Natural Polymeric Scaffolds in Bone Regeneration

Biomimetic Graphene/Spongin Scaffolds for Improved Osteoblasts Bioactivity via Dynamic Mechanical Stimulation

Biomimetics offers excellent prospects for design a novel generation of improved biomaterials. Here the controlled integration of graphene oxide (GO) derivatives with a 3D marine spongin (MS) network is explored to nanoengineer novel smart bio-based constructs for bone tissue engineering. The results point out that 3D MS surfaces can be homogeneously coated by layer-by-layer (LbL) assembly of oppositely charged polyethyleneimine (PEI) and GO. Notably, the GOPEI@MS bionanocomposites present a high structural and mechanical stability under compression tests in wet conditions (shape memory). Dynamic mechanically (2 h of sinusoidal compression cyclic interval (0.5 Hz, 0-10% strain)/14 d) stimulates GOPEI@MS seeded with osteoblast (MC3T3-E1), shows a significant improvement in bioactivity, with cell proliferation being two times higher than under static conditions. Besides, the dynamic assays show that GOPEI@MS bionanocomposites are able to act as mechanical stimulus-responsive scaffolds able to resemble physiological bone extracellular matrix (ECM) requirements by strongly triggering mineralization of the bone matrix. These results prove that the environment created by the system cell-GOPEI@MS is suitable for controlling the mechanisms regulating mechanical stimulation-induced cell proliferation for potential in vivo experimentation.

Oral wound healing models and emerging regenerative therapies

Following injury, the oral mucosa undergoes complex sequences of biological healing processes to restore homeostasis. While general similarities exist, there are marked differences in the genomics and kinetics of wound healing between the oral cavity and cutaneous epithelium. The lack of successful therapy for oral mucosal wounds has influenced clinicians to explore alternative treatments and potential autotherapies to enhance intraoral healing. The present in-depth review discusses current gold standards for oral mucosal wound healing and compares endogenous factors that dictate the quality of tissue remodeling. We conducted a review of the literature on in vivo oral wound healing models and emerging regenerative therapies published during the past twenty years. Studies were evaluated by injury models, therapy interventions, and outcome measures. The success of therapeutic approaches was assessed, and research outcomes were compared based on current hallmarks of oral wound healing. By leveraging therapeutic advancements, particularly within in cell-based biomaterials and immunoregulation, there is great potential for translational therapy in oral tissue regeneration.

Natural Polymers for the Maintenance of Oral Health: Review of Recent Advances and Perspectives

The success of modern dental treatment is strongly dependent on the materials used both temporarily and permanently. Among all dental materials, polymers are a very important class with a wide spectrum of applications. This review aims to provide a state-of-the-art overview of the recent advances in the field of natural polymers used to maintain or restore oral health. It focuses on the properties of the most common proteins and polysaccharides of natural origin in terms of meeting the specific biological requirements in the increasingly demanding field of modern dentistry. The use of naturally derived polymers in different dental specialties for preventive and therapeutic purposes has been discussed. The major fields of application cover caries and the management of periodontal diseases, the fabrication of membranes and scaffolds for the regeneration of dental structures, the manufacturing of oral appliances and dentures as well as providing systems for oral drug delivery. This paper also includes a comparative characteristic of natural and synthetic dental polymers. Finally, the current review highlights new perspectives, possible future advancements, as well as challenges that may be encountered by researchers in the field of dental applications of polymers of natural origin.

Regenerative Medicine Technologies to Treat Dental, Oral, and Craniofacial Defects

Additive manufacturing (AM) is the automated production of three-dimensional (3D) structures through successive layer-by-layer deposition of materials directed by computer-aided-design (CAD) software. While current clinical procedures that aim to reconstruct hard and soft tissue defects resulting from periodontal disease, congenital or acquired pathology, and maxillofacial trauma often utilize mass-produced biomaterials created for a variety of surgical indications, AM represents a paradigm shift in manufacturing at the individual patient level. Computer-aided systems employ algorithms to design customized, image-based scaffolds with high external shape complexity and spatial patterning of internal architecture guided by topology optimization. 3D bioprinting and surface modification techniques further enhance scaffold functionalization and osteogenic potential through the incorporation of viable cells, bioactive molecules, biomimetic materials and vectors for transgene expression within the layered architecture. These computational design features enable fabrication of tissue engineering constructs with highly tailored mechanical, structural, and biochemical properties for bone. This review examines key properties of scaffold design, bioresorbable bone scaffolds produced by AM processes, and clinical applications of these regenerative technologies. AM is transforming the field of personalized dental medicine and has great potential to improve regenerative outcomes in patient care.

