is of great significance for the diagnosis and pathological research of neurological diseases. It is also a key technology for humans to understand the brain and decipher the brain's operating mechanism and cognitive functions. Compared with traditional neural signal detection technology assisted by imaging equipment, neural interface technology implemented through neural electrodes has better spatiotemporal resolution and can conduct in-situ acquisition and real-time monitoring of various electrophysiological signals in the brain. However, most of the neural electrodes currently used clinically are rigid electrodes based on inorganic materials. There is a huge difference between the mechanical properties of the neural electrodes and neural tissue , and has poor biocompatibility and can easily cause brain tissue damage and inflammatory reactions. Advances in polymer materials and their processing technologies provide new opportunities for the development of a new generation of flexible neural interfaces. Among them, active polymer thin-layer materials with good flexibility, biocompatibility and processing adaptability can better achieve conformal contact with irregular curved tissues (conformal contract), and effectively alleviate chronic inflammation caused by implants. They are ideal materials for constructing long-term implanted neural interfaces.
Figure 1. A brief history of the development of neural interfaces
Recently, the team of Professor Zhang Yaopeng and Associate Professor Yao Xiang of the National Key Laboratory of Fiber Material Modification of Donghua University systematically summarized the cutting-edge research progress related to the construction and application strategies of bioactive polymer-based neural interfaces from three aspects: material selection , neural interface structural design , and interface integration strategy (Figure 2), and analyzed its development prospects and challenges. Relevant results were published on Materials Horizons under the title Bioactive polymer-enabled conformal neural interface and its application strategies. Doctoral student Hu Zhanao of Donghua University is the first author. Postdoctoral fellow Niu Qianqian of Donghua University and Professor Benjamin S. Hsiao of the State University of New York at Stony Brook are co-authors. Professor Zhang Yaopeng and Associate Professor Yao Xiang are co-corresponding authors.
Figure 2. Three core considerations for preparing flexible neural interfaces
First, this review briefly introduces the development process of neural interfaces , neural signal acquisition methods and response characteristics of neural tissue to related implants , emphasizing the importance of biocompatibility and flexibility of neural interface building materials to maintain long-lasting and effective operation of neural interfaces in the body. Electrocortical electroencephalography (ECoG), as a neural signal acquisition method with both low invasiveness and high signal-to-noise ratio, has received extensive research and attention. This article further comprehensively analyzes and summarizes the development and application progress of the above-mentioned bioactive polymer-based ECoG neural interfaces by taking silk fibroin (SF) (Figure 3), cellulose and their derivatives as representatives of biopolymer materials, and using polyimide, polydimethylsiloxane (PDMS), etc. as representatives of synthetic polymers. In addition, this article also systematically discusses the impact of material selection, interface structure design and neural interface integration strategy on the comprehensive performance of neural interfaces: In order to alleviate chronic inflammation caused by neural interface implantation, biopolymers such as SF and cellulose have good biocompatibility, biodegradability/absorbability and mechanical flexibility, and can be used to construct ideal neural interface substrates and packaging materials; in order to further improve the neural interface and assembly Conformal contact between tissues and signal acquisition efficiency can be achieved through reasonable structural design, such as kirigami structures and sinusoidal structures, to give the neural interface excellent stretchability, thereby better adapting to the dynamic physiological movement of the tissue. At the same time, two strategies are provided that are applicable to the integration and encapsulation of biopolymer-based neural interfaces, with a view to providing guidance for the development and optimization of more bioactive polymer-based neural interfaces (Figure 4).
Figure 3. From SF to SF-based neural interface
Figure 4. Two integration/encapsulation strategies for bioactive polymer-based flexible neural interfaces (a, c) "sandwich" structure; (b, d) passivated structure
In order to achieve long-term effective monitoring of neural activity or electrical stimulation of neural interfaces after implantation, and to expand its practical application in the fields of neurological disease diagnosis and human-computer interaction, this article proposes the following development prospects and challenges:
(1) The biocompatibility of neural interfaces needs to be further improved. During the raw material extraction and interface manufacturing process, the relevant processes need to be further optimized and a complete supervision system established to ensure that the prepared neural interface does not contain harmful chemical components, thereby avoiding the risk of brain damage and inflammation caused by implants. In addition, surface grafting/modification technology can also be used to improve the affinity of the neural interface for target neurons and reduce the adhesion and proliferation of unintended neural cells (such as glia) around the neural interface. The performance of
(2) neural interface interface impedance , signal transduction and long-term electrical stability needs to be further improved. For example, tissues transmit bioelectric signals through ions, while metals transmit charges through electrons. Therefore, the transduction mechanism at the interface-tissue interface is an ion-to-electron conversion process and vice versa. Developing effective bioactive hydrogels or elastomers to facilitate ion-electron signal transduction is an important direction in developing efficient and electrically stable neural interfaces.
(3) Flexibility regulation of bioactive polymers deserves further study. The modulus of most flexible polymeric materials (<100>1 GPa), but still higher than the modulus of real brain tissue (~1 kPa). Using conductive polymers to replace traditional metal conductors can effectively reduce the overall modulus of neural interfaces, but the number of channels supported by this type of interface needs to be further increased. In addition, the durability of polymer materials in the body and their degradation after implantation also need to be comprehensively considered and studied.
This work was funded by the National Natural Science Foundation , the Shanghai Excellent Academic Leader Project, and the Shanghai Science and Technology Commission International Cooperation Fund project.
In recent years, Professor Zhang Yaopeng's team has focused on the research of silk fibroin materials in the fields of biomedical materials and electronic devices, and has published a series of research results (J. Mater. Chem. A, 2020; 8, 25323; Mater. Horiz., 2021, 8, 3281-3294; Adv. Fiber Mater., 2022; 4, 758-773;Compos. Part B-Eng., 2022; 235, 109764;ACS Appl. Mater. Interfaces, 2022; 14, 123-137;Nano Energy, 2022, 96, 107101;Mater. Today, Bio., 2022, 221, 146;Acta Biomater., 2022, 153, 68-84)
--recommendation number--
Original link:
https://doi.org/10.1039/D2MH01125E
Source: Donghua Biomass Material Molding and Processing Research Group
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-