DSpace Angular :: Browsing by Author "Burns, Owen"

Browsing by Author "Burns, Owen"

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Anti-inflammatory Effects of Abdominal Vagus Nerve Stimulation on Experimental Intestinal Inflammation
(Frontiers, 2019-05) Payne, Sophie; Furness, John; Burns, Owen; Sedo, Alicia; Hyakumura, Tomoko; Shepherd, Robert; Fallon, James
Electrical stimulation of the cervical vagus nerve is an emerging treatment for inflammatory bowel disease (IBD). However, cervical vagal nerve stimulation (VNS) can produce unwanted side effects. Here, we investigated whether stimulating the vagus nerve closer to the end organ has fewer off-target effects, while reducing intestinal inflammation. An electrode array was developed to stimulate and record vagal neural responses in rats. Acute VNS off-target experiment: The cervical and abdominal vagus nerves of anaesthetised rats (n=5) were acutely implanted with an electrode array, stimulation delivered (10 Hz; symmetric biphasic current pulse; 320 nC per phase) and changes to heart rate, respiration and blood pressure assessed. Chronic VNS efficacy experiment: The abdominal vagus nerve was chronically implanted with an electrode array. After 2 weeks, the intestine was inflamed with TNBS (2.5% 2,4,6-trinitrobenzene sulphonic acid), an established method for rodent models of IBD. Rats were randomly selected to receive therapeutic VNS (n=7; 10 Hz; symmetric biphasic current pulse; 320 nC per phase; 3 hours/day) or no stimulation (n=8) for 5 days. Stool quality, C-reactive protein in blood and histology of the inflamed intestine were assessed. VNS off-target experiment: Abdominal VNS had no effect (two-way RM-ANOVA: P>0.05) on cardiac, respiratory and blood pressure parameters. However, during cervical VNS heart rate decreased by 31 ± 9 beats/minute (P>0.05), respiration was inhibited and blood pressure decreased. VNS efficacy experiment: During the implantation period, electrically-evoked neural response thresholds remained stable (one-way RM ANOVA: P>0.05), and were below stimulation levels. VNS rats, compared to unstimulated rats, had improved stool quality (two-way RM ANOVA: P<0.0001), no blood in faeces (P<0.0001), reduced plasma C-reactive protein (two-way RM ANOVA: P<0.05) and a reduction in resident inflammatory cell populations within the intestine (Kruskal-Wallis: P<0.05). Abdominal VNS did not evoke off-target effects, is an effective treatment of TNBS-induced inflammation, and may be an effective treatment of IBD in humans.
Chronic electrical stimulation with a peripheral suprachoroidal retinal implant: a preclinical safety study of neuroprotective stimulation.
(Frontiers, 2024-06-20) Abbott, Carla J; Allen, Penelope J; Williams, Chris E; Williams, Richard A; Epp, Stephanie B; Burns, Owen; Thomas, Ross; Harrison, Mark; Thien, Patrick C; Saunders, Alexia; McGowan, Ceara; Sloan, Caitlin; Luu, Chi D; Nayagam, David A X
Extraocular electrical stimulation is known to provide neuroprotection for retinal cells in retinal and optic nerve diseases. Currently, the treatment approach requires patients to set up extraocular electrodes and stimulate potentially weekly due to the lack of an implantable stimulation device. Hence, a minimally-invasive implant was developed to provide chronic electrical stimulation to the retina, potentially improving patient compliance for long-term use. The aim of the present study was to determine the surgical and stimulation safety of this novel device designed for neuroprotective stimulation.
