Production and Characterization of Electrospun Chitosan, Nanochitosan and Hyaluronic Acid Membranes for Skin Wound Healing.

The development of new wound dressings made from biomaterials, which offer a better cost-benefit ratio and accelerate the healing process, is increasing nowadays. Various biopolymers can be electrospun to form functional membranes for wound healing. Therefore, in this study, chitosan and nanochitosan membranes with or without hyaluronic acid were prepared using the electrospinning technique, characterized and evaluated in the healing of skin wounds in rats. Chitosan and nanochitosan solutions, with or without hyaluronic acid, were prepared at concentrations of 1%-4% using PEO (polyethylene oxide) and subjected to the electrospinning process to obtain membranes characterized by scanning electron microscopy (SEM), mechanical tests, and antimicrobial activity. The healing effect of the membranes was evaluated by monitoring the area of the lesions, contraction of the wounds, histologic analysis, and induction of pro-inflammatory cytokine (IL-1 α and TNF-α) production in rats. The nanochitosan and nanochitosan membranes with hyaluronic acid achieved greater fiber diameter and uniformity, resistance, elasticity, and thermal stability, in addition to good adhesion to the wound bed and permeation capacity. Despite not presenting antimicrobial activity in vitro, they contributed to the production of pro-inflammatory interleukins in the animals tested, provided physical protection, reduced the wound area more markedly until the seventh day of the evaluation, with an acceleration of the healing process and especially when functionalized with hyaluronic acid. These results indicate that the membranes may be promising for accelerating the healing process of chronic wounds in humans.

Comparative fluorophotometric evaluation of the ocular surface retention time of cross-linked and linear hyaluronic acid ocular eye drops on healthy dogs.

PURPOSE: Evaluate and compare the retention time on the canine ocular surface of crosslinked hyaluronic acid (X-HA), linear hyaluronic acid (L-HA) and saline solution using fluorescent compounds (fluorescein sodium salt, Alexa Fluor 488 cadaverine and Alexa Fluor 488 maleimide). METHODS: 0.9% saline solution (SAL) was combined with fluorescein sodium salt. X-HA and L-HA were covalently modified using Alexa Fluor 488 reactive moieties. Eye drops were applied to 70 eyes of 35 dogs that were previously assessed and determined to have a normal ocular surface. Employing a blue light filter (450-490 nm), digital images were captured from instillation to 180 min. Images were analyzed to assess the percent of the total ocular area covered with green fluorescence at various time points. RESULTS: X-HA exhibited a dual phase behavior: A broad microgel coverage first, followed by accumulation in tear film meniscus and medial canthus in the second phase, remaining in contact with the ocular surface up to 180 min. Coverage with L-HA and SAL eye drops quickly migrated to the tear meniscus. No traces of the fluorescent compounds were observed by 45 min in eyes treated with SAL solution compound and, by 120 min, eyes treated with L-HA. CONCLUSIONS: X-HA exhibited a significantly increased ocular surface contact time with the ocular surface compared with L-HA and SAL. Not only could this indicate extended lubrication time but also supports the potential use of this compound as a method for topical sustained-release drug application.

Role of Hyaluronic acid and its chemical derivatives in immunity during homeostasis, cancer and tissue regeneration.

Over the last few decades, scientists have recognized the critical role that various components of the extracellular matrix (ECM) play in maintaining homeostatic immunity. Besides, dysregulation in the synthesis or degradation levels of these components directly impacts the mechanisms of immune response during tissue injury caused by tumor processes or the regeneration of the tissue itself in the event of damage. ECM is a complex network of protein compounds, proteoglycans and glycosaminoglycans (GAGs). Hyaluronic acid (HA) is one of the major GAGs of this network, whose metabolism is strictly physiologically regulated and quickly altered in injury processes, affecting the behavior of different cells, from stem cells to differentiated immune cells. In this revision we discuss how the native or chemically modified HA interacts with its specific receptors and modulates intra and intercellular communication of immune cells, focusing on cancer and tissue regeneration conditions.

Effect of hyaluronic acid-stabilized silver nanoparticles on lettuce (Lactuca sativa L.) seed germination.

