Intradermal Lactate Monitoring Based on a Microneedle Sensor Patch for Enhanced In Vivo Accuracy.

Lactate is an important diagnostic and prognostic biomarker of several human pathological conditions, such as sepsis, malaria, and dengue fever. Unfortunately, due to the lack of reliable analytical decentralized platforms, the determination of lactate yet relies on discrete blood-based assays, which are invasive and inefficient and may cause tension and pain in the patient. Herein, we demonstrate the potential of a fully integrated microneedle (MN) sensing system for the minimally invasive transdermal detection of lactate in an interstitial fluid (ISF). The originality of this analytical technology relies on: (i) a strategy to provide a uniform coating of a doped polymer-based membrane as a diffusion-limiting layer on the MN structure, optimized to perform full-range lactate detection in the ISF (linear range of response: 0.25-35 mM, 30 s assay time, 8 h operation), (ii) double validation of ex vivo and in vivo results based on ISF and blood measurements in rats, (iii) monitoring of lactate level fluctuations under the administration of anesthesia to mimic bedside clinical scenarios, and (iv) in-house design and fabrication of a fully integrated and portable sensing device in the form of a wearable patch including a custom application and user-friendly interface in a smartphone for the rapid, routine, continuous, and real-time lactate monitoring. The main analytical merits of the lactate MN sensor include appropriate selectivity, reversibility, stability, and durability by using a two-electrode amperometric readout. The ex-vivo testing of the MN patch of preconditioned rat skin pieces and euthanized rats successfully demonstrated the accuracy in measuring lactate levels. The in vivo measurements suggested the existence of a positive correlation between ISF and blood lactate when a lag time of 10 min is considered (Pearson's coefficient = 0.85, mean difference = 0.08 mM). The developed MN-based platform offers distinct advantages over noncontinuous blood sampling in a wide range of contexts, especially where access to laboratory services is limited or blood sampling is not suitable. Implementation of the wearable patch in healthcare could envision personalized medicine in a variety of clinical settings.

How to develop a bio-based phosphorus mining strategy for eutrophic marine sediments: Unlocking native microbial processes for anaerobic phosphorus release.

This study examined the anaerobic release of phosphorus (P) from two different Baltic Sea sediments (B and F), focusing on the impact of initial concentration of externally introduced waste-derived volatile fatty acids (VFA) as the carbon source, temperature, pH, and mixing conditions. The first batch bioreactor set was operated to demonstrate the effect of VFA on anaerobic P release at different concentrations (1000-10000 mg/L as COD) at 20 °C. A notable P release of up to 15.85 mg/L PO4-P was observed for Sediment B at an initial carbon concentration of 10000 mg COD/L. However, VFA consumption in the bioreactors was minimal or no subsequent. The second batch bioreactor set was carried out to investigate the effect of temperature (20 °C-35 °C), pH (5.5, 7.0 and 8.5) and mixing conditions on P release by introducing lower initial carbon concentration (1000 mg COD/L) considering the potential risk for VFA accumulation in the bioreactors. Maximum P releases of 4.4 mg/L and 3.5 mg/L were for Sediment B and Sediment F, respectively. Two-way ANOVA tests revealed that the operation time and pH and their interactions were statistically significant (p < 0.05) for both sediments while the effect of mixing was not statistically significant. Most of the sulfate was reduced during batch bioreactor operation and Desulfomicobiaceae became dominant among other sulfate-reducing bacteria (SRB) possibly shows the importance of SRB in terms of anaerobic P release. This study gives an insight into future implementations of phosphorus mining from eutrophic environment under anaerobic conditions.

Light-induced Delivery of Charged Species using Ion-selective Core-Shell Nanoparticles.

Controlled release systems have gained considerable attention owing to their potential to deliver molecules, including ions and drugs, in a customized manner. We present a light-induced ion-transfer platform consisting of a dispersion of nanoparticles (NPs, ~300 nm) with the conductive polymer poly(3-octylthiophene-2,5-diyl) (POT) in the core and a potassium (K+)-selective membrane in the shell. Owing to the photoactive nature of POT, POT NPs can be used for a dual purpose: as a host for positively charged species and as an actuator to trigger the subsequent release. POT0 and doped POT+ coexist in the core, allowing K+ encapsulation in the shell. As POT0 is photo-oxidized to POT+, K+ is released to the (aqueous) dispersion phase to preserve the neutrality of the NPs. This process is reversible and can be simultaneously assessed using the native fluorescence of POT0 and via potentiometric measurements. The NP structure and its mechanism of action were thoroughly studied with a series of control experiments and complementary techniques. Understanding the NP and its surrounding interactions will pave the way for other nanostructured systems, facilitating sophisticated applications. The delivery of ionic drugs and interference/pollutant catching for advanced sensing/restoration will be considered in future research.

