Immobilization of acetylcholinesterase on electrospun poly(acrylic acid)/multi-walled carbon nanotube nanofibrous membranes

In this work, poly(acrylic acid) (PAA) and PAA/multi-walled carbon nanotube (MWNTs) nanofibrous membranes are fabricated by electrospinning to immobilize acetylcholinesterase (AChE). 3-Aminopropyltriethoxysilane (APTES) and glutaraldehyde are used for surface modification and PAA membrane stabilization in aqueous media. The structure of the nanofibrous membrane was studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, thermogravimetric and mechanical analyses. The AChE enzyme was immobilized on the PAA nanofibers with different amounts of MWNTs concentrations from 0 to 5 wt%. The SEM images revealed that the average diameter of the PAA nanofibers was 226 ± 25 nm which was increased by increasing the MWNTs concentration. The tensile strength and modulus of the nanofibrous membranes increased by 1.87 and 4.39 fold respectively after a crosslinking process. The results show that membranes containing MWNTs are a more appropriate support for enzyme immobilization. In comparison to pure PAA, the activity of the sample containing 4 wt% of MWNTs was increased by 5.07 fold. Also, the immobilized enzyme showed excellent reusability even after 10 cycles of washing and samples maintained more than 90% of their original activities. Moreover, the pH and thermal stability of the immobilized enzyme was improved compared to the free enzyme. The results show that a PAA/MWNTs nanofibrous membrane could be counted as a suitable support for AChE immobilization in addition to different applications such as biosensor manufacturing. The immobilized enzyme on nanofibrous samples maintained more than 90% of its original activity even after 10 cycles of reusing.