Nanotechnology has brought significant advancements to agriculture through the development of engineered nanomaterials (ENPs). Silver nanoparticles (AgNPs) capped with polysaccharides have been applied in agricultural diagnostics, crop pest management, and seed priming. Hyaluronic acid (HA), a natural polysaccharide with bactericidal properties, has been considered a growth regulator for plant tissues and an inducer of systemic resistance against plant diseases. Additionally, HA has been employed as a stabilizing agent for AgNPs. This study investigated the synthesis and effects of hyaluronic acid-stabilized silver nanoparticles (HA-AgNPs) as a seed priming agent on lettuce (Lactuca sativa L.) seed germination. HA-AgNPs were characterized using several techniques, exhibiting spherical morphology and good colloidal stability. Germination assays conducted with 0.1, 0.04, and 0.02 g/L of HA-AgNPs showed a concentration-dependent reduction in seed germination. Conversely, lower concentrations of HA-AgNPs significantly increased germination rates, survival, tolerance indices, and seed water absorption compared to silver ions (Ag+). SEM/EDS indicated more significant potential for HA-AgNPs internalization compared to Ag+. Therefore, these findings are innovative and open new avenues for understanding the impact of Ag+ and HA-AgNPs on seed germination.

Analysis of the Morphology, Rheology, and Clinical Applicability of a Hybrid Injectable with Hyaluronic Acid and Hydroxyapatite.

BACKGROUND: Treating signs of aging requires skeletal restructuring, facial contour redefinition, and sagging skin treatment. Hence, HarmonyCa® was recently introduced in the market, combining hyaluronic acid and hydroxyapatite. However, there are no studies evaluating the physicochemical properties of this material. PURPOSE: To analyze the morphology, rheology, and clinical applicability of HarmonyCa® over a 180-day follow-up. METHODS: A morphological analysis with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) and rheology measurement with a rheometer. The clinical applicability analysis included a tissue ptosis patient who received the product and was reassessed 30 and 180 days after applying HarmonyCa®. RESULTS: SEM and EDS analyses showed two distinct morphologies related to hydroxyapatite and hyaluronic acid. The rheological measurements of HarmonyCa® showed G' and G″ of 51.56 and 44.01 Pa, respectively. The tan δ value was 0.8503, and G* was 108.1 Pa. The clinical outcomes were satisfactory. CONCLUSION: HarmonyCa® presents a good synergy between hyaluronic acid and hydroxyapatite. Also, the rheological analysis showed moderate viscosity for the product, with a clinical indication for subcutaneous application. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The rheology of injectable hyaluronic acid hydrogels used as facial fillers: A review.

Injectable hyaluronic acid (HA) hydrogels have been popularized in facial aesthetics as they provide a long-lasting effect, low risk of complications, allergenicity tests are not required before application and can be easily removed by the action of hyaluronidases. On the other hand, the development of these systems requires in-depth studies of chemical mechanisms involved in hydrogel formation. Ideal dermal fillers should temporarily fluidize during extrusion through the needle and quickly recover their original shape after application. Hydrogels with more elastic properties, for example, are difficult to inject while viscous materials are too liquid. A balance between both properties should be achieved. Each region of the face requires products with distinct rheological properties. High G' dermal fillers are preferable for deeper wrinkles whereas the counterpart with lower values of G' is more indicated in superficial wrinkles or lip augmentation. Factors such as molecular weight and concentration of HA, pH, type and concentration of the crosslinking agent, particle size, crosslinking reaction time and crosslinking agent/polysaccharide ratio should be modulated to achieve specific rheological properties. In this review, the effect of each variable is discussed in detail to guide the rational development of new dermal fillers.

Electrostimulable polymeric films with hyaluronic acid and lipid nanoparticles for simultaneous topical delivery of macromolecules and lipophilic drugs.

