Influence of Surface Chemistry on Host/Guest Interactions: A Model Study on Redox-Sensitive ß-Cyclodextrin/Ferrocene Complexes.

While host/guest interactions are widely used to control molecular assembly on surfaces, quantitative information on the effect of surface chemistry on their efficiency is lacking. To address this question, we combined electrochemical characterization with quartz crystal microbalance with dissipation monitoring to study host/guest interactions between surface-attached ferrocene (Fc) guests and soluble ß-cyclodextrin (ß-CD) hosts. We identified several parameters that influence the redox response, ß-CD complexation ability, and repellent properties of Fc monolayers, including the method of Fc grafting, the linker connecting Fc with the surface, and the diluting molecule used to tune Fc surface density. The study on monovalent ß-CD/Fc complexation was completed by the characterization of multivalent interactions between Fc monolayers and ß-CD-functionalized polymers, with new insights being obtained on the interplay between the surface chemistry, binding efficiency, and reversibility under electrochemical stimulus. These results should facilitate the design of well-defined functional interfaces and their implementation in stimuli-responsive materials and sensing devices.

Hyaluronic acid single-network hydrogel with high stretchable and elastic properties.

Stretchable materials have demonstrated great interest in wearable or implantable applications. Most of the existing hydrogels with high stretchability characteristics are based on double networks, exhibit large hysteresis loops, and cannot recover after deformation due to permanent rupture of network. Elastic, biodegradable, and biocompatible hydrogels are desirable for wound dressing of joints with frequent motions or post-surgical healing of mobile tissues. Here, we show a simple strategy for the preparation of a hyaluronic acid (HA) single-network hydrogel that can be stretchable and highly elastic without the addition of other components/partners or complicated processes of preparation. Our strategy relies on the use of high Mw HA to create a chemical hydrogel in which densely entangled HA chains are tied together by a small number of covalent bonds. While the presence of covalent cross-links can prevent disintegration of the HA network, entanglements endow the hydrogel with high stretchability through transmission of tension along the length of the long HA chains. The stretching-relaxation cycles show negligible hysteresis and perfect recovery of material after the release of force. The diminution of Mw together with increasing the concentration or cross-linker amount leads to brittle hydrogels.

A novel injectable radiopaque hydrogel with potent properties for multicolor CT imaging in the context of brain and cartilage regenerative therapy.

Cell therapy is promising to treat many conditions, including neurological and osteoarticular diseases. Encapsulation of cells within hydrogels facilitates cell delivery and can improve therapeutic effects. However, much work remains to be done to align treatment strategies with specific diseases. The development of imaging tools that enable monitoring cells and hydrogel independently is key to achieving this goal. Our objective herein is to longitudinally study an iodine-labeled hydrogel, incorporating gold-labeled stem cells, by bicolor CT imaging after in vivo injection in rodent brains or knees. To this aim, an injectable self-healing hyaluronic acid (HA) hydrogel with long-persistent radiopacity was formed by the covalent grafting of a clinical contrast agent on HA. The labeling conditions were tuned to achieve sufficient X-ray signal and to maintain the mechanical and self-healing properties as well as injectability of the original HA scaffold. The efficient delivery of both cells and hydrogel at the targeted sites was demonstrated by synchrotron K-edge subtraction-CT. The iodine labeling enabled to monitor the hydrogel biodistribution in vivo up to 3 days post-administration, which represents a technological first in the field of molecular CT imaging agents. This tool may foster the translation of combined cell-hydrogel therapies into the clinics.

Design of hyaluronan-based dopant for conductive and resorbable PEDOT ink.

Conformable biocompatible conductive materials are increasingly sought for the development of bioelectronics. If additionally resorbable, they could serve for the design of transient implantable electronic devices, opening the way to new healthcare applications. Hyaluronan (HA) derivatives including sulfate and aminophenylboronic acid (PBA) groups (HAS-PBA) were therefore designed to serve as dopants of poly(3,4-ethylenedioxy)thiophene (PEDOT). The optimized HA sulfation protocol allowed good control on polymer sulfation degree while minimizing polymer chain degradation. Sulfated HA was shown to be degradable in physiological conditions. A synergy was observed between the sulfate negative charges and the PBA aromatic groups promoting hydrophobic interactions and π-stacking between PEDOT and HAS-PBA, to boost the material conductivity that reached 1.6 ± 0.2 S/cm in physiological conditions. Moreover the PEDOT:HAS-PBA material was not cytotoxic and could be formulated for easy processing by inkjet printing, appearing as promising candidate for the design of soft transient electronics for in vivo applications.

