0.077 ng/mL). We demonstrated a simple way to fabricate sub-100 nm multi-shell bimetallic GERTs for use as SERS probes with strong Raman signals with potential for in vivo and in vitro application as bioimaging and biosensing probes.

SERS-based lateral flow immunoassay of troponin I by using gap-enhanced Raman tags

The lateral flow immunoassay (LFIA) has emerged as a powerful tool for rapid screening owing to its simplicity and flexibility for detection of various biomarkers. However, conventional LFIA strips have several disadvantages, including limits in quantitative analysis and low sensitivity. Here we developed a novel surface-enhanced Raman scattering LFIA based on nonspherical gap-enhanced Raman tags (GERTs), with Raman molecules (RMs) embedded in a 1-nm gap between Au nanorod core and Au shell. Such tags have a strong and uniform SERS response, an order of magnitude higher than that of other common SERS tags such as Au nanorods, nanostars, Au nanoshells with surface-adsorbed RMs, or spherical GERTs with embedded RMs. The feasibility of the tags was demonstrated by the semiquantitative and sensitive detection of the heart disease biomarker cardiac troponin I (cTnI). GERTs were conjugated with monoclonal antibodies and used for LFIA in the same way as ordinary functionalized colloidal gold. The presence of the target antigen, cTnI, was identified by Raman microscopy mapping of the test zone. With the SERS-based LFIA, the limit of cTnI detection was about 0.1 ng/mL. This value is within the diagnostic range of cTnI in the blood serum of patients with heart infarction and is 30 times lower than that of the colorimetric LFIA test using the same antibodies and either GERTs or colloidal gold as labels.

Dual dye-loaded Au@Ag coupled to a lateral flow immunoassay for the accurate and sensitive detection of Mycoplasma pneumoniae infection.

We present an attractive model of surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-LFIA) for the sensitive and accurate detection of Mycoplasma pneumoniae (MP) infection in human serum. The SERS-LFIA strip uses Au@Ag nanoparticles (Au@Ag NPs) loaded with two layers of Raman dye 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) as SERS tags. The advantages of the dual dye-loaded SERS tags (Au/DTNB@Ag/DTNB) are the high sensitivity and the bioconjugation flexibility of the detection antibody. As determined from our SERS-LFIA strip, human IgM was quantified by monitoring the SERS signal on the test line. The limit of detection for human IgM was 0.1 ng mL−1, which was 100 times more sensitive than that by using the colorimetric method. Our assay results for 20 MP-specific IgM positive serum specimens showed 100% accuracy and detection rate, whereas the parallel enzyme-linked immunosorbent assay only showed 85% detection rate. The SERS-LFIA strip also exhibited high specificity and potential clinical applications. Therefore, our SERS-based LFIA strip has strong potential for practical applications in the sensitive and rapid detection of MP.

Quantitative analysis of thyroid-stimulating hormone (TSH) using SERS-based lateral flow immunoassay

We report the development of a surface-enhanced Raman scattering (SERS)-based lateral flow immunoassay (LFIA) sensor for the highly sensitive detection of thyroid-stimulating hormone (TSH) in clinical fluids. Here, Raman reporter-labeled gold nanoparticles (AuNPs) were used as SERS nano tags. Using this SERS-based LFIA test strip, the presence of TSH could be identified through a color change in the test line. In addition, quantitative evaluation of TSH was possible by monitoring the characteristic Raman peak intensity of SERS nano tags. The limit of detection (LOD) was estimated to be 0.025μIU/mL, which is approximately two orders of magnitude more sensitive than that achieved from the conventional colorimetric LFIA sensor based on the naked eye. Consequently, it is possible to diagnose hyperthyroidism as well as hypothyroidism since a TSH concentration lower than 0.5μIU/mL can be detected using this SERS-based LFIA detection technique. Therefore, this approach has strong potential feasibility for application in the early diagnosis of TSH hormone-related diseases.

Application of a SERS-based lateral flow immunoassay strip for the rapid and sensitive detection of staphylococcal enterotoxin B.

A novel surface-enhanced Raman scattering (SERS)-based lateral flow immunoassay (LFA) biosensor was developed to resolve problems associated with conventional LFA strips (e.g., limits in quantitative analysis and low sensitivity). In our SERS-based biosensor, Raman reporter-labeled hollow gold nanospheres (HGNs) were used as SERS detection probes instead of gold nanoparticles. With the proposed SERS-based LFA strip, the presence of a target antigen can be identified through a colour change in the test zone. Furthermore, highly sensitive quantitative evaluation is possible by measuring SERS signals from the test zone. To verify the feasibility of the SERS-based LFA strip platform, an immunoassay of staphylococcal enterotoxin B (SEB) was performed as a model reaction. The limit of detection (LOD) for SEB, as determined with the SERS-based LFA strip, was estimated to be 0.001 ng mL(-1). This value is approximately three orders of magnitude more sensitive than that achieved with the corresponding ELISA-based method. The proposed SERS-based LFA strip sensor shows significant potential for the rapid and sensitive detection of target markers in a simplified manner.