Aisha Javed

Nano-composition of riboflavin-nafion functional film and its application in biosensing

A novel nafion-riboflavin membrane was constructed and characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy and cyclic voltammetric techniques. The estimated average diameter of the designed nanoparticles was about 60 nm. The functional membrane showed a quasi-reversible electrochemical behaviour with a formal potential of −562 ± 5 mV (vs Ag/AgCl) on the gold electrode. Some electrochemical parameters were estimated, indicating that the system has good and stable electron transfer properties. Moreover, horseradish peroxidase (HRP) was immobilized on the riboflavin-nafion functional membrane. The electrochemical behaviour of HRP was quasi-reversible with a formal potential of 80 ± 5 mV (vs Ag/AgCl). The HRP in the film exhibited good catalytic activity towards the reduction of H2O2. It shows a linear dependence of its cathodic peak current on the concentration of H2O2, ranging from 10 to 300 µM.

A new method for the determination of haemoglobin concentration using a bromide-modified silver electrode.

A bromide‐mediated silver electrode was applied to the measurement of haemoglobin. Bromide ions showed very good redox behaviour with the silver electrode. The cathodic and anodic peak potentials were related to the concentration of bromide ions involved in making the bromide‐modified silver electrode. The electrode reaction in the bromine solution was a diffusion‐controlled process. In the presence of pure haemoglobin, the modified electrode showed positive shift in cathodic and anodic peaks: −170 to −140 mV for cathodic peak and +30 to +65 mV for anodic peak with a new pair of cathodic and anodic peaks appearing at −58 and 218 mV, which were related to haemoglobin. Redox peak currents increased linearly as haemoglobin concentrations increased from 5 to 70 μM. The correlation coefficient and detection limit were 0.997 and 2 μM respectively. For a real test sample, the correlation coefficient and detection limit of the experiment were 0.993 and 4 μM respectively. The relative S.D. of results was 2.8% for five successive determinations of 20 μM haemoglobin. The modified silver electrode showed very good repeatability and stability for the determination of haemoglobin.