Rational modification of oligoarginine for highly efficient siRNA delivery: structure-activity relationship and mechanism of intracellular trafficking of siRNA.

Recently, cell-penetrating peptides (CPPs) have received much attention for cellular delivery of therapeutic molecules. However, in the case of CPPs as carriers for siRNA delivery, their utility is often restricted by low cellular uptake and/or entrapment in endosomes. Here, in order to deliver siRNAs with high efficiency, oligoarginine, a prominent member in CPPs, is rationally modified with oligohistidine and stearyl moieties (STR-) by fully taking into account the formation of nanoparticles, uptake and intracellular trafficking. We show that when the ratio of histidine/arginine in a peptide sequence is >1.5, pronounced gene silencing is induced. Following this rule, STR-HnR8 (n=16 and 20) are developed, which show a high knockdown efficiency rarely reported before. Finally, we find that endosomal escape of siRNA induced by stearylated and oligohistidylated oligoarginine is only from "proton-sponge" effect. Taken together, our results suggest a new strategy for the improvement of CPP-based siRNA delivery systems. FROM THE CLINICAL EDITOR: This study present a novel cell penetrating peptide-based siRNA delivery system utilizing modified oligo-arginine demonstrating a successful siRNA delivery approach.

Ultrasonication-assisted one-step self-assembly preparation of biocompatible fluorescent-magnetic nanobeads for rare cancer cell detection.

Multifunctional nanomaterials simultaneously possessing attractive properties, such as strong fluorescent intensity, excellent superparamagnetic behavior, easy modification and good biocompatibility, are always desired in a wide range of applications. In this work, we present a facile ultrasonication-assisted one-step self-assembly strategy for the fabrication of smart fluorescent-magnetic nanobeads (FMNBs) without using a matrix. Via one-step ultrasonication, organic-soluble superparamagnetic nanoparticles (MNPs) and quantum dots (QDs) were automatically encapsulated by amphiphilic (2-hydroxyl-3-dodecanoxyl) propylcarboxymethylchitosans (HDP-CMCHSs) through hydrophobic interaction to form hydrophilic FMNBs, presenting a good QD fluorescent property and a strong MNP magnetic response. The outer surface of the FMNBs was derived from natural biopolymer chitosans, enabling FMNBs with good biocompatibility and convenience for biological modification. As-prepared FMNBs can be easily modified with streptavidin, facilitating bioconjugation with biotin-labeled human epidermal growth factor (hEGF). hEGF-functionalized FMNBs are able to specifically recognize and capture rare target cells spiked in white blood cells, and the recovered cells can be further cultured for a long time. All of these excellent properties make nanobeads promising for circulating tumor cell (CTC) detection.

pH-responsive mechanism of a deoxycholic acid and folate comodified chitosan micelle under cancerous environment.

Smart pH-responsive polymeric micelles have attracted much attention as one of the most promising drug delivery candidates. In this paper, a different substitution of deoxycholic acid (DCA) and folic acid (FA) comodified hydroxypropyl chitosans (HPCHS) were synthesized for doxorubicin (DOX) targeted delivery and controllable release. The results indicate that the DOX-release behavior is pH-responsive and closely related with the grafting proportions of the two hydrophobic ingredients. The pH-responsive mechanism for the optimized (6%DCA)-HPCHS-(0.1%FA) was suggested, resulting from a synergistic effect of gradual hydrolysis of the amido bond and electrostatic repulsion between the subsequently protonated DOX and the amino residue of the chitosan backbone under a cancerous microenvironment. Moreover, the DOX/(6%DCA)-HPCHS-(0.1%FA) micelle as a promising targeted drug delivery system in cancer therapy was evaluated by cell growth inhibition assays and confocal laser microscopy in vitro. The results clearly demonstrate a controlled release of its cargo and promoted curative efficacy of DOX.

Shell modulation by tailoring substituents in chitosan for LbL-assembled microcapsules.

By AFM we report the successful modulation of shell structure (morphology and shell thickness) of microcapsules through tailoring molecular substituents of chitosan. The shell thickness of hollow (HPCS/SA)(n) (n=5, 7, 9) capsules is more than 3 times that of the (QACS/SA)(n) (n=5, 7, 9) capsules, due to less charges carried by the neutral -NH(2) substituent group and the induced coily conformation in HPCS, while more charges carried by the positively charged -N(CH(3))(3)(+) substituent and the induced extended conformation in QACS (HPCS: hydroxyl propyl chitosan; QACS: quaternary ammonium chitosan; SA: sodium alginate). The ultrathin shells of microcapsules assembled in this work by the layer-by-layer (LbL) self-assembly technique rather than the traditional method of mixing CS, SA and CaCl(2) enable the thickness modulation characterization by AFM on the atomic scale. These microcapsules with tunable shell thickness provide important guidance for potential drug delivery and sustained release.

Synthesis and characterization of carboxymethyl-polyaminate chitosan and its adsorption behavior toward a reactive dye.

Carboxymethyl-polyaminate chitosan (DETA-CMCHS), a novel kind of amphoteric chitosan derivative, was prepared and characterized by elemental analysis, and by IR and (1)H NMR spectroscopy. The adsorption behavior of Reactive Blue (RB2) on DETA-CMCHS was also studied. Results showed that the maximum value of adsorption capacity was 1185.71 mg/g at pH 3. The adsorption kinetic behavior was fitted with a second-order reaction rate equation. The adsorption was an exothermic, irreversible and entropy-reduced process according to thermodynamic parameters, such as standard Gibbs free-energy change, enthalpy change, and entropy change, all of which were calculated from adsorption equilibrium data.

Preparation and properties of chitosan chondroitin sulfate complex microcapsules.

The chitosan (CHS) chondroitin sulfate (CS) complex microcapsules were prepared by emulsion-chemical crosslink method, with the chitosan and chondroitin sulfate as the wall materials and the low molecular weight heparin (LMWH) as the core materials. The microcapsules were characterized by Fourier transform infrared (IR) spectrometry, scanning electron microscope (SEM), size distribution and thermal analysis. The in vitro drug release behavior of the microcapsules was studied by spectrophotometry. The SEM and size distribution showed that the microcapsules were in the spherical form mostly in the size range of 20-80 microm. The IR spectrum indicated that there were electrostatic interactions between chitosan and chondroitin sulfate, with the sulfate group and free carboxyl group reacted with the amino groups of chitosan. The DSC result showed that the wall materials could protect the core materials of the microcapsules. The results of the release kinetics experiments of the microcapsules showed that the drug released slightly faster in acid media than in alkali ones.

Surface and aggregate properties of an amphiphilic derivative of carboxymethylchitosan.

A new kind of amphiphilic derivative of carboxymethylchitosan, a group of (2-hydroxyl-3-butoxyl)propylcarboxymethylchitosans (HBP-CMCHS), has been synthesized, and the surface and aggregate properties have been studied by means of surface tension, surface pressure and fluorescence measurements. HBP-CMCHS can adsorb on the surface to decrease the surface tension of the solution. The adsorption film was quite stable, which can make the relative compressed pressure increase dramatically with the decrease of the surface area. In solution, hydrophobic aggregations were identified by the decrease in the ratio of the fluorescence emission intensity of the first and third pyrene vibronic peaks ( I(1)/ I(3)). Results showed that the aggregation began to form at a concentration similar to that of the polymer transfer to the air-water interface. Aggregate formation of the polymers is a gradually compact process with hydrophobic associations. Increase of DS and addition of NaCl to the HBP-CMCHS solution can make the surface tension decrease, make the aggregation occur at lower concentration, and make the aggregation more hydrophobic.