On-chip highly sensitive saliva glucose sensing using multilayer films composed of single-walled carbon nanotubes, gold nanoparticles, and glucose oxidase

It is very important for human health to rapidly and accurately detect glucose levels in biological environments, especially for diabetes mellitus. We proposed a simple, highly sensitive, accurate, convenient, low-cost, and disposable glucose biosensor on a single chip. A working (sensor) electrode, a counter electrode, and a reference electrode are integrated on a single chip through micro-fabrication. The working electrode is functionalized through a layer-by-layer (LBL) assembly of single-walled carbon nanotubes (SWNTs) and multilayer films composed of chitosan (CS), gold nanoparticles (GNp), and glucose oxidase (GOx) to obtain high sensitivity and accuracy. The glucose sensor has following features: (1) direct electron transfer between GOx and the electrode surface; (2) on-a-chip; (3) glucose detection down to 0.1 mg/dL (5.6 μM); (4) good sensing linearity over 0.017–0.81 mM; (5) high sensitivity (61.4 μA/mM-cm2) with a small reactive area (8 mm2); (6) fast response; (7) high reproducibility and repeatability; (8) reliable and accurate saliva glucose detection. Thus, this disposable biosensor will be an alternative for real time tracking of glucose levels from body fluids, e.g. saliva, in a noninvasive, pain-free, accurate, and continuous way. In addition to being used as a disposable glucose biosensor, it also provides a suitable platform for on-chip electrochemical sensing for other chemical agents and biomolecules.