Optimization of single-walled carbon nanotube solubility by noncovalent PEGylation using experimental design methods

Abstract

In this study, noncovalent functionalization of single-walled carbon nanotubes (SWCNTs) with phospholipid-polyethylene glycols (Pl-PEGs) was performed to improve the solubility of SWCNTs in aqueous solution. Two kinds of PEG derivatives, ie, Pl-PEG 2000 and Pl-PEG 5000, were used for the PEGylation process. An experimental design technique (D-optimal design and second-order polynomial equations) was applied to investigate the effect of variables on PEGylation and the solubility of SWCNTs. The type of PEG derivative was selected as a qualitative parameter, and the PEG/SWCNT weight ratio and sonication time were applied as quantitative variables for the experimental design. Optimization was performed for two responses, aqueous solubility and loading efficiency. The grafting of PEG to the carbon nanostructure was determined by thermogravimetric analysis, Raman spectroscopy, and scanning electron microscopy. Aqueous solubility and loading efficiency were determined by ultraviolet-visible spectrophotometry and measurement of free amine groups, respectively. Results showed that Pl-PEGs were grafted onto SWCNTs. Aqueous solubility of 0.84 mg/mL and loading efficiency of nearly 98% were achieved for the prepared Pl-PEG 5000-SWCNT conjugates. Evaluation of functionalized SWCNTs showed that our noncovalent functionalization protocol could considerably increase aqueous solubility, which is an essential criterion in the design of a carbon nanotube-based drug delivery system and its biodistribution.

In Vitro Evaluation of DSPE-PEG (5000) Amine SWCNT Toxicity and Efficacy as a Novel Nanovector Candidate in Photothermal Therapy by Response Surface Methodology (RSM)

“…However, it is necessary to promote carbon nanotubes’ biocompatibility in a biological medium [ 52 ]. DSPE-PEG is one of the most used polymers with a suitable safety profile, and also improves the aqueous solubility of insoluble materials [ 45 , 53 ]. DSPE-PEG might be either adsorbed or covalently bonded to the surface of SWCNTs.…”

“…Then, for homogenization, the suspension was sonicated on ice with an ultrasonic processor using 100% amplitude and 120 W power (UP200Ht Hielsher, Hielscher, Germany) for 2 min (20 s pulse and 10 s pause). To separate non-PEGylated SWCNTs from the supernatant, the suspension was centrifuged at 20,000 rpm (Beckman, IN, USA) at room temperature for 4 h. Finally, the DSPE-PEG (5000) amine/SWCNT concentration in the supernatants was determined by the spectrophotometric method at 280 nm [ 44 , 45 ]. A TNBSA test was performed to determine free amino groups on DSPE-PEG (5000) amine loaded onto SWCNTs [ 44 , 45 ].…”

“…To separate non-PEGylated SWCNTs from the supernatant, the suspension was centrifuged at 20,000 rpm (Beckman, IN, USA) at room temperature for 4 h. Finally, the DSPE-PEG (5000) amine/SWCNT concentration in the supernatants was determined by the spectrophotometric method at 280 nm [44,45]. A TNBSA test was performed to determine free amino groups on DSPE-PEG (5000) amine loaded onto SWCNTs [44,45]. Thermogravimetric analysis (TGA) was also performed for pure SWCNTs and DSPE-PEG (5000) amine SWCNTs (functionalized SWCNTs) up to 600 • C. Accordingly, this analysis was performed using a TGA-50 instrument (Shimazu, Tokyo, Japan).…”

Repression of Multiple Myeloma Cell Growth In Vivo by Single-wall Carbon Nanotube (SWCNT)-delivered MALAT1 Antisense Oligos

“…A suitable modification on the surface of SWCNTs can help it get reliable dispersibility in physiologically relevant, aqueous environments and promote their biodistribution 28,29 . We used DSPE-PEG2000-amine to modify the SWCNT, which has been demonstrated to graft on SWCNT and improve the aqueous solubility of it, and furthermore, it showed excellent stability without agglomeration in biological media 30 . Sulfo-LC-SPDP was used as a crosslinker in the experiment, which helped functionalized SWCNT to bind the anti-MALAT1 gapmer DNA through disulfide linkage, and thereafter deliver them into cells.…”

Influence of Carbon Nanotubes and Its Derivatives on Tumor Cells In Vitro and Biochemical Parameters, Cellular Blood Composition In Vivo

“…Authors of [ 29 , 30 ] reported that specific nanotubes may be less harmful than nano-carriers for drugs. It has also been shown that simple functionalization (-OH, -COOH, -NH, PEG) [ 31 ] or encapsulation of the CNTs [ 22 ], increases the water solubility, improves bioavailability, and reduces toxicity of CNTs. And the introduction of CNTs to mice with a transplanted tumor may be effective against targeted transformed tissue and led to decreasing of tumor volume and to increasing animal survival [ 32 ].…”