Fluid Glucose Research Articles

Flexible cellulose paper-based biosensor from inkjet printing for non-invasive glucose monitoring

Wearable glucose sensors have attracted significant attention for enabling non-invasive blood glucose measurement without discomfort and risk of infection. However, it is a challenge to simultaneously realize wearable adaptability, biodegradability, and excellent sensing performance. Herein, a cellulose paper-based non-invasive biosensor relying on reverse iontophoresis was designed to detect glucose in interstitial fluid (ISF), and two different enzyme immobilization strategies have been compared. The results showed inkjet-printed cellulose paper-based biosensor (IPB) performances better than the drop-coated cellulose paper-based biosensor (DPB). IPB has twice response current more than DPB in detection range (0–10 mM). In sensitivity, IPB is 1.170 μA/mM three times higher than the DPB (0.376 μA/mM). Besides, IPB's electron-transfer resistance (Rct) is 7.27 kΩ smaller than DPB (Rct = 10.51 kΩ) about 30 %. More importantly, IPB exhibited a good reproducibility (RSD, 4.82 %), which was much less than DPB (RSD, 18.35 %). Furthermore, the IPB realizes noninvasive continuous glucose monitoring over 6 h in volunteer experiments with great analytical performance comparable to commercial devices (Pearson correlation 0.732). Cellulose paper-based glucose sensors with inkjet printing provide non-invasive access to statistically significant diagnostic information, simple and cost-effective, which promotes the application of flexible, wearable, degradable bioelectrodes in continuous glucose monitoring at home, providing a concept for full integration in a compact and portable way in the future.

Predictive role of PAR and LAR in refractory suppurative meningitis in infants

BackgroundMeningitis can be caused by a variety of pathogenic microorganisms, which can lead to higher mortality and disability rates. However, the clinical manifestations of suppurative meningitis are often atypical in infants and young children, which makes early clinical diagnosis difficult.PAR and LAR are considered as a novel inflammatory biomarker and have been applied in tumors, IgA nephropathy, sepsis.ObjectiveTo investigate the application of platelet/albumin (PAR) and lactate dehydrogenase/albumin (LAR) in refractory suppurative meningitis in infants.MethodsThe relevant clinical data of 107 children with suppurative meningitis were retrospectively analyzed, and were divided into common group (82 cases) and refractory group (25 cases) according to the severity of the disease according to the relevant clinical consensus. The relevant clinical data and laboratory examination of the children in the two groups were compared. The diagnostic value of PAR and LAR in children with refractory suppurative meningitis was analyzed and multivariate Logistic regression analysis was performed.ResultThe PAR of children with suppurative meningitis in refractory group was lower than that in common group (P < 0.05), while LAR was higher than that in common group (P < 0.05). Meanwhile, multivariate Logistic regression analysis showed that LAR and cerebrospinal fluid glucose ≤ 1.5mmo/L were risk factors for poor prognosis (OR > 1, P < 0.05). PAR was a protective factor (OR < 1, P < 0.05).ConclusionPAR and LAR can be used for early diagnosis of refractory suppurative meningitis in children as protective and risk factors, respectively.

P-223 Follicular fluid from women stimulated with hMG protocol displays altered energy metabolism and this impacts embryo morphokinetics

