Microneedle patches: usability and acceptability for self-vaccination against influenza.

While therapeutic drugs are routinely self-administered by patients, there is little precedent for self-vaccination. Convenient self-vaccination may expand vaccination coverage and reduce administration costs. Microneedle patches are in development for many vaccines, but no reports exist on usability or acceptability. We hypothesized that naïve patients could apply patches and that self-administered patches would improve stated intent to receive an influenza vaccine. We conducted a randomized, repeated measures study with 91 venue-recruited adults. To simulate vaccination, subjects received placebo microneedle patches given three times by self-administration and once by the investigator, as well as an intramuscular injection of saline. Seventy participants inserted patches with thumb pressure alone and the remainder used snap-based devices that closed shut at a certain force. Usability was assessed by skin staining and acceptability was measured with an adaptive-choice analysis. The best usability was seen with the snap device, with users inserting a median value of 93-96% of microneedles over three repetitions. When a self-administered microneedle patch was offered, intent to vaccinate increased from 44% to 65% (CI: 55-74%). The majority of those intending vaccination would prefer to self-vaccinate: 64% (CI: 51-75%). There were no serious adverse events associated with use of microneedle patches. The findings from this initial study indicate that microneedle patches for self-vaccination against influenza are usable and may lead to improved vaccination coverage.

Evaluation of multi-well microelectrode arrays for neurotoxicity screening using a chemical training set.

Microelectrode array (MEA) approaches have been proposed as a tool for detecting functional changes in electrically excitable cells, including neurons, exposed to drugs, chemicals or particles. However, conventional single well-MEA systems lack the throughput necessary for screening large numbers of uncharacterized compounds. Recently, multi-well MEA (mwMEA) formats have become available to address the need for increased throughput. The current experiments examined the effects of a training set of 30 chemicals on spontaneous activity in networks of cortical neurons grown on mwMEA plates. Each plate contained 12 wells with 64 microelectrodes/well, for a total of 768 channels. Of the 30 chemicals evaluated, 23 were known to alter neuronal function in vivo ("positives"), including 6 GABAergic and 3 glutamatergic antagonists/agonists, 4 pyrethroids, 3 metals, 2 cholinesterase inhibitors, 2 nicotinic acetylcholine receptor agonists, valproic acid, verapamil, and fluoxetine. Seven compounds expected to have no effect on neuronal function were tested as "negatives" (glyphosate, acetaminophen, salicylic acid, paraquat, saccharin, d-sorbitol and amoxicillin). Following collection of 33 min of baseline activity, chemical effects (50 µM or highest soluble concentration) were recorded for 33 min. Twenty of the positives altered the mean network spike rate by more than the 14% threshold (two standard deviations from the mean for DMSO control). The three positives without effect were bifenthrin, nicotine and imidacloprid. None of the negative compounds caused a change in activity beyond the threshold. Based on these results, the mwMEA assay has both high sensitivity (87% identification of positive compounds) and specificity (100% identification of negative compounds). These experiments demonstrate the capacity of mwMEAs to screen compounds for neurotoxic effects mediated by a broad variety of mechanisms.

Highly-compliant, microcable neuroelectrodes fabricated from thin-film gold and PDMS.

Bio-electrodes have traditionally been made of materials such as metal and silicon that are much stiffer than the tissue from which they record or stimulate. This difference in mechanical compliance can cause incomplete or ineffective contact with the tissue. The electrode stiffness has also been hypothesized to cause chronic low-grade injury and scar-tissue encapsulation, reducing stimulation and recording efficiency. As an initial step to resolve these issues with electrode performance, we have developed and characterized electrically-functional, low-Young's modulus, microcable-shaped neuroelectrodes and demonstrated electrophysiological recording functionality. The microcable geometry gives the electrodes a similar footprint to traditional wire and microwire neuroelectrodes, while reducing the difference in Young's modulus from nervous tissue by orders of magnitude. The electrodes are composed of PDMS and thin-film gold, affording them a high-level of compliance that is well suited for in vivo applications. The composite Young's modulus of the electrode was experimentally determined to be 1.81 ± 0.01 MPa. By incorporating a high-tear-strength silicone, Sylgard 186, the load at failure was increased by 92%, relative to that of the commonly used Sylgard 184. The microcable electrodes were also electromechanically tested, with measurable conductivity (220 kΩ) at an average 8% strain (n = 2) after the application of 200% strain. Electrophysiological recording is demonstrated by wrapping the electrode around a peripheral nerve, utilizing the compliance and string-like profile of the electrode for effective recording in nerve tissue.

Low-power sensing for vestibular prostheses.

