Carbohydrate-Based Nanocarriers Exhibiting Specific Cell Targeting with Minimum Influence from the Protein Corona.

Whenever nanoparticles encounter biological fluids like blood, proteins adsorb on their surface and form a so-called protein corona. Although its importance is widely accepted, information on the influence of surface functionalization of nanocarriers on the protein corona is still sparse, especially concerning how the functionalization of PEGylated nanocarriers with targeting agents will affect protein corona formation and how the protein corona may in turn influence the targeting effect. Herein, hydroxyethyl starch nanocarriers (HES-NCs) were prepared, PEGylated, and modified on the outer PEG layer with mannose to target dendritic cells (DCs). Their interaction with human plasma was then studied. Low overall protein adsorption with a distinct protein pattern and high specific affinity for DC binding were observed, thus indicating an efficient combination of "stealth" and targeting behavior.

Tailoring the stealth properties of biocompatible polysaccharide nanocontainers.

Fundamental development of a biocompatible and degradable nanocarrier platform based on hydroxyethyl starch (HES) is reported. HES is a derivative of starch and possesses both high biocompatibility and improved stability against enzymatic degradation; it is used to prepare nanocapsules via the polyaddition reaction at the interface of water nanodroplets dispersed in an organic miniemulsion. The synthesized hollow nanocapsules can be loaded with hydrophilic guests in its aqueous core, tuned in size, chemically functionalized in various pathways, and show high shelf life stability. The surface of the HES nanocapsules is further functionalized with poly(ethylene glycol) via different chemistries, which substantially enhanced blood half-life time. Importantly, methods for precise and reliable quantification of the degree of functionalization are also introduced, which enable the precise control of the chemistry on the capsules' surface. The stealth properties of these capsules is studied both in-vitro and in-vivo. The functionalized nanocapsules serve as a modular platform for specific cell targeting, as they show no unspecific up-taken by different cell types and show very long circulating time in blood (up to 72 h).

(Oligo)mannose functionalized hydroxyethyl starch nanocapsules: en route to drug delivery systems with targeting properties.

Hydroxyethyl starch nanocapsules (NCs) are potentially interesting hydrophilic drug delivery carriers, since they do not show non-specific interactions with the living cells. Only the presence of a targeting agent on their surface allows them to target specifically the desired site of action. In this paper, we report the synthesis and cell uptake of crosslinked hydroxyethyl starch (HES) NCs decorated with (oligo)mannose, which is an effective targeting agent for macrophage and dendritic cells. The crosslinked HES NCs were prepared via the interfacial polyaddition of HES with 2,4-toluene diisocyanate (TDI) in inverse (water-in-oil) miniemulsion and then functionalized with (oligo)mannose following two different strategies. To compare the activity and availability of a targeting agent, different types of mannose molecules such as α-d-mannopyranosylphenyl isothiocyanate, 3-O-(α-d-mannopyranosyl)-d-mannose and α3,α6-mannotriose were used for the functionalization of NCs. The availability of the mannose was unambiguously assessed by interaction with a fluorescent lectin. Moreover, the accessibility of the pilot molecule was improved by the presence of a PEG linker at the surface of the NCs. To simulate in vivo conditions, where proteins interact with nanoparticles with a possible hindrance of the accessibility to the targeting agent, the mannosylated NCs were first incubated with human serum before interaction with the fluorescent lectin. Enhancement of uptake into dendritic cells demonstrates the targeting ability in in vitro studies.

A murine ESC-like state facilitates transgenesis and homologous recombination in human pluripotent stem cells.

Murine pluripotent stem cells can exist in two functionally distinct states, LIF-dependent embryonic stem cells (ESCs) and bFGF-dependent epiblast stem cells (EpiSCs). However, human pluripotent cells so far seemed to assume only an epiblast-like state. Here we demonstrate that human iPSC reprogramming in the presence of LIF yields human stem cells that display morphological, molecular, and functional properties of murine ESCs. We termed these hLR5 iPSCs because they require the expression of five ectopic reprogramming factors, Oct4, Sox2, Klf4, cMyc, and Nanog, to maintain this more naive state. The cells are "metastable" and upon ectopic factor withdrawal they revert to standard human iPSCs. Finally, we demonstrate that the hLR5 state facilitates gene targeting, and as such provides a powerful tool for the generation of recombinant human pluripotent stem cell lines.