Nanocarriers based on interpolyelectrolyte complexation of Sulphated polysaccharide-b- PEG diblock copolymers and PLL

Publicado em "Journal of Tissue Engeneering and Regenerative Medicine", vol. 7, supp. 1 (2013)Glycosaminoglycans (GAGs) are integral part of the closest cellular environment: they can be found on the cells surface and in the extracellular matrix, where they interact with different proteins acting as local regulator of their activity. The use of GAGs in the preparation of protein delivery nanosystems is, therefore, prominent but so far, underexploited mainly because of the heterogeneity (composition and molecular weights) of natural glycans and the multistep procedures needed to obtain GAGs’ synthetic analogues and diblock copolymers.1 Recently, we have shown that oxime click reaction can be applied as a straightforward methodology for the synthesis of poly(ethylene glycol) (PEG)- hyaluronic acid (HA) diblock copolymers.2 These copolymers formed nanosized interpolyelectrolyte complexes (45 to 150 nm) by interaction with poly- L -lysine (PLL).3 Unfortunately, these complexes are not stable at physiological ionic strength. Herein, we describe a strategy to overcome this drawback; chondroitin sulphate-b-PEG diblock copolymers (CS-b-PEG) were obtained using the same oxime click reaction. The stronger negative charge of sulphate groups (versus the carboxilic groups present in HA) resulted in the complexes with higher stability: interpolyelectrolyte complexes between PLL and (CS-b-PEG) are stable up to 260 mM ionic strenght. Because carbohydrates do not activate Tcells, we believe that the reported herein complexes have an enormous potential in both drug delivery and vaccination fields

CARB 113: Co-assembly of peptide and carbohydrate amphiphiles to generate proteoglycan mimics

Peptide amphiphiles (PA) have been used as building blocks that generate nanofibrous protein mimics through self-assembly under physiological conditions. These supramolecular structures are maintained by non-covalent interactions, such as, Pi-Pi stacking, hydrogen bonding and hydrophobic effects. The generated fibers can be further crosslinked via salt bridges thus forming hydrated systems that resemble the extracellular matrix (ECM) at structural and functional level. However, the proteins in the ECM are often presented as glycoconjugates such as glycoproteins and proteoglycans. Carbohydrate-modified PAs are just emerging as alternative or complementary building blocks able to generate closer supramolecular ECM mimics. Such PAs are challenging at synthetic, supramolecular and biofunctional level. Carbohydrates bear different â OH groups prompt to react and thus, different protections are needed for selective functionalization. Moreover, once conjugated to the PA, the carbohydrate moiety can alter its self-assembling capacity, as well as, the biofunctionality of the incorporated bioactive peptide. We therefore developed a simpler approach for generation of minimalistic proteoglycan mimics: co-assembly of short, aromatic PA and their carbohydrate analogues. The nanofibers generated by this approach have a PA core (e.g. fmoc-FF) and a carbohydrate shell (e.g. fmoc-glucosamine-6-phosphate or fmoc-glucosamine-6-sulfate). They present: 1) a higher mechanical performance than the PA single component systems; 2) an improved biofunctionality as demonstrated by our studies with growth factors (e.g. FGF2), lectins and cells. Peptide amphiphiles (PA) have been used as building blocks that generate nanofibrous protein mimics through self-assembly under physiological conditions. These supramolecular structures are maintained by non-covalent interactions, such as, Pi-Pi stacking, hydrogen bonding and hydrophobic effects. The generated fibers can be further crosslinked via salt bridges thus forming hydrated systems that resemble the extracellular matrix (ECM) at structural and functional level. However, the proteins in the ECM are often presented as glycoconjugates such as glycoproteins and proteoglycans. Carbohydrate-modified PAs are just emerging as alternative or complementary building blocks able to generate closer supramolecular ECM mimics. Such PAs are challenging at synthetic, supramolecular and biofunctional level. Carbohydrates bear different –OH groups prompt to react and thus, different protections are needed for selective functionalization. Moreover, once conjugated to the PA, the carbohydrate moiety can alter its self-assembling capacity, as well as, the biofunctionality of the incorporated bioactive peptide. We therefore developed a simpler approach for generation of minimalistic proteoglycan mimics: co-assembly of short, aromatic PA and their carbohydrate analogues. The nanofibers generated by this approach have a PA core (e.g. fmoc-FF) and a carbohydrate shell (e.g. fmoc-glucosamine-6-phosphate or fmoc-glucosamine-6-sulfate). They present: 1) a higher mechanical performance than the PA single component systems; 2) an improved biofunctionality as demonstrated by our studies with growth factors (e.g. FGF2), lectins and cells.  info:eu-repo/semantics/publishedVersio

