Electrochemical chiral sensor based on cellulose nanocrystals and multiwall carbon nanotubes for discrimination of tryptophan enantiomers

Based on the natural right-handed chirality of cellulose nanocrystals (CNCs) and conductive amplification of multiwall carbon nanotubes (MWCNTs), we designed a composite chiral sensor to discriminate the tryptophan (Trp) enantiomers with the advantages of rapid recognition, high sensitivity and stability. In comparison with previous reports, the developed composite sensor from s-CNC (CNC from H2SO4-hydrolysis)/MWCNT nanoparticles exhibited high enantiospecificity to l-Trp, with the promising sensitivity of 3.5-fold of the peak current ratio for l-Trp to d-Trp at the optimal conditions (pH 7.0, 25 °C). Two kinds of CNCs (s-CNCs from H2SO4-hydrolysis and h-CNCs from HCl-hydrolysis) bearing different surface properties (groups and charges) exhibited different effects on the affinity to Trp enantiomers and resultant chiral recognition influence. The synergetic effect of chiral recognition from cellulose nanocrystals and signal amplification from multiwall carbon nanotubes offered an easy-handling and effective electrochemical approach for isomers discrimination to realize the chiral recognition of Trp enantiomers.