Interstitial Fluid Levels Research Articles

A high-performance wearable microneedle sensor based on a carboxylated carbon nanotube-carbon nanotube composite electrode for the simultaneous detection of uric acid and dopamine

Uric acid (UA) and dopamine (DA) are crucial biomarkers in the human body. However, there is limited research on detecting UA or DA in subcutaneous interstitial fluid (SISF), and no studies on their simultaneous detection in SISF. Here, we developed an electrochemical microneedle sensor based on the carboxylated carbon nanotubes/multiwalled carbon nanotubes (CCNT/CNT) composite electrode for the simultaneous detection of UA and DA. Highly carboxylated CCNT was prepared and mixed with CNT and organosilicon-modified acrylic resin to form the CCNT/CNT composite. The carboxyl functional groups of CCNT enhance the electrode’s adsorption of UA and DA, while CNT improves electron conduction. The sensor achieves a wide linear detection range for UA (5–600 μM) with high sensitivity (7.13 μA μM−1 cm−2) and linearity (R2 = 0.994), as well as a wide linear range for DA (2–200 μM) with high sensitivity (13.31 μA μM−1 cm−2) and linearity (R2 = 0.994). The sensor achieved simultaneous detection of DA and UA in artificial interstitial fluid (ISF), with sensitivity and linearity remaining nearly unchanged compared to that in PBS, and is not affected by high levels of ascorbic acid (AA). Finally, the sensor successfully detected changes in UA levels in ISF of subjects before and after alcohol consumption in vivo, demonstrating its practical application capabilities. This study presents a practical strategy for detecting human biomarkers characterized by low cost, easy fabrication and excellent performance of electrode materials, and a well-designed microneedle sensor preparation scheme, making it highly promising for further research extension.

Flexible plasmonic microneedle array-based SERS sensor for pH monitoring of skin interstitial fluid

Interstitial fluid (ISF) is a prevalent accessible and information-rich biofluid, and monitoring pH level of interstitial fluid plays a crucial role in the physiological health assessment. However, facile extraction of ISF and sensitive detection of pH is still a great challenge. Herein, a flexible plasmonic microneedle array (PMNA)-based SERS sensor was developed for facile and sensitive pH monitoring of skin ISF. The flexible microneedle arrays were fabricated by norland optical adhesive 65 (NOA65), and coated with pH-sensitive 4-Mercaptobenzoic acid (4-MBA)-labeled silver nanoparticles (Ag NPs) by electrostatic assembly. The proposed flexible PMNA-based SERS sensor has a good linear response in the pH range of 5 to 9 which covers the normal pH level in skin interstitial fluid. The ISF extracted from porcine skin was chosen as the test model, and the pH levels detected by the PMNA-based SERS sensors were well consistent with the theoretical results. Besides, the proposed flexible SERS sensors show good mechanical robustness, sensing stability, and biocompatibility before and after skin insertion, which can be a potential analytical tool for practical detection of pH levels in ISF and provide technical support for SERS-based wearable biosensing.

Development of an electrochemical biosensor for non-invasive cholesterol monitoring via microneedle-based interstitial fluid extraction

In this study, we present the development of an innovative electrochemical biosensor integrated into a microneedle-based system for non-invasive and sensitive quantification of cholesterol levels in interstitial fluid (ISF). The biosensor employs a graphene-based electrode with a polyelectrolyte interlayer to immobilize cholesterol oxidase (ChOx), enabling selective cholesterol detection. Graphene oxide is electrochemically reduced to form a conductive layer, and PANI is chosen as the optimal polyelectrolyte for ChOx immobilization. The biosensor's performance is thoroughly evaluated, demonstrating excellent sensitivity, stability, and selectivity. Furthermore, the biosensor is successfully applied to skin-mimicking agarose gel and porcine skin, showcasing its potential for real-world interstitial fluid extraction and cholesterol monitoring. The integrated microneedle-based system offers a promising approach for non-invasive monitoring of cholesterol levels, with implications for personalized healthcare diagnostics.

Phase II study shows potential benefit of adenoviral vascular endothelial growth factor C (VEGF-C) and lymph node transfer in lymphedema.

