Hyaluronic Acid Hydrogel Scaffold Research Articles

Chlorogenic acid/carboxymethyl chitosan nanoparticle-assisted biomultifunctional hyaluronic acid-based hydrogel scaffolds for burn skin repair

Burns are a prevalent type of injury worldwide, affecting tens of millions of people each year and significantly impacting the physical and psychological well-being of patients. Consequently, prompt treatment of burn wounds is imperative, with oxidative stress and excessive inflammation identified as primary factors contributing to delayed healing. In recent years, there has been growing interest in in situ crosslinked multifunctional hydrogels as a minimally invasive approach for personalized treatment delivery. To address these, a photocrosslinkable methacryloyl hyaluronic acid hydrogel scaffold embedded with chlorogenic acid/carboxymethyl chitosan nanoparticles (CGA/CMCS-HAMA, CCH), was developed for the treatment of burn wounds. The hydrogel prepared degraded by over 50 % by day 20, demonstrating stability and meeting the therapeutic requirements for burn wounds. Leveraging the extracellular matrix-like properties of HAMA and the antioxidant capabilities of CGA/CMCS NPs, this hydrogel demonstrates the ability to locally and continuously scavenge ROS and inhibit lipid peroxidation, inhibiting ferroptosis. Moreover, hydrogels well modulate the expression of macrophage- and fibroblast-associated inflammatory factors. Additionally, the hydrogel promotes cell adhesion and migration, further supporting the healing process. Overall, this innovative approach offers a safe and promising solution for burn wound treatment, addressing drug breakthrough and safety concerns while being adaptable to various irregular wound types.

Hyaluronic Acid Hydrogel Combined With Ocimum sanctum and Tendon-Derived Extracellular Matrix Enhances Tenogenesis in Periodontal Ligament Stem Cells.

Background Ocimum sanctum (OS) is a medicinal plant with antioxidant, anti-cancer, anti-diabetic, antimicrobial, and anti-inflammatory activities. Extracellular matrix (ECM) maintains the structural stability of tissues. Hyaluronic acid (HA), which is used in hydrogel fabrication and osteochondral regeneration, increases cell viability and the expression of marker genes. Periodontal ligament stem cells (PDLSC), which are a type of mesenchymal stem cells (MSC), have self-renewing capacity and they prevent teratoma formationand promote tendon (TEN) regeneration. The aim of this study is to incorporate the phytochemical effects of Ocimum sanctuminto hyaluronic acid hydrogel scaffolds made with the MSCs in tendon ECM for increased tissue regeneration. Materials & methods Ocimum sanctum extract and methacrylated hyaluronic acid (HA-MA) were prepared. An ovine tendon sample was decellularised to obtain the ECM. The study groups of HA, TEN, HA_OS, HA_TEN, and HA_OS_TEN were prepared. The presence of tendon cells was confirmed by picrosirius red staining and the hydrogel scaffolds were analysed using scanning electron microscopy (SEM), swelling, differentiation, compression, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) compatibility analyses. Results The morphology of the samples was analysed by SEM analysis. The HA_OS_TEN sample showed the highest rate of tenogenesis, lowest swelling, high cell viability and differentiation, and optimal compression rates. Conclusion This study showed that hyaluronic acid combined with Ocimum sanctumand tendon ECM is a very good conjugation for the preparation of hydrogel scaffolds for tendon tissue regeneration using MSCs.

3D-printed hyaluronic acid hydrogel scaffolds impregnated with neurotrophic factors (BDNF, GDNF) for post-traumatic brain tissue reconstruction.

