Programmable self-assembly of carbon nanotubes assisted by reversible denaturation of a protein

Abstract

Self-assembly of pristine multi-walled carbon nanotubes (CNTs) in aqueous dispersion using a protein, bovine serum albumin (BSA), has been demonstrated. Step-wise conformational changes in BSA as a function of temperature have been deployed to direct the assembly of nanotubes. More specifically, CNTs distributed randomly in native BSA at 35 °C as well as completely denatured BSA solution at 80 °C self-assemble in the intermediate temperature range of 45-65 °C, as evident from scanning and transmission electron microscopy. Fourier transform infrared (FTIR) and fluorescence studies indicate significant changes in the α-helical content of the protein with respect to the amide I and II bands and tryptophan emission intensity, respectively. The stability of CNT dispersion in BSA solution has been attributed to the hydrophobic interaction between nanotubes and the protein molecule by adding sodium cholate to the dispersion. Moreover, a mechanism based on electrostatic repulsion between BSA-bound CNTs has been proposed for the thermally reversible assembly of CNTs in BSA solution based on evidence from zeta potential measurements and FTIR spectroscopy. Thus the present report demonstrates bio-mimetic self-assembly of as-synthesized CNTs using changes in surface charge and conformation of an unfolding protein for biomedical applications and nanobiotechnology.

Selective Assembly of DNA-Conjugated Single-Walled Carbon Nanotubes from the Vascular Secretome

“…Our study of aggregation also opens the door to various potential applications. Compared to previous BSA–SWCNT studies, our EM showed much higher protein density per SWCNT . Combined with aggregate preferences for protein types, there is potential to utilize aggregation for the detection , and extraction of low-concentration species.…”

“…Compared to previous BSA–SWCNT studies, our EM showed much higher protein density per SWCNT. 53 Combined with aggregate preferences for protein types, there is potential to utilize aggregation for the detection 54 , 55 and extraction of low-concentration species. Lastly, the new understanding of temperature-dependent DNA–SWCNT associations can lead to novel methods of bioresponsive self-assembly.…”

Particle formation pathways and polymorphism of curcumin induced by ultrasound and additives during liquid antisolvent precipitation

“…BSA at pH 6.5 (all the experiments in this work had a suspension pH in the range of 6-7) contains only deprotonated hydroxyl groups (-COOH) on the surface, whereas -NH 2 groups are embedded within the globular structure of BSA. 32 Therefore, BSA can interact at the ends of the curcumin molecule at phenolic -OH and methoxyl groups resulting in a quick arrest of curcumin particle growth in all directions (schematic shown in Fig. 10).…”

Bioimpact of Carbon Nanomaterials

“…Being hydrophobic in nature, CNTs are subjected to van der Waals interactions, which results in them being found in the form of selfassembled aggregates, which makes them quite insoluble in water. Nithiyasri et al [227] have investigated the possibility of self-assembling CNTs in aqueous dispersions using a water-soluble protein; bovine serum albumin (BSA). …”

“…They concluded that CNTs selfassemble in the intermediate temperature range of 45-65°C in both native BSA at 35°C, as well as denatured BSA solution at 80°C[227].…”