Pinecone oil supplemented to multiparous sows from 107 days prenatal to 21 days postpartum improves reproductive performance and milk composition and affects serum parameters.

Pinecone oil (PO) of Pinus koraiensis mainly contains α-pinene, ß-pinene, and limonene that may ameliorate animal well-being and growth performance. This study evaluated its effects on feed intake, milk composition and yield, serum parameters, and litter growth of sows. Twenty-seven pregnant sows (parity 2-4) were distributed to three dietary treatments. The trial started on Day 107 of gestation and ended on Day 21 of lactation. Sows were given either a basal diet or the basal diet + 200 or 400 mg/kg PO. Each treatment contained nine sows and each sow was considered an experimental unit. Results showed that the average daily gain and weaned body weight of piglets from the sows fed 400 mg/kg PO supplements were higher (p < 0.05) than the piglets from the control sows. Lactose content in colostrum samples and fat content in milk samples were higher (p < 0.05) in 400 mg/kg PO-treated sows, respectively, than those from the sows fed basal diet. Additionally, cortisol concentration and aspartate aminotransferase concentration in sow serum was lowered (p < 0.05) by 400 mg/kg PO on Day 21 of lactation. In conclusion, supplementation of 400 mg/kg PO during late gestation and lactation contributed to greater offspring growth performance, possibly by enhanced milk quality and alleviated maternal stress.

Influences of flavonoid (quercetin) inclusion to corn-soybean-gluten meal-based diet on broiler performance.

Quercetin (a predominant flavonoid) is considered to have antimicrobial and antioxidant properties. This trial was conducted to evaluate the impact of graded doses of quercetin (QS) on growth efficiency, nutrient retention, faecal score, footpad lesion score, tibia ash and meat quality. In a 32-day feeding test, a total of 576 1-day-old Ross 308 broilers (male) were allocated arbitrarily with an average body weight of 41 ± 0.5 g. The trial had four dietary treatments with eight repetitions of 18 birds per pen and a basal diet incorporating 0%, 0.02%, 0.04% and 0.06% of QS. As the QS dosage increased, body weight gain tended to increase linearly on Days 9-21 (p = 0.069) and overall period (p = 0.079). Similarly, feed intake increased (p = 0.009) linearly with the increasing doses of QS on Days 9-21. Likewise, there was a linear improvement in dry matter (p = 0.002) and energy (p = 0.016) digestibility after QS administration. Moreover, the inclusion of QS supplement (0%-0.06%) linearly increased (p = 0.012) tibia ash in broilers. However, the faecal score and footpad lesion score showed no significant outcome (p > 0.05). By giving broilers a graded amount of QS, the relative organ weights of breast muscle (p = 0.009) and spleen (p = 0.006) improved linearly, meat colour lightness increased (p = 0.015), redness tended to improve (p = 0.065) linearly and drip loss decreased (p = 0.015) linearly. The inclusion of QS in the graded-level diet led to improvements in growth efficiency, nutrient absorption, meat quality and tibia ash, which recommended it as a beneficial feed additive for the broiler.

Synergism, Bifunctionality, and the Evolution of a Gradual Sensory Trade-off in Hummingbird Taste Receptors.

Sensory receptor evolution can imply trade-offs between ligands, but the extent to which such trade-offs occur and the underlying processes shaping their evolution is not well understood. For example, hummingbirds have repurposed their ancestral savory receptor (T1R1-T1R3) to detect sugars, but the impact of this sensory shift on amino acid perception is unclear. Here, we use functional and behavioral approaches to show that the hummingbird T1R1-T1R3 acts as a bifunctional receptor responsive to both sugars and amino acids. Our comparative analyses reveal substantial functional diversity across the hummingbird radiation and suggest an evolutionary timeline for T1R1-T1R3 retuning. Finally, we identify a novel form of synergism between sugars and amino acids in vertebrate taste receptors. This work uncovers an unexplored axis of sensory diversity, suggesting new ways in which nectar chemistry and pollinator preferences can coevolve.

Alanine-specific appetite in slow growing chickens is associated with impaired glucose transport and TCA cycle.

