Nowadays many drugs with improved therapeutic efficacy and fewer side effects are discovered, but cannot be applied due to their low solubility and subsequent low bioavailability. One approach to overcome these obstacles and make these drugs applicable is their encapsulation into polymer-based nanoparticles. Multiple techniques are available for the formulation of drug-loaded polymeric particles, e.g. nanoprecipitation of a polymer/drug solution (either by syringe injection, utilization of pipetting robots or microfluidic devices), or emulsion techniques where droplet and particle formation are induced by application of high energy ultrasound or microfluidic chips. For efficient encapsulation of drugs into nanoparticle carriers various key parameters must be considered, e.g. the nature of the drug and the polymer, their hydrophobicity and concentration on one side, and on the other side solvents, additives and surfactants. In a nutshell, a versatile toolbox is accessible for tailored drug-loaded nanoparticles; however, a subsequent comprehensive characterization is inevitable for each formulation.
In order to investigate the encapsulation of anti-inflammatory drugs (Bisindolylmaleimide I, TG201, TH34, BRP187) into polymers like PLGA, acetalated dextran and novel polyesters, different formulations utilizing different methods, polymer/drug ratios, type and concentrations of surfactants were prepared and characterized for the following particle properties: size distribution, surface charge, formulation stability, encapsulation efficiency and drug loading capacity. Standard characterization techniques, such as dynamic light scattering (DLS), UV-Vis measurements and HPLC analysis were complemented by advanced analytic ultracentrifugation (AUC) studies, nanoparticle tracking analysis (NTA) and asymmetrical flow field-flow fractionation (AF4) measurements. As final investigations in vitro studies were performed to evaluate the beneficial effect of the nanocarriers over the free drug, i.e. a prolonged circulation time and/or an improved bioavailability.