Breast cancer-related lymphedema (BCRL) is a common complication lacking medical treatment. Lymfactin® is an adenovirus type 5-based gene therapy and prolymphangiogenic growth factor vector that induces vascular endothelial growth factor C (VEGF-C) expression. Our aim was to evaluate the therapeutic effect of Lymfactin® with vascularized lymph node transfer (VLNT). This Phase II, double-blind, placebo-controlled, randomized multicenter study evaluated the efficacy and safety of Lymfactin® in combination with VLNT. The primary endpoints were edema volume, quality of life (LyQoLI), and lymphoscintigraphy. All adverse events were recorded. A mixed model of repeated measures analysis of covariance was performed. This study was a continuation of a previous Phase I Lymfactin® study. Thirty-nine patients with BCRL were recruited between June 2018 and December 2019 and randomized to receive either Lymfactin® (n = 20) or placebo (n = 19). The primary endpoints showed a positive effect of VLNT in both groups compared to the baseline, but without statistical differences between groups at 12 months. Additionally, greater improvements were observed in the tissue dielectric constant ratios measuring skin interstitial fluid levels in the Lymfactin® group compared to the placebo group (p = 0.020). No differences in adverse events were detected between the groups. This study was one of the few studies to objectively show a positive effect of VLNT in a prospective clinical multicenter setting. It was also the first-ever randomized prospective clinical study showing a quantitatively positive effect of a medical therapy on the edema of lymphedema although failing to show differences between groups in primary outcome measures.

Characterization of Inflammatory Mediators and Metabolome in Interstitial Fluid Collected with Dermal Open Flow Microperfusion before and at the End of Dupilumab Treatment in Atopic Dermatitis.

Dupilumab is a monoclonal antibody approved for the treatment of atopic dermatitis (AD); however, its effects on molecular, cellular, and immunological levels remain to be elucidated. In this study, blood and dermal interstitial fluid (ISF) from nonlesional (NL) and lesional (L) skin were collected from eight patients with moderate to severe AD, before (visit 2-v2) and at the end of a 16-week treatment with dupilumab (visit 10-v10). Clinical treatment effect was demonstrated by significantly decreased AD severity scores at the end of treatment. At v10 versus v2, the percentages of CD4+ interleukin-producing cells showed a decreasing trend in ISF L and NL, unbound IL-4 levels in plasma were increased, IL-5 levels in ISF L reduced, and levels of factors involved in anti-inflammatory pathways and re-epithelization increased. At v2, ISF L showed that AD lesions might have altered amino acid pathways and lipid signaling compared to ISF NL. At v10, ISF L exhibited raised levels of long- and very-long-chain fatty acids and lipids compared to v2. Furthermore, dupilumab administration caused reduced expression of miR-155-5p and miR-378a-3p in ISF L. In conclusion, results from the present study provided novel knowledge by linking local immune and metabolic alterations to AD pathogenesis and treatment response.

Plasma and interstitial fluid antibiotic levels of subcutaneously implanted compounded florfenicol calcium sulfate beads in New Zealand White rabbits (Oryctolagus cuniculus).

To determine antibiotic levels in plasma and interstitial fluid (ISF) after SC placement of compounded florfenicol (FF) calcium sulfate beads (CSBs) in New Zealand White rabbits (Oryctolagus cuniculus). 6 juvenile female rabbits (n = 5 treatment and 1 control). An ultrafiltration probe and CSBs were placed SC in 6 rabbits (n = 5 for FF CSBs and 1 for control CSBs). Plasma (3, 6, 12, 24, and 48 hours and 7, 14, and 21 days) and ISF (daily for 21 days) samples were collected, and FF was measured by HPLC for pharmacokinetic analysis. Hematology, biochemistry, and histopathology were assessed. Means ± SD for the area under the curve, maximum concentration, time of maximum concentration, terminal half-life, and mean residence time to the last data point for plasma and ISF were 16.63 ± 8.16 and 17,902 ± 7,564 h·µg/mL, 0.79 ± 0.38 and 245 ± 223 µg/mL, 2.90 ± 0.3 and 59 ± 40 hours, 30.81 ± 16.9 and 27.3 ± 9.39 hours, 23.4 ± 10 and 73.7 ± 13 hours, respectively. Plasma FF was < 2 µg/mL at all time points. The ISF FF remained > 8 μg/mL for 109.98 to 231.58 hours. One rabbit death occurred during treatment, but the cause of death was undetermined. Local tissue inflammation was present, but no clinically significant systemic adverse effects were found on hematology, biochemistry, or histopathology in the remaining rabbits. Florfenicol CSBs maintained antibiotic concentrations in ISF at levels likely to be effective against bacteria sensitive to > 8 µg/mL for 5 to 10 days while maintaining low (< 2 µg/mL) plasma levels. Florfenicol CSBs may be effective for local antibiotic treatment in rabbit abscesses.

