DNA-wrapped multi-walled carbon nanotube modified electrochemical biosensor for the detection of Escherichia coli from real samples.

This paper introduces DNA-wrapped multi-walled carbon nanotube (MWCNT)-modified genosensor for the detection of Escherichia coli (E. coli) from polymerase chain reaction (PCR)-amplified real samples while Staphylococcus aureus (S. aureus) was used to investigate the selectivity of the biosensor. The capture probe specifically recognizing E. coli DNA and it was firstly interacted with MWCNTs for wrapping of single-stranded DNA (ssDNA) onto the nanomaterial. DNA-wrapped MWCNTs were then immobilised on the surface of disposable pencil graphite electrode (PGE) for the detection of DNA hybridization. Electrochemical behaviors of the modified PGEs were investigated using Raman spectroscopy and differential pulse voltammetry (DPV). The sequence selective DNA hybridization was determined and evaluated by changes in the intrinsic guanine oxidation signal at about 1.0V by DPV. Numerous factors affecting the hybridization were optimized such as target concentration, hybridization time, etc. The designed DNA sensor can well detect E. coli DNA in 20min detection time with 0.5pmole of detection limit in 30µL of sample volume.

Cystic Fibrosis Mutation Detection with SPR Biosensor in Real Samples via Multiple Surfaces Binding Method.

AIM AND OBJECTIVE: Surface Plasmon Resonance (SPR) based biosensor system was developed for the detection of Delta F508 (ΔF508del) Cystic Fibrosis (CF) mutation in both synthetic and real samples. MATERIAL AND METHOD: In order to provide an effective hybridization between probe and the Polymerase Chain Reaction (PCR) amplicons (target), streptavidin was bound to the surface and biotin-tag probe was sent to the streptavidin-coated surface. For the target preparation, blood samples were collected from the patients who suffer from CF. Following the DNA isolation; samples were amplified with PCR with biotin-tag. Before sending the biotin-tag PCR amplicons onto the modified surface, amplicons were also interacted with the helper oligonucleotides to prevent re-annealing of the denatured DNA strands. This kind of 'multiple surface binding' method helps increasing the sensitivity of the detection. RESULTS: The limit of detection (S/N= 3) was calculated as 12.24 pico-mole/ml for PCR-like synthetic long target sequence and 13x105 molecules for real samples in less than half an hour. CONCLUSION: Using the both biotin-tag probe and the helper oligonucleotides together, hybridization was achieved much more efficiently than traditional denaturation protocols for real samples and biotinfree hybridization detection. To the best of our knowledge, the procedure described in this study is one of the simplest, rapid and sensitive methods for CF mutation detection with SPR based biosensor system in real samples.