2D Film-Like Magnetic SERS Tag with Enhanced Capture and Detection Abilities for Immunochromatographic Diagnosis of Multiple Bacteria.

Here, a multiplex surface-enhanced Raman scattering (SERS)-immunochromatography (ICA) platform is presented using a graphene oxide (GO)-based film-like magnetic tag (GFe-DAu-D/M) that effectively captures and detects multiple bacteria in complex specimens. The 2D GFe-DAu-D/M tag with universal bacterial capture ability is fabricated through the layer-by-layer assembly of one layer of small Fe3O4 nanoparticles (NPs) and two layers of 30 nm AuNPs with a 0.5 nm built-in nanogap on monolayer GO nanosheets followed by co-modification with 4-mercaptophenylboronic acid (MPBA) and 5,5'-dithiobis-(2-nitrobenzoic acid).The GFe-DAu-D/M enabled the rapid enrichment of multiple bacteria by MPBA and quantitative analysis of target bacteria on test lines by specific antibodies, thus achieving multiple signal amplification of magnetic enrichment effect and multilayer dense hotspots and eliminating matrix interference in real-world applications. The developed technology can directly and simultaneously diagnose three major pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella typhimurium) with detection limits down to the level of 10 cells mL-1. The good performance of the proposed method in the detection of real urinary tract infection specimens is also demonstrated, suggesting the great potential of the GFe-DAu-D/M-ICA platform for the highly sensitive monitoring of bacterial infections or contamination.

Analysis of Risk Factors for Urinary Tract Infections in Pregnant Women: A Retrospective Study.

OBJECTIVE: Urinary tract infections (UTIs) are the most common bacterial infection during pregnancy. This study aimed to investigate the risk factors of UTI during pregnancy. METHODS: In this study, pregnant women who underwent prenatal examination in our hospital from October 2019 to October 2023 were divided into UTI group and non-UTI group in accordance with whether or not they had a UTI. The general data, clinical data and laboratory indicators of the participants were collected. Multivariate logistic regression was used to analyse the influencing factors of UTI in pregnant women, and the results were shown with odds ratio (OR) and 95% confidence interval (95% CI). RESULTS: A total of 600 pregnant women were included in the study. The results found that 56 women (9.33%) had a combined UTI. The results of midstream urinary bacterial culture in the UTI group showed that Gram-negative bacteria accounted for 60.71% of all detected pathogenic bacteria, and Escherichia coli and Staphylococcus aureus were common strains, accounting for 46.43% and 23.21%, respectively. The proportions of patients in the UTI group who were ≥35 years old, had a high school education or below, had a history of abortion, had gestational diabetes, had ≥three vaginal and anal examinations, had a history of UTI and had urinary tract stones were significantly higher than the non-UTI group (p < 0.05). Multivariate logistic regression analysis showed that age ≥35 years (OR = 9.127; 95% CI: 4.668-17.810; p < 0.001), educational level of high school or lower (OR = 4.184; 95% CI: 2.448-7.160; p < 0.001), gestational diabetes (OR = 3.494; 95% CI: 1.789-6.803; p < 0.001), UTI history (OR = 2.074; 95% CI: 1.114-3.834; p < 0.001) and haemoglobin (Hb) <100 g/L (OR = 8.022; 95% CI: 4.532-14.325; p < 0.001) are risk factors for UTI in pregnant women. CONCLUSIONS: The common pathogenic bacteria of pregnant women with UTI are mainly Gram-negative bacteria. Older pregnant women, low educational level, gestational diabetes mellitus, history of UTI and anaemia may be risk factors for UTI in pregnant women.

3D Film-Like Nanozyme with a Synergistic Amplification Effect for the Ultrasensitive Immunochromatographic Detection of Respiratory Viruses.