Corn-inspired high-density plasmonic metal-organic frameworks microneedles for enhanced SERS detection of acetaminophen

Effective monitoring of acetaminophen (APAP) dosage is crucial for preventing antipyretic abuse, ensuring therapeutic efficacy, and minimizing toxic effects. However, existing self-monitoring methods are limited. In this study, we designed a plasmonic microneedle (MN) sensor for real-time nondestructive monitoring of acetaminophen levels in dermal interstitial fluid (ISF) by employing a handheld Raman spectrometer. The fabricated MN sensor incorporated a high-density plasmonic MOFs known as HDPM, which unique structure of large specific surface area, specific pore structure as well as high density gold nanospheres packing enabled the excellent performance of selective ISF drug enrichment and surface-enhanced Raman scattering (SERS). The maximum electric field enhancement factor of the HDPM nanostructure could be calculated as 5.73 × 107. The developed HDPM@MNs was characterized with a core-shell type “soft on the outside and rigid on the inside” structure, which exhibited sufficient hardness and flexibility to penetrate the dermal tissue with little damage, and robust SERS enhancement effect in APAP detection without any interfering peaks. Through a hydrogel drug simulation experiment, the sensor demonstrated robust capabilities for acetaminophen enrichment and monitoring, exhibiting excellent stability and repeatability. The quantitative detection window spanned from 1 to 100 μM, with a low detection limit reaching 0.45 μM. Furthermore, by monitoring the concentration of acetaminophen in the interstitial fluid of rat skin at different doses and for different administration times, the HDPM@MNs can be used to determine the pharmacokinetics of acetaminophen in rats and the physiological characteristics associated with various dosage regimens. This work not only holds promise for drug monitoring but also provides a novel approach for nondestructive monitoring of other crucial low-abundance physiological markers.

Sleep-wake body temperature regulates tau secretion in mice and correlates with CSF and plasma tau in humans.

The sleep-wake cycle regulates interstitial fluid and cerebrospinal fluid (CSF) tau levels in both mouse and human by mechanisms that remain unestablished. Here, we reveal a novel pathway by which wakefulness increases extracellular tau levels in mouse and humans. In mice, higher body temperature (BT) associated with wakefulness and sleep deprivation increased CSF tau. In vitro, wakefulness temperatures upregulated tau secretion via a temperature-dependent increase in activity and expression of unconventional protein secretion pathway-1 components, namely caspase-3-mediated C-terminal cleavage of tau (TauC3), and membrane expression of PIP2 and syndecan-3. In humans, the increase in both CSF and plasma tau levels observed post-wakefulness correlated with BT increase during wakefulness. Our findings suggest sleep-wake variation in BT may contribute to regulating extracellular tau levels, highlighting the importance of thermoregulation in pathways linking sleep disturbance to neurodegeneration, and the potential for thermal intervention to prevent or delay tau-mediated neurodegeneration.

GH and IGF-1 in skin interstitial fluid and blood are associated with heat loss responses in exercising young adults.

Sweat glands and cutaneous vessels possess growth hormone (GH) and insulin-like growth factor 1 (IGF-1) receptors. Here, we assessed if exercise increases GH and IGF-1 in skin interstitial fluid, and whether baseline and exercise-induced increases in GH and IGF-1 concentrations in skin interstitial fluid/blood are associated with heat loss responses of sweating and cutaneous vasodilation. Sixteen young adults (7 women) performed a 50-min moderate-intensity exercise bout (50% VO2peak) during which skin dialysate and blood samples were collected. In a sub-study (n = 7, 4 women), we administered varying concentrations of GH (0.025-4000ng/mL) and IGF-1 (0.000256-100µg/mL) into skin interstitial fluid via intradermal microdialysis. Sweat rate (ventilated capsule) and cutaneous vascular conductance (CVC) were measured continuously for both studies. Exercise increased sweating and CVC (both P < 0.001), paralleled by increases of serum GH and skin dialysate GH and IGF-1 (all P ≤ 0.041) without changes in serum IGF-1. Sweating was positively correlated with baseline dialysate and serum GH levels, as well as exercise-induced increases in serum GH and IGF-1 (all P ≤ 0.044). Increases in CVC were not correlated with any GH and IGF-1 variables. Exogenous administration of GH and IGF-1 did not modulate resting sweat rate and CVC. (1) Exercise increases GH and IGF-1 levels in the skin interstitial fluid, (2) exercise-induced sweating is associated with baseline GH in skin interstitial fluid and blood, as well as exercise-induced increases in blood GH and IGF-1, and (3) cutaneous vasodilation during exercise is not associated with GH and IGF-1 in skin interstitial fluid and blood.