Tailored hyaluronic acid-based nanogels as theranostic boron delivery systems for boron neutron cancer therapy.

Boron-rich nanocarriers possess great potential for advanced boron neutron capture therapy (BNCT) as an effective radiation treatment for invasive malignant tumors. If additionally, they can be imaged in a non-invasive and real-time manner allowing the assessment of local boron concentration, they could serve for dose calculation and image-guided BNCT to enhance tumor treatment efficacy. To meet this challenge, this study describes the design of a theranostic nanogel, enriched in 10B and fluorescent dye, to achieve selective imaging, and sufficient accumulation of boron at the tumor site. The boron-rich and fluorescent nanogels can be easily obtained via temperature triggered-assembly of hyaluronic acid (HA) modified with a thermoresponsive terpolymer. The latter was specifically designed to enable the efficient encapsulation of the fluorescent dye - an aza­boron-dipyrromethene (aza-BODIPY) - linked to 10B-enriched sodium borocaptate (BSH), in addition to induce nanogel formation below room temperature, and to enable their core-crosslinking by hydrazone bond formation. The HA nanogel considerably concentrates aza-BODIPY-BSH into the hydrophobic nanodomains made of the terpolymer chains. Here, we present the detailed synthesis of the HA-terpolymer conjugate, nanogel formation, and characterization in terms of size, morphology, and stability upon storage, as well as the biological behavior of the boron nanocarrier using real-time fluorescence imaging in cells and in vivo. This work suggested the potential of the theranostic HA nanogel as a boron delivery system for the implementation of BNCT in brain cancer and sarcoma.

Boronate-ester crosslinked hyaluronic acid hydrogels for dihydrocaffeic acid delivery and fibroblasts protection against UVB irradiation.

Herein, we exploit the dynamic nature and pH dependence of complexes between phenylboronic acid and diol-containing molecules to control the release of an anti-photoaging agent, dihydrocaffeic acid (DHCA), from a dynamic covalent hydrogel (HG). The HG is prepared by reversible formation of boronate ester crosslinks between hyaluronic acid (HA) modified with saccharide (GLU) residues and HA functionalized with 3-aminophenylboronic acid (APBA), part of which is involved in complexation with DHCA. The hydrogel exhibited increased dynamic moduli and a lower relaxation time at pH 7.4 in comparison to pH 6, and greater amount of DHCA was incorporated at pH 7.4. Moreover, this hydrogel prolonged DHCA release at pH 7.4 through drug reversible complexation/decomplexation, while the rate of release was fastest in acidic (skin) conditions. Very interestingly, the incorporation of DHCA into the network enhances its protection against UVB-induced L929 fibroblast death. Therefore, this smart hydrogel can contribute to photoaging prevention.

Dynamic Covalent Chemistry Enables Reconfigurable All-Polysaccharide Nanogels.

Dynamic covalent bonds are established upon molecular recognition of sugar derivatives by boronic acid molecules. These reversible links can be used in a cross-linking method to fabricate polymer-based responsive nanosystems. Herein, the design of the first dynamic nanogels made entirely of polysaccharides (PS) is reported. Based on PS chains alternately modified with phenyl boronic acid groups and sugar moieties, these colloids self-assemble in physiological conditions and combine the biocompatible nature of their PS backbone with the reconfiguration capacities of their cross-linking chemistry. These dynamic nanogels are easily prepared, stable for a long time, pH responsive, and efficiently internalized by cancer cells.

Hydrogel-Colloid Composite Bioinks for Targeted Tissue-Printing.