BACKGROUND: The rate of protein accretion and growth affect amino acid requirements in young animals. Differences in amino acid metabolism contribute to individual variations in growth rate. This study aimed at determining how amino acid needs may change with growth rates in broiler chickens. Experiment 1 consisted of testing amino acid choices in two chicken groups with extreme growth rates (the slowest -SG- or fastest -FG- growing birds in a flock). Essential (EAA) (methionine, lysine and threonine) or non-essential (NEAA) (alanine, aspartic acid and asparagine) amino acids were added to a standard control feed (13.2 MJ/kg; 21.6% crude protein). The chickens were offered simultaneous access to the control feed and a feed supplemented with one of the two amino acid mixes added at 73% above standard dietary levels. Experiment 2 consisted of the selection of the bottom 5 SG and top 5 FG chickens from a flock of 580 to study differences in amino acid metabolism using the proventriculus representing gut sensing mechanism. In this experiment, transcriptomic, proteomic, and genomic analyses were used to compare the two groups of chickens. RESULTS: SG preferred NEAA, while they rejected EAA supplemented feeds (P < 0.05). However, FG rejected NEAA (P < 0.05), and they were indifferent to EAA supplemented feed (P > 0.05). Transcriptomic and proteomic analyses identified 909 differentially expressed genes and 146 differentially abundant proteins associated with differences in growth rate (P < 0.05). The integration of gene expression and protein abundance patterns showed the downregulation of sensing and transport of alanine and glucose associated with increased alanine catabolism to pyruvate in SG chickens. CONCLUSION: Dietary preferences for NEAA in the SG group are associated with a potential cytosolic depletion of alanine following an upregulation of the catabolism into TCA cycle intermediates.

Sensitive Electrochemical Non-Enzymatic Detection of Glucose Based on Wireless Data Transmission.

Miniaturization and wireless continuous glucose monitoring are key factors for the successful management of diabetes. Electrochemical sensors are very versatile and can be easily miniaturized for wireless glucose monitoring. The authors report a microneedle-based enzyme-free electrochemical wireless sensor for painless and continuous glucose monitoring. The microneedles (MNs) fabricated consist of a 3 × 5 sharp and stainless-steel electrode array configuration. Each MN in the 3 × 5 array has 575 µm × 150 µm in height and width, respectively. A glucose-catalyzing layer, porous platinum black, was electrochemically deposited on the tips of the MNs by applying a fixed cathodic current of 2.5 mA cm-2 for a period of 200 s. For the non-interference glucose sensing, the platinum (Pt)-black-coated MN was carefully packaged into a biocompatible ionomer, nafion. The surface morphologies of the bare and modified MNs were studied using field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray analysis (EDX). The wireless glucose sensor displayed a broad linear range of glucose (1→30 mM), a good sensitivity and higher detection limit of 145.33 µA mM-1 cm-2 and 480 µM, respectively, with bare AuMN as a counter electrode. However, the wireless device showed an improved sensitivity and enhanced detection limit of 445.75, 165.83 µA mM-1 cm-2 and 268 µM, respectively, with the Pt-black-modified MN as a counter electrode. The sensor also exhibited a very good response time (2 s) and a limited interference effect on the detection of glucose in the presence of other electroactive oxidizing species, indicating a very fast and interference-free chronoamperometric response.

Hepatoprotective Effects of Ixeris chinensis on Nonalcoholic Fatty Liver Disease Induced by High-Fat Diet in Mice: An Integrated Gut Microbiota and Metabolomic Analysis.

Ixeris chinensis (Thunb.) Nakai (IC) is a folk medicinal herb used in Mongolian medical clinics for the treatment of hepatitis and fatty liver diseases even though its pharmacological mechanism has not been well characterized. This study investigated the hepatoprotective mechanism of IC on mice with nonalcoholic fatty liver disease (NAFLD) by integrating gut microbiota and metabolomic analysis. A high-fat diet (HFD) was used to develop nonalcoholic fatty liver disease, after which the mice were treated with oral IC (0.5, 1.5 and 3.0 g/kg) for 10 weeks. HFD induced NAFLD and the therapeutic effects were characterized by pathological and histological evaluations, and the serum indicators were analyzed by ELISA. The gut microbial and metabolite profiles were studied by 16S rRNA sequencing and untargeted metabolomic analysis, respectively. The results showed that the administration of IC resulted in significant decreases in body weight; liver index; serum biomarkers such as ALT, TG, and LDL-C; and the liver inflammatory factors IL-1ß, IL-6, and TNF-α. The 16S rRNA sequencing results showed that administration of IC extract altered both the composition and abundance of the gut microbiota. Untargeted metabolomic analysis of liver samples detected a total of 212 metabolites, of which 128 were differentially expressed between the HFD and IC group. IC was found to significantly alter the levels of metabolites such as L-glutamic acid, pyridoxal, ornithine, L-aspartic acid, D-proline, and N4-acetylaminobutanal, which are involved in the regulation of glutamine and glutamate, Vitamin B6 metabolism, and arginine and proline metabolic pathways. Correlation analysis indicated that the effects of the IC extract on metabolites were associated with alterations in the abundance of Akkermansiaceae, Lachnospiraceae, and Muribaculaceae. Our study revealed that IC has a potential hepatoprotective effect in NAFLD and that its function might be linked to improvements in the composition of gut microbiota and their metabolites.

