Direct electrochemical sensor for label-free DNA detection based on zero current potentiometry

Biosensor for label-free DNA quantification based on functionalized LPGs

A label-free fiber optic biosensor based on a long period grating (LPG) and a basic optical interrogation scheme using off the shelf components is used for the detection of in-situ DNA hybridization. A new methodology is proposed for the determination of the spectral position of the LPG mode resonance. The experimental limit of detection obtained for the DNA was 62±2nM and the limit of quantification was 209±7nM. The sample specificity was experimentally demonstrated using DNA targets with different base mismatches relatively to the probe and was found that the system has a single base mismatch selectivity.

Gr-Pt hybrid NP modified GCPE as label and indicator free electrochemical genosensor platform

Glassy carbon paste electrode (GCPE) was modified with graphene platinum hybrid nanoparticle (Gr-Pt hybrid NP) and used as a transducer for label and indicator free electrochemical genosensor. 22 mer oligonucleotides representing Escherichia coli bacteria were used as a model case. As far as it is known, this study is the first study where Gr-Pt hybrid NP was incorporated into GCPE and used for genosensor transducer. The extent of hybridization was determined by using differential pulse voltammetric signals of guanin oxidation. After the optimization of experimental parameters, analytical characteristics were investigated. The linear range was found between 1.5×10(-7) and 2.25×10(-6) M with the equation of y=1.6566x-2.6161 and R(2) of 0.9959. RSD and LOD were calculated as 4.2% (n=6) and 1.12×10(-9) M respectively.

Carbon-Mercaptooctadecane/Carboxylated Multi-walled Carbon Nanotubes Composite Based Genosensor for Detection of Bacterial Meningitis

Human brain bacterial meningitis is a life-threatening disease mainly caused by Neisseria meningitidis, lead to several complications including damage of brain or even death. The present available methods for diagnosis of meningitis have one or more limitations. A rmpM gene based genosensor was fabricated by immobilizing 5'-amino modified 19-mer single stranded DNA probe onto carbon-mercaptooctadecane/carboxylated multi-walled carbon nanotubes composite electrode and hybridized with 2.5-40 ng/6 μL of single stranded genomic DNA (ssG-DNA) of N. meningitidis from cerebrospinal fluid (CSF) of the suspected meningitis patients. The electrochemical response was measured by using cyclic voltammetry and differential pulse voltammetry (DPV) using 1 mM methylene blue as redox indicator in 30 min (including a response time of 1 min) at 25 °C. The sensitivity of the genosensor was 3.762 (μA/cm(2))/ng and limit of detection was 2 ng of ssG-DNA of N. meningitidis with DPV. The genosensor has specificity only to N. meningitidis and does not hybridize with the genomic DNA of any other possible pathogen in human CSF. The immobilization of the probe and hybridization of the ssG-DNA were characterized by using electrochemical impedance in presence of 5 mM potassium ferricyanide and scanning electron microscopy. The genosensor loses only 12 % of its original DPV current on storage at 4 °C for 6 months. Carbon composite based electrochemical array can be constructed to detect multiple bacterial meningitis suspected patient CSF samples during an outbreak of the disease.