This study focused on developing electrically stimulable hyaluronic acid (HA) films incorporating lipid nanoparticles (NPs) designed for the topical administration of lipophilic drugs and macromolecules. Based on beeswax and medium-chain triglycerides, NPs were successfully integrated into silk fibroin/chitosan films containing HA (NP-HA films) at a density of approximately 1011 NP/cm2, ensuring a uniform distribution. This integration resulted in a 40% increase in film roughness, a twofold decrease in Young's modulus, and enhanced film flexibility and bioadhesion work. The NP-HA films, featuring Ag/AgCl electrodes, demonstrated the capability to conduct a constant electrical current of 0.2 mA/cm2 without inducing toxicity in keratinocytes and fibroblasts during a 15-min application. Moreover, the NPs facilitated the homogeneous distribution of lipophilic drugs within the film, effectively transporting them to the skin and uniformly distributing them in the stratum corneum upon film administration. The sustained release of HA from the films, following Higuchi kinetics, did not alter the macroscopic characteristics of the film. Although anodic iontophoresis did not noticeably affect the release of HA, it did enhance its penetration into the skin. This enhancement facilitated the permeation of HA with a molecular weight (MW) of up to 2 × 105 through intercellular and transcellular routes. Confocal Raman spectroscopy provided evidence of an approximate 100% increase in the presence of HA with a MW in the range of 1.5-1.8 × 106 in the viable epidermis of human skin after only 15 min of iontophoresis applied to the films. Combining iontophoresis with NP-HA films exhibits substantial potential for noninvasive treatments focused on skin rejuvenation and wound healing.

In Situ Photo-crosslinkable Hyaluronic Acid/Gelatin Hydrogel for Local Nitric Oxide Delivery.

An increasing number of studies have shown that the local release of nitric oxide (NO) from hydrogels stimulates tissue regeneration by modulating cell proliferation, angiogenesis, and inflammation. The potential biomedical uses of NO-releasing hydrogels can be expanded by enabling their application in a fluid state, followed by controlled gelation triggered by an external factor. In this study, we engineered a hydrogel composed of methacrylated hyaluronic acid (HAGMA) and thiolated gelatin (GELSH) with the capacity for in situ photo-cross-linking, coupled with localized NO release. To ensure a gradual and sustained NO release, we charged the hydrogels with poly(l-lactic-co-glycolic acid) (PLGA) nanoparticles functionalized with S-nitrosoglutathione (GSNO), safeguarding SNO group integrity during photo-cross-linking. The formation of thiol-ene bonds via the reaction between GELSH's thiol groups and HAGMA's vinyl groups substantially accelerated gelation (by a factor of 6) and increased the elastic modulus of hydrated hydrogels (by 1.9-2.4 times). HAGMA/GELSH hydrogels consistently released NO over a 14 day duration, with the release of NO depending on the hydrogels' equilibrium swelling degree, determined by the GELSH-to-HAGMA ratio. Biocompatibility assessments confirmed the suitability of these hydrogels for biological applications as they display low cytotoxicity and stimulated fibroblast adhesion and proliferation. In conclusion, in situ photo-cross-linkable HAGMA/GELSH hydrogels, loaded with PLGA-GSNO nanoparticles, present a promising avenue for achieving localized and sustained NO delivery in tissue regeneration applications.

Anatomy, molecular structures, and hyaluronic acid - Gelatin injectable hydrogels as a therapeutic alternative for hyaline cartilage recovery: A review.

Cartilage damage caused by trauma or osteoarthritis is a common joint disease that can increase the social and economic burden in society. Due to its avascular characteristics, the poor migration ability of chondrocytes, and a low number of progenitor cells, the self-healing ability of cartilage defects has been significantly limited. Hydrogels have been developed into one of the most suitable biomaterials for the regeneration of cartilage because of its characteristics such as high-water absorption, biodegradation, porosity, and biocompatibility similar to natural extracellular matrix. Therefore, the present review article presents a conceptual framework that summarizes the anatomical, molecular structure and biochemical properties of hyaline cartilage located in long bones: articular cartilage and growth plate. Moreover, the importance of preparation and application of hyaluronic acid - gelatin hydrogels for cartilage tissue engineering are included. Hydrogels possess benefits of stimulating the production of Agc1, Col2α1-IIa, and SOX9, molecules important for the synthesis and composition of the extracellular matrix of cartilage. Accordingly, they are believed to be promising biomaterials of therapeutic alternatives to treat cartilage damage.

