Recent Progress in Hyaluronic-Acid-Based Hydrogels for Bone Tissue Engineering

Spatiotemporal controlled released hydrogels for multi-system regulated bone regeneration

Bone defect is one of the urgent problems to be solved in clinics, and it is very important to construct efficient scaffold materials to facilitate bone tissue regeneration. Hydrogels, characterized by their unique three-dimensional network structure, serve as excellent biological scaffold materials. Their internal pores are capable of loading osteogenic drugs to expedite bone formation. The rate and quality of new bone formation are intimately linked with immune regulation and vascular remodeling. The strategic sequential release of drugs to balance inflammation and regulate vascular remodeling is crucial for initiating the osteogenic process. Through the design of hydrogel microstructures, it is possible to achieve sequential drug release and the drug action time can be prolonged, thereby catering to the multi-systemic collaborative regulation needs of osteosynthesis. The drug release rate within the hydrogel is governed by swelling control systems, physical control systems, chemical control systems, and environmental control systems. Utilizing these control systems to design hydrogel materials capable of multi-drug delivery optimizes the construction of the bone microenvironment. Consequently, this facilitates the spatiotemporal controlled released of drugs, promoting bone tissue regeneration. This paper reviews the principles of the controlled release system of various sustained-release hydrogels and the advancements in research on hydrogel multi-drug delivery systems for bone tissue regeneration.

The combination of modified acupuncture needle and melittin hydrogel as a novel therapeutic approach for rheumatoid arthritis treatment

Rheumatoid arthritis (RA) involves chronic joint inflammation. Combining acupuncture and medication for RA treatment faces challenges like spatiotemporal variability, limited drug loading in acupuncture needles, and premature or untargeted drug release. Here, we designed a new type of tubular acupuncture needles, with an etched hollow honeycomb-like structure to enable the high loading of therapeutics, integrating the traditional acupuncture and drug repository into an all-in-one therapeutic platform. In these proof-of-concept experiments, we fabricated injectable hollow honeycomb electroacupuncture needles (HC-EA) loaded with melittin hydrogel (MLT-Gel), enabling the combination treatment of acupuncture stimulation and melittin therapy in a spatiotemporally synchronous manner. Since the RA microenvironment is mildly acidic, the acid-responsive chitosan (CS)/sodium beta-glycerophosphate (β-GP)/ hyaluronic acid (HA) composited hydrogel (CS/GP/HA) was utilized to perform acupuncture stimulation and achieve the targeted release of injected therapeutics into the specific lesion site. Testing our therapeutic platform involved a mouse model of RA and bioinformatics analysis. MLT-Gel@HC-EA treatment restored Th17/Treg-mediated immunity balance, reduced inflammatory factor release (TNF-α, IL-6, IL-1β), and alleviated inflammation at the lesion site. This novel combination of modified acupuncture needle and medication, specifically melittin hydrogel, holds promise as a therapeutic strategy for RA treatment.

Development and evaluation of an injectable ChitHCl-MgSO4-DDA hydrogel for bone regeneration: In vitro and in vivo studies on cell migration and osteogenesis enhancement

Nonunion and delayed union of the bone are situations in orthopedic surgery that can occur even if the bone alignment is correct and there is sufficient mechanical stability. Surgeons usually apply artificial bone grafts in bone fracture gaps or in bone defect sites for osteogenesis to improve bone healing; however, these bone graft materials have no osteoinductive or osteogenic properties, and fit the morphology of the fracture gap with difficulty. In this study, we developed an injectable chitosan-based hydrogel with MgSO4 and dextran oxidative, with the purpose to improve bone healing through introducing an engineered chitosan-based hydrogel. The developed hydrogel can gelate and fit with any morphology or shape, has good biocompatibility, can enhance the cell-migration capacity, and can improve extracellular calcium deposition. Moreover, the amount of new bone formed by injecting the hydrogel in the bone tunnel was assessed by an in vivo test. We believe this injectable chitosan-based hydrogel has great potential for application in the orthopedic field to improve fracture gap healing.