Milestones and current achievements in development of multifunctional bioscaffolds for medical application

Tissue engineering (TE) is a rapidly growing interdisciplinary field, which aims to restore or improve lost tissue function. Despite that TE was introduced more than 20 years ago, innovative and more sophisticated trends and technologies point to new challenges and development. Current challenges involve the demand for multifunctional bioscaffolds which can stimulate tissue regrowth by biochemical curves, biomimetic patterns, active agents and proper cell types. For those purposes especially promising are carefully chosen primary cells or stem cells due to its high proliferative and differentiation potential. This review summarized a variety of recently reported advanced bioscaffolds which present new functions by combining polymers, nanomaterials, bioactive agents and cells depending on its desired application. In particular necessity of study biomaterial-cell interactions with in vitro cell culture models, and studies using animals with in vivo systems were discuss to permit the analysis of full material biocompatibility. Although these bioscaffolds have shown a significant therapeutic effect in nervous, cardiovascular and muscle, tissue engineering, there are still many remaining unsolved challenges for scaffolds improvement.

Nature-Inspired Unconventional Approaches to Develop 3D Bioceramic Scaffolds with Enhanced Regenerative Ability

Material science is a relevant discipline in support of regenerative medicine. Indeed, tissue regeneration requires the use of scaffolds able to guide and sustain the natural cell metabolism towards tissue regrowth. This need is particularly important in musculoskeletal regeneration, such as in the case of diseased bone or osteocartilaginous regions for which calcium phosphate-based scaffolds are considered as the golden solution. However, various technological barriers related to conventional ceramic processing have thus far hampered the achievement of biomimetic and bioactive scaffolds as effective solutions for still unmet clinical needs in orthopaedics. Driven by such highly impacting socioeconomic needs, new nature-inspired approaches promise to make a technological leap forward in the development of advanced biomaterials. The present review illustrates ion-doped apatites as biomimetic materials whose bioactivity resides in their unstable chemical composition and nanocrystallinity, both of which are, however, destroyed by the classical sintering treatment. In the following, recent nature-inspired methods preventing the use of high-temperature treatments, based on (i) chemically hardening bioceramics, (ii) biomineralisation process, and (iii) biomorphic transformations, are illustrated. These methods can generate products with advanced biofunctional properties, particularly biomorphic transformations represent an emerging approach that could pave the way to a technological leap forward in medicine and also in various other application fields.

Idealization through interactive modeling and experimental assessment of 3D-printed gyroid for trabecular bone scaffold

Porous scaffolds assisted bone tissue engineering is a viable alternative for reconstruction of large segmental bone defects caused by bone pathologies or trauma. In the current study, we intend to develop trabecular bone scaffolds using gyroid architecture. An interactive modeling framework is developed for the design of three-dimensional gyroid scaffolds using advanced generative tools including K3DSurf, MeshLab, and Netfabb. The suggested modeling approach resulted in uniform and interconnected pores. Subsequently, fused deposition modeling 3D-printing is employed to fabricate the scaffolds using poly lactic acid material. The pores interconnectivity, porosity, and surface finish of the fabricated scaffolds are characterized using micro-computer tomography and scanning electron microscopy. Additionally, to assess the performance of scaffolds as a bone substitute, compression, and in-vitro biocompatibility tests on sterilized scaffolds are conducted. Compression tests reveal mechanical strength in the range of native bone while human adipose-derived mesenchymal stem cells show high proliferation after 72 h of incubation. Based on these results, the fabricated gyroid scaffolds can be said to possess favorable properties for trabecular bone scaffold.

