The typical trans olefinic band was observed at 965cm?1 [5]. PHBV infrared spectrum exhibited a strong band at Ku-0059436 1720cm?1 due to C=O stretching. Typical bands from 800 to 975cm?1 corresponded to symmetric�CC�CO�CC�Cstretching vibration. Moreover, the antisymmetric�CC�CO�CC�Cstretching leads to bands between 1060 and 1150cm?1 [35]. Considering PCL is also an aliphatic polyester, its spectrum is similar to that of PHBV with a strong band at 1727cm?1 corresponding to C=O stretching and two bands at 2943 and 2864cm?1 due to symmetric and asymmetric CH2-stretching, respectively [41].Figure 3FTIR spectra of resveratrol, PHBV/PCL, physical mixtures, and PHBV/PCL microparticles. Physical mixtures and microparticles presented band assignments at the same wavenumber range of FTIR spectrum.
Therefore, no difference in the positions of the absorption bands was observed between resveratrol-loaded microparticles and respective physical mixtures. Consequently, no chemical bond between drug and polymers was formed during microencapsulation.3.5. X-Ray Powder DiffractionFigure 4 shows the XRPD patterns of resveratrol, PHBV, PCL, physical mixtures, and PHBV/PCL microparticles. Pure resveratrol presented different peaks related to a crystalline structure, and its main peaks appear at 2�� = 6.62, 16.30, 19.17, 22.43, 23.55, and 28.37. Resveratrol-loaded microparticles revealed XRPD patterns similar to pure PHBV/PCL and unloaded-microparticles (M1R0/M2R0). These results suggest that the microencapsulation procedure provided a remarkable decrease of the crystalline diffraction peaks of resveratrol leading to drug amorphization [42].
Figure 4XRPD patterns of resveratrol, PHBV/PCL, physical mixtures, and PHBV/PCL microparticles. Substances in solid state can reveal crystalline and/or amorphous characteristics. In general, amorphous solids are more soluble than crystalline forms due to free energies involved in the dissolution process. Solids in amorphous state have randomly arranged molecules, and thus low energy is Entinostat required to separate them. Consequently their dissolution is faster than when in the crystal form [43]. 3.6. Thermal Analyses3.6.1. Thermogravimetric Analysis The TG curves of pure resveratrol, PHBV, PCL, physical mixtures, and PHBV/PCL microparticles are shown in Figures Figures55 and and6.6. Resveratrol presented two events of weight loss that can be observed through its derivative thermogravimetric curve (DTG). The first event ranged from 625 to 758K (��m = 41.7%), while the second one occurred between 758 and 1150K (��m = 57.5%). Both polymers showed only one event of weight loss, ranging from 564 to 591K (��m = 97.