Abstract Study question Does different type of ovarian stimulation affect follicle metabolism? Summary answer Patients stimulated hMG-only show increased levels of glucose and MDA in follicular fluid and longer Cc3 embryo time compared to patients stimulated rFSH and hMG. What is known already Oocyte growth and maturation strongly rely on energy metabolism. However, there is a notable lack of studies examining the influence of ovarian stimulation protocols on individual follicular fluid. While certain studies indicate changes in genes associated with glucose metabolism in patients subjected to different protocols, there remains a need for prospective studies in this field. Study design, size, duration This is a single-center prospective analysis from March 2022 to August 2022 including 20 patients. From the total, 14 were stimulated with rFSH + hMG and 6 with hMG only. A total of 81 embryos were submitted to morphokinetics analysis. Patients with Polycystic Ovary Syndrome (PCOS), Ovarian insufficiency, Endometriosis in stages III and IV, and patients who have already undergone other attempts at the clinic were excluded. Participants/materials, setting, methods Patients were firstly assessed by age, body mass index (BMI), and dosage of stimulation hormones. Puncture of follicles was performed individually after system wash and only follicular fluid (FF) with no visible blood contamination were submitted for analysis. FFs were analyzed for glucose, lactate, insulin (specific fluorometric assays), and MDA (important oxidative stress marker). Morphokinetics analyses were performed for all available embryos from day 0 until day 6. Main results and the role of chance Body Mass Index (BMI) and ages were similar among the categories (p = 0.388 and p = 0.373, respectively). FSH dosage used in both groups was not different (p = 0.85) but LH used was higher in patients treated with human menopausal gonadotropin (hMG) (p = 0.002). Women whose treatment was hMG presented more glucose in FF (p = 0.02) and MDA (p = 0.02) while no differences were observed for insulin and lactate content (p = 0.57 and p = 0.72 respectively). There was a significant increase of 3º Cell Cicle (Cc3) time of embryos from women treated with hMG only. Taken together, these data suggest that hMG is modifying the glucose metabolism by interrupting glycolysis in the oocyte, resulting in a higher amount in FF, which increases Malondialdehyde (MDA) levels. Considering that oocytes from women treated with hMG only had an altered metabolic profile, this could impact the further embryo development, with consequences specifically at the time of the embryonic metabolic shift. Limitations, reasons for caution The limited number of patients is a limitation of the study and the lack of standardization in the use of trigger, despite of not having significant difference. Wider implications of the findings Understanding the implication of hormones in follicular microambient might help individualization of hormones usage and improve the outcomes of IVF treatment. Trial registration number 44895621.1.0000.5594

Кореляція маркерів материнського та плодового запалення

Fetal inflammatory response syndrome (IFRS) is an inadequate reaction of the fetal immune system to the inflammatory process in the placenta, which is accompanied by an increase in neonatal mortality and morbidity. Aim - to assess the dependence of IFRS on the markers of the inflammatory process of the mother in premature births in different gestational periods to determine the date of delivery. Materials and methods. 405 mothers with premature singleton deliveries and their premature newborns were examined. The Spearman correlation method was used to calculate the relationship between IL-6 content in the umbilical cord blood of a newborn and laboratory markers of maternal inflammation in peripheral blood (containing leukocytes and rod-shaped neutrophils, C-reactive protein, procalcitonin, pro-inflammatory interleukins), amniotic fluid (glucose, secretory inhibitor of leukocyte proteinase (SILP) and pro-inflammatory interleukins) and cervical mucus (pro-inflammatory interleukins). Results. Between the indicators of the mother's peripheral blood circulation and the value of IL-6, only a moderate connection was found, and the content of IL-6 in the amniotic fluid shows a strong correlation with the concentration of IL-6 in the umbilical cord blood of extremely premature newborns. For SILP, a strong correlation with the laboratory marker SFZV was found. A negative correlation with IL-6 of umbilical cord blood was found in cervical mucus for SILP. Signs of infection in the newborn show a strong dependence on the concentration of C-reactive protein and procalcitonin in the peripheral blood of the mother, but this was not found for extremely premature newborns. A strong correlation was found between the concentration of glucose in the amniotic fluid and signs of infection in premature infants in both gestational categories. Conclusions. Among indicators of peripheral blood circulation of a pregnant woman, none shows a strong correlation with IFRS. The concentration of SILP in the amniotic fluid has a strong correlation with signs of fetal inflammation, regardless of gestational age. The content of SILP in the cervical mucus has a strong negative correlation with the criterion of IFRS in preterm infants against the background of intact fetal membranes. A strong correlation between the glucose content in the amniotic fluid and signs of infection in the premature infant was revealed. For extremely premature newborns, no indicator of the mother's peripheral blood correlates with signs of infection. The research was carried out in accordance with the principles of the Declaration of Helsinki. The research protocol was approved by the Local Ethics Committee of the institution mentioned in the work. Informed consent of the women was obtained for the research. The authors declare no conflict of interest.

