Cyclodextrin-modified nanodiamond for the sensitive fluorometric determination of doxorubicin in urine based on its differential affinity towards β/γ-cyclodextrins.

The manuscript reports on the preparation of β-cyclodextrin-modified nanodiamonds (βCD-ND) for the extraction and preconcentration of the fluorescent anticancer drug doxorubicin (DOX) from biological samples. The inclusion of DOX into the cavities of β- and γ-cyclodextrin (CD) confirms their utility for selective extraction and elution of the drug based on its good fit to the cyclodextrin cavity. Although both larger cyclodextrins (βCD and γCD) accommodate DOX, DOX clearly prefers the bigger γCD cavities. Dispersive micro solid-phase extraction using βCD-ND as sorbent enables the inclusion complexation of DOX. The elution of DOX from βCD-ND cavities occurs with a basic solution of γCD containing 10% acetonitrile owing to the preferential affinity (i.e. optimal fit) of DOX into the larger γCD cavity. DOX is quantified by monitoring its intrinsic fluorescence (exc/em = 475/595 nm). The method can determine DOX in urine with a limit of detection of 18 ng·mL-1. Recoveries (93.2% and 94.0%) and precision (RSDs of 5.9% and 4.7%) at 100 and 400 ng·mL-1 DOX levels in urine are satisfactory. The matrix effect is negligible even when working with undiluted urine samples. Graphical abstract Nanodiamonds functionalized with β-cyclodextrin (βCD-ND) were used as sorbent for the determination of nanomolar levels of doxorubicin (DOX). It is based on host:guest interactions ruled by different stabilities of DOX within cyclodextrin (CD) cavity-size: βCD/γCD.