We synthesized citric acid (Cit)-coordinated Eu3+ and F– codoped hydroxyapatite (Cit/Eu:HA-F) nanoparticles (NPs) and investigated their ion diffusion processes based on photoluminescence (PL) properties at the near-surfaces with thermal treatment. At 85 °C, the Cit coordination layer effectively suppressed the nonradiative deactivation of HA NP surfaces in the PL process, and the quantum yield (ηint) of Eu3+ ions reached a maximum value of ca. 33%, indicating the highest PL efficiency in the HA system. At 250 °C, Cit was decomposed into aconitic acid with a high optical absorption coefficient and reducing ability, so that the ηint of the Eu ions in the NPs were minimized and the partial Eu3+ ions were resultantly reduced to Eu2+ ions. At around 350 °C, the Eu ions were partially diffused from Ca­(I) into Ca­(II) sites. At 550 °C, the proportion of Eu ions in Ca­(II) sites dramatically reached up to ca. 31%, and the F– ions simultaneously diffused into the HA structures by substituting for the OH sites. Therefore, it was elucidated that the Cit molecules coordinated to the Eu and F– codoped HA surfaces achieved higher ηint and promoted the diffusion of various ions into the HA structures with thermal treatment and resultantly controlled the existence ratio of the Eu3+ and Eu2+ ions at the near surfaces, which could be expected to control the PL color by the Cit coordinative mediation technique and realize the creation of cell-labeling luminescent nanomaterials in biomedical fields.

We clarified the surface elution behavior of citric acid (Cit) ions from Cit-coordinated europium­(III) ion (Eu3+)-doped hydroxyapatite (CEH) nanoparticles in three different biological solutions (i.e., phosphate buffer (PB), carbonate buffer (CB), and simulated body fluid (SBF)). Specifically, the elution behavior of Cit from the CEH nanoparticles in SBF was clarified as compared with the cases in PB and CB. Based on the elution results of Cit from the nanoparticles, two-stepwise (i.e., initially dramatic and subsequentially gradual) elution behavior during the immersion was observed, which was mainly driven by the substitutional coordination of HPO4 2– and CO3 2– to the Cit ions on the nanoparticle surfaces. The Cit elution behavior by the immersion was effectively affected by the anions in the biological solutions. The substitutional coordination of HPO4 2– or CO3 2– to the Cit ions was the dominant driving force for the Cit ion elution chelating with Eu3+ and Ca2+ ions, which progressed significantly at the immersion time of 0–3 h in SBF. Subsequently, the complex reactions based on the substitutional coordination would become the equilibrium state at the immersion time of 3–12 h in SBF, suggesting the control of nanoparticle surface states by optimizing the Cit elution behavior. Therefore, we believe that the nanoparticles will be the base nanobiomaterials toward the application for drug delivery system carriers containing both photoluminescence and drug loading functions.

This study was carried out to evaluate the effects of Chinese herbal transdermal ointment on mastitis in the dairy cow and to select the best efficient formula for treating the disorder. With chlorogenic acid as a marker, using high performance liquid chromatography (HPLC), the contents of chlorogenic acid in permeate liquid were determined. Different skin permeation enhancing effects of Chinese herbal medicinal formulations and various herbal transdermal promoters were evaluated in the form of ointment. The results indicated that ultrafined powder (UFP) of Chinese herbal medicine (CHM) directly adding to medication and 4.5% borneol plus 4.5% Azone as skin permeation enhancers showed the best skin-penetrating effect.

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