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.

Regulation of extracellular progranulin in the medial prefrontal cortex

AbstractBackgroundLoss‐of‐function mutations in progranulin (GRN) are a major genetic cause of frontotemporal dementia (FTD). Progranulin is a secreted protein that is trafficked to lysosomes, where it promotes lysosomal function. Progranulin also exerts neurotrophic and anti‐inflammatory effects, some of which may be mediated by extracellular signaling. Neurons and microglia express progranulin and loss of progranulin from either cell type induces FTD‐like deficits in mice. Both cell types secrete progranulin in culture, but their contribution to extracellular progranulin in the brain is unclear, as are the mechanisms regulating progranulin secretion from each cell type. In this study, we used microdialysis to gain insight into the contribution of neurons and microglia to extracellular progranulin in the medial prefrontal cortex (mPFC), a region that degenerates in FTD and develops impaired dendritic arborization in progranulin‐insufficient mice.MethodPolyethylene probes (2 mm, 1000 kDa cut‐off) were implanted in mouse mPFC and perfused with artificial cerebrospinal fluid containing 4% BSA using a push‐pull pump system (Atmos LM, Amuza). Progranulin levels in interstitial fluid (ISF) were measured by ELISA (Adipogen).ResultGrn+/– mice exhibited a roughly 50% decrease in ISF progranulin versus wild‐type, which was similar to the reduction of progranulin in mPFC tissue. In wild‐type mice, inducing cellular depolarization with KCl (100 mM) increased ISF progranulin, but stimulating synaptic activity with picrotoxin (100 μM) or NMDA (50 μM) did not. Inducing systemic inflammation with LPS (10 mg/kg i.p.) increased ISF progranulin to around 200% of baseline at eight hours after injection. Analysis of ISF progranulin from microglial progranulin knockout mice (Cx3Cr1‐Cre‐ER:Grnfl/fl) revealed a nearly 50% reduction in ISF progranulin compared to Cre– littermates, which was a larger reduction than observed in mPFC tissue. Ongoing studies are analyzing ISF progranulin in neuronal progranulin knockout mice (CamKII‐Cre:Grnfl/fl).ConclusionOur findings indicate that inflammation increases ISF progranulin in the mPFC and that nearly half of the extracellular progranulin in the mPFC may originate from microglia. In contrast, synaptic activity does not significantly increase ISF progranulin in the mPFC. Ongoing studies will investigate the contribution of neurons to extracellular progranulin in the mPFC.

0085 Peripheral glucose metabolism bidirectionally modulates sleep in a model of Alzheimer's disease

Abstract Introduction Metabolic impairments and sleep disruptions are both recognized as modifiable risk factors in the development of Alzheimer’s disease (AD). A bidirectional relationship exists between sleep and AD where pathology can disrupt sleep, but sleep disturbances can also increase AD-related pathology. This results in a feed-forward cycle of disease progression and further sleep impairments. Sleep fragmentation and poor sleep quality can also cause glucose intolerance and insulin resistance. However, it remains unclear if peripheral metabolic dysfunction alone can impair sleep, particularly in the context of AD-related pathology. Therefore, the goal of this study was to establish mechanisms connecting peripheral metabolic and sleep disruptions and identify potential therapeutic targets for mitigating AD risk. Methods We implanted biosensors measuring interstitial fluid (ISF) levels of glucose and lactate, biomarkers of cerebral metabolism and neuronal activity, respectively, directly into the hippocampus of wildtype and APP/PS1 mice, a model of amyloid-beta (Aβ) overexpression. Biosensors were paired with cortical EEG and EMG recordings for simultaneous sleep/wake analysis. To understand the relationship between metabolic dysfunction and sleep, we altered the peripheral metabolic environment using two paradigms: an acute high-fat, high-sugar diet (HF/HSD) and a pharmacological metabolic rescue. Results We found short-term HF/HSD exposure was sufficient to disrupt ISF glucose and lactate diurnal rhythms, independent of changes to pathology burden. Moreover, we found significant sleep disruptions, particularly decreased delta power, indicating slow wave sleep impairments. These findings were exacerbated in mice with Aβ pathology who have disrupted metabolic and sleep functioning at baseline. Conversely, we found normalizing peripheral glucose tolerance in mice with Aβ pathology was sufficient to rescue impaired ISF glucose and lactate rhythms. We also saw a restoration of normal sleep-wake patterns, specifically within slow wave activity. Conclusion We found modulating peripheral glucose metabolism can bidirectionally alter sleep, particularly slow wave sleep, independent of changes in Aβ burden. This indicates sleep as a mediator in the relationship between metabolic impairments and AD pathophysiology. While impaired sleep increases AD risk, improved sleep slows pathology accumulation. Therefore, this study demonstrates targeting peripheral glucose regulation is a potential avenue for early AD intervention and risk mitigation. Support (if any) F31-AG066302, R01-AG068330, P30-AG072947