Minimalistic supramolecular proteoglycan mimics by co-assembly of aromatic peptide and carbohydrate amphiphiles

We report the co-assembly of aromatic carbohydrate and dipeptide amphiphiles under physiological conditions as a strategy to generate minimalistic proteoglycan mimics. The resulting nanofibers present a structural, fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) core and a functional carbohydrate (Fmoc-glucosamine-6-sulfate or -phosphate) shell. The size, degree of bundling and mechanical properties of the assembled structures depend on the chemical nature of the carbohydrate amphiphile used. In cell culture medium, these nanofibers can further organize into supramolecular hydrogels. We demonstrate that, similar to proteoglycans, the assembled gels prolong the stability of growth factors and preserve the viability of cultured cells. Our results demonstrate that this approach can be applied to the design of extracellular matrix (ECM) substitutes for future regenerative therapies.We acknowledge the EU's H2020 and FP7 framework programmes (Forecast 668983; CHEM2NATURE 692333; THE DISCOVERIES CTR 739572; ERC AdG ComplexiTE 321266) and the Portuguese FCT (IF/00032/2013; BD/113794/2015; BPD/85790/2012; M-ERA-NET2/0001/2016 – INCIPIT; ENMed/001/2015 – CytoNanoHeal). We thank P. Frederix for his help in the FTIR measurements and M. Mullin for her help in the TEM imaging.info:eu-repo/semantics/publishedVersio

End-on PEGylation of heparin: Effect on anticoagulant activity and complexation with protamine

Supplementary data to this article can be found online at https://doi.org/10.1016/j.ijbiomac.2023.125957.Heparin is the most common anticoagulant used in clinical practice but shows some downsides such as short half- life (for the high molecular weight heparin) and secondary effects. On the other hand, its low molecular weight analogue cannot be neutralized with protamine, and therefore cannot be used in some treatments. To address these issues, we conjugated polyethylene glycol (PEG) to heparin reducing end (end-on) via oxime ligation and studied the interactions of the conjugate (Hep-b-PEG) with antithrombin III (AT) and protamine. Isothermal titration calorimetry showed that Hep-b-PEG maintains the affinity to AT. Dynamic light scattering demonstrated that the Hep-b-PEG formed colloidal stable nanocomplexes with protamine instead of large multi-molecular aggregates, associated with heparin side effects. The in vitro (human plasma) and in vivo experiments (Sprague Dawley rats) evidenced an extended half-life and higher anticoagulant activity of the conjugate when compared to unmodified heparin.  The authors thank INNO Laboratório Veterinário for the measurements of in vivo coagulation times, Raul Pacheco for discussions about the ITC results, Teresa Oliveira for her help in the in vivo experiments and Ramón Rail for his help in the 3D structures of Fig. 1, Fig. 4. We thank funding provided by the Portuguese Foundation for Science and Technology (PTDC/QUI-POL/28117/2017 and CEECIND/00814/2017). África González-Fernández thanks Xunta de Galicia (Grupo de Referencia competitiva, GRC-ED431C 2020/02) 2020-2023

Biomedical potential of fucoidan, a seaweed sulfated polysaccharide: from a anticancer agent to a building block of cell encapsulating systems for regenerative medicine

