Analysis of the heterogeneous structure of iron oxide/gold nanoparticles and their application in a nanosensor

- A heterogenous nanoparticles, IONPs-AuNPs using electrostatic- self- assembly technique is proposed.
- This technique manipulates the positive (IONPs) and negative (AuNPs) surface charge.
- Modification of carboxylate-IONPs-AuNPs for glucose oxidase immobilisation.
- Application of immobilised glucose oxidase on IONPs-AuNPs for glucose detection.

Magnetic iron oxide-gold nanoparticles (IONPs-AuNPs) could provide a useful platform for biosensing purposes. The aim of this study was to investigate the formation of such particles using a simple electrostatic self-assembly technique, and then to demonstrate their application using a glucose detection assay. AuNPs were attached to the IONPs surface by ionic interaction, as verified using UV-vis spectrophotometry. Then, a carbodiimide-coupling technique was used to covalently attach glucose oxidase (GOx) onto the nanoparticles' surface and the bioactivity was measured using an ABTS colorimetric assay. For characterization, UV-vis spectrophotometer, DLS, zeta potential, TEM, EDX, XPS and FTIR techniques were used. The particle diameter obtained from TEM was 16.1 ± 11.1 nm and EDX confirmed the presence of Au and Fe elements. In addition, FTIR results exhibited strong vibrational modes around 1654, 1546 and 3369 cm−1 that appeared to be primarily due to immobilization of GOx onto Fe/Au. The colorimetric assay also showed a significant increase in green color intensity, due to oxidation of ABTS, with increasing glucose concentrations ranging from 20 μM to 100 μM. IONPs/Au nanoparticles showed a good potential for application in this colorimetric assay, thus suggesting an excellent basis for a nanosensor system using these particles.