Usefulness of the Distribution of Relaxation Time Method in Electroanalytical Systems: The Case of Voltammetric Ion-Selective Electrodes.

Despite the distribution of relaxation time (DRT) method providing clear insights about processes that go unnoticed by traditional electrochemical impedance spectroscopy (EIS) analysis, it has not yet been adopted to solve electroanalytical systems. As an illustration case, we apply the DRT method to deconvolve EIS data from solid-state voltammetric ion-selective electrodes (ISEs). The main aim is to shed light on the underlying working mechanism across the different materials and interfaces, specifically, the doping of a conducting polymer when covered with a very thin (ca. 230 nm) permselective membrane. Although frequency-dependent AC measurements in EIS allow the separation of processes that contribute to the electrical signal, interpretation of the data is challenging. DRT may overcome this inconvenience by revealing a series of peaks corresponding to the predominant electrochemical processes, without any preknowledge on those. To demonstrate our hypothesis, we examine the conducting polymer poly(3-octylthiophene) (POT) linked to a membrane with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (Na+TFPB-) as the cation exchanger, in which the lipophilic anionic part (TFPB-) is responsible for the POT doping when it gets electrochemically oxidized (POT+). The investigation of EIS data obtained under different conditions with the DRT method showed the occurrence of several processes. We have attributed two of these to two different conformational changes in the POT film in connection with p-type charge-transfer doping. Indeed, the kinetics is found to follow a Butler-Volmer behavior, with average charge transfers of 0.5 and 0.3 mol of electrons for each peak. Overall, we demonstrate the utility of the EIS-DRT tandem to separately study charge-transfer events that interconnect along the same (interfacial segmented) system, which cannot be reached by using classical electrochemical approaches. These kinds of insights are necessary for a more efficient design and high-level exploitation of voltammetric ISEs but also other electrochemical systems such as catalysts, batteries, and photovoltaic cells.

Voltammetric Ion-Selective Electrodes in Thin-Layer Samples: Absolute Detection of Ions Using Ultrathin Membranes.

Calibration-free sensors are generally understood as analytical tools with no need for calibration apart from the initial one (i.e., after its fabrication). However, an "ideal" and therefore "more restricted" definition of the concept considers that no calibration is necessary at all, with the sensor being capable of directly providing the analyte concentration in the sample. In the electroanalysis field, investigations have been directed to charge-based readouts (i.e., coulometry) that allow for concentration calculation via the Faraday Law: The sample volume must be precisely defined and the absoluteness of the electrochemical process in which the analyte is involved must be ensured (i.e., the analyte in the sample is ∼100% converted/transported). Herein, we report on the realization of calibration-free coulometric ISEs based on ultrathin ion-selective membranes, which is demonstrated for the detection of potassium ions (K+). In essence, the K+ transfer at the membrane-sample interface is modulated by the oxidation state of the conducting polymer underlying the membrane. The accumulation/release of K+ to/from the membrane is an absolute process owing to the confinement of the sample to a thin-layer domain (thickness of <100 µm). The capacity of the membrane expressed in charge is fixed to ca. 18 µC, and this dictates the detection of micromolar levels of K+ present in ca. 5 µL sample volume. The system is interrogated with cyclic voltammetry to obtain peaks related to the K+ transfer that can be treated charge-wise. The conceptual and technical innovative steps developed here made the calibration-free detection of K+ possible in artificial and real samples with acceptable accuracy (<10% difference compared with the results obtained from a current-based calibration and ion chromatography). The charge-based analysis does not depend on temperature and appeared to be repetitive, reproducible, and reversible in the concentration range from 1 to 37.5 µM, with an average coulometry efficiency of 96%.

Demonstrating the Analytical Potential of a Wearable Microneedle-Based Device for Intradermal CO2 Detection.