Deciphering the Disaggregation Mechanism of Amyloid Beta Aggregate by 4-(2-Hydroxyethyl)-1-Piperazinepropanesulfonic Acid Using Electrochemical Impedance Spectroscopy.

Aggregation of amyloid-ß (aß) peptides into toxic oligomers, fibrils, and plaques is central in the molecular pathogenesis of Alzheimer's disease (AD) and is the primary focus of AD diagnostics. Disaggregation or elimination of toxic aß aggregates in patients is important for delaying the progression of neurodegenerative disorders in AD. Recently, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS) was introduced as a chemical agent that binds with toxic aß aggregates and transforms them into monomers to reduce the negative effects of aß aggregates in the brain. However, the mechanism of aß disaggregation by EPPS has not yet been completely clarified. In this study, an electrochemical impedimetric immunosensor for aß diagnostics was developed by immobilizing a specific anti-amyloid-ß (aß) antibody onto a self-assembled monolayer functionalized with a new interdigitated chain-shaped electrode (anti-aß/SAM/ICE). To investigate the ability of EPPS in recognizing AD by extricating aß aggregation, commercially available aß aggregates (aßagg) were used. Electrochemical impedance spectroscopy was used to probe the changes in charge transfer resistance (Rct) of the immunosensor after the specific binding of biosensor with aßagg. The subsequent incubation of the aßagg complex with a specific concentration of EPPS at different time intervals divulged AD progression. The decline in the Rct of the immunosensor started at 10 min of EPPS incubation and continued to decrease gradually from 20 min, indicating that the accumulation of aßagg on the surface of the anti-aß/SAM/ICE sensor has been extricated. Here, the kinetic disaggregation rate k value of aßagg was found to be 0.038. This innovative study using electrochemical measurement to investigate the mechanism of aßagg disaggregation by EPPS could provide a new perspective in monitoring the disaggregation periods of aßagg from oligomeric to monomeric form, and then support for the prediction and handling AD symptoms at different stages after treatment by a drug, EPPS.

Microneedle Array Electrode-Based Wearable EMG System for Detection of Driver Drowsiness through Steering Wheel Grip.

Driver drowsiness is a major cause of fatal accidents throughout the world. Recently, some studies have investigated steering wheel grip force-based alternative methods for detecting driver drowsiness. In this study, a driver drowsiness detection system was developed by investigating the electromyography (EMG) signal of the muscles involved in steering wheel grip during driving. The EMG signal was measured from the forearm position of the driver during a one-hour interactive driving task. Additionally, the participant's drowsiness level was also measured to investigate the relationship between muscle activity and driver's drowsiness level. Frequency domain analysis was performed using the short-time Fourier transform (STFT) and spectrogram to assess the frequency response of the resultant signal. An EMG signal magnitude-based driver drowsiness detection and alertness algorithm is also proposed. The algorithm detects weak muscle activity by detecting the fall in EMG signal magnitude due to an increase in driver drowsiness. The previously presented microneedle electrode (MNE) was used to acquire the EMG signal and compared with the signal obtained using silver-silver chloride (Ag/AgCl) wet electrodes. The results indicated that during the driving task, participants' drowsiness level increased while the activity of the muscles involved in steering wheel grip decreased concurrently over time. Frequency domain analysis showed that the frequency components shifted from the high to low-frequency spectrum during the one-hour driving task. The proposed algorithm showed good performance for the detection of low muscle activity in real time. MNE showed highly comparable results with dry Ag/AgCl electrodes, which confirm its use for EMG signal monitoring. The overall results indicate that the presented method has good potential to be used as a driver's drowsiness detection and alertness system.

