Colorimetric detection of electrolyte ions in blood based on biphasic microdroplet extraction.

BACKGROUND: Timely diagnosis and prevention of diseases require rapid and sensitive detection of biomarkers from blood samples without external interference. Abnormal electrolyte ion levels in the blood are closely linked to various physiological disorders, including hypertension. Therefore, accurate, interference-free, and precise measurement of electrolyte ion concentrations in the blood is particularly important. RESULTS: In this work, a colorimetric sensor based on a biphasic microdroplet extraction is proposed for the detection of electrolyte ions in the blood. This sensor employs mini-pillar arrays to facilitate contact between adjacent blood microdroplets and organic microdroplets serving as sensing phases, with any color changes being monitored through a smartphone's colorimetric software. The sensor is highly resistant to interference and does not require pre-treatment of the blood samples. Remarkably, the sensor exhibits exceptional reliability and stability, allowing for rapid enrichment and detection of K+, Na+, and Cl- in the blood within 10 s (Cl-), 15 s (K+) and 40 s (Na+) respectively. SIGNIFICANCE: The colorimetric sensor based on biphasic microdroplet extraction offers portability due to its compact size and ease of operation without the need for large instruments. Additionally, it is location-independent, making it a promising tool for real-time biomarker detection in body fluids such as blood.

Fully Integrated Multiplexed Wristwatch for Real-Time Monitoring of Electrolyte Ions in Sweat.

Considerable progress has already been made in sweat sensors based on electrochemical methods to realize real-time monitoring of biomarkers. However, realizing long-term monitoring of multiple targets at the atomic level remains extremely challenging, in terms of designing stable solid contact (SC) interfaces and fully integrating multiple modules for large-scale applications of sweat sensors. Herein, a fully integrated wristwatch was designed using mass-manufactured sensor arrays based on hierarchical multilayer-pore cross-linked N-doped porous carbon coated by reduced graphene oxide (NPCs@rGO-950) microspheres with high hydrophobicity as core SC, and highly selective monitoring simultaneously for K+, Na+, and Ca2+ ions in human sweat was achieved, exhibiting near-Nernst responses almost without forming an interfacial water layer. Combined with computed tomography, solid-solid interface potential diffusion simulation results reveal extremely low interface diffusion potential and high interface capacitance (598 µF), ensuring the excellent potential stability, reversibility, repeatability, and selectivity of sensor arrays. The developed highly integrated-multiplexed wristwatch with multiple modules, including SC, sensor array, microfluidic chip, signal transduction, signal processing, and data visualization, achieved reliable real-time monitoring for K+, Na+, and Ca2+ ion concentrations in sweat. Ingenious material design, scalable sensor fabrication, and electrical integration of multimodule wearables lay the foundation for developing reliable sweat-sensing systems for health monitoring.

Electrolyte disturbances in patients hospitalized for COVID-19 infection: An observational study.

There are multiple mechanisms by which The Coronavirus-19 (COVID-19) infection can cause electrolyte abnormalities, which may not be the case for bacterial causes of pneumonia. This study aimed to assess the differences in electrolyte levels between patients suffering from COVID-19 and bacterial pneumonia. This is an original, retrospective study. Two cohorts of hospitalized patients were included, 1 suffering from COVID-19 and the other from bacterial pneumonia. Their day 1 and day 3 levels of sodium, potassium, magnesium, and phosphorus, as well as their outcomes, were extracted from the charts. Statistical analysis was subsequently performed. Mean admission levels of sodium, potassium, phosphorus, and magnesium were 135.64 ±â€…6.13, 4.38 ±â€…0.69, 3.53 ±â€…0.69, and 2.03 ±â€…0.51, respectively. The mean day 3 levels of these electrolytes were 138.3 ±â€…5.06, 4.18 ±â€…0.59, 3.578 ±â€…0.59, and 2.11 ±â€…0.64, respectively. Patients suffering from bacterial pneumonia were significantly older (N = 219, mean = 64.88 ±â€…15.99) than patients with COVID-19 pneumonia (N = 240, mean = 57.63 ±â€…17.87). Bacterial pneumonia group had significantly higher serum potassium (N = 211, mean = 4.51 ±â€…0.76), and magnesium (N = 115, mean = 2.12 ±â€…0.60) levels compared to COVID-19 group (N = 227, mean = 4.254 ±â€…0.60 for potassium and N = 118, mean = 1.933 ±â€…0.38 for magnesium). Only magnesium was significantly higher among day 3 electrolytes in the bacterial pneumonia group. No significant association between electrolyte levels and outcomes was seen. We found that COVID-19 patients had lower potassium and magnesium levels on admission, possibly due to the effect of COVID-19 on the renin-angiotensin-aldosterone system as well as patient characteristics and management. We did not find enough evidence to recommend using electrolyte levels as a determinator of prognosis, but more research is needed.