Monitoring of carbon dioxide (CO2) body levels is crucial under several clinical conditions (e.g., human intensive care and acid-base disorders). To date, painful and risky arterial blood punctures have been performed to obtain discrete CO2 measurements needed in clinical setups. Although noninvasive alternatives have been proposed to assess CO2, these are currently limited to benchtop devices, requiring trained personnel, being tedious, and providing punctual information, among other disadvantages. To the best of our knowledge, the literature and market lack a wearable device for real-time, on-body monitoring of CO2. Accordingly, we have developed a microneedle (MN)-based sensor array, labeled as CO2-MN, comprising a combination of potentiometric pH- and carbonate (CO32-)-selective electrodes together with the reference electrode. The CO2-MN is built on an epidermal patch that allows it to reach the stratum corneum of the skin, measuring pH and CO32- concentrations directly into the interstitial fluid (ISF). The levels for the pH-CO32- tandem are then used to estimate the PCO2 in the ISF. Assessing the response of each individual MN, we found adequate response time (t95 < 5s), sensitivity (50.4 and -24.6 mV dec-1 for pH and CO32-, respectively), and stability (1.6 mV h-1 for pH and 2.1 mV h-1 for CO32-). We validated the intradermal measurements of CO2 at the ex vivo level, using pieces of rat skin, and then, with in vivo assays in anesthetized rats, showing the suitability of the CO2-MN wearable device for on-body measurements. A good correlation between ISF and blood CO2 concentrations was observed, demonstrating the high potential of the developed MN sensing technology as an alternative to blood-based analysis in the near future. Moreover, these results open new horizons in the noninvasive, real-time monitoring of CO2 as well as other clinically relevant gases.

The role of gut microbiota in cerebrovascular disease and related dementia.

In recent years, increasing evidence suggests that commensal microbiota may play an important role not only in health but also in disease including cerebrovascular disease. Gut microbes impact physiology, at least in part, by metabolizing dietary factors and host-derived substrates and then generating active compounds including toxins. The purpose of this current review is to highlight the complex interplay between microbiota, their metabolites. and essential functions for human health, ranging from regulation of the metabolism and the immune system to modulation of brain development and function. We discuss the role of gut dysbiosis in cerebrovascular disease, specifically in acute and chronic stroke phases, and the possible implication of intestinal microbiota in post-stroke cognitive impairment and dementia, and we identify potential therapeutic opportunities of targeting microbiota in this context. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Myeloid cells in vascular dementia and Alzheimer's disease: Possible therapeutic targets?

Growing evidence supports the suggestion that the peripheral immune system plays a role in different pathologies associated with cognitive impairment, such as vascular dementia (VD) or Alzheimer's disease (AD). The aim of this review is to summarize, within the peripheral immune system, the implications of different types of myeloid cells in AD and VD, with a special focus on post-stroke cognitive impairment and dementia (PSCID). We will review the contributions of the myeloid lineage, from peripheral cells (neutrophils, platelets, monocytes and monocyte-derived macrophages) to central nervous system (CNS)-associated cells (perivascular macrophages and microglia). Finally, we will evaluate different potential strategies for pharmacological modulation of pathological processes mediated by myeloid cell subsets, with an emphasis on neutrophils, their interaction with platelets and the process of immunothrombosis that triggers neutrophil-dependent capillary stall and hypoperfusion, as possible effector mechanisms that may pave the way to novel therapeutic avenues to stop dementia, the epidemic of our time. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Selective Deionization of Thin-Layer Samples Using Tandem Carbon Nanotubes-Polymeric Membranes.

Herein, we investigate the selective deionization (i.e., the removal of ions) in thin-layer samples (<100 µm in thickness) using carbon nanotubes (CNTs) covered with an ionophore-based ion-selective membrane (ISM), resulting in a CNT-ISM tandem actuator. The concept of selective deionization is based on a recent discovery by our group ( Anal. Chem. 2022, 94, 21, 7455-7459), where the activation of the CNT-ISM architecture is conceived on a mild potential step that charges the CNTs to ultimately generate the depletion of ions in a thin-layer sample. The role of the ISM is to selectively facilitate the transport of only one ion species to the CNT lattice. To estimate the deionization efficiency of such a process, a potentiometric sensor is placed less than 100 µm away from the CNT-ISM tandem, inside a microfluidic cell. This configuration helped to reveal that the selective uptake of ions increases with the capacitance of the CNTs and that the ISM requires a certain ion-exchanger capacity, but this does not further affect its efficiency. The versatility of the concept is demonstrated by comparing the selective uptake of five different ions (H+, Li+, Na+, K+, and Ca2+), suggesting the possibility to remove any cation from a sample by simply changing the ionophore in the ISM. Furthermore, ISMs based on two ionophores proved to achieve the simultaneous and selective deionization of two ion species using the same actuator. Importantly, the relative uptake between the two ions was found to be governed by the ion-ionophore binding constants, with the most strongly bound ion being favored over other ions. The CNT-ISM actuator concept is expected to contribute to the analytical sensing field in the sense that ionic interferents influencing the analytical signal can selectively be removed from samples to lower traditional limits of detection.

