Continuous Ketone Monitoring via Wearable Microneedle Patch Platform.

Ketone bodies (KBs), especially ß-hydroxybutyrate (BHB), have gained tremendous attention as potential biomarkers as their presence in bodily fluids is closely associated with health and wellness. While a variety of blood fingerstick test strips are available for self-testing of BHB, there are major needs for wearable devices capable of continuously tracking changing BHB concentrations. To address these needs, we present here the first demonstration of a wearable microneedle-based continuous ketone monitoring (CKM) in human interstitial fluid (ISF) and illustrate its ability to closely follow the intake of ketone drinks. To ensure highly stable and selective continuous detection of ISF BHB, the new enzymatic microneedle BHB sensor relies on a gold-coated platinum working electrode modified with a reagent layer containing toluidine blue O (TBO) redox mediator, ß-hydroxybutyrate dehydrogenase (HBD) enzyme, a nicotinamide adenine dinucleotide (NAD+) cofactor, along with carbon nanotubes (CNTs), chitosan (Chit), and a poly(vinyl chloride) (PVC) outer protective layer. The skin-worn microneedle sensing device operates with a miniaturized electrochemical analyzer connected wirelessly to a mobile electronic device for capturing, processing, and displaying the data. Cytotoxicity and skin penetration studies indicate the absence of potential harmful effects. A pilot study involving multiple human subjects evaluated continuous BHB monitoring in human ISF, against gold standard BHB meter measurements, revealing the close correlation between the two methods. Such microneedle-based CKM offers considerable promise for dynamic BHB tracking toward the management of diabetic ketoacidosis and personal nutrition and wellness.

Disposable screen-printed electrochemical sensing strips for rapid decentralized measurements of salivary ketone bodies: Towards therapeutic and wellness applications.

The interest in ketone bodies (KBs) has intensified recently as they play significant roles in healthcare, nutrition, and wellness applications. We present a disposable electrochemical sensing strip for rapid decentralized detection of ß-hydroxybutyrate (HB), one of the dominant physiological KBs, in saliva. The new salivary enzymatic HB sensor strip relies on a gold-coated screen-printed carbon electrode modified with a reagent layer containing toluidine blue O (TBO mediator), ß-hydroxybutyrate dehydrogenase (HBD enzyme), and the HBD cofactor nicotinamide adenine dinucleotide (NAD+ coenzyme), along with carbon nanotubes (CNTs) and chitosan (Chit) for enhancing the sensor's sensitivity and for encapsulating the enzyme and its cofactor, respectively. The systematic optimization resulted in an attractive analytical performance, with a rapid response time within 60 s, a wide HB dynamic detection range from 0.1 to 3.0 mM along with a low limit of detection (50 µM HB) in an artificial saliva medium. The strip displays high selectivity for HB over acetoacetate (AcAc) and other interferences (i.e., acetaminophen, ascorbic acid, glucose, lactic acid, and uric acid), good reproducibility, and high stability towards temperature or pH effects. The new disposable sensing strip system, coupled with a hand-held electrochemical analyzer, showed rapid HB monitoring in human saliva samples collected from healthy volunteers, with similar temporal profiles to those obtained in parallel capillary blood measurements in response to the intake of keto supplements. This strip enables efficient, reliable, and near real-time salivary HB detection to track non-invasively the dynamics of HB concentrations after intaking commercial supplements towards diverse healthcare and nutrition applications.

Self-Testing of Ketone Bodies, along with Glucose, Using Touch-Based Sweat Analysis.

