Tailoring MWCNTs and β-Cyclodextrin for Sensitive Detection of Acetaminophen and Estrogen.

Monitoring of trace amount of acetaminophen and estrogen in drinking water is of great importance because of their potential links to gastrointestinal diseases, and breast and prostate cancers. The sensitive and accurate detection of acetaminophen and estrogen requires the development of advanced sensing materials that possess appropriate number of analyte capturing sites and suitable signal conduction path. This can be achieved by implementing appropriate chemical attachment of multi-walled carbon nanotubes (MWCNTs) and β-cyclodextrin (βCD). Here, we report a systematic investigation of four types of modified MWCNT-βCD: (1) physical mixing, (2) "click reaction", (3) thionyl chloride esterification, and (4) Steglich esterification. The Steglich esterification is a one-step approach with shorter reaction-time, lower reaction-temperature, and eliminates handling of air/moisture-sensitive reagents. The MWCNT-βCD prepared by Steglich esterification possessed moderate βCD loading (5-10 wt%), large effective-surface-area, and fast electron transfer. The host-guest interaction of βCD and redox properties of MWCNT enabled sensitive detection of acetaminophen and 17β-estradiol (E2 is a primary female sex hormone) in the range of 0.005-20 µM and 0.01-15 µM, respectively, with low detection limits of 3.3 nM and 2.5 nM, respectively. We demonstrated accurate detection results of pharmaceutical compositions in water and urine samples. These results indicate that Steglich esterification method may be applied in fabricating pharmaceutical contaminants sensors for health and environmental applications.