Highly sensitive, selective and label-free protein detection in physiological solutions using carbon nanotube transistors with nanobody receptors

• Published in: Sensors and actuators. B, Chemical Chemical, 2018-02, Vol.255, p.1507-1516
• Main Authors: Filipiak, Marcin S., Rother, Marcel, Andoy, Nesha M., Knudsen, Arne C., Grimm, Stefan, Bachran, Christopher, Swee, Lee Kim, Zaumseil, Jana, Tarasov, Alexey
• Format: Article
• Language: English
• Subjects: Biosensors; Debye screening; Electrolytes; Field effect transistors; Field-effect transistor (FET); Fluorescence; Immunoassay; Label-free immunosensing; Nanobodies (VHH); Nanomaterials; Nanotubes; Physiological effects; Polyethylene glycol; Polyethylene glycol (PEG); Pretreatment; Proteins; Receptors; Screening; Semiconductor devices; Single wall carbon nanotubes; Single-walled carbon nanotube (SWCNT) networks; Transistors
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2017.08.164

[Display omitted] •Sorted carbon nanotube networks yield high quality transducers by solution processing.•Novel nanobody receptors enable analyte binding close to the surface.•The signals can be strongly enhanced if the surface is PEGylated.•Label-free, rapid and selective protein detection is demonstrated in physiological solutions.•Dynamic range exceeds 5 orders of magnitude with a sub-picomolar detection limit. Nanomaterial-based field-effect transistors (FETs) have been proposed for real-time, label-free detection of various biological species. However, two major challenges have limited their use in physiological samples: screening of the analyte charge by electrolyte ions (Debye screening) and non-specific adsorption. Here, these challenges are overcome by combining highly stable FETs based on single-walled semiconducting carbon nanotube (SWCNTs) networks with a novel surface functionalization comprising: 1) short nanobody (VHH) receptors, and 2) a polyethylene glycol (PEG) layer. Nanobodies are stable, easy-to-produce biological receptors that are very small (∼2–4nm), thus enabling analyte binding closer to the sensor surface. Despite their unique properties, nanobodies have not been used yet as receptors in FET based biosensors. The addition of PEG strongly enhances the signal in high ionic strength environment. Using green fluorescent protein (GFP) as a model antigen, high selectivity and sub-picomolar detection limit with a dynamic range exceeding 5 orders of magnitude is demonstrated in physiological solutions. In addition, long-term stability measurements reveal a low drift of SWCNTs of 0.05mV/h. The presented immunoassay is fast, label-free, does not require any sample pretreatment or washing steps.