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Small interfering RNAs (siRNAs) present a strong therapeutic potential because of their ability to inhibit the expression of any desired protein. Recently, we developed the retro-inverso amphipathic RICK peptide as novel non-covalent siRNA carrier. This peptide is able to form nanoparticles (NPs) by self-assembling with the siRNA resulting in the fully siRNA protection based on its protease resistant peptide sequence. With regard to an in vivo application, we investigated here the influence of the polyethylene glycol (PEG) grafting to RICK NPs on their in vitro and in vivo siRNA delivery properties. A detailed structural study shows that PEGylation did not alter the NP formation (only decrease in zeta potential) regardless of the used PEGylation rates. Compared to the native RICK:siRNA NPs, low PEGylation rates (≤20%) of the NPs did not influence their cellular internalization capacity as well as their knock-down specificity (over-expressed or endogenous system) in vitro. Because the behavior of PEGylated NPs could differ in their in vivo application, we analyzed the repartition of fluorescent labeled NPs injected at the one-cell stage in zebrafish embryos as well as their pharmacokinetic (PK) profile after administration to mice. After an intra-cardiac injection of the PEGylated NPs, we could clearly determine that 20% PEG-RICK NPs reduce significantly liver and kidney accumulation. NPs with 20% PEGylation constitutes a modular, easy-to-handle drug delivery system which could be adapted to other types of functional moieties to develop safe and biocompatible delivery systems for the clinical application of RNAi-based cancer therapeutics., (Copyright © 2017 Elsevier B.V. All rights reserved.)

There is an obvious need to develop pharmacological strategies to protect the heart in patients suffering from acute myocardial infarction. Apoptosis was evidenced as a main contributor of myocardial ischemia-reperfusion (IR) injury. Our cardioprotective strategy was based on the use of four cell penetrating peptides (CPP: Tat, (RXR)4, Bpep and Pip2b) which were conjugated to the BH4-peptide, derived from the BH4 domain of the Bcl-xL anti-apoptotic protein. These CPP-BH4 conjugates were able to reduce staurosporine-induced apoptosis in primary cardiomyocytes in vitro. Although Pip2b-BH4 was more efficient in terms of cellular uptake, it was as efficient as Tat-BH4 for its anti-apoptotic activity. As required for potential therapeutic application their cardioprotective effects were evaluated in an in vivo mouse model of myocardial IR injury. Our results clearly show that a single low dose (1 mg/kg) injection of Tat-BH4 and Pip2b-BH4 administered intravenously 5 min before reperfusion was able to drastically reduce infarct size (~47%) and to inhibit apoptosis (~60%) in the left ventricle of treated mice. Importantly, these effects are not observed following the injection of CPP alone or scrambled version of BH4. This study evidences that the Pip2b CPP, designed for oligonucleotides translocation, as well as the widely used natural Tat CPP exhibit similar efficacy in vivo to deliver BH4 anti-apoptotic peptide to the reperfused myocardium and may thus become useful therapeutic tools to treat acute myocardial infarction in the clinical setting., (Copyright © 2011 Elsevier B.V. All rights reserved.)