Liposome-based immunostrip for the rapid detection of Salmonella

Nanolabels Prepared by the Entrapment or Self-Assembly of Signaling Molecules for Colorimetric and Fluorescent Immunoassays

Nanomaterials have attracted significant attention as signal reporters for immunoassays. They can directly generate detectable signals or release a large number of signaling elements for readout. Among various nanolabels, nanomaterials composed of multiple signaling molecules have shown great potential in immunoassays. Generally, signaling molecules can be entrapped in nanocontainers or self-assemble into nanostructures for signal amplification. In this review, we summarize the advances of signaling molecules-entrapped or assembled nanomaterials for colorimetric and fluorescence immunoassays. The nanocontainers cover liposomes, polymers, mesoporous silica, metal-organic frameworks (MOFs), various nanosheets, nanoflowers or nanocages, etc. Signaling molecules mainly refer to visible and/or fluorescent organic dyes. The design and application of immunoassays are emphasized from the perspective of nanocontainers, analytes, and analytical performances. In addition, the future challenges and research trends for the preparation of signaling molecules-entrapped or assembled nanolabels are briefly discussed.

Insights into water insecurity in Indigenous communities in Canada: assessing microbial risks and innovative solutions, a multifaceted review

Canada is considered a freshwater-rich country, despite this, several Indigenous reserves struggle with household water insecurity. In fact, some of these communities have lacked access to safe water for almost 30 years. Water quality in Canadian Indigenous reserves is influenced by several factors including source water quality, drinking water treatments applied, water distribution systems, and water storage tanks when piped water is unavailable. The objective of this multifaceted review is to spot the challenges and consequences of inadequate drinking water systems (DWS) and the available technical and microbiological alternatives to address water sanitation coverage in Indigenous reserves of Canada, North America (also known as Turtle Island). A comprehensive literature review was conducted using national web portals from both federal and provincial governments, as well as academic databases to identify the following topics: The status of water insecurity in Indigenous communities across Canada; Microbiological, chemical, and natural causes contributing to water insecurity; Limitations of applying urban-style drinking water systems in Indigenous reserves in Canada and the management of DWS for Indigenous communities in other high-income countries; and the importance of determining the microbiome inhabiting drinking water systems along with the cutting-edge technology available for its analysis. A total of 169 scientific articles matched the inclusion criteria. The major themes discussed include: The status of water insecurity and water advisories in Canada; the risks of pathogenic microorganisms (i.e., Escherichia coli and total coliforms) and other chemicals (i.e., disinfection by-products) found in water storage tanks; the most common technologies available for water treatment including coagulation, high- and low-pressure membrane filtration procedures, ozone, ion exchange, and biological ion exchange and their limitations when applying them in remote Indigenous communities. Furthermore, we reviewed the benefits and drawbacks that high throughput tools such as metagenomics (the study of genomes of microbial communities), culturomics (a high-efficiency culture approach), and microfluidics devices (microminiaturized instruments) and what they could represent for water monitoring in Indigenous reserves. This multifaceted review demonstrates that water insecurity in Canada is a reflection of the institutional structures of marginalization that persist in the country and other parts of Turtle Island. DWS on Indigenous reserves are in urgent need of upgrades. Source water protection, and drinking water monitoring plus a comprehensive design of culturally adapted, and sustainable water services are required. Collaborative efforts between First Nations authorities and federal, provincial, and territorial governments are imperative to ensure equitable access to safe drinking water in Indigenous reserves.

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.

Current Technical Approaches for the Early Detection of Foodborne Pathogens: Challenges and Opportunities

The development of novel and high-tech solutions for rapid, accurate, and non-laborious microbial detection methods is imperative to improve the global food supply. Such solutions have begun to address the need for microbial detection that is faster and more sensitive than existing methodologies (e.g., classic culture enrichment methods). Multiple reviews report the technical functions and structures of conventional microbial detection tools. These tools, used to detect pathogens in food and food homogenates, were designed via qualitative analysis methods. The inherent disadvantage of these analytical methods is the necessity for specimen preparation, which is a time-consuming process. While some literature describes the challenges and opportunities to overcome the technical issues related to food industry legal guidelines, there is a lack of reviews of the current trials to overcome technological limitations related to sample preparation and microbial detection via nano and micro technologies. In this review, we primarily explore current analytical technologies, including metallic and magnetic nanomaterials, optics, electrochemistry, and spectroscopy. These techniques rely on the early detection of pathogens via enhanced analytical sensitivity and specificity. In order to introduce the potential combination and comparative analysis of various advanced methods, we also reference a novel sample preparation protocol that uses microbial concentration and recovery technologies. This technology has the potential to expedite the pre-enrichment step that precedes the detection process.

