Abstract: Orthopedic implants for the treatment of bone defects from various causes have been challenged by insufficient osseointegration, bacterial infection, oxidative stress, immune rejection, and insufficient individualized treatment. These challenges not only impact treatment outcomes but also severely impact patients' daily lives. Layer-by-Layer (LbL) serves as a simple surface coating technique, in simple terms, to functionalize implants by sequentially adsorbing oppositely charged materials onto a substrate. In orthopaedics, LbL self-assembly technology solves some of the challenges by loading various drugs or biological agents on the implant surface and controlling their release precisely to the site of bone defects in a personalized way. This review will introduce the basic principle and the development of LbL in orthopaedics, review and analyze the chemical strategy of LbL in the preparation of bone implants to ensure the stability of the implant, and introduce the use of LbL bone implants in orthopaedics in recent years. The application of LbL includes the realization of programmed drug delivery and sustained release, thereby promoting osseointegration and the formation of new blood vessels, antibacterial, antioxidant, etc. This review focuses on the LbL technology, involving the technology selection for the preparation of bone implants, the chemical strategies of the stability guarantee of LbL implants, the pharmacological properties, loading and release mechanisms of loaded drugs, and the molecular mechanisms of osteogenesis and angiogenesis. The aim of this review is to provide an overview of current research advances, and a prospect in this field was also described.

Key words: Orthopedic implants, Layer-by-Layer self-assembly, Chemical strategy, Agents release, Orthopedic applications