A bioinspired approach for the modulation of electroosmotic flow and protein-surface interactions in capillary electrophoresis using silylated amino-amides blocks and covalent grafting

We explore a bioinspired approach to design tailored functionalized capillary electrophoresis (CE) surfaces based on covalent grafting for biomolecules analysis. First, the approach aims to overcome well-known common obstacles in CE protein analysis affecting considerably the CE performance (asymmetry, resolution, and repeatability) such as the unspecific adsorption on fused silica surface and the lack of control of electroosmotic flow (EOF). Then, our approach, which relies on new amino-amide mimic hybrid precursors synthesized by silylation of amino-amides (Si-AA) derivatives with 3-isocyanatopropyltriethoxysilane, aims to recapitulate the diversity of protein-protein interactions (π-π stacking, ionic, Van der Waals…) found in physiological condition (bioinspired approach) to improve the performance of CE protein analysis (electrochromatography). As a proof of concept, these silylated Si-AA (tyrosinamide silylation, serinamide silylation, argininamide silylation, leucinamide silylation, and isoglutamine silylation acid) have been covalently grafted in physiological conditions in different amount on bare fused silica capillary giving rise to a biomimetic coating and allowing both the modulation of EOF and protein-surface interactions. The analytical performances of amino-amide functionalized capillaries were assessed using lysozyme, cytochrome C and ribonuclease A and compared to traditional capillary coatings poly(ethylene oxide), poly(diallyldimethylammonium chloride), and sodium poly(styrenesulfonate). EOF, protein adsorption rate, protein retention factor k, and selectivity were determined for each coating. All results obtained showed this approach allowed to modulate the EOF, reduce unspecific adsorption, and generate specific interactions with proteins by varying the nature and the amount of Si-AA in the functionalization mixture.

One-Pot Synthesis of Bioinspired Peptide-Decorated Apatite Nanoparticles for Nanomedicine

Hybrid organic-inorganic bio-inspired apatite nanoparticles (NPs) are attractive for biomedical applications and especially in nanomedicine. Unfortunately, their applications in nanomedicine are limited by their broad particle size distributions and uncontrolled drug loading due to their multistep synthesis process.  Besides, very few attempts at exposing bioactive peptides on apatite NPs are made. In this work, an original one-pot synthesis of well-defined bioactive hybrid NPs composed of a mineral core of bioinspired apatite surrounded by an organic corona of bioactive peptides is reported. Dual stabilizing-bioactive agents, phosphonated polyethylene glycol-peptide conjugates, are prepared and directly used during apatite precipitation i) to form the organic corona during apatite precipitation, driving the size and shape of resulting hybrid NPs with colloidal stabilization and ii) to expose peptide moieties (RGD or YIGSR sequences) at the NPs periphery in view of conferring additional surface properties to enhance their interaction with cells. Here, the success of this approach is demonstrated, the functionalized NPs are fully characterized by Fourier-transform infrared, Raman, X-ray diffraction, solid and liquid state NMR, transmission electron microscopy, and dynamic light scattering, and their interaction with fibroblast cells is followed, unveiling a synergistic proliferative effect.

Superiority of the Triple-Acting 5-HT6R/5-HT3R Antagonist and MAO-B Reversible Inhibitor over 5-HT6R Antagonist Intepirdine in Alleviation of Cognitive Deficits in Rats

The multifactorial origin and neurochemistry of Alzheimer's disease (AD) call for the development of multitarget treatment strategies. We report a first-in-class triple acting compound that targets serotonin type 6 and 3 receptors (5-HT-Rs) and monoamine oxidase type B (MAO-B) as an approach for treating AD. The key structural features required for MAO-B inhibition and 5-HT6R antagonism and interaction with 5-HT3R were determined using molecular dynamic simulations and cryo-electron microscopy, respectively. Bioavailable PZ-1922 reversed scopolamine-induced cognitive deficits in the novel object recognition test. Furthermore, it displayed superior pro-cognitive properties compared to intepirdine (a 5-HT6R antagonist) in the AD model, which involved intracerebroventricular injection of an oligomeric solution of amyloid-β peptide (oAβ) in the T-maze test in rats. PZ-1922, but not intepirdine, restored levels of biomarkers characteristic of the debilitating effects of oAβ. These data support the potential of a multitarget approach involving the joint modulation of 5-HT6R/5-HT3R/MAO-B in AD.

