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 beta-cyclodextrin-modified nanodiamonds (beta CD-ND) for the extraction and preconcentration of the fluorescent anticancer drug doxorubicin (DOX) from biological samples. The inclusion of DOX into the cavities of beta- and gamma-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 (beta CD and gamma CD) accommodate DOX, DOX clearly prefers the bigger gamma CD cavities. Dispersive micro solid-phase extraction using beta CD-ND as sorbent enables the inclusion complexation of DOX. The elution of DOX from beta CD-ND cavities occurs with a basic solution of gamma CD containing 10% acetonitrile owing to the preferential affinity (i.e. optimal fit) of DOX into the larger gamma CD 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.