Glycine-rich regions feature prominently in intrinsically disordered regions (IDRs) of proteins that drive phase separation and the regulated formation of membraneless biomolecular condensates. ...Interestingly, the Gly-rich IDRs seldom feature poly-Gly tracts. The protein fused in sarcoma (FUS) is an exception. This protein includes two 10-residue poly-Gly tracts within the prion-like domain (PLD) and at the interface between the PLD and the RNA binding domain. Poly-Gly tracts are known to be highly insoluble, being potent drivers of self-assembly into solid-like fibrils. Given that the internal concentrations of FUS and FUS-like molecules cross the high micromolar and even millimolar range within condensates, we reasoned that the intrinsic insolubility of poly-Gly tracts might be germane to emergent fluid-to-solid transitions within condensates. To assess this possibility, we characterized the concentration-dependent self-assembly for three non-overlapping 25-residue Gly-rich peptides derived from FUS. Two of the three peptides feature 10-residue poly-Gly tracts. These peptides form either long fibrils based on twisted ribbon-like structures or self-supporting gels based on physical cross-links of fibrils. Conversely, the peptide with similar Gly contents but lacking a poly-Gly tract does not form fibrils or gels. Instead, it remains soluble across a wide range of concentrations. Our findings highlight the ability of poly-Gly tracts within IDRs that drive phase separation to undergo self-assembly. We propose that these tracts are likely to contribute to nucleation of fibrillar solids within dense condensates formed by FUS.
Mucosal surfaces pose a challenging environment for efficient drug delivery. Various delivery strategies such as nanoparticles have been employed so far; yet, still yielding limited success. To ...address the need of efficient transmucosal drug delivery, this report presents the synthesis of novel disulfide‐containing dendritic polyglycerol (dPG)‐based nanogels and their preclinical testing. A bifunctional disulfide‐containing linker is coupled to dPG to act as a macromolecular crosslinker for poly‐N‐isopropylacrylamide (PNIPAM) and poly‐N‐isopropylmethacrylamide (PNIPMAM) in a precipitation polymerization process. A systematic analysis of the polymerization reveals the importance of a careful polymer choice to yield mucus‐degradable nanogels with diameters between 100 and 200 nm, low polydispersity, and intact disulfide linkers. Absorption studies in porcine intestinal tissue and human bronchial epithelial models demonstrate that disulfide‐containing nanogels are highly efficient in overcoming mucosal barriers. The nanogels efficiently degrade and deliver the anti‐inflammatory biomacromolecule etanercept into epithelial tissues yielding local anti‐inflammatory effects. Over the course of this work, several problems are encountered due to a limited availability of valid test systems for mucosal drug‐delivery systems. Hence, this study also emphasizes how critical a combined and multifaceted approach is for the preclinical testing of mucosal drug‐delivery systems, discusses potential pitfalls, and provides suggestions for solutions.
Novel disulfide‐containing dendritic polyglycerol‐based nanogels act as highly efficient transmucosal drug delivery systems. Upon encountering the mucus layer, they undergo gradual redox‐dependent degradation, and thus are able to penetrate the mucous barrier and achieve efficient intraepithelial drug delivery of encapsulated therapeutics (e.g., etanercept). Here, comprehensive, and multifaceted approaches are implemented to overcome distinct pitfalls and shortcomings of current mucous test systems.
Abstract Cell-responsive hydrogels hold tremendous potential as cell delivery devices in regenerative medicine. In this study, we developed a hydrogel-based cell delivery vehicle, in which the ...encapsulated cell cargo control its own release from the vehicle in a protease-independent manner. Specifically, we have synthesized a modified poly(ethylene glycol) (PEG) hydrogel that undergoes degradation responding to cell-secreted molecules by incorporating disulfide moieties onto the backbone of the hydrogel precursor. Our results show the disulfide-modified PEG hydrogels disintegrate seamlessly into solution in presence of cells without any external stimuli. The rate of hydrogel degradation, which ranges from hours to months, is found to be dependent upon the type of encapsulated cells, cell number, and fraction of disulfide moieties present in the hydrogel backbone. The differentiation potential of human mesenchymal stem cells released from the hydrogels is maintained in vitro . The in vivo analysis of these cell-laden hydrogels, through a dorsal window chamber and intramuscular implantation, demonstrated autonomous release of cells to the host environment. The hydrogel-mediated implantation of cells resulted in higher cell retention within the host tissue when compared to that without a biomaterial support. Biomaterials that function as a shield to protect cell cargos and assist their delivery in response to signals from the encapsulated cells could have a wide utility in cell transplantation and could improve the therapeutic outcomes of cell-based therapies.
We analyzed the protein corona of thermoresponsive, poly(N-isopropylacrylamide)- or poly(N-isopropylmethacrylamide)-based nanogels.
Traces of protein corona detected after incubation in human serum ...were characterized by proteomics and dynamic light scattering in undiluted serum.
Apolipoprotein B-100 and albumin were the main components of the protein coronae. For dendritic polyglycerol-poly(N-isopropylacrylamide) nanogels at 37°C, an increase in adsorbed immunoglobulin light chains was detected, followed by partially reversible nanogel aggregation. All nanogels in their hydrophilic state are colloidally stable in serum and bear a dysopsonin-rich protein corona.
We observed strong changes in NG stability upon slight alterations in the composition of the protein coronae according to nanogel solvation state. Nanogels in their hydrophilic state possess safe protein coronae.
