Biocomposites reinforced by fibers or tubes as scaffolds for tissue engineering or regenerative medicine

Review of recent advances in bone scaffold fabrication methods for tissue engineering for treating bone diseases and sport injuries

Despite advancements in medical care, the management of bone injuries remains one of the most significant challenges in the fields of medicine and sports medicine globally. Bone tissue damage is often associated with aging, reduced quality of life, and various conditions such as trauma, cancer, and infection. While bone tissue possesses the natural capacity for self-repair and regeneration, severe damage may render conventional treatments ineffective, and bone grafting may be limited due to secondary surgical procedures and potential disease transmission. In such cases, bone tissue engineering has emerged as a viable approach, utilizing cells, scaffolds, and growth factors to repair damaged bone tissue. This research shows a comprehensive review of the current literature on the most important and effective methods and materials for improving the treatment of these injuries. Commonly employed cell types include osteogenic cells, embryonic stem cells, and mesenchymal cells, while scaffolds play a crucial role in bone tissue regeneration. To create an effective bone scaffold, a thorough understanding of bone structure, material selection, and examination of scaffold fabrication techniques from inception to the present day is necessary. By gaining insights into these three key components, the ability to design and construct appropriate bone scaffolds can be achieved. Bone tissue engineering scaffolds are evaluated based on factors such as strength, porosity, cell adhesion, biocompatibility, and biodegradability. This article examines the diverse categories of bone scaffolds, the materials and techniques used in their fabrication, as well as the associated merits and drawbacks of these approaches. Furthermore, the review explores the utilization of various scaffold types in bone tissue engineering applications.

A Method for Sensing Dielectric Properties of Thin and Flexible Conductive Biocomposites

This study investigates the dielectric properties of conductive biocomposites (CBs), which are integral to the development of advanced materials for flexible electronics and medical devices. A novel method employing Microwave Reflectometry (MR) is introduced, utilizing a miniaturized Vector Network Analyzer (m-VNA) and a dedicated sensing element (SE), to extract the dielectric properties of CBs. The method is grounded in a minimization principle, aligning the measured S11 reflection scattering parameter with its electromagnetic (EM) simulation, facilitating a refined process for determining the dielectric properties. The experimental setup was meticulously engineered, optimized, and validated using reference dielectric samples (RDSs) with known dielectric properties. The method was then applied to three innovative CBs, resulting in an accurate extrapolation of their dielectric properties. The findings highlight the method's versatility, cost-efficiency, and applicability to ultra-thin and flexible biopolymer films, offering significant potential for advancements in flexible electronics and bio-sensing applications.

Drug eluting protein and polysaccharides-based biofunctionalized fabric textiles- pioneering a new frontier in tissue engineering: An extensive review

In the ever-evolving landscape of tissue engineering, medicated biotextiles have emerged as a game-changer. These remarkable textiles have garnered significant attention for their ability to craft tissue scaffolds that closely mimic the properties of natural tissues. This comprehensive review delves into the realm of medicated protein and polysaccharide-based biotextiles, exploring a diverse array of fabric materials. We unravel the intricate web of fabrication methods, ranging from weft/warp knitting to plain/stain weaving and braiding, each lending its unique touch to the world of biotextiles creation. Fibre production techniques, such as melt spinning, wet/gel spinning, and multicomponent spinning, are demystified to shed light on the magic behind these ground-breaking textiles. The biotextiles thus crafted exhibit exceptional physical and chemical properties that hold immense promise in the field of tissue engineering (TE). Our review underscores the myriad applications of drug-eluting protein and polysaccharide-based textiles, including TE, tissue repair, regeneration, and wound healing. Additionally, we delve into commercially available products that harness the potential of medicated biotextiles, paving the way for a brighter future in healthcare and regenerative medicine. Step into the world of innovation with medicated biotextiles-where science meets the art of healing.

