Luminescent Hydroxyapatite Doped with Rare Earth Elements for Biomedical Applications

Abstract

One new, promising approach in the medical field is represented by hydroxyapatite doped with luminescent materials for biomedical luminescence imaging. The use of hydroxyapatite-based luminescent materials is an interesting area of research because of the attractive characteristics of such materials, which include biodegradability, bioactivity, biocompatibility, osteoconductivity, non-toxicity, and their non-inflammatory nature, as well their accessibility for surface adaptation. It is well known that hydroxyapatite, the predominant inorganic component of bones, serves a substantial role in tissue engineering, drug and gene delivery, and many other biomedical areas. Hydroxyapatite, to the detriment of other host matrices, has attracted substantial attention for its ability to bind to luminescent materials with high efficiency. Its capacity to integrate a large assortment of substitutions for Ca2+, PO43−, and/or OH− ions is attributed to the versatility of its apatite structure. This paper summarizes the most recently developed fluorescent materials based on hydroxyapatite, which use rare earth elements (REEs) as dopants, such as terbium (Tb3+), erbium (Er3+), europium (Eu3+), lanthanum (La3+), or dysprosium (Dy3+), that have been developed in the biomedical field.

Crystallization, Luminescence and Cytocompatibility of Hexagonal Calcium Doped Terbium Phosphate Hydrate Nanoparticles

“…Luminescent nanoparticles are excellent optical probes for uses in biological imaging since they provide the essential fluorescent contrast to analyze and study cells and tissues [1]. Different luminescent labeling agents, mainly organic dyes, and nanomaterials including semiconductor quantum dots, nanodiamonds, gold nanoparticles [2][3][4], several nanostructures labeled with organic dyes [5], and more recently calcium phosphate apatite nanoparticles (nAp) both labeled with organic dyes [6] or doped with luminescent lanthanides (Ln 3+ ) ions [7,8], have been proposed for these applications. The main limitation of organic dyes is photobleaching [5], while the use of quantum dots is controversial due to their cytotoxicity [9].…”

Photoluminescent Hydroxylapatite: Eu3+ Doping Effect on Biological Behaviour

“…A photoluminescent material is the most promising candidate for clinical applications and implantation. The biocompatibility is not the only important feature, a longer lifetime of luminescence being also an significant benefit in practical applications [35,36].…”

Quenching of the Eu3+ Luminescence by Cu2+ Ions in the Nanosized Hydroxyapatite Designed for Future Bio-Detection

“…HAp) is used in medicine as a bone implant material due to its biocompatibility, bioactivity, and similarity to bone mineral [ 3 , 4 ]. However, it is still widely investigated in order to improve its properties by obtaining appropriate grain size, morphology, mechanical strength, and solubility and by adding some dopants that are, e.g., naturally built into bone apatite, ions possessing antibacterial properties, or ions enabling bio-imaging [ 5 , 6 ]. Infections after grafting of bone implant material are a serious problem in surgery.…”