Changes in adiponectin levels of subclinical ketosis cows and their effects on steroid hormone secretion and proliferation in follicular granulosa cells

In dairy cows, the occurrence of subclinical ketosis (SCK) is particularly high during early lactation. Previously, we documented alterations in the abundance of adiponectin (ADPN) in anestrus cows with SCK in comparison to cows in estrus. In the present study, 60 cows were divided into two groups: control (C, n = 30) and SCK (n = 30). Based on cow’s estrus situation in two group at 55–60 days postpartum, 15 anestrus SCK cows and estrus cows were designated the SCK-A group and C-E group, respectively. The SCK-A group had downregulated serum and follicular fluid ADPN levels compared with the C-E group. The serum ADPN level was positively correlated with the insulin level and follicle growth rate, and there was a positive correlation between ADPN and glucose in the follicular fluid. Primary culture of dairy cow granulosa cells (GCs) was established to observe the effect of low glucose (Glu) and/or ADPN on GCs cyclins and proteins important for steroid synthesis. The results showed that the addition of 1 µg/mL ADPN alleviated the negative effects of low Glu treatment on the proliferation of GCs and the expression of steroid secretion related protein proteins. Treatment with LY294002 (PI3K inhibitor) four experimental GCs groups: control (0 µg/mL ADPN), 1 µg/mL ADPN, LY294002 inhibitor, and 1 µg/mL ADPN+LY294002. The results showed that ADPN promotes the secretion of steroid hormones by GCs through the PI3K–AKT. In summary, ADPN plays a crucial role in ameliorating postpartum anestrus in dairy cows with SCK.

Defect-rich cypress-leaf-like Cu2+1O@NiF for high-performance non-invasive glucose detection with low detection limit

Non-invasive detection of body fluid glucose concentration is of great significance in the diagnosis and treatment of diabetes, which poses a new challenge to the reduction of the detection limit of glucose sensors. In this work, a novel non-enzymatic glucose sensor (defect-rich cypress-leaf-like Cu2+1O@NiF) was proposed by rapid electrodeposition of cypress-leaf-like Cu2+1O on the surface of nickel foam (NiF) substrate. Due to the high electrochemical active surface area and abundant defects of cypress-leaf-like Cu2+1O providing more catalytic active sites, the prepared non-enzymatic sensor has an ultra-low detection limit (0.9 nM), high sensitivity (88,419.4 μA∙mM−1∙cm−2 (1 nM-0.5 μM) and 2095.5 μA∙mM−1∙cm−2 (1 μM-4.33 mM)) and wide linear range (1 nM-4.33 mM) with good selectivity, reproducibility and stability. Furthermore, the obtained sensors exhibited high detection stability, accuracy and recovery for glucose detection of human body fluid samples, which means that the defect-rich cypress-leaf-like Cu2+1O@NiF electrode is an ideal candidate for non-invasive glucose sensors.

Differences in Cerebrospinal Fluid Glucose Levels in Meningitis Patients Based on Examination Time: A Single Center Observational Study at Dr. M. Djamil General Hospital, Padang, Indonesia

Differences in Cerebrospinal Fluid Glucose Levels in Meningitis Patients Based on Examination Time: A Single Center Observational Study at Dr. M. Djamil General Hospital, Padang, Indonesia

Remote-Controlled Sensing and Drug Delivery via 3D-Printed Hollow Microneedles.

Remote health monitoring and treatment serve as critical drivers for advancing health equity, bridging geographical and socioeconomic disparities, ensuring equitable access to quality healthcare for those in underserved or remote regions. By democratizing healthcare, this approach offers timely interventions, continuous monitoring, and personalized care independent of one's location or socioeconomic status, thereby striving for an equitable distribution of health resources and outcomes. Meanwhile, microneedle arrays (MNAs), revolutionize painless and minimally invasive access to interstitial fluid for drug delivery and diagnostics. This paper introduces an integrated theranostic MNA system employing an array of colorimetric sensors to quantitatively measure -pH, glucose, and lactate, alongside a remotely-triggered system enabling on-demand drug delivery. Integration of an ultrasonic atomizer streamlines the drug delivery, facilitating rapid, pumpless, and point-of-care drug delivery, enhancing system portability while reducing complexities. An accompanying smartphone application interfaces the sensing and drug delivery components. Demonstrated capabilities include detecting pH (3 to 8), glucose (up to 16mm), and lactate (up to 1.6mm), showcasing on-demand drug delivery, and assessing delivery system performance via a scratch assay. This innovative approach confronts drug delivery challenges, particularly in managing chronic diseases requiring long-term treatment, while also offering avenues for non-invasive health monitoring through microneedle-based sensors.