Novel PLCL nanofibrous/keratin hydrogel bilayer wound dressing for skin wound repair

In this study, a novel poly(L-lactate-caprolactone) copolymer (PLCL) nanofibrous/keratin hydrogel bilayer wound dressing loaded with fibroblast growth factor (FGF-2) was prepared by the low-pressure filtration-assisted method. The ability of the keratin hydrogel in the bilayer dressing to mimic the dermis and that of the nanofibrous PLCL to mimic the epidermis were discussed. Keratin hydrogel exhibited good porosity and maximum water absorption of 874.09%. Compared with that of the dressing prepared by the coating method, the interface of the bilayer dressing manufactured by the low-pressure filtration-assisted method (filtration time: 20 min) was tightly bonded, and its bilayer dressing interface could not be easily peeled off. The elastic modulus of hydrogel was about 44 kPa, which was similar to the elastic modulus of the dermis (2-80 kPa). Additionally, PLCL nanofibers had certain toughness and flexibility suitable for simulating the epidermal structures. In vitro studies showed that the bilayer dressing was biocompatible and biodegradable. In vivo studies indicated that PLCL/keratin-FGF-2 bilayer dressing could promote re-epithelialization, collagen deposition, skin appendages (hair follicles) regeneration, microangiogenesis construction, and adipose-derived stem cells (ADSCs) recruitment. The introduction of FGF-2 resulted in a better repair effect. The bilayer dressing also solved the problems of poor interface adhesion of hydrogel/electrospinning nanofibers. This paper also explored the preliminary role and mechanism of bilayer dressing in promoting skin healing, showing that its potential applications as a biomedical wound dressing in the field of skin tissue engineering.

Poly(ε-Caprolactone) Substrates with Micro/Nanohierarchical Patterned Structures for Cell Culture

A simple, efficient and controllable one-step template method is proposed to fabricate poly(ε-caprolactone) substrates with micro/nanohierarchical patterned structures. Two kinds of geometric patterns with and without nanowires, i.e., hexagonal and strip with controllable island size and spacing are designed and fabricated. Furthermore, the influence of geometric patterns, island size, island spacing, and patterned nanowires (pNW) on the growth behavior of MG-63 cells is studied in terms of cell density, distribution, proliferation, morphogenesis, and cellular alignment. It is found that MG-63 cells prefer to adhere and grow on the substrate with smaller island size or spacing. Moreover, unlike the hexagonal structure, the strip structure can guide cellular alignment on its surface. In addition, the microisland structures and the pNW play different roles in promoting cell proliferation, distribution, and morphogenesis. It is concluded that the growth behavior of MG-63 cells can be well controlled by precisely adjusting the micro/nanostructure of the substrate surface. A simple and effective method is provided here for the regulation of cell growth behavior.

Green Polymer Nanocomposites for Skin Tissue Engineering

Fabrication of an appropriate skin scaffold needs to meet several standards related to the mechanical and biological properties. Fully natural/green scaffolds with acceptable biodegradability, biocompatibility, and physiological properties quite often suffer from poor mechanical properties. Therefore, for appropriate skin tissue engineering and to mimic the real functions, we need to use synthetic polymers and/or additives as complements to green polymers. Green nanocomposites (either nanoscale natural macromolecules or biopolymers containing nanoparticles) are a class of scaffolds with acceptable biomedical properties window (drug delivery and cardiac, nerve, bone, cartilage as well as skin tissue engineering), enabling one to achieve the required level of skin regeneration and wound healing. In this review, we have collected, summarized, screened, analyzed, and interpreted the properties of green nanocomposites used in skin tissue engineering and wound dressing. We particularly emphasize the mechanical and biological properties that skin cells need to meet when seeded on the scaffold. In this regard, the latest state of the art studies directed at fabrication of skin tissue and bionanocomposites as well as their mechanistic features are discussed, whereas some unspoken complexities and challenges for future developments are highlighted.

Design-Build-Validate Strategy to 3D Print Bioglass Gradients for Anterior Cruciate Ligament Enthesis Reconstruction