Collagen-based biomaterials for biomedical applications

Collagen is an insoluble fibrous protein that composes the extracellular matrix in animals. Although collagen has been used as a biomaterial since 1881, the properties and the complex structure of collagen are still extensive study subjects worldwide. In this article, several topics of importance for understanding collagen research are reviewed starting from its historical milestones, followed by the description of the collagen superfamily and its complex structures, with a focus on type I collagen. Subsequently, some of the superior properties of collagen-based biomaterials, such as biocompatibility, biodegradability, mechanical properties, and cell activities, are pinpointed. These properties make collagen applicable in biomedicine, such as wound healing, tissue engineering, surface coating of medical devices, and skin supplementation. Moreover, some antimicrobial strategies and the general host tissue responses regarding collagen as a biomaterial are presented. Finally, the current status and clinical application of the three-dimensional (3D) printing techniques for the fabrication of collagen-based scaffolds and the reconstruction of the human heart's constituents, such as capillary structures or even the entire organ, are discussed. Besides, an overall outlook for the future of this unique biomaterial is provided.

Cathelicidin LL37 Promotes Osteogenic Differentiation in vitro and Bone Regeneration in vivo

Different types of biomaterials have been used to repair the defect of bony orbit. However, exposure and infections are still critical risks in clinical application. Biomaterials with characteristics of osteogenesis and antibiosis are needed for bone regeneration. In this study, we aimed to characterize the antimicrobial effects of cathelicidin-LL37 and to assess any impacts on osteogenic activity. Furthermore, we attempted to demonstrate the feasibility of LL37 as a potential strategy in the reconstruction of clinical bone defects. Human adipose-derived mesenchyme stem cells (hADSCs) were cultured with different concentrations of LL37 and the optimum concentration for osteogenesis was selected for further in vitro studies. We then evaluated the antibiotic properties of LL37 at the optimum osteogenic concentration. Finally, we estimated the efficiency of a PSeD/hADSCs/LL37 combined scaffold on reconstructing bone defects in the rat calvarial defect model. The osteogenic ability on hADSCs in vitro was shown to be dependent on the concentration of LL37 and reached a peak at 4 μg/ml. The optimum concentration of LL37 showed good antimicrobial properties against Escherichia coli and Staphylococcus anurans. The combination scaffold of PSeD/hADSCs/LL37 showed superior osteogenic properties compared to the PSeD/hADSCs, PSeD, and control groups scaffolds, indicating a strong bone reconstruction effect in the rat calvarial bone defect model. In Conclusion, LL37 was shown to promote osteogenic differentiation in vitro as well as antibacterial properties. The combination of PSeD/hADSCs/LL37 was advantageous in the rat calvarial defect reconstruction model, showing high potential in clinical bone regeneration.

Mimicking the Hierarchical Organization of Natural Collagen: Toward the Development of Ideal Scaffolding Material for Tissue Regeneration

Biological materials found in living organisms, many of which are proteins, feature a complex hierarchical organization. Type I collagen, a fibrous structural protein ubiquitous in the mammalian body, provides a striking example of such a hierarchical material, with peculiar architectural features ranging from the amino acid sequence at the nanoscale (primary structure) up to the assembly of fibrils (quaternary structure) and fibers, with lengths of the order of microns. Collagen plays a dominant role in maintaining the biological and structural integrity of various tissues and organs, such as bone, skin, tendons, blood vessels, and cartilage. Thus, "artificial" collagen-based fibrous assemblies, endowed with appropriate structural properties, represent ideal substrates for the development of devices for tissue engineering applications. In recent years, with the ultimate goal of developing three-dimensional scaffolds with optimal bioactivity able to promote both regeneration and functional recovery of a damaged tissue, numerous studies focused on the capability to finely modulate the scaffold architecture at the microscale and the nanoscale in order to closely mimic the hierarchical features of the extracellular matrix and, in particular, the natural patterning of collagen. All of these studies clearly show that the accurate characterization of the collagen structure at the submolecular and supramolecular levels is pivotal to the understanding of the relationships between the nanostructural/microstructural properties of the fabricated scaffold and its macroscopic performance. Several studies also demonstrate that the selected processing, including any crosslinking and/or sterilization treatments, can strongly affect the architecture of collagen at various length scales. The aim of this review is to highlight the most recent findings on the development of collagen-based scaffolds with optimized properties for tissue engineering. The optimization of the scaffolds is particularly related to the modulation of the collagen architecture, which, in turn, impacts on the achieved bioactivity.