Development of a Magnetic Attachment Method for Bionic Eye Applications
(Wiley Periodicals, Inc., 2016) Fox, Kate; Meffin, Hamish; Burns, Owen; Abbott, Carla; Allen, Penelope; Opie, Nicholas; McGowan, Ceara; Yeoh, Jonathon; Ahnood, Arman; Luu, Chi; Cicione, Rosemary; Saudners, Alexia; McPhedran, Michelle; Cardamone, Lisa; Villalobos, Joel; Garrett, David; Nayagam, David; Apollo, Nicholas; Ganesan, Kumaravelu; Shivdasani, Mohit; Stacey, Alastair; Escudie, Mathilde; Lichter, Samantha; Shepherd, Robert; Prawer, Stephen
Successful visual prostheses require stable, long-term attachment. Epiretinal prostheses, in particular, require attachment methods to fix the prosthesis onto the retina. The most common method is fixation with a retinal tack; however, tacks cause retinal trauma, and surgical proficiency is important to ensure optimal placement of the prosthesis near the macula. Accordingly, alternate attachment methods are required. In this study, we detail a novel method of magnetic attachment for an epiretinal prosthesis using two prostheses components positioned on opposing sides of the retina. The magnetic attachment technique was piloted in a feline animal model (chronic, nonrecovery implantation). We also detail a new method to reliably control the magnet coupling force using heat. It was found that the force exerted upon the tissue that separates the two components could be minimized as the measured force is proportionately smaller at the working distance. We thus detail, for the first time, a surgical method using customized magnets to position and affix an epiretinal prosthesis on the retina. The position of the epiretinal prosthesis is reliable, and its location on the retina is accurately controlled by the placement of a secondary magnet in the suprachoroidal location. The electrode position above the retina is less than 50 microns at the center of the device, although there were pressure points seen at the two edges due to curvature misalignment. The degree of retinal compression found in this study was unacceptably high; nevertheless, the normal structure of the retina remained intact under the electrodes.
Development of a surgical procedure for implantation of a prototype suprachoroidal retinal prosthesis
(John Wiley & Sons Inc, 2014-09) Saunders, Alexia; Williams, Chris; Heriot, Wilson; Briggs, Robert; Yeoh, Jonathan; Nayagam, David; McCombe, Mark; Villalobos, Joel; Burns, Owen; Luu, Chi; Ayton, Lauren; McPhedran, Michelle; Opie, Nicholas; McGowan, Ceara; Shepherd, Robert; Guymer, Robyn; Allen, Penelope
BACKGROUND: Current surgical techniques for retinal prosthetic implantation require long and complicated surgery, which can increase the risk of complications and adverse outcomes. METHOD: The suprachoroidal position is known to be an easier location to access surgically, and so this study aimed to develop a surgical procedure for implanting a prototype suprachoroidal retinal prosthesis. The array implantation procedure was developed in 14 enucleated eyes. A full-thickness scleral incision was made parallel to the intermuscular septum and superotemporal to the lateral rectus muscle. A pocket was created in the suprachoroidal space, and the moulded electrode array was inserted. The scleral incision was closed and scleral anchor point sutured. In 9 of the 14 eyes examined, the device insertion was obstructed by the posterior ciliary neurovascular bundle. Subsequently, the position of this neurovascular bundle in 10 eyes was characterized. Implantation and lead routing procedure was then developed in six human cadavers. The array was tunnelled forward from behind the pinna to the orbit. Next, a lateral canthotomy was made. Lead fixation was established by creating an orbitotomy drilled in the frontal process of the zygomatic bone. The lateral rectus muscle was detached, and implantation was carried out. Finally, pinna to lateral canthus measurements were taken on 61 patients in order to determine optimal lead length. RESULTS: These results identified potential anatomical obstructions and informed the anatomical fitting of the suprachoroidal retinal prosthesis. CONCLUSION: As a result of this work, a straightforward surgical approach for accurate anatomical suprachoroidal array and lead placement was developed for clinical application.
