Separation-free electrochemical determination of liposomal daunorubicin encapsulation efficiency using mesoporous film on ternary carbon nanocomposite

Determination of the encapsulation efficiency (EE) of liposomal drugs generally requires prior physical separation of free drug from liposomes, which is time-consuming and can perturb drug partitioning. Herein, an electrochemical sensor was fabricated using vertically ordered mesoporous silica film (VMSF) grown on the adhesive, conductivity-enhancing interlayer of electrochemically reduced graphene oxide-multiwalled carbon nanotube-N-doped graphene quantum dot (ErGO-MWCNTs-NGQDs) ternary carbon nanocomposite. VMSF was grown by electrochemically assisted self-assembly on graphene oxide-MWCNTs-NGQDs (GO-MWCNTs-NGQDs) modified glassy carbon electrode (GCE), during which graphene oxide was simultaneously reduced in situ to ErGO. The preconcentration capability of VMSF, together with the highly electroactive interface provided by the ternary carbon nanocomposite, remarkably enhanced the electrochemical response of Daunorubicin. The peak current of DNR at VMSF/ErGO-MWCNTs-NGQDs electrode was 48-fold higher than that at bare glassy carbon electrode. The sensor exhibited two linear ranges for DNR detection, 0.001-1 μM and 1-20 μM, with a limit of detection (LOD) of 514 pM. The sensor also demonstrated good selectivity, reproducibility, and stability. After liposomalencapsulation of DNR, the proposed sensor enabled direct determination of free DNR in the liposomal formulation without prior physical separation of free and encapsulated DNR, thereby allowing the encapsulation efficiency to be calculated. The encapsulation-efficiency results obtained with the proposed sensor were in good agreement with those obtained using a commercially available UV-vis method. This separation-free electrochemical strategy provides promising method for DNR analysis and liposomal drug applications.