Developing a novel immunochromatographic test strip with gold magnetic bifunctional nanobeads (GMBN) for efficient detection of Salmonella choleraesuis in milk

Double-enhanced lateral flow immunoassay for potato virus X based on a combination of magnetic and gold nanoparticles

This study presents the joint use of magnetic nanoparticles (MNPs) and gold nanoparticles (GNPs) for double enhancement in a lateral flow immunoassay (LFIA). The study realizes two types of enhancement: (1) increasing the concentration of analytes in the samples using conjugates of MNPs with specific antibodies and (2) increasing the visibility of the label through MNP aggregation caused by GNPs. The proposed strategy was implemented using a LFIA for potato virus X (PVX), a significant potato pathogen. MNPs conjugated with biotinylated antibodies specific to PVX and GNPs conjugated with streptavidin were synthesized and characterized. The LFIAs with and without the proposed enhancements were compared. The double-enhanced LFIA achieved the highest sensitivity, equal to 0.25 ng mL^-1 and 32 times more sensitivity than the non-enhanced LFIA (detection limit: 8 ng mL^-1). LFIAs using one of the types of amplification (magnetic concentration without GNPs-causing aggregation or MNP aggregation without the concentration stage) showed intermediate levels of sensitivity. The double-enhanced LFIA was successfully used for PVX detection in potato leaves. The results for PVX detection in the infected plants were similar for the double-enhanced LFIA developed and the conventional LFIA based on the GNP conjugates; however, the new system provided significant coloring enhancement. This study confirmed that a simple combination of MNPs and GNPs has great potential for high-sensitivity detection and could possibly be adopted for LFIAs of other compounds.

Recent advances in nanoparticle-based lateral flow immunoassay as a point-of-care diagnostic tool for infectious agents and diseases

Recent advances in lateral flow immunoassay-based devices as a point-of-care analytical tool for the detection of infectious diseases are reviewed.

Nanozyme-Mediated Dual Immunoassay Integrated with Smartphone for Use in Simultaneous Detection of Pathogens

Nanozymes are an excellent class of optical reporters for the development of sensitive biosensors for widespread applications. In this study, mesoporous core-shell palladium@platinum (Pd@Pt) nanoparticles were synthesized and then applied as signal amplifier in a dual lateral flow immunoassay (LFIA) and integrated with a smartphone-based device for use in simultaneous detection of Salmonella Enteritidis and Escherichia coli O157:H7. After optimization, the limit of detections were calculated to be ∼20 cfu/mL for S. Enteritidis and ∼34 cfu/mL for E. coli O157:H7, respectively. The greatly improved sensitivity was contributed by the peroxidase-like catalytic activity of the Pd@Pt nanoparticles for signal enhancement and the parallel design of dual detection for eliminating the cross-interference. The estimated recoveries of the dual LFIA range from 91.44 to 117.00%, which indicated that the developed method is capable of detecting live bacteria in food samples. This approach provides an attractive platform for S. Enteritidis and E. coli O157:H7 detection using a smartphone-based device as the sole piece of equipment, indicating great promise for foodborne pathogen analysis or in-field food safety tracking.

Development of a competitive immunochromatographic assay for the sensitive detection of amantadine in chicken muscle

Amantadine (AMD) is a prohibitive veterinary medicine in the entire world. In this study, a sensitive colloidal gold immunochromatographic assay (CGICA) was established for the rapid semi-quantitative detection of AMD in chicken muscle. Under optimal conditions, the detection results were obtained in 12min with a limit of detection for 1.80ng/mL. CGICA presented a good linear range from 2.5ng/mL to 25ng/mL, with only 11.5% cross-reactivity with rimantadine. The recovery rates for the fortified samples were ranged from 81% to 120%. The coefficient of variation of the intra-assay and inter-assay was less than 15%. The accuracy of CGICA was confirmed by systematically comparing the result of the proposed method with enzyme-linked immunosorbent assay and ultra-high-performance liquid chromatography-tandem mass spectrometry. Given the advantages of its simplicity, convenience, and speediness, the proposed CGICA is suitable for the on-site rapid detection of AMD in chicken muscle.

Highly sensitive and selective lateral flow immunoassay based on magnetic nanoparticles for quantitative detection of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is an important biomarker in cancer diagnosis. Here, we present an efficient, selective lateral-flow immunoassay (LFIA) based on magnetic nanoparticles (MNPs) for in situ sensitive and accurate point-of-care detection of CEA. Signal amplification mechanism involved linking of detection MNPs with signal MNPs through biotin-modified single-stranded DNA (ssDNA) and streptavidin. To verify the effectiveness of this modified LFIA system, the sensitivity and specificity were evaluated. Sensitivity evaluation showed a broad detection range of 0.25-1000ng/ml for CEA protein by the modified LFIA, and the limit of detection (LOD) of the modified LFIA was 0.25ng/ml, thus producing significant increase in detection threshold compared with the traditional LFIA. The modified LFIA could selectively recognize CEA in presence of several interfering proteins. In addition, this newly developed assay was applied for quantitative detection of CEA in human serum specimens collected from 10 randomly selected patients. The modified LFIA system detected minimum 0.27ng/ml of CEA concentration in serum samples. The results were consistent with the clinical data obtained using commercial electrochemiluminescence immunoassay (ECLIA) (p<0.01). In conclusion, the MNPs based LFIA system not only demonstrated enhanced signal to noise ratio, it also detected CEA with higher sensitivity and selectivity, and thus has great potential to be commercially applied as a sensitive tumor marker filtration system.