Development of hybrid bioactive nanofibers composed of star Poly(lactic acid) and gelatin by sol-gel crosslinking during the electrospinning process

The design of a biomimetic scaffold is a major challenge in tissue engineering to promote tissue reconstruction. The use of synthetic polymer nanofibers is widely described as they provide biocompatible matrices whose topography mimics natural extracellular matrix (ECM). To closely match the biochemical composition of the ECM, bioactive molecules such as gelatin are added to the nanofibers to enhance cell adhesion and proliferation. To overcome the rapid solubilization of gelatin in biological fluids and to allow a lasting biological effect, the covalent crosslinking of this macromolecule in the network is crucial. The sol-gel route offers the possibility of gentle crosslinking during shaping but is rarely combined with electrospinning. In this study, we present the creation of Poly(lactic acid)/Gelatin hybrid nanofibers by sol-gel route during electrospinning. To enable sol-gel crosslinking, we synthesized star-shaped PLA and functionalized it with silane groups; then we functionalized gelatin with the same groups for their subsequent reaction with the polymer and thus the creation of the hybrid nanonetwork. We evaluated the impact of the presence of gelatin in Poly(lactic acid)/Gelatin hybrid nanofibers at different percentages on the mechanical properties, nanonetwork crosslinking, degradation and biological properties of the hybrid nanofibers. The addition of gelatin modulated nanonetwork crosslinking that impacted the stiffness of the nanofibers, resulting in softer materials for the cells. Moreover, these hybrid nanofibers also showed a significant improvement in fibroblast proliferation and present a degradation rate suitable for tissue reconstruction. Finally, the bioactive hybrid nanofibers possess versatile properties, interesting for various potential applications in tissue reconstruction.

Gelatin modified with alkoxysilanes (GelmSi) forms hybrid hydrogels for bioengineering applications

Biopolymers are ideal candidates for the development of hydrogels for tissue engineering applications. However, chemical modifications are required to further improve their mechanical properties, in particular to cross-link them for long-lasting applications or biofabrication. Herein, we developed a novel gelatin-based hydrogel precursor, "GelmSi" which consist on modified gelatin with triethoxysilyl groups. Gelatin was chosen as starting material because of its biocompatibility and bioactivity, favouring cell adhesion and migration. Alkoxysilane moieties were introduced in a controlled manner on the lysine side chains of gelatin to obtain a hybrid precursor which reacts in physiological conditions, forming covalent siloxane bonds and allowing the formation of a three-dimensional chemical network. On the contrary to unmodified gelatin, siloxane covalent network dramatically increases the stiffness and the thermal stability of the resulting gelatin-based hydrogel, making it suitable for cell encapsulation and cell culture. The biorthogonality and versatility of the GelmSi hybrid hydrogel unlock a broad range of gelatin-based bioengineering applications.

3D high-precision melt electro written polycaprolactone modified with yeast derived peptides for wound healing

In this study melt electro written (MEW) scaffolds of poly(ε-caprolactone) PCL are decorated with anti-inflammatory yeast-derived peptide for skin wound healing. Initially, 13 different yeast-derived peptides were screened and analyzed using both in vitro and in vivo assays. The MEW scaffolds are functionalized with the selected peptide VLSTSFPPW (VW-9) with the highest activity in reducing pro-inflammatory cytokines and stimulating fibroblast proliferation, migration, and collagen production. The peptide was conjugated to the MEW scaffolds using carbodiimide (CDI) and thiol chemistry, with and without plasma treatment, as well as by directly mixing the peptide with the polymer before printing. The MEW scaffolds modified using CDI and thiol chemistry with plasma treatment showed improved fibroblast and macrophage penetration and adhesion, as well as increased cell proliferation and superior anti-inflammatory properties, compared to the other groups. When applied to full-thickness excisional wounds in rats, the peptide-modified MEW scaffold significantly enhanced the healing process compared to controls (p < 0.05). This study provides proof of concept for using yeast-derived peptides to functionalize biomaterials for skin wound healing.

Amelogenin-Derived Peptide (ADP-5) Hydrogel for Periodontal Regeneration: An In Vitro Study on Periodontal Cells Cytocompatibility, Remineralization and Inflammatory Profile

A relevant alternative to enamel matrix derivatives from animal origin could be the use of synthetic amelogenin-derived peptides. This study aimed to assess the effect of a synthetic amelogenin-derived peptide (ADP-5), alone or included in an experimental gellan-xanthan hydrogel, on periodontal cell behavior (gingival fibroblasts, periodontal ligament cells, osteoblasts and cementoblasts). The effect of ADP-5 (50, 100, and 200 µg/mL) on cell metabolic activity was examined using Alamar blue assay, and cell morphology was assessed by confocal imaging. An experimental gellan-xanthan hydrogel was then designed as carrier for ADP-5 and compared to the commercial gel Emdogain^®. Alizarin Red was used to determine the periodontal ligament and cementoblasts cell mineralization. The inflammatory profile of these two cells was also quantified using ELISA (vascular endothelial growth factor A, tumor necrosis factor α, and interleukin 11) mediators. ADP-5 enhanced cell proliferation and remineralization; the 100 µg/mL concentration was more efficient than 50 and 200 µg/mL. The ADP-5 experimental hydrogel exhibited equivalent good biological behavior compared to Emdogain^® in terms of cell colonization, mineralization, and inflammatory profile. These findings revealed relevant insights regarding the ADP-5 biological behavior. From a clinical perspective, these outcomes could instigate the development of novel functionalized scaffold for periodontal regeneration.

