Preparation, characterization, and antioxidative activity of Bletilla striata polysaccharide/chitosan microspheres for oligomeric proanthocyanidins

Novel oligomeric proanthocyanidins/Bletilla striata polysaccharide/chitosan (OPC/BSP/CTS) microspheres were obtained by spray-drying method. The morphology, size, physicochemical characterization, and in vitro release behavior of the formulation were evaluated. The results of scanning electron microscopy showed OPC-loaded microspheres with considerably wrinkled surfaces and drug-free microspheres with smooth surfaces. Particle-size analysis showed that the diameters of the OPC/BSP/CTS microspheres were 1–5 µm, with uniform distribution (polydispersity below 0.465). Fourier transform infrared indicated the occurrence of a chemical reaction between BSP and CTS. The OPC formed intermolecular hydrogen bonds with BSP/CTS carriers or transmuted amorphous structure. Differential scanning calorimetry displayed the absence of interaction; OPC was only physically encapsulated in the polymer matrix and OPC changed the crystallinity. All the microspheres showed desirable biodegradation rates; the high CTS content retarded their degradation and extended administration times. OPC/BSP/CTS microspheres showed pronounced antioxidant activity than pure OPC. These microspheres can be used as a potential platform to efficiently deliver unstable drugs as a sustained-release oral drug delivery system.