Hyaluronic acid-conjugated liposomes loaded with dexamethasone: A promising approach for the treatment of inflammatory diseases.

Dexamethasone is a well-known anti-inflammatory drug readily used to treat many lung diseases. However, its side effects and poor lower airway deposition and retention are significant limitations to its usage. In this work, we developed lipid nanoparticulate platforms loaded with dexamethasone and evaluated their behavior in inflammatory lung models in vitro and in vivo. Dexamethasone-loaded liposomes with an average diameter below 150 nm were obtained using a solvent injection method. Three different formulations were produced with a distinct surface coating (polyethylene glycol, hyaluronic acid, or a mixture of both) as innovative strategies to cross the pulmonary mucus layer and/or target CD44 expressed on alveolar proinflammatory macrophages. Interestingly, while electron paramagnetic spectroscopy showed that surface modifications did not induce any molecular changes in the liposomal membrane, drug loading analysis revealed that adding the hyaluronic acid in the bilayer led to a decrease of dexamethasone loading (from 3.0 to 1.7 w/w%). In vitro experiments on LPS-activated macrophages demonstrated that the encapsulation of dexamethasone in liposomes, particularly in HA-bearing ones, improved its anti-inflammatory efficacy compared to the free drug. Subsequently, in vivo data revealed that while intratracheal administration of free dexamethasone led to an important inter-animals variation of efficacy, dexamethasone-loaded liposomes showed an improved consistency within the results. Our data indicate that encapsulating dexamethasone into lipid nanoparticles is a potent strategy to improve its efficacy after lung delivery.

Proteoglycans: A Tool for Detecting Hyaluronan by ELISA-Like Methods.

Hyaluronan is a non-sulfated glycosaminoglycan synthesized on the plasma membrane of almost all mammalian cells, which can interact with different proteoglycans of the extracellular matrix. Aggrecan, versican, neurocan, and brevican are proteoglycans whose structures present a specific protein domain called "link module," which allows hyaluronan binding. Therefore, they can be helpful for assays that detect hyaluronan. For example, ELISA-like methods developed to measure hyaluronan amounts in solution are based on specific interactions between this molecule and the link module present in aggrecan or other hyaluronan-binding proteins (hyaladherins).

Supramolecular structure organization and rheological properties modulate the performance of hyaluronic acid-loaded thermosensitive hydrogels as drug-delivery systems.

The challenges for developing new pharmaceutical formulations based on natural and synthetic polymers has led to innovation into the design of systems responsive environmental stimuli such as temperature. However, the presence of hydrophilic or hydrophobic molecules, charged groups, or metallic elements can affect their structural behavior and their biopharmaceutical performance This work aims to study and characterize the morphology and structure of polymeric formulations based on Poloxamer (PL) 407 (15 % and 30 % m/v) and its binary with PL 338 (15 % PL 407 + 15 % PL 338) and hyaluronic acid (0.5 % m/v), as drug delivery systems of local anesthetic bupivacaine (0.5 % m/v) and ropivacaine (0.5 % m/v) hydrochloride. For this, it was performed SANS analysis for determination of supramolecular organization and lattice parameters; calorimetry was done to characterize their thermodynamic parameters; rheological analysis flow curve, consistency and adhesion calculation, Maxwell model study. Also, it was performed drug release profiles and calculation of diffusion coefficients. It was identified lamellar structures in PL 407 15 % formulations, and coexistence of cubic and hexagonal phases in PL 407 30 % and binary formulations, however hyaluronic acid, bupivacaine or ropivacaine seem do not affect the type of supramolecular structure. In addition, these additives can modulate viscosity among poloxamers chains, increasing micelle-micelle interactions as it happens in presence of bupivacaine. On the other hand, addition of hyaluronic acid can promote increased structural stabilization by hydrophilic interactions between hyaluronic and micellar corona. It reflects the ability how to control the drug release, as in case of binary system that retained bupivacaine for longer time than other systems, as well it happens when hyaluronic acid is added in PL 407 15 % and PL 407 30 %.

The effects of sulfated hyaluronan in breast, lung and colorectal carcinoma and monocytes/macrophages cells: Its role in angiogenesis and tumor progression.