Facile Preparation of Multifunctional Hydrogels with Sustained Resveratrol Release Ability for Bone Tissue Regeneration

Injectable hydrogels show great promise for bone tissue engineering applications due to their high biocompatibility and drug delivery capabilities. The bone defects in osteoporosis are usually characterized by an oxidative and inflammatory microenvironment that impairs the regeneration capability of bone tissues. To attenuate the reactive oxygen species (ROS) and promote bone regeneration, an anti-oxidative hydrogel with osteogenic capacity was developed in this study. The poorly water soluble, natural antioxidant, resveratrol, was encapsulated in thiolated Pluronic F-127 micelles with over 50-times-enhanced solubility. The injectable hydrogel was facilely formed because of the new thioester bond between the free thiol group in modified F-127 and the arylate group in hyaluronic acid (HA)-acrylate. The resveratrol-loaded hydrogel showed good viscoelastic properties and in vitro stability and was cyto-compatible with bone-marrow-derived mesenchymal stem cells (BMSCs). The hydrogel allowed for a sustained release of resveratrol for at least two weeks and effectively enhanced the osteogenic differentiation of BMSCs by the up-regulation of osteogenic markers, including ALP, OCN, RUNX-2, and COL1. Moreover, the hydrogel exhibited anti-oxidative and anti-inflammatory abilities through the scavenging of intracellular ROS in RAW264.7 cells and inhibiting the gene expression and secretion of pro-inflammatory cytokines TNF-α and IL-1β under LPS exposure. In summary, the results suggest that our multifunctional hydrogel loaded with resveratrol bearing osteogenic, anti-oxidative, and anti-inflammatory actions is easily prepared and represents a promising resveratrol delivery platform for the repair of osteoporotic bone defects.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Janus hydrogels: merging boundaries in tissue engineering for enhanced biomaterials and regenerative therapies

In recent years, the design and synthesis of Janus hydrogels have witnessed a thriving development, overcoming the limitations of single-performance materials and expanding their potential applications in tissue engineering and regenerative medicine. Janus hydrogels, with their exceptional mechanical properties and excellent biocompatibility, have emerged as promising candidates for various biomedical applications, including tissue engineering and regenerative therapies. In this review, we present the latest progress in the synthesis of Janus hydrogels using commonly employed preparation methods. We elucidate the surface and interface interactions of these hydrogels and discuss the enhanced properties bestowed by the unique "Janus" structure in biomaterials. Additionally, we explore the applications of Janus hydrogels in facilitating regenerative therapies, such as drug delivery, wound healing, tissue engineering, and biosensing. Furthermore, we analyze the challenges and future trends associated with the utilization of Janus hydrogels in biomedical applications.

Nanotechnological Research for Regenerative Medicine: The Role of Hyaluronic Acid

Hyaluronic acid (HA) is a linear, anionic, non-sulfated glycosaminoglycan occurring in almost all body tissues and fluids of vertebrates including humans. It is a main component of the extracellular matrix and, thanks to its high water-holding capacity, plays a major role in tissue hydration and osmotic pressure maintenance, but it is also involved in cell proliferation, differentiation and migration, inflammation, immunomodulation, and angiogenesis. Based on multiple physiological effects on tissue repair and reconstruction processes, HA has found extensive application in regenerative medicine. In recent years, nanotechnological research has been applied to HA in order to improve its regenerative potential, developing nanomedical formulations containing HA as the main component of multifunctional hydrogels systems, or as core component or coating/functionalizing element of nanoconstructs. This review offers an overview of the various uses of HA in regenerative medicine aimed at designing innovative nanostructured devices to be applied in various fields such as orthopedics, dermatology, and neurology.