Marine macroalgae or seaweeds synthesize a wide variety of polymers and smaller compounds with several bioactivities, among which the sulfated polysaccharides acquire greater relevance not only due to the reported antioxidant, antiviral and anticancer[1] activities, but also to the resemblance of extracellular matrix glycosaminoglycans found in the human body[2]. In this study, the potential of fucoidan (Fu) isolated from brown seaweed Fucus vesiculosus for therapeutical use has been evaluated, focusing in its performance as antitumoral agent (bioactive role) or as building block of cell encapsulating systems (structural role). Materials and Methods: The anticancer activity of Fu extracts was assessed by evaluating the cytotoxic behavior over two human breast cancer cell lines (MCF-7 and MDA-MB-231) in in-vitro culture, using human fibroblasts and endothelial cells (HPMEC-ST1 and MRC-5, respectively) as reference. Regarding the structural role, Fu was modified by methacrylation reaction (MFu) using methacrylic acid and further crosslinked using visible radiation and triethanolamine and eosin-y as photoinitiators. The photocrosslinking was performed on MFu solution droplets placed in a silica-based superhydrophobic surface[3], allowing the formation of particles[4] (since natural Fu is highly soluble in water and ion gelation is not effective). Biological performance of the developed particles was assessed by in vitro culture of fibroblasts and pancreatic cells (L929 and 1.1B4, respectively) in contact with MFu particles, up to 7 days. The ability of the developed materials to support adhesion and proliferation of cells was evaluated for both types of cells. Results and Discussion: The tested anticancer activity is not ubiquitous on Fu extracts, being dependent on its chemical features, with molecular weight (Mw) representing a particular role. Specifically, Mw values around 60 kDa exhibited cytotoxic effects to human breast cancer cell lines, while not affecting normal fibroblasts or endothelial cells (which represent the cells of the healthy tissue that would be closer to the tumor in a real situation). A concentration range of 0.2 to 0.3 mg mL-1 from the selected Fu extract could be considered as the therapeutic window for further studies. Regarding fucoidanâ s role on innovative biomaterials, the developed MFu particles could support the proliferation of fibroblasts (L929), but also of human pancreatic beta cells (1.1B4), which tend to form pseudo-islets after 7 days in culture (Fig. 1). This pancreatic cells could be also successfully encapsulated, opening a new route for a diabetes mellitus type 1 therapeutic approach. Fig. 1: Confocal microscopy images of 1.1B4 cells cultured in the presence of fucoidan-based particles and organized in pseudo-islets (red â actin; blue â nuclei). Conclusion: The present work establishes fucoidan as a high performance building block for the development of advanced therapies for cancer (targeted therapy) or tissue and organ regeneration. It shed light on the relation between chemical structure and biological activity towards anti-cancer effect and proposes novel beta cell laden particles as injectable insulin producing systems to tackle diabetes.Funding from projects 0687_NOVOMAR_1_P (co-funded by INTERREG 2007-2013 / POCTEP), CarbPol_u_Algae (EXPL/MAR-BIO/0165/2013, funded by the Portuguese Foundation for Science and Technology, FCT), POLARIS (FP7-REGPOT-CT2012-316331) and ComplexiTE (ERC-2012-ADG 20120216-321266), funded by the European Union’s Seventh Framework Programme for Research and Development is acknowledged. ASF, SSS, NMO and DSC are also thankful to FCT for their individual fellowships

Interplay between Structure and Dynamics in Chitosan Films Investigated with Solid-State NMR, Dynamic Mechanical Analysis, and X-ray Diffraction

Modern solid-state NMR techniques, combined with X-ray diffraction, revealed the molecular origin of the difference in mechanical properties of self-associated chitosan films. Films cast from acidic aqueous solutions were compared before and after neutralization, and the role of the counterion (acetate vs Cl⁻) was investigated. There is a competition between local structure and long-range order. Hydrogen bonding gives good mechanical strength to neutralized films, which lack long-range organization. The long-range structure is better defined in films cast from acidic solutions in which strong electrostatic interactions cause rotational distortion around the chitosan chains. Plasticization by acetate counterions enhances long-range molecular organization and film flexibility. In contrast, Cl⁻ counterions act as a defect and impair the long-range organization by immobilizing hydration water. Molecular motion and proton exchange are restricted, resulting in brittle films despite the high moisture content

Physicochemical and biological characterization of chitosan-microRNA nanocomplexes for gene delivery to MCF-7 breast cancer cells

Cancer gene therapy requires the design of non-viral vectors that carry genetic material and selectively deliver it with minimal toxicity. Non-viral vectors based on cationic natural polymers can form electrostatic complexes with negatively-charged polynucleotides such as microRNAs (miRNAs). Here we investigated the physicochemical/biophysical properties of chitosan–hsa-miRNA-145 (CS–miRNA) nanocomplexes and the biological responses of MCF-7 breast cancer cells cultured in vitro. Self-assembled CS–miRNA nanocomplexes were produced with a range of (+/−) charge ratios (from 0.6 to 8) using chitosans with various degrees of acetylation and molecular weight. The Z-average particle diameter of the complexes was <200 nm. The surface charge increased with increasing amount of chitosan. We observed that chitosan induces the base-stacking of miRNA in a concentration dependent manner. Surface plasmon resonance spectroscopy shows that complexes formed by low degree of acetylation chitosans are highly stable, regardless of the molecular weight. We found no evidence that these complexes were cytotoxic towards MCF-7 cells. Furthermore, CS–miRNA nanocomplexes with degree of acetylation 12% and 29% were biologically active, showing successful downregulation of target mRNA expression in MCF-7 cells. Our data, therefore, shows that CS–miRNA complexes offer a promising non-viral platform for breast cancer gene therapy