ß-Hydroxybutyrate (HB) is one of the main physiological ketone bodies that play key roles in human health and wellness. Besides their important role in diabetes ketoacidosis, ketone bodies are currently receiving tremendous attention for personal nutrition in connection to the growing popularity of oral ketone supplements. Accordingly, there are urgent needs for developing a rapid, simple, and low-cost device for frequent onsite measurements of ß-hydroxybutyrate (HB), one of the main physiological ketone bodies. However, real-time profiling of dynamically changing HB concentrations is challenging and still limited to laboratory settings or to painful and invasive measurements (e.g., a commercial blood ketone meter). Herein, we address the critical need for pain-free frequent HB measurements in decentralized settings and report on a reliable noninvasive, simple, and rapid touch-based sweat HB testing and on its ability to track dynamic HB changes in secreted fingertip sweat, following the intake of commercial ketone supplements. The new touch-based HB detection method relies on an instantaneous collection of the fingertip sweat at rest on a porous poly(vinyl alcohol) (PVA) hydrogel that transports the sweat to a biocatalytic layer, composed of the ß-hydroxybutyrate dehydrogenase (HBD) enzyme and its nicotinamide adenine dinucleotide (NAD+) cofactor, covering the modified screen-printed carbon working electrode. As a result, the sweat HB can be measured rapidly by the mediated oxidation reaction of the nicotinamide adenine dinucleotide (NADH) product. A personalized HB dose-response relationship is demonstrated within a group of healthy human subjects taking commercial ketone supplements, along with a correlation between the sweat and capillary blood HB levels. Furthermore, a dual disposable biosensing device, consisting of neighboring ketone and glucose enzyme electrodes on a single-strip substrate, has been developed toward the simultaneous touch-based detection of dynamically changing sweat HB and glucose levels, following the intake of ketone and glucose drinks.

Lab on a body for biomedical electrochemical sensing applications: The next generation of microfluidic devices.

This chapter highlights applications of microfluidic devices toward on-body biosensors. The emerging application of microfluidics to on-body bioanalysis is a new strategy to establish systems for the continuous, real-time, and on-site determination of informative markers present in biofluids, such as sweat, interstitial fluid, blood, saliva, and tear. Electrochemical sensors are attractive to integrate with such microfluidics due to the possibility to be miniaturized. Moreover, on-body microfluidics coupled with bioelectronics enable smart integration with modern information and communication technology. This chapter discusses requirements and several challenges when developing on-body microfluidics such as difficulties in manipulating small sample volumes while maintaining mechanical flexibility, power-consumption efficiency, and simplicity of total automated systems. We describe key components, e.g., microchannels, microvalves, and electrochemical detectors, used in microfluidics. We also introduce representatives of advanced lab-on-a-body microfluidics combined with electrochemical sensors for biomedical applications. The chapter ends with a discussion of the potential trends of research in this field and opportunities. On-body microfluidics as modern total analysis devices will continue to bring several fascinating opportunities to the field of biomedical and translational research applications.

Advances in emergent biological recognition elements and bioelectronics for diagnosing COVID-19.

Coronaviruses pose a serious threat to public health. Tremendous efforts are dedicated to advance reliable and effective detection of coronaviruses. Currently, the coronavirus disease 2019 (COVID-19) diagnosis mainly relies on the detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genetic materials by using reverse transcription-polymerase chain reaction (RT-PCR) assay. However, simpler and more rapid and reliable alternatives are needed to meet high demand during the pandemic. Biosensor-based diagnosis approaches become alternatives for selectively and rapidly detecting virus particles because of their biorecognition elements consisting of biomaterials that are specific to virus biomarkers. Here, we summarize biorecognition materials, including antibodies and antibody-like molecules, that are designed to recognize SARS-CoV-2 biomarkers and the advances of recently developed biosensors for COVID-19 diagnosis. The design of biorecognition materials or layers is crucial to maximize biosensing performances, such as high selectivity and sensitivity of virus detection. Additionally, the recent representative achievements in developing bioelectronics for sensing coronavirus are included. This review includes scholarly articles, mainly published in 2020 and early 2021. In addition to capturing the fast development in the fields of applied materials and biodiagnosis, the outlook of this rapidly evolving technology is summarized. Early diagnosis of COVID-19 could help prevent the spread of this contagious disease and provide significant information to medical teams to treat patients.

An integrated microcatheter-based dual-analyte sensor system for simultaneous, real-time measurement of propofol and fentanyl.

