Implantation of nano-MOFs into chitosan/sodium alginate hydrogels: boosting the electroanalytical response of chlorogenic acid in food samples

Anchoring metal-organic frameworks (MOFs) into flexible carriers to improve the mass-transfer and dispersion properties holds enormous promise in the field of food safety monitoring. Herein, a classical nano-MOF, amino-modified zirconium 1,4-dicarboxybenzene (UiO-66-NH2), was assembled via the solvothermal approach. UiO-66-NH2 was then implanted into chitosan/sodium alginate hydrogels (CS/SA) to form MOF-based composite hydrogels (CS/UiO-66-NH2/SA-x, x indicates the mass ratio of CS/SA, which was set to 1, 2 and 3). Next, an electroanalytical sensing platform (CS/UiO-66-NH2/SA-2/GCE) was effectively constructed with the CS/UiO-66-NH2/SA-2-modified glassy carbon electrode (GCE). CS/UiO-66-NH2/SA-2/GCE achieved an excellent linear detection range (0.1-1000 μmol L-1) and sensitive detection limit (0.03 μmol L-1) for the target analyte chlorogenic acid (CGA), a vital biomolecule in food, under optimal buffer solution conditions. At the same time, the electrochemical sensor presented good anti-interference capability in the presence of a range of ions and biomolecule interferences. During the evaluation of real samples (apple and coffee), the CS/UiO-66-NH2/SA-2-based electrochemical sensing platform achieved recovery rates of 99.2-103.4%. In short, combining MOF materials with flexible hydrogels offers novel perspectives for the assessment of markers in food.