Ipsilesional Hippocampal GABA Is Elevated and Correlates With Cognitive Impairment and Maladaptive Neurogenesis After Cortical Stroke in Mice.

BACKGROUND: Cognitive dysfunction is a frequent stroke sequela, but its pathogenesis and treatment remain unresolved. Involvement of aberrant hippocampal neurogenesis and maladaptive circuitry remodeling has been proposed, but their mechanisms are unknown. Our aim was to evaluate potential underlying molecular/cellular events implicated. METHODS: Stroke was induced by permanent occlusion of the middle cerebral artery occlusion in 2-month-old C57BL/6 male mice. Hippocampal metabolites/neurotransmitters were analyzed longitudinally by in vivo magnetic resonance spectroscopy. Cognitive function was evaluated with the contextual fear conditioning test. Microglia, astrocytes, neuroblasts, interneurons, γ-aminobutyric acid (GABA), and c-fos were analyzed by immunofluorescence. RESULTS: Approximately 50% of mice exhibited progressive post-middle cerebral artery occlusion cognitive impairment. Notably, immature hippocampal neurons in the impaired group displayed more severe aberrant phenotypes than those from the nonimpaired group. Using magnetic resonance spectroscopy, significant bilateral changes in hippocampal metabolites, such as myo-inositol or N-acetylaspartic acid, were found that correlated, respectively, with numbers of glia and immature neuroblasts in the ischemic group. Importantly, some metabolites were specifically altered in the ipsilateral hippocampus suggesting its involvement in aberrant hippocampal neurogenesis and remodeling processes. Specifically, middle cerebral artery occlusion animals with higher hippocampal GABA levels displayed worse cognitive outcome. Implication of GABA in this setting was supported by the amelioration of ischemia-induced memory deficits and aberrant hippocampal neurogenesis after blocking pharmacologically GABAergic neurotransmission, an intervention which was ineffective when neurogenesis was inhibited. These data suggest that GABA exerts its detrimental effect, at least partly, by affecting morphology and integration of newborn neurons into the hippocampal circuits. CONCLUSIONS: Hippocampal GABAergic neurotransmission could be considered a novel diagnostic and therapeutic target for poststroke cognitive impairment.

Defective hippocampal neurogenesis underlies cognitive impairment by carotid stenosis-induced cerebral hypoperfusion in mice.

Chronic cerebral hypoperfusion due to carotid artery stenosis is a major cause of vascular cognitive impairment and dementia (VCID). Bilateral carotid artery stenosis (BCAS) in rodents is a well-established model of VCID where most studies have focused on white matter pathology and subsequent cognitive deficit. Therefore, our aim was to study the implication of adult hippocampal neurogenesis in hypoperfusion-induced VCID in mice, and its relationship with cognitive hippocampal deficits. Mice were subjected to BCAS; 1 and 3 months later, hippocampal memory and neurogenesis/cell death were assessed, respectively, by the novel object location (NOL) and spontaneous alternation performance (SAP) tests and by immunohistology. Hypoperfusion was assessed by arterial spin labeling-magnetic resonance imaging (ASL-MRI). Hypoperfused mice displayed spatial memory deficits with decreased NOL recognition index. Along with the cognitive deficit, a reduced number of newborn neurons and their aberrant morphology indicated a remarkable impairment of the hippocampal neurogenesis. Both increased cell death in the subgranular zone (SGZ) and reduced neuroblast proliferation rate may account for newborn neurons number reduction. Our data demonstrate quantitative and qualitative impairment of adult hippocampal neurogenesis disturbances associated with cerebral hypoperfusion-cognitive deficits in mice. These findings pave the way for novel diagnostic and therapeutic targets for VCID.

