Bertrand Czarny

Antibacterial coatings are needed to reduce surface contamination in clinical and textile environments, but many existing antimicrobial coatings rely on the release of biocides, creating concerns about toxicity and antimicrobial resistance, or require metal ions, harsh chemicals, and complex multi-step fabrication processes that limit practical deployment. In this study, six catechol aldehyde isomers were grafted onto bactericidal branched polyethylenimine (bPEI) using Schiff-base click chemistry to create one-component, metal-free coating solutions. Upon exposure to air and moisture, these solutions crosslinked into quinone-based networks that formed uniform films on cellulose substrates through simple dip-coating. Evaluation using colony-forming-unit counts, zone-of-inhibition assays, and ¹H NMR leachate analysis distinguished contact-killing activity from antibacterial effects caused by diffusion. All coatings exhibited low leaching, losing no more than 7.6% of their mass after aqueous exposure, while maintaining antibacterial performance after brief water and ethanol rinses. Notably, the bPEI-g-(3,5-DBA) formulation matched the strong contact-bactericidal activity of unmodified bPEI, achieving more than a three-log reduction in bacterial count. The results demonstrate that catechol substitution patterns can be used to control the balance between diffusible and surface-retained antibacterial activity, offering a versatile strategy for designing durable, wash-resistant, air-activated antibacterial coatings.

Despite advances in therapy for inflammatory bowel disease (IBD), current treatments are associated with poor clinical outcomes and systemic side effects. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have therapeutic potential in IBD due to their regenerative and immunomodulatory properties. However, most studies administer MSC-EVs by injection, which does not offer the significant benefits of oral administration, including direct and localized access to the site(s) of intestinal inflammation. Here, we evaluated the stability of MSC-EVs for oral delivery by assessing particle size, concentration, and EV markers. MSC-EVs disintegrated in gastrointestinal (GI) fluids, with cryogenic electron microscopy confirming the loss of structural integrity. To address this, we developed a double-coating formulation consisting of chitosan and Eudragit S100 to enhance GI stability and facilitate colon-targeted delivery. Coated EVs were resistant to GI fluids and digestive enzymes, and the formulation released structurally intact, biologically active vesicles in colonic fluid. Preliminary in vivo studies showed that orally administered coated EVs reduced disease severity in a colitis mouse model and elicited a stronger therapeutic response than uncoated EVs administered orally or intravenously at the same dose. These findings indicate that, with appropriate formulation, oral delivery of MSC-EVs could be an effective route of administration to treat intestinal inflammation.

With the constant need for surface sterilization to prevent bacterial contamination, easily applied, non-leaching, wash resistant and contact-killing coatings that not include copper or silver ions are the ideal solution to the problem of inhibiting bacterial growth. Herein catechol coatings utilizing Schiff-base grafting to a polyethyleneimine matrix are evaluated for their contact inhibition against S.aureus and E.coli bacteria and their performance after water and ethanol washes, comparing zone of inhibition on agar plates and the toxicity of leachates from water submerged coatings.