Multiscale porosity in a 3D printed gellan-gelatin composite for bone tissue engineering

The aim of this work was to develop a complex-shaped gelatin-gellan composite scaffold with multiscale porosity using a combination of cryogenic 3D printing and lyophilization for bone tissue engineering. Cryogenic 3D printing was used to fabricate a low-concentration composite of complex-shaped macroporous gelatin-gellan structures with a pore size of 919 ± 89 µm. This was followed by lyophilization to introduce micropores of size 20-250 µm and nanometre-level surface functionalities, thus achieving a hierarchical porous structure. These multiscale porous scaffolds (GMu) were compared with two other types of scaffolds having only microporosity (GMi) and macroporosity (GMa) with regard to their physical andin vitrobiological properties. GMu scaffolds were found to be better than GMi and GMa in terms of swelling percentage, degradation rate, uniform pore distribution, cellular infiltration, attachment, proliferation, protein generation and mineralization. In conclusion, we have developed a controlled hierarchical bone-like structure, biomimicking natural bone, together with a reproducible process of manufacture by coupling soft hydrogel 3D printing with lyophilization. This enables the development of complex-shaped patient-specific 3D printed hydrogel scaffolds with enhanced performancein vitroand great potential in the fields of tissue engineering, bioprinting and regenerative medicine.

The Drug-Loaded Electrospun Poly(ε-Caprolactone) Mats for Therapeutic Application

Diclofenac sodium salt (DSS)-loaded electrospun nanofiber mats on the base of poly(ε-caprolactone) (PCL) were investigated as biocompatible nanofibrous mats for medical applications with the ability to inhibit bacterial infections. The paper presents the characteristics of fibrous mats made by electrospinning and determines the effect of medicament on the fiber morphology, chemical, mechanical and thermal properties, as well as wettability. PCL and DSS-loaded PCL nanofibrous mats were characterized using scanning electron microscopy, transmission electron microscopy, attenuated total reflectance-Fourier transform infrared spectrometry, dynamic mechanical analysis, and contact angle measurements. Electron paramagnetic resonance measurements confirmed the lifetime of DSS before and after application of high voltage during the electrospinning process. In vitro biocompatibility was studied, and it was proved to be of good viability with ~92% of the diploid human cells culture line composed of lung fibroblast (MRC 5) after 48 h of incubation. Moreover, the significant activity of DSS-loaded nanofibers against cancer cells, Ca Ski and HeLa, was established as well. It was shown that 12.5% (m/V) is the minimal concentration for antibacterial activity when more than 99% of Escherichia coli (Gram-negative) and 99% of Staphylococcus aureus (Gram-positive) have been exterminated.

Marine Algae Incorporated Polylactide Acid Patch: Novel Candidate for Targeting Osteosarcoma Cells without Impairing the Osteoblastic Proliferation

Biodegradable collagen-based materials have been preferred as scaffolds and grafts for diverse clinical applications in density and orthopedy. Besides the advantages of using such bio-originated materials, the use of collagen matrices increases the risk of infection transmission through the cells or the tissues of the graft/scaffold. In addition, such collagen-based solutions are not counted as economically feasible approaches due to their high production cost. In recent years, incorporation of marine algae in synthetic polymers has been considered as an alternative method for preparation grafts/scaffolds since they represent abundant and cheap source of potential biopolymers. Current work aims to propose a novel composite patch prepared by blending Sargassum vulgare powders (SVP) to polylactide (PLA) as an alternative to the porcine-derived membranes. SVP-PLA composite patches were produced by using a modified solvent casting method. Following detailed material characterization to assess the cytocompatibility, human osteoblasts (HOBs) and osteosarcoma cells (SaOS-2) were seeded on neat PLA and SVP-PLA patches. MTT and BrdU assays indicated a greater cytocompatibility and higher proliferation for HOBs cultured on SVP-PLA composite than for those cultured on neat PLA. SaOS-2 cells cultured on SVP-PLA exhibited a significant decrease in cell proliferation. The composite patch described herein exhibits an antiproliferative effect against SaOS-2 cells without impairing HOBs' adhesion and proliferation.

