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Sterically stabilized biocompatible poly(lactic acid) (PLA) nanospheres were prepared by an o/w emulsion/evaporation technique, using hydrophobically modified dextrans (DexP) as the emulsion stabilizer. Photon correlation spectroscopy, zetametry, and differential scanning calorimetry studies corroborated that interfacial adhesion between immiscible dextran and PLA chains was achieved by compatibilization of polymer segments via hydrophobic groups grafted onto dextran and thus leading to the formation of entanglements between the hydrophobic dextran parts and the PLA matrix. The presence of dextran exposed at the particle surface was confirmed by X-ray photoelectron spectroscopy and by the fact that the suspensions showed an increased stability in concentrated NaCl solutions and a reduction of bovine serum albumin adsorption compared to uncoated PLA nanoparticles. A comparison of the characteristics of PLA nanospheres DexP-coated via the emulsion procedure (NS(em)) with those of PLA particles coated by DexP adsorption (NS(ad)) suggests that the conformation of the polymer in the superficial layers may be different. However, both DexP layers behave similarly in terms of stability and protein adsorption.

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Hyaluronic acid (HA) has a high affinity for the CD44 receptor present at the surface of articular cells, particularly of chondrocytes. HA-covered polylactide nanoparticles containing bioactive compounds such as HA and chondroitin sulfate (CS) were thus prepared in order to achieve a controlled delivery targeted to cartilage cells after injection near articular alterations/erosions. Such nanoparticles (diameter = 700 nm) were prepared by double emulsion/solvent evaporation, using amphiphilic derivatives of HA, as stabilizer of the secondary emulsion. These nanoparticles were incubated with articular cells, and several tests were carried out. First, they proved that the nanospheres provoked no decrease in cell viability, even after 72 h of contact. Second, a confocal microscopy analysis on fluorescent HA-covered particles showed that they were captured by articular cells, while with those covered with poly(vinyl alcohol), the uptake was far lower. Third, a scattering electron microscopy analysis proved that the HA-coated nanoparticles were localized in the cell intracytoplasmic area.

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