Sintered porous Ti6Al4V scaffolds incorporated with recombinant human bone morphogenetic protein-2 microspheres and thermosensitive hydrogels can enhance bone regeneration

Recent advances of chitosan-based composite hydrogel materials in application of bone tissue engineering

Bone defects, stemming from trauma, tumors, infections, and congenital conditions, pose significant challenges in orthopedics. Although the body possesses innate mechanisms for bone self-repairing, factors such as aging, disease, and injury can impair these processes, jeopardizing skeletal integrity. Addressing substantial bone defects remains a global orthopedic concern, with variables like gender, lifestyle and preexisting conditions influencing fracture risk and complication rates. Traditional repair methods, mainly bone transplantation including autografts, allografts and xenografts, have shown effectiveness but also present limitations. Autologous bone grafts, highly valued for their osteogenic properties, require additional surgeries with extended hospitalization, and carry risks associated with the donor site. The development of advanced biomaterials offers promising new avenues for bone repair. An ideal material should exhibit a combination of biocompatibility, biodegradability, bone conduction, porosity, strength, and the ability to stimulate bone formation. Chitosan (CS), derived from chitin, stands out due to its biocompatibility, biodegradability, low immunogenicity, non-toxicity, and a wide range of biological activities, including antioxidant, anti-tumor, anti-inflammatory, antimicrobial, and immunomodulatory properties. Notably, CS has shown the properties to promote bone regeneration, increase bone density, and accelerate fracture healing. This review provides a comprehensive examination of CS-based hydrogels for bone repair aiming to inspire researchers by presenting new ideas for innovative CS-based solutions, thereby advancing their potential applications in the field of bone repair.

Polycaprolactone Hybrid Scaffold Loaded With N,O-Carboxymethyl Chitosan/Aldehyde Hyaluronic Acid/Hydroxyapatite Hydrogel for Bone Regeneration

Hydrogels have emerged as potential materials for bone grafting, thanks to their biocompatibility, biodegradation, and flexibility in filling irregular bone defects. In this study, we fabricated a novel NAH hydrogel system, composed of N,O-carboxymethyl chitosan (NOCC), aldehyde hyaluronic acid (AHA), and hydroxyapatite (HAp). To improve the mechanical strength of the fabricated hydrogel, a porous polycaprolactone (PCL) matrix was synthesized and used as a three-dimensional (3D) support template for NAH hydrogel loading, forming a novel PCL/NAH hybrid scaffold. A mixture of monosodium glutamate (M) and sucrose (S) at varied weight ratios (5M:5S, 7M:3S, and 9M:1S) was used for the fabrication of 3D PCL matrices. The morphology, interconnectivity, and water resistance of the porous PCL scaffolds were investigated for optimal hydrogel loading efficiency. The results demonstrated that PCL scaffolds with porogen ratios of 7M:3S and 9M:1S possessed better interconnectivity than 5M:5S ratio. The compressive strength of the PCL/NAH hybrid scaffolds with 9M:1S (561.6 ± 6.1 kPa) and 7M:3S (623.8 ± 6.8 kPa) ratios are similar to cancellous bone and all hybrid scaffolds were biocompatible. Rabbit models with tibial defects were implanted with the PCL/NAH scaffolds to assess the wound healing capability. The results suggest that the PCL/NAH hybrid scaffolds, specifically those with porogen ratio of 7M:3S, exhibit promising bone healing effects.

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.

Applications of Stimuli-Responsive Hydrogels in Bone and Cartilage Regeneration

Bone and cartilage regeneration is an area of tremendous interest and need in health care. Tissue engineering is a potential strategy for repairing and regenerating bone and cartilage defects. Hydrogels are among the most attractive biomaterials in bone and cartilage tissue engineering, mainly due to their moderate biocompatibility, hydrophilicity, and 3D network structure. Stimuli-responsive hydrogels have been a hot topic in recent decades. They can respond to external or internal stimulation and are used in the controlled delivery of drugs and tissue engineering. This review summarizes current progress in the use of stimuli-responsive hydrogels in bone and cartilage regeneration. The challenges, disadvantages, and future applications of stimuli-responsive hydrogels are briefly described.

Smart Hydrogels for Advanced Drug Delivery Systems

Since the last few decades, the development of smart hydrogels, which can respond to stimuli and adapt their responses based on external cues from their environments, has become a thriving research frontier in the biomedical engineering field. Nowadays, drug delivery systems have received great attention and smart hydrogels can be potentially used in these systems due to their high stability, physicochemical properties, and biocompatibility. Smart hydrogels can change their hydrophilicity, swelling ability, physical properties, and molecules permeability, influenced by external stimuli such as pH, temperature, electrical and magnetic fields, light, and the biomolecules' concentration, thus resulting in the controlled release of the loaded drugs. Herein, this review encompasses the latest investigations in the field of stimuli-responsive drug-loaded hydrogels and our contribution to this matter.

Enhanced regeneration of bone defects using sintered porous Ti6Al4V scaffolds incorporated with mesenchymal stem cells and platelet-rich plasma

A new highly controlled powder sintering technique was used for the fabrication of a porous Ti6Al4V scaffold. The platelet-rich plasma (PRP) was prepared using whole blood. The PRP was used as a cell carrier to inject bone marrow mesenchymal stem cells (MSC) into the pores of the Ti6Al4V scaffold in the presence of calcium chloride and thrombin, and then the composite construct of porous Ti6Al4V loaded with PRP gel and MSC was obtained. The bare Ti6Al4V scaffold and the Ti6Al4V scaffold loaded with MSC were used as controls. The characteristics and mechanical properties of the scaffold, and the biological properties of the constructs were evaluated by a series of in vitro and in vivo experiments. The results show that the sintered porous Ti6Al4V has good biocompatibility, and high porosity and large pore size, which can provide sufficient space and sufficient mechanical support for the growth of cells and bones without an obvious stress shielding effect. However, Ti6Al4V/MSC/PRP showed a significantly higher cell proliferation rate, faster bone growth speed, more bone ingrowth, and higher interfacial strength. Therefore, the porous Ti6Al4V scaffolds incorporated with MSC and PRP may be more effective at enhancing bone regeneration, and is expected to be used for bone defect repair.

Fabrication techniques of biomimetic scaffolds in three-dimensional cell culture: A review

In the last four decades, several researchers worldwide have routinely and meticulously exercised cell culture experiments in two-dimensional (2D) platforms. Using traditionally existing 2D models, the therapeutic efficacy of drugs has been inappropriately validated due to the failure in generating the precise therapeutic response. Fortunately, a 3D model addresses the foregoing limitations by recapitulating the in vivo environment. In this context, one has to contemplate the design of an appropriate scaffold for favoring the organization of cell microenvironment. Instituting pertinent model on the platter will pave way for a precise mimicking of in vivo conditions. It is because animal cells in scaffolds oblige spontaneous formation of 3D colonies that molecularly, phenotypically, and histologically resemble the native environment. The 3D culture provides insight into the biochemical aspects of cell-cell communication, plasticity, cell division, cytoskeletal reorganization, signaling mechanisms, differentiation, and cell death. Focusing on these criteria, this paper discusses in detail, the diversification of polymeric scaffolds based on their available resources. The paper also reviews the well-founded and latest techniques of scaffold fabrication, and their applications pertaining to tissue engineering, drug screening, and tumor model development.