Preparation and Physicochemical Characteristics of Luminescent Apatite-Based Colloids

Abstract

Luminescent colloidal nanosystems based on europium-doped biomimetic apatite were prepared and investigated. The colloids were synthesized by soft chemistry in the presence of a phospholipid moiety, 2-aminoethylphosphoric acid (AEP), with varying europium doping rates. Physicochemical features, including compositional, structural, morphological, and luminescence properties, were examined. Experimental evidence showed that suspensions prepared from an initial Eu/(Eu + Ca) molar ratio up to 2% consisted of singlephased biomimetic apatite nanocrystals covered with AEP molecules. The mean particle size was found to depend closely on the AEP content, enabling the production of apatite colloids with a controlled size down to ca. 30 nm. The colloids showed luminescence properties typical of europium-doped systems with narrow emission bands and long luminescence lifetimes of the order to the millisecond, and the data suggested the location of Eu 3+ ions in a common crystallographic environment for all the colloids. These systems, stable over time and capable of being excited in close-to-visible or visible light domains, may raise interest in the future in the field of medical imaging.

Biomimetic Apatite-Based Functional Nanoparticles as Promising Newcomers in Nanomedicine: Overview of 10 Years of Initiatory Research

“…These have been described in previous occurrences [33,42]. Briefly, in the case of europium, main luminescence maxima (recorded under excitation at 393 nm) were localized in 4 -AEP represents indeed the hydrophilic head of phosphatidylethanolamine, one type of phospholipids constitutive of cell membranes [41].…”

“…The protocol used for synthesizing apatite-based colloids was described previously [33]. All starting salts were at least of reagent-grade purity.…”

“…Such ionic substitutions, at least up to 2 at % of Eu or Tb relative to the calcium content per apatite unit formula, were shown to be effective by the observation by XRD of a single apatite phase in each case. The substitution of divalent calcium by trivalent europium or terbium in the apatitic crystallographic array was discussed elsewhere in detail [33]; for non-stoichiometric apatites, several substitution scenarios can contribute to facilitate this process.…”

The Biomimetic Approach to Design Apatites for Nanobiotechnological Applications

“…Their size can easily be controlled by stabilizing agents, such as polymers or nucleic acids. The nanoparticles can be made to fluoresce by the incorporation of lanthanide ions and they can also act as carriers for different drugs (Al-Kattan et al, 2010). For example, one of the most efficient ways to improve the bone forming ability of biomaterials is their association with bone morphogenetic proteins (Autefage et al, 2009).…”

Estudo, caracterização e propriedades de ortofosfatos multifuncionais

“…Há também os métodos de processamento a alta temperatura, representados pelo método de combustão [59] e a pirólise [94]. Em relação aos métodos por via úmida pode-se destacar os tratamentos hidrotérmicos [7,95,96], a precipitação química [49,97,98], precipitação química assistida por tratamento ultrassônico [28,99], precipitação química com aditivos orgânicos [11,100,101], hidrotérmico assistido por micro-ondas [102], Sol-Gel [103] e a hidrólise dos precursores [104][105][106]. Cada uma das metodologias desenvolvidas apresenta suas próprias vantagens e desvantagens, as quais devem ser levadas em conta durante o desenvolvimento da pesquisa científica.…”