Flexible nanoelectrodes can “pave the way” for higher-resolution stimulation devices

Lan Luan, Robin Kim, Roy Lycke and Chong Xie (left to right) are all part of the Rice University team who produced this research

Engineers at Rice University (Houston, USA) have created nanoelectrodes that are minimally invasive and exceptionally flexible—and, as such, have the potential to function as an implanted platform, enabling long-term, high-resolution neurostimulation therapy.

As per a statement from Rice University, traditional, implantable medical devices intended for brain stimulation “frequently possess a rigidity and bulkiness that is incongruous with one of the human body’s most supple and fragile tissues”. A study now published in Cell Reports by a team of the university’s engineers was conducted in response to this issue.

The study revealed that minute, implantable devices were able to establish stable and enduring tissue-electrode interfaces in rodents, with minimal scarring or deterioration. The devices were also capable of delivering electrical pulses that closely resembled neuronal signalling patterns and amplitudes, “surpassing the capabilities of traditional intracortical electrodes”, according to Rice University.

The statement adds that, due to their exceptional biocompatibility and precise spatiotemporal stimulus control, these devices have the potential to facilitate the advancement of novel brain stimulation therapies. Such therapies, including neuronal prostheses, could greatly benefit individuals with impaired sensory or motor functions.

“When a larger current is employed, neuron activation becomes more widespread and diffuse,” said Lan Luan (Rice University, Houston, USA), a corresponding author on the study. “However, we successfully reduced the current and demonstrated a significantly more focused activation. This achievement can pave the way for the development of higher-resolution stimulation devices.”

Luan explained that the research paper utilises imaging, behavioural and histological methods to demonstrate the enhanced effectiveness of stimulation achieved by these tissue-integrated electrodes. The electrodes have the capability to administer precise and minute electrical pulses, thereby facilitating controlled neural activity excitation.

The team of researchers successfully achieved a significant reduction in the required current for neuronal activation—meaning that the electrical pulses delivered by the electrodes can be as subtle as a duration of around two hundred microseconds, and an amplitude of one or two microamps. Such precise and low-intensity stimulation holds “great potential” for advancing the field of brain stimulation therapies, Rice University claims.

The electrode design developed by researchers at the Rice Neuroengineering Initiative marks a “substantial advancement” compared to traditional implantable electrodes utilised for treating conditions like Parkinson’s disease, epilepsy, and obsessive-compulsive disorder, the release adds, as conventional electrodes often lead to “adverse tissue reactions and unintended alterations in neural activity”. This new electrode design aims to address these challenges by enhancing the effectiveness and safety of treatments for such neurological conditions.

Chong Xie (Rice University, Houston, USA), who is also a corresponding author of the study, stated that traditional electrodes are highly invasive in nature, and typically activate thousands or even millions of neurons simultaneously.

“When all these neurons are stimulated simultaneously, their individual functions and coordination, which are supposed to follow specific patterns, get disrupted,” he explained. “While this simultaneous stimulation may have the desired therapeutic effect in certain cases, it lacks the necessary precision and control, especially when it comes to encoding sensory information. To achieve more precise and effective outcomes, greater control over the stimuli is essential.”

Drawing a comparison between the more generalised stimulation provided by traditional electrodes, and the potential benefits of this new technology regarding specificity and precision, he added that “we used to have this very big loudspeaker, and now everyone has an earpiece”.

The capacity to modify the frequency, duration and intensity of the signals holds the potential for the advancement of innovative prosthetic devices, whereby electrode arrays are implanted to restore impaired sensory function, the statement further claims. On this point, Luan highlights that the precision and specificity of neuron activation play a crucial role in generating accurate and precise sensations—and emphasises that, the more focused and deliberate the activation of neurons, the higher the level of precision in the generated sensation.

Luan also commented on the significance of the ultra-flexible design of the Rice team’s electrode in achieving enhanced tissue integration. In addition, they have published a series of research papers demonstrating its capability to facilitate improved recording of brain activity over extended periods, yielding superior signal-to-noise ratios.


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