Brain tissue reconstruction posttraumatic injury remains a long-standing challenge in neurotransplantology, where a tissue-engineering construct (scaffold, SC) with specific biochemical properties is deemed the most essential building block. Such three-dimensional (3D) hydrogel scaffolds can be formed using brain-abundant endogenous hyaluronic acid modified with glycidyl methacrylate by employing our proprietary photopolymerisation technique. Herein, we produced 3D hyaluronic scaffolds impregnated with neurotrophic factors (BDNF, GDNF) possessing 600 kPa Young’s moduli and 336% swelling ratios. Stringent in vitro testing of fabricated scaffolds using primary hippocampal cultures revealed lack of significant cytotoxicity: the number of viable cells in the SC+BDNF (91.67 ± 1.08%) and SC+GDNF (88.69 ± 1.2%) groups was comparable to the sham values (p > 0.05). Interestingly, BDNF-loaded scaffolds promoted the stimulation of neuronal process outgrowth during the first 3 days of cultures development (day 1: 23.34 ± 1.46 µm; day 3: 37.26 ± 1.98 µm, p < 0.05, vs. sham), whereas GDNF-loaded scaffolds increased the functional activity of neuron-glial networks of cultures at later stages of cultivation (day 14) manifested in a 1.3-fold decrease in the duration coupled with a 2.4-fold increase in the frequency of Ca2+ oscillations (p < 0.05, vs. sham). In vivo studies were carried out using C57BL/6 mice with induced traumatic brain injury, followed by surgery augmented with scaffold implantation. We found positive dynamics of the morphological changes in the treated nerve tissue in the post-traumatic period, where the GDNF-loaded scaffolds indicated more favorable regenerative potential. In comparison with controls, the physiological state of the treated mice was improved manifested by the absence of severe neurological deficit, significant changes in motor and orienting-exploratory activity, and preservation of the ability to learn and retain long-term memory. Our results suggest in favor of biocompatibility of GDNF-loaded scaffolds, which provide a platform for personalized brain implants stimulating effective morphological and functional recovery of nerve tissue after traumatic brain injury.

Engineering Natural Pollen Grains as Multifunctional 3D Printing Materials

AbstractThe development of multifunctional 3D printing materials from sustainable natural resources is a high priority in additive manufacturing. Using an eco‐friendly method to transform hard pollen grains into stimulus‐responsive microgel particles, we engineered a pollen‐derived microgel suspension that can serve as a functional reinforcement for composite hydrogel inks and as a supporting matrix for versatile freeform 3D printing systems. The pollen microgel particles enabled the printing of composite inks and improved the mechanical and physiological stabilities of alginate and hyaluronic acid hydrogel scaffolds for 3D cell culture applications. Moreover, the particles endowed the inks with stimulus‐responsive controlled release properties. The suitability of the pollen microgel suspension as a supporting matrix for freeform 3D printing of alginate and silicone rubber inks was demonstrated and optimized by tuning the rheological properties of the microgel. Compared with other classes of natural materials, pollen grains have several compelling features, including natural abundance, renewability, affordability, processing ease, monodispersity, and tunable rheological features, which make them attractive candidates to engineer advanced materials for 3D printing applications.

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.

PREPARATION, CHARACTERIZATION AND OSTEOGENIC POTENTIAL OF AN INJECTABLE PHOTO-CURABLE HYALURONIC ACID HYDROGEL SCAFFOLD LOADED WITH BIOACTIVE NANO-HYDROXYAPATITE.

Introduction: In-situ photo-cured hydrogels for bone regeneration offer an advantage compared to solid scaffolds or membranes is that it can be used by minimally invasive techniques and can fill irregularly shaped defects easily. Objective: was to prepare an injectable photo-curable hyaluronic acid hydrogel scaffold loaded with bioactive nano-hydroxyapatite using riboflavin as a natural source photoinitiator for bone regeneration and to investigate the effect of addition of nano-hydroxyapatite on the physiochemical and mechanical properties of the prepared hydrogel. Also, the osteogenic potential of the prepared hydrogels was assessed in a rabbit model. Materials and methods: Two groups were prepared, (Group I) photo-cured hyaluronic acid as a control group and (Group II) photo-cured hyaluronic acid/nano-hydroxyapatite. Laboratory characterization tests: FTIR, XRD, SEM, mechanical, swelling and degradation rate tests were performed. Cell viability % using the MTT assay was used to assess the biocompatibility. In vivo bioactivity was assessed in a rabbit model and histomorphometric analysis was done. Results: Statistical analysis of results revealed that the addition of nano-hydroxyapatite increased significantly the mechanical properties of the hydrogels. SEM images demonstrated that the addition of nano-hydroxyapatite caused the formation of inter-connected pores. MTT assay showed that hydrogel extract didn’t affect cell viability after 48h. Histomorphometric analysis results revealed that the photo-cured (GMA-HA/HAP) hydrogel increased the osteogenic potential by one and a half folds compared to the control group and this proved its bioactivity. Conclusion: Results suggest that the prepared photo-cured hyaluronic hydrogel is a promising biomaterial to deliver bioactive nano-hydroxyapatite and has an osteogenic potential.

Hyaluronic acid hydrogel scaffolds loaded with cationic niosomes for efficient non-viral gene delivery.

