Lateral flow assays (LFA) are quick, simple and cheap assays to analyse a variety of samples at the point of care or in the field, making them one of the most widespread biosensors currently available. They have been successfully employed for the detection of a myriad of different targets (ranging from atoms up to whole cells) in all type of samples (including water, blood, foodstuff and environmental samples). Their operation relies on the capillary flow of the sample within a series of sequential pads with different functionalities aiming to generate a signal indicating the absence/presence (and, in some cases, the concentration) of the analyte of interest. In order to have a user-friendly operation, their development requires the optimization of multiple, interconnected parameters that may overwhelm new developers. In this Tutorial we provide the readers with: 1) the basic knowledge to understand the principles governing an LFA and to take informed decisions during lateral flow strip design and fabrication, 2) a roadmap for optimal LFA development independent of the specific application, 3) a step by step example protocol for the assembly and operation of an LF strip for the detection of Human Immunoglobulin G and 4) an extensive troubleshooting section addressing the most frequent issues in designing, assembling and using LFAs.
The COVID-19 pandemic made clear how our society requires quickly available tools to
address emerging healthcare issues. Diagnostic assays and devices are used every day to
screen for COVID-19 positive patients, with the aim to decide the appropriate treatment
and containment measures. In this context, we would have expected to see the use of the
most recent diagnostic technologies worldwide, including the advanced ones such as
nano-biosensors capable to provide faster, more sensitive, cheaper, and high-throughput
results than the standard polymerase chain reaction and lateral flow assays. Here we
discuss why that has not been the case and why all the exciting diagnostic strategies
published on a daily basis in peer-reviewed journals are not yet successful in reaching
the market and being implemented in the clinical practice.
The discovery of NO, CO, and H2S as gasotransmitters and their beneficial role in multiple physiological functions opened an era of research devoted to exogenously deliver them as therapeutic agents. However, the gaseous nature of these molecules demands new forms of administration that enable to control the location, dosage and timing of their delivery. Porous materials are among the most suitable scaffolds to store, deliver and release gasotranmistters due to their high surface area, tunable composition and reactivity. This review highlights the strategies employed to load and release gasotransmitters from different kinds of porous materials, including zeolites, mesoporous silica, metal-organic frameworks and protein assemblies.
Immunoassays are nowadays a crucial tool for diagnostics and drug development. However, they often involve time-consuming procedures and need at least two antibodies in charge of the capture and detection processes, respectively. This study reports a nanocomposite based on graphene oxidecoated nanopaper (GONAP) facilitating an advantageous immunosensing platform using a single antibody and without the need for washing steps. The hydrophilic, porous, and photoluminescence-quenching character of GONAP allows for the adsorption and quenching of photoluminescent quantum dots nanocrystals complexed with antibodies (Ab-QDs), enabling a ready-to-use immunosensing platform. The photoluminescence is recovered upon immunocomplex (antibody-antigen) formation which embraces a series of interactions (hydrogen bonding, electrostatic, hydrophobic, and Van der Waals interactions) that trigger desorption of the antigen-Ab-QD complex from GONAP surface. However, the antigen is then attached onto the GONAP surface by electrostatic interactions leading to a spacer (greater than ≈20 nm) between Ab-QDs and GONAP and thus hindering nonradiative energy transfer. It is demonstrated that this simple-yet highly sensitive-platform represents a virtually universal immunosensing approach by using small-sized and big-sized targets as model analytes, those are, human-IgG protein and Escherichia coli bacteria. In addition, the assay is proved effective in real matrices analysis, including human serum, poultry meat, and river water. GONAP opens the way to conceptually new paper-based devices for immunosensing, which are amenable to point of care applications and automated diagnostics.
Validity of a single antibody-based lateral flow immunoassay depending on graphene oxide for highly sensitive determination of E. coli O157:H7 in minced beef and river water. Food Chemistry, (2019). 297.
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