Biology subjects

Alrashdan, F.

Publications and source records attributed to Alrashdan, F..

4 recordsLinked to original sources

bioRxiv2023

Endocisternal interfaces for minimally invasive neural stimulation and recording of the brain and spinal cord

Minimally invasive neural interfaces can be used to diagnose, manage, and treat many disorders with substantially reduced risks of surgical complications. Endovascular neural interfaces implanted in the veins or arteries is one approach, but it requires prescriptions of anti-thrombotic medication and are likely not explantable after endothelialization. More critically, the approach is limited by the small size and location of blood vessels, such that many important cortical, subcortical, spinal targets cannot be reached. Here, we demonstrate a chronic endocisternal neural interface that approaches brain and spinal cord targets through inner and outer cerebral spinal fluid (CSF) spaces. These spaces surround the nervous system and lack the tortuosity of the circulatory system, giving us access to the entire brain convexity, deep brain structures within the ventricles, and the spinal cord from the spinal subarachnoid space. Combined with miniature magnetoelectric-powered bioelectronics, the entire wireless system is deployable through a percutaneous procedure. The flexible catheter electrodes can be freely navigated throughout the body from the spinal to cranial subarachnoid space, and from the cranial subarachnoid space to the ventricles. We show in a large animal model that we can also reposition the recording and stimulation electrodes or explant the neural interface after chronic implantation. This enables applications in therapies that require transient or permanent brain/machine interface such as stroke rehabilitation and epilepsy monitoring and opens a new class of minimally invasive endocisternal bioelectronics.

bioengineering↗

bioRxiv2023

Magnetoelectrics Enables Large Power Delivery to mm-Sized Wireless Bioelectronics

To maximize the capabilities of minimally invasive implantable bioelectronic devices, we must deliver large amounts of power to small implants; however, as devices are made smaller, it becomes more difficult to transfer large amounts of power without a wired connection. Indeed, recent work has explored creative wireless power transfer (WPT) approaches to maximize power density (the amount of power transferred divided by receiver footprint area (length x width)). Here, we analyzed a model for WPT using magnetoelectric (ME) materials that convert an alternating magnetic field into an alternating voltage. With this model, we identify the parameters that impact WPT efficiency and optimize the power density. We find that improvements in adhesion between the laminated ME layers, clamping, and selection of material thicknesses lead to a power density of 3.1 mW/mm2, which is over 4 times larger than previously reported for mm-sized wireless bioelectronic implants at a depth of 1 cm or more in tissue. This improved power density allows us to deliver 31 mW and 56 mW to 10-mm2 and 27-mm2 ME receivers, respectively. This total power delivery is over 5 times larger than similarly sized bioelectronic devices powered by radiofrequency electromagnetic waves, inductive coupling, ultrasound, light, capacitive coupling, or previously reported magnetoelectrics. This increased power density opens the door to more power-intensive bioelectronic applications that have previously been inaccessible using mm-sized battery-free devices.

neuroscience↗

bioRxiv2022

Self-rectifying magnetoelectric metamaterials enable precisely timed remote neural stimulation and restoration of sensory motor functions

Magnetoelectric materials convert magnetic fields to electric fields and have applications in wireless data and power transmission, electronics, sensing, data storage, and biomedical technology. For example, magnetoelectrics could enable precisely timed remote stimulation of neural tissue, but the resonance frequencies where magnetoelectric effects are maximized are typically too high to stimulate neural activity. To overcome this challenge, we created the first self-rectifying magnetoelectric "metamaterial." This metamaterial relies on nonlinear charge transport across semiconductor layers that allow the material to generate a steady bias voltage in the presence of an alternating magnetic field. This "self-rectification" allows us to generate arbitrary electrical pulse sequences that have a time-averaged voltage in excess of 1 V. As a result, we can use magnetoelectric nonlinear metamaterials (MNMs) to remotely stimulate peripheral nerves with repeatable latencies of less than 5 ms, which is more than 120 times faster than previous neural stimulation approaches based on magnetic materials. These short latencies enable this metamaterial to be used in applications where fast neural signal transduction is necessary such as in sensory or motor neuroprosthetics. As a proof of principle, we show wireless stimulation to restore a sensory reflex in an anesthetized rat model as well as using the MNM to restore signal propagation in a severed nerve. The rational design of nonlinearities in the magnetic-to-electric transduction pathway as described here opens the door to many potential designs of MNMs tailored to applications spanning electronics, biotechnology, and sensing.

bioengineering↗

bioRxiv2021

Wireless endovascular nerve stimulation with a millimeter-sized magnetoelectric implant

Implanted bioelectronic devices have the potential to treat disorders that are resistant to traditional pharmacological therapies; however, reaching many therapeutic nerve targets requires invasive surgeries and implantation of centimeter-sized devices. Here we show that it is possible to stimulate peripheral nerves from within blood vessels using a millimeter-sized wireless implant. By directing the stimulating leads through the blood vessels we can target specific nerves that are difficult to reach with traditional surgeries. Furthermore, we demonstrate this endovascular nerve stimulation (EVNS) with a millimeter sized wireless stimulator that can be delivered minimally invasively through a percutaneous catheter which would significantly lower the barrier to entry for neuromodulatory treatment approaches because of the reduced risk. This miniaturization is achieved by using magnetoelectric materials to efficiently deliver data and power through tissue to a digitally-programmable 0.8 mm2 CMOS system-on-a-chip. As a proof-of-principle we show wireless stimulation of peripheral nerve targets both directly and from within the blood vessels in rodent and porcine models. The wireless EVNS concept described here provides a path toward minimally invasive bioelectronics where mm-sized implants combined with endovascular stimulation enable access to a number of nerve targets without open surgery or implantation of battery-powered pulse generators.

bioengineering↗