Porous Colorimetric Microneedles for Minimally Invasive Rapid Glucose Sampling and Sensing in Skin Interstitial Fluid.

Though monitoring blood glucose (BG) is indispensable for regulating diabetes, the frequent pricking of the finger by the commonly used fingertip blood collection causes discomfort and poses an infection risk. Since glucose levels in skin interstitial fluid (ISF) correlate with blood glucose levels, monitoring glucose in the skin ISF can be a viable alternative. With this rationale, the present study developed a biocompatible porous microneedle capable of rapid sampling, sensing, and glucose analysis in ISF in a minimally invasive manner, which can improve patient compliance and detection efficiency. The microneedles contain glucose oxidase (GOx) and horseradish peroxidase (HRP), and a colorimetric sensing layer containing 3,3',5,5'-tetramethylbenzidine (TMB) is on the back of the microneedles. After penetrating rat skin, porous microneedles harvest ISF rapidly and smoothly via capillary action, triggering the production of hydrogen peroxide (H2O2) from glucose. In the presence of H2O2, HRP reacts with TMB contained in the filter paper on the back of microneedles, causing an easily visible color shift. Further, a smartphone analysis of the images quickly quantifies glucose levels in the 50-400 mg/dL range using the correlation between color intensity and glucose concentration. The developed microneedle-based sensing technique with minimally invasive sampling will have great implications for point-of-care clinical diagnosis and diabetic health management.

KATP channels are necessary for glucose-dependent increases in amyloid-β and Alzheimer's disease-related pathology.

Elevated blood glucose levels, or hyperglycemia, can increase brain excitability and amyloid-β (Aβ) release, offering a mechanistic link between type 2 diabetes and Alzheimer's disease (AD). Since the cellular mechanisms governing this relationship are poorly understood, we explored whether ATP-sensitive potassium (KATP) channels, which couple changes in energy availability with cellular excitability, play a role in AD pathogenesis. First, we demonstrate that KATP channel subunits Kir6.2/KCNJ11 and SUR1/ABCC8 were expressed on excitatory and inhibitory neurons in the human brain, and cortical expression of KCNJ11 and ABCC8 changed with AD pathology in humans and mice. Next, we explored whether eliminating neuronal KATP channel activity uncoupled the relationship between metabolism, excitability, and Aβ pathology in a potentially novel mouse model of cerebral amyloidosis and neuronal KATP channel ablation (i.e., amyloid precursor protein [APP]/PS1 Kir6.2-/- mouse). Using both acute and chronic paradigms, we demonstrate that Kir6.2-KATP channels are metabolic sensors that regulate hyperglycemia-dependent increases in interstitial fluid levels of Aβ, amyloidogenic processing of APP, and amyloid plaque formation, which may be dependent on lactate release. These studies identify a potentially new role for Kir6.2-KATP channels in AD and suggest that pharmacological manipulation of Kir6.2-KATP channels holds therapeutic promise in reducing Aβ pathology in patients with diabetes or prediabetes.