The development of neural stimulators: a review of preclinical safety and efficacy studies
(IOP Publishing, 2018-05) Shepherd, Robert; Villalobos, Joel; Burns, Owen; Nayagam, David
OBJECTIVE: Given the rapid expansion of the field of neural stimulation and the rigorous regulatory approval requirements required before these devices can be applied clinically, it is important that there is clarity around conducting preclinical safety and efficacy studies required for the development of this technology. APPROACH: The present review examines basic design principles associated with the development of a safe neural stimulator and describes the suite of preclinical safety studies that need to be considered when taking a device to clinical trial. MAIN RESULTS: Neural stimulators are active implantable devices that provide therapeutic intervention, sensory feedback or improved motor control via electrical stimulation of neural or neuro-muscular tissue in response to trauma or disease. Because of their complexity, regulatory bodies classify these devices in the highest risk category (Class III), and they are therefore required to go through a rigorous regulatory approval process before progressing to market. The successful development of these devices is achieved through close collaboration across disciplines including engineers, scientists and a surgical/clinical team, and the adherence to clear design principles. Preclinical studies form one of several key components in the development pathway from concept to product release of neural stimulators. Importantly, these studies provide iterative feedback in order to optimise the final design of the device. Key components of any preclinical evaluation include: in vitro studies that are focussed on device reliability and include accelerated testing under highly controlled environments; in vivo studies using animal models of the disease or injury in order to assess safety and, given an appropriate animal model, the efficacy of the technology under both passive and electrically active conditions; and human cadaver and ex vivo studies designed to ensure the device's form factor conforms to human anatomy, to optimise the surgical approach and to develop any specialist surgical tooling required. SIGNIFICANCE: The pipeline from concept to commercialisation of these devices is long and expensive; careful attention to both device design and its preclinical evaluation will have significant impact on the duration and cost associated with taking a device through to commercialisation. Carefully controlled in vitro and in vivo studies together with ex vivo and human cadaver trials are key components of a thorough preclinical evaluation of any new neural stimulator.
Hermetic diamond capsules for biomedical implants enabled by gold active braze alloys
(Elsevier, Ltd., 2015-03) Lichter, Samantha; Escudie, Mathilde; Stacey, Alastair; Ganesan, Kumaravelu; Fox, Kate; Ahnood, Arman; Apollo, Nicholas; Kua, Dunstan; Lee, Aaron; McGowan, Ceara; Saunders, Alexia; Burns, Owen; Nayagam, David; Williams, Richard; Garrett, David; Meffin, Hamish; Prawer, Stephen
As the field of biomedical implants matures the functionality of implants is rapidly increasing. In the field of neural prostheses this is particularly apparent as researchers strive to build devices that interact with highly complex neural systems such as vision, hearing, touch and movement. A retinal implant, for example, is a highly complex device and the surgery, training and rehabilitation requirements involved in deploying such devices are extensive. Ideally, such devices will be implanted only once and will continue to function effectively for the lifetime of the patient. The first and most pivotal factor that determines device longevity is the encapsulation that separates the sensitive electronics of the device from the biological environment. This paper describes the realisation of a free standing device encapsulation made from diamond, the most impervious, long lasting and biochemically inert material known. A process of laser micro-machining and brazing is described detailing the fabrication of hermetic electrical feedthroughs and laser weldable seams using a 96.4% gold active braze alloy, another material renowned for biochemical longevity. Accelerated ageing of the braze alloy, feedthroughs and hermetic capsules yielded no evidence of corrosion and no loss of hermeticity. Samples of the gold braze implanted for 15 weeks, in vivo, caused minimal histopathological reaction and results were comparable to those obtained from medical grade silicone controls. The work described represents a first account of a free standing, fully functional hermetic diamond encapsulation for biomedical implants, enabled by gold active alloy brazing and laser micro-machining.
