Nanosized Polyaniline (PANI) as the immobilisation template for protein molecules / Nor Hazirah Kamel Abdul Azem

Nanosized polyaniline (PANI) was used as template to enhance the sensitivity of Surface Plasmon Resonance (SPR) signal. Nanosized PANI was synthesised using microemulsion polymerisation using hydrochloric acid as dopant and ammonium peroxydisulphate as the oxidising agent. PANI particles with sizes between (1-15) nm as measured using a nanosizer were successfully synthesised. The PANI obtained is of the emeraldine type due to the presence of both quinoid and benzene ring as identified in it’s FTIR spectrum, and; further proven from the value of it’s electrical conductivity which is 2.99 X 10'9 S cm'1 which is closed to other researcher. Thermal analysis revealed the possibility of PANI-HC1 complex being formed which contributed to the positively charged nature of the PANI particles. The PANI existed as single particles with sharp edges and are irregularly-shaped under TEM observation. Bovine Serum Albumin (BSA), which was chosen to be the model protein molecule was introduced to the PANI nanoparticles; and the nanoparticles capability to immobilised BSA was determined using SPR Spectroscopy. Several concentration of BSA were used for immobilisation onto various amount of PANI. Highest SPR signal (in RU unit) was obtained when 10.00 mg/ml of BSA was immobilised onto 1.00% PANI nanoparticles. The main driving force for adsorption of BSA onto PANI is electrostatic interaction between the positively charged amine (-NH+) in PANI and negatively charged BSA molecules. The interaction of antiBSA (AB) with PANI-bounded BSA generated a maximum RU signal of 1736; which is 7 times higher than the interaction of AB with free (unbound) BSA of the same concentration. It shows that the activity of BSA was not affected by the immobilisation process onto PANI nanoparticles. This proved that PANI nanoparticles could serve as a template for the immobilisation of BSA with enhancement of the SPR signal, hence increasing the SPR sensitivity.