A sensor capable of continuously measuring specific molecules in the bloodstream in vivo would give clinicians a valuable window into patients’ health and their response to therapeutics. Such technology would enable truly personalized medicine, wherein therapeutic agents could be tailored with optimal doses for each patient to maximize efficacy and minimize side effects. Unfortunately, continuous, real-time measurement is currently only possible for a handful of targets, such as glucose, lactose, and oxygen, and the few existing platforms for continuous measurement are not generalizable for the monitoring of other analytes, such as small-molecule therapeutics. In response, we have developed a real-time biosensor capable of continuously tracking a wide range of circulating drugs in living subjects. Our microfluidic electrochemical detector for in vivo continuous monitoring (MEDIC) requires no exogenous reagents, operates at room temperature, and can be reconfigured to measure different target molecules by exchanging probes in a modular manner. To demonstrate the system's versatility, we measured therapeutic in vivo concentrations of doxorubicin (a chemotherapeutic) and kanamycin (an antibiotic) in live rats and in human whole blood for several hours with high sensitivity and specificity at sub-minute temporal resolution. Importantly, we show that MEDIC can also obtain pharmacokineticparameters for individual animals in real-time. Accordingly, just as continuous glucose monitoring technology is currently revolutionizing diabetes care, we believe MEDIC could be a powerful enabler for personalized medicine by ensuring delivery of optimal drug doses for individual patients based on direct detection of physiological parameters.

The development of a biosensor system capable of continuous, real-time measurement of smallmolecule analytes directly in complex, unprocessed aqueous samples has been a significant challenge, and successful implementation has been achieved for only a limited number of targets. Towards a general solution to this problem, we report here the Microfluidic Electrochemical Aptamer-based Sensor (MECAS) chip wherein we integrate target-specific DNA aptamers that fold, and thus generate an electrochemical signal, in response to the analyte with a microfluidic detection system. As a model, we demonstrate the continuous, real-time (~1 minute time resolution) detection of the small molecule drug cocaine at near physiological, low micromolar concentrations directly in undiluted, otherwise unmodified blood serum. We believe our approach of integrating folding-based electrochemical sensors with miniaturized detection systems may lay the ground work for the realtime, point-of-care detection of a wide variety of molecular targets.The capability to perform in situ, continuous, real-time monitoring of specific small molecules in complex, unprocessed aqueous samples is important for a broad spectrum of applications ranging from medical diagnostics to environmental monitoring. 1 However, successful implementation of such strategies has proven elusive, and thus far has been achieved for only a few, specialized targets (e.g., neurotransmitters, such as 5-hydroxytryptamine, 2 hydrogen ions 3 and glucose 4 ). The challenge of real-time sensing arises from the fact that, to meet this demanding application, a sensor needs not only be sensitive, stable and selective enough to deploy directly in complex sample matrices, but it also needs to be reagentless, regenerable and able to respond rapidly relative to the timescale with which the target concentration fluctuates.Previously-developed strategies for the real-time detection of small-molecule analytes have typically made use of sensors that measure changes in mass, 5 index of refraction 6 or charge 7 that occur when the target molecules bind to the sensor surface. Such measurements, however, suffer from often severe false positives; for example, it has proven difficult to discriminate between changes in mass arising from the binding of authentic target molecules and those *To whom all correspondence should be addressed. arising due to the non-specific adsorption of contaminants, which has significantly hindered the application of these adsorption-based sensors in complex samples, such as unprocessed clinical or environmental materials. [5][6][7] In contrast, sensors based on binding-induced conformational changes in a bimolecular probe [8][9] have proven more effective in rejecting such false positives. An example is the electrochemical, aptamer-based (E-AB) sensor platform, which operates via the target binding-induced folding of DNA and RNA aptamers and has been shown to work directly in blood serum, 10-12 crude cellular extracts, 13 soil extracts 14 and foodstuffs. 15 The high ...

Lactate (La) has long been at the center of controversy in research, clinical, and athletic settings. Since its discovery in 1780, La has often been erroneously viewed as simply a hypoxic waste product with multiple deleterious effects. Not until the 1980s, with the introduction of the cell-to-cell lactate shuttle did a paradigm shift in our understanding of the role of La in metabolism begin. The evidence for La as a major player in the coordination of whole-body metabolism has since grown rapidly. La is a readily combusted fuel that is shuttled throughout the body, and it is a potent signal for angiogenesis irrespective of oxygen tension. Despite this, many fundamental discoveries about La are still working their way into mainstream research, clinical care, and practice. The purpose of this review is to synthesize current understanding of La metabolism via an appraisal of its robust experimental history, particularly in exercise physiology. That La production increases during dysoxia is beyond debate, but this condition is the exception rather than the rule. Fluctuations in blood [La] in health and disease are not typically due to low oxygen tension, a principle first demonstrated with exercise and now understood to varying degrees across disciplines. From its role in coordinating whole-body metabolism as a fuel to its role as a signaling molecule in tumors, the study of La metabolism continues to expand and holds potential for multiple clinical applications. This review highlights La's central role in metabolism and amplifies our understanding of past research.

Through much of the history of metabolism, lactate (La−) has been considered merely a dead-end waste product during periods of dysoxia. Congruently, the end product of glycolysis has been viewed dichotomously: pyruvate in the presence of adequate oxygenation, La− in the absence of adequate oxygenation. In contrast, given the near-equilibrium nature of the lactate dehydrogenase (LDH) reaction and that LDH has a much higher activity than the putative regulatory enzymes of the glycolytic and oxidative pathways, we contend that La− is always the end product of glycolysis. Cellular La− accumulation, as opposed to flux, is dependent on (1) the rate of glycolysis, (2) oxidative enzyme activity, (3) cellular O2 level, and (4) the net rate of La− transport into (influx) or out of (efflux) the cell. For intracellular metabolism, we reintroduce the Cytosol-to-Mitochondria Lactate Shuttle. Our proposition, analogous to the phosphocreatine shuttle, purports that pyruvate, NAD+, NADH, and La− are held uniformly near equilibrium throughout the cell cytosol due to the high activity of LDH. La− is always the end product of glycolysis and represents the primary diffusing species capable of spatially linking glycolysis to oxidative phosphorylation.

The ability to obtain sequence-specific genetic information about rare target organisms directly from complex biological samples at the point of care would transform many areas of biotechnology. Microfluidics technology offers compelling tools for integrating multiple biochemical processes in a single device, but despite significant progress, only limited examples have shown specific, genetic analysis of clinical samples within the context of a fully integrated, portable platform. Herein we present the Magnetic Integrated Microfluidic Electrochemical Detector (MIMED) that integrates sample preparation and electrochemical sensors in a monolithic disposable device to detect RNA-based virus directly from patient samples. By combining immunomagnetic target capture, concentration and purification, reverse-transcriptase polymerase chain reaction (RT-PCR) and single-stranded DNA (ssDNA) generation in the sample preparation chamber, as well as sequence specific electrochemical DNA detection in the electrochemical cell, we demonstrate the detection of influenza H1N1 in throat swab samples at loads as low as 10 TCID50 - 4 orders of magnitude below the clinical titer for this virus. Given the availability of affinity reagents for a broad range of pathogens, our system offers a general approach for multi-target diagnostics at the point-of-care.