Category: G. Subra

Inorganic polymerization: an attractive route to biocompatible hybrid hydrogels

Posted by Lubomir Vezenkov on

J. Mater. Chem. B, 2018,6, 3434-3448,  doi 10.1039/C8TB00456K

 Montheil T,  Echalier C,  Martinez J, Subra S,  Mehdi A

Abstract

As an intermediate state between liquid and solid materials, hydrogels display unique properties, opening a wide scope of applications, especially in the biomedical field. Organic hydrogels are composed of an organic network cross-linked via chemical or physical reticulation nodes. In contrast, hybrid hydrogels are defined by the coexistence of organic and inorganic moieties in water. Inorganic polymerization, i.e. the sol–gel process, is one of the main techniques leading to hybrid hydrogels. The chemoselectivity of this method proceeds through hydrolysis and condensation reactions of metal oxide moieties. In addition, the mild reaction conditions make this process very promising for the preparation of water-containing materials and their bio-applications.

Heteromultivalent targeting of integrin αvβ3 and neuropilin 1 promotes cell survival via the activation of the IGF-1/insulin receptors

Posted by Lubomir Vezenkov on

Biomaterials 2018 Feb;155:64-79. doi: 10.1016/j.biomaterials.2017.10.042. Epub 2017 Oct 29.

Jia T, Choi J, Ciccione J, Henry M, Mehdi A, Martinez J, Eymin B, Subra G, Coll JL.

Abstract

Angiogenesis strongly depends on the activation of integrins, especially integrin αvβ3, and of neuropilin-1 (NRP-1), a co-receptor of VEGFR2. Dual-targeted molecules that simultaneously block both of them are expected have increased anti-angiogenic and antitumor activity. Toward this goal, we generated bifunctional 40 nm-sized silica nanoparticles (NPs) coated with controlled amounts of cRGD and ATWLPPR peptides and studied their affinity, selectivity and biological activity in HUVECs. Sub-nanomolar concentrations of NPs grafted either with ATWLPPR alone or in combination with cRGD exhibit potent and specific antagonist activity against VEGFR2/AKT signaling. However, a 1 nM concentration of the cRGD/ATWLPPR-heteromultivalent particles (RGD/ATW-NPs) also blocks the phosphorylation of VEGFR2 while co-inducing an unexpected long-lasting activation of AKT via IGF-1R/IR-AKT/GSK3β/eNOS signaling that stimulates cell survival and abrogates the intrinsic toxicity of silica-NPs to serum-starved HUVECs. We also showed that their repeated intravenous administration was associated with the proliferation of human U87MG tumor cells engrafted in nude mice and a dilatation of the tumor blood vessels. We present biochemical evidence for the complex cross-talk generated by the binding of the heteromultivalent NPs with αvβ3-integrin and with NRP1. In particular, we show for the first time that such heteromultivalent NPs can trans-activate IGF-1/insulin receptors and exert dose-dependent pro-survival activity. This study demonstrates the difficulties in designing targeted silica-based NPs for antiangiogenic therapies and the possible risks posed by undesirable side effects.

Ribbon-like Foldamers for Cellular Uptake and Drug Delivery

Posted by Lubomir Vezenkov on

Chembiochem 2017 Nov 2;18(21):2110-2114. doi: 10.1002/cbic.201700455. Epub 2017 Sep 22.

Vezenkov LL, Martin V, Bettache N, Simon M, Messerschmitt A, Legrand B, Bantignies JL, Subra G, Maynadier M, Bellet V, Garcia M, Martinez J, Amblard M.

Abstract

Different intracellular delivery systems of bioactive compounds have been developed, including cell-penetrating peptides. Although usually nontoxic and biocompatible, these vectors share some of the general drawbacks of peptides, notably low bioavailability and susceptibility to protease degradation, that limit their use. Herein, the conversion of short peptide sequences into poly-α-amino-γ-lactam foldamers that adopt a ribbon-like structure is investigated. This template is used to distribute critical cationic and/or hydrophobic groups on both sides of the backbone, leading to potent short, cell-permeable foldamers with a low positive-charge content. The lead compound showed dramatically improved protease resistance and was able to efficiently deliver a biologically relevant cargo inside cells. This study provided a simple strategy to convert short peptide sequences into efficient protease-resistant cell-penetrating foldamers.

Microgels of silylated HPMC as a multimodal system for drug co-encapsulation

Posted by Lubomir Vezenkov on

Int J Pharm. 2017 Nov 5;532(2):790-801. doi: 10.1016/j.ijpharm.2017.07.074. Epub 2017 Jul 27.