Study of Serum Electrolytes (Sodium and Potassium) Abnormalities in Acute Stroke.

Stroke is the common cause of death and disability worldwide, as well as in Bangladesh. Serum electrolytes abnormalities or dyselectrolytaemia is one of the major acute complications of stroke. Dyselectrolytaemia or serum electrolytes (sodium and potassium) abnormalities are more common in patients with acute stroke that can be easily measured. The study was planned to find out the serum electrolytes (sodium and potassium) abnormalities in acute stroke patients. This cross-sectional study was conducted in the Department of Neurology and Medicine, Mymensingh Medical College and Hospital from January 2019 to June 2020. Total 84 purposively selected patients with acute strokes were evaluated following informed written consent. Diagnosis was confirmed by neuroimaging of brain. Moreover, serum electrolytes level was measured for each patient. Data were collected by interviews, clinical examinations & laboratory investigations of the patients using a case record form and analysis was carried out by the help of SPSS 25.0. Mean age of the patients with acute strokes were 57.65±15.79 years. About two thirds (60.7%) of the patients were male and the remaining (39.3%) were female. Sodium imbalances were observed in 32.2% and potassium imbalances in 25.0% cases. About 66.7% haemorrhagic strokes patients and 42.2% ischaemic strokes patients had dyselectrolytaemia (p<0.05). More than twenty eight percent (28.6%) of all stroke patients had hyponatraemia, which was more common (35.9%) among haemorrhagic strokes patients (p<0.05). Of all stroke patients 21.4% had hypokalaemia, which was more common (28.2%) in haemorrhagic strokes patients (p<0.05). This study reveals that, serum electrolytes (sodium and potassium) abnormalities are more common in haemorrhagic than ischaemic strokes, which is mainly hyponatraemia and hypokalaemia.

Relationship between electrolytes and glycated hemoglobin among diabetic patients with poor adherence to antidiabetic medications: a cross-sectional study.

Introduction: type 2 Diabetes mellitus is a chronic metabolic disease with devastating effects on patients and results in numerous healthcare challenges in terms of its management and the cost burden among the affected. Successful management involves maintaining optimal glycemic control to prevent complications, with adherence to antidiabetic medications playing a crucial role in achieving this objective. Additionally, maintaining a healthy electrolyte balance is key for overall well-being and physiological function. However, the correlation between glycated hemoglobin and electrolyte balance remains under investigated, particularly in patients with suboptimal adherence. The aim of this research was to study the relationship between glycated hemoglobin and electrolytes among diabetic patients with poor adherence to antidiabetic medications. Methods: this study was conducted at Samburu County Referral Hospital in Samburu County, Kenya. We employed a descriptive cross-sectional design focusing on adult diabetic patients aged 18 years and above who had visited the diabetic clinic over a three-month period. To evaluate their adherence levels, we employed a Morisky Medication Adherence Scale-8. Seventy-two diabetic patients who got adherence level scores of < 6 were categorized as having low adherence and their blood samples were collected for measuring glycated hemoglobin levels and electrolytes levels particularly potassium, sodium, calcium, magnesium, phosphorus and chloride. Relationship between electrolytes and glycated hemoglobin among diabetic patients with poor adherence to antidiabetics was determined using Karl Pearson correlation. Results: among the study participants, the lowest hemoglobin A1C (HbA1c) level recorded was 5.1% while the highest was 15.0% and the majority (41.7%) fell within the HbA1c range of 5-7%. A high proportion of individuals (58.3%) with poor adherence to antidiabetics had elevated HbA1c levels, indicating poor glycemic control. The correlations observed between glycated hemoglobin and electrolytes which included magnesium, sodium, chloride, calcium and phosphorus was r= -0.07, -0.32, -0.05 -0.24 and -0.04 respectively. Conclusion: this study concluded that there is a relationship between electrolytes and glycated hemoglobin among diabetic patients with poor adherence to antidiabetics. A statistically significant negative correlation was observed between glycated hemoglobin and calcium level (r=-0.2398 P ≤0.05) and also sodium (r=-0.31369 P≤0.05). A negative correlation (P≥0.05) was observed between phosphorus, magnesium, chloride and potassium with HbA1c levels though not statistically significant.