Polypeptide-coated silica nanoparticles represent an interesting class of organic-inorganic hybrids since the ordered secondary structure of the polypeptide grafts imparts functional properties to ...these nanoparticles. The synthesis of a poly-l-glutamic acid (PLGA) silica nanoparticle hybrid by employing N-carboxyanhydride (NCA) polymerization to synthesize the polypeptide chains and Cu catalyzed azide alkyne cycloaddition reaction to graft these chains onto the silica surface is reported. This methodology enables the synthesis of well-defined polypeptide chains that are attached onto the silica surface at high surface densities. The PLGA-silica conjugate particles are well dispersed in water, and have been thoroughly characterized using multinuclear ((13)C, (29)Si) solid state NMR, thermogravimetric analysis, Fourier transform infrared, dynamic light scattering, and transmission electron microscopy. The pH-dependent reversible aggregation of the PLGA-silica particles, driven by the change in PLGA structure, has also been studied. Preliminary results on the use of aqueous dispersions of silica-PLGA for the preparation of three-dimensional macroporous structures with oriented pores by ice templating methodology are also demonstrated. These macroporous materials, comprising a biocompatible polymer shell covalently attached to rigid inorganic cores, adopts an interesting lamellar structure with fishbone-type architecture.
Dendritic thermoresponsive nanogels loaded with cytochrome c corona induce controlled apoptosis upon sample cooling.
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The use of thermoresponsive nanogels (NGs) allows the controlled ...release of therapeutic molecules upon a thermal switch. Usually, this strategy involves the use of temperature increase to activate cargo expulsion from shrinking NGs. In this study, poly(N-isopropylacrylamide) (pNIPAM)-based NGs were involved in the release of a therapeutic protein corona by temperature decrease. NGs based on dendritic polyglycerol (dPG) and thermoresponsive pNIPAM were semi-interpenetrated with poly(4-acryloylamine-4-(carboxyethyl)heptanodioic acid) (pABC). The resulting semi-interpenetrated NGs retain the thermoresponsive properties of pNIPAM, together with pH-responsive, dendritic pABC as a secondary network, in one single nanoparticle. Semi-interpenetrated polymer network (SIPN) NGs are stable in physiological conditions, exhibit a reversible phase transition at 35 °C, together with tunable electrophoretic mobilities around the body temperature. The binding of cytochrome c (cyt c) was successful on SIPN NGs in their collapsed state at 37 °C. Upon cooling of the samples to room temperature, the swelling of the NG effectively boosted the release of cyt c, as compared with the same kept at constant 37 °C. These responsive SIPN NGs were able to deliver cyt c to cancer cells and specifically induce apoptosis at 30 °C, while the cells remained largely unaffected at 37 °C. In this way, we show therapeutic efficacy of thermoresponsive NGs as protein carriers and their efficacy triggered by temperature decrease. We envision the use of such thermal trigger as relevant for the treatment of superficial tumors, in which induction of apoptosis can be controlled by the application of local cooling agents.
Techniques that can create three-dimensional (3D) structures to provide architectural support for cells have a significant impact in generating complex and hierarchically organized tissues/organs. In ...recent times, a number of technologies, including photopatterning, have been developed to create such intricate 3D structures. In this study, we describe an easy-to-implement photopatterning approach, involving a conventional fluorescent microscope and a simple photomask, to encapsulate cells within spatially defined 3D structures. We have demonstrated the ease and the versatility of this approach by creating simple to complex as well as multilayered structures. We have extended this photopatterning approach to incorporate and spatially organize multiple cell types, thereby establishing coculture systems. Such cost-effective and easy-to-use approaches can greatly advance tissue engineering strategies.
Mesoporous silica nanoparticles (MSNs), that are capable of delivering gene and drugs to organisms in an effective and selective way have attracted much attention lately for its potential in the ...treatment of cancer. However, the successful application of MSNs for delivery of plasmid DNA or drugs requires surface modification of the silica with positively charged functional groups so that it binds to the negatively charged nucleic acids and also helps it penetrate through the cell membrane. We report for the first time the synthesis of a hybrid MSN where the cell penetrating cationic polypeptide poly‐L‐arginine synthesized by NCA polymerization is grafted onto the external surface of MSN using click chemistry. These poly‐L‐arginine grafted MSNs show low cytotoxity (85% cell viability at 100 μg/mL MSN concentration) and high cellular uptake by both HeLa and A549 (>90%). The poly‐L‐arginine grafted MSNs were used effectively to deliver mCherry DNA plasmid into cells leading to expression of the protein mCherry inside the cells (transfection efficiency 60%). In contrast, poly‐L‐arginine grafted non‐porous silica nanoparticles were unable to express the protein mCherry inside the cells although their uptake into the cells was as efficient as with poly‐L‐arginine grafted MSNs. We also show preliminary results to demonstrate that these hybrid MSNs can be used as a delivery vehicle for the anticancer drug Doxorubicin towards cancerous cells HeLa and A549. The biocompatibility of poly‐L‐arginine and its cell penetrating ability are expected to make these MSN conjugates very useful carriers for the delivery of genes and drugs into cancer cells.
Poly‐L‐arginine grafted mesoporous silica nanoparticles have been shown to be an efficient carrier for the transfection of DNA plasmid and the delivery of anti‐cancer drug Doxorubicin into cancer cells.
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