Enhanced Cells Anchoring to Electrospun Hybrid Scaffolds With PHBV and HA Particles for Bone Tissue Regeneration

Hybrid materials combining organic and inorganic compounds used as scaffolds are highly beneficial in bone regeneration. In this study, we successfully produced by blend electrospinning poly(3-hydroxybutyric acid-co-3-hydrovaleric acid) (PHBV) scaffolds enriched with hydroxyapatite (HA) particles to biomimic bone tissue for improved and faster regeneration processes. The morphology, fiber diameters, and composition of the scaffolds were investigated by scanning electron microscopy (SEM) techniques followed by focused ion beam (FIB) sectioning to verify HA particles integration with PHBV fibers. In vitro cell culture was performed for 7 days and followed with the cell proliferation test (CellTiter-Blue^® Assay). Additionally, cell integration with the scaffold was visualized by confocal and SEM imaging. We developed a simple way of obtaining hybrid scaffolds by electrospinning PHBV solution with HA particles without any post-processing. The PHBV + HA scaffold enhanced cell proliferation and filopodia formation responsible for cell anchoring within the created 3D environment. The obtained results show the great potential in the development of hybrid scaffolds stimulating bone tissue regeneration.

Initiated Chemical Vapor Deposition (iCVD) Functionalized Polylactic Acid-Marine Algae Composite Patch for Bone Tissue Engineering

The current study aimed to describe the fabrication of a composite patch by incorporating marine algae powders (MAPs) into poly-lactic acid (PLA) for bone tissue engineering. The prepared composite patch was functionalized with the co-polymer, poly (2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) (p(HEMA-co-EGDMA)) via initiated chemical vapor deposition (iCVD) to improve its wettability and overall biocompatibility. The iCVD functionalized MAP–PLA composite patch showed superior cell interaction of human osteoblasts. Following the surface functionalization by p(HEMA-co-EGDMA) via the iCVD technique, a highly hydrophilic patch was achieved without tailoring any morphological and structural properties. Moreover, the iCVD modified composite patch exhibited ideal cell adhesion for human osteoblasts, thus making the proposed patch suitable for potential biomedical applications including bone tissue engineering, especially in the fields of dentistry and orthopedy.

Clinical Application of Bone Marrow Mesenchymal Stem/Stromal Cells to Repair Skeletal Tissue

There has been an escalation in reports over the last decade examining the efficacy of bone marrow derived mesenchymal stem/stromal cells (BMSC) in bone tissue engineering and regenerative medicine-based applications. The multipotent differentiation potential, myelosupportive capacity, anti-inflammatory and immune-modulatory properties of BMSC underpins their versatile nature as therapeutic agents. This review addresses the current limitations and challenges of exogenous autologous and allogeneic BMSC based regenerative skeletal therapies in combination with bioactive molecules, cellular derivatives, genetic manipulation, biocompatible hydrogels, solid and composite scaffolds. The review highlights the current approaches and recent developments in utilizing endogenous BMSC activation or exogenous BMSC for the repair of long bone and vertebrae fractures due to osteoporosis or trauma. Current advances employing BMSC based therapies for bone regeneration of craniofacial defects is also discussed. Moreover, this review discusses the latest developments utilizing BMSC therapies in the preclinical and clinical settings, including the treatment of bone related diseases such as Osteogenesis Imperfecta.

Progress and Prospects of Polymer-Based Drug Delivery Systems for Bone Tissue Regeneration

Despite the high regenerative capacity of bone tissue, there are some cases where bone repair is insufficient for a complete functional and structural recovery after damage. Current surgical techniques utilize natural and synthetic bone grafts for bone healing, as well as collagen sponges loaded with drugs. However, there are certain disadvantages associated with these techniques in clinical usage. To improve the therapeutic efficacy of bone tissue regeneration, a number of drug delivery systems based on biodegradable natural and synthetic polymers were developed and examined in in vitro and in vivo studies. Recent studies have demonstrated that biodegradable polymers play a key role in the development of innovative drug delivery systems and tissue engineered constructs, which improve the treatment and regeneration of damaged bone tissue. In this review, we discuss the most recent advances in the field of polymer-based drug delivery systems for the promotion of bone tissue regeneration and the physical-chemical modifications of polymers for controlled and sustained release of one or more drugs. In addition, special attention is given to recent developments on polymer nano- and microparticle-based drug delivery systems for bone regeneration.