The development of extrusion-based bioprinting for tissue engineering is conditioned by the design of bioinks displaying adequate printability, shape stability, and postprinting bioactivity. In this context, simple bioink formulations, made of cells supported by a polymer matrix, often lack the necessary versatility. To address this issue, intense research work has been focused on introducing colloidal particles into the ink formulation. By creating weak cross-links between polymer chains, added particles modify the rheology and mechanical behavior of bioinks to improve their printability and structural integrity. Additionally, nano- and microscopic particles display composition- and structure-specific properties that can affect the cellular behavior and enhance the formation of tissue within the printed material. This Review offers a comprehensive picture of the role of colloids in bioprinting from a physicochemical and biological perspective. As such, it provides guidance on devising adaptable bioinks for the fabrication of biomimetic tissues.

Development of chitosan nanocapsules containing essential oil of Matricaria chamomilla L. for the treatment of cutaneous leishmaniasis.

Matricaria chamomilla L. has been used for centuries in many applications, including antiparasitic activity. Leishmaniasis is a parasitic disease, with limited treatments, due to high cost and toxicity. Thus, there is a need to develop new treatments, and in this context, natural products are targets of these researches. We report the development of chitosan nanocapsules containing essential oil of M. chamomilla (CEO) from oil-in-water emulsions using chitosan modified with tetradecyl chains as biocompatible shell material. The nanocapsules of CEO (NCEO) were analyzed by optical microscopy and dynamic light scattering, which revealed spherical shape and an average size of 800 nm. Successful encapsulation of CEO was further confirmed by fluorescence microscopy observations taking advantage of the autofluorescence properties of CEO. The encapsulation efficiency was around 90%. The entrapment of CEO reduced its cytotoxicity towards normal cells. On the other hand, the CEO was active against promastigotes and intracellular amastigotes, exhibiting IC50 of 3.33 µg/mL and 14.56 µg/mL, respectively, while NCEO showed IC50 for promastigotes of 7.18 µg/mL and for intracellular amastigotes of 14.29 µg/mL. These results demonstrate that encapsulation of CEO in nanocapsules using an alkylated chitosan biosurfactant as a "green" stabilizer is a promising therapeutic strategy to treat leishmaniasis.

Boronic acid and diol-containing polymers: how to choose the correct couple to form "strong" hydrogels at physiological pH.

Dynamic covalent hydrogels crosslinked by boronate ester bonds are promising materials for biomedical applications. However, little is known about the impact of the crosslink structure on the mechanical behaviour of the resulting network. Herein, we provide a mechanistic study on boronate ester crosslinking upon mixing hyaluronic acid (HA) backbones modified, on the one hand, with two different arylboronic acids, and on the other hand, with three different saccharide units. Combining rheology, NMR and computational analysis, we demonstrate that carefully selecting the arylboronic-polyol couple allows for tuning the thermodynamics and molecular exchange kinetics of the boronate ester bond, thereby controlling the rheological properties of the gel. In particular, we report the formation of "strong" gels (i.e. featuring slow relaxation dynamics) through the formation of original complex structures (tridentate or bidentate complexes). These findings offer new prospects for the rational design of hydrogel scaffolds with tailored mechanical response.

Liposome-based nanocarrier loaded with a new quinoxaline derivative for the treatment of cutaneous leishmaniasis.

The use of nanocarriers for drug delivery is a strategy aimed to improve therapeutic indices through changes in their pharmacokinetic and pharmacodynamic characteristics. Liposomes are well-investigated nanocarriers for drug delivery to macrophage-targeted therapy, the main hosts of intracellular pathogens of some infectious diseases, such as leishmaniasis. In this study, we developed hyaluronic acid (HA)-coated liposomes by different methods that can encapsulate a new quinoxaline derivative, the LSPN331, to increase its solubility and improve its bioavailability. The surface modification of liposomes and their physicochemical characteristics may depend on the coating method, which may be a critical parameter with regard to the route of administration of the antileishmanial drug. Liposomes with identical phospholipid composition containing the same drug were developed, and different biological responses were verified, and our hypothesis is that it is related to the type of modification of the surface. Different physicochemical characterization techniques (dynamic light scattering, transmission electron microscopy and UV-vis quantification of labeled-HA) were used to confirm the successful modification of liposomes as well as their stability upon storage. The encapsulation of LSPN331 was performed using HPLC method, and the entrapment efficiency (EE%) was satisfatory in all formulations, considering results of similar formulations in the literature. Furthermore, in vitro and in vivo studies were carried out to evaluate the efficacy against the parasite Leishmania amazonensis. The in vitro activity was maintained or even improved and HA-coated liposomes showed the ability to target to the site of action by the proposed routes of administration, topically and intravenously. Both formulations are promising for future tests of antileishmania activity in vivo.

