Preparation of poly(D,L-lactide) nanoparticles assisted by amphiphilic poly(methyl methacrylate-co-methacrylic acid) copolymers

When co-precipitated with amphiphilic copolymers from DMSO, poly(D,L-lactide) (PLA) can be readily converted into stable sub-200 nm nanoparticles by addition of an aqueous phase, free of any polymeric stabilizers such as poly(vinyl alcohol) or Poloxamer. In this work, the ability of random poly(methyl methacrylate-co-methacrylic acid) copolymers (PMMA-co-MA) to stabilize PLA nanoparticles was demonstrated, and the properties of PLA/PMMA-co-MA nanoparticles were investigated. When co-precipitated with PMMA-co-MA, PLA was totally converted into nanoparticles using a polymer concentration in DMSO (Cp) below 17.6 mg ml(-1), and a PMMA-co-MA proportion above a critical value depending on the content of MA repeating units (X). For instance, the lowest PMMA-co-MA proportion required was 0.9 mg mg(-1) PLA for X = 12%, and 0.5 mg mg(-1) PLA for X = 25% (for C(PLA) = 16 mg ml(-1) DMSO). The nanoparticle diameter was essentially independent of X, the proportion of PMMA-co-MA, and the PLA molecular weight, except for oligomers for which the nanoparticle diameter was smaller. It decreased when the organic phase was diluted (126 +/- 13 nm for Cp = 17.6 mg ml(-1), and 81 +/- 5 nm for C(P) = 5.6 mg ml(-1)). The time-dependence of the stability and the degradation of PLA/PMMA-co-MA nanoparticles was discussed. One of the main advantages of this technique is the ability to control surface properties and to bring functional groups to otherwise non-functionalized PLA nanoparticles. To illustrate this, a conjugate of PMMA-co-MA25 and biotin was synthesized, and used to prepare biotinylated nanoparticles that could be detected by fluorescence and transmission electron microscopy after infiltration into ligatured rat small intestine

Neolithic Human Societies and Woodlands in the North-Western Mediterranean Region: Wood and Charcoal Analysis

International audienc

The migration of beech ( Fagus sylvatica L.) up the Rhone: the Mediterranean history of a “mountain” species

http://dx.doi.org/10.1007/s00334-005-0068-9International audienceNew anthracological data on the beech (Fagus sylvatica L.), obtained through rescue excavations, allows the proposal of a new pattern of population by beech of the South of France since the Lateglacial. Due to itscurrent ecology and distribution it is considered to be a mountain species in the Mediterranean area despite the presence of beech forests, usually described as glacial relicts, at low altitudes in the South of France and in the Rhone valley (Sainte-Baume, Valbonne and Grand Fays). Our results, combined with previous pollen and charcoal data, show both an early spread from glacial refuges and a late disappearance of the species. During the glacial period, the beech remained in the southernmost zones. From there, it first spread during the Preboreal towards outposts in the Rhone delta, and during the Atlantic along the rhodanian corridor. During the Subboreal, a retreat of beech towards the Pre-Alps and the Rhone delta can be traced. The Iron Age and the Classical period experienced the maximal concentration of beech along the Rhone river, while it became more rare in the North and in the South. During the Middle Ages, it first disappeared from these distal areas, and later also in the valley (around A.D.1000), finally settling in its present mountainous distribution area (probably around the 14th century A.D.). Some crucial points of the proposed dynamics are further analysed: the paradoxical regression of beech in the valley during the Subboreal, the factors determining the expansion of beech from refuge areas during the Subatlantic and finally, the disappearance of the beech in the middle Rhone valley in rather recent times, a disappearance attributed to the strong human impact on the landscape.Les nouvelles données anthracologiques concernant le hêtre (Fagus sylvatica L.), obtenues grâce au développement de l'archéologie préventive, permettent de proposer un nouveau modèle de diffusion de cette espèce depuis le Tardiglaciaire. D'après son écologie et sa distribution actuelles, elle est considérée comme une espèce montagnarde dans la région méditerranéenne, en dépit de la présence de hêtraies, souvent envisagées comme des reliques glaciaires, à basse altitude dans le sud de la France et dans la vallée du Rhône (Sainte-Baume, Valbonne et le Grand Fays). Nos résultats, combinées aux données polliniques et anthracologiques préexistantes, montrent une diffusion précoce à partir des refuges glaciaires, et une disparition tardive de cette espèce. Au cours de la période glaciaire, le hêtre s'est maintenu dans les zones les plus méridionales, puis s'est diffusé au cours du Préboréal, à partir d'avant-postes localisés dans le delta du Rhône, et au cours de l'Atlantique le long du couloir rhodanien avant de se replier vers les Préalpes et le delta du Rhône au Subboréal. L'Âge du Fer et l'Antiquité connaissent la concentration maximale du hêtre le long du Rhône, alors qu'il se raréfie au nord et au sud de la zone. Au Moyen Âge, il disparaît tout d'abord de ces zones distales, et ensuite de la vallée (vers 1000 A.D.), pour s'installer définitivement dans sa zone de répartition actuelle (probablement autour du 14eme siècle). Quelques points cruciaux de la dynamique de peuplement sont analysés : la régression paradoxale du hêtre dans la vallée au Subboréal, le déterminisme de son expansion à partir des zones refuges au cours du Subatlantique et, finalement, sa disparition de la moyenne vallée du Rhône à une période récente, disparition attribuée à la forte emprise humaine sur le paysage

A new scenario for the Quaternary history of European beech populations: palaeobotanical evidence and genetic consequences

Here, palaeobotanical and genetic data for common beech (Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. Four large datasets are presented, including over 400 fossil-pollen sites, 80 plant-macrofossil sites, and 450 and 600 modern beech populations for chloroplast and nuclear markers, respectively. The largely complementary palaeobotanical and genetic data indicate that: (i) beech survived the last glacial period in multiple refuge areas; (ii) the central European refugia were separated from the Mediterranean refugia; (iii) the Mediterranean refuges did not contribute to the colonization of central and northern Europe; (iv) some populations expanded considerably during the postglacial period, while others experienced only a limited expansion; (v) the mountain chains were not geographical barriers for beech but rather facilitated its diffusion; and (vi) the modern genetic diversity was shaped over multiple glacial-interglacial cycles. This scenario differs from many recent treatments of tree phylogeography in Europe that largely focus on the last ice age and the postglacial period to interpret genetic structure and argue that the southern peninsulas (Iberian, Italian and Balkan) were the main source areas for trees in central and northern Europ