Fast-dissolving core-shell composite microparticles of quercetin fabricated using a coaxial electrospray process

Abstract

This study reports on novel fast-dissolving core-shell composite microparticles of quercetin fabricated using coaxial electrospraying. A PVC-coated concentric spinneret was developed to conduct the electrospray process. A series of analyses were undertaken to characterize the resultant particles in terms of their morphology, the physical form of their components, and their functional performance. Scanning and transmission electron microscopies revealed that the microparticles had spherical morphologies with clear core-shell structure visible. Differential scanning calorimetry and X-ray diffraction verified that the quercetin active ingredient in the core and sucralose and sodium dodecyl sulfate (SDS) excipients in the shell existed in the amorphous state. This is believed to be a result of second-order interactions between the components; these could be observed by Fourier transform infrared spectroscopy. In vitro dissolution and permeation studies showed that the microparticles rapidly released the incorporated quercetin within one minute, and had permeation rates across the sublingual mucosa around 10 times faster than raw quercetin.

Figure 1. Images of the coaxial electrospraying process and the spinneret.

a) a diagram of the process; b) and c) the images of the concentric PVC-coated spinneret.

Figure 2. Photographs of the coaxial electrospraying processes.

a) the arrangement of the apparatus used in this work (inset: a photograph of the collector when an excessive core fluid flow rate was used); b) the connection of the spinneret with the power supply; c) a typical coaxial process under an applied voltage of 20 kV, with shell and core flow rates of 1.0 and 0.7 mL h⁻¹respectively; d) the compound Taylor cone.

Figure 3. FESEM images of the microparticles and their diameter distributions.

Figure 4. TEM images.

a) M1; b) M2; c) M3; and d) M5.

Figure 5. DSC thermograms of the starting materials (quercetin, sucralose, PVP and SDS) and microparticles (M2, M3 and M5).

Figure 6. XRD patterns and cross-polarised light observations.

a) XRD patterns of the starting materials and microparticles; and, microscopy images of b) quercetin; c) sucralose; d) SDS; e) PVP and f) M5 viewed under cross-polarised light.

Figure 7. ATR-FTIR spectra of the raw materials and microparticles, and the molecular structures of PVP, quercetin, sucralose and SDS.

Figure 8. In vitro dissolution tests.

a) in vitro quercetin release profiles (n = 6); b) Photographs of the dissolution of M5. The process is shown in sequence from 1 to 8, and finishes within 10s; c) a schematic depicting possible drug release mechanisms from the crystal quercetin and the microparticle composites.

Figure 9. In vitro permeation profiles of the quercetin powder and the microparticles (n = 6).