An open-source head-fixation and implant-protection system for mice.

Mice are widely used in neuroscience experiments, which often require head-fixation and attachment of skull-mounted hardware. For many experiments, these components must remain intact over weeks to months, ideally with animals group housed. Many labs have designed ad-hoc head-fixation systems, which is an inefficient process. For example, when reinventing these solutions in our lab, we faced challenges with group housing, wherein mice would chew and damage implanted cannulas and electrodes of their cage mates. We performed several non-trivial design iterations to solve this problem, and present the most successful designs as an open-source collection. The designs include a standard mounting headbar compatible with most skull-mounted hardware, a snap-on protective mouse hat (headhat) to prevent mice from chewing the hardware, and a head-fixation station to facilitate common experimental procedures. We provide 3D-printing files, detail vendors and software used to make the components of the system, and provide editable design files for maximum flexibility to individual lab requirements.

An open-source transparent microelectrode array.

Objective.The micro-electrode array (MEA) is a cell-culture surface with integrated electrodes used for assays of electrically excitable cells and tissues. MEAs have been a workhorse in the study of neurons and myocytes, owing to the scalability and millisecond temporal resolution of the technology. However, traditional MEAs are opaque, precluding inverted microscope access to modern genetically encoded optical sensors and effectors.Approach. To address this gap, transparent MEAs have been developed. However, for many labs, transparent MEAs remain out of reach due to the cost of commercially available products, and the complexity of custom fabrication. Here, we describe an open-source transparent MEA based on the OpenEphys platform (Siegleet al2017J. Neural Eng.14045003).Main results.We demonstrate the performance of this transparent MEA in a multiplexed electrical and optogenetic assay of primary rat hippocampal neurons.Significance.This open-source transparent MEA and recording platform is designed to be accessible, requiring minimal microelectrode fabrication or circuit design experience. We include low-noise connectors for seamless integration with the Intan Technologies headstage, and a mechanically stable adaptor conforming to the 24-well plate footprint for compatibility with most inverted microscopes.

Audit of the efficacy and complications of cyanoacrylate glue embolisation to treat varicose veins in primary care.

INTRODUCTION Cyanoacrylate glue embolization (CAGE) is a non-surgical procedure that uses a proprietary medical adhesive, delivered endovenously to close truncal, varicose veins. AIM To describe CAGE administered by a New Zealand general practitioner (GP) in primary care. METHODS The procedures were performed by a single GP with a special interest and 19 years' clinical experience in procedural phlebology. The clinical records of 107 consecutive patients who underwent CAGE over a 2-year period were retrospectively reviewed. Some patients had bilateral disease and some had more than one truncal vein per leg treated. Data on 173 truncal veins were included in the audit. Clinical data, procedural details and postprocedural course were recorded and analysed for 71 females and 36 males. RESULTS In total, 173 truncal veins were treated. They included the anterior accessory saphenous vein, the great saphenous vein, the small (lesser) saphenous vein and the thigh extension with a range of clinical severity. The most commonly treated truncal vein was the great saphenous vein with an average truncal diameter of 8.8mm (2.9s.d.). Of the 173 treated truncal veins, two failed to seal with CAGE, but were sealed after adjuvant ultrasound-guided foam sclerotherapy treatment. Post CAGE, 14.5% of treated truncal veins developed a phlebitis. DISCUSSION This audit shows that varicose veins can be treated in general practice with high levels of anatomic efficacy and few adverse effects.

Optical nondestructive dynamic measurements of wafer-scale encapsulated nanofluidic channels.

Nanofluidic channels are of great interest for DNA sequencing, chromatography, and drug delivery. However, metrology of embedded or sealed nanochannels and measurement of their fill-state have remained extremely challenging. Existing techniques have been restricted to optical microscopy, which suffers from insufficient resolution, or scanning electron microscopy, which cannot measure sealed or embedded channels without cleaving the sample. Here, we demonstrate a novel method for accurately extracting nanochannel cross-sectional dimensions and monitoring fluid filling, utilizing spectroscopic ellipsometric scatterometry, combined with rigorous electromagnetic simulations. Our technique is capable of measuring channel dimensions with better than 5-nm accuracy and assessing channel filling within seconds. The developed technique is, thus, well suited for both process monitoring of channel fabrication as well as for studying complex phenomena of fluid flow through nanochannel structures.

Bioelectronic measurement and feedback control of molecules in living cells.

We describe an electrochemical measurement technique that enables bioelectronic measurements of reporter proteins in living cells as an alternative to traditional optical fluorescence. Using electronically programmable microfluidics, the measurement is in turn used to control the concentration of an inducer input that regulates production of the protein from a genetic promoter. The resulting bioelectronic and microfluidic negative-feedback loop then serves to regulate the concentration of the protein in the cell. We show measurements wherein a user-programmable set-point precisely alters the protein concentration in the cell with feedback-loop parameters affecting the dynamics of the closed-loop response in a predictable fashion. Our work does not require expensive optical fluorescence measurement techniques that are prone to toxicity in chronic settings, sophisticated time-lapse microscopy, or bulky/expensive chemo-stat instrumentation for dynamic measurement and control of biomolecules in cells. Therefore, it may be useful in creating a: cheap, portable, chronic, dynamic, and precise all-electronic alternative for measurement and control of molecules in living cells.

Re-engineering artificial muscle with microhydraulics.

We introduce a new type of actuator, the microhydraulic stepping actuator (MSA), which borrows design and operational concepts from biological muscle and stepper motors. MSAs offer a unique combination of power, efficiency, and scalability not easily achievable on the microscale. The actuator works by integrating surface tension forces produced by electrowetting acting on scaled droplets along the length of a thin ribbon. Like muscle, MSAs have liquid and solid functional components and can displace a large fraction of their length. The 100 µm pitch MSA presented here already has an output power density of over 200 W kg-1, rivaling the most powerful biological muscles, due to the scaling of surface tension forces, MSA's power density grows quadratically as its dimensions are reduced.