Imaging of CO2 and Dissolved Inorganic Carbon via Electrochemical Acidification-Optode Tandem.

Dissolved inorganic carbon (DIC) is a key component of the global carbon cycle and plays a critical role in ocean acidification and proliferation of phototrophs. Its quantification at a high spatial resolution is essential for understanding various biogeochemical processes. We present an analytical method for 2D chemical imaging of DIC by combining a conventional CO2 optode with localized electrochemical acidification from a polyaniline (PANI)-coated stainless-steel mesh electrode. Initially, the optode response is governed by local concentrations of free CO2 in the sample, corresponding to the established carbonate equilibrium at the (unmodified) sample pH. Upon applying a mild potential-based polarization to the PANI mesh, protons are released into the sample, shifting the carbonate equilibrium toward CO2 conversion (>99%), which corresponds to the sample DIC. It is herein demonstrated that the CO2 optode-PANI tandem enables the mapping of free CO2 (before PANI activation) and DIC (after PANI activation) in complex samples, providing high 2D spatial resolution (approx. 400 µm). The significance of this method was proven by inspecting the carbonate chemistry of complex environmental systems, including the freshwater plant Vallisneria spiralis and lime-amended waterlogged soil. This work is expected to pave the way for new analytical strategies that combine chemical imaging with electrochemical actuators, aiming to enhance classical sensing approaches via in situ (and reagentless) sample treatment. Such tools may provide a better understanding of environmentally relevant pH-dependent analytes related to the carbon, nitrogen, and sulfur cycles.

Fully Integrated Wearable Device for Continuous Sweat Lactate Monitoring in Sports.

The chemical digitalization of sweat using wearable sensing interfaces is an attractive alternative to traditional blood-based protocols in sports. Although sweat lactate has been claimed to be a relevant biomarker in sports, an analytically validated wearable system to prove that has not yet been developed. We present a fully integrated sweat lactate sensing system applicable to in situ perspiration analysis. The device can be conveniently worn in the skin to monitor real-time sweat lactate during sports, such as cycling and kayaking. The novelty of the system is threefold: advanced microfluidics design for sweat collection and analysis, an analytically validated lactate biosensor based on a rational design of an outer diffusion-limiting membrane, and an integrated circuit for signal processing with a custom smartphone application. The sensor covering the range expected for lactate in sweat (1-20 mM), with appropriate sensitivity (-12.5 ± 0.53 nA mM-1), shows an acceptable response time (<90 s), and the influence of changes in pH, temperature, and flow rate are neglectable. Also, the sensor is analytically suitable with regard to reversibility, resilience, and reproducibility. The sensing device is validated through a relatively high number of on-body tests performed with elite athletes cycling and kayaking in controlled environments. Correlation outcomes between sweat lactate and other physiological indicators typically accessible in sports laboratories (blood lactate, perceived exhaustion, heart rate, blood glucose, respiratory quotient) are also presented and discussed in relation to the sport performance monitoring capability of continuous sweat lactate.

Portable All-in-One Electrochemical Actuator-Sensor System for the Detection of Dissolved Inorganic Phosphorus in Seawater.

We present a methodology for the detection of dissolved inorganic phosphorous (DIP) in seawater using an electrochemically driven actuator-sensor system. The motivation for this work stems from the lack of tangible solutions for the in situ monitoring of nutrients in water systems. It does not require the addition of any reagents to the sample and works under mild polarization conditions, with the sample confined to a thin-layer compartment. Subsequent steps include the oxidation of polyaniline to lower the pH, the delivery of molybdate via a molybdenum electrode, and the formation of an electroactive phosphomolybdate complex from DIP species. The phosphomolybdate complex is ultimately detected by either cyclic voltammetry (CV) or square wave voltammetry (SWV). The combined release of protons and molybdate consistently results in a sample pH < 2 as well as a sufficient excess of molybdate, fulfilling the conditions required for the stoichiometric detection of DIP. The current of the voltammetric peak was found to be linearly related to DIP concentrations between 1 and 20 µM for CV and 0.1 and 20 µM for SWV, while also being selective against common silicate interference. The analytical application of the system was demonstrated by the validated characterization of five seawater samples, revealing an acceptable degree of difference compared to chromatography measurements. This work paves the way for the future DIP digitalization in environmental waters by in situ electrochemical probes with unprecedented spatial and temporal resolution. It is expected to provide real-time data on anthropogenic nutrient discharges as well as the improved monitoring of seawater restoration actions.