Recent Advances in Endocrine and Neuroendocrine Systems.

The endocrine and neuroendocrine systems exert powerful and broad control over the regulation of homeostasis in animals. Secreted hormones play significant roles in lifetime-related events such as germ cell development, sexual maturation, development, metamorphosis, aging, feeding, and energy metabolism. Additionally, hormones, particularly sex steroid hormones, are involved in reproduction, including sexual behavior and dimorphism. Changes in body color protect against external enemies, and circadian rhythms direct physiology and behaviors in synchrony with light and dark cycles. Water and electrolyte metabolism are essential for survival in land or seawater. Both aquatic and terrestrial animals have developed a variety of endocrine and neuroendocrine systems that exquisitely manage water and electrolyte metabolism to support survival. In zoological science, many animal species are investigated for their unique life history phenomena, and many researchers bring original and unique research approaches to understand these phenomena. Exploring such a variety of animal species leads to an understanding of diversity and unity, and contributes to the development of comparative endocrinology. This Special Issue contains 15 papers focusing on the endocrine mechanisms involved in the aforementioned life phenomena.

Risk stratification and predictive modeling of postoperative delirium in chronic subdural hematoma.

Background- Postoperative delirium is a common complication associated with the elderly, causing increased morbidity and prolonged hospital stay. However, its risk factors in chronic subdural hematoma patients have not been well studied. Methods- A total of 202 consecutive patients with chronic subdural hematoma at Peking University Third Hospital between January 2018 and January 2023 were enrolled. Various clinical indicators were analyzed to identify independent risk factors for postoperative delirium using univariate and multivariate regression analyses. Delirium risk prediction models were developed as a nomogram and a Markov chain. Results- Out of the 202 patients (age, 71 (IQR, 18); female-to-male ratio, 1:2.7) studied, 63 (31.2%) experienced postoperative delirium. Univariate analysis identified age (p < 0.001), gender (p = 0.014), restraint belt use (p < 0.001), electrolyte imbalance (p < 0.001), visual analog scale score (p < 0.001), hematoma thickness (p < 0.001), midline shift (p < 0.001), hematoma side (p = 0.013), hematoma location (p = 0.018), and urinal catheterization (p = 0.028) as significant factors. Multivariate regression analysis confirmed the significance of restraint belt use (B = 7.657, p < 0.001), electrolyte imbalance (B = -3.993, p = 0.001), visual analog scale score (B = 2.331, p = 0.016), and midline shift (B = 0.335, p = 0.007). Hematoma thickness and age had no significant impact. Conclusion- Increased midline shift and visual analog scale scores, alongside restraint belt use and electrolyte imbalance elevate delirium risk in chronic subdural hematoma surgery. Our prediction models may offer reference value in this context.

Artificial Funnel Nanochannel Device Emulates Synaptic Behavior.