A rupture of the anterior cruciate ligament (ACL) is one of the most common knee ligament injuries affecting the young and active population. Tissue engineering strategies to reconstruct the damaged ACL have met with significant challenges mainly associated with poor graft integration at the bone-ligament interface (i.e., enthesis). In this study, a "design-build-validate" strategy was employed by combining 3D Raman spectral mapping and 3D printing to develop a tissue engineered scaffold that is compositionally similar to the ACL bone-ligament interface and can provide the essential biochemical cues to promote interface regeneration and facilitate functional graft to bone integration. Results showed that Raman spectroscopy is a highly efficient nondestructive technique to determine the biochemical composition of native ACL enthesis. 3D printing using combinatory inks consisting of different compositions of methacrylated collagen (CMA) and Bioglass (BG) allowed for the fabrication of BG gradient-incorporated collagen matrices (BioGIMs) with a transition region confirmed by Alizarin red S staining. Furthermore, Raman spectroscopy validated replication of ACL enthesis composition in BioGIMs. In addition, human mesenchymal stem cells (hMSCs) cultured on BioGIMs showed morphological differences along the length of the BioGIMs as evidenced by confocal microscopy of cell cytoskeleton-stained images indicating that the cells can sense the underlying differences in matrix composition. Overall, the "design-build-validate" strategy developed in this study has significant potential to generate biomimetic tissue constructs for use at the interface regions of synthetic grafts to promote better host integration and achieve full reconstruction of the ACL. Impact statement Poor graft integration at the bone-ligament interface (i.e., enthesis) is a significant clinical problem in anterior cruciate ligament (ACL) repair and reconstruction. In this study, Raman spectroscopy and 3D printing technologies were used in combination for the first time in a design-build-validate strategy to develop a continuous biomimetic Bioglass gradient-incorporated collagen matrix (BioGIM) that compositionally emulates the native ACL enthesis. These BioGIMs can be fused onto the ends of synthetic ACL grafts and have significant potential to provide the essential biochemical cues to guide tissue-specific cell differentiation, augment functional matrix reorganization, promote better graft integration, and achieve full reconstruction of damaged ACL.

Hydrogel Composites with Different Dimensional Nanoparticles for Bone Regeneration

The treatment of large segmental bone defects and complex types of fractures caused by trauma, inflammation, or tumor resection is still a challenge in the field of orthopedics. Various natural or synthetic biological materials used in clinical applications cannot fully replicate the structure and performance of raw bone. This highlights how to endow materials with multiple functions and biological properties, which is a problem that needs to be solved in practical applications. Hydrogels with outstanding biocompatibility, for their casting into any shape, size, or form, are suitable for different forms of bone defects. Therefore, they have been used in regenerative medicine more widely. In this review, versatile hydrogels are compounded with nanoparticles of different dimensions, and many desirable features of these materials in bone regeneration are introduced, including drug delivery, cell factor vehicle, cell scaffolds, which have potential in bone regeneration applications. The combination of hydrogels and nanoparticles of different dimensions encourages better filling of bone defect areas and has higher adaptability. This is due to the minimally invasive properties of the material and ability to match irregular defects. These biological characteristics make composite hydrogels with different dimensional nanoparticles become one of the most attractive options for bone regeneration materials.

The effect of carbon nanotubes on osteogenic functions of adipose-derived mesenchymal stem cells in vitro and bone formation in vivo compared with that of nano-hydroxyapatite and the possible mechanism

It has been well recognized that the development and use of artificial materials with high osteogenic ability is one of the most promising means to replace bone grafting that has exhibited various negative effects. The biomimetic features and unique physiochemical properties of nanomaterials play important roles in stimulating cellular functions and guiding tissue regeneration. But efficacy degree of some nanomaterials to promote specific tissue formation is still not clear. We hereby comparatively studied the osteogenic ability of our treated multi-walled carbon nanotubes (MCNTs) and the main inorganic mineral component of natural bone, nano-hydroxyapatite (nHA) in the same system, and tried to tell the related mechanism. In vitro culture of human adipose-derived mesenchymal stem cells (HASCs) on the MCNTs and nHA demonstrated that although there was no significant difference in the cell adhesion amount between on the MCNTs and nHA, the cell attachment strength and proliferation on the MCNTs were better. Most importantly, the MCNTs could induce osteogenic differentiation of the HASCs better than the nHA, the possible mechanism of which was found to be that the MCNTs could activate Notch involved signaling pathways by concentrating more proteins, including specific bone-inducing ones. Moreover, the MCNTs could induce ectopic bone formation in vivo while the nHA could not, which might be because MCNTs could stimulate inducible cells in tissues to form inductive bone better than nHA by concentrating more proteins including specific bone-inducing ones secreted from M2 macrophages. Therefore, MCNTs might be more effective materials for accelerating bone formation even than nHA.

