Synthesis and characterization of conductive flexible cellulose carbon nanohorn sheets for human tissue applications

Background: Conductive sheets of cellulose and carbon nanomaterials and its human skin applications are an interesting research aspect as they have potential for applications for skin compatibility. Hence it is needed to explore the effects and shed light on these applications. Method: To fabricate wearable, portable, flexible, lightweight, inexpensive, and biocompatible composite materials, carbon nanohorns (CNHs) and hydroxyethylcellulose (HEC) were used as precursors to prepare CNH-HEC (Cnh-cel) composite sheets. Cnh-cel sheets were prepared with different loading concentrations of CNHs (10, 20 50,100 mg) in 200 mg cellulose. To fabricate the bio-compatible sheets, a pristine composite of CNHs and HEC was prepared without any pretreatment of the materials. Results: The obtained sheets possess a conductivity of 1.83 × 10^{− 10} S/m and bio-compatible with human skin. Analysis for skin-compatibility was performed for Cnh-cel sheets by h-CLAT in vitro skin sensitization tests to evaluate the activation of THP-1 cells. It was found that THP-1 cells were not activated by Cnh-cel; hence Cnh-cel is a safe biomaterial for human skin. It was also found that the composite allowed only a maximum loading of 100 mg to retain the consistent geometry of free-standing sheets of < 100 μm thickness. Since CNHs have a unique arrangement of aggregates (dahlia structure), the composite is homogeneous, as verified by transmission electron microscopy (TEM) and, scanning electron microscopy (SEM), and other functional properties investigated by Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), conductivity measurement, tensile strength measurement, and skin sensitization. Conclusion: It can be concluded that cellulose and CNHs sheets are conductive and compatible to human skin applications.