Electrochemical Immunosensor for the Early Detection of Rheumatoid Arthritis Biomarker: Anti-Cyclic Citrullinated Peptide Antibody in Human Serum Based on Avidin-Biotin System.

Rheumatoid arthritis (RA) is a chronic autoimmune disease that produces a progressive inflammatory response that leads to severe pain, swelling, and stiffness in the joints of hands and feet, followed by irreversible damage of the joints. The authors developed a miniaturized, label-free electrochemical impedimetric immunosensor for the sensitive and direct detection of arthritis Anti-CCP-ab biomarker. An interdigitated-chain-shaped microelectrode array (ICE) was fabricated by taking the advantage of microelectromechanical systems. The fabricated ICE was modified with a self-assembled monolayer (SAM) of Mercaptohexanoic acid (MHA) for immobilization of the synthetic peptide bio-receptor (B-CCP). The B-CCP was attached onto the surface of SAM modified ICE through a strong avidin-biotin bio-recognition system. The modified ICE surface with the SAM and bio-molecules (Avidin, B-CCP, Anti-CCP-ab and BSA) was morphologically and electrochemically characterized. The change in the sensor signal upon analyte binding on the electrode surface was probed through the electrochemical impedance spectroscopy (EIS) property of charge-transfer resistance (Rct) of the modified electrodes. EIS measurements were target specific and the sensor response was linearly increased with step wise increase in target analyte (Anti-CCP-ab) concentrations. The developed sensor showed a linear range for the addition of Anti-CCP-ab between 1 IU mL-1 → 800 IU mL-1 in phosphate buffered saline (PBS) and Human serum (HS), respectively. The sensor showed a limit of detection of 0.60 IU mL-1 and 0.82 IU mL-1 in the PBS and HS, respectively. The develop bio-electrode showed a good reproducibility (relative standard deviation (RSD), 1.52%), selectivity and stability (1.5% lost at the end of 20th day) with an acceptable recovery rate (98.0% → 101.18%) and % RSD's for the detection of Anti-CCP-ab in spiked HS samples.

Fabrication of Parylene-Coated Microneedle Array Electrode for Wearable ECG Device.

Microneedle array electrodes (MNE) showed immense potential for the sensitive monitoring of the bioelectric signals by penetrating the stratum corneum with high electrical impedance. In this paper, we introduce a rigid parylene coated microneedle electrode array and portable electrocardiography (ECG) circuit for monitoring of ECG reducing the motion artifacts. The developed MNE showed stability and durability for dynamic and long-term ECG monitoring in comparison to the typical silver-silver chloride (Ag/AgCl) wet electrodes. The microneedles showed no mechanical failure under the compression force up-to 16 N, but successful penetration of skin tissue with a low insertion force of 5 N. The electrical characteristics of the fabricated MNE were characterized by impedance spectroscopy with equivalent circuit model. The designed wearable wireless ECG monitoring device with MNE proved feasibility of the ECG recording which reduces the noise of movement artifacts during dynamic behaviors.

Interdigitated and Wave-Shaped Electrode-Based Capacitance Sensor for Monitoring Antibiotic Effects.

Label-free and real-time monitoring of the bacterial viability is essential for the accurate and sensitive characterization of the antibiotic effects. In the present study, we investigated the feasibility of the interdigitated and wave-shaped electrode (IWE) for monitoring the effect of tetracycline or kanamycin on Staphylococcus aureus (S. aureus) and methicillin-resistant S.aureus (MRSA). The electrical impedance spectra of the IWE immersed in the culture media for bacterial growth were characterized in a frequency range of 10 Hz to 1 kHz. The capacitance index (CI) (capacitance change relevant with the bacterial viability) was used to monitor the antibiotic effects on the S. aureus and MRSA in comparison to the traditional methods (disk diffusion test and optical density (OD) measurement). The experimental results showed that the percentage of change in CI (PCI) for the antibiotic effect on MRSA was increased by 51.58% and 57.83% in kanamycin and control, respectively. In contrast, the PCI value decreased by 0.25% for tetracycline, decreased by 52.63% and 37.66% in the cases of tetracycline and kanamycin-treated S. aureus, and increased 2.79% in the control, respectively. This study demonstrated the feasibility of the IWE-based capacitance sensor for the label-free and real-time monitoring of the antibiotic effects on S.aureus and MRSA.