#2103 Accuracy of a continuous glucose monitor in people with diabetes on peritoneal dialysis

Abstract Background and Aims Globally 40% of people receiving peritoneal dialysis (PD) have a diagnosis of diabetes. Good glycaemic control can by complicated by the obligate glucose load associated with PD. Monitoring and treatment of people with diabetes (PwD) on PD has been limited by reduced reliability of traditional markers of glycaemia such as HbA1c in end-stage kidney disease. Continuous glucose monitors (CGMs) have been increasingly used in the care of PwD over the last 20 years. Monitors worn on the upper arm or abdomen measure glucose in interstitial fluid at regular intervals over the 24 hour period. CGMs are currently unlicensed in PD populations as they have not been tested in large scale studies. Concerns remain around accuracy in the presence of potentially interfering substances generated by the breakdown of osmotic agents used in PD fluid (e.g. Icodextrin). We aimed to assess the analytical and clinical accuracy of the FreeStyle Libre(FSL) CGM system in PwD on maintenance PD. Method We conducted a single centre observational study of 10 PwD who had been on PD for at least 3 months. For the 10 day study period participants wore a blinded research model FSL monitor which measured interstitial glucose levels every 15 minutes. Results from the FSL were compared with; Analytical accuracy was assessed using three methods; Clinical accuracy was assessed using the Parkes consensus error grid to assign each pair of readings to one of five risk zones and quantify the clinical implications of any difference between the two measurements. The International Organisation for Standardisation guidelines stipulates 99% of pairs should be in zones A and B, denoting little or no effect on clinical actions. Results Of 11 recruited participants, 10 completed the 10 day study period resulting in 76 paired CGM-YSI measurements and 375 paired CGM-CBG measurements. 7 participants were on APD and 3 on CAPD. All participants were prescribed a PD regime that included one daily dwell with Icodextrin. The aggregate MARD was 9.4% (95% CI 7.9, 10.4) for CGM-YSI matched pairs and 17.6% (95% CI 17, 19.3) for CGM-CBG matched pairs. Spearman's r was 0.94 (p &amp;lt; 0.0001) for CGM-YSI and 0.89 (p &amp;lt; 0.0001) for CGM-CBG. From Bland-Altman analysis, the systematic error of the CGM compared with YSI and CBG was −0.81 mmol/l (SD 0.81) and −1.6 mmol/l (SD 1.9) respectively. Parkes consensus error grid analysis showed that compared with YSI and CBG respectively, 100% and 99.9% of sensor values were in the clinically acceptable zones A and B (Fig. 1). Conclusion We have demonstrated satisfactory performance of the FSL monitoring system by both analytical and clinical metrics in this cohort of PD patients using treatment regimens including Icodextrin based fluids. CGMs provide much more information for the PwD and their clinical care team compared with random CBGs (which in themselves have been shown to exhibit significant between user variability) and time averaged markers such as HbA1c. They allow detection of asymptomatic hypoglycaemia and direct monitoring of the systemic effects of any change to the PD prescription resulting in a larger or smaller glucose load. These results should be reassuring for clinicians wishing to utilise the greater depth of information provided by CGMs to improve clinical care for their patients with diabetes on PD.

Smart Contact Lens for Colorimetric Visualization of Glucose Levels in the Body Fluid.

Frequent blood glucose monitoring is a crucial routine for diabetic patients. Traditional invasive methods can cause discomfort and pain and even pose a risk of infection. As a result, researchers have been exploring noninvasive techniques. However, a limited number of products have been developed for the market due to their high cost. In this study, we developed a low-cost, highly accessible, and noninvasive contact lens-based glucose monitoring system. We functionalized the surface of the contact lens with boronic acid, which has a strong but reversible binding affinity to glucose. To achieve facile conjugation of boronic acid, we utilized a functional coating layer called poly(tannic acid). The functionalized contact lens binds to glucose in body fluids (e.g., tear) and releases it when soaked in an enzymatic cocktail, allowing for the glucose level to be quantified through a colorimetric assay. Importantly, the transparency and oxygen permeability of the contact lens, which are crucial for practical use, were maintained after functionalization, and the lenses showed high biocompatibility. Based on the analysis of colorimetric data generated by the smartphone application and ultraviolet-visible (UV-vis) spectra, we believe that this contact lens has a high potential to be used as a smart diagnostic tool for monitoring and managing blood glucose levels.