Electrospun Nanofibers of Natural and Synthetic Polymers as Artificial Extracellular Matrix for Tissue Engineering

Many types of polymer nanofibers have been introduced as artificial extracellular matrices. Their controllable properties, such as wettability, surface charge, transparency, elasticity, porosity and surface to volume proportion, have attracted much attention. Moreover, functionalizing polymers with other bioactive components could enable the engineering of microenvironments to host cells for regenerative medical applications. In the current brief review, we focus on the most recently cited electrospun nanofibrous polymeric scaffolds and divide them into five main categories: natural polymer-natural polymer composite, natural polymer-synthetic polymer composite, synthetic polymer-synthetic polymer composite, crosslinked polymers and reinforced polymers with inorganic materials. Then, we focus on their physiochemical, biological and mechanical features and discussed the capability and efficiency of the nanofibrous scaffolds to function as the extracellular matrix to support cellular function.

Frame Coating of Single-Walled Carbon Nanotubes in Collagen on PET Fibers for Artificial Joint Ligaments

The coating formation technique for artificial knee ligaments was proposed, which provided tight fixation of ligaments of polyethylene terephthalate (PET) fibers as a result of the healing of the bone channel in the short-term period after implantation. The coating is a frame structure of single-walled carbon nanotubes (SWCNT) in a collagen matrix, which is formed by layer-by-layer solidification of an aqueous dispersion of SWCNT with collagen during spin coating and controlled irradiation with IR radiation. Quantum mechanical method SCC DFTB, with a self-consistent charge, was used. It is based on the density functional theory and the tight-binding approximation. The method established the optimal temperature and time for the formation of the equilibrium configurations of the SWCNT/collagen type II complexes to ensure maximum binding energies between the nanotube and the collagen. The highest binding energies were observed in complexes with SWCNT nanometer diameter in comparison with subnanometer SWCNT. The coating had a porous structure-pore size was 0.5-6 μm. The process of reducing the mass and volume of the coating with the initial biodegradation of collagen after contact with blood plasma was demonstrated. This is proved by exceeding the intensity of the SWCNT peaks G and D after contact with the blood serum in the Raman spectrum and by decreasing the intensity of the main collagen bands in the SWCNT/collagen complex frame coating. The number of pores and their size increased to 20 μm. The modification of the PET tape with the SWCNT/collagen coating allowed to increase its hydrophilicity by 1.7 times compared to the original PET fibers and by 1.3 times compared to the collagen coating. A reduced hemolysis level of the PET tape coated with SWCNT/collagen was achieved. The SWCNT/collagen coating provided 2.2 times less hemolysis than an uncoated PET implant. MicroCT showed the effective formation of new bone and dense connective tissue around the implant. A decrease in channel diameter from 2.5 to 1.7 mm was detected at three and, especially, six months after implantation of a PET tape with SWCNT/collagen coating. MicroCT allowed us to identify areas for histological sections, which demonstrated the favorable interaction of the PET tape with the surrounding tissues. In the case of using the PET tape coated with SWCNT/collagen, more active growth of connective tissue with mature collagen fibers in the area of implantation was observed than in the case of only collagen coating. The stimulating effect of SWCNT/collagen on the formation of bone trabeculae around and inside the PET tape was evident in three and six months after implantation. Thus, a PET tape with SWCNT/collagen coating has osteoconductivity as well as a high level of hydrophilicity and hemocompatibility.

Silicate bioceramics: from soft tissue regeneration to tumor therapy

Great efforts have been devoted to exploiting silicate bioceramics for various applications in soft tissue regeneration, owing to their excellent bioactivity. Based on the inherent ability of silicate bioceramics to repair tissue, bioactive ions are easily incorporated into silicate bioceramics to endow them with extra biological properties, such as enhanced angiogenesis, antibiosis, enhanced osteogenesis, and antitumor effect, which significantly expands the application of multifunctional silicate bioceramics. Furthermore, silicate nanobioceramics with unique structures have been widely employed for tumor therapy. In recent years, the novel applications of silicate bioceramics for both tissue regeneration and tumor therapy have substantially grown. Eliminating the skin tumors first and then repairing the skin wounds has been widely investigated by our groups, which might shed some light on treating other soft tissue tumor or tumor-induced defects. This review first describes the recent advances made in the development of silicate bioceramics as therapeutic platforms for soft tissue regeneration. We then highlight the major silicate nanobioceramics used for tumor therapy. Silicate bioceramics for both soft tissue regeneration and tumor therapy are further emphasized. Finally, challenges and future directions of silicate bioceramics stepping into the clinics are discussed. This review will inspire researchers to create the efficient and functional silicate bioceramics needed for regeneration and tumor therapy of other tissues.

