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.

In this review, we briefly summarize the reliability of the density functional theory (DFT)-based methods to accurately predict the main antioxidant properties and the reaction mechanisms involved in the free radical-scavenging reactions of chemical compounds present in food. The analyzed properties are the bond dissociation energies, in particular those involving OH bonds, electron transfer enthalpies, adiabatic ionization potentials, and proton affinities. The reaction mechanisms are hydrogen-atom transfer, proton-coupled electron transfer, radical adduct formation, single electron transfer, sequential electron proton transfer, proton-loss electron transfer, and proton-loss hydrogen-atom transfer. Furthermore, the chelating ability of these compounds and its role in decreasing or inhibiting the oxidative stress induced by Fe(III) and Cu(II) are considered. Comparisons between theoretical and experimental data confirm that modern theoretical tools are not only able to explain controversial experimental facts but also to predict chemical behavior.

Nanotheranostics is one of the biggest scientific breakthroughs in nanomedicine. Most of the currently available diagnosis and therapies are invasive, time-consuming and associated with severe toxic side effects. Nanotheranostics, on the other hand, has the potential to bridge this gap by harnessing the capabilities of nanotechnology and nanomaterials for combined therapeutics and diagnostics with markedly enhanced efficacy. However, nanomaterial applications in nanotheranostics are still in its infancy. This is due to the fact that each disease has a particular microenvironment with well-defined characteristics, which promotes deeper selection criteria of nanomaterials to meet the disease needs. In this review, we have outlined how nanomaterials are designed and tailored for nanotheranostics of cancer, and other diseases such as neurodegenerative, autoimmune (particularly on rheumatoid arthritis) and cardiovascular diseases. The penetrability and retention of a nanomaterial in the biological system, the therapeutic strategy used and the imaging mode selected are some of the aspects discussed for each disease. The specific properties of the nanomaterials in terms of feasibility, physicochemical challenges, progress in clinical trials, its toxicity and their future application on translational medicine are addressed. Our review meticulously and critically examines the applications of nanotheranostics with various nanomaterials, including graphene, across several diseases; offering a broader perspective of this emerging field.

The availability of sensors able to rapidly detect SARS-CoV-2 directly in biological fluids in a single step would allow performing massive diagnostic testing to track in real time and contain the spread of COVID-19. Motivated by this, here, we developed an electrochemical aptamer-based (EAB) sensor able to achieve the rapid, reagentless, and quantitative measurement of the SARS-CoV-2 spike (S) protein. First, we demonstrated the ability of the selected aptamer to undergo a binding-induced conformational change in the presence of its target using fluorescence spectroscopy. Then, we engineered the aptamer to work as a bioreceptor in the EAB platform and we demonstrated its sensitivity and specificity. Finally, to demonstrate the clinical potential of the sensor, we tested it directly in biological fluids (serum and artificial saliva), achieving the rapid (minutes) and single-step detection of the S protein in its clinical range.

Lateral flow assays (LFAs) are currently the most used point-of-care sensors for both diagnostic (e.g., pregnancy test, COVID-19 monitoring) and environmental (e.g., pesticides and bacterial monitoring) applications. Although the core of LFA technology was developed several decades ago, in recent years the integration of novel nanomaterials as signal transducers or receptor immobilization platforms has brought improved analytical capabilities. In this Review, we present how nanomaterial-based LFAs can address the inherent challenges of point-of-care (PoC) diagnostics such as sensitivity enhancement, lowering of detection limits, multiplexing, and quantification of analytes in complex samples. Specifically, we highlight the strategies that can synergistically solve the limitations of current LFAs and that have proven commercial feasibility. Finally, we discuss the barriers toward commercialization and the next generation of LFAs.