Hyaluronan (HA) is a component of the extracellular matrix (ECM) it is the main non-sulfated glycosaminoglycan able to modulate cell behavior in the healthy and tumor context. Sulfated hyaluronan (sHA) is a biomaterial derived from chemical modifications of HA, since this molecule is not naturally sulfated. The HA sulfation modifies several properties of the native molecule, acquiring antitumor properties in different cancers. In this study, we evaluated the action of sHA of ~30-60 kDa with different degrees of sulfation (0.7 sHA1 and 2.5 sHA3) on tumor cells of a breast, lung, and colorectal cancer model and its action on other cells of the tumor microenvironment, such as endothelial and monocytes/macrophage cells. Our data showed that in breast and lung tumor cells, sHA3 is able to modulate cell viability, cytotoxicity, and proliferation, but no effects were observed on colorectal cancer cells. In 3D cultures of breast and lung cancer cells, sHA3 diminished the size of the tumorsphere and modulated total HA levels. In these tumor models, treatment of monocytes/macrophages with sHA3 showed a downregulation of the expression of angiogenic factors. We also observed a decrease in endothelial cell migration and modulation of the hyaluronan-binding protein TSG-6. In the breast in vivo xenograft model, monocytes/macrophages preincubated with sHA1 or sHA3 decreased tumor vasculature, TSG-6 and HA levels. Besides, in silico analysis showed an association of TSG-6, HAS2, and IL-8 with biological processes implicated in the progression of the tumor. Taken together, our data indicate that sHA in a breast and lung tumor context is able to induce an antiangiogenic action on tumor cells as well as in monocytes/macrophages (Mo/MØ) by modulation of endothelial migration, angiogenic factors, and vessel formation.

Polysaccharide-based layer-by-layer nanoarchitectonics with sulfated chitosan for tuning anti-thrombogenic properties.

The development of blood-interacting surfaces is critical to fabricate biomaterials for medical use, such as prostheses, implants, biosensors, and membranes. For instance, thrombosis is one of the leading clinical problems when polymer-based materials interact with blood. To overcome this limitation is necessary to develop strategies that limit platelets adhesion and activation. In this work, hyaluronan (HA)/chitosan (Chi) based-films, recently reported in the literature as platforms for tumor cell capture, were developed and, subsequently, functionalized with sulfated chitosan (ChiS) using a layer-by-layer technique. ChiS, when compared to native Chi, presents the unique abilities to confer anti-thrombogenic properties, to reduce protein adsorption, and also to limit calcification. Film physicochemical characterization was carried out using FTIR and XPS for chemical composition assessment, AFM for the surface morphology, and contact angle for hydrophilicity evaluation. The deposition of ChiS monolayer promoted a decrease in both roughness and hydrophilicity of the HA/Chi films. In addition, the appearance of sulfur in the chemical composition of ChiS-functionalized films confirmed the film modification. Biological assay indicated that the incorporation of sulfated groups limited platelet adhesion, mainly because a significant reduction of platelets adhesion to ChiS-functionalized films was observed compared to HA/Chi films. On balance, this work provides a new insight for the development of novel antithrombogenic biomaterials, opening up new possibilities for devising blood-interaction surfaces.

Features to consider for mimicring tissues in orofacial aesthetics with optimal balance technology and non-animal stabilized hyaluronic acid (Restylane®): The MIMT concept.

Nonsurgical cosmetic treatments have significantly increased over the last decade. Therefore, this study aims to review the features that should be considered in orofacial esthetic procedures, thorough of a proposal of a new concept called the tissue mimicry concept (MIMT concept) and filling techniques. The MIMT concept described in this article comprises knowledge about anatomy of the face and associated structures, understanding of aging and how this process affects the facial tissues interactions (skin, subcutaneous tissues, muscles, and bones), interpretation of facial analysis, comprehension of dermal fillers characteristics and discernment of the correct filling technique for each region. Based on these variables the MIMT concept proposes the implantation of the minimum-effective quantity of acid hyaluronic fillers (HA) with different physical, chemical and rheological properties (complex viscosity and elastic modulus) in the correct layers; in order to optimize their performance resulting in a natural appearance with fewer risks of adverse events. the versatility, acceptable safety profile, biocompatibility and greater patient compliance presented in the Restylane® line (by Galderma) should be taken in consideration, since the use of a proper HA is noteworthiness. The Non-Animal Stabilized Hyaluronic Acid Tecnology (NASHA®) and the Optimal Balance Technology (OBT®), which make up this line of fillers, allow us to have very firm to very flexible gels, with different particle sizes, with an optimal concentration of HA and with viscoelastic and biocompatible characteristics according to the region of the treated face.