Effect of Drilling Techniques on Microcracks and Pull-Out Strength of Cortical Screw Fixed in Human Tibia: An In-Vitro Study

The strength between the cortical screw and bone following an orthopaedic implant surgery is an important determinant for the success of osteosynthesis. An excessive axial cutting force during drilling produces microcracks in the bone surface, resulting in reduced strength between the screw and bone, resulting in loosening of implant. The present work, investigates the influence of drilling parameters on microcracks generated in the drilled surface and pull-out strength of screw fixed in cortical bone of human tibia. The holes were drilled by two different techniques: conventional surgical bone drilling (CSBD) and rotary ultrasonic bone drilling (RUBD), by a recently developed operation theatre (OT) compatible machine. Cutting force generated in drilling of human tibia using RUBD was 30-40% lesser than that of CSBD. Scanning electron microscopy (SEM) also revealed that RUBD produced significantly lesser and thinner microcracks than that of CSBD in human bones. Biomechanical pull-out test results showed that, the pull-out strength of screws inserted into drilled holes by RUBD was much higher (100-150%) than that of CSBD. A significant difference in pull-out strength (p < 0.05) between RUBD and CSBD was revealed by statistical analysis at 95% confidence interval.

Combination of electrospinning with other techniques for the fabrication of 3D polymeric and composite nanofibrous scaffolds with improved cellular interactions

The development of three-dimensional (3D) scaffolds with physical and chemical topological cues at the macro-, micro-, and nanometer scale is urgently needed for successful tissue engineering applications. 3D scaffolds can be manufactured by a wide variety of techniques. Electrospinning technology has emerged as a powerful manufacturing technique to produce non-woven nanofibrous scaffolds with very interesting features for tissue engineering products. However, electrospun scaffolds have some inherent limitations that compromise the regeneration of thick and complex tissues. By integrating electrospinning and other fabrication technologies, multifunctional 3D fibrous assemblies with micro/nanotopographical features can be created. The proper combination of techniques leads to materials with nano and macro-structure, allowing an improvement in the biological performance of tissue-engineered constructs. In this review, we focus on the most relevant strategies to produce electrospun polymer/composite scaffolds with 3D architecture. A detailed description of procedures involving physical and chemical agents to create structures with large pores and 3D fiber assemblies is introduced. Finally, characterization and biological assays including in vitro and in vivo studies of structures intended for the regeneration of functional tissues are briefly presented and discussed.

Soya protein isolate-polyethylene oxide electrospun nanofiber membrane with bone marrow-derived mesenchymal stem cell for enhanced bone regeneration

In this study, we prepared an electrospun nanofiber membrane from soya protein isolate (SPI) and polyethylene oxide (PEO) loaded with rat bone marrow-derived mesenchymal stem cells (rBMSC), as a cell-scaffold approach to enhance bone regeneration. Different ratios of SPI:PEO (7:0, 7:1, 7:3, 7:5, and 0:7) was investigated to obtain uniform nanofibers, and crosslinked with EDC/NHS to stabilize the membranes. SPI/PEO membrane (7:3) was found to create more uniform and stable nanofibers at a flow rate of 9 µL/min, spun in a cylindrical collector rotating at 350 r/min, 23 kV DC voltage, and needle tip to collector distance of 13 cm. The loaded rBMSC were pre-differentiated to ensure commitment towards osteoblastic lineage. The SPI/PEO electrospun nanofiber membranes were successful in allowing for cell attachment and growth of the rBMSC and was further investigated in vivo using a rat skull defect model. New bone formation was observed for the optimized SPI/PEO electrospun nanofiber membrane (7:3) with and without rBMSC, but with faster new bone formation for SPI/PEO electrospun nanofiber membrane loaded with rBMSC as compared to SPI/PEO electrospun nanofiber membrane only and control (defect only).