Creating artificial synapses that can interact with biological neural systems is critical for developing advanced intelligent systems. However, there are still many difficulties, including device morphology and fluid selection. Based on Micro-Electro-Mechanical System technologies, we utilized two immiscible electrolytes to form a liquid/liquid interface at the tip of a funnel nanochannel, effectively enabling a wafer-level fabrication, interactions between multiple information carriers, and electron-to-chemical signal transitions. The distinctive ionic transport properties successfully achieved a hysteresis in ionic transport, resulting in adjustable multistage conductance gradient and synaptic functions. Notably, the device is similar to biological systems in terms of structure and signal carriers, especially for the low operating voltage (200 mV), which matches the biological neural potential (∼110 mV). This work lays the foundation for realizing the function of iontronics neuromorphic computing at ultralow operating voltages and in-memory computing, which can break the limits of information barriers for brain-machine interfaces.

[Biological characteristics and osteogenic differentiation of magnesium-doped nanoporous titanium coating].

PURPOSE: Bioactive magnesium ions were successfully incorporated into the nanoporous titanium base coating by micro-arc oxidation(MAO), and its physical properties and osteogenic effects were explored. METHODS: Non-magnesium-containing and magnesium-containing titanium porous titanium coatings(MAO, MAO-mg) were prepared by changing the composition of MAO electrolyte and controlling the doping of magnesium in porous titanium coatings. The samples were characterized by scanning electron microscope (SEM), roughness, contact angle and energy dispersive X-ray spectrometer (EDS). Mg2+ release ability of magnesium-doped nanoporous titanium coatings was determined by inductively coupled plasma/optical emission spectrometer(ICP-OES). The structure of the cytoskeleton was determined by live/dead double staining, CCK-8 detection of material proliferation-toxicity, and staining of ß-actin using FITC-phalloidin. The effects of the coating on osteogenic differentiation in vitro were determined by alizarin red (ARS), alkaline phosphatase (ALP) staining and real-time polymerase chain reaction (qRT-PCR). SPSS 25.0 software package was used for statistical analysis. RESULTS: The MAO electrolyte with magnesium ions did not change the surface characteristics of the porous titanium coating. Each group prepared by MAO had similar microporous structure(P＞0.05). There was no significant difference in surface roughness and contact angle between MAO treatment group (MAO, MAO-mg)(P＞0.05), but significantly higher than that of Ti group (P＜0.05). With the passage of cell culture time, MAO-mg group promoted cell proliferation (P＜0.05). MAO-mg group was significantly higher than other groups in ALP and ARS staining. The expression of Runx2 mRNA (P＜0.05), ALP(P＜0.05) and osteocalcin OCN(P＜0.05) in MAO-mg group was significantly higher than that in Ti and MAO groups. CONCLUSIONS: MAO successfully prepared magnesium-containing nanoporous titanium coating, and showed a significant role in promoting osteogenic differentiation.

Del nido cardioplegia in adults: a retrospective observational study in comparison to modified St. Thomas cardioplegia in cardiac surgery.

BACKGROUND: St. Thomas cardioplegia is commonly administered to adults, yet repeated dosing at brief intervals is required. Del Nido's cardioplegic solution provides a prolonged duration of safe myocardial arrest, yet it was primarily intended for pediatric cardiac surgery. Recently, there has been an increasing interest in using Del Nido's in adults; this might be due to its ease of administration and extended re-dosing intervals. This study contrasted Del Nido's to modified St. Thomas cardioplegia in adults. METHODS: This study was conducted on 200 patients. Troponin-T was the primary outcome within the first 24 and 48 h post-surgery. Cardiopulmonary bypass time, cross-clamp time, intraoperative use of inotropic support, defibrillator and/or intra-aortic balloon were the secondary outcomes of the study. RESULTS: There was a significant reduction in post-operative Troponin-T levels in the first 24 and 48 h within Del Nido's group compared to the modified St. Thomas group. The cross-clamp and cardiopulmonary bypass times were also found to be lower within Del Nido's group. CONCLUSION: This study has demonstrated a significant reduction in early postoperative Troponin-T levels as well as operative times favoring Del Nido's in adults.

Electrochemical Characterization of Diffusion in Polymeric vs. Monomeric Solvents.