The lack of ideal non-viral gene carriers has motivated the combination of delivery systems and tissue-engineered scaffolds, which may offer relevant advantages such as enhanced stability and reduced toxicity. In this work, we evaluated a new combination between niosome non-viral vectors and hyaluronic acid (HA) hydrogel scaffolds, both widely studied due to their biocompatibility as well as their ability to incorporate a wide variety of molecules. We evaluated three different niosome formulations (niosomes 1, 2 and 3) varying in composition of cationic lipid, helper lipid and non-ionic tensioactives. Niosomes and nioplexes obtained upon the addition of plasmid DNA were characterized in terms of size, polydispersity, zeta potential and ability to transfect mouse bone marrow cloned mesenchymal stem cells (mMSCs) in 2D culture. Niosome 1 was selected for encapsulation in HA hydrogels due to its higher transfection efficiency and the formulation was concentrated in order to be able to incorporate higher amounts of DNA within HA hydrogels. Nioplex-loaded HA hydrogels were characterized in terms of biomechanical properties, particle distribution, nioplex release kinetics and ability to transfect encapsulated mMSCs in 3D culture. Our results showed that nioplex-loaded HA hydrogel scaffolds presented little or no particle aggregation, allowed for extensive cell spreading and were able to efficiently transfect encapsulated mMSCs with high cellular viability. We believe that the knowledge gained through this in vitro model can be utilized to design novel and effective platforms for in vivo local and non-viral gene delivery applications.

Retention of Human-Induced Pluripotent Stem Cells (hiPS) With Injectable HA Hydrogels for Vocal Fold Engineering.

One prospective treatment option for vocal fold scarring is regeneration with an engineered scaffold containing induced pluripotent stem cells (iPS). In the present study, we investigated the feasibility of utilizing an injectable hyaluronic acid (HA) scaffold encapsulated with human-iPS cell (hiPS) for regeneration of vocal folds. Thirty athymic nude rats underwent unilateral vocal fold injury. Contralateral vocal folds served as uninjured controls. Hyaluronic acid hydrogel scaffold, HA hydrogel scaffold containing hiPS, and HA hydrogel scaffold containing hiPS with epidermal growth factor (EGF) were injected in both vocal folds immediately after surgery. One and 2 weeks after injection, larynges were excised for histology, immunohistochemistry, and fluorescence in situ hybridization (FISH). Presence of HA hydrogel was confirmed in vocal folds 1 and 2 weeks post injection. The FISH analysis confirmed the presence and viability of hiPS in the injected vocal folds. Histological results demonstrated that vocal folds injected with HA hydrogel scaffold containing EGF demonstrated less fibrosis than those with HA hydrogel only. Human-iPS survived in injured rat vocal folds. The HA hydrogel with hiPS and EGF ameliorated the fibrotic response. Additional work is necessary to optimize hiPS differentiation and further confirm the safety of hiPS for clinical applications.

Restoration of ovarian tissue function and estrous cycle in rat after autotransplantation using hyaluronic acid hydrogel scaffold containing VEGF and bFGF

This study investigates the effect of hyaluronic acid (HA) containing VEGF and bFGF on restoration of ovarian function after ovarian autotransplantation. Twenty-four rats were randomly divided into three groups for ovarian autotransplantation: group A (ovaries without HA, VEGF and bFGF), group B (ovaries encapsulated with HA) and group C (ovaries encapsulated with HA containing VEGF and bFGF). The grafts were assessed using vaginal smears, histological, hormonal, and the genes expression analysis. The duration of first estrous cycle was shorter in group C than in group A (p < 0.01). The mean number of primordial follicles was protected in group C. The level of estradiol was higher in group A than in group C (p < 0.01). The expression level of Cellular-Myelocytomatosis (C-Myc) in group C was lower than in group B (p < 0.05). HA containing VEGF and bFGF can ensure follicular survival, decrease apoptosis and recover ovarian function after auto-transplantation.