Insights into the innate immunity of the Mediterranean mussel Mytilus galloprovincialis

<p>Abstract</p> <p>Background</p> <p>Sessile bivalves of the genus <it>Mytilus </it>are suspension feeders relatively tolerant to a wide range of environmental changes, used as sentinels in ecotoxicological investigations and marketed worldwide as seafood. Mortality events caused by infective agents and parasites apparently occur less in mussels than in other bivalves but the molecular basis of such evidence is unknown. The arrangement of Mytibase, interactive catalogue of 7,112 transcripts of <it>M. galloprovincialis</it>, offered us the opportunity to look for gene sequences relevant to the host defences, in particular the innate immunity related genes.</p> <p>Results</p> <p>We have explored and described the Mytibase sequence clusters and singletons having a putative role in recognition, intracellular signalling, and neutralization of potential pathogens in <it>M. galloprovincialis</it>. Automatically assisted searches of protein signatures and manually cured sequence analysis confirmed the molecular diversity of recognition/effector molecules such as the antimicrobial peptides and many carbohydrate binding proteins. Molecular motifs identifying complement C1q, C-type lectins and fibrinogen-like transcripts emerged as the most abundant in the Mytibase collection whereas, conversely, sequence motifs denoting the regulatory cytokine MIF and cytokine-related transcripts represent singular and unexpected findings. Using a cross-search strategy, 1,820 putatively immune-related sequences were selected to design oligonucleotide probes and define a species-specific Immunochip (DNA microarray). The Immunochip performance was tested with hemolymph RNAs from mussels injected with <it>Vibrio splendidus </it>at 3 and 48 hours post-treatment. A total of 143 and 262 differentially expressed genes exemplify the early and late hemocyte response of the <it>Vibrio</it>-challenged mussels, respectively, with AMP trends confirmed by qPCR and clear modulation of interrelated signalling pathways.</p> <p>Conclusions</p> <p>The Mytibase collection is rich in gene transcripts modulated in response to antigenic stimuli and represents an interesting window for looking at the mussel immunome (transcriptomes mediating the mussel response to non-self or abnormal antigens). On this basis, we have defined a new microarray platform, a mussel Immunochip, as a flexible tool for the experimental validation of immune-candidate sequences, and tested its performance on <it>Vibrio</it>-activated mussel hemocytes. The microarray platform and related expression data can be regarded as a step forward in the study of the adaptive response of the <it>Mytilus </it>species to an evolving microbial world.</p

Following the enzymatic digestion of chondroitin sulfate by a simple GPC analysis

We describe the use of gel permeation chromatography (GPC) setup with four size exclusion columns for analysis of enzymatically digested glycosaminoglycans (GAGs). This setup provides information about the molecular weight (Mw) and concentration of all species (low and high Mw) present in the digests in a single measurement. The data about the fraction with high Mw (often omitted in the analysis of GAG digests) provide direct evidence about the mechanisms of action of the enzymes. We proved the feasibility of this methodology by applying it to chondroitin sulfate (CS) substrates with different molecular weight and sulfation pattern and using different enzymes (hyaluronidase and chondroitinase). NMR analysis of the obtained digests fractionated by ultrafiltration confirmed the results obtained by GPC setup and reveal further details about the degradation mechanisms: (i) both enzymes preferentially attack 4-sulfated chondroitin and (ii) additionally to the well documented endolytic activity of hyaluronidase we also observed a low lyase activity for this enzyme reflected in the detected minor exolytic breakage. Finally, we demonstrate that CS with medium molecular weight (12â 60 kDa) which is sulfated mainly at 6-position can be obtained in good yields by enzymatic digestion and following ultrafiltration.The authors acknowledge the ON.2 (NORTE-01-0124-FEDER-000016), the EU-FP7 (REGPOT-2012-2013-1-316331) and Portuguese Foundation for Science and Technology (IF/00032/2013). RNC is thankful to Xunta de Galicia for providing him a fellowship