Greatly improving the sensitivity and detection range of lateral flow immunoassays (LFAs) by at least 100 times without using additional instruments remains challenging. Herein, we develop a three-dimensional (3D) film-like nanozyme (GO-Pt30-AuPt5) by ordered assembly of one layer of 30 nm Pt nanoparticles (NPs) and one layer of small Au@Pt satellites (5 nm) onto a two-dimensional (2D) graphene oxide (GO) nanofilm, in which GO greatly increased the interface area and stability of the nanozyme whereas Pt and Au@Pt NPs synergistically enhanced colorimetric/catalytic activities. The grafting of outer Au@Pt satellites converted the 2D nanofilm into a 3D flexible nanozyme with numerous catalytic sites for enzymatic deposition signal amplification and binding sites for target capture. The introduction of GO-Pt30-AuPt5 into multiplex LFA achieved the ultrasensitive and simultaneous detection of two important respiratory viruses with sensitivity of 1 pg/mL level, which was about 100 times higher than that without signal enrichment and at least 20 and 1900 times higher than those of traditional enzyme-linked immunosorbent assay and AuNP-based LFA, respectively. The clinical utility of the proposed assay was validated through the diagnosis of 49 real clinical respiratory tract specimens. Our proposed LFA shows great potential for the ultrasensitive screening of pathogens in the field.

Phenylboronic Acid-Modified Membrane-Like Magnetic Quantum Dots Enable the Ultrasensitive and Broad-Spectrum Detection of Viruses by Lateral Flow Immunoassay.

Although lateral flow immunochromatographic assay (LFIA) is an effective point-of-care testing technology, it still cannot achieve broad-spectrum and ultrasensitive detection of viruses. Herein, we propose a multiplex LFIA platform using a two-dimensional graphene oxide (GO)-based magnetic fluorescent nanofilm (GF@DQD) as a multifunctional probe and 4-aminophenylboronic acid (APBA) as a broad-spectrum recognition molecule for viral glycoprotein detection. GF@DQD-APBA with enhanced magnetic/fluorescence properties and universal capture ability for multiple viruses was easily prepared through the electrostatic adsorption of one layer of density-controlled Fe3O4 nanoparticles (NPs) and thousands of small CdSe/ZnS-MPA quantum dots (QDs) on a monolayer GO sheet followed by chemical coupling with APBA on the QD surface. The GF@DQD-APBA probe enabled the universal capture and specific determination of different target viruses on the test strip through an arbitrary combination with the antibody-modified LFIA strip, thus greatly improving detection efficiency and reducing the cost and difficulty of multiplex LFIA for viruses. The proposed technique can simultaneously and sensitively diagnose three newly emerged viruses within 20 min with detection limits down to the pg/mL level. The excellent practicability of GF@DQD-APBA-LFIA was also demonstrated in the detection of 34 clinical specimens positive for SARS-CoV-2, revealing its potential for epidemic control and on-site viral detection.

Electrostatic Adsorption of Dense AuNPs onto Silica Core as High-Performance SERS Tag for Sensitive Immunochromatographic Detection of Streptococcus pneumoniae.

Streptococcus pneumoniae (S. pneumoniae) is a prominent pathogen of bacterial pneumonia and its rapid and sensitive detection in complex biological samples remains a challenge. Here, we developed a simple but effective immunochromatographic assay (ICA) based on silica-Au core-satellite (SiO2@20Au) SERS tags to sensitively and quantitatively detect S. pneumoniae. The high-performance SiO2@20Au tags with superior stability and SERS activity were prepared by one-step electrostatic adsorption of dense 20 nm AuNPs onto 180 nm SiO2 core and introduced into the ICA method to ensure the high sensitivity and accuracy of the assay. The detection limit of the proposed SERS-ICA reached 46 cells/mL for S. pneumoniae and was 100-fold more sensitive than the traditional AuNPs-based colorimetric ICA method. Further, considering its good stability, specificity, reproducibility, and easy operation, the SiO2@20Au-SERS-ICA developed here has great potential to meet the demands of on-site and accurate detection of respiratory pathogens.

Surveillance of emerging infectious diseases for biosecurity.

Emerging infectious diseases, such as COVID-19, continue to pose significant threats to human beings and their surroundings. In addition, biological warfare, bioterrorism, biological accidents, and harmful consequences arising from dual-use biotechnology also pose a challenge for global biosecurity. Improving the early surveillance capabilities is necessary for building a common biosecurity shield for the global community of health for all. Furthermore, surveillance could provide early warning and situational awareness of biosecurity risks. However, current surveillance systems face enormous challenges, including technical shortages, fragmented management, and limited international cooperation. Detecting emerging biological risks caused by unknown or novel pathogens is of particular concern. Surveillance systems must be enhanced to effectively mitigate biosecurity risks. Thus, a global strategy of meaningful cooperation based on efficient integration of surveillance at all levels, including interdisciplinary integration of techniques and interdepartmental integration for effective management, is urgently needed. In this paper, we review the biosecurity risks by analyzing potential factors at all levels globally. In addition to describing biosecurity risks and their impact on global security, we also focus on analyzing the challenges to traditional surveillance and propose suggestions on how to integrate current technologies and resources to conduct effective global surveillance.

