Biological evaluation of micro-patterned hyaluronic acid hydrogel for bone tissue engineering

Extensive epidural fibrosis is a common complication following spinal surgery and can cause pain and limited mobility. In the present study, a novel biomimetic approach was developed to prevent postsurgical adhesion of the dura. We aimed to reconstruct epidural fat, which prevents scar-tissue adhesion, through the development of an injectable decellularized adipose matrix (DAM)-containing hyaluronic acid (HA) hydrogel loaded with adipose stromal cells (ASCs). Injectable DAM was prepared from porcine adipose tissue by four freeze—thaw cycles with subsequent pepsin digestion. Residual analyses confirmed the efficacy of detergent-free decellularization, while most sulfated glycosaminoglycans and collagen were preserved. The Transwell migration assay demonstrated the anti-infiltrative property of the DAM-containing HA hydrogel. After 14 d of 3D culture, the DAM-containing HA hydrogel showed inductive potential in the adipogenic differentiation of ASCs. For an in vivo study, the ASC-loaded DAM-containing HA hydrogel (DAM/ASC-incorporated HA hydrogel) was injected into adult laminectomized male rats, and the results were assessed by microscopic histological examination. The in vivo data indicated that HA hydrogel, DAM, and ASCs were all required for the ability of the engineered fat tissue to block the invasion of the fibrous tissue. Our results suggested that this injectable DAM/ASC-incorporated HA hydrogel has potential applications in minimally invasive surgery for soft-tissue reconstruction and epidural fibrosis prevention.

Injectable hyaluronic acid (HA) hydrogels, crosslinked with 1,4-butanediol diglycidyl ether (BDDE), are widely used in aesthetic medicine. Due to their high clinical tolerance, HA hydrogels are thought to be applicable as injectable drug delivery systems. Here, HA matrix structures of BDDE-crosslinked HA hydrogels were analysed, and the effects of the structures on the release of two model drugs were assessed. Seven crosslinked HA hydrogels were observed by optical microscopy and cryo scanning electron microscopy (cryo-SEM). We observed three specific matrix macrostructures under optical microscopy: two had a “spider web”-like structure, three had a particulate structure, and two had an intermediate structure. These differences were less evident under cryo-SEM, where all hydrogels exhibited fibrous microstructures of different homogeneity levels, with pore sizes between 0.5 and 18 μm. Three cross-linked HA hydrogels with different macrostructures were loaded with bovine serum albumin (BSA) and lidocaine to assess their capacities to release drug over 4 days. No differences in drug release were observed between gels, and BSA was released for up to 4 days, which was four times longer than lidocaine. Thus, BDDEcrosslinked HA hydrogels could be applied as an injectable drug delivery system, particularly for the delivery of high-molecular-weight molecules.

Pre-culture of mesenchymal stem cells within RGD-modified hyaluronic acid hydrogel improves their resilience to ischaemic conditions

Electrically conductive hyaluronic acid (HA) hydrogels incorporated with single-walled carbon nanotubes (CNTs) and/or polypyrrole (PPy) were developed to promote differentiation of human neural stem/progenitor cells (hNSPCs). The CNT and PPy nanocomposites, which do not easily disperse in aqueous phases, dispersed well and were efficiently incorporated into catechol-functionalized HA (HA-CA) hydrogels by the oxidative catechol chemistry used for hydrogel cross-linking. The prepared electroconductive HA hydrogels provided dynamic, electrically conductive three-dimensional (3D) extracellular matrix environments that were biocompatible with hNSPCs. The HA-CA hydrogels containing CNT and/or PPy significantly promoted neuronal differentiation of human fetal neural stem cells (hfNSCs) and human induced pluripotent stem cell-derived neural progenitor cells (hiPSC-NPCs) with improved electrophysiological functionality when compared to differentiation of these cells in a bare HA-CA hydrogel without electroconductive motifs. Calcium channel expression was upregulated, depolarization was activated, and intracellular calcium influx was increased in hNSPCs that were differentiated in 3D electroconductive HA-CA hydrogels; these data suggest a potential mechanism for stem cell neurogenesis. Overall, our bioinspired, electroconductive HA hydrogels provide a promising cell-culture platform and tissue-engineering scaffold to improve neuronal regeneration.