Morphological evolution of poly(glycerol monomethacrylate)-stat-glycine–phenylalanine–phenylalanine–methacrylamide-b-poly(2-hydroxypropylmethacrylate) (P(GMA-stat-(MAm-GFF))-b-PHPMA) block copolymer nano-objects via polymerization-induced self-assembly

Here we report a study on the reversible addition–fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) of self-assembling peptide-containing diblock copolymers.

Silylated biomolecules: Versatile components for bioinks

Physical hydrogels prepared from natural biopolymers are the most popular components for bioinks. However, to improve the mechanical properties of the network, in particular its durability for long-lasting tissue engineering applications or its stiffness for bone/cartilage applications, covalent chemical hydrogels have to be considered. For that purpose, biorthogonal reactions are required to allow the inclusion of living cells within the bioink reservoir before the 3D printing procedure. Interestingly, such reactions also unlock the possibility to further multifunctionalize the network, adding bioactive moieties to tune the biological properties of the resulting printed biomaterial. Surprisingly, compared to the huge number of studies disclosing novel bioink compositions, no extensive efforts have been made by the scientific community to develop new chemical reactions meeting the requirements of both cell encapsulation, chemical orthogonality and versatile enough to be applied to a wide range of molecular components, including fragile biomolecules. That could be explained by the domination of acrylate photocrosslinking in the bioprinting field. On the other hand, proceeding chemoselectively and allowing the polymerization of any type of silylated molecules, the sol-gel inorganic polymerization was used as a crosslinking reaction to prepare hydrogels. Recent development of this strategy includes the optimization of biocompatible catalytic conditions and the silylation of highly attractive biomolecules such as amino acids, bioactive peptides, proteins and oligosaccharides. When one combines the simplicity and the versatility of the process, with the ease of functionalization of any type of relevant silylated molecules that can be combined in an infinite manner, it was obvious that a family of bioinks could emerge quickly. This review presents the sol-gel process in biocompatible conditions and the various classes of relevant silylated molecules that can be used as bioink components. The preparation of hydrogels and the kinetic considerations of the sol-gel chemistry which at least allowed cell encapsulation and extrusion-based bioprinting are discussed.

Structure-Based Design and Optimization of FPPQ, a Dual-Acting 5-HT3 and 5-HT6 Receptor Antagonist with Antipsychotic and Procognitive Properties

In line with recent clinical trials demonstrating that ondansetron, a 5-HT₃ receptor (5-HT₃R) antagonist, ameliorates cognitive deficits of schizophrenia and the known procognitive effects of 5-HT₆ receptor (5-HT₆R) antagonists, we applied the hybridization strategy to design dual-acting 5-HT₃/5-HT₆R antagonists. We identified the first-in-class compound FPPQ, which behaves as a 5-HT₃R antagonist and a neutral antagonist 5-HT₆R of the Gs pathway. FPPQ shows selectivity over 87 targets and decent brain penetration. Likewise, FPPQ inhibits phencyclidine (PCP)-induced hyperactivity and displays procognitive properties in the novel object recognition task. In contrast to FPPQ, neither 5-HT₆R inverse agonist SB399885 nor neutral 5-HT₆R antagonist CPPQ reversed (PCP)-induced hyperactivity. Thus, combination of 5-HT₃R antagonism and 5-HT₆R antagonism, exemplified by FPPQ, contributes to alleviating the positive-like symptoms. Present findings reveal critical structural features useful in a rational polypharmacological approach to target 5-HT₃/5-HT₆ receptors and encourage further studies on dual-acting 5-HT₃/5-HT₆R antagonists for the treatment of psychiatric disorders.

Neuropathic pain-alleviating activity of novel 5-HT6 receptor inverse agonists derived from 2-aryl-1H-pyrrole-3-carboxamide

The diverse signaling pathways engaged by serotonin type 6 receptor (5-HT₆R) together with its high constitutive activity suggests different types of pharmacological interventions for the treatment of CNS disorders. Non-physiological activation of mTOR kinase by constitutively active 5-HT₆R under neuropathic pain conditions focused our attention on the possible repurposing of 5-HT₆R inverse agonists as a strategy to treat painful symptoms associated with neuropathies of different etiologies. Herein, we report the identification of compound 33 derived from the library of 2-aryl-1H-pyrrole-3-carboxamides as a potential analgesic agent. Compound 33 behaves as a potent 5-HT₆R inverse agonist at Gs, Cdk5, and mTOR signaling. Preliminary ADME/Tox studies revealed preferential distribution of 33 to the CNS and placed it in the low-risk safety space. Finally, compound 33 dose-dependently reduced tactile allodynia in spinal nerve ligation (SNL)-induced neuropathic rats.