In Vivo Feasibility of Epiretinal Stimulation Using Ultrananocrystalline Diamond 1 Electrodes
(IOP Publishing, 2020-07) Shivdasani, Mohit; Evans, Mihailo; Burns, Owen; Yeoh, Jonathon; Allen, Penelope; Nayagam, David; Villalobos, Joel; Abbott, Carla; Luu, Chi; Opie, Nicholas; Sabu, Anu; Saunders, Alexia; McPhedran, Michelle; Cardamone, Lisa; McGowan, Ceara; Maxim, Vanessa; Williams, Richard; Fox, Kate; Cicione, Rosemary; Garrett, David; Ahnood, Arman; Ganesan, Kumaravelu; Meffin, Hamish; Burkitt, Anthony; Prawer, Steven; Williams, Chris; Shepherd, Robert
PURPOSE: Due to their increased proximity to retinal ganglion cells (RGCs), epiretinal visual prostheses present the opportunity for eliciting phosphenes with low thresholds through direct RGC activation. This study characterised the in vivo performance of a novel prototype monolithic epiretinal prosthesis, containing Nitrogen incorporated ultrananocrystalline (N-UNCD) diamond electrodes. METHODS: A prototype implant containing up to twenty-five 120×120 µm N-UNCD electrodes was implanted into 16 anaesthetised cats and attached to the retina either using a single tack or via magnetic coupling with a suprachoroidally placed magnet. Multiunit responses to retinal stimulation using charge-balanced biphasic current pulses were recorded acutely in the visual cortex using a multichannel planar array. Several stimulus parameters were varied including; the stimulating electrode, stimulus polarity, phase duration, return configuration and the number of electrodes stimulated simultaneously. RESULTS: The rigid nature of the device and its form factor necessitated complex surgical procedures. Surgeries were considered successful in 10/16 animals and cortical responses to single electrode stimulation obtained in 8 animals. Clinical imaging and histological outcomes showed severe retinal trauma caused by the device in-situ in many instances. Cortical measures were found to significantly depend on the surgical outcomes of individual experiments, phase duration, return configuration and the number of electrodes stimulated simultaneously, but not stimulus polarity. Cortical thresholds were also found to increase over time within an experiment. CONCLUSIONS: The study successfully demonstrated that an epiretinal prosthesis containing diamond electrodes could produce cortical activity with high precision, albeit only in a small number of cases. Both surgical approaches were highly challenging in terms of reliable and consistent attachment to and stabilisation against the retina, and often resulted in severe retinal trauma. There are key challenges (device form factor and attachment technique) to be resolved for such a device to progress towards clinical application, as current surgical techniques are unable to address these issues.
Ring and peg electrodes for minimally-Invasive and long-term sub-scalp EEG recordings
(Elsevier, Ltd., 2017-06) Benovitski, Yuri; Lai, Alan; McGowan, Ceara; Burns, Owen; Maxim, Vanessa; Nayagam, David; Millard, Rodney; Rathbone, Graeme; le Chevoir, M.A.; Williams, R.A.; Grayden, David; May, C.N.; Murphy, M.; D'Souza, Wendyl; Cook, Mark; Williams, Chris
OBJECTIVE: Minimally-invasive approaches are needed for long-term reliable Electroencephalography (EEG) recordings to assist with epilepsy diagnosis, investigation and more naturalistic monitoring. This study compared three methods for long-term implantation of sub-scalp EEG electrodes. METHODS: Three types of electrodes (disk, ring, and peg) were fabricated from biocompatible materials and implanted under the scalp in five ambulatory ewes for 3months. Disk electrodes were inserted into sub-pericranial pockets. Ring electrodes were tunneled under the scalp. Peg electrodes were inserted into the skull, close to the dura. EEG was continuously monitored wirelessly. High resolution CT imaging, histopathology, and impedance measurements were used to assess the status of the electrodes at the end of the study. RESULTS: EEG amplitude was larger in the peg compared with the disk and ring electrodes (p<0.05). Similarly, chewing artifacts were lower in the peg electrodes (p<0.05). Electrode impedance increased after long-term implantation particularly for those within the bone (p<0.01). Micro-CT scans indicated that all electrodes stayed within the sub-scalp layers. All pegs remained within the burr holes as implanted with no evidence of extrusion. Eight of 10 disks partially eroded into the bone by 1.0mm from the surface of the skull. The ring arrays remained within the sub-scalp layers close to implantation site. Histology revealed that the electrodes were encapsulated in a thin fibrous tissue adjacent to the pericranium. Overlying this was a loose connective layer and scalp. Erosion into the bone occurred under the rim of the sub-pericranial disk electrodes. CONCLUSIONS: The results indicate that the peg electrodes provided high quality EEG, mechanical stability, and lower chewing artifact. Whereas, ring electrode arrays tunneled under the scalp enable minimal surgical techniques to be used for implantation and removal.
