Passive sweat collection and colorimetric analysis.

Pharmacology and optogenetics are widely used in neuroscience research to study the central and peripheral nervous systems. While both approaches allow for sophisticated studies of neural circuitry, continued advances are, in part, hampered by technology limitations associated with requirements for physical tethers that connect external equipment to rigid probes inserted into delicate regions of the brain. The results can lead to tissue damage and alterations in behavioral tasks and natural movements, with additional difficulties in use for studies that involve social interactions and/or motions in complex 3-dimensional environments. These disadvantages are particularly pronounced in research that demands combined optogenetic and pharmacological functions in a single experiment. Here, we present a lightweight, wireless, battery-free injectable microsystem that combines soft microfluidic and microscale inorganic light-emitting diode probes for programmable pharmacology and optogenetics, designed to offer the features of drug refillability and adjustable flow rates, together with programmable control over the temporal profiles. The technology has potential for large-scale manufacturing and broad distribution to the neuroscience community, with capabilities in targeting specific neuronal populations in freely moving animals. In addition, the same platform can easily be adapted for a wide range of other types of passive or active electronic functions, including electrical stimulation.

Cas13 orthologs, the single effectors of the Class 2 type VI clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas) systems, are RNA-guided ribonucleases 1 . The CRISPR RNAs (crRNAs) of this family contain a direct repeat stem loop that interacts with the Cas13 protein to form an RNase-inactive binary complex and a spacer sequence that base pairs with the target RNA 2 . The resulting Cas13-crRNA-target ternary complex undergoes a large-scale conformational change in which two higher eukaryotes and prokaryotes nucleotide-binding (HEPN) domains move toward each other to form a single catalytic pocket to cleave the target RNA. Intriguingly, this catalytic pocket localized on the outer surface of the target-activated Cas13 complex can non-specifically cleave any surrounding RNA molecules in a characteristic 'collateral effect' 2 . This target-triggered collateral activity, originally an immune defense mechanism intended to induce host dormancy and prevent the propagation of invading phages, has been rapidly developed for in vitro detection of nucleic acids 3 . For example, the Cas13-crRNA surveillance complex is activated upon target recognition and performs collateral cleavage of nearby dye-quencher pairs linked by single-stranded RNA (ssRNA) 3,4 to rapidly generate measurable fluorescent or colorimetric signals [3][4][5] .The Leptotrichia wadei (Lwa)Cas13a has been widely used in nucleic-acid-based diagnostics. Coupling LwaCas13a collateral activity to target preamplification, the specific high-sensitivity enzymatic reporter unlocking (SHERLOCK) platform has detected attomolar levels of viral RNA and other endogenous RNA targets 3 . Combining LwaCas13a with auxiliary Csm6 endoribonuclease, SHERLOCKv2 shortened the detection time for a Dengue

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) systems have recently received notable attention for their applications in nucleic acid detection. Despite many attempts, the majority of current CRISPR-based biosensors in infectious respiratory disease diagnostic applications still require target preamplifications. This study reports a new biosensor for amplification-free nucleic acid detection via harnessing the trans-cleavage mechanism of Cas13a and ultrasensitive graphene field-effect transistors (gFETs). CRISPR Cas13a-gFET achieves the detection of SARS-CoV-2 and respiratory syncytial virus (RSV) genome down to 1 attomolar without target preamplifications. Additionally, we validate the detection performance using clinical SARS-CoV-2 samples, including those with low viral loads (Ct value > 30). Overall, these findings establish our CRISPR Cas13a-gFET among the most sensitive amplification-free nucleic acid diagnostic platforms to date.

Electrolytes play a pivotal role in regulating cardiovascular functions, hydration, and muscle activation. The current standards for monitoring electrolytes involve periodic sampling of blood and measurements using laboratory techniques, which are often uncomfortable/inconvenient to the subjects and add considerable expense to the management of their underlying disease conditions. The wide range of electrolytes in skin interstitial fluids (ISFs) and their correlations with those in plasma create exciting opportunities for applications such as electrolyte and circadian metabolism monitoring. However, it has been challenging to monitor these electrolytes in the skin ISFs. In this study, we report a minimally invasive microneedle-based potentiometric sensing system for multiplexed and continuous monitoring of Na+ and K+ in the skin ISFs. The potentiometric sensing system consists of a miniaturized stainless-steel hollow microneedle to prevent sensor delamination and a set of modified microneedle electrodes for multiplex monitoring. We demonstrate the measurement of Na+ and K+ in artificial ISFs with a fast response time, excellent reversibility and repeatability, adequate selectivity, and negligible potential interferences upon the addition of a physiologically relevant concentration of metabolites, dietary biomarkers, and nutrients. In addition, the sensor maintains the sensitivity after multiple insertions into the chicken skin model. Furthermore, the measurements in artificial ISFs using calibrated sensors confirm the accurate measurements of physiological electrolytes in artificial ISFs. Finally, the skin-mimicking phantom gel and chicken skin model experiments demonstrate the sensor’s potential for minimally invasive monitoring of electrolytes in skin ISFs. The developed sensor platform can be adapted for a wide range of other applications, including real-time monitoring of nutrients, metabolites, and proteins.