A Study of Serum to Pleural Fluid Albumin Gradient in Differentiation of Exudative and Transudative Pleural Effusion in Comparison to Light’s Criteria

Pleural effusion is the accumulation of fluid between the parietal and visceral pleura called the pleural cavity. It can occur by itself or can be the result of surrounding parenchymal diseases like infection, malignancy or inflammatory conditions. Pleural effusion is one of the major causes of pulmonary mortality and morbidity. Both the visceral and the parietal pleura play an important role in fluid homeostasis in the pleural space. Pleural effusions develop when there is excess hydrostatic pressure in the pulmonary capillaries, when fluid removal is impaired by compromised lymphatic drainage or when protein and cell rich fluid enters the pleural space through leaky capillary and pleural membranes. Pleural fluid is classified as a transudate or exudate based on modified Light’s criteria, proposed by Light et al., in 1972 which has been the standard differentiation method. It is considered an exudative effusion if at least one of the criteria is met:  Pleural fluid protein/serum protein ratio of more than 0.5  Pleural fluid lactate dehydrogenase (LDH)/serum LDH ratio of more than 0.6  Pleural fluid LDH is more than two-thirds of the upper limits of normal laboratory value for serum LDH. Commonly performed tests on the pleural fluid to determine etiology are a measurement of fluid pH, fluid protein, albumin and LDH, fluid glucose, fluid triglyceride, fluid cell count differential, fluid gram stain and culture and fluid cytology.

The significance of precise diabetes diagnosis: a case of euglycemic diabetic ketoacidosis induced by the introduction of empagliflozin with simultaneous reduction of insulin dosage

Euglycemic diabetic ketoacidosis (euDKA) is a rare but severe metabolic complication of diabetes mellitus characterised by elevated anion gap metabolic acidosis despite normal or mildly elevated blood glucose levels. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have emerged as effective antidiabetic medications, yet their use is associated with an increased risk of euDKA, especially when coupled with insulin dose reduction. We present the case of a 50-year-old male with a 20-year history of diabetes mellitus, initially managed with insulin and metformin, who developed euDKA following the introduction of empagliflozin and sitagliptin alongside a reduction in insulin therapy. Despite normoglycaemia the patient exhibited symptoms of ketoacidosis, including chronic fatigue, polydipsia, and polyuria. Diagnostic workup revealed metabolic acidosis, elevated inflammatory markers, acute kidney injury and ketonuria. Subsequent specialised laboratory tests confirmed type 1 diabetes mellitus (T1DM) with the presence of anti-glutamic acid decarboxylase (anti-GAD) antibodies and the absence of C-peptide secretion. Management involved fluid therapy, intravenous insulin and glucose administration. This case underscores the diagnostic challenges of euDKA and emphasises the importance of differentiating between T1DM and T2DM, as management strategies vary significantly. Patient education on insulin therapy and injection techniques is crucial to prevent complications such as improper insulin delivery and dose reduction, which can precipitate euDKA. In conclusion, clinicians should be vigilant for euDKA in patients on SGLT2 inhibitors, particularly when insulin dose reduction is involved. Comprehensive patient education and accurate differentiation between diabetes types are essential for timely diagnosis and optimal management, thereby reducing the risk of severe complications.

Validation of a rapid technique of blood gas analysis for cerebrospinal fluid (CSF) lactate and glucose

Validation of a rapid technique of blood gas analysis for cerebrospinal fluid (CSF) lactate and glucose

Vagal nerve and sympathetic nerve activity in response to glucagon-like peptide-1 (GLP-1) receptor stimulation in conscious rats