Safety Studies for a 44-Channel Suprachoroidal Retinal Prosthesis: A Chronic Passive Study
(IOVS, 2018-03) Abbott, Carla; Nayagam, David; Luu, Chi; Epp, Stephanie; Williams, Richard; Salinas-LaRosa, Cesar; Villalobos, Joel; McGowan, Ceara; Shivdasani, Mohit; Burns, Owen; Leavens, Jason; Yeoh, Jonathon; Brandli, Alice; Thien, Patrick; Zhou, Jenny; Feng, Helen; Williams, Chris; Shepherd, Robert; Allen, Penelope
Abstract Purpose: Following successful clinical outcomes of the prototype suprachoroidal retinal prosthesis, Bionic Vision Australia has developed an upgraded 44-channel suprachoroidal retinal prosthesis to provide a wider field of view and more phosphenes. The aim was to evaluate the preclinical passive safety characteristics of the upgraded electrode array. Methods: Ten normal-sighted felines were unilaterally implanted with an array containing platinum electrodes (44 stimulating and 2 returns) on a silicone carrier near the area centralis. Clinical assessments (color fundus photos, optical coherence tomography, full-field electroretinography, intraocular pressure) were performed under anesthesia prior to surgery, and longitudinally for up to 20 weeks. Histopathology grading of fibrosis and inflammation was performed in two animals at 13 to 15 weeks. Results: Eight animals showed safe electrode array insertion (good retinal health) and good conformability of the array to the retinal curvature. Eight animals demonstrated good mechanical stability of the array with only minor (<2 disc diameters) lateral movement. Four cases of surgical or stability complications occurred due to (1) bulged choroid during surgery, (2) hemorrhage from a systemic bleeding disorder, (3) infection, and (4) partial erosion of thin posterior sclera. There was no change in retinal structure or function (other than that seen at surgery) at endpoint. Histopathology showed a mild foreign body response. Electrodes were intact on electrode array removal. Conclusions: The 44-channel suprachoroidal electrode array has an acceptable passive safety profile to proceed to clinical trial. The safety profile is expected to improve in human studies, as the complications seen are specific to imitations (anatomic differences) with the feline model.
Vagus nerve stimulation to treat inflammatory bowel disease: a chronic, preclinical safety study in sheep
(Future Medicine, 2019-02) Payne, Sophie; Burns, Owen; Stebbing, Martin; Thomas, Ross; de Silva, Angel; Sedo, Alicia; Weissenborn, Frank; Hyakumura, Tomoko; Huynh, Mario; May, Clive; Williams, Richard; Furness, John; Fallon, James; Shepherd, Robert
Aim: Electrical stimulation of the left cervical vagus nerve is a feasible therapy for inflammatory bowel disease (IBD). However, due to the location of the electrode placement, stimulation is often associated with side effects. Methods: We developed a cuff electrode array, designed to be implanted onto the vagus nerve of the lower thorax or abdomen, below branches to vital organs, to minimize off-target effects to stimulation. Results: Following chronic implantation and electrical stimulation, electrodes remained functional and neural thresholds stable, while there were minimal off-target affects to stimulation. No nerve damage or corrosion of stimulated electrodes was observed. Conclusion: This novel electrode array, located on the vagus nerve below branches to vital organs, is a safe approach for the treatment of inflammatory bowel disease.

Browsing by Author "Burns, Owen"

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