Injectable Self-Healing Hydrogels Based on Boronate Ester Formation between Hyaluronic Acid Partners Modified with Benzoxaborin Derivatives and Saccharides.

We demonstrate here, for the first time, formation of injectable dynamic covalent hydrogels at physiological pH using benzoxaborin-saccharide complexation as a reversible cross-linking method. The gels were prepared by simply mixing hyaluronic acid modified with an original boronic acid derivative, 3,4-dihydro-2H-benzo[e][1,2]oxaborinin-2-ol (1,2-ABORIN), and HA functionalized with 1-amino-1-deoxy-d-fructose. Dynamic rheological experiments confirmed the gel-like behavior (storage modulus (G') > loss modulus (G″) in the frequency window explored) for the designed HA-1,2-ABORIN/HA-fructose network. Furthermore, this hydrogel exhibited excellent self-healing and injectability behaviors in aqueous conditions and was found to be responsive to pH. Additionally, fibroblast cells encapsulated in the HA network showed high viability (>80% after 7 days of cell culture), as monitored by Live/Dead staining. Taken together, this new class of boronate ester cross-linked hydrogel provides promising future for diverse biomedical applications.

Design of Soft Nanocarriers Combining Hyaluronic Acid with Another Functional Polymer for Cancer Therapy and Other Biomedical Applications.

The rapid advancement in medicine requires the search for new drugs, but also for new carrier systems for more efficient and targeted delivery of the bioactive molecules. Among the latter, polymeric nanocarriers have an increasingly growing potential for clinical applications due to their unique physical and chemical characteristics. In this regard, nanosystems based on hyaluronic acid (HA), a polysaccharide which is ubiquitous in the body, have attracted particular interest because of the biocompatibility, biodegradability and nonimmunogenic property provided by HA. Furthermore, the fact that hyaluronic acid can be recognized by cell surface receptors in tumor cells, makes it an ideal candidate for the targeted delivery of anticancer drugs. In this review, we compile a comprehensive overview of the different types of soft nanocarriers based on HA conjugated or complexed with another polymer: micelles, nanoparticles, nanogels and polymersomes. Emphasis is made on the properties of the polymers used as well as the synthetic approaches for obtaining the different HA-polymer systems. Fabrication, characterization and potential biomedical applications of the nanocarriers will also be described.

Heparosan as a potential alternative to hyaluronic acid for the design of biopolymer-based nanovectors for anticancer therapy.

Glycosaminoglycans (GAGs) are important components of the extracellular matrix that have attracted great interest for drug delivery and pharmaceutical applications due to their diverse biological functions. Among GAGs, heparosan (Hep), a biosynthetic precursor of heparin, has recently emerged as a promising building block for the design of nanoparticles with stealth properties. Though this non-sulfated polysaccharide has a chemical structure very close to that of hyaluronic acid (HA), it distinguishes from HA in that it is biologically inert in the extracellular spaces in the body. In this study, we designed Hep- and HA-based nanogels (NGs) that differ only in the chemical nature of the hydrophilic shell. The nanogels were prepared in a very straightforward way from Hep and HA modified with a thermoresponsive copolymer properly designed to induce self-assembly below room temperature. This versatile synthetic approach also enabled further shell-crosslinking allowing an increase in the colloidal stability. After careful characterization of the un-crosslinked and crosslinked Hep and HA NGs in terms of size (Z-average diameters of un-crosslinked and crosslinked NGs ∼110 and 150 nm) and morphology, they were injected intravenously into tumor-bearing mice for biodistribution experiments. Interestingly, these show that the liver uptake of Hep nanogels is remarkably reduced and tumor accumulation significantly improved as compared to HA nanogels (intensity ratios of tumor-to-liver of 2.2 and 1.4 for the un-crosslinked and crosslinked Hep NGs versus 0.11 for the un-crosslinked and crosslinked HA ones). These results highlight the key role played by the shell-forming GAGs on the in vivo fate of nanogels, which correlates with the specific biological properties of Hep and HA.

