Encapsulation of quantum dots and carbon nanotubes with polypyrrole in a syringe needle for automated molecularly imprinted solid phase pre-concentration of ochratoxin A in red wine analysis

Abstract

Nanometer-sized semiconductor quantum dots (QDs with CdSe core and ZnS shell) and carbon nanotubes (CNTs with multi-walls) were encapsulated inside a stainless steel syringe needle by electrodeposition of polypyrrole (PPy). By cross-linking the PPy with ethylene glycol dimethacrylate (EGDMA) in the presence of ochratoxin A (OTA) as a template, molecularly imprinted polypyrrole (MIPPy) was formed on the nano-hybrid structure at an increased specific surface area. The MIPPy/ CNTs/QDs-modified needle was readily adapted in an autosampler for micro-solid phase preconcentration (lSPP) of OTA from a red wine sample. After pulsed elution (PE) with 2% triethylamine (TEA), the OTA was determined by high performance liquid chromatography (HPLC) with fluorescence detection (FD). In comparison with MIPPy/ CNTs, this new nano-hybrid structure of MIPPy/CNTs/ QDs significantly improved the % recovery of OTA. The method, MIPPy/CNTs/QDs-lSPP-HPLC-FD, demonstrated that the MIPPy was truly a molecularly imprinted polymer (MIP) with specific recognition for OTA. All red wine matrix components could be differentially washed out, prior to accurate determination of the strongly bound OTA.

Molecularly Imprinted Polymer Nanomaterials for Mycotoxin Extraction

“…A 22-gauge needle can be modified to introduce a small sample on the microfluidic chip for capillary electrophoresis analysis (63). Currently, our group is exploring a new possibility in using quantum dots and carbon nanotubes to build three-dimensional structures inside a stainless steel needle (64 ). New results are verifying that those nano-scale structures can further increase the total surface area of MIPPy film, thus dramatically enhancing the extraction efficiency (or %recovery).…”

Imprinted Polymers

“…This problem can be mitigated by the use of nanostructured materials for molecular imprinting, to enhance the surface area for the same amount of polymer. Recently, Wei and coworkers [67], have proved this concept by using both carbon nanotubes (CNTs) and semiconductor quantum dots (encapsulated into a PPy film) to increase the surface area of their microsolid-phase preconcentration device for ochratoxin A (OTA) in red wine. Since the discovery of CNTs in 1991, they represent a new kind of carbon material that has been widely recognized as the quintessential nanomaterial [68].…”

“…Integration of CNT and CPs in the form of composites presents new opportunities to produce superior materials for various applications. Yu and coworkers [67,[70][71][72] prepared MIPs by electropolymerization of pyrrole (MIPPy) onto a stainless steel frit using OTA as the template and CNTs as nanostructured fibers to make a microsolid-phase preconcentration device, where the limit of detection for OTA was 12 ng ml −1 (ppt). The use of MIPPy/CNT-modified stainless steel frits in the rapid extraction of small amounts of OTA was compared with traditional microsolid-phase extraction cartridges and MIPPy-modified stainless steel frits [73] (prepared without CNTs), where the limit of detection was only 0.05 mg ml −1 (ppb).…”

Carbon nanotube array: A new MIP platform

“…However, this normally leads to a significant reduction of binding capacity within the same device area, thereby reducing the sensitivity when it is integrated into a transducer for direct sensing. This problem has been addressed by scientists using large surface area nano-materials for molecular imprinting (Shi et al, 1999;Chronakis et al, 2006;Li et al, 2006) and the most recent developments in this area were done by Wei et al (2007) and Xie et al (2007). In the work of Wei et al, both carbon nanotubes and semiconductor quantum dots were encapsulated into a thick polypyrrole film, aiming to increase the surface area of their micro-solid phase preconcentration (SPP) device.…”

“…In the work of Wei et al, both carbon nanotubes and semiconductor quantum dots were encapsulated into a thick polypyrrole film, aiming to increase the surface area of their micro-solid phase preconcentration (SPP) device. However, this nano-hybrid structure has increased the surface area of the device by increasing the surface roughness but not the porosity of the polymer matrix, and thus this is not truly surface imprinting (Wei et al, 2007). In contrast, Xie et al imprinted 2,4, molecules on the walls of highly uniform silica nanotubes.…”