Observed Tissue Reactions Associated with Subacute Implantation of Cortical Intraparenchymal Microelectrode Arrays

Abstract Objective. Neural interfaces are an essential tool to enable the human body to directly communicate with machines such as computers or prosthetic robotic arms. Since invasive electrodes can be located closer to target neurons, they have advantages such as precision in stimulation and high signal-to-noise ratio (SNR) in recording, while they often exhibit unstable performance in long-term in-vivo implantation because of the tissue damage caused by the electrodes insertion. In the present study, we investigated the electrical functionality of flexible penetrating microelectrode arrays (FPMAs) up to 3 months in in-vivo conditions. Approach. The in-vivo experiment was performed by implanting FPMAs in five rats. The in-vivo impedance as well as the action potential (AP) amplitude and SNR were analyzed over weeks. Additionally, APs were tracked over time to investigate the possibility of single neuron recording. Main results. It was observed that the FPMAs exhibited dramatic increases in impedance for the first 4 weeks after implantation, accompanied by decreases in AP amplitude. However, the increase/decrease in AP amplitude was always accompanied by the increase/decrease in background noise, resulting in quite consistently maintained SNRs. After 4 weeks of implantation, we observed two distinctive issues regarding long-term implantation, each caused by chronic tissue responses or by the delamination of insulation layer. The results demonstrate that the FPMAs successfully recorded neuronal signals up to 12 weeks, with very stably maintained SNRs, reduced by only 16.1% on average compared to the first recordings, although biological tissue reactions or physical degradation of the FPMA were present. Significance. The fabricated FPMAs successfully recorded intracortical signals for 3 months. The SNR was maintained up to 3 months and the chronic function of FPMA was comparable with other silicon based implantable electrodes.

Download Full-text

641 What Is the Most Reliable Way to Secure A Surgical Drain?

British Journal of Surgery ◽

10.1093/bjs/znab134.157 ◽

2021 ◽

Vol 108 (Supplement_2) ◽

Author(s):

B Hughes ◽

J Stallard ◽

S Jivan

Keyword(s):

Suture Material ◽

Suture Techniques ◽

Robust Method ◽

Suturing Technique ◽

The Moment ◽

Tissue Reactions ◽

Surgical Drain

Abstract Introduction Surgical drains are used by many specialities, we aim to determine the most robust method of securing them by comparing suturing technique, material and fixation angle. Method A Blake’s drain was inserted into a piece of pork belly and secured using a standard ‘three half hitch’ technique with 3.0 Silk, EthilonTM and ProleneTM . For each suture type, drains were sutured in line, at 45 and 90 degrees to the course of the drain. The force needed for the suture to failure was measured and each repeated 3 times. Different suture techniques were then used to determine the strongest fixation. Results With the drain exiting inline the moment of failure was, on average, 1.25kg for silk, 3.5kg for EthilonTM and 4.0kg for ProleneTM. Increasing drain fixation angle required more force for the suture to fail. With EthilonTM and ProleneTM, the suture snapped before the drain slipped. Three half hitches was the strongest technique. Conclusions Suture material, technique and drain fixation angle had an impact on suture strength with ProleneTM outperforming Silk. We advocate using a ‘three half hitch’ technique with 3.0 ProleneTM to secure a surgical drain. It offers superior strength whilst reducing the risk of localised tissue reactions.

Download Full-text

Extracellular detection of neuronal coupling

Scientific Reports ◽

10.1038/s41598-021-94282-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Elmer Guzman ◽

Zhuowei Cheng ◽

Paul K. Hansma ◽

Kenneth R. Tovar ◽

Linda R. Petzold ◽

...

Keyword(s):

Action Potentials ◽

Microelectrode Arrays ◽

Short Latency ◽

Spike Sorting ◽

Neuronal Connectivity ◽

Direct Stimulation ◽

Multiple Electrodes

AbstractWe developed a method to non-invasively detect synaptic relationships among neurons from in vitro networks. Our method uses microelectrode arrays on which neurons are cultured and from which propagation of extracellular action potentials (eAPs) in single axons are recorded at multiple electrodes. Detecting eAP propagation bypasses ambiguity introduced by spike sorting. Our methods identify short latency spiking relationships between neurons with properties expected of synaptically coupled neurons, namely they were recapitulated by direct stimulation and were sensitive to changing the number of active synaptic sites. Our methods enabled us to assemble a functional subset of neuronal connectivity in our cultures.

