Biossensores de colesterol baseados no sistema poli(álcool vinílico)/ftalocianina

Abstract

A new amperometric biosensor for the determining cholesterol based on the immobilization of cholesterol oxidase (ChOx) in a crosslinked poly(vinyl alcohol) (PVA) matrix and the charge transfer mediator copper phtahalocyanine (Ftc) is described. The biosensor was obtained by the complexation-mediated solubilization method, where Ftc was dispersed in high concentration in an organic aprotic solvent for the formation of the electron donor-acceptor complex. The crosslinked PVA membranes were characterized by differential scanning calorimetry (DSC), thermomechanical analysis (TMA), electronic spectroscopy (UV/Vis) and vibrational (FTIR) spectroscopy. The water transport through the biosensor membrane was studied by the equilibrium degree of swelling. The results of DSC and TMA indicate that both, the glass transition temperature (Tg) and Young modulus were increased systematically with crosslinking density of the hydrogel. The water diffusion coefficient decreased with the increase in the crosslinking degree indicating that the water molecules possess a lower degree of translational mobility and are "tightly bound" in the PVA-borate complex structure. Semiempirical calculations using PM3-d have been performed on the Ftc/PVA charge transfer complex. The geometry parameters, heats of formation, ionization potential, HOMO-LUMO energy differences are also reported and compared with the vibrational (FTIR) spectra and conductivity experimental results. The developed biosensor has been used for the determination of cholesterol with an acceptable accuracy. Under optimal conditions, the biosensor shows a linear response to cholesterol in the range of 0.1 mM to 5.17 mM, with a fast response (12 s) and high sensitivity.