Anisotropic natural nanostructures occurring in the several organisms in nature possessing structural color have gained more and more attention because of its obvious advantages in sensitivity, stability, security, miniaturization, portability, online use and remote monitoring. Due to the development of research on nature-inspired bionic structures, as well as demand for high-efficient low-cost microfabrication techniques, understanding and replicating the mechanism of structural coloration have become increasingly significant. These sophisticated structures have many unique functions and can be used for many applications. Many sensors have been proposed based on their novel structure and unique optical properties. A lot of these bio-inspired sensors for infrared radiation/thermal, pH, vapor etc. have been discussed in detail, with intense focus on several biomedical applications, anyway there still a lot of application yet to be discovered.
In thesis review, we will describe these nanostructure materials based on their sources in nature and the varieties of their structure, as layered, hierarchical, helical structures and so on. Beside we discuss the functions endowed by these structures, such as superamphiphobic, adhesion, and high-strength, etc., and have been put them into number of applications in biomedical fields, which involve in cell cultivation, biosensors and tissue engineering. This research mainly focuses on the anisotropic nanostructures of butterfly wings biomedical application in cell regulating and wearable biosensor, and the main achievements are summarized as follows:
1) A simple and green method was developed by utilizing butterfly wings (Morpho menelaus, Papilio ulysses telegonus and Ornithoptera croesus lydius) with natural anisotropic nanostructures to generate cell alignment. A two-step chemical treatment was proposed to achieve more hydrophilic butterfly wings preceding cell culturing. Furthermore, calcein acetoxymethyl ester (Calcein-AM) staining and Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay results demonstrated the appropriate viability of NIH-3T3 fibroblast cells on those butterfly wings. Moreover, the cells displayed a high degree of alignment in each specimen of these wings. We anticipate that those originating from natural butterfly wings will pose important applications for tissue engineering.
2) We describe a good 3D model for the hepatocyte growth and aggregate formation with maintaining the function of the hepatocytes based on the natural anisotropic nanostructures derivate from butterfly wings. These substrates which previously introduced by us in a simple, inexpensive and green method and NIH-3T3 fibroblast cells cultured on these substrates was shown a high degree of alignment along the direction of the ridges, here these natural substrates show an important role in the final tissue model or cell aggregates of hepatocyte as well. We anticipate that these natural, biodegradable and biocompatible substrates maintain a hepatic culture model in a potential therapeutic application and can participate in future development of regenerative tissues.
3) Motivated by Morpho menelaus wing unique structures and extraordinary functionalities of its ordered structures, biosensor based on butterfly wings was presented. Flexible Morpho menelaus-based wearable sensors were integrated with a microfluidic system and electronic networks to facilitate the diagnosis of neurodegenerative disease (ND). In the microfluidic section, the structural characteristics of the Morpho menelaus wings up layer were combined with SiO2 nanoparticles to form a heterostructure, the fluorescent enhancement property of the heterostructure is used to increase the fluorescent intensity for multiplex detection of two proteins: IgG and AD7c-NTP. For the electronic section, conductive ink was blade-coated on the under layer of wing for measuring resistance change rate to obtain the frequency of static tremors of ND patients. The disposable Morpho menelaus-based flexible microfluidic and electronic sensor enables biochemical–physiological hybrid monitoring of ND. The sensor is also amenable to a variety of applications, such as comprehensive personal healthcare and human–machine interaction.