Luminescent calcium orthophosphate (CaPO4) bioceramics: preparation, properties and biomedical applications

Due to the chemical similarities with calcified tissues of mammals, calcium orthophosphate (abbreviated as CaPO4) bioceramics have a broad range of promising biomedical applications. To further extend their use, CaPO4 bioceramics are modified with various additives and dopants. Since luminescence is an effective minimally invasive tool for in situ studies of tissue engineering, drug delivery and restoration phenomena, a utilization of CaPO4 bioceramics doped with luminescent compounds seems to be very promising. This approach has been developed as the result of the studies of natural CaPO4, which were found to possess luminescent properties mainly due to the presence of rare-earth (RE) dopants. In comparison to other luminescent substances, the use of luminescent CaPO4 bioceramics is an exceptional area of biomedical applications due to its biodegradability, bioactivity, biocompatibility, osteoconductivity, non-toxicity and non-inflammatory nature. Such biomaterials possess intrinsic features that can be adjusted through various ways, such as changing the available dopants and their amounts, synthesizing temperature, reaction time and production techniques. Therefore, luminescent CaPO4 bioceramics are used in a variety of biomedical applications, including imaging probes, drug delivery, bone tissue engineering and antibacterial studies. This review analyses the synthetic methods, luminous properties and biomedical applications of luminescent CaPO4 bioceramics. Future directions are also outlined.