These values are mainly based on the poor aqueous solubility (13.6��g?g?1 selleckchem in pH = 7.4) of resveratrol [34] which leads to an increase in the drug loaded into microparticles. Similar results were previously reported. A resveratrol entrapment higher than 97.7% was achieved for calcium-pectinate beads prepared by instantaneous gelation of pectin [11]. Resveratrol-loaded nanoparticles showed EE from 78.3 to 91.4% using PCL of Mw? = 65,000g?mol?1 [16]. Vanillin cross-linked chitosan microparticles containing resveratrol revealed a drug entrapment higher than 93.7% [22]. The polymer:drug ratio is also a critical factor during microparticle formation and can influence EE values [35]. The enhancement of resveratrol entrapment was observed when the polyester amount was increased (Table 3).

For PHBV microparticles, EE was increased from 80 to 93% as polymer:drug ratio was improved from 4:1 (20% resveratrol) to 19:1 (5% resveratrol). Resveratrol entrapment varied from 88 to 101% for PCL microparticles when polymer:drug ratio was changed at the same proportion. This effect can be simply due to the greater polymer with respect to the drug amount.3.2. Scanning Electron MicroscopyThe scanning electron micrographs of PHBV/PCL microparticles are shown in Figure 2. Different morphological aspects were observed depending on the polyester used. By SEM, PHBV microparticles were spherical shaped with a rough surface and pores (Figures 2(a)�C2(d)). The presence of pores represents important morphological evidence that can change the drug release process from microparticles [36].

However, PCL microparticles revealed a spherical shape with smooth surface (Figures 2(e)�C2(h)), and no pore were observed. Moreover, formulation M2R20 showed a residual resveratrol onto the microparticles surface. This external drug can be rapidly dissolved into an aqueous medium and provide an immediate-release behavior (burst effect) [23]. This effect has been also observed in other studies related to delayed-release biopolymer systems [37, 38].Figure 2Scanning electron micrographs of PHBV/PCL microparticles: M1R0 (a), M1R5 (b), M1R10 (c), M1R20 (d), M2R0 (e), M2R5 (f), M2R10 (g), and M2R20 (h). Magnifications of 2000x.3.3. Particle Size and Size DispersionThe particle size and size distribution obtained by LDS measurements are indicated in Table 3.

Micrometer-sized particles with mean diameters less than 60��m were obtained. Although these particle sizes do not allow an uptake by intestinal tissue, the oral administration of these microparticles can provide sustained drug effect due to their prolonged bowel transit GSK-3 time [39]. Regarding that a low span value indicates a narrow polydispersity [40], PCL microparticles presented a more homogeneous size distribution when compared to PHBV microparticles.3.4.