Methylcellulose-Encapsulated Carbon Nanotubes as Biosensing Implants

Abstract

While single-walled carbon nanotubes (SWCNTs) have shown functionality in vivo for monitoring drugs and cancer biomarkers via their near-infrared fluorescence in the tissue transparent window, there is not yet a widely-used non-invasive method for implanting such devices. We developed an injectable methylcellulose (MC)-based polymer system, with demonstrated biocompatibility and in-situ gelling, for encapsulating SWCNTs. Oligonucleotide-wrapped SWCNTs were added to methacrylated MC polymer solutions, which were then crosslinked by free radical polymerization using redox initiators. Encapsulation in MC gels did not adversely impact SWCNT fluorescence for at least 149 days in vitro. The resulting nanocomposite gels were then exposed to varying concentrations of bovine serum albumin (BSA) as a model globular protein analyte, which caused SWCNT fluorescence to red-shift in a quantitative, concentration-dependent fashion from 0.1 to 150 µM. Separately, SWCNT response to the chemotherapeutic doxorubicin was also evaluated. This interaction quenched the fluorescence of MC-encapsulated SWCNTs with similar concentration dependence above 200 nM as has previously been found for in vivo implantable devices. We anticipate that this MC system will be a valuable tool for minimally-invasive delivery of SWCNT-based sensors for future in vivo experiments and potentially for use in the clinic.