Event Abstract Back to Event Hyaluronic acid hydrogels cross-linked by polyethylene glycol diglycidyl ether (PEGDE) for long-lasting dermal filler applications Ho-Yong Lee1*, Seol-Ha Jeong1, Jae-Uk Baek1, Ju-Ha Song1 and Hyoun-Ee Kim1 1 Seoul national university, Materials science and engineering, Korea Statement of Purpose: Dermal fillers have been widely used for cosmetic applications such as wrinkle management and plastic surgery. Hyaluronic acid (HA) has been regarded as the best candidate for dermal fillers due to its non-immunogenicity and biodegradability[1]. HA for commercial dermal fillers is often chemically cross-linked by 1,4-butanediol diglycidyl ether (BDDE) for enhanced mechanical properties and biostability[2]. However, BDDE-crosslinked HA fillers is known to lose their mechanical integrity within 6 months in vivo by enzymatic degradation[3]. Therefore, in this study, we have incorporated polyethylene glycol diglycidyl ether (PEGDE) into HA hydrogels as a chemical cross-linker to further enhance mechanical and biological stability as compare to BDDE. Moreover, we investigate in vitro and in vivo biological behavior of PEGDE-crosslinked HA fillers. Methods: HA hydrogels were cross-linked using PEGDE (Mn = 2000 Da) or BDDE. 20 wt. % HA solution was prepared by dissolving 0.1 g HA (Mn = 2.2 MDa) in 0.5 mL 0.3 N NaOH aqueous solution. 5 µL BDDE was added to the HA solution. Likewise, the molar equivalent amount (0.15 mol crosslinker/ 1 mol HA) of PEGDE to BDDE was added to the HA solution. The reactions were performed at 25 oC for 24 h. Rheology measurement was carried out using parallel plate rheometer. Swelling test was performed with fully swollen samples in PBS at 37 ºC. In vitro degradation was performed in Hyaluronidase/PBS (100 U/ml) solution. In vitro cell test was performed by culturing L929 fibroblasts on the gel surface. Results: Rheological behavior of cross-linked HA hydrogels by BDDE and PEGDE were shown in Fig. 1a. The storage modulus of PEGDE-cross-linked HA hydrogel was higher than that of BDDE-crosslinked HA hydrogel, meaning higher elasticity in PEGDE-cross-linked HA hydrogel. Swelling behavior was inversely correlated to storage modulus (Fig. 1b). Degradation stability by hyaluronidase was evaluated by volumetric and shape change, showing PEGDE-cross-linked HA hydrogel is more resistant to degradation than BDDE-cross-linked HA hydrogel (Fig. 2). Between time intervals, the hydrogels maintained their initial shape. Cell spreading was observed for both gels (Fig. 3). On PEGDE-cross-linked HA hydrogel, fibroblasts spread well almost “spindle-like” phenotype, whereas “spherical” shape on BDDE-cross-linked HA hydrogel, implying cell-matrix interaction is higher on PEGDE-cross-linked HA hydrogel surface. Conclusions: PEGDE-cross-linked HA hydrogel was fabricated with more efficient cross-linking effect as compared to BDDE-cross-linked HA hydrogel. Higher elasticity and biostability can be obtained by using PEGDE rather than BDDE. Moreover, the hydrogel can controllable in mechanical properties and degradability by the amount of cross-linker with minimally modified. Exploiting great biocompatibility of PEG/HA hydrogel can be a good candidate for long-lasting dermal filler applications. Small and Medium Business Administration, Republic of Korea (S2174750)

