Preparation of Pinocembrin-Loaded F127/MPEG-PDLLA Polymer Micelles and Anti-Osteoporotic Activity

Pinocembrin (PCB) is 5,7-dihydroxyl flavanone and has multiple pharmacological activities, namely, anti-inflammation, anti-osteoporotic, and so on. However, low water solubility and bioavailability have hindered its application. Herein, we aimed to increase its bioavailability through preparation of F127/MPEG-PDLLA polymer micelles (PCB-M). We characterized the micelles through appropriate attributes such as analysis of particle size (PS), polydispersity (PDI), transmission electron microscopic (TEM) image, stability test, and evaluation of in vitro release of drug. After physical characterization, the respective PS, PDI, and entrapment efficiency (EE) of PCB-M were estimated to be 27.63 ± 0.17 nm, 0.055 ± 0.02, and 90.53 ± 0.01%. Fluorescence probe method was employed to measure critical micelle concentration (CMC) of PCB-M, we observed CMC was low, thereby suggesting that PCB-M had good stability. In vitro release analysis indicated that the rate of cumulative PCB release from PCB-M was greater than 90% in each medium compared with free PCB, which was less than 40%, thus pointing to a significantly improved solubility of PCB. In vivo pharmacokinetic results showed that oral biological availability of PCB-M increased 5.3 folds comparable to free PCB. The effects of PCB on osteoblasts and ALP activities were investigated; subsequently, zebrafish osteoporotic model was established with prednisolone to study the anti-osteoporotic effects of PCB and PCB-M. The results showed that PCB improved osteoporosis with PCB-M being more effective than free PCB. Finally, PCB-M can be used as a promising method to improve the solubility of PCB, while the bioavailability and anti-osteoporotic effect of PCB could be improved, thus laying a foundation for clinical use in the future. Graphical Abstract