Formation of electrosprayed PVP-GTE submicron particles: physicochemical characteristics and antioxidant activities

Abstract This research is focused on the optimation of green tea extract-loaded polyvinylpyrrolidone (PVP) submicron particles by electrospraying for enhanced delivery of antioxidants. The novelty lies in the explanation of the critical connection between process parameters, drug loading, and biological activity. A precursor solution of GTE and PVP in ethanol (13 wt.%) was electrosprayed at a fixed voltage (15 kV) and distance (15 cm), and the flow rate varied (1, 3, and 5 µL/min) as an important parameter. Spherical morphologies were examined using scanning electron microscopy (SEM), with the average diameter of particles increasing from 391 nm to 713 nm with increasing flow rate. FTIR spectroscopy employing Fourier transform infrared verified effective encapsulation of the GTE in the PVP matrix via hydrogen bonding. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis indicated that the encapsulated GTE existed in an amorphous form, a desired state for enhanced bioavailability. More importantly, diphenylpicrylhydrazyl (DPPH) assay demonstrated pronounced antioxidant activity in the composite particles to be significantly enhanced relative to free GTE (IC₅₀ values of ~ 22 µg/mL vs. 47 µg/mL). Compared to typical emphasis on nano-size for rapid release, bigger particles (separated at higher flow rates) contained superior antioxidant activity with higher GTE loading content (~ 47%), overshadowing kinetic advantage of smaller particles. The above findings emphasize that optimization of encapsulation efficiency can be more crucial than mere size decrease. Thus, electrosprayed PVP-GTE particles reveal a highly promising platform for creating efficient natural antioxidant delivery systems.