2-Phenyl-1H-pyrrole-3-carboxamide as a New Scaffold for Developing 5-HT6 Receptor Inverse Agonists with Cognition-Enhancing Activity

Serotonin type 6 receptor (5-HT₆R) has gained particular interest as a promising target for treating cognitive deficits, given the positive effects of its antagonists in a wide range of memory impairment paradigms. Herein, we report on degradation of the 1H-pyrrolo[3,2-c]quinoline scaffold to provide the 2-phenyl-1H-pyrrole-3-carboxamide, which is devoid of canonical indole-like skeleton and retains recognition of 5-HT₆R. This modification has changed the compound’s activity at 5-HT₆R-operated signaling pathways from neutral antagonism to inverse agonism. The study identified compound 27 that behaves as an inverse agonist of the 5-HT₆R at the Gs and Cdk5 signaling pathways. Compound 27 showed high selectivity and metabolic stability and was brain penetrant. Finally, 27 reversed scopolamine-induced memory decline in the novel object recognition test and exhibited procognitive properties in the attentional set-shifting task in rats. In light of these findings, 27 might be considered for further evaluation as a new cognition-enhancing agent, while 2-phenyl-1H-pyrrole-3-carboxamide might be used as a template for designing 5-HT₆R inverse agonists.

Sol-gel process: the inorganic approach in protein imprinting

Proteins play a central role in the signal transmission in living systems since they are able to recognize specific biomolecules acting as cellular receptors, antibodies or enzymes, being themselves recognized by other proteins in protein/protein interactions, or displaying epitopes suitable for antibody binding. In this context, the specific recognition of a given protein unlocks a range of interesting applications in diagnosis and in targeted therapies. Obviously, this role is already fulfilled by antibodies with unquestionable success. However, the design of synthetic artificial systems able to endorse this role is still challenging with a special interest to overcome limitations of antibodies, in particular their production and their stability. Molecular Imprinted Polymers (MIPs) are attractive recognition systems which could be an alternative for the specific capture of proteins in complex biological fluids. MIPs can be considered as biomimetic receptors or antibody mimics displaying artificial paratopes. However, MIPs of proteins remains a challenge due to their large size and conformational flexibility, their complex chemical nature with multiple recognition sites and their low solubility in most organic solvents. Classical MIP synthesis conditions result in large polymeric cavities and unspecific binding sites on the surface. In this review, the potential of the sol-gel process as inorganic polymerization strategy to overcome the drawbacks of protein imprinting is highlighted. Thanks to the mild and biocompatible experimental conditions required and the use of water as a solvent, the inorganic polymerization approach better suited to proteins than organic polymerization. Through numerous examples and applications of MIPs, we proposed a critical evaluation of the parameters that must be carefully controlled to achieve sol-gel protein imprinting (SGPI), including the choice of the monomers taking part in the polymerization.

Nano-assemblies with core-forming hydrophobic polypeptide via polymerization-induced self-assembly (PISA)

The aim of this study is to produce self-assembled structures with hydrophobic polypeptide cores via Reversible Addition–Fragmentation chain Transfer (RAFT) – mediated Polymerisation-Induced Self-Assembly (PISA).

Encapsulation of BSA in hybrid PEG hydrogels: stability and controlled release

Hybrid hydrogels based on silylated polyethylene glycol, Si-PEG, were evaluated as hybrid matrices able to trap, stabilize and release bovine serum albumin (BSA) in a controlled manner. Parameters of the inorganic condensation reaction leading to a siloxane (Si–O–Si) three dimensional network were carefully investigated, in particular the temperature, the surrounding hygrometry and the Si-PEG concentration. The resulting hydrogel structural features affected the stability, swelling, and mechanical properties of the network, leading to different protein release profiles. Elongated polymer assemblies were observed, the length of which ranged from 150 nm to over 5 μm. The length could be correlated to the Si–O–Si condensation rate from 60% (hydrogels obtained at 24 °C) to about 90% (xerogels obtained at 24 °C), respectively. Consequently, the controlled release of BSA could be achieved from hours to several weeks, with respect to the fibers' length and the condensation rate. The protein stability was evaluated by means of a thermal study. The main results gave insight into the biomolecule structure preservation during polymerisation, with ΔG < 0 for encapsulated BSA in any conditions, below the melting temperature (65 °C).

Silylated hybrid hydrogels of polyethylene glycol were designed to trap, stabilize and release a model protein (bovine serum albumin). Fine-tuning sol–gel reactions lead to sustained release of BSA over weeks, with good insight of protein stability.

Direct Synthesis of Peptide-Containing Silicones: A New Way to Bioactive Materials

A simple and efficient way to synthesize peptide-containing silicone materials is described. Silicone oils containing a chosen ratio of bioactive peptide sequences were prepared by acid-catalyzed copolymerization of dichlorodimethylsilane, hybrid dichloromethyl peptidosilane, and Si(vinyl)- or SiH-functionalized monomers. Functionalized silicone oils were first obtained and then, after hydrosilylation cross-linking, bioactive polydimethylsiloxane (PDMS)-based materials were straightforwardly obtained. The introduction of an antibacterial peptide yielded PDMS materials showing activity against Staphylococcus aureus. PDMS containing RGD ligands showed improved cell-adhesion properties. This generic method was fully compatible with the stability of peptides and thus opened the way to the synthesis of a wide range of biologically active silicones.