Dihydrocaffeic Acid Prevents UVB-Induced Oxidative Stress Leading to the Inhibition of Apoptosis and MMP-1 Expression via p38 Signaling Pathway.

Chronic UVB exposure promotes oxidative stress, directly causes molecular damage, and induces aging-related signal transduction, leading to skin photoaging. Dihydrocaffeic acid (DHCA) is a phenolic compound with potential antioxidant capacity and is thus a promising compound for the prevention of UVB-induced skin photodamage. The aim of this study was to evaluate the antioxidant and protective effect of DHCA against oxidative stress, apoptosis, and matrix metalloproteinase (MMP) expression via the mitogen-activated protein kinase (MAPK) signaling pathway on L929 fibroblasts irradiated with UVB. DHCA exhibited high antioxidant capacity on 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2-azinobis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS•+), and xanthine/luminol/xanthine oxidase (XOD) assays and reduced UVB-induced cell death in the neutral red assay. DHCA also modulated oxidative stress by decreasing intracellular reactive oxygen species (ROS) and extracellular hydrogen peroxide (H2O2) production, enhancing catalase (CAT) and superoxide dismutase (SOD) activities and reduced glutathione (GSH) levels. Hence, cellular damage was attenuated by DHCA, including lipid peroxidation, apoptosis/necrosis and its markers (loss of mitochondria membrane potential, DNA condensation, and cleaved caspase 9 expression), and MMP-1 expression. Furthermore, DHCA reduced the phosphorylation of MAPK p38. These findings suggest that DHCA can be used in the development of skin care products to prevent UVB-induced skin damage.

Physical nanocomposite hydrogels filled with low concentrations of TiO2 nanoparticles: Swelling, networks parameters and cell retention studies.

Physical nanocomposite hydrogels composed of poly(2-hydroxyethylmethacrylate) and titanium oxide nanoparticles at low concentrations (<1.0 wt%) were synthesized. The effect of the nanoparticle content on the water swelling and mechanical properties of the hydrogels was investigated. Additionally, to study the influence of the polymer-nanoparticle interactions, a second type of nanocomposite was synthesized using surface functionalized nanoparticles with 3-methacryloxypropyltrimethoxysilane as the filler. The pristine nanoparticles increased the swelling capacity, especially at short time scales, and greater solvent diffusion coefficients and initial swelling rates were achieved. In contrast, the nanocomposite filled with functionalized nanoparticles exhibited a diminished swelling capacity, a constant diffusion coefficient and a significant decrease in the initial swelling rate. The mechanical properties were studied by dynamic mechanical analyses using stress-relaxation tests. Two Maxwell models in parallel agreed well with the curves of the relaxation modulus as a function of time and indicated that at short relaxation times, the nanoparticles did not cause an effect, but that at longer times, the nanoparticles decreased the relaxation time. Finally, hydrogel network parameters determined by swelling measurements and mechanical experiments indicated that the hydrogel with well distributed nanoparticles decreases the molar mass between crosslink point and the mesh size, while poorly distributed nanoparticles lead to larger mesh size. Our functional studies show that the addition of titanium oxide nanoparticles improves the ability of nanocomposite hydrogels to retain aggregates of skeletal muscle cells, revealing their potential use as suitable scaffolds for tissue repair strategies.

A versatile method for the selective core-crosslinking of hyaluronic acid nanogels via ketone-hydrazide chemistry: from chemical characterization to in vivo biodistribution.

