Cellulosic biosensor chips for monitoring adsorptive interaction of rubisco protein with cellulose using SPR

Cellulosic films were prepared by spin-coating a nano-layer of cellulose from an organic solvent onto gold substrates. The cellulose-coated substrates were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and surface plasmon resonance (SPR). Rubisco protein adsorptive interaction with the spin-coated cellulosic surfaces was monitored using SPR. The results have demonstrated that rubisco uptake by the spin-coated cellulosic films is minimal relative to other non-cellulosic films. The results have also revealed that rubisco uptake by the spin-coated cellulosic films is inconsistent, most likely due to the interference of the SPR reflectivity signal (i.e. measurement accuracy) by the swelling of the thick (~30 nm on dry basis) films. This inconsistency problem was resolved by preparing ultrathin films (~2.5 nm) of cellulose via the self-assembly of cellulose onto the SPR biosensor chips. The self-assembly was achieved by attaching disulphide functional group to the cellulose molecules through the chemical coupling with α-lipoic acid.