GLP-1 (Glucagon-Like Peptide-1) is a type of gastrointestinal hormone that plays an integral role in regulating glucose homeostasis and appetite control. GLP-1 receptors are expressed throughout the body, and it has been suggested that GLP-1 can be detected by vagal afferent nerve activity, leading to changes in sympathetic nerve activity. However, the details of the effects of GLP-1 receptor stimulation on autonomic nerve activity have not been reported. Therefore, this study investigated the effects of different sites of GLP-1 receptor stimulation on autonomic nerve activity by administering GLP-1 receptor agonists via three routes: intravenous (IV), intraportal vein (iport), and intraperitoneal (iperi). Male Wistar rats were chronically implanted with electrodes, catheters for measuring cervical vagal activity, renal and lumbar sympathetic nerve activity, electroencephalogram, electromyogram, electrocardiogram, arterial pressure, sensors for tissue fluid glucose concentration, and catheters for drug administration in the vein, portal vein, and abdominal cavity. Exendin-4, a GLP-1 receptor agonist, was administered to conscious rats via one of the following routes: intravenous, intra-portal vein, or intra-abdominal. Cervical vagal activity was increased in all routes of Exendin-4 administration. Renal sympathetic nerve activity was rapidly decreased by Exendin-4 administration and gradually recovered to pre-administration levels. There were no significant differences in renal sympathetic nerve activity among the different routes of Exendin-4 administration. On the other hand, lumbar sympathetic nerve activity increased slowly after Exendin-4 administration through the iperi and iport routes, while it decreased initially, then gradually increased following administration through the IV route. These results demonstrate that stimulation of GLP-1 receptors by Exendin-4 increases vagal nerve activity, decreases renal sympathetic nerve activity, and produces regionally different responses in lumbar sympathetic nerve activity depending on the site of stimulation. JST (JPMJMS2023). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Practical considerations for continuous glucose monitoring in elite athletes with type 1 diabetes mellitus: A narrative review.

Type 1 diabetes mellitus (T1DM) refers to a metabolic condition where a lack of insulin impairs the usual homeostatic mechanisms to control blood glucose levels. Historically, participation in competitive sport has posed a challenge for those with T1DM, where the dynamic changes in blood glucose during exercise can result in dangerously high (hyperglycaemia) or low blood glucoses (hypoglycaemia) levels. Over the last decade, research and technological development has enhanced the methods of monitoring and managing blood glucose levels, thus reducing the chances of experiencing hyper- or hypoglycaemia during exercise. The introduction of continuous glucose monitoring (CGM) systems means that glucose can be monitored conveniently, without the need for frequent fingerpick glucose checks. CGM devices include a fine sensor inserted under the skin, measuring levels of glucose in the interstitial fluid. Readings can be synchronized to a reader or mobile phone app as often as every 1-5min. Use of CGM devices is associated with lower HbA1c and a reduction in hypoglycaemic events, promoting overall health and athletic performance. However, there are limitations to CGM, which must be considered when being used by an athlete with T1DM. These limitations can be addressed by individualized education plans, using protective equipment to prevent sensor dislodgement, as well as further research aiming to: (i) account for disparities between CGM and true blood glucose levels during vigorous exercise; (ii) investigate the effects of temperature and altitude on CGM accuracy, and (iii) explore of the sociological impact of CGM use amongst sportspeople without diabetes on those with T1DM.

Nutrient deprivation induces mouse embryonic diapause mediated by Gator1 and Tsc2.

Embryonic diapause is a special reproductive phenomenon in mammals that helps embryos to survive various harsh stresses. However, the mechanisms of embryonic diapause induced by the maternal environment is still unclear. Here, we uncovered that nutrient deficiency in uterine fluid was essential for the induction of mouse embryonic diapause, shown by a decreased concentration of arginine, leucine, isoleucine, lysine, glucose and lactate in the uterine fluid of mice suffering from maternal starvation or ovariectomy. Moreover, mouse blastocysts cultured in a medium with reduced levels of these six components could mimic diapaused blastocysts. Our mechanistic study indicated that amino acid starvation-dependent Gator1 activation and carbohydrate starvation-dependent Tsc2 activation inhibited mTORC1, leading to induction of embryonic diapause. Our study elucidates the essential environmental factors in diapause induction.

A wearable sensor device based on screen-printed chip with biofuel cell-driven electrochromic display for noninvasive monitoring of glucose concentration

Wearable flexible sensor devices have the characteristics of lightweight and miniaturization. Currently, power supply and detection components limit the portability of wearable flexible sensor devices. Meanwhile, conventional liquid electrolytes are unsuitable for the integration of sensing devices. To address these constraints, wearable biofuel cells and flexible electrochromic displays have been introduced, which can improve integration with other devices, safety, and color-coded display data. Meanwhile, electrode chips prepared through screen printing technology can further improve portability. In this work, a wearable sensor device with screen-printed chips was constructed and used for non-invasive detection of glucose. Agarose gel electrolytes doped with PDA-CNTs were prepared, and the mechanical strength and moisture retention were significantly improved compared with traditional gel electrolytes. Glucose in interstitial fluid was non-invasive extracted to the skin surface using reverse iontophoresis. As a biofuel for wearable biofuel cells, glucose drives self-powered sensor and electrochromic display to produce color change, allowing for visually measurement of glucose levels in body fluids. Accurate detection results can be visualized by reading the RGB value with a cell phone.