Polymer electrolyte was used as a medium for testing the performance of microband electrodes under conditions of linear diffusion. Cyclic voltammetry (CV) and chronoamperometry (CA) experiments were performed in a highly viscous medium, where diffusion rates are much slower than in fluid solutions. The log i vs. log v (CV) or log i vs. log t (CA) relationships with the current equation confirmed the existence of such conditions, yielding slope values that were lower than the expected 0.5. This could indicate an impure linear diffusion profile, i.e., some contribution from radial diffusion (edge effects). However, the desired value of 0.5 was obtained when performing these tests in monomeric solvents of similar viscosities, such as glycerol or propylene glycol. These results led to the conclusion that the current equations, which are based on Fick's laws, may not be applicable for polymer electrolytes, where various obstructions to free diffusion result in a more complicated process than for monomeric solvents.

Comparison of modified Del Nido and Custodiol® cardioplegia in minimally invasive mitral valve surgery.

OBJECTIVES: In this study, we evaluated if modified Del Nido cardioplegia delivers comparable cardiac protection in comparison to Custodiol® in patients undergoing isolated minimally invasive mitral valve repair. METHODS: From January 2018 to October 2021, all patients undergoing non-emergent isolated minimally invasive mitral valve repair were included in this study. The cardioplegia was chosen at the surgeons' discretion. The primary end points of this study were peak postoperative cardiac enzyme levels. Secondary end points were in-hospital mortality, hospital stay, occurrence of cardiac arrhythmias, pacemaker implantations, postoperative lactate and sodium levels and postoperative incidence of renal failure requiring dialysis. RESULTS: A total of 355 patients were included in this study. The mean age of patients was 57. After propensity score matching, a total of 156 pairs were identified. There was no difference in cross-clamp time between both groups. Postoperative creatine kinase levels were higher in patients receiving Custodiol on the 1st and 2nd postoperative days. Creatine kinase isoenzyme MB levels were higher in patients receiving Custodiol on the 2nd postoperative day (0.5 ± 0.2 vs 0.4 ± 0.1 µmol/l s; P < 0.001). Postoperative Troponin T concentrations were similar between both groups. Maximum lactate concentrations were higher in patients receiving Custodiol on the day of surgery (2.4 ± 1.9 vs 2.0 ± 1.1 mmol/l; P = 0.04). The overall hospital stay was longer in patients receiving Del Nido cardioplegia (10.6 ± 3.2 vs 8 ± 4.1 days; P < 0.01). CONCLUSIONS: Modified Del Nido cardioplegia based on Ionosteril® solution offers equivalent protection compared to Custodiol for isolated minimally invasive mitral valve repair.

Adaptively resettable microfluidic patch for sweat rate and electrolytes detection.

Skin-interfaced microfluidic patch has become a reliable device for sweat collection and analysis. However, the intractable problems of emptying the microchannel for reuse, and the channel's volumetric capacity limited by the size of the patch, directly hinder the practical application of sweat sensors. Herein, we report an adaptively resettable microfluidic sweat patch (Art-Sweat patch) capable of continuously monitoring both sweat rate (0.2-4.0 µL min-1) and total ionic charge concentration (10-200 mmol L-1). We develop a platform with a vertical and horizontal microchannel combined strategy, enabling repeatedly filling sweat and emptying the microchannel for autonomously resetting and detecting. The variation in the emptied volume is designed to be adaptively identified by the sensor, resulting in enhanced stability and an enlarged volumetric capacity of over 300 µL. By integrating with self-designed wireless transmission modules, the proposed Art-Sweat patch shows product-level wearability and high performance in monitoring variations in regional sweat rate and concentration for hydration status assessment.

Hypophosphatemia after Start of Medical Nutrition Therapy Indicates Early Refeeding Syndrome and Increased Electrolyte Requirements in Critically Ill Patients but Has No Impact on Short-Term Survival.

