Encapsulation of green tea polyphenol by pH responsive, antibacterial, alginate microgels used for minimally invasive treatment of bone infection.

The treatment of bone infection requires drug carriers take large number of cargo, be antibacterial, promote proliferation and differentiation of osteoblasts. Herein, we proposed a strategy of preparing pH responsive, antibacterial, multistage structured microspheres encapsulated with green tea polyphenol used for minimally invasive treatment of bone infection. Tea polyphenol (TP) were encapsulated by porous silica nanospheres (SiO2 NSs). Then, sodium alginate (SA) microgel spheres (MSs) were prepared to encapsulate a lot of TP loaded SiO2 NSs. The outer layer of obtained TP@SiO2@SA microgel spheres were further wrapped by pH sensitive CaCO3. Mineral out-layer of the composite microspheres is used to neutralize the acidic environment caused by bacterial infection. At the same time, encapsulated TP is released pH sensitively to resist oxidative stress. Our results exhibited excellent drug delivery properties including drug loading efficiency (DLE) of 92.96% and drug loading content (DLC) of 19.62%. Besides, results demonstrated that TP@SiO2@SA@CaCO3 MSs can effectively kill Staphylococcus aureus and promote proliferation and differentiation of osteoblasts under stimulation of H2O2 at pH = 5.5.