▎ 摘　　要

Cotinine, a metabolite of nicotine, has shown promise as a biomarker for the detection of tobacco use and smoke exposure due its ability to persist in human bodily fluids for days (ca. 4-5 days) after tobacco consumption. However, current cotinine detection strategies primarily include arduous laboratory sensing methods or qualitative in-field biosensing devices. Herein, we report an electrochemical cotinine sensor based on a selective molecularly-imprinted polymer (MIP) electrodeposited on a screen-printed carbon electrode (SPCE) modified with graphene flakes and platinum nanoparticles (PtNPs). The PtNP-graphene modified SPCE exhibited a 4-fold increase in electrochemical sensitivity (10 mu A-40 mu A) during ferricyanide cyclic voltammetry. This developed biosensor functionalized with the MIP was consequently capable of selective sensing of cotinine in spiked saliva samples across a wide sensing range (1-100 nM) and low detection limit of (0.33 nM). This sensing range covers cotinine concentration levels that are typically found in saliva for non-smokers and smokers (ca. 10-75 nM). Moreover, the sensing is capable of acquiring a cotinine measurement within 12 min with minimal interference from both nicotine and myosmine-cotinine chemical analogs that are typically found in tobacco products. Hence, the developed biosensor is well-suited for use in the field such as at point-of-care facilities.