Microneedle‐Integrated Device for Transdermal Sampling and Analyses of Targeted Biomarkers

Currently available point‐of‐care systems for body fluid collection exhibit poor integration with sensors. Herein, the design of a disposable device for interstitial fluid (ISF) extraction as well as glucose, lactate, and potassium ion (K+) monitoring is reported on. It is minimally invasive and appropriate for single use, minimizing the risk of infection to the user. This microscale device contains a 3D‐printed cap‐like structure with a four‐by‐four microneedle (MN) array, bioreceptor‐modified carbon fiber (CF)‐sensing surface, and negative pressure convection technology. These features are incorporated within a compact, self‐contained, and manually operated microscale device, which is capable of withdrawing ≈3.0 μL of ISF from the skin. MN arrays applied with an upward driving force may increase the ISF flow rate. Moreover, functionalized CF working electrodes (WE1, WE2, WE3) are shown to selectively detect lactate, glucose, and K+ with high sensitivities of 0.258, 0.549, and 0.657 μA μm−1 cm−2 and low detection limits of 0.01, 0.080, 0.05 μm, respectively. Ex vivo testing on porcine skin is used to detect the ISF levels of the biomarkers. The microscale device can be a replacement for current point‐of‐care diagnostic approaches.

Dose-Dependent Effects in Plasma Oncotherapy: Critical In Vivo Immune Responses Missed by In Vitro Studies.

Cold atmospheric plasma (CAP) generates abundant reactive oxygen and nitrogen species (ROS and RNS, respectively) which can induce apoptosis, necrosis, and other biological responses in tumor cells. However, the frequently observed different biological responses to in vitro and in vivo CAP treatments remain poorly understood. Here, we reveal and explain plasma-generated ROS/RNS doses and immune system-related responses in a focused case study of the interactions of CAP with colon cancer cells in vitro and with the corresponding tumor in vivo. Plasma controls the biological activities of MC38 murine colon cancer cells and the involved tumor-infiltrating lymphocytes (TILs). In vitro CAP treatment causes necrosis and apoptosis in MC38 cells, which is dependent on the generated doses of intracellular and extracellular ROS/RNS. However, in vivo CAP treatment for 14 days decreases the proportion and number of tumor-infiltrating CD8+T cells while increasing PD-L1 and PD-1 expression in the tumors and the TILs, which promotes tumor growth in the studied C57BL/6 mice. Furthermore, the ROS/RNS levels in the tumor interstitial fluid of the CAP-treated mice are significantly lower than those in the MC38 cell culture supernatant. The results indicate that low doses of ROS/RNS derived from in vivo CAP treatment may activate the PD-1/PD-L1 signaling pathway in the tumor microenvironment and lead to the undesired tumor immune escape. Collectively, these results suggest the crucial role of the effect of doses of plasma-generated ROS and RNS, which are generally different in in vitro and in vivo treatments, and also suggest that appropriate dose adjustments are required upon translation to real-world plasma oncotherapy.

Physiological β-amyloid clearance by the liver and its therapeutic potential for Alzheimer’s disease

Cerebral amyloid-β (Aβ) accumulation due to impaired Aβ clearance is a pivotal event in the pathogenesis of Alzheimer's disease (AD). Considerable brain-derived Aβ is cleared via transporting to the periphery. The liver is the largest organ responsible for the clearance of metabolites in the periphery. Whether the liver physiologically clears circulating Aβ and its therapeutic potential for AD remains unclear. Here, we found that about 13.9% of Aβ42 and 8.9% of Aβ40 were removed from the blood when flowing through the liver, and this capacity was decreased with Aβ receptor LRP-1 expression down-regulated in hepatocytes in the aged animals. Partial blockage of hepatic blood flow increased Aβ levels in both blood and brain interstitial fluid. The chronic decline in hepatic Aβ clearance via LRP-1 knockdown specific in hepatocytes aggravated cerebral Aβ burden and cognitive deficits, while enhancing hepatic Aβ clearance via LRP-1 overexpression attenuated cerebral Aβ deposition and cognitive impairments in APP/PS1 mice. Our findings demonstrate that the liver physiologically clears blood Aβ and regulates brain Aβ levels, suggesting that a decline of hepatic Aβ clearance during aging could be involved in AD development, and hepatic Aβ clearance is a novel therapeutic approach for AD.

Optical determination of lithium therapeutic levels in micro-volumes of interstitial fluid.