Perinatal exposure to pesticides alters synaptic plasticity signaling and induces behavioral deficits associated with neurodevelopmental disorders.

Increasing evidence from animal and epidemiological studies indicates that perinatal exposure to pesticides cause developmental neurotoxicity and may increase the risk for psychiatric disorders such as autism and intellectual disability. However, the underlying pathogenic mechanisms remain largely elusive. This work was aimed at testing the hypothesis that developmental exposure to different classes of pesticides hijacks intracellular neuronal signaling contributing to synaptic and behavioral alterations associated with neurodevelopmental disorders (NDD). Low concentrations of organochlorine (dieldrin, endosulfan, and chlordane) and organophosphate (chlorpyrifos and its oxon metabolite) pesticides were chronically dosed ex vivo (organotypic rat hippocampal slices) or in vivo (perinatal exposure in rats), and then biochemical, electrophysiological, behavioral, and proteomic studies were performed. All the pesticides tested caused prolonged activation of MAPK/ERK pathway in a concentration-dependent manner. Additionally, some of them impaired metabotropic glutamate receptor-dependent long-term depression (mGluR-LTD). In the case of the pesticide chlordane, the effect was attributed to chronic modulation of MAPK/ERK signaling. These synaptic alterations were reproduced following developmental in vivo exposure to chlordane and chlorpyrifos-oxon, and were also associated with prototypical behavioral phenotypes of NDD, including impaired motor development, increased anxiety, and social and memory deficits. Lastly, proteomic analysis revealed that these pesticides differentially regulate the expression of proteins in the hippocampus with pivotal roles in brain development and synaptic signaling, some of which are associated with NDD. Based on these results, we propose a novel mechanism of synaptic dysfunction, involving chronic overactivation of MAPK and impaired mGluR-LTD, shared by different pesticides which may have important implications for NDD.

In Vivo Transdermal Multi-Ion Monitoring with a Potentiometric Microneedle-Based Sensor Patch.

Microneedle sensor technology offers exciting opportunities for decentralized clinical analyses. A novel issue puts forward herein is to demonstrate the uniqueness of membrane-based microneedles to accomplish real-time, on-body monitoring of multiple ions simultaneously. The use of multi-ion detection is clinically relevant since it is expected to provide a more complete and reliable assessment of the clinical status of a subject concerning electrolyte disorders and others. We present a microneedle system for transdermal multiplexed tracing of pH, Na+, K+, Ca2+, Li+, and Cl-. The device consists of an array of seven solid microneedles externally modified to provide six indicator electrodes, each selective for a different ion, and a common reference electrode, all integrated into a wearable patch read in a potentiometric mode. We show in vitro measurements at the expected clinical levels, resulting in a fast response time, excellent reversibility and repeatability, and adequate selectivity. Close-to-Nernstian sensitivity, sufficient stability and resiliency to skin penetration guarantee the sensor's success in transdermal measurements, which we demonstrate through ex vivo (with pieces of rat skin) and in vivo (on-body measurements in rats) tests. Accuracy is evaluated by comparison with gold standard techniques to characterize collected dermal fluid, blood, and serum. In the past, interstitial fluid (ISF) analysis has been challenging due to difficult sample collection and analysis. For ions, this has resulted in extrapolations from blood concentrations (invasive tests) rather than pure measurements in ISF. The developed microneedle patch is a relevant analytical tool to address this information gap.

Diurnal Differences in Immune Response in Brain, Blood and Spleen After Focal Cerebral Ischemia in Mice.

BACKGROUND: The immune response to acute cerebral ischemia is a major factor in stroke pathobiology. Circadian biology modulates some aspects of immune response. The goal of this study is to compare key parameters of immune response during the active/awake phase versus inactive/sleep phase in a mouse model of transient focal cerebral ischemia. METHODS: Mice were housed in normal or reversed light cycle rooms for 3 weeks, and then they were blindly subjected to transient focal cerebral ischemia. Flow cytometry was used to examine immune responses in blood, spleen, and brain at 3 days after ischemic onset. RESULTS: In blood, there were higher levels of circulating T cells in mice subjected to focal ischemia during zeitgeber time (ZT)1-3 (inactive or sleep phase) versus ZT13-15 mice (active or awake phase). In the spleen, organ weight and immune cell numbers were lower in ZT1-3 versus ZT13-15 mice. Consistent with these results, there was an increased infiltration of activated T cells into brain at ZT1-3 compared with ZT13-15. CONCLUSIONS: This proof-of-concept study indicates that there are significant diurnal effects on the immune response after focal cerebral ischemia in mice. Hence, therapeutic strategies focused on immune targets should be reassessed to account for the effects of diurnal rhythms and circadian biology in nocturnal rodent models of stroke.

