CoFe2O4-APTES nanocomposite for the selective determination of tacrolimus in dosage forms: Perspectives from computational studies

An innovative and cost effective electrochemical sensor was fabricated to determine tacrolimus (TAC) in pharmaceutical samples. In the present study, cobalt ferrite nanoparticles (CFO) were synthesized hydrothermally using chitosan as the template and were further functionalized using (3-Aminopropyl)triethoxysilane (APTES). The synthesized CFO were characterized using various analytical techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometry and high- resolution transmission electron microscopy. The CFO and CFO-APTES were further drop-casted on to the glassy carbon electrode (CFO-NH 2 /GCE) for the electrochemical determination of TAC. Under the optimum conditions, the CFO-NH 2 /GCE showed a very low detection limit of 0.03 nM with a high sensitivity of 21,448 μAμM −1 cm −2 and a wide linear TAC concentration range of 0.14 nM – 75.83 nM. The proposed sensor showed good sensitivity, selectivity, reproducibility and stability for the sensing of TAC and this has been demonstrated by analysing TAC in different dosage forms. This is the first study to report the interaction of CFO-TAC and CFO-NH 2 -TAC at the electrode/electrolyte interface. To support the experimental findings qualitatively, extensive density functional theory simulations were carried out to study the interaction at the interface. Hence the proposed sensor is very selective and sensitive towards the detection of TAC.