Inorganic Sol-Gel Polymerization for Hydrogel Bioprinting

An inorganic sol-gel polymerization process was used as a cross-linking reaction during three-dimensional (3D) bioprinting of cell-containing hydrogel scaffolds. Hybrid hydroxypropyl methyl cellulose (HPMC), with a controlled ratio of silylation, was prepared and isolated as a 3D-network precursor. When dissolved in a biological buffer containing human mesenchymal stem cells, it yields a bioink that can be printed during polymerization by extrusion. It is worth noting that the sol-gel process proceeded at pH 7.4 using biocompatible mode of catalysis (NaF and glycine). The printing window was determined by rheology and viscosity measurements. The physicochemical properties of hydrogels were studied. Covalent functionalization of the network can be easily performed by adding a triethoxysilyl-containing molecule; a fluorescent hybrid molecule was used as a proof of concept.

Real-time shear wave ultrasound elastography: a new tool for the evaluation of diaphragm and limb muscle stiffness in critically ill patients

BACKGROUND

Muscle weakness following critical illness is the consequence of loss of muscle mass and alteration of muscle quality. It is associated with long-term disability. Ultrasonography is a reliable tool to quantify muscle mass, but studies that evaluate muscle quality at the critically ill bedside are lacking. Shear wave ultrasound elastography (SWE) provides spatial representation of soft tissue stiffness and measures of muscle quality. The reliability and reproducibility of SWE in critically ill patients has never been evaluated.

METHODS

Two operators tested in healthy controls and in critically ill patients the intra- and inter-operator reliability of the SWE using transversal and longitudinal views of the diaphragm and limb muscles. Reliability was calculated using the intra-class correlation coefficient and a bootstrap sampling method assessed their consistency.

RESULTS

We collected 560 images. Longitudinal views of the diaphragm (ICC 0.83 [0.50-0.94]), the biceps brachii (ICC 0.88 [0.67-0.96]) and the rectus femoris (ICC 0.76 [0.34-0.91]) were the most reliable views in a training set of healthy controls. Intra-class correlation coefficient for inter-operator reproducibility and intra-operator reliability was above 0.9 for all muscles in a validation set of healthy controls. In critically ill patients, inter-operator reproducibility and intra-operator 1 and 2 reliability ICCs were respectively 0.92 [0.71-0.98], 0.93 [0.82-0.98] and 0.92 [0.81-0.98] for the diaphragm; 0.96 [0.86-0.99], 0.98 [0.94-0.99] and 0.99 [0.96-1] for the biceps brachii and 0.91 [0.51-0.98], 0.97 [0.93-0.99] and 0.99 [0.97-1] for the rectus femoris. The probability to reach intra-class correlation coefficient greater than 0.8 in a 10,000 bootstrap sampling for inter-operator reproducibility was respectively 81%, 84% and 78% for the diaphragm, the biceps brachii and the rectus femoris respectively.

CONCLUSIONS

SWE is a reliable technique to evaluate limb muscles and the diaphragm in both healthy controls and in critically ill patients.

TRIAL REGISTRATION

The study was registered (ClinicalTrial NCT03550222).

Biocompatible Glycine-Assisted Catalysis of the Sol-Gel Process: Development of Cell-Embedded Hydrogels

The sol-gel process can be used for hydrogel cross-linking, thus opening an attractive route for the design of biocompatible hydrogels under soft conditions. The sol-gel process can be catalysed at basic or acidic pH values, under neutral conditions with the addition of a nucleophile. Therefore, working around pH 7 unlocks the possibility of direct cell embedment and the preparation of bioinks. We aimed to propose a generic method for sol-gel 3D bioprinting, and first screened different nucleophilic catalysts using bis-silylated polyethylene glycol (PEG) as a model hydrogel. A synergistic effect of glycine and NaF, used in low concentrations to avoid any toxicity, was observed. Biocompatibility of the approach was demonstrated by embedding primary mouse mesenchymal stem cells. The measure of viscosity as a function of time showed the impact of reaction parameters, such as temperature, complexity of the medium, pH and cell addition, on the kinetics of the sol-gel process, and allowed prediction of the gelation time.

The presence of PEG on nanoparticles presenting the c[RGDfK]- and/or ATWLPPR peptides deeply affects the RTKs-AKT-GSK3β-eNOS signaling pathway and endothelial cells survival