Le RXP470.1 est l’un des premiers inhibiteurs puissants de la MMP-12, une métalloprotéase à zinc impliquée dans de nombreuses pathologies comme l’athéroclérose et la bronchopneumopathie obstructive chronique (BPCO). Pour comprendre les bases moléculaires contrôlant l’interaction de cet inhibiteur avec sa cible, des approches pluridisciplinaires associant des relations structure-activité, avec des études de cristallographie de complexes enzymes inhibiteurs et d’études de microcalorimétrie, décrivant les contributions enthalpiques et entropiques impliquées dans la formation des complexes, ont été réalisées dans ce travail de thèse. Les affinités de trois analogues du RXP470.1 ont été tout d’abord déterminées. Puis quatre structures cristallographiques de complexes enzyme/inhibiteur décrivant le mode d’interaction duRXP470.1 et de ces trois analogues ont été obtenues avec des résolutions de 1.15 Å, 1.50 Å, 1.50Å et 1.30 Å, respectivement. Parallèlement les études de microcalorimétrie ont été menées pour étudier les facteurs énergétiques contrôlant l’interaction du RXP470.1 avec la MMP-12. Les résultats indiquent que la présence d’une chaîne latérale très longue et hydrophobe en position P1’de l’inhibiteur s’insérant dans la cavité S1’ de la MMP-12 est essentielle à la très bonne affinité de cet inhibiteur pour la MMP-12. Cette interaction met essentiellement en jeu un effet entropique très important de - 4 kcal/mol. L’interaction du RXP470.1 est aussi essentiellement dirigée par une forte augmentation d’entropie (-TDS= -10 kal/mol) et une composante enthalpique beaucoup plus faible (DH= -2.5 kcal/mol), et ce malgré l’observation dans le cristal de nombreuses interactions entre l’inhibiteur et le site actif de la MMP-12. L’étude de microcalorimétrie met aussi en lumière la prise d’un proton au cours de la formation du complexe enzyme inhibiteur impliquant deux résidus chargés négativement en solution, le résidu catalytique Glu219 et le groupe phosphoryle chélatant du zinc dans l’inhibiteur. Cette étude révèle aussi que si le groupe phosphoryle est considéré comme un chélatant faible de l’atome de zinc, il impose néanmoins des contraintes directionnelles très importantes qui ont un impact sur le positionnement des autres parties de l’inhibiteur dans le site actif de l’enzyme. Ce dernier effet pourrait expliquer pourquoi un certain nombre d’interactions entre l’inhibiteur et l’enzyme ne sont pas optimisées et pourquoi la variation d’enthalpie pour former le complexe reste relativement faible. Cette étude ouvre maintenant la voie à d’autres études en plaçant au centre des futurs travaux le rôle du groupe chélatant dans la conception des inhibiteurs de MMP, ainsi de nouveaux inhibiteurs puissants et sélectifs d’autres MMP devraient voir le jour grâce à ce travail et aux résultats obtenus.

Nucleic acid therapeutics (NATs) promise to revolutionize the fight against diseases like cancer, yet their full potential remains untapped due to significant delivery challenges. In this study, innovative nano‐cell vesicle technology systems (nCVTs) are developed to target NATs to cancer cells. nCVTs are created by fusing cationic lipids with pre‐emptied cell membranes that can efficiently bind and transport NATs such as antisense oligonucleotides (ASOs). In the study, nCVTs loaded with an anti‐cancer ASO, AS014 (nCVTs _AS014 ) outperformed both liposomes and free AS014 in delivering the therapeutic payload into cancer cells, reaching both the cytoplasm and nuclei with remarkable efficiency while displaying lower intrinsic cytotoxicity. Most impressively, nCVTsAS014 demonstrated potent inhibition of tumor growth in vivo, underscoring its potential as a powerful cancer therapy platform. Altogether, the findings highlight nCVTs as a promising strategy to unlock the therapeutic power of NATs, paving the way toward more effective and targeted treatments for cancer.

Gradient hydrogels are an emerging strategy in tissue engineering to mimic the heterogeneity in native tissues. Herein, the metal‐thiolate complexation mechanism is exploited by allowing diffusion of silver ions (Ag ⁺ ) through a cysteine‐rich human hair keratin (HHK) solution to produce a novel gradient hydrogel. This one‐step approach enables the combined benefits of a sustainable material with an established antimicrobial agent. Herein, the gelation kinetics, physical, mechanical, and biochemical properties of the gradient hydrogel are correlated over a range of thiol:Ag ratios. The presence of a porosity gradient within a single construct, along with dissimilar top and bottom surface morphologies, is shown. Disk diffusion tests against Staphylococcus aureus verified the antibacterial activity of this Ag‐loaded hydrogel. Additionally, hydrogels at 1.25 thiol:Ag ratio supported > 95% viability and proliferation of human dermal fibroblasts (HDFs), comparable to collagen hydrogels. These HDFs produce fibronectin, collagen III, and express alpha‐smooth muscle actin within the gradient hydrogels. In an in vivo full‐thickness wound healing mouse model, the 1.25 hydrogel evoke minimal host tissue response, support reepithelialization more than the uniform Gelatin Methacrylate (GelMA) hydrogel, and promote the most collagen deposition. These findings demonstrate the practicality of metal‐thiolate complexation in producing biomimetic gradient hydrogels for tissue regeneration.