Paramagnetic Functionalization of Biocompatible Scaffolds for Biomedical Applications: A Perspective

The burst of research papers focused on the tissue engineering and regeneration recorded in the last years is justified by the increased skills in the synthesis of nanostructures able to confer peculiar biological and mechanical features to the matrix where they are dispersed. Inorganic, organic and hybrid nanostructures are proposed in the literature depending on the characteristic that has to be tuned and on the effect that has to be induced. In the field of the inorganic nanoparticles used for decorating the bio-scaffolds, the most recent contributions about the paramagnetic and superparamagnetic nanoparticles use was evaluated in the present contribution. The intrinsic properties of the paramagnetic nanoparticles, the possibility to be triggered by the simple application of an external magnetic field, their biocompatibility and the easiness of the synthetic procedures for obtaining them proposed these nanostructures as ideal candidates for positively enhancing the tissue regeneration. Herein, we divided the discussion into two macro-topics: the use of magnetic nanoparticles in scaffolds used for hard tissue engineering for soft tissue regeneration.

Highly Permeable Gelatin/Poly(lactic acid) Fibrous Scaffolds with a Three-Dimensional Spatial Structure for Efficient Cell Infiltration, Mineralization and Bone Regeneration

Three-dimensional (3D) fibrous scaffolds allowing sufficient cell infiltration are urgently needed for bone tissue engineering. In this study, a highly permeable 3D interconnected scaffold was fabricated by surface bonding of cotton-like nonwoven fibers with micro- and nanoscale architecture using gaseous chloroform. The results of physiochemical characterization indicated that bonding for 90 min with a fiber density of 0.15 g/cm³ could facilitate satisfactory porosity, supportive mechanical properties, and a 3D spatial microstructure for cell ingrowth. Coating with gelatin on the fibers induced highly efficient in vitro mineralization and in vivo bone formation as indicated by mineral deposition and repair of rabbit radius bone defect. The findings from this work demonstrated that these biofunctionalized fibrous scaffolds could bionically represent topographic nanofeatures and biological composition for cell binding affinities similar to those of the natural extracellular matrix (ECM). It can be concluded that the facile fabrication and modification strategy of 3D fibrous scaffolds exhibit promising prospect to fulfill the progressive needs in bone tissue engineering.

Innovative Molecular and Cellular Therapeutics in Cleft Palate Tissue Engineering

Clefts of the lip and/or palate are the most prevalent orofacial birth defects occurring in about 1:700 live human births worldwide. Early postnatal surgical interventions are extensive and staged to bring about optimal growth and fusion of palatal shelves. Severe cleft defects pose a challenge to correct with surgery alone, resulting in complications and sequelae requiring life-long, multidisciplinary care. Advances made in materials science innovation, including scaffold-based delivery systems for precision tissue engineering, now offer new avenues for stimulating bone formation at the site of surgical correction for palatal clefts. In this study, we review the present scientific literature on key developmental events that can go awry in palate development and the common surgical practices and challenges faced in correcting cleft defects. How key osteoinductive pathways implicated in palatogenesis inform the design and optimization of constructs for cleft palate correction is discussed within the context of translation to humans. Finally, we highlight new osteogenic agents and innovative delivery systems with the potential to be adopted in engineering-based therapeutic approaches for the correction of palatal defects. Impact statement Tissue-engineered scaffolds supplemented with osteogenic growth factors have attractive, largely unexplored possibilities to modulate molecular signaling networks relevant to driving palatogenesis in the context of congenital anomalies (e.g., cleft palate). Constructs that address this need may obviate current use of autologous bone grafts, thereby avoiding donor-site morbidity and other regenerative challenges in patients afflicted with palatal clefts. Combinations of biomaterials and drug delivery of diverse regenerative cues and biologics are currently transforming strategies exploited by engineers, scientists, and clinicians for palatal cleft repair.

Innovative Human Three-Dimensional Tissue-Engineered Models as an Alternative to Animal Testing

Animal testing has long been used in science to study complex biological phenomena that cannot be investigated using two-dimensional cell cultures in plastic dishes. With time, it appeared that more differences could exist between animal models and even more when translated to human patients. Innovative models became essential to develop more accurate knowledge. Tissue engineering provides some of those models, but it mostly relies on the use of prefabricated scaffolds on which cells are seeded. The self-assembly protocol has recently produced organ-specific human-derived three-dimensional models without the need for exogenous material. This strategy will help to achieve the 3R principles.