Covering the surface of a nanoparticle with polyethylene glycol (PEG) is a common way to prevent non-specific interactions but how its presence impacts on the activity of targeting ligands is still poorly documented. We synthesized a set of 9 silica nanoparticles grafted with c[RGDfK]-, a peptide targeting integrin α_vß₃ (cRGD)_, and/or with ATWLPPR, an anti-neuropilin 1 peptide (ATW). We then added various PEGs, and studied NPs binding on primary endothelial cells, the downstream activated signaling pathways and the impact on apoptosis. Our results show that the presence of PEG2000 on cRGD/ATW nanoparticles moderately improves cell binding but induces a 6000 times augmentation of AKT-dependent cell response due to the recruitment of other Receptor Tyrosine Kinases. Augmenting the length of the spacer that separates the peptides from the silica (using PEG3000) mainly resulted in a loss of specificity. Finally, the PEG-mediated hyperactivation of AKT did not protect endothelial cell from dying in the absence of serum, while its moderate activation obtained without PEG did. Finally, PEGylation of cRGD/ATW-NPs can generate nanoparticles with potent capacities to activate the AKT-GSK3β-eNOS cascade and to affect the resistance of endothelial cells to apoptosis. Thus, the impact of PEGylation should be precisely considered in order to avoid the apparition of counter-productive biological responses.

Combining sol–gel and microfluidics processes for the synthesis of protein-containing hybrid microgels

Biocompatible encapsulation of proteins in hybrid microgels of a silylated hydrogel, focused on soft procedures and cross-linking conditions.

Chemical insights into bioinks for 3D printing

Dedicated chemical strategies are required to form hydrogel networks from bioink components, allowing cell survival during 3D bioprinting processes.

Receptor-Ligand Interaction Measured by Inductively Coupled Plasma Mass Spectrometry and Selenium Labeling

In the search for an alternative strategy to the radioactivity measurement conventionally performed to probe receptor-ligand interactions in pharmacological assays, we demonstrated that selenium labeling of the studied ligand combined with elemental mass spectrometry was as efficient and robust as the reference method but devoid of its environmental and health hazards. The proof-of-concept was illustrated on two GPCR receptors, vasopressin (V_1A) and cholecystokinin B (CCK-B), involving peptides as endogenous ligands. We proposed several methodologies to produce selenium-labeled ligands according to peptide sequences along with binding affinity constraints. A selection of selenopeptides that kept high affinities toward the targeted receptor were engaged in saturation and competitive binding experiments with subsequent sensitive RP-LC-ICP-MS measurements. Experimental values of affinity constant ( K_i) were perfectly correlated to literature data, illustrating the general great potency of replacing radioactive iodine by selenium for ligand labeling to further undergo unaffected pharmacology experiments efficiently monitored by elemental mass spectrometry.

Inorganic polymerization: an attractive route to biocompatible hybrid hydrogels

The sol–gel process is one of the main techniques leading to hybrid hydrogels that can be used in a wide scope of applications, especially in the biomedical field.

Site-specific grafting on titanium surfaces with hybrid temporin antibacterial peptides

Controlled orientation of silylated hybrid-temporins on titanium surfaces improved antibacterial activity.

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

Angiogenesis strongly depends on the activation of integrins, especially integrin α_vβ₃, 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 α_vβ₃-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.

Peptide synthesis: ball-milling, in solution, or on solid support, what is the best strategy?

While presenting particularly interesting advantages, peptide synthesis by ball-milling was never compared to the two traditional strategies, namely peptide syntheses in solution and on solid support (solid-phase peptide synthesis, SPPS). In this study, the challenging VVIA tetrapeptide was synthesized by ball-milling, in solution, and on solid support. The three strategies were then compared in terms of yield, purity, reaction time and environmental impact. The results obtained enabled to draw some strengths and weaknesses of each strategy, and to foresee what will have to be implemented to build more efficient and sustainable peptide syntheses in the near future.

Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model

Melanoma is a highly metastatic and deadly form of cancer. Invasive melanoma cells overexpress integrin α_vβ₃, which is a well-known target for Arg-Gly-Asp-based (RGD) peptides. We developed a sophisticated method to synthetize milligram amounts of a targeted vector that allows the RGD-mediated targeting, internalization, and release of a mitochondria-disruptive peptide derived from the pro-apoptotic Bax protein. We found that 2.5 μM Bax[109-127] was sufficient to destabilize the mitochondria in ten different tumor cell lines, even in the presence of the anti-apoptotic Bcl2 protein, which is often involved in tumor resistance. This pore-forming peptide displayed antitumor activity when it was covalently linked by a disulfide bridge to the tetrameric RAFT-c[RGD]₄-platform and after intravenous injection in a human melanoma tumor model established in humanized immuno-competent mice. In addition to its direct toxic effect, treatment with this combination induced the release of the immuno-stimulating factor monocyte chimoattractant protein 1 (MCP1) in the blood and a decrease in the level of the pro-angiogenic factor FGF2. Our novel multifunctional, apoptosis-inducing agent could be further customized and assayed for potential use in tumor-targeted therapy.

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

Inorganic polymerization as a cross-linking method for 3D printing of PEG–peptide hydrogels.

Simple and Specific Grafting of Antibacterial Peptides on Silicone Catheters

To fight against nosocomial infection initiated by colonization of medical devices, a strategy enabling the direct and fast functionalization of silicone surfaces is proposed. This strategy proceeds in a site-specific way using original hybrid silylated antibacterial peptides. This safe and up-scalable method guarantees a covalent and robust immobilization with the correct orientation of the bioactive moiety. Importantly it also avoids multi-step chemical modifications of the surface or multi-layer polymer coatings. As proof of concept, antibacterial silicone catheter has been prepared whose immediate and long term efficiency is superior by comparison to similar silver-embedded materials.