Real-Time Impedance Detection of Intra-Articular Space in a Porcine Model Using a Monopolar Injection Needle.

Rheumatoid arthritis and osteoarthritis can be treated through specific drug injection into the intra-articular space. Several failures during drug injection attempts with conventional fluoroscopy and ultrasonography in a small area of the intra-articular space have been reported. In this work we present an innovative impedance measurement-based method/algorithm for needle tip positioning to enhance image-guided intra-articular vaccination treatment. A novel algorithm for detecting the intra-articular space in the elbow and knee joints of a live porcine model is reported. An impedance measurement system was developed for biological tissue measurement. The electrical impedance in the intra-articular space was monitored and the needle tip was examined by ultrasonography. The contrast dye was vaccinated and checked using fluoroscopy to confirm that the dye was properly inoculated in the cavity. The electrical impedance was estimated for various needle inclusion profundity levels in saline solution, which were broadly used to evaluate the proposed device for in vivo examinations. Good efficiency was observed in the impedance-based measurements using a monopolar injection needle for intra-articular therapy. To enhance the needle tip positioning for intra-articular therapy, the intended impedance measurement device with a monopolar injection needle can be used as a complement to existing modalities.

New Parylene Coating System with Real-Time and Non-Destructive Electrical Impedance Monitoring of Parylene Layer.

Parylene is one of the polymers widely used as an electrical insulating or waterproof layer in the fields of semiconductor, electronics, and biomedical engineering owing to its outstanding properties of chemically inertness, biocompatibility, water resistance, low conductivity, and flexibility. It is increasingly required for real-time and non-destructive characterization of the deposition of parylene layer for the quality control and assurance. In the present work, we suggested an impedance measurement based parylene coating system which can provide the electrical properties of the deposited parylene in real-time and non-destructively. For this, the impedance spectra of parylene C, N, or D were measured using the fabricated interdigitated and wave-shaped electrode (IWE) during the chemical vapor deposition (CVD) process. The results showed a feasibility to monitor the impedance change according to the parylene deposition, and that the resistance at the frequency of 2.15 kHz was decreased in dependency on the type of the deposited parylene.

Lock-in Amplifier-Based Impedance Detection of Tissue Type Using a Monopolar Injection Needle.

For successful intra-articular injection therapy, it is essential to accurately position the tip of the injection needle into the target joint area while administering the drug into the affected tissue. In this study, we investigated the feasibility of a monopolar injection needle and lock-in amplifier (LIA)-based impedance measurement system for detecting the tissue type where the needle tip is located. After positioning the monopolar injection needle tip into the dermis, hypodermis, or muscle layer of pork tissue, the electrical impedance was measured in the frequency range of 10 Hz to 10 kHz. We observed a difference in the results based on the tissue type where the needle was positioned (p-value < 0.01). Therefore, the monopolar injection needle with electrical impedance measurement can be used to improve intra-articular injection therapy through non-destructive and real-time monitoring of the needle position in the tissues.

Electrochemical Detection of C-Reactive Protein in Human Serum Based on Self-Assembled Monolayer-Modified Interdigitated Wave-Shaped Electrode.

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01-10,000 ng mL-1. The electrode showed detection limits of 0.025 ng mL-1 and 0.23 ng mL-1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.

Nonenzymatic determination of glucose at near neutral pH values based on the use of nafion and platinum black coated microneedle electrode array.

The authors report on a microneedle-based amperometric nonenzymatic glucose sensor for painless and continuous monitoring of glucose. It consists of 3 × 5 sharp stainless steel microneedles micromachined from a stainless steel substrate. The microneedles are 600 and 100 µm in height and width, respectively. Nafion and platinum black were sequentially coated onto the tip of gold-coated microneedles and used for nonenzymatic (direct) sensing of glucose. Attractive features of the modified microneedle electrode include (a) a low working potential (+0.12 V vs. Ag/AgCl), (b) a linear response in the physiologically relevant range (1-40 mM), (c) a sensitivity as high as 175 µA mM-1 cm-2, (d) a 23 µM detection limit, and (e) a response time of 2 s. The sensor also exhibits good reproducibility and stability. The sensor is selective for glucose even in the presence of 10-fold higher concentrations of ascorbic acid, lactic acid, dopamine, uric acid, and acetaminophen. Graphical abstract Schematic representation of the fabrication sequence for a nonenzymatic electrochemical glucose sensor using Nafion and platinum black coated microneedle electrode array. The sensor is based on measuring the faradaic current at +0.12 V vs. Ag/AgCl by the direct electrochemical oxidation of glucose to gluconic acid on the surface of a Pt black sensing layer.