Photo-Functionalized Magnetic Nanoparticles as a Nanocarrier of Photodynamic Anticancer Agent for Biomedical Theragnostics

Various theragnostic agents have been devised and developed as cancer treatments; however, existing agents are often limited by their specific functions and complexities. Here, we report multifunctional magnetite (Fe₃O₄) nanoparticles functionalized with chlorin e6 (Ce6) and folic acid (FA) using a simple fabrication process to be used as theragnostic agents in photodynamic therapy (PDT). The effectiveness of cellular uptake of Fe3O4-Ce6-FA nanoparticles (FCF NPs) and its visualization as well as the photodynamic anticancer activities were evaluated. The mechanism of cancer cell death by the FCF NPs was also verified with qualitative and quantitative methods. Results indicate that FCF NPs have good penetration efficacy, resulting in excellent in vitro fluorescence and magnetic resonance imaging in cancer cells. FCF NPs exhibited promising anticancer activity in an irradiation time- and FCF NPs-dose-dependent manner in various cancer cell lines, leading to apoptotic cell death via morphological changes in cell membrane, nuclear, and DNA damage, and via overexpression of apoptosis-related genes, such as ZFP36L1, CYR61, GADD45G, caspases-2, -3, -9, 10, and -14. This study suggests that FCF NPs may be safely used in cancer therapy via PDT and could be a versatile therapeutic tool and biocompatible theragnostic agent, which may be used in diagnostic imaging.

In vitro comparison of conventional surgical and rotary ultrasonic bone drilling techniques

In orthopedic and trauma surgical operations, drilling of bone is one of the commonly used procedures performed in hospitals and is a clinical practice for fixing the fractured parts of human bones. Force, torque and temperature play a significant role during the bone drilling and decide the stability of the medical implants. Therefore, it is necessary to minimize force, torque and temperature while drilling to avoid the thermal necrosis and osteosynthesis. This study focused on studying the influence of various types of bone drilling parameters (rotational speed, feed rate, drill diameter and ultrasonic amplitude), tools (solid tool, hollow tool and conventional twist drill bit) and techniques (conventional surgical drilling, rotary ultrasonic bone drilling and rotary bone drilling) on force, torque, temperature and microcracks produced in the drilled surface of the bone. The experimental investigations were conducted on porcine bone samples to perform the comparative study. Results revealed that increasing the diameter of drill tool and feed rate results in the increase in force, torque and temperature, while low rotational speed (500 r/min) generated a low temperature, high cutting force and torque for all types of drilling processes and tools evaluated in this study. Experimental results also revealed that rotary ultrasonic bone drilling with hollow tool generated the lowest cutting force, torque, temperature (<47 °C) and microcracks in the drilled surface of the bone as compared to the other four types of drilling techniques evaluated in this study. Influence of external irrigation technique on temperature was also studied with respect to the rotary ultrasonic bone drilling with a hollow tool, which could eliminate the problem of thermal necrosis. In conclusion, this study revealed that the rotary ultrasonic bone drilling process with hollow tool produced lesser cutting force as compared to rotary bone drilling and conventional surgical drilling for hollow and solid tools. The study also revealed that rotary ultrasonic bone drilling process has the potential to minimize the cutting force, torque and temperature as compared to the conventional surgical drilling for orthopedic surgery.

Rapid development of dual porous poly(lactic acid) foam using fused deposition modeling (FDM) 3D printing for medical scaffold application

The poor melt property and brittleness of poly(lactic acid) (PLA) cause difficulties in extrusion foaming and decrease product performance in industrial and research fields. In this paper, the rheological properties of PLA resin were improved using an epoxy chain extension reaction, which led to the improvement of pore properties such as morphology and foamability. Reinforced PLA was extruded in a porous filament, and a scaffold was fabricated with design freedom, one-step processing, and dual porosity by extrusion foaming and 3D printing. In addition, in vitro cell culture tests were performed to verify the cell biology assessment and confirm the potential of the scaffold for application as medical scaffolds.