Zayed M, Tourne-Peteilh C, Ramonda M, Rethore G, Weiss P, Martinez J, Subra G, Mehdi A, Devoisselle JM, Legrand P.

Abstract

Combined therapy is a global strategy developed to prevent drug resistance in cancer and infectious diseases. In this field, there is a need of multifunctional drug delivery systems able to co-encapsulate small drug molecules, peptides, proteins, associated to targeting functions, nanoparticles. Silylated hydrogels are alkoxysilane hybrid polymers that can be engaged in a sol-gel process, providing chemical cross linking in physiological conditions, and functionalized biocompatible hybrid materials. In the present work, microgels were prepared with silylated (hydroxypropyl)methyl cellulose (Si-HPMC) that was chemically cross linked in soft conditions of pH and temperature. They were prepared by an emulsion templating process, water in oil (W/O), as microreactors where the condensation reaction took place. The ability to functionalize the microgels, so-called FMGs, in a one-pot process, was evaluated by grafting a silylated hydrophilic model drug, fluorescein (Si-Fluor), using the same reaction of condensation. Biphasic microgels (BPMGs) were prepared to evaluate their potential to encapsulate lipophilic model drug (Nile red). They were composed of two separate compartments, one oily phase (sesame oil) trapped in the cross linked Si-HPMC hydrophilic phase. The FMGs and BPMGs were characterized by different microscopic techniques (optic, epi-fluorescence, Confocal Laser Scanning Microscopy and scanning electronic microscopy), the mechanical properties were monitored using nano indentation by Atomic Force Microscopy (AFM), and different preliminary tests were performed to evaluate their chemical and physical stability. Finally, it was demonstrated that it is possible to co-encapsulate both hydrophilic and hydrophobic drugs, in silylated microgels, that were physically and chemically stable. They were obtained by chemical cross linking in soft conditions, and without surfactant addition during the emulsification process. The amount of drug loaded was in favor of further biological activity. Mechanical stimulations should be necessary to trigger drug release.

Sol-gel synthesis of collagen-inspired peptide hydrogel

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 Materials Today , Pages: Ahead of Print, Journal, 2017,  DOI: 10.1016/j.mattod.2017.02.001

C. Echalier, S. Jebors, G. Laconde, B. Guillaume, V. Luc, C. Pascal, B. Lea, A. Bethry, B. Legrand, H. Van Den Berghe, X. Garric, D. Noel, J. Martinez, A. Mehdi, G. Subra

Abstract

Conceiving biomaterials able to mimic the specific environments of extracellular matrixes are a prerequisite for tissue engineering applications. Numerous types of polymers (PEG, PLA, etc.) have been used for the design of biocompatible scaffolds, but they are still less efficient than natural biopolymers such as collagen exts. Chem. modified and loaded with different bioactive factors, biopolymers afford an environment favorable to cell proliferation and differentiation. Unfortunately, they present several drawbacks, such as weak batch-to-batch reproducibility, potential immunogenicity and high cost of prodn. Herein we propose a fully synthetic covalent hydrogel obtained by sol-gel polymn. of a silylated peptide. We selected a short and low mol. building-block derived from the consensus collagen sequence [Pro-Hyp-Gly]. Interestingly, the sol-gel process occurs in physiol. buffer, enabling the embedment of stem cells. This collagen-inspired hydrogel provides a cell-friendly environment comparable to natural collagen substrates, demonstrating its potency as a biomimetic scaffold.

-Modular bioink for 3D printing of biocompatible hydrogels: sol-gel polymerization of hybrid peptides and polymers

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RSC Advances, 2017, Volume: 7, Issue: 20, Pages: 12231-12235, DOI: 10.1039/C6RA28540F

C. Echalier, R. Levato, M. A. Mateos-Timoneda, O. Castano, S. Dejean, X. Garric, C. Pinese, D. Noel, E. Engel, J. Martinez, A. Mehdi, G.Subra

RCS materials

Abstract

An unprecedented generic system allowing the 3D printing of peptide-functionalized hydrogels by soft sol-gel inorg. polymn. is presented. Hybrid silylated inorg./bioorg. blocks are mixed in biol. buffer in an appropriate ratio, to yield a multicomponent bioink that can be printed as a hydrogel without using any photochem. or org. reagent. Hydrolysis and condensation of the silylated precursors occur during the printing process and result in a covalent network in which mols. are linked through siloxane bonds. The viscosity of the colloidal soln. used as bioink was monitored in order to set up the optimal conditions for extrusion printing. Grid-patterned hydrogel scaffolds contg. a hybrid integrin ligand were printed using a pressure-driven rapid prototyping machine. Finally, they were seeded with mesenchymal stem cells, demonstrating their suitability for cell culture. The versatility of the sol-gel process and its biocompatibility makes this approach highly promising for the prepn. of tailor-made cell-laden scaffolds.

