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.

BamA is a pivotal protein in cell envelope synthesis and cell division in Deinococcus radiodurans.

The beta-barrel assembly machinery (BAM) is an indispensable complex for protein transportation located at the outer membrane of bacteria. BAM is composed of five subunits (BamA-E) in the model bacterium Escherichia coli. DR_0379 is a BamA homolog in Deinococcus radiodurans, but the other subunits have not been detected in this species. In the present study, deletion of bamA resulted in decreased growth rate and altered morphology of D. radiodurans. ΔbamA cells underwent abnormal cell division, leading to aggregated bacteria of diverse size and shape, and the cell envelope was detached from the cell surface, resulting in reduced resistance to high ionic strength. Oxidative stress resistance was significantly enhanced in the mutant, which may be attributed to increased manganese ion concentration and Mn/Fe ratio. Numerous proteins were released into the medium from ΔbamA cells, including surface layer (S-layer) proteins and various transporters located in the periplasm and outer membrane. These results indicate that BamA affects the synthesis and assembly of the outer membrane and S-layer, and thereby influences material transport and cell division. The findings highlight the special functions of BamA in D. radiodurans, and promote our understanding of the multi-layer structure of the D. radiodurans cell envelope.

Dual-SERS biosensor for one-step detection of microRNAs in exosome and residual plasma of blood samples for diagnosing pancreatic cancer.

MicroRNAs have been proved to be the biomarker for early detection of pancreatic cancer and the precisely quantitation of the MicroRNA-10b in the blood samples even can distinguish pancreatic cancer from chronic pancreatitis (CP) and normal controls (NC). In this study, we developed a DSN-assisted dual-SERS biosensor for microRNA-10b in exosome and residual plasma of blood samples detection based on the Fe3O4 @Ag-DNA-Au@Ag@DTNB (SERS tag) conjugates. In presence of target microRNA, it can hybridized with the complementary DNA probes. DSN enzyme was then added to selectively cleaves the DNA probe of the DNA/microRNA duplex, SERS tags can be released from the Fe3O4@Ag and SERS intensity quenching can be triggered, the released microRNA can enter the cycle to decluster other DNA and SERS tags. Due to the dual-SERS enhancement of the Fe3O4@Ag-SERS tag conjugates and the recycling signal amplification, a detection limit of 1 aM with single-base recognition can be performed by one step. The target microRNA in plasma-derived exosome and residual supernatant plasma of blood samples from pancreatic ductal adenocarcinoma (PDAC), chronic pancreatitis (CP) and normal controls (NC) were directly quantified and significant SERS signal distinction can be found among them. The precise quantitation, one-step and one-pot operation can ensure this assay a promising future for point-of-care cancer diagnosis technology.

Rapid, quantitative and ultra-sensitive detection of cancer biomarker by a SERRS-based lateral flow immunoassay using bovine serum albumin coated Au nanorods.

Early diagnosis of cancer biomarkers is the key to guiding treatments and improving the survival rate of patients. Herein, we report a novel surface-enhanced resonance Raman scattering (SERRS)-based lateral flow immunoassay (LFIA) for quantitative and ultra-sensitive analysis of alpha-fetoprotein (AFP). Gold nanorods (AuNRs) were fabricated to be in resonance with 785 nm laser excitation, that is, the excitation level that can maximize SERRS activity. The AuNRs were modified with 5,5'-dithiobis(2-nitrobenzoic acid), bovine serum albumin (BSA), and AFP detection antibody successively as the SERRS nanotags for the LFIA system. Modification of the BSA layer guaranteed good stability and biocompatibility of the SERRS nanotags in complex samples. The SERRS-LFIA strip for AFP detection showed a low detection limit of 9.2 pg mL-1 and a broad detection range from 10 pg mL-1 to 500 ng mL-1. By comparison, the detection limit of the proposed assay is about 100 and 10 times lower than those of the Au nanoparticle-based SERS-strip and conventional enzyme-linked immunosorbent assay, respectively. Moreover, the potential clinical applications of the assay were evaluated by detecting 10 actual serum samples. Results showed 100% accuracy based on the clinical tests.