Ultrasensitive multichannel immunochromatographic assay for rapid detection of foodborne bacteria based on two-dimensional film-like SERS labels.

Rapid and sensitive detection of multiple foodborne bacteria without DNA amplification is still challenging. Here, we proposed an immunochromatographic assay (ICA) with multiplex analysis ability and high sensitivity for direct detection of bacteria in real food samples, based on an improved surface-enhanced Raman scattering (SERS) sensing strategy. Multifunctional Au shell-coated graphene oxide nanosheets (GO@Au) were fabricated and for the first time introduced into the ICA system as a two-dimensional film-like SERS label, which possessed huge surface area, excellent stability, and superior SERS activity. Different from the conventional spherical nanotags, the antibody-conjugated GO@Au nanosheet effectively and rapidly adhered to bacterial cells, improved the dispersibility of bacteria-nanolabel complexes on the ICA strips, and provided numerous stable hotspots for SERS signal enhancement. The combination of GO@Au labels and the ICA system achieved the multiplex and ultrasensitive determination of three major foodborne pathogens, namely, Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella typhimurium, in a single test, with low detection limits (8, 10, and 10 cells/mL) and short detection time (20 min). The proposed biosensor demonstrated high stability and good accuracy in various food samples and is thus a promising tool for the rapid identification of bacteria.

Dual-signal lateral flow assay using vancomycin-modified nanotags for rapid and sensitive detection of Staphylococcus aureus.

This paper reports a colorimetric-fluorescent dual-signal lateral flow assay (LFA) based on vancomycin (Van)-modified SiO2-Au-QD tags for sensitive and quantitative detection of Staphylococcus aureus (S. aureus). The combination of high-performance Van-tags and detection antibodies integrated into the LFA system produced assays with high sensitivity and specificity. The visualization limit of the colorimetric signal and the detection limit of the fluorescence signal of the proposed method for S. aureus can reach 104 and 100 cells mL-1, respectively.

Rapid SERS identification of methicillin-susceptible and methicillin-resistant Staphylococcus aureus via aptamer recognition and deep learning.

Here, we report a label-free surface-enhanced Raman scattering (SERS) method for the rapid and accurate identification of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) based on aptamer-guided AgNP enhancement and convolutional neural network (CNN) classification. Sixty clinical isolates of Staphylococcus aureus (S. aureus), comprising 30 strains of MSSA and 30 strains of MRSA were used to build the CNN classification model. The developed method exhibited 100% identification accuracy for MSSA and MRSA, and is thus a promising tool for the rapid detection of drug-sensitive and drug-resistant bacterial strains.

Layer-by-layer assembly of magnetic-core dual quantum dot-shell nanocomposites for fluorescence lateral flow detection of bacteria.

Lateral flow immunoassay (LFA) strips are extensively used for rapid tests of various biochemical molecules, but these strips still have some limitations in bacterial detection due to their low sensitivity and poor stability in complex samples. In this study, we reported a highly sensitive and quantitative fluorescent LFA strip for bacterial detection by using novel magnetic-core@dual quantum dot (QD)-shell nanoparticles (Fe3O4@DQDs) as multifunctional fluorescent labels. The Fe3O4@DQDs were prepared through a polyethyleneimine (PEI)-mediated layer-by-layer (LBL) assembly method, and they possess monodispersity, high magnetic responsiveness, good stability, and superior fluorescence properties. Based on these merits, the Fe3O4@DQDs were used to capture and enrich bacteria from complex samples and then used as advanced fluorescent labels of LFA strips for the quantitative detection of bacteria. Under optimal conditions, the assay ultra-sensitively detected Streptococcus pneumoniae with a low limit of detection of 8 cells per mL and a wide dynamic linear range of 10 cells per mL to 107 cells per mL. Systematic comparison revealed that the fluorescence detection limit of the Fe3O4@DQD-based strip was 55 and 1000 times higher than those of Fe3O4-core@QD-shell nanocomposite (Fe3O4-QD)-based and conventional QD microsphere-based strips, respectively. The proposed method also exhibited high specificity and selectivity for biological samples (human whole blood and sputum) and is thus a promising tool for real bacterial sample testing.