An array of individually addressable micro-needles for mapping pH distributions

Zuliani, Claudio; Ng, Fu Siong; Alenda, Andrea; Eftekhar, Amir; Peters, Nicholas S.; Toumazou, C.

doi:10.1039/c6an00639f

Cited by 28 publications

(28 citation statements)

References 39 publications

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“…Scientific RepoRtS |(2020) 10:4110 | https://doi.org/10.1038/s41598-020-60713-z www.nature.com/scientificreports www.nature.com/scientificreports/ wearable devices47,48 , and low cost and high throughput44,49 . It is expected that the present results contribute to the development of such novel pH measurement techniques.…”

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confidence: 99%

Development of glass micro-electrodes for local electric field, electrical conductivity, and pH measurements

Doi

Asano

2020

Sci Rep

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In micro- and nanofluidic devices, liquid flows are often influenced by ionic currents generated by electric fields in narrow channels, which is an electrokinetic phenomenon. Various technologies have been developed that are analogous to semiconductor devices, such as diodes and field effect transistors. On the other hand, measurement techniques for local electric fields in such narrow channels have not yet been established. In the present study, electric fields in liquids are locally measured using glass micro-electrodes with 1-μm diameter tips, which are constructed by pulling a glass tube. By scanning a liquid poured into a channel by glass micro-electrodes, the potential difference in a liquid can be determined with a spatial resolution of the size of the glass tip. As a result, the electrical conductivity of sample solutions can be quantitatively evaluated. Furthermore, combining two glass capillaries filled with buffer solutions of different concentrations, an ionic diode that rectifies the proton conduction direction is constructed, and the possibility of pH measurement is also demonstrated. Under constant-current conditions, pH values ranging from 1.68 to 9.18 can be determined more quickly and stably than with conventional methods that depend on the proton selectivity of glass electrodes under equilibrium conditions.

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confidence: 99%

Development of glass micro-electrodes for local electric field, electrical conductivity, and pH measurements

Doi

Asano

2020

Sci Rep

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“…Initially we have targeted to measure the pH, and currently we are examining potassium electrodes as well [7]. For pH we decided to use IrOx wires [8]. The mechanism behind ability of the IrOx to sense pH changes lies in the existence of redox chemical reaction between two IrOx types, namely Ir(III)Ox and Ir(IV)Ox:…”

Section: A Sensors: Irox Electrodesmentioning

confidence: 99%

“…Details about the IrOx pH sensor calibrations are given in our previous publication [8]. For CAP recordings we first tested the validity of using an IrOx electrode.…”

Section: A Irox Sensor: Ph Calibration Cap Recordingmentioning

confidence: 99%

Platform for Closed Loop Neuromodulation Based on Dual Mode Biosignals

Mirza

Kulasekeram

Cork

et al. 2017

Preprint

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Abstract-Closed loop neuromodulation, where the stimulation is controlled autonomously based on physiological events, has been more effective than open loop techniques. In the few existing closed loop implementations which have a feedback, indirect non-neurophysiological biomarkers have been typically used (e.g. heart rate, stomach distension). Although these biomarkers enable automatic initiation of neural stimulation, they do not enable intelligent control of stimulation dosage. In this paper, we present a novel closed loop neuromodulation platform based on a dual signal mode that is detecting electrical and chemical signatures of neural activity. We demonstrated it on a case of vagus nerve stimulation (VNS). Vagal chemical (pH) signal is detected and used for initiating VNS and vagal compound action potential (CAP) signals are used to determine the stimulation dosage and pattern. Although we used the paradigm of appetite control and neurometabolic therapies, the platform developed here can be utilised for prototyping closed loop neuromodulation systems before adapting the final System-on-Chip (SoC) design.

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“…In this way, blood glucose levels are maintained and the risk of hypoglycemia, caused by the release of excess drug, is reduced [ 16 , 19 ]. Many pH [ 19 , 20 ] ultrasound [ 21 ] or light-responsive [ 22 ] polymer and hydrogel microcarriers [ 23 ] have been extensively explored for triggered drug release, but few of them can be easily prepared with simultaneous stimulus-sensitivity and biocompatibility [ 17 , 24 , 25 ]. Moreover, most smart drug delivery systems make use of several chemical and slow processes.…”

Section: Introductionmentioning

confidence: 99%

Smart Microneedles with Porous Polymer Layer for Glucose-Responsive Insulin Delivery

et al. 2020

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A closed-loop system imitating the function of pancreatic cells, connected to microneedles (MNs) that automatically “release” insulin in response to the blood glucose (BG) levels would be highly satisfactory for improving the quality of life and health for diabetes patients. This paper describes an easy, fast and simple technique of coating a porous polymer layer on stainless steel (SS) MNs that release insulin in a glucose-responsive fashion. It was fabricated by sealing insulin, sodium bicarbonate (a pH-sensitive element [NaHCO3]) and glucose oxidase (glucose-specific enzymes [GOx]) into the pores of a porous polymer coating. Glucose can passively diffuse into the pores and become oxidized to gluconic acid by GOx, thereby causing a decrease in local pH. The subsequent reaction of protons with NaHCO3 forms carbon dioxide (CO2) which creates pressure inside the pores, thereby rupturing the thin polymer film and releasing the encapsulated insulin. Field emission scanning electron microscopy (FE-SEM) images displayed that upon the exposure of MNs to glucose-free phosphate buffer saline (PBS) with pH 7.4, the pores of the porous MNs were closed, while in MNs exposed to a hyperglycemic glucose level, the pores were opened and the thin film burst. These MNs demonstrated both in vitro (in porcine skin and PBS) and in vivo (in diabetic rats) glucose-mediated insulin release under hyperglycemic conditions with rapid responsiveness. This study validated that the release of insulin from porous MNs was effectively correlated with glucose concentration.

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An array of individually addressable micro-needles for mapping pH distributions

Abstract: This work describes the preparation of an array of individually addressable pH sensitive microneedles which demonstrated suitable for measuring pH distribution during heart ischemia and reperfusion cycles.

Cited by 28 publications

References 39 publications

Development of glass micro-electrodes for local electric field, electrical conductivity, and pH measurements

Development of glass micro-electrodes for local electric field, electrical conductivity, and pH measurements

Platform for Closed Loop Neuromodulation Based on Dual Mode Biosignals

Smart Microneedles with Porous Polymer Layer for Glucose-Responsive Insulin Delivery

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