Download Full-text

Fabrication and Characterization of 3D Microelectrode Arrays (3D MEAs) with "Edge-Wrapped" Metal Interconnects and 3D-Printed Assembly Rigs for Simultaneous Optical and Electrical Probing of Nerve-on-a-Chip® Constructs

2021 IEEE 34th International Conference on Micro Electro Mechanical Systems (MEMS) ◽

10.1109/mems51782.2021.9375313 ◽

2021 ◽

Author(s):

Charles M. Didier ◽

Corey Rountree ◽

Julia Freitas Orrico ◽

Avra Kundu ◽

Nilab Azim ◽

...

Keyword(s):

Microelectrode Arrays ◽

3D Printed ◽

Fabrication And Characterization ◽

Metal Interconnects

Download Full-text

Revealing Inflammatory Indications Induced by Titanium Alloy Wear Debris in Periprosthetic Tissue by Label-Free Correlative High-Resolution Ion, Electron and Optical Microspectroscopy

Materials ◽

10.3390/ma14113048 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3048

Author(s):

Rok Podlipec ◽

Esther Punzón-Quijorna ◽

Luka Pirker ◽

Mitja Kelemen ◽

Primož Vavpetič ◽

...

Keyword(s):

Titanium Alloy ◽

High Resolution ◽

Wear Debris ◽

Ion Beam ◽

Quantitative Measure ◽

Label Free ◽

Periprosthetic Tissue ◽

Correlative Microscopy ◽

X Ray ◽

Tissue Reactions

The metallic-associated adverse local tissue reactions (ALTR) and events accompanying worn-broken implant materials are still poorly understood on the subcellular and molecular level. Current immunohistochemical techniques lack spatial resolution and chemical sensitivity to investigate causal relations between material and biological response on submicron and even nanoscale. In our study, new insights of titanium alloy debris-tissue interaction were revealed by the implementation of label-free high-resolution correlative microscopy approaches. We have successfully characterized its chemical and biological impact on the periprosthetic tissue obtained at revision surgery of a fractured titanium-alloy modular neck of a patient with hip osteoarthritis. We applied a combination of photon, electron and ion beam micro-spectroscopy techniques, including hybrid optical fluorescence and reflectance micro-spectroscopy, scanning electron microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), helium ion microscopy (HIM) and micro-particle-induced X-ray emission (micro-PIXE). Micron-sized wear debris were found as the main cause of the tissue oxidative stress exhibited through lipopigments accumulation in the nearby lysosome. This may explain the indications of chronic inflammation from prior histologic examination. Furthermore, insights on extensive fretting and corrosion of the debris on nm scale and a quantitative measure of significant Al and V release into the tissue together with hydroxyapatite-like layer formation particularly bound to the regions with the highest Al content were revealed. The functional and structural information obtained at molecular and subcellular level contributes to a better understanding of the macroscopic inflammatory processes observed in the tissue level. The established label-free correlative microscopy approach can efficiently be adopted to study any other clinical cases related to ALTR.

Download Full-text

Wafer-Scale Fabrication and Assembly Method of Multichannel Microelectrode Arrays for ECoG Application

Electronics ◽

10.3390/electronics10030316 ◽

2021 ◽

Vol 10 (3) ◽

pp. 316

Author(s):

Cong Wang ◽

Yu-Chen Wei ◽

Ho-Kun Sung ◽

Alok Kumar ◽

Zhong-Liang Zhou ◽

...

Keyword(s):

Printed Circuit Boards ◽

Electrochemical Impedance ◽

Microelectrode Arrays ◽

Absence Seizure ◽

Curing Conditions ◽

Wafer Scale ◽

In Vivo Test ◽

Assembly Method ◽

Signal Recording

High density electrocorticography (ECoG)-based microelectrode arrays (MEAs) are fabricated to timely record the neural activities to provide the fundamental understanding in neuroscience and biomedical engineering. This paper aims to introduce a device-based concept and wafer-scale fabrication process for MEAs. Flexible and biocompatible polyimide is applied on MEAs to bear all possible stress and strain. Detailed fabrication key techniques, including surface treatment, polyimide stability measurement, evaporation process, and curing conditions, have been discussed thoroughly. Moreover, the fabricated polyimide-based MEAs are surface-mounted on well-packaged printed circuit boards (PCBs) via a slot-type connector without any additional wire bonding to make the signal recording process easier. An absence seizure was recorded during the in vivo test, which shows the availability of signal recording based on the presented MEAs. The proposed MEAs could be remained at the skull, while the connector and PCBs can be disassembled apart. Therefore, the testing sample will get less suffering. To verify the robustness of the fabricated MEAs, the impedance properties were characterized using electrochemical impedance spectroscopy. The measured results indicate an average impedance of 12.3 ± 0.675 kΩ at 1 kHz. In total, 10 groups of MEAs were sample tested, and over 90% of the total 60 channels per 1-MEAs operated efficiently.

Download Full-text