According to the American Society of Anesthesiologists Closed Claims Database, one of three drug-related errors is the result administrating an incorrect dose. Directly measuring drug concentration removes the uncertainty in the dose-concentration relationship and addresses inter- and intra-subject variabilities that affect the pharmacokinetics of anesthetics. Here we describe a dual-analyte microcatheter-based electrochemical sensor capable of simultaneous real-time continuous monitoring of fentanyl (FTN) and propofol (PPF) drugs simultaneously in the operating rooms. Such a dual PPF/FTN catheter sensor relies on embedding two different modified carbon paste (CP)-packed working electrodes along with Ag/AgCl microwire reference electrodes within a mm-wide Teflon tube, and uses a square wave voltammetric (SWV) technique. The composition of each working electrode was judiciously tailored to cover the concentration range of interest for each analyte. A polyvinyl chloride (PVC) organic polymer coating on the surface of CP electrode enabled selective and sensitive PPF measurements in µM range. The detection of nM FTN levels was achieved through a multilayered nanostructure-based surface modification protocol, including a CNT-incorporated CP transducer modified by a hybrid of electrodeposited Au nanoparticles and electrochemically reduced graphene oxide (erGO) and a PVC outer membrane. The long-term monitoring capability of the dual sensor was demonstrated in a protein-rich artificial plasma medium. The promising antibiofouling behavior of the catheter-based multiplexed sensor was also illustrated in whole blood samples. The new integrated dual-sensor microcatheter platform holds considerable promise towards real-time, in-vivo detection of the anesthetic drugs, propofol and fentanyl, during surgical procedures towards significantly improved safe delivery of anesthetic drugs.

A new alternative assay for sensitive analysis of ethylenethiourea and propylenethiourea in fruit samples after their separation.

Ultra-high-performance liquid chromatography (UHPLC) coupled with a cobalt phthalocyanine screen-printed carbon electrode (CoPc-SPCE) was developed and validated for quantitative analysis of ethylenethiourea (ETU) and propylenethiourea (PTU). CoPC-SPCE provided high catalytic properties for ETU and PTU oxidation. This fabricated electrode is inexpensive, disposable, and easy to prepare by an in-house screen-printing technique. The chromatographic separation was performed in isocratic mode on a reversed phase C18 (100 mm × 4.6 mm, 3 µm) column, using a 90 : 10 (v/v) ratio of 0.05 M phosphate buffer solution (pH 4) and methanol as the mobile phase with a flow rate of 1.0 mL min-1 at an oxidation potential of +0.7 V vs. Ag/AgCl. The separation could be achieved within 3 min, and a wide linear range of 0.01-100 µg mL-1 (r2 > 0.99) was obtained for both analytes. The limits of detection (3 S/N) were found to be 0.006 and 0.009 µg mL-1 for ETU and PTU, respectively. Furthermore, this proposed method was utilized to determine ETU and PTU in fruit samples with satisfactory results, yielding excellent intra-day and inter-day relative standard deviations and recoveries. These results demonstrated that the proposed assay can be used as a new alternative way for inexpensive, rapid, selective and sensitive determination of ETU and PTU in fruit samples.

Continuous Opioid Monitoring along with Nerve Agents on a Wearable Microneedle Sensor Array.

There are urgent needs for sensing devices capable of distinguishing between episodes of opioid overdose and nerve agent poisoning. This work presents a wearable microneedle sensor array for minimally invasive continuous electrochemical detection of opioid (OPi) and organophosphate (OP) nerve agents on a single patch platform. The new multimodal microneedle sensor array relies on unmodified and organophosphorus hydrolase (OPH) enzyme-modified carbon paste (CP) microneedle electrodes for square wave voltammetric (SWV) detection of the fentanyl and nerve agent targets, respectively. Such real-time simultaneous sensing provides distinct unique information, along with attractive analytical performance, including high sensitivity, selectivity, and stability, for real-time on-body OPi-OP analysis. The patch represents the first sensing device capable of continuously monitoring fentanyl down to the nanomolar level through a nanomaterial-based multilayered surface architecture. Applicability of the sensor array toward opioids screening is demonstrated for morphine and norfentanyl. Successful OPi-OP detection conducted in a skin-mimicking phantom gel demonstrates the suitability of the device for rapid on-body sensing. Such progress toward continuous minimally invasive transdermal analysis of drugs of abuse and nerve agents holds promise for rapid countermeasures for protecting soldiers, civilians, and healthcare personnel.