Hyaluronic acid hydrogel scaffolds with a triple degradation behavior for bone tissue engineering

In this study, in order to better mimick the nature of bone extracellular matrix, hyaluronic acid (HA) hydrogels having a triple degradation behavior were synthesized from 3,3′-dithiodipropionate hydrazide-modified HA (DTPH–HA) and polyethylene glycol dilevulinate (LEV–PEG–LEV) via the reaction of the ketone carbonyl groups of LEV–PEG–LEV with the hydrazide groups of DTPH–HA. The HA hydrogels were characterized by solid state 13C NMR, FT-IR, SEM, and rheological, swelling and degradation tests. The results showed that the HA hydrogels exhibited a highly porous morphology and had pore diameters ranging from 20 to 200μm. The equilibrium swelling ratio of the HA hydrogels was no less than 37.5. The HA hydrogels could be degraded by hyaluronidase and reducing substances or at acidic pH values. The biocompatibility of the HA hydrogels was evaluated using osteoblast-like MC3T3-E1 cells by live/dead staining and MTT assays. The results revealed that the HA hydrogels had good biocompatibility and could support the attachment and proliferation of MC3T3-E1 cells. All the results indicated that the HA hydrogels synthesized by hydrazone bond crosslinking might have great potential to be used in bone tissue engineering.

In Vitro Epithelial Differentiation of Human Induced Pluripotent Stem Cells for Vocal Fold Tissue Engineering

We determined the feasibility and optimization of differentiating human induced pluripotent stem cells (hiPS) into nonkeratinized stratified squamous epithelial cells for vocal fold engineering. hiPS were cultured and assessed for differentiation in 3 conditions: a 3-dimensional (3D) hyaluronic acid (HA) hydrogel scaffold, a 3D HA hydrogel scaffold with epidermal growth factor (EGF), and a 3D HA hydrogel scaffold cocultured with human vocal fold fibroblasts (hVFF). After 1, 2, and 4 weeks of cultivation, hiPS were selected for histology, immunohistochemistry, and/or transcript expression analysis. At 4 weeks, hiPS cultivated with hVFF or with EGF had significantly decreased levels of Oct 3/4, indicating loss of pluripotency. Immunofluorescence revealed the presence of pancytokeratin and of cytokeratin (CK) 13 and 14 epithelial-associated proteins at 4 weeks after cultivation in hiPS EGF and hiPS hVFF cultures. The transcript expression level of CK14 was significantly increased for hiPS hVFF cultures only and was measured concomitantly with cell morphology that was clearly cohesive and displayed a degree of nuclear polarity suggestive of epithelial differentiation. We found that hiPS cultivated in 3D HA hydrogel with hVFF demonstrated the most robust conversion evidence to date of epithelial differentiation. Further work is necessary to focus on amplification of these progenitors for application in vocal fold regenerative biology.

A novel in vivo model for evaluating functional restoration of a tissue-engineered salivary gland

To create a novel model for development of a tissue-engineered salivary gland from human salivary gland cells that retains progenitor cell markers useful for treatment of radiation-induced xerostomia. A three-dimensional (3D) hyaluronic acid (HA)-based hydrogel scaffold was used to encapsulate primary human salivary gland cells and to obtain organized acini-like spheroids. Hydrogels were implanted into rat models, and cell viability and receptor expression were evaluated. A parotid gland surgical resection model for xenografting was developed. Salivary cells loaded in HA hydrogels formed spheroids and in vitro were implanted in the three-fourths resected parotid bed of athymic rats. Implants were removed after 1 week and analyzed for spheroid viability and phenotype retention. Spheroids in 3D stained positive for HA receptors CD168/RHAMM and CD44, which is also a progenitor cell marker. The parotid gland three-fourths resection model was well-tolerated by rodent hosts, and the salivary cell/hydrogel scaffolds were adherent to the remaining parotid gland, with no obvious signs of inflammation. A majority of human cells in the extracted hydrogels demonstrated robust expression of CD44. A 3D HA-based hydrogel scaffold that supported long-term culture of salivary gland cells into organized spheroids was established. An in vivo salivary gland resection model was developed that allowed for integration of the 3D HA hydrogel scaffold with the existing glandular parenchyma. The expression of CD44 among salivary cultures may partially explain their regenerative potential, and the expression of CD168/RHAMM along with CD44 may aid the development of these 3D spheroids into regenerated salivary glands. NA.

