Microneedle coupled epidermal sensor for multiplexed electrochemical detection of kidney disease biomarkers

Harnessing the role of microneedles as sensors: current status and future perspectives

In recent years, microneedles (MNs) have been transformed to serve a wide range of applications in the biomedical field. Their role as sensors in wearable devices has provided an alternative to blood-based monitoring of health and diagnostic methods. Hence, they have become a topic of research interest for several scientists working in the biomedical field. These MNs as sensors offer the continuous monitoring of biomarkers like glucose, nucleic acids, proteins, polysaccharides and electrolyte ions, which can therefore screen for and diagnose disease conditions in humans. The present review focuses on types of MN sensors and their applications. Various clinical trials and bottlenecks of MN R&D are also discussed.

Polymeric Microneedles for Health Care Monitoring: An Emerging Trend

Bioanalyte collection by blood draw is a painful process, prone to needle phobia and injuries. Microneedles can be engineered to penetrate the epidermal skin barrier and collect analytes from the interstitial fluid, arising as a safe, painless, and effective alternative to hypodermic needles. Although there are plenty of reviews on the various types of microneedles and their use as drug delivery systems, there is a lack of systematization on the application of polymeric microneedles for diagnosis. In this review, we focus on the current state of the art of this field, while providing information on safety, preclinical and clinical trials, and market distribution, to outline what we believe will be the future of health monitoring.

Continuous Ketone Monitoring via Wearable Microneedle Patch Platform

Ketone bodies (KBs), especially β-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, β-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.

Wearable Microneedle Patch for Transdermal Electrochemical Monitoring of Urea in Interstitial Fluid

Microneedle-based wearable electrochemical biosensors are the new frontier in personalized health monitoring and disease diagnostic devices that provide an alternative tool to traditional blood-based invasive techniques. Advancements in micro- and nanofabrication technologies enabled the fabrication of microneedles using different biomaterials and morphological features with the aim of overcoming existing challenges and enhancing sensing performance. In this work, we report a microneedle array featuring conductive recessed microcavities for monitoring urea levels in the interstitial fluid of the skin. Microcavities are small pockets on the tip of each microneedle that can accommodate the sensing layer, provide protection from delamination during skin insertion or removal, and position the sensing layer in a deep layer of the skin to reach the interstitial fluid. The wearable urea patch has shown to be highly sensitive and selective in monitoring urea, with a sensitivity of 2.5 mV mM-1 and a linear range of 3 to 18 mM making it suitable for monitoring urea levels in healthy individuals and patients. Our ex vivo experiments have shown that recessed microcavities can protect the sensing layer from delamination during skin insertion and monitor changing urea levels in interstitial fluid. This biocompatible platform provides alternative solutions to the critical issue of maintaining the performance of the biosensor upon skin insertion and holds great potential for advancing transdermal sensor technology.

Association of long-term triglyceride-glucose index patterns with the incidence of chronic kidney disease among non-diabetic population: evidence from a functional community cohort

BACKGROUND

The triglyceride-glucose (TyG) index is a reliable surrogate marker of insulin resistance and previous studies have confirmed the association of TyG index with incident chronic kidney disease (CKD). However, the impact of longitudinal patterns of TyG index on CKD risk among non-diabetic population is still unknown. Therefore, this study aimed to investigate the association of longitudinal patterns of TyG index with incident CKD among non-diabetic population.

METHODS

A total of 5484 non-diabetic participants who underwent one health examination per year from 2015 to 2017 were included in this prospective study. TyG index variability and cumulative TyG index were calculated to assess the longitudinal patterns of TyG index. Cox proportional hazard models were performed to estimate the association of TyG index variability or cumulative TyG index with incident CKD.

RESULTS

During a median of 3.82 years follow-up, 879 participants developed CKD. Compared with participants in the lowest quartile, the hazard ratio (HR) and 95% confidence interval (CI) of incident CKD were 1.772 (95% CI: 1.453, 2.162) for the highest TyG index variability quartile and 2.091 (95% CI: 1.646, 2.655) for the highest cumulative TyG index quartile in the fully adjusted models. The best discrimination and reclassification improvement were observed after adding baseline TyG, TyG index variability and cumulative TyG index to the clinical risk model for CKD.

CONCLUSIONS

Both TyG index variability and cumulative TyG index can independently predict incident CKD among non-diabetic population. Monitoring longitudinal patterns of TyG index may assist with prediction and prevention of incident CKD.

Dissolving and Swelling Hydrogel-Based Microneedles: An Overview of Their Materials, Fabrication, Characterization Methods, and Challenges

Polymeric hydrogels are a complex class of materials with one common feature-the ability to form three-dimensional networks capable of imbibing large amounts of water or biological fluids without being dissolved, acting as self-sustained containers for various purposes, including pharmaceutical and biomedical applications. Transdermal pharmaceutical microneedles are a pain-free drug delivery system that continues on the path to widespread adoption-regulatory guidelines are on the horizon, and investments in the field continue to grow annually. Recently, hydrogels have generated interest in the field of transdermal microneedles due to their tunable properties, allowing them to be exploited as delivery systems and extraction tools. As hydrogel microneedles are a new emerging technology, their fabrication faces various challenges that must be resolved for them to redeem themselves as a viable pharmaceutical option. This article discusses hydrogel microneedles from a material perspective, regardless of their mechanism of action. It cites the recent advances in their formulation, presents relevant fabrication and characterization methods, and discusses manufacturing and regulatory challenges facing these emerging technologies before their approval.