Granular Disulfide-Crosslinked Hyaluronic Hydrogels: A Systematic Study of Reaction Conditions on Thiol Substitution and Injectability Parameters

A quality by design approach to optimise disulfide-linked hyaluronic acid hydrogels

In this study, the disulfide-linked hyaluronic acid (HA) hydrogels were optimised for potential application as a scaffold in tissue engineering through the Quality by Design (QbD) approach. For this purpose, HA was first modified by incorporating the cysteine moiety into the HA backbone, which promoted the formation of disulfide cross-linked HA hydrogel at physiological pH. Utilising a Design of Experiments (DoE) methodology, the critical factors to achieve stable biomaterials, i.e. the degree of HA substitution, HA molecular weight, and coupling agent ratio, were explored. To establish a design space, the DoE was performed with 65 kDa, 138 kDa and 200 kDa HA and variable concentrations of coupling agent to optimise conditions to obtain HA hydrogel with improved rheological properties. Thus, HA hydrogel with a 12 % degree of modification, storage modulus of ≈2321 Pa and loss modulus of ≈15 Pa, was achieved with the optimum ratio of coupling agent. Furthermore, biocompatibility assessments in C28/I2 chondrocyte cells demonstrated the non-toxic nature of the hydrogel, underscoring its potential for tissue regeneration. Our findings highlight the efficacy of the QbD approach in designing HA hydrogels with tailored properties for biomedical applications.

An injectable sequential dual-crosslinking catechol-functionalized hyaluronic acid hydrogel for enhanced regeneration of full-thickness burn injury

Severe burn injuries with massive dermal loss are often underestimated despite their significant impact on morbidity and mortality. Resembling the natural extracellular matrix (ECM), hyaluronic acid (HA)-based dressings have been extensively explored as suitable candidates for burn wound treatment. However, native HA hydrogel's limitations, such as low mechanical strength, rapid degradation, and uncontrollable drug delivery, hinder its efficacy, especially for full-thickness burns requiring injectable hydrogels with robust antibacterial and angiogenic capabilities. Herein, we present a novel multifunctional sequential dual-curing hydrogel system, combining hyperbranched poly(DMA-DMAPMA-PEGDA) (DDP) polymer with thiolated hyaluronic acid (HA-SH). The DDP copolymer, featuring multi-vinyls and catechol functionalities, facilitates two curing reactions taking place sequentially with HA-SH under physiological conditions, balancing convenient injection with the mechanical strength essential for effective wound management. Furthermore, the resulting DDP/HA hydrogels demonstrate enhanced therapeutic attributes, including intrinsic angiogenic and antimicrobial effects, setting them as promising dressing options for deep burn wound therapy.

pH-sensitive docetaxel-loaded chitosan/thiolated hyaluronic acid polymeric nanoparticles for colorectal cancer

Aim: This study aimed to develop and evaluate pH-sensitive docetaxel-loaded thiolated hyaluronic acid (HA-SH) nanoparticles (NPs) for targeted treatment of colon cancer. Materials & methods: HA-SH, synthesized via oxidation and subsequent covalent linkage to cysteamine, served as the precursor for developing HA-SH NPs through polyelectrolyte complexation involving chitosan and thiol-bearing HA. Results & conclusion: HA-SH NPs displayed favorable characteristics, with small particle sizes (184-270 nm), positive zeta potential (15.4-18.6 mV) and high entrapment efficiency (91.66-95.02%). In vitro, NPs demonstrated potent mucoadhesion and enhanced cytotoxicity compared with free docetaxel. In vivo assessments confirmed safety and biocompatibility, suggesting HA-SH NPs as promising pH-sensitive drug carriers with enhanced antitumor activity for colorectal cancer treatments.

Combining adhesive and nonadhesive injectable hydrogels for intervertebral disc repair in an ovine discectomy model

Background

Intervertebral disc (IVD) disorders (e.g., herniation) directly contribute to back pain, which is a leading cause of global disability. Next-generation treatments for IVD herniation need advanced preclinical testing to evaluate their ability to repair large defects, prevent reherniation, and limit progressive degeneration. This study tested whether experimental, injectable, and nonbioactive biomaterials could slow IVD degeneration in an ovine discectomy model.

Methods

Ten skeletally mature sheep (4-5.5 years) experienced partial discectomy injury with cruciate-style annulus fibrosus (AF) defects and 0.1 g nucleus pulposus (NP) removal in the L1-L2, L2-L3, and L3-L4 lumbar IVDs. L4-L5 IVDs were Intact controls. IVD injury levels received: (1) no treatment (Injury), (2) poly (ethylene glycol) diacrylate (PEGDA), (3) genipin-crosslinked fibrin (FibGen), (4) carboxymethylcellulose-methylcellulose (C-MC), or (5) C-MC and FibGen (FibGen + C-MC). Animals healed for 12 weeks, then IVDs were assessed using computed tomography (CT), magnetic resonance (MR) imaging, and histopathology.

Results

All repaired IVDs retained ~90% of their preoperative disc height and showed minor degenerative changes by Pfirrmann grading. All repairs had similar disc height loss and Pfirrmann grade as Injury IVDs. Adhesive AF sealants (i.e., PEGDA and FibGen) did not herniate, although repair caused local endplate (EP) changes and inflammation. NP repair biomaterials (i.e., C-MC) and combination repair (i.e., FibGen + C-MC) exhibited lower levels of degeneration, less EP damage, and less severe inflammation; however, C-MC showed signs of herniation via biomaterial expulsion.

Conclusions

All repair IVDs were noninferior to Injury IVDs by IVD height loss and Pfirrmann grade. C-MC and FibGen + C-MC IVDs had the best outcomes, and may be appropriate for enhancement with bioactive factors (e.g., cells, growth factors, and miRNAs). Such bioactive factors appear to be necessary to prevent injury-induced IVD degeneration. Application of AF sealants alone (i.e., PEGDA and FibGen) resulted in EP damage and inflammation, particularly for PEGDA IVDs, suggesting further material refinements are needed.