Selection and characterisation of bioreceptors to develop nanoparticle-based lateral-flow immunoassays in the context of the SARS-CoV-2 outbreak.

This manuscript aims at raising the attention of the scientific community to the need for better characterised bioreceptors for fast development of point-of-care diagnostic devices able to support mass frequency testing. Particularly, we present the difficulties encountered in finding suitable antibodies for the development of a lateral flow assay for detecting the nucleoprotein of SARS-CoV-2.

Nanodiagnostics to Face SARS-CoV-2 and Future Pandemics: From an Idea to the Market and Beyond.

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.

Lateral flow device for water fecal pollution assessment: from troubleshooting of its microfluidics using bioluminescence to colorimetric monitoring of generic Escherichia coli.

Water is the most important ingredient of life. Water fecal pollution threatens water quality worldwide and has direct detrimental effects on human health and the global economy. Nowadays, assessment of water fecal pollution relies on time-consuming techniques that often require well-trained personnel and highly-equipped laboratories. Therefore, faster, cheaper, and easily-used systems are needed to in situ monitor water fecal pollution. Herein, we have developed colorimetric lateral flow strips (LFS) able to detect and quantify Escherichia coli species in tap, river, and sewage water samples as an indicator of fecal pollution. The combination of LFS with a simple water filtration unit and a commercially available colorimetric reader enhanced the assay sensitivity and enabled more accurate quantification of bacteria concentration down to 104 CFU mL-1 in 10 minutes, yielding recovery percentages between 80% and 90% for all water samples analyzed. Overall, this system allows for monitoring and assessing water quality based on E. coli species as a standard microbiological indicator of fecal pollution. Furthermore, we have developed a novel bioluminescent, bacteria-based method to quickly characterize the performance of a great variety of LFS materials. This new method allows evaluating the flow rate of big analytes such as bacteria through the LFS materials, as a suggestive means for selecting the appropriate materials for fabricating LFS targeting big analytes (≈2 µm). As a whole, the proposed approach can accelerate and reduce the costs of water quality monitoring and pave the way for further improvement of fecal pollution detection systems.

The Microbiome Meets Nanotechnology: Opportunities and Challenges in Developing New Diagnostic Devices.

Monitoring of the human microbiome is an emerging area of diagnostics for personalized medicine. Here, the potential of different nanomaterials and nanobiosensing technologies is reviewed for the development of novel diagnostic devices for the detection and measurement of microbiome-related biomarkers. Moreover, the current and future landscape of microbiome-based diagnostics is defined by exploring the advantages and disadvantages of current nanotechnology-based approaches, especially in the context of developing point-of-care (PoC) devices that would meet the international guidelines known as REASSURED (Real-time connectivity; Ease of specimen collection; Affordability; Sensitivity; Specificity; User-friendliness; Rapid & robust operation; Equipment-free; and Deliverability). Finally, the strategies of the latest international scientific consortia working in this field are analyzed, the current microbiome diagnostics market are reported and the principal ethical, legal, and societal issues related to microbiome R&D and innovation are discussed.

Tutorial: design and fabrication of nanoparticle-based lateral-flow immunoassays.

Lateral-flow assays (LFAs) are quick, simple and cheap assays to analyze various 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 throughout a series of sequential pads, each with different functionalities aiming to generate a signal to indicate the absence/presence (and, in some cases, the concentration) of the analyte of interest. 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: (i) the basic knowledge to understand the principles governing an LFA and to take informed decisions during lateral flow strip design and fabrication, (ii) a roadmap for optimal LFA development independent of the specific application, (iii) a step-by-step example procedure for the assembly and operation of an LF strip for the detection of human IgG and (iv) an extensive troubleshooting section addressing the most frequent issues in designing, assembling and using LFAs. By changing only the receptors, the provided example procedure can easily be adapted for cost-efficient detection of a broad variety of targets.