This paper describes a novel sensing approach for reducing power requirements of implantable vestibular prostheses. A passive, microfabricated polymeric inertial sensor for detecting angular head rotations based on the biomechanics of the human semicircular canal is described. Angular head motion is coded by deflection of a highly compliant capacitor plate placed in parallel with a rigid reference electrode. This capacitance change serves to detect instantaneous angular velocity along a given axis of rotation. Designed for integration with a microelectromechanical systems-based fully implantable vestibular prosthesis, this sensing method can provide substantial power savings when compared with contemporary gyroscopes.

Spatiotemporal localization of injury potentials in DRG neurons during vincristine-induced axonal degeneration.

The distal to proximal degeneration of axons, or "dying back" is a common pattern of neuropathology in many diseases of the PNS and CNS. A long-standing debate has centered on whether this pattern of neurodegeneration is due to an insult to the cell body or to the axon itself, although it is likely that mechanisms are different for specific disease entities. We have addressed this question in a model system of vincristine-induced axonal degeneration. Here, we created a novel experimental apparatus combining a microfluidic divider with a multielectrode array substrate to allow for independent monitoring of injury-induced electrical activity from dorsal root ganglion (DRG) cell bodies and axons while isolating them into their own culture microenvironments. At specified doses, exposure of the cell body to vincristine caused neither morphological neurodegeneration nor persistent hyperexcitability. In comparison, exposure of the distal axon to the same dose of vincristine first caused a decrease in the excitability of the axon and then axonal degeneration in a dying back pattern. Additionally, exposure of axons to vincristine caused an initial period of hyperexcitability in the cell bodies, suggesting that a signal is transmitted from the distal axon to the soma during the progression of vincristine-induced axonal degeneration. These data support the proposition that vincristine has a direct neurotoxic effect on the axon.

Three dimensional MEMS microfluidic perfusion system for thick brain slice cultures.

In vitro tissue culture models are often benchmarked by their ability to replicate in vivo function. One of the limitations of in vitro systems is the difficulty in preserving an orchestrated cell population, especially for generating three-dimensional tissue equivalents. For example, tissue-engineering applications involve large high-density constructs, requiring a perfusing system that is able to apply adequate oxygen and nutrients to the interior region of the tissue. This is particularly true with respect to thick tissue sections harvested for in vitro culture. We have fabricated a microneedle-based perfusion device for high-cell-density in vitro tissue culture from SU-8 photosensitive epoxy and suitable post-processing. The device was tested for its ability to improve viability in slices of harvested brain tissue. This model was chosen due to its acute sensitivity to disruptions in its nutrient supply. Improved viability was visible in the short term as assessed via live-dead discriminating fluorescent staining and confocal microscopy. This perfusion system opens up many possibilities for both neurobiological as well as other culture systems.

A multielectrode microcompartment culture platform for studying signal transduction in the nervous system.

This paper describes the design, fabrication, and characterization of a microfabricated compartmented culture system (micro-CCS) useful for electrophysiological signaling studies in cultured neurons. The focus of the paper is the process of interfacing the micro-CCS with cultured neurons and to demonstrate the applicability of the system for biochemical-mediated electrophysiological studies. Moreover, we show that we can record action potentials from cultured neurons through the extracellular compartmented application of elevated levels of K(+) ions. Finally, we show that we can isolate the electrophysiological effects of the sodium channel blocker tetrodotoxin in one of the compartments of a two compartment culture while recording electrophysiological data from both compartments.

Microfluidic devices for the high-throughput chemical analysis of cells.

A microfluidic device is reported that integrated cell handling, rapid cell lysis, and electrophoretic separation and detection of fluorescent cytosolic dyes. The device function was demonstrated using Jurkat cells that were loaded with the fluorogenic dyes - carboxyfluorescein diacetate, Oregon green carboxylic acid diacetate, or Calcein AM. The loaded cells were hydrodynamically transported from the cell-containing reservoir to a region on the microfluidic device where they were focused and then rapidly lysed using an electric field. Complete lysis was accomplished in <33 ms. The hydrolyzed, fluorescent dyes in the cell lysate were automatically injected into a separation channel on the device and detected 3 mm downstream of the injection point. The total separation time was approximately 2.2 s with absolute migration time reproducibilities of <1% and efficiencies ranging from 2300 to 4000 theoretical plates. Results from 139 cells are reported. A small fraction of these cells, approximately 9%, were found to enzymatically hydrolyze the loaded dyes in a manner significantly different from the majority of the cells. Cell analysis rates of 7-12 cells/min were demonstrated and are >100 times faster than those reported using standard bench-scale capillary electrophoresis.