Microneedle-Based Detection of Ketone Bodies along with Glucose and Lactate: Toward Real-Time Continuous Interstitial Fluid Monitoring of Diabetic Ketosis and Ketoacidosis.

Diabetic ketoacidosis (DKA), a severe complication of diabetes mellitus with potentially fatal consequences, is characterized by hyperglycemia and metabolic acidosis due to the accumulation of ketone bodies, which requires people with diabetes to monitor both glucose and ketone bodies. However, despite major advances in diabetes management mainly since the emergence of new-generation continuous glucose monitoring (CGM) devices capable of in vivo monitoring of glucose directly in the interstitial fluid (ISF), the continuous monitoring of ketone bodies is yet to be addressed. Here, we present the first use of a real-time continuous ketone bodies monitoring (CKM) microneedle platform. The system is based on the electrochemical monitoring of ß-hydroxybutyrate (HB) as the dominant biomarker of ketone formation. Such real-time HB detection has been realized using the ß-hydroxybutyrate dehydrogenase (HBD) enzymatic reaction and by addressing the major challenges associated with the stable confinement of the enzyme/cofactor couple (HBD/NAD+) and with a stable and selective low-potential fouling-free anodic detection of NADH. The resulting CKM microneedle device displays an attractive analytical performance, with high sensitivity (with low detection limit, 50 µM), high selectivity in the presence of potential interferences, along with good stability during prolonged operation in artificial ISF. The potential applicability of this microneedle sensor toward minimally invasive monitoring of ketone bodies has been demonstrated in a phantom gel skin-mimicking model. The ability to detect HB along with glucose and lactate on a single microneedle array has been demonstrated. These findings pave the way for CKM and for the simultaneous microneedle-based monitoring of multiple diabetes-related biomarkers toward a tight glycemic control.

Wearable Electrochemical Microneedle Sensor for Continuous Monitoring of Levodopa: Toward Parkinson Management.

Levodopa is the most effective medication for treating Parkinson's disease (PD). However, because dose optimization is currently based on patients' report of symptoms, which are difficult for patients to describe, the management of PD is challenging. We report on a microneedle sensing platform for continuous minimally invasive orthogonal electrochemical monitoring of levodopa (L-Dopa). The new multimodal microneedle sensing platform relies on parallel simultaneous independent enzymatic-amperometric and nonenzymatic voltammetric detection of L-Dopa using different microneedles on the same sensor array patch. Such real-time orthogonal L-Dopa sensing offers a built-in redundancy and enhances the information content of the microneedle sensor arrays. This is accomplished by rapid detection of L-Dopa using square-wave voltammetry and chronoamperometry at unmodified and tyrosinase-modified carbon-paste microneedle electrodes, respectively. The new wearable microneedle sensor device displays an attractive analytical performance with the enzymatic and nonenzymatic L-Dopa microneedle sensors offering different dimensions of information while displaying high sensitivity (with a low detection limit), high selectivity in the presence of potential interferences, and good stability in artificial interstitial fluid (ISF). The attractive analytical performance and potential wearable applications of the microneedle sensor array have been demonstrated in a skin-mimicking phantom gel as well as upon penetration through mice skin. The design and attractive analytical performance of the new orthogonal wearable microneedle sensor array hold considerable promise for reliable, continuous, minimally invasive monitoring of L-Dopa in the ISF toward optimizing the dosing regimen of the drug and effective management of Parkinson disease.