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.

Biomembrane-Functionalized Micromotors: Biocompatible Active Devices for Diverse Biomedical Applications.

There has been considerable interest in developing synthetic micromotors with biofunctional, versatile, and adaptive capabilities for biomedical applications. In this perspective, cell membrane-functionalized micromotors emerge as an attractive platform. This new class of micromotors demonstrates enhanced propulsion and compelling performance in complex biological environments, making them suitable for various in vivo applications, including drug delivery, detoxification, immune modulation, and phototherapy. This article reviews various proof-of-concept studies based on different micromotor designs and cell membrane coatings in these areas. The review focuses on the motor structure and performance relationship and highlights how cell membrane functionalization overcomes the obstacles faced by traditional synthetic micromotors while imparting them with unique capabilities. Overall, the cell membrane-functionalized micromotors are expected to advance micromotor research and facilitate its translation towards practical uses.

Decentralized vitamin C & D dual biosensor chip: Toward personalized immune system support.

Combating the ongoing COVID-19 pandemic has put the spotlight on nutritional support of the immune system through consumption of vitamins C and D. Accordingly, there are urgent demands for an effective on-the-spot multi-vitamin self-testing platform that monitors the levels of these immune-supporting micronutrients for guiding precision nutrition recommendations. Herein, we present a compact bioelectronic dual sensor chip aimed at frequent on-the-spot simultaneous monitoring of the salivary vitamin C and D dynamics. The new bioelectronic chip combines a new electrocatalytic vitamin C amperometric assay along with competitive vitamin D immunoassay on neighboring electrodes, to perform selective and cross-talk free detection of both vitamins in a 10-µL saliva sample within 25 min. The distinct vitamin C or D temporal profiles obtained for different individuals after vitamin supplementation indicate the potential of the new bioelectronic chip strategy for enhancing personalized nutrition towards guiding dietary interventions to meet individual nutrition needs and promote immune system health.

Micromotors for Active Delivery of Minerals toward the Treatment of Iron Deficiency Anemia.

As the most common nutritional disorder, iron deficiency represents a major public health problem with broad impacts on physical and mental development. However, treatment is often compromised by low iron bioavailability and undesired side effects. Here, we report on the development of active mineral delivery vehicles using Mg-based micromotors, which can autonomously propel in gastrointestinal fluids, aiding in the dynamic delivery of minerals. Iron and selenium are combined as a model mineral payload in the micromotor platform. We demonstrate the ability of our mineral-loaded micromotors to replenish iron and selenium stores in an anemic mouse model after 30 days of treatment, normalizing hematological parameters such as red blood count, hemoglobin, and hematocrit. Additionally, the micromotor platform exhibits no toxicity after the treatment regimen. This proof-of-concept study indicates that micromotor-based active delivery of mineral supplements represents an attractive approach toward alleviating nutritional deficiencies.

Chemical Sensing at the Robot Fingertips: Toward Automated Taste Discrimination in Food Samples.

The development of robotic sensors that mimic the human sensing capabilities is critical for the interaction and cognitive abilities of modern robots. Though robotic skin with embedded pressure or temperature sensors has received recent attention, robotic chemical sensors have long been unnoticed due to the challenges associated with realizing chemical sensing modalities on robotic platforms. For realizing such chemically sensitive robotic skin, we exploit here the recent advances in wearable chemical sensor technology and flexible electronics, and describe chemical sensing robotic fingers for rapid screening of food flavors and additives. The stretchable taste-sensing finger electrochemical devices are printed on the robotic glove, which simulates the soft skin, and are integrated with a wireless electronic board for real-time data transmission. The printed middle, index, and ring robotic fingers allow accurate discrimination between sweetness, sourness, and spiciness, via direct electrochemical detection of glucose, ascorbic acid, and capsaicin. The sweet-sensing ability has been coupled with a caffeine-sensing robotic finger for rapid screening of the presence of sugar and caffeine in common beverages. The "sense of taste" chemically sensitive robotic technology thus enables accurate discrimination between different flavors, as was illustrated in numerous tests involving a wide range of liquid and solid food samples. Such realization of advanced wearable taste-sensing systems at the robot fingertips should pave the way to automated chemical sensing machinery, facilitating robotic decision for practical food assistance applications, with broad implications to a wide range of robotic sensing applications.

Edible Electrochemistry: Food Materials Based Electrochemical Sensors.

This study demonstrates the first example of completely food-based edible electrochemical sensors. The new edible composite electrodes consist of food materials and supplements serving as the edible conductor, corn, and olive oils as edible binders, vegetables as biocatalysts, and food-based packing sleeves. These edible composite electrodes are systematically characterized for their attractive electrochemical properties, such as potential window, capacitance, redox activity using various electrochemical techniques. The sensing performance of the edible carbon composite electrodes compares favorably with that of "traditional" carbon paste electrodes. Well defined voltammetric detection of catechol, uric acid, ascorbic acid, dopamine, and acetaminophen is demonstrated, including sensitive measurements in simulated saliva, gastric fluid, and intestinal fluid. Furthermore, successful biosensing applications are realized by incorporating a mushroom and horseradish vegetable tissues with edible carbon pastes for imparting biocatalytic activity toward the biosensing of phenolic and peroxide compounds. The attractive sensing performance of the new edible sensors indicates considerable promise for physiological monitoring applications and for developing edible and ingestible devices for diverse biomedical applications.

Stamp transfer electrodes for electrochemical sensing on non-planar and oversized surfaces.

This article describes a new alternative approach to the fabrication of printed electrochemical sensors and biosensors based on the transfer of electrode patterns comprising common conductive and insulating inks from elastomeric stamps to a wide variety of rigid and flexible substrates. This simple, low cost, yet robust methodology is demonstrated to be well-suited for the formation of electrochemical sensors on non-planar substrates and large objects/structures, which have traditionally been off-limits to conventional screen printing techniques. Furthermore, the stamped electrode devices are shown to exhibit electrochemical performance that rivals that of their screen printed counterparts and display resilience against severe mechanical deformation. The stamp transfer approach is further extended to the demonstration of epidermal electrochemical sensors through the transfer of the electrode patterns directly onto the skin. The resulting sensors demonstrate a wide range of usability, from the detection of various physiological analytes, including uric acid on the skin, to the identification of residues originating from the handling of munitions and explosives. The migration of printable electrochemical sensors to non-conventional (non-planar and/or oversized) surfaces provides new opportunities within the personal healthcare, fitness, forensics, homeland security, and environmental monitoring domains.

Amplified label-free electrical detection of DNA hybridization.

A new protocol is described for amplifying label-free electrochemical measurements of DNA hybridization based on the enhanced accumulation of purine nucleobases in the presence of copper ions . Such electrical DNA assays involve hybridization of the target to inosine-substituted oligonucleotide probes (captured on magnetic beads), acidic dipurinization of the hybrid DNA, and adsorptive chronopotentiometric stripping measurements of the free nucleobases in the presence of copper ions. Both amplified adenine and guanine peaks can be used for detecting the DNA hybridization. The dramatic signal amplification advantage of this type of detection has been combined with efficient magnetic removal of non-complementary DNA, use of microliter sample volumes and disposable transducers. Factors influencing the signal enhancement were assessed and optimized. A detection limit of 40 fmol (250 pg) was obtained with 10 min hybridization and 5 min adsorptive-accumulation times. The advantages of this procedure were demonstrated by its application in the detection of DNA segments related to the BRCA1 breast cancer gene. The copper enhancement holds great promise not only for the detection of DNA hybridization, but also for trace measurement of nucleic acids.