Quantitative MALDI-MS Binding Assays: An Alternative to Radiolabeling

Radiolabeling of ligands is still the gold standard in the study of high-affinity receptor-ligand interactions. In an effort toward safer and simpler alternatives to the use of radioisotopes, we developed a quantitative and highly sensitive matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) method that relies on the use of chemically tagged ligands designed to be specifically detectable when present as traces in complex biological mixtures such as cellular lysates. This innovative technology allows easy, sensitive detection and accurate quantification of analytes at the sub-nanomolar level. After statistical validation, we were able to perform pharmacological evaluations of G protein-coupled receptor (V1A-R)-ligand interactions. Both saturation and competitive binding assays were successfully processed.

Selenazolidine: a selenium containing proline surrogate in peptide science

In the search for new peptide ligands containing selenium in their sequences, we investigated l-4-selenazolidine-carboxylic acid (selenazolidine, Sez) as a proline analog with the chalcogen atom in the γ-position of the ring. In contrast to proteinogenic selenocysteine (Sec) and selenomethionine (SeMet), the incorporation within a peptide sequence of such a non-natural amino acid has never been studied. There is thus a great interest in increasing the possibility of selenium insertion within peptides, especially for sequences that do not possess a sulfur containing amino acid (Cys or Met), by offering other selenated residues suitable for peptide synthesis protocols. Herein, we have evaluated selenazolidine in Boc/Bzl and Fmoc/tBu strategies through the synthesis of a model tripeptide, both in solution and on a solid support. Special attention was paid to the stability of the Sez residue in basic conditions. Thus, generic protocols have been optimized to synthesize Sez-containing peptides, through the use of an Fmoc-Xxx-Sez-OH dipeptide unit. As an example, a new analog of the vasopressin receptor-1A antagonist was prepared, in which Pro was replaced with Sez [3-(4-hydroxyphenyl)-propionyl-d-Tyr(Me)-Phe-Gln-Asn-Arg-Sez-Arg-NH2]. Both proline and such pseudo-proline containing peptides exhibited similar pharmacological properties and endopeptidase stabilities indicating that the presence of the selenium atom has minimal functional effects. Taking into account the straightforward handling of Sez as a dipeptide building block in a conventional Fmoc/tBu SPPS strategy, this result suggested a wide range of potential uses of the Sez amino acid in peptide chemistry, for instance as a viable proline surrogate as well as a selenium probe, complementary to Sec and SeMet, for NMR and mass spectrometry analytical purposes.

Novel 1H-Pyrrolo[3,2-c]quinoline Based 5-HT6 Receptor Antagonists with Potential Application for the Treatment of Cognitive Disorders Associated with Alzheimer's Disease

Modulators of the serotonin 5-HT6 receptor (5-HT6R) offer a promising strategy for the treatment of the cognitive deficits that are associated with dementia and Alzheimer's disease. Herein, we report the design, synthesis, and characterization of a novel class of 5-HT6R antagonists that is based on the 1H-pyrrolo[3,2-c]quinoline core. The most active compounds exhibited comparable binding affinity to the reference compound, SB-742457, and markedly improved selectivity. Lead optimization led to the identification of (S)-1-[(3-chlorophenyl)sulfonyl]-4-(pyrrolidine-3-yl-amino)-1H-pyrrolo[3,2-c]quinoline (14) (Ki = 3 nM and Kb = 0.41 nM). Pharmacological characterization of the 5-HT6R's constitutive activity at Gs signaling revealed that 14 behaved as a neutral antagonist, while SB-742457 was classified as an inverse agonist. Both compounds 14 and SB-742457 reversed phencyclidine-induced memory deficits and displayed distinct procognitive properties in cognitively unimpaired animals (3 mg/kg) in NOR tasks. Compounds 14 and SB-742457 were also active in the Vogel test, yet the anxiolytic effect of 14 was 2-fold higher (MED = 3 mg/kg). Moreover, 14 produced, in a 3-fold higher dose (MED = 10 mg/kg), antidepressant-like effects that were similar to those produced by SB-742457 (MED = 3 mg/kg). Together, these data suggest that the 4-(pyrrolidine-3-yl-amino)-1H-pyrrolo[3,2-c]quinoline scaffold is an attractive molecular framework for the development of procognitive agents. The results are promising enough to warrant further detailed mechanistic studies on the therapeutic potential of 5-HT6R antagonists and inverse agonists for the treatment of cognitive decline and depression/anxiety symptoms that are comorbidities of Alzheimer's disease.