Micro-Lithographic Fabrication of Collagen and Hyaluronic Acid Hydrogel Scaffolds

The regeneration of human diseased parts is based on substantial cell number to support physiological functions of diseased tissues/organs. To this end, the scaffolds for cellular proliferation should be structurally similar to normal tissues. This study aimed to fabricate biomimetic structures of naturally-occurring polymer. We utilized micro-lithography to produce three-dimensional scaffold of the composite of collagen and hyaluronic acid (HA) which is further used to evaluate the cellular attachment and proliferation. Collagen from porcine skin was characterized by SDS-PAGE that three species having molecular weights of 120, 130 and 250 kDa were assigned as 2, 1 and  chains of type I collagen. HA was purified by diafiltration and characterized by carbzaole method. The purity of HA was increased from 41.6 g/mL to 71.9 g/mL. To endow photo-cross linker to HA, a graft reaction, catalyzed by triethyl amine was carried out that glycidyl methacrylate (GM) was conjugated to side group of HA. Chemical shifts of 5.7 and 6.1 ppm of 1H NMR spectrum indicated that GMHA was synthesized. To develop 3D scaffolds, we formulated a weight ratio of 10:3 for GMHA and collagen as precursor of micro-lithography. Photo masks of curved, fine lines and rectangular patterns were utilized. For finest lines (100 m) in the pattern, it took 9 minutes to fully crosslink the formulation with UV light, whereas curved lines of 2 to 5 mm could be cross linked in 2 minutes. The scaffolds were found to have pores of 10- 100 m observed under scanning electron microscope. This study completed the scaffold fabrication of naturally-occurring polymers and confirmed the optimized conditions of micro-lithography. The 3D scaffolds having linear and curved lines and rectangular patterns will be used to evaluate the cellular attachment and migration of various mammalian cells.

Latent TGF‐β Hydrogels for Cartilage Tissue Engineering

A biomimetic delivery strategy for transforming growth factor beta (TGF-β) is described, in which TGF-β is presented in a latent form (the small latent complex, SLC), which is inactive until modified by the actions of the cells. In this work, SLC is tethered to a hyaluronic acid hydrogel scaffold to enhance in vitro chondrogenesis.

Combination of hyaluronic acid hydrogel scaffold and PLGA microspheres for supporting survival of neural stem cells.

To develop a biomaterial composite for promoting proliferation and migration of neural stem cells (NSCs), as well as angiogenesis on the materials, to rescue central nervous system (CNS) injuries. A delivery system was constructed based on cross-linked hyaluronic acid (HA) hydrogels, containing embedded BDNF and VEGF-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres for controlled delivery and support for NSCs in the CNS. The surface morphologies were evaluated by SEM and AFM, mechanical property was investigated by rheological tests, and release kinetics were performed by ELISA. Bioactivity of released BDNF and VEGF was assessed by neuron and endothelial cell culture, respectively. Compatibility with NSCs was studied by immunofluorescent staining. Release kinetics showed the delivery of BDNF and VEGF from PLGA microspheres and HA hydrogel composite were sustainable and stable, releasing ~20-30% within 150 h. The bioactivities preserved well to promote survival and growth of the cells. Evaluation of structure and mechanical properties showed the hydrogel composite possessed an elastic scaffold structure. Biocompatibility assay showed NSCs adhered and proliferated well on the hydrogel. Our created HA hydrogel/PLGA microsphere systems have a good potential for controlled delivery of varied biofactors and supporting NSCs for brain repair and implantation.

Viability and differentiation of neural precursors on hyaluronic acid hydrogel scaffold

The traditional notion that injured neurons are unable to regenerate in the adult mammalian brain and spinal cord has long been a concern. This view has led to methodology designed to overcome this problem, most recently by advancements in tissue engineering. Here, neural precursor cells (NPCs) and the Nogo receptor antibody (NgR-Ab) or poly-L-lysine (PLL) were tested in concert with hyaluronic acid hydrogel scaffolds (HA). In particular, we wished to optimize viability and differentiation of NPCs within HA hydrogel scaffolds. Our results show that HA hydrogels can be modified physically or chemically to improve NPCs attachment on the scaffolding doped with NgR-Ab or PLL. Both the HA hydrogels and their modifications support the viability of NPCs. NPCs were also able to differentiate into neurons and glial cells on HA hydrogels, although this was affected by the different modifications. Immunofluorescence showed that fewer beta-III-tubulin antibody and antineurofilament antibody-positive cells were found on HA-PLL hydrogel compared with HA or HA NgR-Ab hydrogels. This indicates that the PLL-modified HA hydrogels may inhibit differentiation of NPCs, whereas modification by NgR-Ab had no such effect. Finally, the NgR-Ab-modified HA scaffold can be used as not only a NPC delivery system but also a bioactive factor transportation system for CNS repair.