Hybrid Methacrylated Gelatin and Hyaluronic Acid Hydrogel Scaffolds. Preparation and Systematic Characterization for Prospective Tissue Engineering Applications.

Hyaluronic acid (HA) and gelatin (Gel) are major components of the extracellular matrix of different tissues, and thus are largely appealing for the construction of hybrid hydrogels to combine the favorable characteristics of each biopolymer, such as the gel adhesiveness of Gel and the better mechanical strength of HA, respectively. However, despite previous studies conducted so far, the relationship between composition and scaffold structure and physico-chemical properties has not been completely and systematically established. In this work, pure and hybrid hydrogels of methacroyl-modified HA (HAMA) and Gel (GelMA) were prepared by UV photopolymerization and an extensive characterization was done to elucidate such correlations. Methacrylation degrees of ca. 40% and 11% for GelMA and HAMA, respectively, were obtained, which allows to improve the hydrogels' mechanical properties. Hybrid GelMA/HAMA hydrogels were stiffer, with elastic modulus up to ca. 30 kPa, and porous (up to 91%) compared with pure GelMA ones at similar GelMA concentrations thanks to the interaction between HAMA and GelMA chains in the polymeric matrix. The progressive presence of HAMA gave rise to scaffolds with more disorganized, stiffer, and less porous structures owing to the net increase of mass in the hydrogel compositions. HAMA also made hybrid hydrogels more swellable and resistant to collagenase biodegradation. Hence, the suitable choice of polymeric composition allows to regulate the hydrogels´ physical properties to look for the most optimal characteristics required for the intended tissue engineering application.

Structure and Fate of Nanoparticles Designed for the Nasal Delivery of Poorly Soluble Drugs.

Nanoparticles are promising mediators to enable nasal systemic and brain delivery of active compounds. However, the possibility of reaching therapeutically relevant levels of exogenous molecules in the body is strongly reliant on the ability of the nanoparticles to overcome biological barriers. In this work, three paradigmatic nanoformulations vehiculating the poorly soluble model drug simvastatin were addressed: (i) hybrid lecithin/chitosan nanoparticles (LCNs), (ii) polymeric poly-ε-caprolactone nanocapsules stabilized with the nonionic surfactant polysorbate 80 (PCL_P80), and (iii) polymeric poly-ε-caprolactone nanocapsules stabilized with a polysaccharide-based surfactant, i.e., sodium caproyl hyaluronate (PCL_SCH). The three nanosystems were investigated for their physicochemical and structural properties and for their impact on the biopharmaceutical aspects critical for nasal and nose-to-brain delivery: biocompatibility, drug release, mucoadhesion, and permeation across the nasal mucosa. All three nanoformulations were highly reproducible, with small particle size (∼200 nm), narrow size distribution (polydispersity index (PI) < 0.2), and high drug encapsulation efficiency (>97%). Nanoparticle composition, surface charge, and internal structure (multilayered, core-shell or raspberry-like, as assessed by small-angle neutron scattering, SANS) were demonstrated to have an impact on both the drug-release profile and, strikingly, its behavior at the biological interface. The interaction with the mucus layer and the kinetics and extent of transport of the drug across the excised animal nasal epithelium were modulated by nanoparticle structure and surface. In fact, all of the produced nanoparticles improved simvastatin transport across the epithelial barrier of the nasal cavity as compared to a traditional formulation. Interestingly, however, the permeation enhancement was achieved via two distinct pathways: (a) enhanced mucoadhesion for hybrid LCN accompanied by fast mucosal permeation of the model drug, or (b) mucopenetration and an improved uptake and potential transport of whole PCL_P80 and PCL_SCH nanocapsules with delayed boost of permeation across the nasal mucosa. The correlation between nanoparticle structure and its biopharmaceutical properties appears to be a pivotal point for the development of novel platforms suitable for systemic and brain delivery of pharmaceutical compounds via intranasal administration.

