Encapsulation of dexamethasone into biodegradable polymeric nanoparticles for in vitro cell uptake

Nanotechnology-based delivery systems can be functionalized to achieve tissue- or organ-specific targeting. Moreover, multiple functionalizations can be performed, in order to combine targeting, diagnostic and therapeutic actions. The controlled delivery of bioactive molecules, such as growth factors or hormones, is also a critical aspect in tissue engineering applications. In fact, different biologically active molecules are necessary for regulating cell proliferation, for preserving cell survival, as well as for promoting or maintaining cell differentiated functions. Dexamethasone (DXM) is a synthetic steroidal drug that can be used both for its anti-inflammatory properties and to induce cell differentiation (i.e. in tissue engineering applications). The present work concerns both the optimization of dexamethasone (DXM) entrapment and its release from biodegradable poly(d,l-lactide-coglycolide) (PLGA, 50 :50) nanoparticles prepared by a novel patented methodology and the in vitro uptake studies of such particles into hepatocites. Nanoparticle size and zeta potential were not modified in the presence of DXM and were respectively around 230 nm and −4mV. The in vitro release profiles of the drug from the bioconjugates have been studied. To examine the effect of DXM encapsulation with PLGA on the cellular uptake, in vitro uptake experiments were performed for PLGA-NPs-coumarin 6 and PLGA-NPs-DXM using the human hepatoma cells HepG2. Experiments with the NPs-coumarin 6 showed a relatively rapid uptake during the first hour of incubation, with partial colocalization of fluorescent NPs with secondary endosomal and lysosomal compartments. Results obtained with dexamethasone-loaded NPs showed a sustained antiproliferative effect and greater activation of the CYP3A4 enzyme, as compared with dexamethasone in solution.