Biomimetic calcium phosphate apatites are particularly adapted to bio‐medical applications due to their biocompatibility and high surface reactivity. In this contribution we report three selected examples dealing with mineral/organic interactions devoted to convey new functionalities to apatite materials, either in the form of dry bioceramics or of aqueous colloids. We first studied the adsorption of risedronate (bisphosphonate) molecules, which present potential therapeutic properties for the treatment of osteoporosis. We then addressed the preparation of luminescent Eu‐doped apatites for exploring apatite/collagen interfaces through the FRET technique, in view of preparing “advanced” biocomposites exhibiting close spatial interaction between apatite crystals and collagen fibers. Finally, we showed the possibility to obtain nanometer‐scaled apatite‐based colloids, with particle size tailorable in the range 30–100 nm by controlling the agglomeration state of apatite nanocrystals by way of surface functionalization with a phospholipid moiety. This paper is aimed at illustrating some of the numerous potentialities of calcium phosphate apatites in the bio‐medical field, allowing one to foresee perspectives lying well beyond bone‐related applications.

We present here a new example of aggregation-induced emission enhancement (AIEE), which involves an original mechanism based on the formation of organic ion pairs. The phenol 4-hydroxy-7-nitrobenzoxadiazole (NBDOH) is dissociated in water at pH 5.0 to give the corresponding phenolate, which is poorly fluorescent in this medium. We bring evidence that fluorescence quenching is due to an interaction with water molecules. In the presence of a relatively bulky ammonium salt, specifically tetrabutylammonium bromide (TBAB), NBDOH forms a hydrophobic salt, TBA(+)NBDO(-). This has no influence on the fluorescence of the anion as long as the salt is dissolved. However, the salt readily crystallizes in the medium and transition to the solid state is accompanied by a strong increase in fluorescence intensity. This effect can be explained by two reasons. The anions are protected from water molecules, and above all, the presence of the bulky cations prevents parallel-stacking of the anions, thus leading to an original molecular arrangement that is favorable to fluorescence. As the nature of the organic cation may be easily changed, the versatility of the system is very interesting for the design of new organic micro- and nanoparticles that must be fluorescent in the solid state, possibly in an aqueous environment.

The resistance of synthetic polymers to the action of living systems is becoming more and more problematic in certain domains in which they are used for a limited period of time before becoming waste. It is exemplified in surgery, pharmacology, agriculture and in the environment too. In these domains, time‐resistant polymeric wastes are less and less acceptable. From this viewpoint, sutures, bone fracture fixation devices, mulch films and packagings are comparable. Basically they should be eliminated after use. Post‐use biorecycling is regarded as a possible solution to some of the problems raised by the management of these polymeric wastes, regardless of the domain of application. This contribution aims to present simple and versatile methods with a potential to investigate the fate, and especially the bioassimilation, of the degradation by‐products of degradable or bio‐degradable polymers in complex living media such as the human body, a compost or the outdoor environment. Two versatile methods are presented that have been developed to radio‐label degradable and biodegradable artificial aliphatic polyesters by substituting some protons by tritium atoms. It is also shown that weighing a population of starved earthworms, allowed to be in contact with degradable or biodegradable polymer, is a worthwhile method to demonstrate that degradation by‐products are bioassimilated.© 2002 Society of Chemical Industry

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Lactic acid‐containing polymers obtained by the ring opening polymerization of lactides are now commercially available as bioresorbable polymers, or as devices that can be assimilated by the human body, or by living species present in the outdoor environment. Studying the mechanisms of lactide polymerization or polylactide degradation and monitoring the fate of the degradation compounds produced from the polymers when they degrade in complex media is thus very important and basically feasible via the labeling of polymer chains. Therefore, the possibility of exchanging some of the protons borne by lactide monomer molecules by deuterium or tritium was investigated. The substitution reactions involving deuterium were conducted and optimized using the High Temperature Solid State Catalytic Isotopic Exchange (HSCIE) method and applied to solid DL‐lactide in the presence of various catalysts. The most active and stable catalyst was palladium on calcium carbonate. The analyses of the resulting deuterated compounds by 1H NMR and mass spectrometry showed that substitution involved mainly the tertiary proton and that the reaction temperature and flask volume were critical factors. The experimental conditions that led to convenient hydrogen‐deuterium exchange yields were then applied to hydrogen‐tritium exchange. Highly radioactive DL‐lactide having a specific activity of 150 GBq/mmol. (4.05 Ci/mmol.) was successfully synthesized. Copyright © 1998 John Wiley & Sons, Ltd.

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