Non-invasive measurements of blood glucose levels by time-gating mid-infrared optoacoustic signals

Non-invasive glucose monitoring (NIGM) represents an attractive alternative to finger pricking for blood glucose assessment and management of diabetes. Nevertheless, current NIGM techniques do not measure glucose concentrations in blood but rely on indirect bulk measurement of glucose in interstitial fluid, where glucose is diluted and glucose dynamics are different from those in the blood, which impairs NIGM accuracy. Here we introduce a new biosensor, termed depth-gated mid-infrared optoacoustic sensor (DIROS), which allows, for the first time, non-invasive glucose detection in blood-rich volumes in the skin. DIROS minimizes interference caused by the stratum corneum and other superficial skin layers by time-gating mid-infrared optoacoustic signals to enable depth-selective localization of glucose readings in skin. In measurements on the ears of (female) mice, DIROS displays improved accuracy over bulk-tissue glucose measurements. Our work demonstrates how signal localization can improve NIGM accuracy and positions DIROS as a holistic approach, with high translational potential, that addresses a key limitation of current NIGM methods.

An Artificial Enzyme: How Nanoconfinement Allows the Selective Electrochemical Detection of Glucose Directly in Whole Blood

AbstractNanoparticles that catalyze biochemically relevant reactions are promoted as alternative enzymes. The application of such artificial enzymes is severely restricted by poor selectivity in biological fluids; mainly because the reactions occur at active sites on the exterior surface of the nanoparticle. Enzymes in contrast typically have their active sites down a nanoconfined substrate channel where the reaction occurs in different solution conditions to bulk solution which aids in achieving selectivity for the substrate. Herein the same 3D structure of enzymes is mimicked in nanoparticles to allow selective reactions in biological fluids. This is achieved using a gold nanoparticle coated in a conducting mesoporous carbon shell where isolated nanochannels lead to the gold surface. It can detect glucose in whole blood with no interference from other species. This is achieved by electrochemically pulsing the artificial enzymes to generate the locally required alkalinity for an effective electrocatalytic reaction in the nanochannels, as well as expelling fouling agents that will otherwise passivate the electrocatalytic reaction. The artificial enzymes are shown to be capable of detecting glucose in biological fluids, without loss of signal, for several months. This study shows how nanoconfinement in nanoparticles can be exploited to potentially allow a broad range of species to be selectively detected in biological fluids with stability that can exceed that of enzymes.

Ag-carbon dots with peroxidase-like activity for colorimetric and SERS dual mode detection of glucose and glutathione

Currently, nanozymes have made important research progress in the fields of catalysis, biosensing and tumor therapy, but most of nanozymes sensing systems are single-mode detection, which are easily affected by environment and operation, so it is crucial to construct nanozymes sensing system with dual-signal detection to obtain a more stable and reliable performance. In this paper, Ag-carbon dots (Ag-CDs) bifunctional nanomaterials were synthesized using carbon dots as reducing agent and protective agent by a facile and green one-step method. A simple and sensitive colorimetric-SERS dual-mode sensing platform was constructed for the detection of glucose and glutathione(GSH) in body fluids by taking advantage of good peroxidase-like and SERS activities of Ag-CDs. Ag-CDs catalyzes H2O2 to hydroxyl radicals(•OH), which oxidized TMB to form ox-TMB blue solution with characteristic absorption peak at 652 nm and Raman characteristic peak at 1607 cm−1. Ag-CDs sensing method exhibited high performance for glucose and GSH with detection limits for colorimetric and SERS as low as 11.30 μM and 3.54 μM, 0.38 μM and 0.24 μM respectively (S/N = 3). In addition, Ag-CDs have good stability and uniformity, ensuring long-term applicability of catalytic system. This colorimetric-SERS dual-mode sensing platform can be used for the determination of glucose and GSH in saliva and urine, and has the advantages of simple, low cost, rapid, and high accuracy, which has a potential application prospect in biosensor and medical research.