Applications of functionalized hyaluronic acid (HA) hydrogels for numerous biomedical applications requires their detailed structural characterization. Since these materials are prepared by multistep chemical modifications in the solid phase and not amenable to characterization by standard analytical tools, we employed high-resolution solid-state NMR spectroscopy to gain detailed insights into the structures of the functionalized HA hydrogels. Divinyl sulfone crosslinked HA hydrogels were converted into maleimide-functionalized hydrogels, which were subjected to chemoselective thiol-maleimide reaction using L-cysteine as the protein mimetic thiol reagent. To overcome challenges associated with obtaining high-resolution NMR spectra of crosslinked hydrogels (such as line broadening and overlapping of signals of the hydrogel with those of residual reagents and solvents used during multi-step reaction processes on insoluble polymer matrices), we devised a radio frequency mediated diffusion-edited semi solid-state NMR technique. This technique enabled us to record NMR spectra of hydrogels exclusively by effectively suppressing signals associated with low molecular weight impurities. Thus, it became possible to perform in-depth characterization of these chemically modified HA hydrogels including quantification of reaction outcome for each reaction step.

In situ delivery of apoptotic bodies derived from mesenchymal stem cells via a hyaluronic acid hydrogel: A therapy for intrauterine adhesions

Hyaluronic acid (HA) hydrogels are interesting delivery systems for topical applications. Besides moisturizing the skin and improving wound healing, HA facilitates topical drug absorption and is highly compatible with labile biomacromolecules. Hence, in this study we investigated the influence of HA hydrogels with different molecular weights (5 kDa, 100 kDa, 1 MDa) on the skin absorption of the model protein bovine serum albumin (BSA) using fluorescence lifetime imaging microscopy (FLIM). To elucidate the interactions of HA with the stratum corneum and the skin absorption of HA itself, we combined FLIM and Fourier-transform infrared (FTIR) spectroscopy. Our results revealed distinct formulation and skin-dependent effects. In barrier deficient (tape-stripped) skin, BSA alone penetrated into dermal layers. When BSA and HA were applied together, however, penetration was restricted to the epidermis. In normal skin, penetration enhancement of BSA into the epidermis was observed when applying low molecular weight HA (5 kDa). Fluorescence resonance energy transfer analysis indicated close interactions between HA and BSA under these conditions. FTIR spectroscopic analysis of HA interactions with stratum corneum constituents showed an α-helix to β-sheet interconversion of keratin in the stratum corneum, increased skin hydration, and intense interactions between 100 kDa HA and the skin lipids resulting in a more disordered arrangement of the latter. In conclusion, HA hydrogels restricted the delivery of biomacromolecules to the stratum corneum and viable epidermis in barrier deficient skin, and therefore seem to be potential topical drug vehicles. In contrast, HA acted as an enhancer for delivery in normal skin, probably mediated by a combination of cotransport, increased skin hydration, and modifications of the stratum corneum properties.

Background: Hyaluronic acid (HA) hydrogels are the most widely used injectable fillers for facial rejuvenation. A new generation of HA fillers crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDE) has been developed to enhance cohesiveness, tissue integration, stability, and longevity while minimizing swelling and immunogenicity. Owing to their distinct viscoelastic properties, PEGDE-crosslinked HA fillers may require product-specific selection and adapted injection techniques. Objective: The objective of this study is to provide practical, expert-based recommendations for the safe and effective use of PEGDE-crosslinked HA hydrogels in facial aesthetic treatments. Methods: A multidisciplinary panel of nine Italian experts in aesthetic medicine, each with more than 15 years of experience using HA fillers, developed consensus recommendations based on clinical practice and available evidence. A pre-meeting questionnaire informed structured discussions during a face-to-face meeting held in Paris in January 2024. The nominal group technique was applied, with consensus defined as agreement by at least 80% of panel members. Results: Consensus was reached on product selection, injection planes, delivery devices, techniques, and typical treatment volumes for PEGDE-HA hydrogels across multiple facial regions, including the forehead, temples, midface, nasolabial folds, chin, jawline, and lips. Recommended injection techniques included microbolus, macrobolus, and retrograde linear threading, with placement ranging from superficial subcutaneous to supraperiosteal planes depending on the anatomical area and clinical indication. Typical injection volumes generally ranged from 0.1 to 0.5 mL per side. Optional ultrasound mapping was considered beneficial in selected high-risk or superficial procedures to improve anatomical safety. Conclusions: These expert consensus recommendations provide practical guidance for clinicians using PEGDE-crosslinked HA hydrogels in facial rejuvenation. Tailoring product characteristics to injection depth, technique, and regional anatomy may help optimize clinical outcomes and procedural safety. Future research priorities include prospective comparative studies with other crosslinking technologies, standardized reporting of adverse events, long-term outcome registries, and further evaluation of ultrasound-guided injection strategies.