Rapid electrochemical quantification of Salmonella Pullorum and Salmonella Gallinarum based on glucose oxidase and antibody-modified silica nanoparticles

In this article, a facile and sensitive electrochemical method for quantification of Salmonella Pullorum and Salmonella Gallinarum (S. Pullorum and S. Gallinarum) was established by monitoring glucose consumption with a personal glucose meter (PGM). Antibody-functionalized magnetic nanoparticles (IgG-MNPs) were used to capture and enrich S. Pullorum and S. Gallinarum, and IgG-MNPs-S. Pullorum and IgG-MNPs-S. Gallinarum complexes were magnetically separated from a sample using a permanent magnet. The trace tag was prepared by loading polyclonal antibodies and high-content glucose oxidase on amino-functionalized silica nanoparticles (IgG-SiNPs-GOx). With a sandwich-type immunoassay format, IgG-SiNPs-GOx were added into the above mixture solution and conjugated to the complexes, forming sandwich composites IgG-MNPs/S. Pullorum and S. Gallinarum/IgG-SiNPs-GOx. The above sandwich composites were dispersed in glucose solution. Before and after the hydrolysis of glucose, the concentration of glucose was measured using PGM. Under optimal conditions, a linear relationship between the decrease of glucose concentration and the logarithm of S. Pullorum and S. Gallinarum concentration was obtained in the concentration range from 1.27 × 10² to 1.27 × 10⁵ CFU mL^-1, with a detection limit of 7.2 × 10¹ CFU mL^-1 (S/N = 3). This study provides a portable, low-cost, and quantitative analytical method for bacteria detection; thus, it has a great potential in the prevention of disease caused by S. Pullorum and S. Gallinarum in poultry. Graphical abstract A schematic illustration of the fabrication process of IgG-SiNPs-GOD nanomaterials (A) and IgG-MNPs (B) and experimental procedure of detection of S. Pullorum and S. Gallinarum using GOD-functionalized silica nanospheres as trace tags based on PGM (C).

Functionalized Vesicles by Microfluidic Device

In recent years, lipid vesicles have become popular vehicles for the creation of biosensors. Vesicles can hold reaction components within a selective permeable membrane that provides an ideal environment for membrane protein biosensing elements. The lipid bilayer allows a protein to retain its native structure and function, and the membrane fluidity can allow for conformational changes and physiological interactions with target analytes. Here, we present two methods for the production of giant unilamellar vesicles (GUVs) within a microfluidic device that can be used as the basis for a biosensor. The vesicles are produced from water-in-oil-in-water (W/O/W) double emulsion templates using a nonvolatile oil phase. To create the GUVs, the oil can be removed via extraction with ethanol, or by altering the interfacial tension between the oil and carrier solution causing the oil to retract into a cap on one side of the structure, leaving behind an exposed lipid bilayer. Methods to integrate sensing elements and membrane protein pores onto the vesicles are also introduced in this work.

A review of fluorescent signal-based lateral flow immunochromatographic strips

Fluorescent signal-based lateral flow immunochromatographic strips (FLFICS) have received great expectations since they combine the quantitative sensitivity of fluorescence analysis and the simplicity, rapidness, and portability of a common lateral flow immunochromatographic strip (LFICS).

Advances in nanomaterials and their applications in point of care (POC) devices for the diagnosis of infectious diseases

Nanotechnology has gained much attention over the last decades, as it offers unique opportunities for the advancement of the next generation of sensing tools. Point-of-care (POC) devices for the selective detection of biomolecules using engineered nanoparticles have become a main research thrust in the diagnostic field. This review presents an overview on how the POC-associated nanotechnology, currently applied for the identification of nucleic acids, proteins and antibodies, might be further exploited for the detection of infectious pathogens: although still premature, future integrations of nanoparticles with biological markers that target specific microorganisms will enable timely therapeutic intervention against life-threatening infectious diseases.

Membrane adhesion and the formation of heterogeneities: biology, biophysics, and biotechnology

Membrane adhesion is essential to many vital biological processes. Sites of membrane adhesion are often associated with heterogeneities in the lipid and protein composition of the membrane. These heterogeneities are thought to play functional roles by facilitating interactions between proteins. However, the causal links between membrane adhesion and membrane heterogeneities are not known. Here we survey the state of the field and indicate what we think are understudied areas ripe for development.

Replacing antibodies with aptamers in lateral flow immunoassay

Aptamers have been identified against various targets as a type of chemical or nucleic acid ligand by systematic evolution of ligands by exponential enrichment (SELEX) with high sensitivity and specificity. Aptamers show remarkable advantages over antibodies due to the nucleic acid nature and target-induced structure-switching properties and are widely used to design various fluorescent, electrochemical, or colorimetric biosensors. However, the practical applications of aptamer-based sensing and diagnostics are still lagging behind those of antibody-based tests. Lateral flow immunoassay (LFIA) represents a well established and appropriate technology among rapid assays because of its low cost and user-friendliness. The antibody-based platform is utilized to detect numerous targets, but it is always hampered by the antibody preparation time, antibody stability, and effect of modification on the antibody. Seeking alternatives to antibodies is an area of active research and is of tremendous importance. Aptamers are receiving increasing attention in lateral flow applications because of a number of important potential performance advantages. We speculate that aptamer-based LFIA may be one of the first platforms for commercial use of aptamer-based diagnosis. This review first gives an introduction to aptamer including the selection process SELEX with its focus on aptamer advantages over antibodies, and then depicts LFIA with its focus on aptamer opportunities in LFIA over antibodies. Furthermore, we summarize the recent advances in the development of aptamer-based lateral flow biosensing assays with the aim to provide a general guide for the design of aptamer-based lateral flow biosensing assays.

