Real time measurement of PEG shedding from lipid nanoparticles in serum via NMR spectroscopy.

Small interfering RNA (siRNA) is a novel therapeutic modality that benefits from nanoparticle mediated delivery. The most clinically advanced siRNA-containing nanoparticles are polymer-coated supramolecular assemblies of siRNA and lipids (lipid nanoparticles or LNPs), which protect the siRNA from nucleases, modulate pharmacokinetics of the siRNA, and enable selective delivery of siRNA to target cells. Understanding the mechanisms of assembly and delivery of such systems is complicated by the complexity of the dynamic supramolecular assembly as well as by its subsequent interactions with the biological milieu. We have developed an ex vivo method that provides insight into how LNPs behave when contacted with biological fluids. Pulsed gradient spin echo (PGSE) NMR was used to directly measure the kinetics of poly(ethylene) glycol (PEG) shedding from siRNA encapsulated LNPs in rat serum. The method represents a molecularly specific, real-time, quantitative, and label-free way to monitor the behavior of a nanoparticle surface coating. We believe that this method has broad implications in gaining mechanistic insights into how nanoparticle-based drug delivery vehicles behave in biofluids and is versatile enough to be applied to a diversity of systems.

Evaluations of combination MDR-1 gene silencing and paclitaxel administration in biodegradable polymeric nanoparticle formulations to overcome multidrug resistance in cancer cells.

In this study, the effect of MDR-1 gene silencing, using small interfering RNA (siRNA), and paclitaxel (PTX) co-therapy in overcoming tumor multidrug resistance was examined. Poly(ethylene oxide)-modified poly(beta-amino ester) (PEO-PbAE) and PEO-modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticles were formulated to efficiently encapsulate MDR-1 silencing siRNA and PTX, respectively. Upon administration in multidrug resistant SKOV3(TR) human ovarian adenocarcinoma cells, siRNA-mediated MDR-1 gene silencing was evident at 100 nM dose. Combination of MDR-1 gene silencing and nanoparticle-mediated delivery significantly influenced the cytotoxic activity of PTX in SKOV3(TR) cells similar to what was observed in drug sensitive SKOV3 cells. We speculate that the enhancement in cytotoxicity was due to an increase in intracellular drug accumulation upon MDR-1 gene silencing leading to an apoptotic cell-kill effect. Taken together, these preliminary results are highly encouraging for the development of combination nano-therapeutic strategies that combine gene silencing and drug delivery to provide more potent therapeutic effect, especially in refractory tumors.