Long-term management of bipolar disorder (BD), characterized by mood fluctuating between episodes of mania and depression, involves the regular taking of lithium preparations as the most reliable mood stabilizer for bipolar patients. However, despite its effectiveness in preventing and reducing mood swings and suicidality, lithium has a very narrow therapeutic index and it is crucial to carefully monitor lithium plasma levels as concentrations >1.2 mmol/L are potentially toxic and can be fatal. Current methods of lithium therapeutic monitoring involve frequent blood tests, which have several drawbacks related to the invasiveness of the technique, comfort, cost and reliability. Dermal interstitial fluid (ISF) is an accessible and information-rich biofluid, and correlations have been found between blood and ISF levels of lithium medication. In the current study, we sought to investigate the optical determination of lithium therapeutic concentrations in samples of ISF extracted from porcine skin utilizing a microneedle-based approach. Monitoring of lithium levels in porcine ISF was achieved by employing a spectrophotometric method based on the reaction between the chromogenic agent Quinizarin and lithium. The resulting spectra show spectral variations which relate to lithium concentrations of lithium in samples of porcine ISF with a coefficient of determination (R2 ) of 0.9. This study has demonstrated successfully that therapeutic levels of lithium in micro-volumes of porcine ISF can be measured with a high level of accuracy utilizing spectroscopic techniques. The results support the future development of a miniaturized and minimally-invasive device for lithium monitoring in bipolar patients.

A paper-based colorimetric method for monitoring of lithium therapeutic levels.

Lithium remains the "gold standard" for both acute and maintenance treatment of bipolar disorder (BD), a serious life-long condition characterised by recurrent episodes of depressed and manic mood states. However, lithium has a very narrow therapeutic range (0.4-1.2 mmol L-1) and despite its effectiveness in preventing and reducing mood swings and suicidality, it is a potentially hazardous drug. While it is crucial to carefully monitor lithium plasma levels, the current techniques of lithium monitoring are cumbersome and require frequent blood tests with the consequent discomfort which results in patients evading treatment. Therefore, development of low-cost and facile lithium detection techniques that can be translated into point-of-care devices for personal monitoring will be a major advance in the management of BD. In the current study, we present colorimetric determination of lithium therapeutic levels utilizing test paper strips, based on its reaction with the chromogenic agent Quinizarin. Exposure of Quinizarin-dipped test papers to samples of interstitial fluid (ISF) or dH2O spiked with therapeutic concentrations of lithium resulted in colour changes that were monitored using optical spectroscopy. The acquired spectra from the test papers show spectral variations which are related to lithium concentrations in spiked samples of dh2O and artificial ISF with a coefficient of determination (R2) of 0.9 and 0.8, respectively. Altogether, the spectrophotometric and colorimetric analyses demonstrated strong correlations between the observed colour changes and the concentrations of lithium present in the sample. Therefore, this study has demonstrated that Quinizarin-treated cellulose-based papers are suitable for the precise detection of changes in lithium therapeutic levels. This method is simple and very convenient and serves as a foundation for the future development of a paper-based colorimetric sensor for monitoring of lithium therapeutic levels in ISF and other non-invasive biological fluids.

Wearable microneedle array-based sensor for transdermal monitoring of pH levels in interstitial fluid

Microneedle-based wearable sensors offer an alternative approach to traditional invasive blood-based health monitoring and disease diagnostics techniques. Instead of blood, microneedle-based sensors target the skin interstitial fluid (ISF), in which the biomarker type and concentration profile resemble the one found in the blood. However, unlike blood, interstitial fluid does not have the same pH-buffering capacity causing deviation of pH levels from the physiological range. Information about the skin ISF pH levels can be used as a biomarker for a wide range of pathophysiological conditions and as a marker for the calibration of a wearable sensor. The ISF pH can significantly affect the detection accuracy of other biomarkers as it influences enzyme activity, aptamer affinity, and antibody-antigen interaction. Herein, we report the fabrication of a high-density polymeric microneedle array-based (PMNA) sensing patch and its optimization for the potentiometric transdermal monitoring of pH levels in ISF. The wearable sensor utilizes a polyaniline-coated PMNA having a density of ∼10,000 microneedles per cm2, containing individual microneedles with a height of ∼250 μm, and a tip diameter of ∼2 μm. To prevent interference from other body fluids like sweat, an insulating layer is deposited at the base of the PMNA. The wearable pH sensor operates from pH 4.0 to 8.6 with a sensitivity of 62.9 mV per pH unit and an accuracy of ±0.036 pH units. Furthermore, testing on a mouse demonstrates the ability of the PMNA to provide a real-time reading of the transdermal pH values. This microneedle-based system will significantly contribute to advancing transdermal wearable sensors technology, simplifying the fabrication process, and improving the cost-effectiveness of such devices.