Carbon Nanotubes/Regenerated Silk Composite as a Three-Dimensional Printable Bio-Adhesive Ink with Self-Powering Properties.

Silvia Bittolo Bon,Antonino Morabito,Rodolfo Tonin,Carmelo De Maria,Riccardo Coletta,Amelia Morrone,Irene Chiesa,Francesco Saverio Pavone,Luca Valentini,Micaela Degli Esposti,Davide Morselli,Martino Calamai,Giacomo Giorgi,Paola Fabbri

doi:10.1021/acsami.1c03288

Abstract

In this study, regenerated silk (RS) obtained from Bombyx Mori cocoons is compounded with carboxyl-functionalized carbon nanotubes (f-CNTs) in an aqueous environment for the fabrication of functional bio-adhesives. Molecular interactions between RS and carboxyl groups of CNTs result in structural increase of the β-sheet formation, obtaining a resistant adhesive suitable for a wet biological substrate. Moreover, the functionalization of CNTs promotes their dispersion in RS, thus enabling the production of films with controlled electrical conductivity. The practical utility of such a property is demonstrated through the fabrication of a piezoelectric device implanted in a rat to monitor the breathing in vivo and to be used as a self-powered system. Finally, RS/f-CNTs were used as a printable biomaterial ink to three dimensionally print bilayer hollow tubular structures composed of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and RS. Initial tests carried out by seeding and growing human skin fibroblasts demonstrated that the 3D printed bilayer hollow cylindrical structures offer a suitable surface for the seeded cells to attach and proliferate. In general, the herein proposed RS/f-CNT composite serves as a versatile material for solvent-free dispersion processing and 3D printing, thus paving a new approach to prepare multifunctional materials with potential applications of great interest in sealing biological substrates and implantable devices for regenerative medicine.

Highlights

Unfunctionalized carbon nanotubes (CNTs) and functionalized carbon nanotubes (f-CNTs) were compounded with regenerated silk (RS) in a water environment to get a stable black dispersion that was used as an adhesive
The cells adhered on both structures and exhibited a healthy nuclear and overall shape and dimension. These findings indicate a favorable cell interaction with RS/f-CNTs and PHBV, and it is a prerequisite for designing 3D architectures for regenerative medicine experiments with these biomaterial inks
Thin solid films made of RS/fCNTs exhibited an enhanced conductivity that makes possible the fabrication of a piezoelectric force sensor to monitor physiological forces

Summary

INTRODUCTION

Adhesives have gained increasing interest in many surgical applications.[1−9] Synthetic adhesives (i.e., Coseal, DuraSeal, and Tisseel), for example, are currently used as sealants in anastomosis, that is a new connection between two body structures that carry fluid.[10,11] the lack of adhesion on a wet surface as well as the elastic modulus mismatch between the substrate and adhesive film still make the development of a suitable material quite a challenging task.[12,52]. Carbon nanotubes (CNTs) are a conductive nanomaterial with excellent mechanical properties.[18,19] In addition, CNTs have been demonstrated to be biocompatible[20,21] and have already been used as a 3D printing ink in the fabrication of green electronic devices and biosensors.[22−24] For example, Wei et al fabricated an integrated strain sensor via extrusion-based 3D printing for in situ monitoring of finger flexion, knee flexion, and respiration by resuspending CNTs into polyacrylic acid and sodium alginate.[25] Due to their hydrophobic nature, CNTs are difficult to disperse in aqueous environments if not properly functionalized. To further demonstrate the versatility of the developed compound, RS/fCNTs have been used as a biomaterial ink for the 3D printing of bilayer hollow cylindrical structures with potential applications in tissue engineering

EXPERIMENTAL SECTION

RESULTS AND DISCUSSION

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES