Natural Polymeric Scaffolds in Bone Regeneration

Evaluation of Opuntia-carrageenan superporous hydrogel (OPM-CRG SPH) as an effective biomaterial for drug release and tissue scaffold

The process of wound healing involves complex interplay of systems biology, dependent on coordination of various cell types, both intra and extracellular mechanisms, proteins, and signaling pathways. To enhance these interactions, drugs must be administered precisely and continuously, effectively regulating the intricate mechanisms involved in the body's response to injury. Controlled drug delivery systems (DDS) play a pivotal role in achieving this objective. A proficient DDS shields the wound from mechanical, oxidative, and enzymatic stress, against bacterial contamination ensuring an adequate oxygen supply while optimizing the localized and sustained delivery of drugs to target tissue. A pH-sensitive SPH was designed by blending two natural polysaccharides, Opuntia mucilage and carrageenan, using microwave irradiation and optimized according to swelling index at pH 1.2, 7.0, and 8.0 and % porosity. Optimized grade was analyzed for surface hydrophilicity-hydrophobicity using OCA. Analytical characterizations were performed using FTIR, TGA, XRD, DSC, reflecting semicrystalline behavior. Mechanical property confirmed adequate strength. In vitro drug release study with ciprofloxacin-HCL as model drug showed 97.8 % release within 10 h, fitting to the Korsmeyer-Peppas model following diffusion and erosion mechanism. In vitro antimicrobial, anti-inflammatory assays, zebrafish toxicity, and animal studies in mice with SPH concluded it as a novel biomaterial.

Biodegradable Polymers in Biomedical Applications: A Review-Developments, Perspectives and Future Challenges

Biodegradable polymers are materials that, thanks to their remarkable properties, are widely understood to be suitable for use in scientific fields such as tissue engineering and materials engineering. Due to the alarming increase in the number of diagnosed diseases and conditions, polymers are of great interest in biomedical applications especially. The use of biodegradable polymers in biomedicine is constantly expanding. The application of new techniques or the improvement of existing ones makes it possible to produce materials with desired properties, such as mechanical strength, controlled degradation time and rate and antibacterial and antimicrobial properties. In addition, these materials can take virtually unlimited shapes as a result of appropriate design. This is additionally desirable when it is necessary to develop new structures that support or restore the proper functioning of systems in the body.

Research progress of biomimetic materials in oral medicine

Biomimetic materials are able to mimic the structure and functional properties of native tissues especially natural oral tissues. They have attracted growing attention for their potential to achieve configurable and functional reconstruction in oral medicine. Though tremendous progress has been made regarding biomimetic materials, significant challenges still remain in terms of controversy on the mechanism of tooth tissue regeneration, lack of options for manufacturing such materials and insufficiency of in vivo experimental tests in related fields. In this review, the biomimetic materials used in oral medicine are summarized systematically, including tooth defect, tooth loss, periodontal diseases and maxillofacial bone defect. Various theoretical foundations of biomimetic materials research are reviewed, introducing the current and pertinent results. The benefits and limitations of these materials are summed up at the same time. Finally, challenges and potential of this field are discussed. This review provides the framework and support for further research in addition to giving a generally novel and fundamental basis for the utilization of biomimetic materials in the future.

Apatite-coated outer layer eggshell membrane: A novel osteoinductive biohybrid composite for guided bone/tissue regeneration

Hybrid biomimetic materials aim to replicate the organic-inorganic constructs of mineralized tissues. During eggshell formation, the outer surface of the eggshell membrane (ESM) promotes calcium carbonate nucleation, while the inner one prevents mineralization toward the egg white and yolk. In the current study, the outer surface of the ESM acted as a heteronucleant in calcium phosphate precipitation by the vapor diffusion sitting drop method, while the inner one remained unmineralized. The aim was to fabricate a 2D biomaterial with dual functions, osteoinductive on one side and protective against cell invasion on the other side. The microstructural, physicochemical, morphological, and mechanical properties of the mineralized ESM were characterized by XRD, TGA, XPS, FTIR/Raman, HR-SEM, and mechanical testing techniques. The cytocompatibility and osteoinductive ability were assessed by biological assays of cell viability, proliferation, and osteogenic differentiation on human mesenchymal stromal cells (hMSCs). Results indicate that the outer surface of the ESM induces the heterogeneous precipitation of carbonate-apatite phase depicting biomimetic features. In addition, the apatite/ESM shows a much higher cytocompatibility than the pristine ESM and promotes the osteogenic differentiation of hMSCs more efficiently. Overall, the apatite/ESM composite exhibits compositional, crystalline, mechanical, and biological properties that resemble those of mineralized tissues, rendering it an approachable and novel material especially useful in guided tissue/bone regeneration.

Fracture mechanism and mechanical properties of porous HA/PLCL and HA/PLLA sandwich composite beams

Previously, we have developed a novel porous hydroxyapatite/poly l-lactic-co-caprolactone (HA/PLCL) composite sandwich beam as a new scaffold material for bone regeneration. This work presents the study of bending fracture mechanisms and microdamage of porous hydroxyapatite/poly L-lactic-acid (HA/PLLA) sandwich beam, in comparison to the previous developed HA/PLCL sandwich beam. Both beams were fabricated using the sandwich method in which the single porous composite beams were layered in between two porous polymer layers of their kind. Three-point bending tests were performed to assess their mechanical properties, and their microstructures along with the damage mechanisms were examined using field emission-scanning electron microscope (FE-SEM). Their crystalline structures and thermal properties were analyzed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, and differential scanning calorimetry (DSC) measurements. The microdamage and fracture mechanisms were then characterized by stepwise crack formations. It was found that HA/PLLA composite sandwich beam possessed higher mechanical properties compared to HA/PLCL sandwich beam, resulting from higher stiffness of PLLA polymer. PLCL layer showed a vast ductile fracture, with elongated PLCL strips, while the fracture surfaces observed on the PLLA layer have a relatively brittle fracture pattern with some polymeric pores that were still visible. Three stages of damage were observed on both beams with different locations of crack initiation, indicating that different polymer materials do affect the fracture behavior of each beam.

Development of Novel Polysaccharide Membranes for Guided Bone Regeneration: In Vitro and In Vivo Evaluations

INTRODUCTION

Guided bone regeneration (GBR) procedures require selecting suitable membranes for oral surgery. Pullulan and/or dextran-based polysaccharide materials have shown encouraging results in bone regeneration as bone substitutes but have not been used to produce barrier membranes. The present study aimed to develop and characterize pullulan/dextran-derived membranes for GBR.

MATERIALS AND METHODS

Two pullulan/dextran-based membranes, containing or not hydroxyapatite (HA) particles, were developed. In vitro, cytotoxicity evaluation was performed using human bone marrow mesenchymal stem cells (hBMSCs). Biocompatibility was assessed on rats in a subcutaneous model for up to 16 weeks. In vivo, rat femoral defects were created on 36 rats to compare the two pullulan/dextran-based membranes with a commercial collagen membrane (Bio-Gide®). Bone repair was assessed radiologically and histologically.

RESULTS

Both polysaccharide membranes demonstrated cytocompatibility and biocompatibility. Micro-computed tomography (micro-CT) analyses at two weeks revealed that the HA-containing membrane promoted a significant increase in bone formation compared to Bio-Gide®. At one month, similar effects were observed among the three membranes in terms of bone regeneration.

CONCLUSION

The developed pullulan/dextran-based membranes evidenced biocompatibility without interfering with bone regeneration and maturation. The HA-containing membrane, which facilitated early bone regeneration and offered adequate mechanical support, showed promising potential for GBR procedures.

Biomaterial composed of chitosan, riboflavin, and hydroxyapatite for bone tissue regeneration

Biomaterial engineering approaches involve using a combination of miscellaneous bioactive molecules which may promote cell proliferation and, thus, form a scaffold with the environment that favors the regeneration process. Chitosan, a naturally occurring biodegradable polymer, possess some essential features, i.e., biodegradability, biocompatibility, and in the solid phase good porosity, which may contribute to promote cell adhesion. Moreover, doping of the materials with other biocompounds will create a unique and multifunctional scaffold that will be useful in regenerative medicine. This study is focused on the manufacturing and characterization of composite materials based on chitosan, hydroxyapatite, and riboflavin. The resulting films were fabricated by the casting/solvent evaporation method. Morphological and spectroscopy analyses of the films revealed a porous structure and an interconnection between chitosan and apatite. The composite material showed an inhibitory effect on Staphylococcus aureus and exhibited higher antioxidant activity compared to pure chitosan. In vitro studies on riboflavin showed increased cell proliferation and migration of fibroblasts and osteosarcoma cells, thus demonstrating their potential for bone tissue engineering applications.

Polysaccharide-bioceramic composites for bone tissue engineering: A review

Limitations associated with conventional bone substitutes such as autografts, increasing demand for bone grafts, and growing elderly population worldwide necessitate development of unique materials as bone graft substitutes. Bone tissue engineering (BTE) would ensure therapy advancement, efficiency, and cost-effective treatment modalities of bone defects. One way of engineering bone tissue scaffolds by mimicking natural bone tissue composed of organic and inorganic phases is to utilize polysaccharide-bioceramic hybrid composites. Polysaccharides are abundant in nature, and present in human body. Biominerals, like hydroxyapatite are present in natural bone and some of them possess osteoconductive and osteoinductive properties. Ion doped bioceramics could substitute protein-based biosignal molecules to achieve osteogenesis, vasculogenesis, angiogenesis, and stress shielding. This review is a systemic summary on properties, advantages, and limitations of polysaccharide-bioceramic/ion doped bioceramic composites along with their recent advancements in BTE.

Drug Loaded 3D-Printed Poly(ε-Caprolactone) Scaffolds for Local Antibacterial or Anti-Inflammatory Treatment in Bone Regeneration

Annual bone grafting surgeries due to bone fractures, resections of affected bones, skeletal anomalies, osteoporosis, etc. exceed two million worldwide. In this regard, the creation of new materials for bone tissue repair is one of the urgent tasks of modern medicine. Additive manufacturing, or 3D printing, offers great opportunities for the development of materials with diverse properties and designs. In this study, the one-pot technique for the production of 3D scaffolds based on poly(ε-caprolactone) (PCL) loaded with an antibiotic or anti-inflammatory drug was proposed. In contrast to previously described methods to prepare drug-containing scaffolds, drug-loaded PCL scaffolds were prepared by direct 3D printing from a polymer/drug blend. An investigation of the mechanical properties of 3D-printed scaffolds containing 0.5-5 wt% ciprofloxacin (CIP) or dexamethasone (DEX) showed almost no effect of the drug (compression modulus ~70-90 MPa) compared to unfilled PCL (74 MPa). At the same time, introducing the drug and increasing its content in the PCL matrix contributed to a 1.8-6.8-fold decrease in the specific surface area of the scaffold, depending on composition. The release of CIP and DEX in phosphate buffer solution and in the same buffer containing lipase revealed a faster release in enzyme-containing medium within 45 days. Furthermore, drug release was more intensive from scaffolds with a low drug load. Analysis of the release profiles using a number of mathematical dissolution models led to the conclusion that diffusion dominates over other probable factors. In vitro biological evaluation of the scaffolds containing DEX showed moderate toxicity against osteoblast-like and leukemia monocytic cells. Being 3D-printed together with PCL both drugs retain their biological activity. PCL/CIP and PCL/DEX scaffolds demonstrated antibacterial properties against Pseudomonas aeruginosa (a total inhibition after 48 h) and anti-inflammatory activity in experiments on TNFα-activated monocyte cells (a 4-time reduction in CD-54 expression relative to control), respectively.

Flavonoid-Loaded Biomaterials in Bone Defect Repair

Skeletons play an important role in the human body, and can form gaps of varying sizes once damaged. Bone defect healing involves a series of complex physiological processes and requires ideal bone defect implants to accelerate bone defect healing. Traditional grafts are often accompanied by issues such as insufficient donors and disease transmission, while some bone defect implants are made of natural and synthetic polymers, which have characteristics such as good porosity, mechanical properties, high drug loading efficiency, biocompatibility and biodegradability. However, their antibacterial, antioxidant, anti-inflammatory and bone repair promoting abilities are limited. Flavonoids are natural compounds with various biological activities, such as antitumor, anti-inflammatory and analgesic. Their good anti-inflammatory, antibacterial and antioxidant activities make them beneficial for the treatment of bone defects. Several researchers have designed different types of flavonoid-loaded polymer implants for bone defects. These implants have good biocompatibility, and they can effectively promote the expression of angiogenesis factors such as VEGF and CD31, promote angiogenesis, regulate signaling pathways such as Wnt, p38, AKT, Erk and increase the levels of osteogenesis-related factors such as Runx-2, OCN, OPN significantly to accelerate the process of bone defect healing. This article reviews the effectiveness and mechanism of biomaterials loaded with flavonoids in the treatment of bone defects. Flavonoid-loaded biomaterials can effectively promote bone defect repair, but we still need to improve the overall performance of flavonoid-loaded bone repair biomaterials to improve the bioavailability of flavonoids and provide more possibilities for bone defect repair.

Synthetic Calcium-Phosphate Materials for Bone Grafting

Synthetic bone grafting materials play a significant role in various medical applications involving bone regeneration and repair. Their ability to mimic the properties of natural bone and promote the healing process has contributed to their growing relevance. While calcium-phosphates and their composites with various polymers and biopolymers are widely used in clinical and experimental research, the diverse range of available polymer-based materials poses challenges in selecting the most suitable grafts for successful bone repair. This review aims to address the fundamental issues of bone biology and regeneration while providing a clear perspective on the principles guiding the development of synthetic materials. In this study, we delve into the basic principles underlying the creation of synthetic bone composites and explore the mechanisms of formation for biologically important complexes and structures associated with the various constituent parts of these materials. Additionally, we offer comprehensive information on the application of biologically active substances to enhance the properties and bioactivity of synthetic bone grafting materials. By presenting these insights, our review enables a deeper understanding of the regeneration processes facilitated by the application of synthetic bone composites.

Human Bone-Marrow-Derived Stem-Cell-Seeded 3D Chitosan-Gelatin-Genipin Scaffolds Show Enhanced Extracellular Matrix Mineralization When Cultured under a Perfusion Flow in Osteogenic Medium

Tissue-engineered bone tissue grafts are a promising alternative to the more conventional use of natural donor bone grafts. However, choosing an appropriate biomaterial/scaffold to sustain cell survival, proliferation, and differentiation in a 3D environment remains one of the most critical issues in this domain. Recently, chitosan/gelatin/genipin (CGG) hybrid scaffolds have been proven as a more suitable environment to induce osteogenic commitment in undifferentiated cells when doped with graphene oxide (GO). Some concern is, however, raised towards the use of graphene and graphene-related material in medical applications. The purpose of this work was thus to check if the osteogenic potential of CGG scaffolds without added GO could be increased by improving the medium diffusion in a 3D culture of differentiating cells. To this aim, the level of extracellular matrix (ECM) mineralization was evaluated in human bone-marrow-derived stem cell (hBMSC)-seeded 3D CGG scaffolds upon culture under a perfusion flow in a dedicated custom-made bioreactor system. One week after initiating dynamic culture, histological/histochemical evaluations of CGG scaffolds were carried out to analyze the early osteogenic commitment of the culture. The analyses show the enhanced ECM mineralization of the 3D perfused culture compared to the static counterpart. The results of this investigation reveal a new perspective on more efficient clinical applications of CGG scaffolds without added GO.

The role of smart polymeric biomaterials in bone regeneration: a review

Addressing critical bone defects necessitates innovative solutions beyond traditional methods, which are constrained by issues such as immune rejection and donor scarcity. Smart polymeric biomaterials that respond to external stimuli have emerged as a promising alternative, fostering endogenous bone regeneration. Light-responsive polymers, employed in 3D-printed scaffolds and photothermal therapies, enhance antibacterial efficiency and bone repair. Thermo-responsive biomaterials show promise in controlled bioactive agent release, stimulating osteocyte differentiation and bone regeneration. Further, the integration of conductive elements into polymers improves electrical signal transmission, influencing cellular behavior positively. Innovations include advanced 3D-printed poly (l-lactic acid) scaffolds, polyurethane foam scaffolds promoting cell differentiation, and responsive polymeric biomaterials for osteogenic and antibacterial drug delivery. Other developments focus on enzyme-responsive and redox-responsive polymers, which offer potential for bone regeneration and combat infection. Biomaterials responsive to mechanical, magnetic, and acoustic stimuli also show potential in bone regeneration, including mechanically-responsive polymers, magnetic-responsive biomaterials with superparamagnetic iron oxide nanoparticles, and acoustic-responsive biomaterials. In conclusion, smart biopolymers are reshaping scaffold design and bone regeneration strategies. However, understanding their advantages and limitations is vital, indicating the need for continued exploratory research.

3D-printed fish gelatin scaffolds for cartilage tissue engineering

Knee osteoarthritis is a chronic disease caused by the deterioration of the knee joint due to various factors such as aging, trauma, and obesity, and the nonrenewable nature of the injured cartilage makes the treatment of osteoarthritis challenging. Here, we present a three-dimensional (3D) printed porous multilayer scaffold based on cold-water fish skin gelatin for osteoarticular cartilage regeneration. To make the scaffold, cold-water fish skin gelatin was combined with sodium alginate to increase viscosity, printability, and mechanical strength, and the hybrid hydrogel was printed according to a pre-designed specific structure using 3D printing technology. Then, the printed scaffolds underwent a double-crosslinking process to enhance their mechanical strength even further. These scaffolds mimic the structure of the original cartilage network in a way that allows chondrocytes to adhere, proliferate, and communicate with each other, transport nutrients, and prevent further damage to the joint. More importantly, we found that cold-water fish gelatin scaffolds were nonimmunogenic, nontoxic, and biodegradable. We also implanted the scaffold into defective rat cartilage for 12 weeks and achieved satisfactory repair results in this animal model. Thus, cold-water fish skin gelatin scaffolds may have broad application potential in regenerative medicine.

The Concept of Scaffold-Guided Bone Regeneration for the Treatment of Long Bone Defects: Current Clinical Application and Future Perspective

The treatment of bone defects remains a challenging clinical problem with high reintervention rates, morbidity, and resulting significant healthcare costs. Surgical techniques are constantly evolving, but outcomes can be influenced by several parameters, including the patient's age, comorbidities, systemic disorders, the anatomical location of the defect, and the surgeon's preference and experience. The most used therapeutic modalities for the regeneration of long bone defects include distraction osteogenesis (bone transport), free vascularized fibular grafts, the Masquelet technique, allograft, and (arthroplasty with) mega-prostheses. Over the past 25 years, three-dimensional (3D) printing, a breakthrough layer-by-layer manufacturing technology that produces final parts directly from 3D model data, has taken off and transformed the treatment of bone defects by enabling personalized therapies with highly porous 3D-printed implants tailored to the patient. Therefore, to reduce the morbidities and complications associated with current treatment regimens, efforts have been made in translational research toward 3D-printed scaffolds to facilitate bone regeneration. Three-dimensional printed scaffolds should not only provide osteoconductive surfaces for cell attachment and subsequent bone formation but also provide physical support and containment of bone graft material during the regeneration process, enhancing bone ingrowth, while simultaneously, orthopaedic implants supply mechanical strength with rigid, stable external and/or internal fixation. In this perspective review, we focus on elaborating on the history of bone defect treatment methods and assessing current treatment approaches as well as recent developments, including existing evidence on the advantages and disadvantages of 3D-printed scaffolds for bone defect regeneration. Furthermore, it is evident that the regulatory framework and organization and financing of evidence-based clinical trials remains very complex, and new challenges for non-biodegradable and biodegradable 3D-printed scaffolds for bone regeneration are emerging that have not yet been sufficiently addressed, such as guideline development for specific surgical indications, clinically feasible design concepts for needed multicentre international preclinical and clinical trials, the current medico-legal status, and reimbursement. These challenges underscore the need for intensive exchange and open and honest debate among leaders in the field. This goal can be addressed in a well-planned and focused stakeholder workshop on the topic of patient-specific 3D-printed scaffolds for long bone defect regeneration, as proposed in this perspective review.

Freeze-Drying Process for the Fabrication of Collagen-Based Sponges as Medical Devices in Biomedical Engineering

This paper presents a systematic review of a key sector of the much promising and rapidly evolving field of biomedical engineering, specifically on the fabrication of three-dimensional open, porous collagen-based medical devices, using the prominent freeze-drying process. Collagen and its derivatives are the most popular biopolymers in this field, as they constitute the main components of the extracellular matrix, and therefore exhibit desirable properties, such as biocompatibility and biodegradability, for in vivo applications. For this reason, freeze-dried collagen-based sponges with a wide variety of attributes can be produced and have already led to a wide range of successful commercial medical devices, chiefly for dental, orthopedic, hemostatic, and neuronal applications. However, collagen sponges display some vulnerabilities in other key properties, such as low mechanical strength and poor control of their internal architecture, and therefore many studies focus on the settlement of these defects, either by tampering with the steps of the freeze-drying process or by combining collagen with other additives. Furthermore, freeze drying is still considered a high-cost and time-consuming process that is often used in a non-optimized manner. By applying an interdisciplinary approach and combining advances in other technological fields, such as in statistical analysis, implementing the Design of Experiments, and Artificial Intelligence, the opportunity arises to further evolve this process in a sustainable and strategic manner, and optimize the resulting products as well as create new opportunities in this field.

Nanogels for bone tissue engineering - from synthesis to application

Nanogels are cross-linked hydrogel nanoparticles with a three-dimensional, tunable porous structure that merges the best features of hydrogels and nanoparticles, including the ability to retain their hydrated nature and to swell and shrink in response to environmental changes. Nanogels have attracted increasing attention for use in bone tissue engineering as scaffolds for growth factor transport and cell adhesion. Their three-dimensional structures allow the encapsulation of a wide range of hydrophobic and hydrophilic drugs, enhance their half-life, and impede their enzymatic breakdown in vivo. Nanogel-based scaffolds are a viable treatment modality for enhanced bone regeneration. They act as carriers for cells and active ingredients capable of controlled release, enhanced mechanical support, and osteogenesis for enhanced bone tissue regeneration. However, the development of such nanogel constructs might involve combinations of several biomaterials to fabricate active ingredients that can control release, enhance mechanical support, and facilitate osteogenesis for more effective bone tissue regeneration. Hence, this review aims to highlight the potential of nanogel-based scaffolds to address the needs of bone tissue engineering.

Recent Advancements in Electrospun Chitin and Chitosan Nanofibers for Bone Tissue Engineering Applications

Treatment of large segmental bone loss caused by fractures, osteomyelitis, and non-union results in expenses of around USD 300,000 per case. Moreover, the worst-case scenario results in amputation in 10% to 14.5% of cases. Biomaterials, cells, and regulatory elements are employed in bone tissue engineering (BTE) to create biosynthetic bone grafts with effective functionalization that can aid in the restoration of such fractured bones, preventing amputation and alleviating expenses. Chitin (CT) and chitosan (CS) are two of the most prevalent natural biopolymers utilized in the fields of biomaterials and BTE. To offer the structural and biochemical cues for augmenting bone formation, CT and CS can be employed alone or in combination with other biomaterials in the form of nanofibers (NFs). When compared with several fabrication methods available to produce scaffolds, electrospinning is regarded as superior since it enables the development of nanostructured scaffolds utilizing biopolymers. Electrospun nanofibers (ENFs) offer unique characteristics, including morphological resemblance to the extracellular matrix, high surface-area-to-volume ratio, permeability, porosity, and stability. This review elaborates on the recent strategies employed utilizing CT and CS ENFs and their biocomposites in BTE. We also summarize their implementation in supporting and delivering an osteogenic response to treat critical bone defects and their perspectives on rejuvenation. The CT- and CS-based ENF composite biomaterials show promise as potential constructions for bone tissue creation.

Overexpression of fibroblast growth factor receptor 2 in bone marrow mesenchymal stem cells enhances osteogenesis and promotes critical cranial bone defect regeneration

Background: Reconstruction of cranial bone defects is one of the most challenging problems in reconstructive surgery, and several biological tissue engineering methods have been used to promote bone repair, such as genetic engineering of bone marrow mesenchymal stem cells (BMSCs). Fibroblast growth factor receptor 2 (Fgfr2) is an important regulator of bone construction and can be used as a potential gene editing site. However, its role in the osteogenesis process of BMSCs remains unclear. This article clarifies the function of Fgfr2 in BMSCs and explores the role of Fgfr2-overexpressed BMSCs carried by light-induced porous hydrogel (GelMA) in the repair of cranial bone defects. Methods: Lenti-virus was used to overexpress Fgfr2 in BMSCs, and cell counting kit-8, transwell, and flow cytometry assays were conducted to investigate the proliferation, migration, and characteristics. After 0, 3, 7, and 10 days of osteogenic or chondrogenic induction, the changes in osteogenic and chondrogenic ability were detected by real-time PCR, western blot, alkaline phosphatase staining, alizarin Red staining, and alcian blue staining. To investigate the viability of BMSCs carried by GelMA, calcein and propyl iodide staining were carried out as well. Finally, a critical cranial bone defect model was established in 6-week-old male mice and micro-computerized tomography, masson staining, and immunohistochemistry of OCN were conducted to test the bone regeneration properties of implanting Fgfr2-overexpressed BMSCs with GelMA in cranial bone defects over 6 weeks. Results: Overexpression of Fgfr2 in BMSCs significantly promoted cell proliferation and migration and increased the percentage of CD200+CD105+ cells. After osteogenic and chondrogenic induction, Fgfr2 overexpression enhanced both osteogenic and chondrogenic ability. Furthermore, in cranial bone defect regeneration, BMSCs carried by light-induced GelMA showed favorable biocompatibility, and Fgfr2-overexpressed BMSCs induced superior cranial bone regeneration compared to a normal BMSCs group and an untreated blank group. Conclusion: In vitro, Fgfr2 enhanced the proliferation, migration, and stemness of BMSCs and promoted osteogenesis and chondrogenesis after parallel induction. In vivo, BMSCs with Fgfr2 overexpression carried by GelMA showed favorable performance in treating critical cranial bone defects. This study clarifies the multiple functions of Fgfr2 in BMSCs and provides a new method for future tissue engineering.

Polylevolysine and Fibronectin-Loaded Nano-Hydroxyapatite/PGLA/Dextran-Based Scaffolds for Improving Bone Regeneration: A Histomorphometric in Animal Study

The regeneration of large bone defects is still demanding, requiring biocompatible scaffolds, with osteoconductive and osteoinductive properties. This study aimed to assess the pre-clinical efficacy of a nano-hydroxyapatite (nano-HA)/PGLA/dextran-based scaffold loaded with Polylevolysine (PLL) and fibronectin (FN), intended for bone regeneration of a critical-size tibial defect, using an ovine model. After physicochemical characterization, the scaffolds were implanted in vivo, producing two monocortical defects on both tibiae of ten adult sheep, randomly divided into two groups to be euthanized at three and six months after surgery. The proximal left and right defects were filled, respectively, with the test scaffold (nano-HA/PGLA/dextran-based scaffold loaded with PLL and FN) and the control scaffold (nano-HA/PGLA/dextran-based scaffold not loaded with PLL and FN); the distal defects were considered negative control sites, not receiving any scaffold. Histological and histomorphometric analyses were performed to quantify the bone ingrowth and residual material 3 and 6 months after surgery. In both scaffolds, the morphological analyses, at the SEM, revealed the presence of submicrometric crystals on the surfaces and within the scaffolds, while optical microscopy showed a macroscopic 3D porous architecture. XRD confirmed the presence of nano-HA with a high level of crystallinity degree. At the histological and histomorphometric evaluation, new bone formation and residual biomaterial were detectable inside the defects 3 months after intervention, without differences between the scaffolds. At 6 months, the regenerated bone was significantly higher in the defects filled with the test scaffold (loaded with PLL and FN) than in those filled with the control scaffold, while the residual material was higher in correspondence to the control scaffold. Nano-HA/PGLA/dextran-based scaffolds loaded with PLL and FN appear promising in promoting bone regeneration in critical-size defects, showing balanced regenerative and resorbable properties to support new bone deposition.

Application of Biomedical Microspheres in Wound Healing

Tissue injury, one of the most common traumatic injuries in daily life, easily leads to secondary wound infections. To promote wound healing and reduce scarring, various kinds of wound dressings, such as gauze, bandages, sponges, patches, and microspheres, have been developed for wound healing. Among them, microsphere-based tissue dressings have attracted increasing attention due to the advantage of easy to fabricate, excellent physicochemical performance and superior drug release ability. In this review, we first introduced the common methods for microspheres preparation, such as emulsification-solvent method, electrospray method, microfluidic technology as well as phase separation methods. Next, we summarized the common biomaterials for the fabrication of the microspheres including natural polymers and synthetic polymers. Then, we presented the application of the various microspheres from different processing methods in wound healing and other applications. Finally, we analyzed the limitations and discussed the future development direction of microspheres in the future.

Recent Advance of Strontium Functionalized in Biomaterials for Bone Regeneration

Bone defect disease causes damage to people’s lives and property, and how to effectively promote bone regeneration is still a big clinical challenge. Most of the current repair methods focus on filling the defects, which has a poor effect on bone regeneration. Therefore, how to effectively promote bone regeneration while repairing the defects at the same time has become a challenge for clinicians and researchers. Strontium (Sr) is a trace element required by the human body, which mainly exists in human bones. Due to its unique dual properties of promoting the proliferation and differentiation of osteoblasts and inhibiting osteoclast activity, it has attracted extensive research on bone defect repair in recent years. With the deep development of research, the mechanisms of Sr in the process of bone regeneration in the human body have been clarified, and the effects of Sr on osteoblasts, osteoclasts, mesenchymal stem cells (MSCs), and the inflammatory microenvironment in the process of bone regeneration have been widely recognized. Based on the development of technology such as bioengineering, it is possible that Sr can be better loaded onto biomaterials. Even though the clinical application of Sr is currently limited and relevant clinical research still needs to be developed, Sr-composited bone tissue engineering biomaterials have achieved satisfactory results in vitro and in vivo studies. The Sr compound together with biomaterials to promote bone regeneration will be a development direction in the future. This review will present a brief overview of the relevant mechanisms of Sr in the process of bone regeneration and the related latest studies of Sr combined with biomaterials. The aim of this paper is to highlight the potential prospects of Sr functionalized in biomaterials.

The Delivery and Activation of Growth Factors Using Nanomaterials for Bone Repair

Bone regeneration is a comprehensive process that involves different stages, and various growth factors (GFs) play crucial roles in the entire process. GFs are currently widely used in clinical settings to promote bone repair; however, the direct application of GFs is often limited by their fast degradation and short local residual time. Additionally, GFs are expensive, and their use may carry risks of ectopic osteogenesis and potential tumor formation. Nanomaterials have recently shown great promise in delivering GFs for bone regeneration, as they can protect fragile GFs and control their release. Moreover, functional nanomaterials can directly activate endogenous GFs, modulating the regeneration process. This review provides a summary of the latest advances in using nanomaterials to deliver exogenous GFs and activate endogenous GFs to promote bone regeneration. We also discuss the potential for synergistic applications of nanomaterials and GFs in bone regeneration, along with the challenges and future directions that need to be addressed.

Biodegradable Polymer Electrospinning for Tendon Repairment

With the degradation after aging and the destruction of high-intensity exercise, the frequency of tendon injury is also increasing, which will lead to serious pain and disability. Due to the structural specificity of the tendon tissue, the traditional treatment of tendon injury repair has certain limitations. Biodegradable polymer electrospinning technology with good biocompatibility and degradability can effectively repair tendons, and its mechanical properties can be achieved by adjusting the fiber diameter and fiber spacing. Here, this review first briefly introduces the structure and function of the tendon and the repair process after injury. Then, different kinds of biodegradable natural polymers for tendon repair are summarized. Then, the advantages and disadvantages of three-dimensional (3D) electrospun products in tendon repair and regeneration are summarized, as well as the optimization of electrospun fiber scaffolds with different bioactive materials and the latest application in tendon regeneration engineering. Bioactive molecules can optimize the structure of these products and improve their repair performance. Importantly, we discuss the application of the 3D electrospinning scaffold's superior structure in different stages of tendon repair. Meanwhile, the combination of other advanced technologies has greater potential in tendon repair. Finally, the relevant patents of biodegradable electrospun scaffolds for repairing damaged tendons, as well as their clinical applications, problems in current development, and future directions are summarized. In general, the use of biodegradable electrospun fibers for tendon repair is a promising and exciting research field, but further research is needed to fully understand its potential and optimize its application in tissue engineering.

Exploring the biomedical competency of gamma-radiation aided hydroxyapatite and its composite fabricated with nano-cellulose and chitosan

The well-known biomaterial Ca-hydroxyapatite (Hap) in its pristine form holds the top ranking position in the field of biomedical research and extensive investigation is continuing across the globe to enhance its competency. Hence, having the intention to introduce superior physiognomies (e.g. cytotoxicity, haemocompatibility, and bioactivity coupled with antimicrobial and antioxidant activity) in Hap, in this research work, we exposed Hap to 200 kGy γ-radiation. As a result, γ-radiated Hap exhibited extreme antimicrobial (more than 98%) and moderate (∼34%) antioxidant properties. On the other hand, cytotoxicity and haemocompatibility of γ-radiated Hap were in good agreement with the ISO 10993-5 and ISO 10993-4 standards respectively. Since, bone and joint infections as well as degenerative disorders e.g. osteoarthritis, osteomyelitis, bone injury, and spinal problems have emerged as serious issues and urge a remedial way out, application of γ-radiated Hap could be a promising solution in this regard.

Unravelling the role of individual components in pBAE/polynucleotide polyplexes in the synthesis of tailored carriers for specific applications: on the road to rational formulations

Oligopeptide end-modified poly(β-amino ester)s (OM-pBAEs) offer a means for the effective implementation of gene therapeutics in the near future. A fine-tuning of OM-pBAEs to meet application requirements is achieved by the proportional balance of oligopeptides used and provide gene carriers with high transfection efficacy, low toxicity, precise targeting, biocompatibility, and biodegradability. Understanding the influence and conformation of each building block at molecular and biological levels is therefore pivotal for further development and improvement of these gene carriers. Herein, we unmask the role of individual OM-pBAE components and their conformation in OM-pBAE/polynucleotide nanoparticles using a combination of fluorescence resonance energy transfer, enhanced darkfield spectral microscopy, atomic force microscopy, and microscale thermophoresis. We found that modifying the pBAE backbone with three end-terminal amino acids produces unique mechanical and physical properties for each combination. Higher adhesion properties are seen with arginine and lysine-based hybrid nanoparticles, while histidine provides an advantage in terms of construct stability. Our results shed light on the high potential of OM-pBAEs as gene delivery vehicles and provide insights into the influence of the nature of surface charges and the chemical nature of the pBAE modifications on their paths towards endocytosis, endosomal escape, and transfection.

Cell Behavior Changes and Enzymatic Biodegradation of Hybrid Electrospun Poly(3-hydroxybutyrate)-Based Scaffolds with an Enhanced Piezoresponse after the Addition of Reduced Graphene Oxide

This is the first comprehensive study of the impact of biodegradation on the structure, surface potential, mechanical and piezoelectric properties of poly(3-hydroxybutyrate) (PHB) scaffolds supplemented with reduced graphene oxide (rGO) as well as cell behavior under static and dynamic mechanical conditions. There is no effect of the rGO addition up to 1.0 wt% on the rate of enzymatic biodegradation of PHB scaffolds for 30 d. The biodegradation of scaffolds leads to the depolymerization of the amorphous phase, resulting in an increase in the degree of crystallinity. Because of more regular dipole order in the crystalline phase, surface potential of all fibers increases after the biodegradation, with a maximum (361 ± 5 mV) after the addition of 1 wt% rGO into PHB as compared to pristine PHB fibers. By contrast, PHB-0.7rGO fibers manifest the strongest effective vertical (0.59 ± 0.03 pm V^-1 ) and lateral (1.06 ± 0.02 pm V^-1 ) piezoresponse owing to a greater presence of electroactive β-phase. In vitro assays involving primary human fibroblasts reveal equal biocompatibility and faster cell proliferation on PHB-0.7rGO scaffolds compared to pure PHB and nonpiezoelectric polycaprolactone scaffolds. Thus, the developed biodegradable PHB-rGO scaffolds with enhanced piezoresponse are promising for tissue-engineering applications.

Cellulose nanocrystals vs. cellulose nanospheres: A comparative study of cytotoxicity and macrophage polarization potential

Nanocellulose application has been increasing owing to its appealing physicochemical properties. Monitoring of the crystallinity, surface topography, and reactivity of this high-aspect-ratio nanomaterial is crucial for efficient tissue engineering. Controlling macrophage polarization phenotype remains a challenge in regenerative medicine and tissue engineering. Herein, we monitored the effects of shape-regulated (rod and spherical) nanocellulose on the macrophage modulatory potential of RAW 246.7 cells in vitro. Spherical nanocellulose (s-NC) exhibited higher thermal stability and biocompatibility than rod nanocellulose. Macrophage polarization was profoundly affected by nanocellulose topography and incubation period. M2 polarization was observed in vitro after 1 day of treatment with s-NC, followed by M1 polarization after treatment for longer periods. Transcriptome analysis similarly revealed that M1 polarization was dominant after 1 day h of incubation with both nanocellulose types. These findings demonstrate that macrophage polarization can be controlled by selecting suitable nanocellulose shape and incubation time for desired applications.

Drug/bioactive eluting chitosan composite foams for osteochondral tissue engineering

Joint defects associated with a variety of etiologies often extend deep into the subchondral bone leading to functional impairment and joint immobility, and it is a very challenging task to regenerate the bone-cartilage interface offering significant opportunities for biomaterial-based interventions to improve the quality of life of patients. Herein drug-/bioactive-loaded porous tissue scaffolds incorporating nano-hydroxyapatite (nHAp), chitosan (CS) and either hydroxypropyl methylcellulose (HPMC) or Bombyx mori silk fibroin (SF) are fabricated through freeze drying method as subchondral bone substitute. A combination of spectroscopy and microscopy (Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and X-ray fluorescence (XRF) were used to analyze the structure of the porous biomaterials. The compressive mechanical properties of these scaffolds are biomimetic of cancellous bone tissues and capable of releasing drugs/bioactives (exemplified with triamcinolone acetonide, TA, or transforming growth factor-β1, TGF-β1, respectively) over a period of days. Mouse preosteoblast MC3T3-E1 cells were observed to adhere and proliferate on the tissue scaffolds as confirmed by the cell attachment, live-dead assay and alamarBlue™ assay. Interestingly, RT-qPCR analysis showed that the TA downregulated inflammatory biomarkers and upregulated the bone-specific biomarkers, suggesting such tissue scaffolds have long-term potential for clinical application.

Recent Developments in Polymer Nanocomposites for Bone Regeneration

Most people who suffer acute injuries in accidents have fractured bones. Many of the basic processes that take place during embryonic skeletal development are replicated throughout the regeneration process that occurs during this time. Bruises and bone fractures, for example, serve as excellent examples. It almost always results in a successful recovery and restoration of the structural integrity and strength of the broken bone. After a fracture, the body begins to regenerate bone. Bone formation is a complex physiological process that requires meticulous planning and execution. A normal healing procedure for a fracture might reveal how the bone is constantly rebuilding as an adult. Bone regeneration is becoming more dependent on polymer nanocomposites, which are composites made up of a polymer matrix and a nanomaterial. This study will review polymer nanocomposites that are employed in bone regeneration to stimulate bone regeneration. As a result, we will introduce the role of bone regeneration nanocomposite scaffolds, and the nanocomposite ceramics and biomaterials that play a role in bone regeneration. Aside from that, recent advances in polymer nanocomposites might be used in a variety of industrial processes to help people with bone defects overcome their challenges will be discussed.

Biomedical materials for wound dressing: recent advances and applications

Wound healing is vital to maintain the physiological functions of the skin. The most common treatment is the use of a dressing to cover the wound and reduce infection risk and the rate of secondary injuries. Modern wound dressings have been the top priority choice for healing various types of wounds owing to their outstanding biocompatibility and biodegradability. In addition, they also maintain temperature and a moist environment, aid in pain relief, and improve hypoxic environments to stimulate wound healing. Due to the different types of wounds, as well as the variety of advanced wound dressing products, this review will provide information on the clinical characteristics of the wound, the properties of common modern dressings, and the in vitro, in vivo as well as the clinical trials on their effectiveness. The most popular types commonly used in producing modern dressings are hydrogels, hydrocolloids, alginates, foams, and films. In addition, the review also presents the polymer materials for dressing applications as well as the trend of developing these current modern dressings to maximize their function and create ideal dressings. The last is the discussion about dressing selection in wound treatment and an estimate of the current development tendency of new materials for wound healing dressings.

Rationally designed bioactive milk-derived protein scaffolds enhanced new bone formation

Recently, a number of studies reported that casein was composed of various multifunctional bioactive peptides such as casein phosphopeptide and β-casochemotide-1 that bind calcium ions and induce macrophage chemotaxis, which is crucial for bone homeostasis and bone fracture repair by cytokines secreted in the process. We hypothesized that the effects of the multifunctional biopeptides in casein would contribute to improving bone regeneration. Thus, we designed a tissue engineering platform that consisted of casein and polyvinyl alcohol, which was a physical-crosslinked scaffold (milk-derived protein; MDP), via simple freeze-thaw cycles and performed surface modification using 3,4-dihydroxy-l-phenylalanine (DOPA), a mussel adhesive protein, for immobilizing adhesive proteins and cytokines for recruiting cells in vivo (MDP-DOPA). Both the MDP and MDP-DOPA groups proved indirectly contribution of macrophages migration as RAW 264.7 cells were highly migrated toward materials by contained bioactive peptides. We implanted MDP and MDP-DOPA in a mouse calvarial defect orthotopic model and evaluated whether MDP-DOPA showed much faster mineral deposition and higher bone density than that of the no-treatment and MDP groups. The MDP-DOPA group showed the accumulation of host M2 macrophages and mesenchymal stem cells (MSCs) around the scaffold, whereas MDP presented mostly M1 macrophages in the early stage.

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Bioactive peptide-containing scaffold was fabricated via simple freeze-thaw cycles, and subsequently, the surface was modified with adhesive protein.

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We confirmed that the multifunctional biopeptides regulated the migration of macrophages and enhanced osteogenic differentiation.

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The bioactive peptide-containing scaffold showed much faster and higher mineral deposition in vivo animal studies compared to the other groups.

Synergistic effects of 3D chitosan-based hybrid scaffolds and mesenchymal stem cells in orthopaedic tissue engineering

Restoration of damaged bone and cartilage tissue with biomaterial scaffolds is an area of interest in orthopaedics. Chitosan is among the low-cost biomaterials used as scaffolds with considerable biocompability to almost every human tissue. Considerable osteoconductivity, porosity, and appropriate pore size distribution have made chitosan an appropriate scaffold for loading of stem cells and a good homing place for differentiation of stem cells to bone tissue. Moreover, the similarity of chitosan to glycosaminoglycans and its potential to be used as soft gels, which could be lasting more than 1 week in mobile chondral defects, has made chitosan a polymer of interest in repairing bone and cartilage defects. Different types of scaffolds using chitosan in combination with mesenchymal stem cells (MSCs) are discussed. MSCs are widely used in regenerative medicine because of their regenerative ability, and recent line evidence reviewed demonstrated that the combination of MSCs with a combination of chitosan with different materials, including collagen type 1, hyaluronic acid, Poly(L-lacticacid)/gelatin/β-tricalcium phosphate, gamma-poly[glutamic acid] polyelectrolyte/titanium alloy, modified Poly(L-Lactide-co-Epsilon-Caprolactone), calcium phosphate, β-glycerophosphate hydrogel/calcium phosphate cement (CPC), and CPC-Chitosan-RGD, can increase the efficacy of using MSCs, and chitosan-based stem cell delivery can be a promising method in restoration of damaged bone and cartilage tissue.

Characteristic Evaluation of Recombinant MiSp/Poly(lactic-co-glycolic) Acid (PLGA) Nanofiber Scaffolds as Potential Scaffolds for Bone Tissue Engineering

Biomaterial-based nanofibrous scaffolds are the most effective alternative to bone transplantation therapy. Here, two recombinant minor ampullate spidroins (spider silk proteins), R1SR2 and NR1SR2C, were blended with Poly(lactic-co-glycolic) Acid (PLGA), respectively, to generate nanofiber scaffolds by electrospinning. The N-terminal (N), C-terminal (C), repeating (R1 and R2) and spacer (S) modules were all derived from the minor ampullate spidroins (MiSp). The physical properties and structures of the blended scaffolds were measured by scanning electron microscopy (SEM), water contact angle measurement, Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), and Tensile mechanical testing. The results showed that blending of MiSp (R1SR2 and NR1SR2C) reduced the diameter of nanofibers, increased the porosity and glass transition temperatures of nanofibrous scaffolds, and effectively improved the hydrophilicity and ultimate strain of scaffolds. It is worth noting that the above changes were more significant in the presence of the N- and C-termini of MiSp. In cell culture assays, human bone mesenchymal stem cells (HBMSCs) grown on NR1SR2C/PLGA (20/80) scaffolds displayed markedly enhanced proliferative and adhesive abilities compared with counterparts grown on pure PLGA scaffolds. Jointly, these findings indicated recombinant MiSp/PLGA, particularly NR1SR2C/PLGA (20/80) blend nanofibrous scaffolds, is promising for bone tissue engineering.

Management of bone diseases: looking at scaffold-based strategies for drug delivery

The bone tissue can regenerate itself completely and continuously; however, large-scale bone defects may overpower this self-regenerative process. Furthermore, the aging population, the increment in obesity incidence, and the sedentary lifestyles are serious risk factors for bone diseases' development which are associated with the self-regenerative process's failure, high morbidity, and mortality rates. Thus, there is an ever-growing need for strategic approaches targeting bone replacement, its remodelling, and its regeneration. Bone scaffolds have successfully been used as synthetic bone grafts for many years, yet recent bone tissue engineering strategies attempt to explore their multifunctionality by investigating them as drug delivery systems. Bone diseases' treatments can be substantially difficult due to the avascular nature of the surrounding cartilage; thus, targeted drug delivery to the bone can be advantageous: it provides local high drug concentrations and minimizes adverse effects while securing a space for new, healthy tissue growth. Despite the promising scientific progress, studies underlining bone scaffolds' use as local drug delivery systems are not abundant. Hence, this work reviews bone scaffolds' therapeutic interest for local drug delivery in five distinct bone disorders-osteomyelitis, osteoporosis, osteoarthritis, osteosarcoma, and cancer bone metastasis. Additionally, it presents the challenges of this possible therapeutic approach and its future perspectives. Albeit bone scaffolds present therapeutic benefits by acting as drug delivery systems, further pre-clinical and clinical assessments are needed to strengthen their understanding and enable research evidence translation into clinical practice. The mismatch between scientific evolution and regulatory frameworks remains one of the major future challenges.

The Mechanical, Thermal, and Chemical Properties of PLA-Mg Filaments Produced via a Colloidal Route for Fused-Filament Fabrication

The effect of Mg particles on the thermal, chemical, physical, and primarily mechanical properties of 3D-printed PLA/Mg composites is studied in this paper. Recently, new colloidal processing has been proposed to introduce Mg particles into the PLA matrix, which ensures good dispersion of the particles and better thermal properties, allowing for thermal processing routes such as extrusion or 3D printing via fused-filament fabrication. The thermal and physical properties are here studied in 1D single-filament-printed PLA/Mg composites with 0 to 10 wt.% of Mg particles by Differential Scanning Calorimetry (DSC); we analyse the PLA chain modifications produced, the crystallinity fraction, and the different crystalline forms of the PLA after thermal processing. Fourier Transform Infrared Spectroscopy (FTIR) is used to confirm the influence of the PLA/Mg colloidal processing after printing. The mechanical properties are measured with a universal tensile test machine on the 1D single-printed filaments via fused-filament fabrication (FFF); the filaments were naturally aged to stable conditions. Filaments with and without a notch are studied to obtain the materials' tensile strength, elastic modulus, and fracture toughness. Different analytical models to explain the results of the PLA-Mg were studied, in which the minimum values for the interface strength of the PLA-Mg composites were calculated.

Natural Coatings and Surface Modifications on Magnesium Alloys for Biomedical Applications

Magnesium (Mg) alloys have great potential in biomedical applications due to their incomparable properties regarding other metals, such as stainless steels, Co-Cr alloys, and titanium (Ti) alloys. However, when Mg engages with body fluids, its degradation rate increases, inhibiting the complete healing of bone tissue. For this reason, it has been necessary to implement protective coatings to control the rate of degradation. This review focuses on natural biopolymer coatings used on Mg alloys for resorbable biomedical applications, as well as some modification techniques implemented before applying natural polymer coatings to improve their performance. Issues such as improving the corrosion resistance, cell adhesion, proliferation, and biodegradability of natural biopolymers are discussed through their basic comparison with inorganic-type coatings. Emphasis is placed on the expected biological behavior of each natural polymer described, to provide basic information as a reference on this topic.

Design strategies for composite matrix and multifunctional polymeric scaffolds with enhanced bioactivity for bone tissue engineering

Over the past few decades, various bioactive material-based scaffolds were investigated and researchers across the globe are actively involved in establishing a potential state-of-the-art for bone tissue engineering applications, wherein several disciplines like clinical medicine, materials science, and biotechnology are involved. The present review article's main aim is to focus on repairing and restoring bone tissue defects by enhancing the bioactivity of fabricated bone tissue scaffolds and providing a suitable microenvironment for the bone cells to fasten the healing process. It deals with the various surface modification strategies and smart composite materials development that are involved in the treatment of bone tissue defects. Orthopaedic researchers and clinicians constantly focus on developing strategies that can naturally imitate not only the bone tissue architecture but also its functional properties to modulate cellular behaviour to facilitate bridging, callus formation and osteogenesis at critical bone defects. This review summarizes the currently available polymeric composite matrices and the methods to improve their bioactivity for bone tissue regeneration effectively.

Comparative Efficiency of Gene-Activated Matrices Based on Chitosan Hydrogel and PRP Impregnated with BMP2 Polyplexes for Bone Regeneration

Gene therapy is one of the most promising approaches in regenerative medicine. Gene-activated matrices provide stable gene expression and the production of osteogenic proteins in situ to stimulate osteogenesis and bone repair. In this study, we developed new gene-activated matrices based on polylactide granules (PLA) impregnated with BMP2 polyplexes and included in chitosan hydrogel or PRP-based fibrin hydrogel. The matrices showed high biocompatibility both in vitro with mesenchymal stem cells and in vivo when implanted intramuscularly in rats. The use of porous PLA granules allowed the inclusion of a high concentration of polyplexes, and the introduction of the granules into hydrogel provided the gradual release of the plasmid constructs. All gene-activated matrices showed transfecting ability and ensured long-term gene expression and the production of target proteins in vitro. At the same time, the achieved concentration of BMP-2 was sufficient to induce osteogenic differentiation of MSCs. When implanted into critical-size calvarial defects in rats, all matrices with BMP2 polyplexes led to new bone formation. The most significant effect on osteoinduction was observed for the PLA/PRP matrices. Thus, the developed gene-activated matrices were shown to be safe and effective osteoplastic materials. PLA granules and PRP-based fibrin hydrogel containing BMP2 polyplexes were shown to be the most promising for future applications in bone regeneration.

Silk Sericin: A Promising Sustainable Biomaterial for Biomedical and Pharmaceutical Applications

Silk is a natural composite fiber composed mainly of hydrophobic fibroin and hydrophilic sericin, produced by the silkworm Bombyx mori. In the textile industry, the cocoons of B. mori are processed into silk fabric, where the sericin is substantially removed and usually discarded in wastewater. This wastewater pollutes the environment and water sources. However, sericin has been recognized as a potential biomaterial due to its biocompatibility, immunocompatibility, biodegradability, anti-inflammatory, antibacterial, antioxidant and photoprotective properties. Moreover, sericin can produce hydrogels, films, sponges, foams, dressings, particles, fibers, etc., for various biomedical and pharmaceutical applications (e.g., tissue engineering, wound healing, drug delivery, cosmetics). Given the severe environmental pollution caused by the disposal of sericin and its beneficial properties, there has been growing interest in upcycling this biomaterial, which could have a strong and positive economic, social and environmental impact.

Preparation and In Vitro Osteogenic Evaluation of Biomimetic Hybrid Nanocomposite Scaffolds Based on Gelatin/Plasma Rich in Growth Factors (PRGF) and Lithium-Doped 45s5 Bioactive Glass Nanoparticles

Bone tissue engineering is an emerging technique for repairing large bone lesions. Biomimetic techniques expand the use of organic-inorganic spongy-like nanocomposite scaffolds and platelet concentrates. In this study, a biomimetic nanocomposite scaffold was prepared using lithium-doped bioactive-glass nanoparticles and gelatin/PRGF. First, sol-gel method was used to prepare bioactive-glass nanoparticles that contain 0, 1, 3, and 5%wt lithium. The lithium content was then optimized based on antibacterial and MTT testing. By freeze-drying, hybrid scaffolds comprising 5, 10, and 20% bioglass were made. On the scaffolds, human endometrial stem cells (hEnSCs) were cultured for adhesion (SEM), survival, and osteogenic differentiation. Alkaline phosphatase activity and osteopontin, osteocalcin, and Runx2 gene expression were measured. The effect of bioactive-glass nanoparticles and PRGF on nanocomposites' mechanical characteristics and glass-transition temperature (T _g) was also studied. An optimal lithium content in bioactive glass structure was found to be 3% wt. Nanoparticle SEM examination indicated grain deformation due to different sizes of lithium and sodium ions. Results showed up to 10% wt bioactive-glass and PRGF increased survival and cell adhesion. Also, Hybrid scaffolds revealed higher ALP-activity and OP, OC, and Runx2 gene expression. Furthermore, bioactive-glass has mainly increased ALP-activity and Runx2 expression, whereas PRGF increases the expression of OP and OC genes. Bioactive-glass increases scaffold modulus and T _g continuously. Hence, the presence of both bioactive-glass and nanocomposite scaffold improves the expression of osteogenic differentiation biomarkers. Subsequently, it seems that hybrid scaffolds based on biopolymers, Li-doped bioactive-glass, and platelet extracts can be a good strategy for bone repair.

Films, Gels and Electrospun Fibers from Serum Albumin Globular Protein for Medical Device Coating, Biomolecule Delivery and Regenerative Engineering

Albumin is a natural biomaterial that is abundantly available in blood and body fluids. It is clinically used as a plasma expander, thereby increasing the plasma thiol concentration due to its cysteine residues. Albumin is a regulator of intervascular oncotic pressure, serves as an anti-inflammatory modulator, and it has a buffering role due to its histidine imidazole residues. Because of its unique biological and physical properties, albumin has also emerged as a suitable biomaterial for coating implantable devices, for cell and drug delivery, and as a scaffold for tissue engineering and regenerative medicine. As a biomaterial, albumin can be used as surface-modifying film or processed either as cross-linked protein gels or as electrospun fibers. Herein we have discussed how albumin protein can be utilized in regenerative medicine as a hydrogel and as a fibrous mat for a diverse role in successfully delivering drugs, genes, and cells to targeted tissues and organs. The review of prior studies indicated that albumin is a tunable biomaterial from which different types of scaffolds with mechanical properties adjustable for various biomedical applications can be fabricated. Based on the progress made to date, we concluded that albumin-based device coatings, delivery of drugs, genes, and cells are promising strategies in regenerative and personalized medicine.