A novel ratiometric fluorescent approach for the modulation of the dynamic range of lateral flow immunoassays

The majority of lateral flow assays (LFAs) use single-color optical labels to provide a qualitative naked-eye detection, however this detection method displays two important limitations. First, the use of a single-color label makes the LFA prone to results misinterpretation. Second, it does not allow the precise modulation of the sensitivity and dynamic range of the test. To overcome these limitations, a ratiometric approach is developed. In particular, using anti-HIgG functionalized red-fluorescent quantum dots on the conjugate pad (as target dependent labels) and blue-fluorescent nanoparticles fixed on the test line (as target independent reporters), it is possible to generate a wide color palette (blue, purple, pink, red) on the test line. It is believed that this strategy will facilitate the development of LFAs by easily adjusting their analytical properties to the needs required by the specific application

Optical smartphone-based sensing: diagnostic of biomarkers

Biomarkers are nucleic acids, peptides, proteins, lipids metabolites, or other small molecules in human tissues or biological fluids whose accurate detection contributes to the prediction and determination of diseases and their status. In recent years, platforms that allow the detection of important biomarkers at the point-of-care (PoC) are moving the field of diagnostics towards personalized medicine. In order to comply with the REASSURED criteria stated by the WHO, the most efficient solution is to integrate PoC devices with smartphones. Without a doubt the smartphone camera is a “smart detector,” and almost all the optical-based methods have been integrated, including absorbance, fluorescence, microscopic bio-imaging, surface plasmon resonance, chemiluminescence, bioluminescence, and photoluminescence. In this chapter, we explain how smartphones can be used as smart detectors in diagnostic devices and we will provide an overview of recent developments of smartphone-based optical PoC devices

Attomolar analyte sensing techniques (AttoSens): A review on a decade of progress on chemical and biosensing nanoplatforms

Detecting the ultra-low abundance of analytes in real-life samples, such as biological fluids, water, soil, and food, requires the design and development of high-performance biosensing modalities. The breakthrough efforts from the scientific community have led to the realization of sensing technologies that measure the analyte's ultra-trace level, with relevant sensitivity, selectivity, response time, and sampling efficiency, referred to as Attomolar Analyte Sensing Techniques (AttoSens) in this review. In an AttoSens platform, 1 aM detection corresponds to the quantification of 60 target analyte molecules in 100 μL of sample volume. Herein, we review the approaches listed for various sensor probe design, and their sensing strategies that paved the way for the detection of attomolar (aM: 10-18 M) concentration of analytes. A summary of the technological advances made by the diverse AttoSens trends from the past decade is presented. This journal isSPU is grateful to the Science and Engineering Research Board – Department of Science and Technology (SERB – DST), India (Grant no. PDF/2018/000079) for the National Postdoctoral Fellowship. VVRS and RD gratefully acknowledge the financial support by the Department of Science and Technology (DST), India. VVRS acknowledges the funding from Indo-German Science and Technology Centre (IGSTC), New Delhi under the DEMO-Multi-WAP project (IGSTC/Call 2015-Extension/Multi-WAP/09/2019-20). ICN2 is funded by the CERCA programme, Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, grant no. SEV-2017-0706). The authors are grateful to Ms Volga Muthukumar, Mr Divagar Murugan, Ms Kuzhandai Shamlee James and Mr Rohan. S for their help in the manuscript preparation