Reduced Graphene Oxide Modified the Interdigitated Chain Electrode for an Insulin Sensor.

Insulin is a key regulator in glucose homeostasis and its deficiency or alternations in the human body causes various types of diabetic disorders. In this paper, we present the development of a reduced graphene oxide (rGO) modified interdigitated chain electrode (ICE) for direct capacitive detection of insulin. The impedance properties of rGO-ICE were characterized by equivalent circuit modeling. After an electrochemical deposition of rGO on ICE, the electrode was modified with self-assembled monolayers and insulin antibodies in order to achieve insulin binding reactions. The impedance spectra and capacitances were measured with respect to the concentrations of insulin and the capacitance change (ΔC) was analyzed to quantify insulin concentration. The antibody immobilized electrode showed an increment of ΔC according to the insulin concentration in human serum ranging from 1 ng/mL to 10 µg/mL. The proposed sensor is feasible for label-free and real-time measuring of the biomarker and for point-of-care diagnosis.

Electrical Impedance Monitoring of C2C12 Myoblast Differentiation on an Indium Tin Oxide Electrode.

Electrical cell-substrate impedance sensing is increasingly being used for label-free and real-time monitoring of changes in cell morphology and number during cell growth, drug screening, and differentiation. In this study, we evaluated the feasibility of using ECIS to monitor C2C12 myoblast differentiation using a fabricated indium tin oxide (ITO) electrode-based chip. C2C12 myoblast differentiation on the ITO electrode was validated based on decreases in the mRNA level of MyoD and increases in the mRNA levels of myogenin and myosin heavy chain (MHC). Additionally, MHC expression and morphological changes in myoblasts differentiated on the ITO electrode were comparable to those in cells in the control culture dish. From the monitoring the integration of the resistance change at 21.5 kHz, the cell differentiation was label-free and real-time detectable in 30 h of differentiation (p < 0.05).

Electrochemical Characterization of Poly-L-Lysine Coating on Indium Tin Oxide Electrode for Enhancing Cell Adhesion.

Nano or microelectrode-based cell chip for stimulating or recording neuronal signals requires better cell adhesion procedures in order to achieve efficient cell based assays for effective cellular diagnosis and for high throughput screening of drug candidates. The cells can be adhered on protein pre-coated sensing electrodes, but the electrochemical characteristics of cells are highly influenced by the electrical charge of the underlying protein interface. Thus, in this study, we report on experimental and theoretical aspects of poly-L-lysine (PLL) adsorption on transparent indium tin oxide (ITO) electrodes and the interaction between PLL and human embryonic kidney 293/GFP cells. PLL coated ITO electrodes showed a lower transfer resistance compared to bare or bovine serum albumin coated ITO electrodes. In addition, they exhibited more positive potential and higher magnitude of redox peak currents with increased immersion time of PLL solution. Finally, results of the impedance analysis showed that adhesion of cells was enhanced by PLL coating on ITO electrodes compared to bare ITO electrodes.

Dependence of Impedance Measurement Sensitivity of Cell Growth on Sensing Area of Circular Interdigitated Electrode.

A circular interdigitated electrode (IDE) array for label-free and real-time impedance monitoring of cell growth was fabricated and evaluated. Both the width and spacing of fingers were 50 µm, and the exposed sensing area of the circular IDE was 1.3~3.4 mm. The electrical characteristics of the fabricated circular IDE were modeled as an equivalent circuit, and the values of the circuit parameters extrapolated from the fitting to the measured spectra in different concentrations of NaCl or sensing areas of the circular IDE were analyzed. During cell growth, the resistance of cells extrapolated from the fitting was increased and the maximum rate of change in the real part of the impedance was observed at frequencies of 10 to 22 kHz. The normalized real part of the impedance measured at 10 kHz during cell growth was increased more with decreasing the electrode sensing area, albeit the number of cells to be investigated showed a corresponding increase.