Personalized treatment with a combination of aesthetic protocols targets the different root causes, contributing to the patient’s aesthetic concerns and optimizes outcomes. This report presents the outcomes of a new protocol combining PEGylated hyaluronic acid (HA) hydrogel, non-ablative laser, and non-crosslinked HA skin booster to rejuvenate the perioral area within a single treatment session. This was a retrospective analysis of medical data from subjects who had undergone treatment with the perioral rejuvenation protocol at Kalea Clinic in the Netherlands. All subjects had been treated with the 3-step protocol involving: (i) injection with PEGylated HA hydrogel 24 mg/ml to contour and shape the lips; (ii) full-face treatment with a non-ablative, fractional diode laser with a wavelength of 1470 nm to smooth and tighten the skin; and (iii) full-face mesotherapy treatment with injection of non-crosslinked HA (18 mg/mL) with 0.01% calcium hydroxyapatite, glycine, and L-proline to improve skin quality. Follow-up visits took place at 6 (Visit 1) and 12 weeks (Visit 2), at which point physicians and patients assessed lip fullness and skin wrinkling on separate validated rating scales. Additional subjective assessment of treatment results was performed by both physicians and patients using the 5-point Global Aesthetic Improvement Scale (GAIS). Physician and patient satisfaction with treatment results was also assessed. Data were analyzed retrospectively for 14 female subjects with a mean age of 39.1 years. At baseline, lip fullness was rated as moderate by 71% of physicians and 64% of patients. At visit 2, 71% of lips were rated as thick and 14% as full by both physicians and patients. The mean skin wrinkle score improved from 1.30 (visible wrinkles with clear indentation) at baseline to 0.79 (fine wrinkle, slight indentation) at Visit 2. Mean GAIS scores for both physicians and patients indicated appearance was ‘improved’ at Visit 1 (mean scores of 3.0 and 2.7, respectively) and ‘much improved’ at Visit 2 (mean scores of 2.4 and 2.3, respectively). All treatments in the protocol were well tolerated. Both physicians and patients were satisfied with the combination protocol, and all patients reported they would be ‘likely’ or ‘very likely’ to recommend it. The combination of three different treatment modalities (PEGylated HA hydrogel, non-ablative laser, and HA mesotherapy) in a single treatment session demonstrated effectiveness in rejuvenating lips and perioral area. The complementary treatments were tailored to the individual for a natural-looking effect.

A novel, biocompatible, and nontoxic dermal filler using hyaluronic acid (HA) hydrogels was successfully developed for tissue augmentation applications. Instead of using highly reactive cross-linkers such as divinyl sulfone (DVS) for Hylaform, 1,4-butanediol diglycidyl ether (BDDE) for Restylane, and 1,2,7,8-diepoxyoctane (DEO) for Puragen, HA hydrogels were prepared by direct amide bond formation between the carboxyl groups of HA and hexamethylenediamine (HMDA) with an optimized carboxyl group modification for effective tissue augmentation. The HA-HMDA hydrogels could be prepared within 5 min by the addition of HMDA to HA solution activated with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and 1-hydroxybenzotriazole monohydrate (HOBt). Five kinds of samples, a normal control, a negative control, a positive control of Restylane, adipic acid dihydrazide grafted HA (HA-ADH) hydrogels, and HA-HMDA hydrogels, were subcutaneously injected to wrinkled model mice. According to the image analysis on dorsal skin augmentation, the HA-HMDA hydrogels exhibited the best tissue augmentation effect being stable longer than 3 months. Furthermore, histological analyses after hematoxylin-eosin (H&E) and Masson's trichrome staining revealed the excellent biocompatibility and safety of HA-HMDA hydrogels. The dermal thickness and the dermal collagen density in wrinkled mice after treatment with HA-HMDA hydrogels for 12 weeks were comparable to those of normal mice. Compared with HA-DVS hydrogels and Restylane, the excellent tissue augmentation by HA-HMDA hydrogels might be ascribed to the biocompatible residues of amine groups in the cross-linker of HMDA. The HA-HMDA hydrogels will be investigated further as a novel dermal filler for clinical applications.