Investigation of Elemental Mass Spectrometry in Pharmacology for Peptide Quantitation at Femtomolar Levels

In the search of new robust and environmental-friendly analytical methods able to answer quantitative issues in pharmacology, we explore liquid chromatography (LC) associated with elemental mass spectrometry (ICP-MS) to monitor peptides in such complex biological matrices. The novelty is to use mass spectrometry to replace radiolabelling and radioactivity measurements, which represent up-to now the gold standard to measure organic compound concentrations in life science. As a proof of concept, we choose the vasopressin (AVP)/V1A receptor system for model pharmacological assays. The capacity of ICP-MS to provide highly sensitive quantitation of metallic and hetero elements, whatever the sample medium, prompted us to investigate this technique in combination with appropriate labelling of the peptide of interest. Selenium, that is scarcely present in biological media, was selected as a good compromise between ICP-MS response, covalent tagging ability using conventional sulfur chemistry and peptide detection specificity. Applying selenium monitoring by elemental mass spectrometry in pharmacology is challenging due to the very high salt content and organic material complexity of the samples that produces polyatomic aggregates and thus potentially mass interferences with selenium detection. Hyphenation with a chromatographic separation was found compulsory. Noteworthy, we aimed to develop a straightforward quantitative protocol that can be performed in any laboratory equipped with a standard macrobore LC-ICP-MS system, in order to avoid time-consuming sample treatment or special implementation of instrumental set-up, while allowing efficient suppression of all mass interferences to reach the targeted sensitivity. Significantly, a quantification limit of 57 ng Se L^-1 (72 femtomoles of injected Se) was achieved, the samples issued from the pharmacological assays being directly introduced into the LC-ICP-MS system. The established method was successfully validated and applied to the measurement of the vasopressin ligand affinity for its V1A receptor through the determination of the dissociation constant (Kd) which was compared to the one recorded with conventional radioactivity assays.

The novel nonapeptide acein targets angiotensin converting enzyme in the brain and induces dopamine release

BACKGROUND AND PURPOSE

Using an in-house bioinformatics programme, we identified and synthesized a novel nonapeptide, H-Pro-Pro-Thr-Thr-Thr-Lys-Phe-Ala-Ala-OH. Here, we have studied its biological activity, in vitro and in vivo, and have identified its target in the brain.

EXPERIMENTAL APPROACH

The affinity of the peptide was characterized using purified whole brain and striatal membranes from guinea pigs and rats . Its effect on behaviour in rats following intra-striatal injection of the peptide was investigated. A photoaffinity UV cross-linking approach combined with subsequent affinity purification of the ligand covalently bound to its receptor allowed identification of its target.

KEY RESULTS

The peptide bound with high affinity to a single class of binding sites, specifically localized in the striatum and substantia nigra of brains from guinea pigs and rats. When injected within the striatum of rats, the peptide stimulated in vitro and in vivo dopamine release and induced dopamine-like motor effects. We purified the target of the peptide, a ~151 kDa protein that was identified by MS/MS as angiotensin converting enzyme (ACE I). Therefore, we decided to name the peptide acein.

CONCLUSION AND IMPLICATIONS

The synthetic nonapeptide acein interacted with high affinity with brain membrane-bound ACE. This interaction occurs at a different site from the active site involved in the well-known peptidase activity, without modifying the peptidase activity. Acein, in vitro and in vivo, significantly increased stimulated release of dopamine from the brain. These results suggest a more important role for brain ACE than initially suspected.

A switchable stapled peptide

The O-N acyl transfer reaction has gained significant popularity in peptide and medicinal chemistry. This reaction has been successfully applied to the synthesis of difficult sequence-containing 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 purification 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 purification. Interestingly, when the peptide was placed at physiological pH, the free amino group initiated the O-N shift reducing the staple length by one atom, leading to a more hydrophobic stapled peptide.

Selective homodimerization of unprotected peptides using hybrid hydroxydimethylsilane derivatives

A straightforward way to dimerize unprotected peptide sequences is presented; it relies on a chemoselective condensation of hybrid peptides bearing a hydroxydimethylsilyl group at a chosen position to generate siloxane bonds upon freeze-drying.

Engineered Adhesion Peptides for Improved Silicon Adsorption

Engineering peptides that present selective recognition and high affinity for a material is a major challenge for assembly-driven elaboration of complex systems with wide applications in the field of biomaterials, hard-tissue regeneration, and functional materials for therapeutics. Peptide-material interactions are of vital importance in natural processes but less exploited for the design of novel systems for practical applications because of our poor understanding of mechanisms underlying these interactions. Here, we present an approach based on the synthesis of several truncated peptides issued from a silicon-specific peptide recovered via phage display technology. We use the photonic response provided by porous silicon microcavities to evaluate the binding efficiency of 14 different peptide derivatives. We identify and engineer a short peptide sequence (SLVSHMQT), revealing the highest affinity for p(+)-Si. The molecular recognition behavior of the obtained peptide fragment can be revealed through mutations allowing identification of the preferential affinity of certain amino acids toward silicon. These results constitute an advance in both the engineering of peptides that reveal recognition properties for silicon and the understanding of biomolecule-material interactions.