Layer By Layer Assembly Of Carbon Nanotubes Modified Biosensor And Its Application

The LBL assembly offering an easy and inexpensive process for multilayer formation has attracted much attention in recent years. Various charged materials, such as nanotubes, organic dyes, and proteins could be used as components to prepare mutilayer films with high order at nanoscale via LBL assembly. Furthermore, the LBL method is conducted in aqueous solutions, under mild conditions, which retains the activity of biomolecules.Recently, carbon nanotubes (CNTs) have been conducted in LBL assembly due to their specific characteristics including high surface-to-volume ratio, high chemical stability and good electric conductivity. In order to subject CNTs to the electrostatic LBL assembly, charged sites have to be attached to the carbon nanotube structures. Wrapping CNTs with polyelectrolyte is an effective method. For example, MWNTs could interact with PAH and the resulting PAH-MWNTs are well-dispersed and positively charged.A type of reagentless biosensor based on electrostatic LBL assembly of functional MWNTs and enzyme-mediator biocomposite was proposed. A (PAH-MWNTs/HRP-MB)n multilayer film was then prepared based on electrostatic LBL assembly of positively-charged PAH-MWNTs and negatively-charged HRP-MB on a gold electrode. Due to the excellent biocompatibility of HRP-MB biocomposite and the uniform LBL assembly, the immobilized HRP could retain its natural bioactivity and MB could efficiently shuttle electrons between HRP and the electrode. The incorporation of MWNTs in the bionanomultilayer enhanced the surface coverage concentration of the electroactive enzyme and increased the catalytic current response of the electrode. The prepared biosensor exhibited an electrocatalytic activity to the reduction of hydrogen peroxide with a fast response, a low detection limit and an effective anti-interference capability.A bienzyme multilayer electrode was constructed based on MWNTs and horseradish peroxidase (HRP)/glucose (GOD) via layer-by-layer (LBL) assembly for amperometric determination of phenolic compounds. Atomic force microscopy (AFM) was applied to monitor the assembly of functionalized MWNTs and HRP or GOD. The bilayer number of MWNTs/enzyme were optimized. With catechol as substrate, electrochemical study showed that the introduce of MWNTs could obviously improve the sensitivity of the bienzyme electrode. The biosensor possessed high sensitivity and fast response for phenolic compounds.A (PAH-MWNTs/TYR)n multilayer electrode was constructed based on PAH-MWNTs and tyrosinase (TYR) via LBL assembly for determination of phenolic compounds. A (PAH-MWNTs/HRP)n multilayer electrode was constructed based on PAH-MWNTs and HRP via LBL assembly. The prepared (PAH-MWNTs/HRP)n biosensor could be applied to detect phenolic compounds in serum. The recovery of quercetin were in the range of 69.3-72.2%, the recovery of rutin were in the range of 95.6-96.3%.