A Nanopipette Platform for Delivering Nanoliter Volumes of Acetylcholine

Abstract

Delivery of nano-liter volumes of neurotransmitter is important in fundamental studies to understand the brain function, as well as in pharmacological intervention for the treatment of neurological disorders. We present here a nanopipette based electrochemical delivery platform for the delivery of acetylcholine, and the measurement of the delivered acetylcholine concentration profile following its delivery. The delivery was enabled by the applied voltage and nano-liter volumes (1.342 ± 0.417 nL) of acetylcholine was successfully delivered. An acetylcholine sensing electrode was used to monitor the acetylcholine concentration in the cellular environment immediately following its delivery, based on the ion transfer across the interface between two immiscible electrolyte solutions (ITIES). Parameters that affect the delivery process were investigated and it was unveiled that both the applied voltage duration and voltage magnitude affect the acetylcholine delivery into the cellular medium. The presented nanoliter delivery platform has advantages of easiness to fabricate, low cost, and flexibility to be positioned over different types of cellular structure. The accurate application of a drug and its subsequent detection after delivery in a localized region has important implications in medicine and pharmacology. [9][10][11][12] Studies show that the application of receptor agonists/antagonists to different regions of the brain invoked different responses.13,14 Synaptic and extrasynaptic receptors have different roles and functionalities, so targeting the entire neuron may have unintended consequences. For example, extrasynaptic NMDA receptor stimulation by neurotransmitters may result in excitotoxicity, while synaptic NMDA receptor stimulation is more neuroprotective. 15,16 These drastic differences in the receptor responses indicate a need for the precise application of the agonists/antagonists. Synapses are on the nanometer scale, 17 so targeting the synapse for localized drug therapy requires a delivery probe that is nm in scale to facilitate localized delivery, and can deliver drugs in a noninvasive manner.Accurately determining the delivery volume is important for the development of the quantitative delivery probe. Besides monitoring the delivery volume and location, it is also crucial to understand the concentration profile over time following the delivery. 18 The concentration of a drug or neurotransmitter at the site of its application can alter its effectiveness and toxicity.19 By monitoring the concentration profile, we can gain a deeper understanding on the amount of stimulation it takes to elicit a response, how long the stimulus remains in the environment, and the nature of diffusion in the environment. By creating an application system where one can have precise manipulations of both the volume and the location, along with an understanding of the change in concentration profile, there will be more control over delivery and better understanding of its effects. We developed the nanopipette delivery platfo...

Review—Nanopipette Applications as Sensors, Electrodes, and Probes: A Study on Recent Developments

“…88,89 One of these recent studies was carried out by McAllister and co-workers to not only deliver acetylcholine (ACh) but also measure its amount. 90 The fluorescence measurement of the ejected solution consisting of ACh and [Ru(bpy) 3 ] 2+ dye demonstrated that the average delivery volume was 1.342 ± 0.417 nl at 9 V applied potential. Relationship with applied voltage duration with increased Ach delivery was established which could be used for a more precise delivery response.…”

Enhancement of heavy ion track-etching in polyimide membranes with organic solvents

“…Recently, synthetic nanopores are gaining much attention because of their implementation for the miniaturization of biosensing devices in the field of bio/nanotechnology [1][2][3]. Moreover, the nanoporous membranes are frequently employed for molecular separation and purification processes as well as energy conversion systems [4][5][6][7][8][9][10]. Depending on the desired application, the nanopore dimensions such as size, shape, surface properties as well as the utilized membrane materials can be tuned to fulfill specific requirements.…”

“…The pore diameter can be tuned by varying the etchant concentration, temperature and the duration of the etching process. Moreover, several parameters have been adjusted such as exposure to UV light, variation of potential across the membrane and also addition of surfactants and different solvents in the etching solution to enhance the homogeneity and etching rate [7,[32][33][34][35][36].…”

Review—Track-Etched Nanoporous Polymer Membranes as Sensors: A Review

“…Various routes and methods have been explored so far for the fabrication of synthetic nanopores including ion beam sculpting, 27,28 electron beam sculpting, 29 thermal annealing, 30 micromolding, 31 dielectric breakdown, 32 laser assisted pulling of capillaries 33 and track-etching 34 in versatile materials like silicon nitride, 35 aluminium oxide, 36 boron nitride, 37 graphene, 38 polymers, [39][40][41] quartz 42 and silicon oxide. 43 Track-etching process is especially of interest for us since it allows the fabrication of different nanopore geometries by simply adjusting experimental conditions.…”