Multifunctional photothermal PB@EGCG-Sr nanocoating design on titanium surface: To achieve short-term rapid osseointegration and on-demand photothermal long-term osteogenesis

To resolve the short-term inflammatory storm after the operation and the long-term osteointegration deficiency of titanium (Ti) implant as an artificial hip joint, in this work, a novel functionalized Ti implant with an "on-demand" treatment strategy was explored. The metallopolyphenol network (Epigallocatechin gallate (EGCG) and Strontium) wrapped Prussian blue nanoparticles were prepared and anchored on the Ti surface. During the acute inflammatory phase, the inflammatory acidic microenvironment will result in the degradation of the metallopolyphenol network and the responsive release of EGCG and strontium (Sr) ions. The released EGCG could reduce oxidative stress damage and promote the transition of macrophages from M1 to M2. In comparison, Sr ions could stimulate osteoblast differentiation and achieve the rapid osteogenesis and fixation of implants. To achieve long-term osteointegration efficacy, "on-demand" near-infrared light irradiation for the remained PB particles could be adopted if necessary. The mild photothermal conversion temperature could upregulate the expressions of heat shock proteins around the implant and promote the biosynthesis of type I collagen, as well as the formation of bone matrix. In vitro and in vivo results proved the feasibility of our strategy. It is a prospective method for the modification of Ti implants.