American ginseng vesicles loaded hyaluronic acid hydrogel for ulcerative colitis.

This work was aimed to explore the potential effect of hyaluronic acid (HA) initial concentration (7.0 - 14.0 % w/v) on cross-linking efficiency of HA hydrogels cross-linked with 1,4-butanediol diglycidyl ether (BDDE). The results revealed that the hydrogel prepared at 10.0 % HA concentration exhibited a slower degradation rate, a lower swelling ability and more regular porosity than those prepared at either lower or higher HA concentration. After four days incubating with hyaluronidase, the content of NAG (N-acetyl glucosamine) remaining in the 10.0 HA hydrogel was 25.1±1.9 % with respect to the total NAG content found in the original mass. In contrast, the hydrogels prepared at 7.0 % and 14.0 % HA concentration showed a less remaining content of NAG equaled to approximately 15.9±5.4 % and 19.5±2.6 % respectively. On the other hand, the swelling ability of tested hydrogels was steadily decreased with the increase of HA initial concentration until the 10.0 % HA hydrogel and then showed an opposite trend. Based on this finding, the 10.0 % HA hydrogel exhibited the lowest swelling ratio which was observed at 129±3.2 g/g in distilled water and at 116±2.4 g/g in phosphate buffer saline (PBS). The SEM images showed various morphologies within the entire range of tested hydrogels. However, the hydrogel prepared at 10.0 % HA concentration was more homogenous and appeared with narrower pore-size distribution ranged in diameter from less than 50 μm to approximately 300 μm. Finally, the effect of HA initial concentration was investigated by FTIR which confirmed that the 10.0 % HA hydrogel was subject to a greater loss of (- OH) at 3343 cm-1 than other hydrogels except the 11.0 % HA hydrogel. This phenomenon was probably attributed to the formation of pendants that allowed the 11.0 % HA hydrogel to appear with a lower peak intensity than the 10.0 % HA hydrogel in the FTIR spectra. In conclusion, the HA initial concentration plays a crucial role in determining the cross-linking efficiency of HA hydrogels cross-linked with BDDE.

This study develops a novel drug delivery system using a hyaluronic acid (HA) hydrogel for controlled release of epidermal growth factor (EGF) to enhance skin wound healing. Conventional hydrogel-based methods suffer from a burst release and limited drug delivery times. To address this, we employ bioconjugation to introduce an acrylate group to EGF, enabling chemical bonding to the HA hydrogel matrix through thiol-ene cross-linking. This approach results in sustained-release delivery of EGF based on the degradation rate of the HA matrix, overcoming diffusion-based limitations. We confirm the introduction of the acrylate group using matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. We evaluated the hydrogel morphology and rheological properties following binding of acrylate-conjugated EGF to the HA matrix. Assessment of the EGF release profile demonstrates delayed release compared to unconjugated EGF. We evaluate the impact on cells through cell proliferation and scratch assays, indicating the system's efficacy. In a rat wound healing model, the sustained release of EGF from the hydrogel system promotes appropriate tissue healing and restores it to a normal state. These findings suggest that this practical drug delivery system, involving the modification of growth factors or drugs to chemically bind healing factors to hydrogels, can achieve long-lasting effects.

Structurally decoupled hyaluronic acid hydrogels for studying matrix metalloproteinase-mediated invasion of metastatic breast cancer cells