Refeeding syndrome (RFS) is a potentially life-threatening complication in malnourished (critically ill) patients. The presence of various accepted RFS definitions and the inclusion of heterogeneous patient populations in the literature has led to discrepancies in reported incidence rates in patients requiring treatment at an intensive care unit (ICU). We conducted a prospective observational study from 2010 to 2013 to assess the RFS incidence and clinical characteristics among medical ICU patients at a large tertiary center. RFS was defined as a decrease of more than 0.16 mmol/L serum phosphate to values below 0.65 mmol/L within seven days after the start of medical nutrition therapy or pre-existing serum phosphate levels below 0.65 mmol/L. Overall, 195 medical patients admitted to the ICU were included. RFS was recorded in 92 patients (47.18%). The presence of RFS indicated significantly altered phosphate and potassium levels and was accompanied by significantly more electrolyte substitutions (phosphate, potassium, and magnesium). No differences in fluid balance, energy delivery, and insulin requirements were detected. The presence of RFS had no impact on ICU length of stay and ICU mortality. Screening for RFS using simple diagnostic criteria based on serum phosphate levels identified critically ill patients with an increased demand for electrolyte substitutions. Therefore, stringent monitoring of electrolyte levels is indicated to prevent life-threatening complications.

Comparing Aluminum Concentrations in Adult and Pediatric Parenteral Nutrition Solutions: Multichamber-Bag versus Compounded Parenteral Nutrition.

Aluminum contamination in parenteral nutrition (PN) solutions can lead to neurotoxicity, reduced bone mass, and liver toxicity, especially in pediatric patients. Ingredients commonly used in PN compounding, such as vitamins, trace elements, calcium, and phosphate salts, contain significant amounts of aluminum. This study aimed to compare aluminum concentrations in multichamber-bag (MCB) and compounded PN for adults and pediatrics. A prospective study assessed aluminum concentrations in various types of MCB and compared them with compounded PN formulations with similar compositions. The types of MCB included Lipoflex® (without electrolytes), Omegaflex®, Finomel®, Smofkabiven® (with and without electrolytes), Olimel®, Clinimix®, and Numeta®. Overall, 80 aluminum determinations were included: 36 for MCBs and 44 for compounded PN. MCBs showed significantly lower aluminum concentrations than compounded PN: 11.37 (SD 6.16) vs. 21.45 (8.08) µg/L, respectively. Similar results were observed for adult (n = 40) and pediatric (n = 40) PN formulations (12.97 (7.74) vs. 20.78 (10.28) µg/L, and 9.38 (2.23) vs. 22.01 (5.82) µg/L, respectively). Significant differences were also found between MCBs depending on the manufacturing company. These findings suggest that MCBs PN offer a safer option for reducing aluminum contamination in PN. Harmonizing regulations concerning aluminum concentrations in PN solutions could help mitigate differences between PN formulations.

Ionic Distribution of an Unequal Electrolyte Near an Air/Water Surface.

The distribution of electrolytes near the air/water surface plays an essential role in many processes. While the general distribution is governed by classic Poisson-Boltzmann statistics, the analytical solution is only available for symmetric electrolytes. From the recent studies in the literature, it is evident that surface adsorption is dependent on specific ions as well as the H-bond structure at the surface. Experimental data can capture the macro properties of the surface, such as surface tension and surface potential. Yet, the underpinning mechanisms behind this experimental macro-observation remain unclear. To address the challenge, we developed a framework combining experimental studies and numerical calculations. The model was developed for electrolytes with unequal cationic and anionic charges. The asymmetric model was successfully applied to describe the surface charge of MgCl 2 aqueous solution. The results can be explained by the role of cationic size and charge on the surface layer.

The Effects of Combined Use of Linaclotide and Polyethylene Glycol Electrolyte Powder in Colonoscopy Preparation for Patients With Chronic Constipation.