Development of fluorescence-based liposome immunoassay for detection of Cronobacter muytjensii in pure culture

Cronobacter spp. are important foodborne pathogens that carry a very high risk of infection to neonates as well as immunocompromised individuals. In the present study, fluorescence-based liposome immunoassay was developed as a new sensitive and rapid diagnostic system for detection of Cronobacter muytjensii (C. muytjensii). Liposomes (size, 206 nm) used in this study were made from cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], and sulforhodamine B (SRB). The outer surface of liposome was conjugated with rabbit anti-C. muytjensii IgG in order to develop immunoliposome. The immunoliposome was incubated with C. muytjensii, which was coated on a 96-well plate. Immunoliposomes bound to C. muytjensii were lysed with 30 mM octyl β-D-glucopyranoside, after which the SRB fluorescence signal was measured at an excitation wavelength of 550 nm and emission wavelength of 585 nm. The signal was directly proportional to the amount of bacterial cells in the test sample. The developed fluorescence-based liposome immunoassay was confirmed to be highly specific to C. muytjensii with a detection limit of 6.3 × 10(4) CFU ml(-1) in pure culture as well as sensitive, efficient, and rapid when compared to culture-based methods. Based on its rapid efficiency and low cost, this fluorescence-based liposome immunoassay may be used to develop diagnostic kits for C. muytjensii detection.

New analytical applications of gold nanoparticles as label in antibody based sensors

Gold nanoparticles (AuNPs) with optical and electrochemical distinctiveness as well as biocompatibility characteristics have proven to be powerful tools in nanomedicinal application. This review article discusses recent advances in the application of AuNPs as label in bioanalytical devices, especially electrochemical immunosensors, rapid and point-of-care (PoC) tests. A crucial assessment regarding implementation of different formats of antibodies allowing rapid and sensitive analysis of a range of analytes is also provided in this study. In addition to this, different approaches to minimize antibodies into Fab, scFv or even single-domain antibody fragments like VHHs will be reviewed. Given the high level of target specificity and affinity, such biomolecules are considered to be excellent elements for on-site or PoC analysis.

Atomic force microscopy: a tool to study the structure, dynamics and stability of liposomal drug delivery systems

Much work has been done during the past few decades to develop effective drug delivery systems (DDS), many of which are based on nanotechnology science. Liposomes are the most attractive lipid vesicles for drug delivery. The multifunctional properties of liposomes have a key role in modifying the bioavailability profile of a therapeutic agent. Different analytical techniques can be used to describe liposomes, not least applied scanning probe microscopy (SPM) techniques. Atomic force microscopy (AFM) seems to be one of the most effectively applied SPM techniques. This review article outlines the applications of AFM in evaluating the physical characteristics and stability of liposomal DDSs. Other well-known microscopy techniques used in evaluating liposome physical characteristics are also mentioned, and the contribution of AFM to evaluating liposomal stability is discussed. Among the advantages of AFM in examining the physicochemical properties of liposomal DDSs is its ability to provide morphological and metrology information on liposome properties. AFM thus appears to be a promising tool in technological characterization of liposomal DDSs.

Point-of-care testing of proteins

Point-of-care testing (POCT) is a fast developing area in clinical diagnostics that is considered to be one of the main driving forces for the future in vitro diagnostic market. POCT means decentralized testing at the site of patient care. The most important POCT devices are handheld blood glucose sensors. In some of these sensors, after the application of less than 1 microl whole blood, the results are displayed in less than 10 s. For protein determination, the most commonly used devices are based on lateral flow technology. Although these devices are convenient to use, the results are often only qualitative or semiquantitative. The review will illuminate some of the current methods employed in POCT for proteins and will discuss the outlook for techniques (e.g., electrochemical immunosensors) that could have a great impact on future POCT of proteins.

Lateral flow (immuno)assay: its strengths, weaknesses, opportunities and threats. A literature survey

Lateral flow (immuno)assays are currently used for qualitative, semiquantitative and to some extent quantitative monitoring in resource-poor or non-laboratory environments. Applications include tests on pathogens, drugs, hormones and metabolites in biomedical, phytosanitary, veterinary, feed/food and environmental settings. We describe principles of current formats, applications, limitations and perspectives for quantitative monitoring. We illustrate the potentials and limitations of analysis with lateral flow (immuno)assays using a literature survey and a SWOT analysis (acronym for "strengths, weaknesses, opportunities, threats"). Articles referred to in this survey were searched for on MEDLINE, Scopus and in references of reviewed papers. Search terms included "immunochromatography", "sol particle immunoassay", "lateral flow immunoassay" and "dipstick assay".