Development of a chitosan and hyaluronic acid hydrogel with potential for bioprinting utilization: A preliminary study.

Bioprinting is a technique that has been applied in the areas of tissue engineering and regenerative medicine (TERM). Natural polymer-based hydrogels are known for their favorable biocompatible properties, as well as attractive biomaterials for cell encapsulation. These hydrogels provide an aqueous three-dimensional environment with biologically relevant chemical and physical signals, mimicking the natural environment of the extracellular matrix (ECM). Chitosan (CHI) and hyaluronic acid (HA) have been widely researched for biomedical applications. Bioinks are "ink" formulations, usually hydrogels, that allow the printing of living cells. This work proposes the development of a low cost and simple chitosan CHI-AH hydrogel with potential to become a bioink. At physiological temperature, the biomaterials form a hydrogel. The material developed was characterized by the analysis of morphology, cytotoxicity, and cell viability. FTIR showed the characteristic vibrational bands of chitosan and HA. No difference in swelling was observed between the different formulations studied, although SEM showed architectural differences between the hydrogels obtained. Extract cytotoxicity testing showed that the hydrogel is not cytotoxic. The direct toxicity test also revealed the absence of toxicity, but the cells had difficulty migrating into the gel, probably because of its density. These data were confirmed by SEM. Further testing are ongoing to better understand the gel's characteristics to improve the limitations found so far.

Synthetic Studies on the Incorporation of N-Acetylallosamine in Hyaluronic Acid-Inspired Thiodisaccharides.

Two approaches for the synthesis of the thiodisaccharide ß-S-GlcA(1→3)ß-S-AllNAc are described here. The target disaccharide was a C-3 epimer and thio-analogue of the hyaluronic acid repetitive unit, tuned with a thiopropargyl anomeric group for further click conjugation. Thus, we analysed and tested two convenient sequences, combining the two key steps required to introduce the thioglycosidic bonds and consequently reach the target molecule: the SN2 substitution of a good leaving group (triflate) present at C-3 of a GlcNAc derivative and the introduction of the anomeric thiopropargyl substituent. The use of a 2-azido precursor showed to be a convenient substrate for the SN2 step. Nevertheless, further protecting group manipulation and the introduction of the thiopropargyl anomeric residue were then required. This approach showed to provide access to a variety of thiodisaccharide derivatives as interesting building blocks for the construction of neoglycoconjugates.

Targeted clindamycin delivery to pilosebaceous units by chitosan or hyaluronic acid nanoparticles for improved topical treatment of acne vulgaris.

We developed chitosan or hyaluronic acid nanoparticles to entrap clindamycin and evaluated for the first time the impact of these two polymeric nanosystems on the targeted drug delivery to the pilosebaceous units, considering the sebaceous characteristics of skin affected by acne. Chitosan and hyaluronic acid nanoparticles respectively presented diameters of 362 ± 19 nm and 417 ± 9 nm (PDI < 0.47), entrapped 42 % and 48 % of the clindamycin content (drug loading of 8.8 % and 0.5 %) and had opposite surface charges (+27.7 ± 0.9 mV and -30.2 ± 2.7 mV). Although only the hyaluronic acid nanoparticles showed increased deposition of the drug into the pilosebaceous structures, both nanoparticles revealed enhanced targeted delivery of clindamycin to these structures as compared to commercial formulation (53 ± 20 % and 77 ± 9% of the total drug that penetrated the skin was found on the pilosebaceous units from, respectively, chitosan and hyaluronic acid nanoparticles). Remarkably, the "targeting potential" of the nanoparticles was more pronounced when the skin was pretreated to simulate a sebaceous condition. In conclusion, both polymeric nanocarriers targeted drug delivery to the pilosebaceous structures at different extensions and, in the case of oily skin conditions, such targeting was increased.