An Overview on the Big Players in Bone Tissue Engineering: Biomaterials, Scaffolds and Cells

Presently, millions worldwide suffer from degenerative and inflammatory bone and joint issues, comprising roughly half of chronic ailments in those over 50, leading to prolonged discomfort and physical limitations. These conditions become more prevalent with age and lifestyle factors, escalating due to the growing elderly populace. Addressing these challenges often entails surgical interventions utilizing implants or bone grafts, though these treatments may entail complications such as pain and tissue death at donor sites for grafts, along with immune rejection. To surmount these challenges, tissue engineering has emerged as a promising avenue for bone injury repair and reconstruction. It involves the use of different biomaterials and the development of three-dimensional porous matrices and scaffolds, alongside osteoprogenitor cells and growth factors to stimulate natural tissue regeneration. This review compiles methodologies that can be used to develop biomaterials that are important in bone tissue replacement and regeneration. Biomaterials for orthopedic implants, several scaffold types and production methods, as well as techniques to assess biomaterials' suitability for human use-both in laboratory settings and within living organisms-are discussed. Even though researchers have had some success, there is still room for improvements in their processing techniques, especially the ones that make scaffolds mechanically stronger without weakening their biological characteristics. Bone tissue engineering is therefore a promising area due to the rise in bone-related injuries.

Hydrogel Microparticles for Bone Regeneration

Hydrogel microparticles (HMPs) stand out as promising entities in the realm of bone tissue regeneration, primarily due to their versatile capabilities in delivering cells and bioactive molecules/drugs. Their significance is underscored by distinct attributes such as injectability, biodegradability, high porosity, and mechanical tunability. These characteristics play a pivotal role in fostering vasculature formation, facilitating mineral deposition, and contributing to the overall regeneration of bone tissue. Fabricated through diverse techniques (batch emulsion, microfluidics, lithography, and electrohydrodynamic spraying), HMPs exhibit multifunctionality, serving as vehicles for drug and cell delivery, providing structural scaffolding, and functioning as bioinks for advanced 3D-printing applications. Distinguishing themselves from other scaffolds like bulk hydrogels, cryogels, foams, meshes, and fibers, HMPs provide a higher surface-area-to-volume ratio, promoting improved interactions with the surrounding tissues and facilitating the efficient delivery of cells and bioactive molecules. Notably, their minimally invasive injectability and modular properties, offering various designs and configurations, contribute to their attractiveness for biomedical applications. This comprehensive review aims to delve into the progressive advancements in HMPs, specifically for bone regeneration. The exploration encompasses synthesis and functionalization techniques, providing an understanding of their diverse applications, as documented in the existing literature. The overarching goal is to shed light on the advantages and potential of HMPs within the field of engineering bone tissue.

Dancing with Nucleobases: Unveiling the Self-Assembly Properties of DNA and RNA Base-Containing Molecules for Gel Formation

Nucleobase-containing molecules are compounds essential in biology due to the fundamental role of nucleic acids and, in particular, G-quadruplex DNA and RNA in life. Moreover, some molecules different from nucleic acids isolated from different vegetal sources or microorganisms show nucleobase moieties in their structure. Nucleoamino acids and peptidyl nucleosides belong to this molecular class. Closely related to the above, nucleopeptides, also known as nucleobase-bearing peptides, are chimeric derivatives of synthetic origin and more rarely isolated from plants. Herein, the self-assembly properties of a vast number of structures, belonging to the nucleic acid and nucleoamino acid/nucleopeptide family, are explored in light of the recent scientific literature. Moreover, several technologically relevant properties, such as the hydrogelation ability of some of the nucleobase-containing derivatives, are reviewed in order to make way for future experimental investigations of newly devised nucleobase-driven hydrogels. Nucleobase-containing molecules, such as mononucleosides, DNA, RNA, quadruplex (G4)-forming oligonucleotides, and nucleopeptides are paramount in gel and hydrogel formation owing to their distinctive molecular attributes and ability to self-assemble in biomolecular nanosystems with the most diverse applications in different fields of biomedicine and nanotechnology. In fact, these molecules and their gels present numerous advantages, underscoring their significance and applicability in both material science and biomedicine. Their versatility, capability for molecular recognition, responsiveness to stimuli, biocompatibility, and biodegradability collectively contribute to their prominence in modern nanotechnology and biomedicine. In this review, we emphasize the critical role of nucleobase-containing molecules of different nature in pioneering novel materials with multifaceted applications, highlighting their potential in therapy, diagnostics, and new nanomaterials fabrication as required for addressing numerous current biomedical and nanotechnological challenges.