OBJECTIVE: The purpose of this study is to evaluate the safety and efficacy of linaclotide and polyethylene glycol (PEG) electrolyte powder in patients with chronic constipation undergoing colonoscopy preparation. PATIENTS AND METHODS: We included 260 patients with chronic constipation who were scheduled to undergo a colonoscopy. They were equally divided into 4 groups using a random number table: 4L PEG, 3L PEG, 3L PEG+L, and 2L PEG+L. The 4 groups were compared based on their scores on the Boston Bowel Preparation Scale (BBPS) and Ottawa Bowel Preparation Quality Scale (OBPQS), adverse reactions during the bowel preparation procedure, colonoscope insertion time, colonoscope withdrawal time, detection rate of adenomas, and their willingness to repeat bowel preparation. RESULTS: In terms of the score of the right half of the colon, the score of the transverse colon, the total score using BBPS, and the total score using OBPQS, the 3L PEG (polyethylene glycol)+L group was superior to groups 3L PEG and 2L PEG+L ( P <0.05), but comparable to the 4L PEG group ( P >0.05). The incidence rate of vomiting was higher in the 4L PEG group than in the 2L PEG+L group ( P <0.05). There was no statistically significant difference in the insertion time of the colonoscope between the 4 groups. The colonoscope withdrawal time in the 3L PEG+L group was shorter than in groups 4L PEG and 3L PEG ( P <0.05) and comparable to that in the 4L PEG group ( P >0.05). There was no statistically significant difference in the rate of adenoma detection among the 4 groups ( P >0.05). The 4L PEG group was the least willing of the 4 groups to undergo repeated bowel preparation ( P <0.05). CONCLUSION: The 3L PEG+L is optimal among the 4 procedures. It can facilitate high-quality bowel preparation, reduce the incidence of nausea during the bowel preparation procedure, and encourage patients to undertake repeated bowel preparation.

Electrochemical Doping Effect on the Conductivity of Melanin-Inspired Materials.

Eumelanin is a natural pigment that can be particularly valuable for sustainable bioelectronic devices due to its inherent biocompatibility and hydration-dependent conductivity. However, the low conductivity of eumelanin limits its technological development. In this research, electrochemical doping was proposed as an alternative route to increase the electronic conductivity of synthetic eumelanin derivatives. Thin films of sulfonated eumelanin were deposited on platinum interdigitated electrodes and electrochemically treated by using cyclic voltammetry and chronoamperometry treatments. X-ray photoelectron spectroscopy analysis confirmed ion doping in sulfonated melanin. Current-voltage, current-time, and electrochemical impedance measurements were used to investigate the effect of different aqueous electrolytes (including KCl and LiClO4) treatments on the charge transport of sulfonated eumelanin. We show that the conductivity depends on the type and size of the anion used and can reach 10-3 S·cm-1. Additionally, depending on the electrolyte, there is a change in charge transport from mixed ionic/electronic to a predominantly electronic-only conduction. Our results show that the chemical nature of the ion plays an important role in the electrochemical doping and, consequently, in the charge transport of eumelanin. These insights serve as inspiration to explore the use of alternative electrolytes with different compositions further and develop eumelanin-based devices with tunable conductivities.

Nitrogen-doped lignin-derived electrode materials for supercapacitors were prepared using the domain-limited effect.

Supercapacitors, pivotal in mitigating the energy crisis stemming from dwindling fossil fuel reservoirs, necessitate meticulous consideration of electrode material preparation. While lignin-derived carbon materials sourced sustainably exhibit commendable potential as electrode materials, their intrinsic low capacitance limits widespread utilization. Herein, nitrogen atom doping of lignin (CNL) was accomplished employing a chemical modification technique employing cyanuric chloride as a dopant. The resultant nitrogen content measured at 2.85 %. Subsequent to CNL carbonation, the generated C3N4 was selectively confined to the internal surface of the CNLMS-800 through a domain-limited activation method, thereby rendering it suitable for deployment as a supercapacitor electrode material. CNLMS-800 manifests a substantial specific surface area of 1778.0 m2 g-1 and a concomitantly diminutive pore size of 2.6 nm. Noteworthy, the specific capacitance of CNLMS-800 attains 473.0 F g-1 at a current density of 0.5 A g-1 in a 6 M KOH electrolyte. The resultant energy density reaches 39.0 Wh kg-1 at a power density of 338.0 W kg-1. Crucially, even after 20,000 charge/discharge cycles at a current density of 10 A g-1, the capacitance retention attains an impressive 87.5 % in the KOH electrolyte. This innovative utilization of sustainable resources for electrode fabrication epitomizes a seminal advancement in the field of energy technology.