Physical and chemical characterization of enolase immobilized polydiacetylene Langmuir–Blodgett film

Hexa histidine tagged recombinant Plasmodium falciparum enolase (His6-Pfen) was covalently immobilized on a Langmuir–Blodgett film of a self assembled mixture of 10,12-pentacosadiynoic acid and its N-succinimidyl ester derivative (PDA LB-film). The film was polymerized with a UV-lamp at 254 nm to obtain a blue coloured, protein hooked polydiacetylene film. Atomic force microscopy (AFM) was used to characterize the surface morphology of the protein-immobilized film. The colorimetric response (CR) of the His6-Pfen hooked PDA LB-film to 2-phosphoglyceric acid (2-PGA), the substrate of enolase, in the presence of magnesium ions was studied spectrophotometrically. The CR of glutathione S-transferase-Pfen (GST-Pfen) immobilized film prepared by using similar procedure was also examined. The results suggest that binding of Mg (II) to the enzyme facilitates the interaction of the enzyme with 2-phosphoglycerate. This ligand-binding event could be detected by an observed increase in colorimetric response of the film by ∼10%. Thus the incorporation of enolase on a PDA film resulted in the formation of a novel material, which can serve as a biosensor.