Starch-Based Hydrogels as a Drug Delivery System in Biomedical Applications

Starch-based hydrogels have gained significant attention in biomedical applications as a type of drug delivery system due to their biocompatibility, biodegradability, and ability to absorb and release drugs. Starch-based hydrogels can serve as effective carriers for pharmaceutical compounds such as drugs and proteins to develop drug-loaded hydrogel systems, providing controlled release over an extended period. The porous structure of a hydrogel allows for the diffusion of drugs, ensuring sustained and localized delivery to the target site. Moreover, starch-based hydrogels have been used as a powerful option in various biomedical fields, including cancer and infectious disease treatment. In addition, starch-based hydrogels have shown promise in tissue engineering applications since hydrogels can be used as scaffolds or matrices to support cell growth and tissue regeneration. Depending on techniques such as chemical crosslinking or physical gelation, it can create a three-dimensional network structure that tunes its mechanical properties and mimics the extracellular matrix. Starch-based hydrogels can also provide a supportive environment for cell attachment, proliferation, and differentiation to promote specific cellular responses and tissue regeneration processes with the loading of growth factors, cytokines, or other bioactive molecules. In this review, starch-based hydrogels as a versatile platform for various biomedical applications are discussed.

Nanomaterial-based drug delivery of immunomodulatory factors for bone and cartilage tissue engineering

As life expectancy continues to increase, so do disorders related to the musculoskeletal system. Orthopedics-related impairments remain a challenge, with nearly 325 thousand and 120 thousand deaths recorded in 2019. Musculoskeletal system, including bone and cartilage tissue, is a living system in which cells constantly interact with the immune system, which plays a key role in the tissue repair process. An alternative to bridge the gap between these two systems is exploiting nanomaterials, as they have proven to serve as delivery agents of an array of molecules, including immunomodulatory agents (anti-inflammatory drugs, cytokines), as well as having the ability to mimic tissue by their nanoscopic structure and promote tissue repair per se. Therefore, this review outlooks nanomaterials and immunomodulatory factors widely employed in the area of bone and cartilage tissue engineering. Emerging developments in nanomaterials for delivery of immunomodulatory agents for bone and cartilage tissue engineering applications have also been discussed. It can be concluded that latest progress in nanotechnology have enabled to design intricate systems with the ability to deliver biologically active agents, promoting tissue repair and regeneration; thus, nanomaterials studied herein have shown great potential to serve as immunomodulatory agents in the area of tissue engineering.

Flexible Fabrication and Hybridization of Bioactive Hydrogels with Robust Osteogenic Potency

Osteogenic scaffolds reproducing the natural bone composition, structures, and properties have represented the possible frontier of artificially orthopedic implants with the great potential to revolutionize surgical strategies against the bone-related diseases. However, it is difficult to achieve an all-in-one formula with the simultaneous requirement of favorable biocompatibility, flexible adhesion, high mechanical strength, and osteogenic effects. Here in this work, an osteogenic hydrogel scaffold fabricated by inorganic-in-organic integration between amine-modified bioactive glass (ABG) nanoparticles and poly(ethylene glycol) succinimidyl glutarate-polyethyleneimine (TSG-PEI) network was introduced as an all-in-one tool to flexibly adhere onto the defective tissue and subsequently accelerate the bone formation. Since the N-hydroxysuccinimide (NHS)-ester of tetra-PEG-SG polymer could quickly react with the NH2-abundant polyethyleneimine (PEI) polymer and ABG moieties, the TSG-PEI@ABG hydrogel was rapidly formed with tailorable structures and properties. Relying on the dense integration between the TSG-PEI network and ABG moieties on a nano-scale level, this hydrogel expressed powerful adhesion to tissue as well as durable stability for the engineered scaffolds. Therefore, its self-endowed biocompatibility, high adhesive strength, compressive modulus, and osteogenic potency enabled the prominent capacities on modulation of bone marrow mesenchymal stem cell (BMSCs) proliferation and differentiation, which may propose a potential strategy on the simultaneous scaffold fixation and bone regeneration promotion for the tissue engineering fields.