Owing to their diverse properties, fluorescent carbon dots (CDs) have attracted more attention and present enormous potential in development of sensors, bioimaging, drug delivery, microfluidics, photodynamic therapy, light emitting diode, and so forth. Herein, a multifunctional sensing platform based on bright yellow fluorescent CDs (Y-CDs) was designed for the label-free detection of fluoroquinolones (FQs) and histidine (His). The Y-CDs with superior optical and biological merits including high chemical stability, good biocompatibility, and low cytotoxicity were simply synthesized via one-step hydrothermal treatment of o-phenylenediamine (o-PD) and 4-aminobutyric acid (GABA). The Y-CDs can be utilized to directly monitor the amount of FQs based on fluorescence static quenching owing to the specific interaction between FQs and Y-CDs. Then, the fluorescence of this system can be effectively recovered upon addition of His. The multifunctional sensing platform exhibited high sensitivity and selectivity toward three kinds of FQs and His with low detection limits of 17–67 and 35 nM, respectively. Benefiting from these outstanding characters, the Y-CDs were successfully employed for trace detection of FQs in real samples such as antibiotic tablets and milk products. Furthermore, the probe was also extended to cellular imaging. All of the above prove that this multifunctional sensing platform presents great prospect in multiple applications such as biosensing, biomedicine, disease diagnosis, and environmental monitoring.

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SARS-CoV-2, the virus underlying COVID-19, has now been recognized to cause multiorgan disease with a systemic effect on the host. To effectively combat SARS-CoV-2 and the subsequent development of COVID-19, it is critical to detect, monitor, and model viral pathogenesis. In this review, we discuss recent advancements in microfluidics, organ-on-a-chip, and human stem cell–derived models to study SARS-CoV-2 infection in the physiological organ microenvironment, together with their limitations. Microfluidic-based detection methods have greatly enhanced the rapidity, accessibility, and sensitivity of viral detection from patient samples. Engineered organ-on-a-chip models that recapitulate in vivo physiology have been developed for many organ systems to study viral pathology. Human stem cell–derived models have been utilized not only to model viral tropism and pathogenesis in a physiologically relevant context but also to screen for effective therapeutic compounds. The combination of all these platforms, along with future advancements, may aid to identify potential targets and develop novel strategies to counteract COVID-19 pathogenesis.

Graphical abstract Extracellular ATP as a purinergic signaling molecule, together with ATP receptor, are playing an important role in tumor growth, therapy resistance, and host immunity suppression. Meanwhile ATP is a crucial indicator for cellular energy status and viability, thus a vital variable for tissue regeneration and in vitro tissue engineering. Most recent studies on COVID-19 virus suggest infection caused ATP deficit and release as a major characterization at the early stage of the disease and major causes for disease complications. Thus, imaging ATP molecule in both cellular and extracellular contexts has many applications in biology, engineering, and clinics. A sensitive and selective fluorescence “signal-on” probe for ATP detection was constructed, based on the base recognition between a black hole quencher (BHQ)-labeled aptamer oligonucleotide and a fluorophore (Cy5)-labeled reporter flare. The probe was able to detect ATP in solution with single digit µM detection limit. With the assistance of lipofectamine, this probe efficiently entered and shined in the model cells U2OS within 3 h. Further application of the probe in specific scenery, cardio-tissue engineering, was also tested where the ATP aptamer complex was able to sense cellular ATP status in a semi-quantitative manner, representing a novel approach for selection of functional cardiomyocytes for tissue engineering. At last a slight change in probe configuration in which a flexible intermolecular A14 linker was introduced granted regeneration capability. These data support the application of this probe in multiple circumstances where ATP measurement or imaging is on demand. Supplementary Information The online version contains supplementary material available at 10.1007/s00604-021-05012-8.