Continuous flow ring-closing metathesis, an environmentally-friendly route to 2,5-dihydro-1H-pyrrole-3-carboxylates

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Green Chemistry, Pages: Ahead of Print

M. Drop, X. Bantreil, K. Grychowska, G.U. Mahoro, E. Colacino, M. Pawlowski, J. Martinez, G. Subra, P. Zajdel, F. Lamaty

Astract

2,5-Dihydro-1H-pyrrole-3-carboxylates are important building blocks for the synthesis of high value pyrroles and pyrroloquinoline derivs. with interesting biol. activities. The use of continuous flow allowed us to perform a key synthetic step, namely ruthenium-catalyzed ring-closing metathesis, with a residence time of 1 min at 120 °C. Di-Me carbonate, a green solvent, was demonstrated for the first time to be an excellent solvent for this reaction in continuous flow. The continuous flow conditions proved to be general and the scale-up of this reaction was not only possible, but also highly efficient. Conversion of 10 g of diene was realized in 37 min under continuous flow, yielding the desired heterocycle in 91% yield.

Unambiguous and Controlled One-Pot Synthesis of Multifunctional Silica Nanoparticles

Posted by Lubomir Vezenkov on

Chemistry of Materials, 2016, Volume: 28, Issue: 3, Pages: 885-889, DOI: 10.1021/acs.chemmater.5b04398

J. Ciccione, T. Jia, J .L. Coll, K. Parra, M. Amblard, S. Jebors, J. Martinez, A. Mehdi, G. Subra 

Abstract

A method for obtaining in a single step well-defined tunable multifunctional fluorescent particles having their surface functionalized with multiple covalently linked ligands is reported.  The strategy relies on the synthesis of hybrid bioorg.-inorg. peptide ligands, greatly simplifying the design of multifunctional nanoparticles.  It was possible to tune the ratio of two grafted ligands on the surface of the SiNPs simply by adjusting the relative concn. of hybrid species in the starting soln.  An original fluorine NMR method was applied to the dissolved SiNPs to demonstrate our hypothesis.

A switchable stapled peptide

Posted by Lubomir Vezenkov on

Journal of Peptide Science, 2016, Volume: 22, Issue: 3, Pages: 143-148, DOI: 10.1002/psc.2851

A. Kalistratova, B. Legrand, P. Verdie, E. Naydenova, M. Amblard, J. Martinez, G. Subra

Abstract

The O-N acyl transfer reaction has gained significant popularity in peptide and medicinal chem.  This reaction has been successfully applied to the synthesis of difficult sequence-contg. peptides, cyclic peptides, epimerization-free fragment coupling and more recently, to switchable peptide polymers.  Herein, we describe a related strategy to facilitate the synthesis and purifn. of a hydrophobic stapled peptide.  The staple consists of a serine linked through an amide bond formed from its carboxylic acid function and the side chain amino group of diaminopropionic acid and through an ester bond formed from its amino group and the side chain carboxylic acid function of aspartic acid.  The α-amino group of serine was protonated during purifn.  Interestingly, when the peptide was placed at physiol. pH, the free amino group initiated the O-N shift reducing the staple length by one atom, leading to a more hydrophobic stapled peptide.

Easy Synthesis of Tunable Hybrid Bioactive Hydrogels

Posted by Lubomir Vezenkov on

Chemistry of Materials, 2016, Volume: 28, Issue: 5, Pages: 1261-1265,  DOI: 10.1021/acs.chemmater.5b04881

C. Echalier, C. Pinese, X. Garric, H. Van Den Berghe, E. Jumas Bilak, J. Martinez, A. Mehdi, G. Subra 

Abstract

Hydrogels are raising an increasing interest in the biomedical field and have found applications in tissue engineering and regenerative medicine.  In order to mimic the complexity of natural tissues, functionalization of hydrogels with bioactive mols. is of first importance.  In this context, we developed a bottom-up approach based on the synthesis of hybrid silylated blocks that can be combined to obtain covalently functionalized gels.  In this study, hybrid silylated PEG and hybrid silylated bioactive peptides were synthesized and mixed in desired ratio before being simply dissolved in phosphate buff-er at physiol. pH to form a gel.  The soln. turns quickly into a covalent functional gel at 37 °C.  Mech. properties of these hydrogels were studied and their biocompatibility was demonstrated.  Depending on the type of bioactive peptides introduced within the gels, they exhibited either antibacterial or cell adhesion properties demonstrating the potency of this sol-gel modular strategy for fine tuning of gel properties.