The development of biopolymer-based nanogels has gained particular interest to achieve successful delivery of therapeutics for the treatment of various diseases, such as cancer, infection and diabetes. Herein, we report a new and simple methodology for the covalent stabilization of self-assembled gel nanoparticles based on hyaluronic acid (HA) modified with a thermoresponsive ketone-functional copolymer. This relies on the selective formation of hydrazone crosslinks with bishydrazides within the globular domains of the copolymer chains formed above the cloud point temperature. This approach allows tuning of the crosslinking density by varying the dihydrazide crosslinker to ketone molar ratio. The size distributions and morphology of the nanogels were assessed using dynamic light scattering (DLS), cryo-transmission and scanning electron microscopy. In vitro cellular uptake in several cancer cells and in vivo biodistribution of the nanogels in different mouse tumor models were then explored to assess the effectiveness of this crosslinking strategy. The data from these experiments show prolonged blood circulation, longer than 24 hours, for the crosslinked nanogels and high tumor accumulation.

Chitosan-lipid nanoparticles (CS-LNPs): Application to siRNA delivery.

To benefit from the biocompatibility of lipid nanoparticles associated with the transfection ability of chitosan, small chitosan lipid nanoparticles (CS-LNPs) dedicated to SiRNA delivery were formulated by an easy-to-implement one-step process. Formulations of CS-LNPs (lipid core stabilized by a shell comprising phospholipids/cationic lipids and hydrophobically modified chitosan) were optimized for their physico-chemical properties (size, zeta potential, colloidal stability) according to their shell composition. In particular, amphiphilic chitosan with various molecular weight and C12 degrees of substitution, and different phospholipids and cationic lipids (lecithin, DOTAP, DOPE) were included at the particle surface at different ratios. The ability of the particles for SiRNA complexation, NIH3T3 cell transfection, and ERK1 downregulation, were studied. Lipid nanoparticles formulated with 15,000g/mol 2% C12 substituted chitosan, DOTAP and DOPE, mediated 40% ERK1 downregulation efficiency, comparable to lipofectamine™ RNAimax, while displaying no cytotoxicity up to 500µg/mL.

Coumarin-containing thermoresponsive hyaluronic acid-based nanogels as delivery systems for anticancer chemotherapy.

Multi-stimuli responsive nanogels based on biocompatible hydrophilic polymers have emerged as promising drug delivery systems to improve anticancer therapy with hydrophobic drugs, through increase of circulating-time in the bloodstream, tumor-targeting and reduction of systemic toxicity. This paper reports on the synthesis, characterization and biological perspectives of light- and thermoresponsive hyaluronic acid (HA)-based nanogels containing coumarin as the photocleavable group. Newly synthesized nanogels exhibited interesting features: formation by a temperature-triggered self-assembly process, successful incorporation of poorly water-soluble molecules, light-responsiveness as demonstrated by a significant shift in the critical aggregation temperature after light irradiation, efficient internalization by cancer cells overexpressing the CD44 receptor of HA, ability to circulate for a prolonged period of time in the bloodstream after intravenous injection in mice and considerable detection in tumor tissues. Our findings indicate that coumarin-containing HA-based nanogels may be promising delivery systems for anticancer chemotherapy.

Time-Controllable Lipophilic-Drug Release System Designed by Loading Lipid Nanoparticles into Polysaccharide Hydrogels.

A hybrid hydrogel composed of solid lipid nanoparticles (LNPs) entrapped within chemically cross-linked carboxymethylcellulose (CMC) is developed to achieve localized and sustained release of lipophilic drugs. The analysis of LNP stability as well as the hydrogel swelling and mechanical properties confirm the successful incorporation of particles up to a concentration of 50% w/wCMC . The initial LNP release rate can be prolonged by increasing the particle diameter from 50 to 120 nm, while the amount of long-term release can be adjusted by tailoring the particle surface charge or the cross-linking density of the polymer. After 30 d, 58% of 50 nm diameter negatively charged LNPs escape from the matrix while only 17% of positively charged nanoparticles are released from materials with intermediate cross-linking density. A mathematical diffusion model based on Fick's second law is efficient to predict the diffusion of the particles from the hydrogels.