Functional specialization of different PI3K isoforms for the control of neuronal architecture, synaptic plasticity, and cognition.

Neuronal connectivity and activity-dependent synaptic plasticity are fundamental properties that support brain function and cognitive performance. Phosphatidylinositol 3-kinase (PI3K) intracellular signaling controls multiple mechanisms mediating neuronal growth, synaptic structure, and plasticity. However, it is still unclear how these pleiotropic functions are integrated at molecular and cellular levels. To address this issue, we used neuron-specific virally delivered Cre expression to delete either p110α or p110ß (the two major catalytic isoforms of type I PI3K) from the hippocampus of adult mice. We found that dendritic and postsynaptic structures are almost exclusively supported by p110α activity, whereas p110ß controls neurotransmitter release and metabotropic glutamate receptor-dependent long-term depression at the presynaptic terminal. In addition to these separate functions, p110α and p110ß jointly contribute to N-methyl-d-aspartate receptor-dependent postsynaptic long-term potentiation. This molecular and functional specialization is reflected in different proteomes controlled by each isoform and in distinct behavioral alterations for learning/memory and sociability in mice lacking p110α or p110ß.

Imaging Sample Acidification Triggered by Electrochemically Activated Polyaniline.

In this letter, we demonstrate 2D acidification of samples at environmental and physiological pH with an electrochemically activated polyaniline (PANI) mesh. A novel sensor-actuator concept is conceived for such a purpose. The sample is sandwiched between the PANI (actuator) and a planar pH optode (sensor) placed at a very close distance (∼0.50 mm). Upon application of a mild potential to the mesh, in contrast to previously reported acidification approaches, PANI releases a significant number of protons, causing an acid-base titration in the sample. This process is monitored in time and space by the pH optode, providing chemical imaging of the pH decrease along the dynamic titration via photographic acquisition. Acidification of samples at varying buffer capacity has been investigated: the higher the buffer capacity, the more time (and therefore proton charge) was needed to reach a pH of 4.5 or even lower. Also, the ability to map spatial differences in buffer capacity within a sample during the acid-base titration was unprecedentedly proven. The sensor-actuator concept could be used for monitoring certain analytes in samples that specifically require acidification pretreatment. Particularly, in combination with different optodes, dynamic mapping of concentration gradients will be accessible in complex environmental samples ranging from roots and sediments to bacterial aggregates.

Intradermal Glycine Detection with a Wearable Microneedle Biosensor: The First In Vivo Assay.

Glycine (GLY) is gaining importance in medical diagnoses due to its relationship with multiple physiological functions. Today, GLY is exclusively analyzed using instrumentation centralized in clinical labs, and a tangible point-of-care tool that gathers real-time data from the patient for effective and fast evaluations is lacking. Relevant clinical advances are expected as soon as the rapid provision of both punctual and continuous measurements is possible. In that context, this work presents a microneedle (MN)-based biosensor for intradermal GLY detection in interstitial fluid (ISF). The MN tip is externally tailored to detect GLY levels through the hydrogen peroxide formed in its reaction with a quinoprotein-based GLY oxidase enzyme. The analytical performance of the MN biosensor indicates a fast response time (<7 s); acceptable reversibility, reproducibility, and stability; as well as a wide linear range of response (25-600 µM) that covers the physiological levels of GLY in ISF. The MN biosensor conveniently exhibits high selectivity for GLY over other compounds commonly found in ISF, and the response is not influenced by temperature, pH, or skin insertions. Validated intradermal measurements of GLY were obtained at the in vitro (with pieces of rat skin), ex vivo (on-body tests of euthanized rats) and in vivo (on-body tests of anesthetized rats) levels, demonstrating its ability to produce accurate physiological data. The developed GLY MN biosensor is skin-wearable and provides reliable, real-time intradermal GLY measurements in ISF by means of a minimally invasive approach.