Photopatterned anisotropic swelling of dual-crosslinked hyaluronic acid hydrogels

The purpose of a tissue engineered (TE) scaffold is to provide a support structure that can aid the regeneration of damaged tissue. Unlike native tissues, currently existing TE scaffolds are structurally simple, with homogeneous bulk properties that are unable to induce cells to regenerate architecturally complex healthy tissue. Thus, there is a need for methods that can create structural complexity within TE scaffolds to guide tissue regeneration. In this paper we have engineered novel dual-crosslinked hyaluronic acid hydrogel scaffolds with photopatterned anisotropic swelling. Anisotropic swelling can produce zonal distributions of crosslink density, water content and viscoelasticity on the macro- and micro-scales within the hydrogel scaffold. We have found that anisotropically swelling hydrogels can be obtained by a combination of chemical crosslinks and patterned photocrosslinks within a single dual-crosslinked hydrogel. According to our method an unswollen chemically crosslinked hydrogel substrate was spatially patterned with photocrosslinks that restricted swelling at selected sites. The resulting dual-crosslinked hydrogel swelled anisotropically because of differential crosslink densities between the photopatterned and non-photopatterned regions. Anisotropic swelling permitted the hydrogel to contort and evolve a shape different from that of the unswollen hydrogel. A biodegradable hydrogel with this unique swelling behavior yields a new, unexplored type of shape-changing TE scaffold.

116 Applicaton of a Novel Crosslinked Glycosaminoglycan Hydrogel Scaffold Improves Healing in a Rabbit Ear Ulcer Model

Introduction: Hyaluronic acid (HA) is a major glycosaminoglycan component of normal dermis and a major component of the matrix synthesized during wound healing. Previous studies have shown that uncrosslinked HA is rapidly degraded and cleared in vivo, limiting its clinical utility. We have used a novel HA hydrogel scaffold that is crosslinked for prolonged bioavailability. It has a porous interior and a smooth surface. This scaffold can also be fabricated with collagen and linked to proteins or DNA to direct cell growth and differentiation. We hypothesized that this novel HA formulation might itself improve wound healing by enhancing cell migration. Purpose: The present study explored the effects of a crosslinked HA hydrogel on wound healing. Methods: Using an established model of wound healing, four 7 mm punch wounds were made on each ear of New Zealand rabbits. Each wound was immediately treated with topical application of one of the following: HA hydrogel (n = 26), HA/collagen hydrogel (n = 27), or phosphate-buffered saline (PBS)(n = 16). Wounds were harvested on day 8 for histologic evaluation. Sections were examined for epithelial and granulation tissue ingrowth into wounds. Results: HA- and HA/collagen-treated wounds showed statistically significant increases in epithelial (p = 0.003 and p = 0.007, respectively) and granulation tissue ingrowth (p = 0.004 and p = 0.01, respectively) when compared to PBS-treated controls. Conclusions: In the rabbit ear ulcer model, the application of crosslinked HA and HA/collagen hydrogels accelerated wound healing as measured by epithelial and granulation tissue ingrowth. Funding Source: NIH grant: 5R01GM063825–03

Carbon Nanotubes as Structural Nanofibers for Hyaluronic Acid Hydrogel Scaffolds

We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions. Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone. We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels. The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones. We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content). This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains. As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.

Crosslinked hyaluronic acid hydrogels: a strategy to functionalize and pattern

The physiological activity of hyaluronic acid (HA) polymers and oligomers makes it a promising material for a variety of applications. The development of HA–hydrogel scaffolds with improved mechanical stability against degradation and biochemical functionality may enhance their application to tissue engineering. In this report, a crosslinking strategy targeting the alcohol groups via a poly(ethylene glycol) diepoxide crosslinker was investigated for the generation of degradable HA hydrogels. To provide support for cell adhesion in vitro, collagen was incorporated into the HA solution prior to the crosslinking process. The hydrogels have a continuous exterior and a porous interior, with pore diameters ranging from 6 to 9 μm. HA and HA–collagen hydrogels degrade in the presence of hyaluronidase and collagenase enzymes, indicating that the chemical modification does not prevent biodegradation. Complete degradation of the hydrogels occurred within 14 days in hyaluronidase (100 U/ml) and 3 days in collagenase (66 U/ml). Pattern transfer was employed to introduce a surface topography onto the hydrogel, which was able to orient cell growth. Furthermore, the hydrogels could be functionalized with the biomolecule neutravidin by incorporation of biotin along the HA backbone. This biotinylation approach may allow attachment of bioactive molecules that are conjugated to avidin.