Despite advances in therapy for inflammatory bowel disease (IBD), current treatments are still associated with poor clinical outcomes and severe systemic side effects. Extracellular vesicles derived from mesenchymal stem cells (MSC-EVs) could have therapeutic applications in IBD due to their regenerative potential and immunomodulatory properties. Previous studies investigating the potential of MSC-EVs in IBD have largely administered the vesicles by injection, which does not offer the significant benefits of oral administration, including direct and localised access to the site(s) of intestinal inflammation. Here, we evaluated the stability of MSC-EVs for oral delivery by assessing particle size, concentration and EV markers. The EVs disintegrated in gastrointestinal (GI) fluids, with cryogenic electron microscopy confirming the loss of structural integrity. To address this, we developed a double-coating formulation consisting of chitosan and Eudragit S100 to enhance GI stability and facilitate colon-targeted delivery. We demonstrated that coated EVs were resistant to GI fluids and digestive enzymes, and the formulation released intact vesicles in colonic fluid. Preliminary in vivo studies in a dextran sodium sulfate-induced colitis mouse model showed that coated EVs reduced disease severity, whereas uncoated EVs performed similarly to the control group. Interestingly, coated MSC-EVs elicited a stronger therapeutic response compared to EVs administered intravenously at the same dose. These findings indicate that oral delivery of MSC-EVs could be an effective route of administration, with appropriate formulation, to treat intestinal inflammation.

MRNA-based vaccines against the COVID-19 pandemic have propelled the use of nucleic acids for drug delivery. Conventional lipid-based carriers, such as liposomes and nanolipogels, effectively encapsulate and deliver RNA but are hindered by issues such as premature burst release and immunogenicity. To address these challenges, cell membrane-coated nanoparticles offer a promising alternative. We developed a novel nanoparticle system using chitosan methacrylate-tripolyphosphate (CMATPP), which capitalizes on interactions involving membrane proteins at biointerfaces. Ionic crosslinking between chitosan methacrylate and tripolyphosphate facilitates the formation of nanoparticles amenable to coating with red blood cell (RBC) membranes, extracellular vesicles (EVs), and cell-derived nanovesicles (CDNs). Coating CMATPP nanoparticles with RBC membranes effectively mitigated the initial burst release of encapsulated small interfering RNA (siRNA), sustaining controlled release while preserving membrane proteins. This concept was extended to EVs, where CMATPP nanoparticles and CDNs were incorporated into a microfluidic device and subjected to electroporation to create hybrid CDN-CMATPP nanoparticles. Our findings demonstrate that CMATPP nanoparticles are a robust siRNA delivery system with suppressed burst release and enhanced membrane properties conferred by cell or vesicle membranes. Furthermore, the adaptation of the CDN-CMATPP nanoparticle formation in a microfluidic device suggests its potential for personalized therapies using diverse cell sources and increased throughput via automation. This study underscores the versatility and efficacy of CMATPP nanoparticles in RNA delivery, offering a pathway towards advanced therapeutic strategies that utilize biomimetic principles and microfluidic technologies.

This study investigates the effects of homopolymer additives and kinetic traps on the self-assembly of poly(ethylene glycol)-b-poly(lactide) (PEG-PLA) block copolymer (BCP) nanostructures in aqueous environments. By using non-adsorbing PEG homopolymers to kinetically trap PEG-PLA nanostructures, we demonstrate that varying the concentration and molecular weight of the added PEG induces a reversible micelle-to-vesicle transition. This transition is primarily driven by changes in the molecular geometry of the PEG-PLA BCPs due to excluded volume screening effects. Additionally, the reversible vesicle-to-micelle transition upon PEG’s removal shows time and temperature dependency, highlighting the influence of the system’s kinetic nature. Intermediate structures observed during the transition support a mechanism based on shifts in the molecular geometry of PEG-PLA. As a proof of concept, we show that PEG-PLA vesicles can act as thermoresponsive delivery systems, retaining dye at low temperatures (4 °C) and releasing it upon heating (37 °C). Overall, this work presents a novel approach to controlling BCP nanostructures’ morphology, with implications for drug delivery and material science applications.