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Carbon Nanotube-Wrapped Spider Silks for Directed Cardiomyocytes Growth and Electrophysiological Detection Junfeng Hou, Yu Xie, Aiguo Ji, Anyuan Cao, Ying Fang, and Enzheng Shi ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b14793 • Publication Date (Web): 09 Feb 2018 Downloaded from http://pubs.acs.org on February 11, 2018
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ACS Applied Materials & Interfaces
Carbon Nanotube-Wrapped Spider Silks for Directed Cardiomyocytes Growth and Electrophysiological Detection Junfeng Hou,
†§
†
Yu Xie, ∥ AiGuo Ji, *Anyuan Cao,∥ Ying Fang,§ Enzheng Shi∥‡*
† School of Ocean, Shandong University, Weihai 264209, China § National Center for Nanoscience and Technology, 11 Beiyitiao Street, Zhongguancun, Beijing 100190, P.R. China ∥Department
of Materials Science and Engineering, College of Engineering, Peking University,
Beijing 100871, P. R. China
KEYWORDS:
Carbon
nanotube, spider silk, bio-sensors,
electrochemical
detection,
cardiomyocytes
ABSTRACT: Combination of nanostructures with biomaterials offers great opportunities in constructing innovated functional devices such as bio-sensors and actuators. Here, we create a multifunctional fiber by wrapping a thin film of carbon nanotubes (CNTs) on naturally found
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spider silks, which shows great flexibility and conductivity. The hybrid CNT-silk fiber demonstrates intimate contact with cardiomyocytes and can direct the cell growth and simultaneously record potential signals evoked from cell beating. Cell activities reflected in the form of potential signals have been monitored clearly and reliably through the CNT-silks, without degradation over a long term.
TEXT: Biomedical applications of nanomaterials have stimulated tremendous interest in recent years.1 Among various nanoscale material, carbon nanotubes are chemically stable and electrically conductive, and have been studied in biological and medical areas either at individual level or in macroscopic self-assembled structures.2 CNT films, fibers, coatings, and threedimensional (3D) electrodes could serve as structural supports for cell culture and tissue engineering, and in general they were found to create a favorable environment and promote cell attachment and subsequent growth, differentiation as well as long-term survival.3,4 For example, it was observed that CNTs formed tight contacts with rat ventricular myocytes and increased syncytia development and electrical activity of cardiomyocytes.5 Also, a CNT coating on metal electrodes could boost electrophysiological signals from neurons and cardiac myocytes, suggesting effective coupling between CNTs and excitable cells.6-8 The versatility of CNT-based materials (including films, fibers, 3D structures) together with their high conductivity allow the configuration of many different bio-sensors and actuators with high performance. Despite of such a great promise, it remains challenging to develop functional CNT devices that are fully compatible to biological systems. Conventional substrates (e.g. metals, ceramics) are too rigid or hard to soft tissues; CNTs must be anchored in appropriate substrates that offer high flexibility and compliance to surrounding media. In this regard, spider silks could be appropriate
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ACS Applied Materials & Interfaces
choices since they are light-weight, mechanically strong and stretchable in tension (with tensile strength and strain up to 4.8 GPa and 35%, respectively), and extremely soft as well9. In fact, spider silks have been used as a natural protein to prevent infection and heal wounds in folk medicine for more than 2000 years10 Recent studies also demonstrated their potential applications in cell interfacing and tissue engineering, in which spider silks could enhance cell growth, proliferation, and nerve regeneration11,12. Based on the investigation of the interaction between CNTs and excitable cells reported by several groups,13-16 the CNTs provided a soft artificial extracellular matrix which may ultimately facilitate cell adhesion by the formation of tight contacts between CNTs and cell membrane, which were clearly confirmed by TEM or SEM data. Coupled with the recent results, which showed CNTs enhance disc assembly in cardiac myocytes by activating β1-integrin signaling at the cell membrane and the subsequent signaling kinases,17 we speculate that the nanotopographical features and the conductivity improvement of CNTs substrates could induce and guide cell adhesion, and CNTs-based scaffolds have the ability to improve cardiomyocytes proliferation, maturation, and electrical behavior by providing a desired artificial extracellular matrix and by regulating protein expression, which is superior to other substrates like Silicon and gold. Herein, we combine CNTs and spider silks to fabricate robust and conducting hybrid fibers that contact well with growing cells and enable in-situ detection of cell activity. The hybrid fiber takes full advantages of these two materials, particularly the high conductivity of CNTs and the biocompatibility of spider silks, to enable high-performance multifunctional devices. With this combination, we demonstrate fiber-shaped bio-sensors that can detect electrophysiological signals from cultured cardiomyocytes reliably and with high sensitivity over a long period.
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Our fabrication of carbon nanotube-wrapped spider silks was based on a dry-coating and wetcollapsing method. Nephila Clavata spider dragline silks were collected in the campus. Each bundle of dragline silk could be separated into several single silks (Figure S1). These spider silks have diameters ranging from 5 to 10 µm and lengths up to a few meters. Several factors related to our fabrication process are important and would facilitate subsequent applications. First, we used freestanding CNT films to directly wrap each individual spider silk over centimeter length without interruption (Figure 1a). The CNT films synthesized by chemical vapor deposition are highly conductive with few defects, as indicated by the high G/D ratio in Raman spectrum (Figure 1b), creating a continuously conducting path along spider silks. Second, the CNT film consisting of interconnected CNT bundles is very thin (thickness