Biofunctionalization of Natural Fiber-Reinforced Biocomposites for Biomedical Applications

In the last ten years, environmental consciousness has increased worldwide, leading to the development of eco-friendly materials to replace synthetic ones. Natural fibers are extracted from renewable resources at low cost. Their combination with synthetic polymers as reinforcement materials has been an important step forward in that direction. The sustainability and excellent physical and biological (e.g., biocompatibility, antimicrobial activity) properties of these biocomposites have extended their application to the biomedical field. This paper offers a detailed overview of the extraction and separation processes applied to natural fibers and their posterior chemical and physical modifications for biocomposite fabrication. Because of the requirements for biomedical device production, specialized biomolecules are currently being incorporated onto these biocomposites. From antibiotics to peptides and plant extracts, to name a few, this review explores their impact on the final biocomposite product, in light of their individual or combined effect, and analyzes the most recurrent strategies for biomolecule immobilization.

Influence of the mechanical properties of biomaterials on degradability, cell behaviors and signaling pathways: current progress and challenges

We have clarified the influence of the mechanical properties of biomaterials on degradability and cell response, and also mechanical design targets and approaches.

Osseointegrated membranes based on electro-spun TiO2/hydroxyapatite/polyurethane for oral maxillofacial surgery

Membranes which have an osseointegration abilty are often selected as biomaterials in oral and maxillofacial surgery. Although these membranes are often the best option for certain uses, it is a challenge to create functionally attractive membranes. In this research, electro-spun titanium oxide (TiO2)/hydroxyapatite (HA)/polyurethane (PU) membranes were fabricated with different ratios of HA and TiO2: 100: 0, 70:30, 50:50, 30:70 and 0:100 w/w. The morphologies of the different mixtures were assessed with a Scanning Electron Microscope (SEM) and Field Emission Microscope (FESEM). Element analysis was performed with EDX. The physical properties of the water contact angles and mechanical strength were tested and the membranes cultured with osteoblasts to evaluate their biological functions, cell adhesion, viability, proliferation, alkaline phosphatase (ALP) activity, and calcium content. The results showed that the membranes with TiO₂ and HA had smaller fibers than those without TiO₂ and HA. The TiO2- and HA-including compounds showed the formation of particle aggregation on the surface of the fibers. They also had higher water contact angles, mechanical strength, and stiffness than those without TiO₂ and HA, and they had better cell adhesion, viability, proliferation, ALP activity and calcium content. The membrane with a 50:50 TiO₂:HA ratio had more unique biological functions than the others. Finally, our research demonstrated that osseointegrated membranes with 50:50 TiO2:HA are promising for oral and maxillofacial surgery.

Using Chitosan Besides Nano Hydroxyapatite and Fluorohydroxyapatite Boost Dental Pulp Stem Cell Proliferation

The dental tissue scaffold must provide a favorable surface for dental pulp stem cell attachment and proliferation. Employing nanohydroxyapatite (HA) and nanofluorohydroxyapatite (FHA) beside synthetic and organic polymer in favor of scaffolds would be used in bone and dental tissue engineering. In this research, nanoHA and FHA/chitosan scaffolds were synthesized by freeze-drying technique. Surface morphology, chemical composition and hydrophilicity have a great impact on initial cell attachment which will further affect the cell viability and proliferation which evaluated by SEM, XRD and contact angle measurement. Bioactivity of scaffolds was investigated by immersion in simulated body fluid (SBF) and cell proliferation assay. In freeze-drying technique percentage usage of hydroxyapatite could be risen up to 40% and shown better macro-mechanical and physical properties and bioactivity. According to obtained results by adding chitosan, contact angle was decreased by %54 and %37 for polycaprolactone (PCL)/HA and PCL/FHA scaffolds. In addition, addition of chitosan causes significant increase in the cell proliferation for PCL/HA and PCL/FHA up to 81% and 164%, respectively. These results indicate that PCL/FHA/chitosan scaffold represent a big potential for dental tissue engineering.

3D bioprinted complex constructs reinforced by hybrid multilayers of electrospun nanofiber sheets

Despite the usefulness of hydrogels for cell-based bioprinting, the fragility of their resulting constructs has hindered their practical applications in tissue engineering research. Here, we suggest a hybrid integration method based on cell-hydrogel bioprinting that includes alternate layering of flexible nanofiber (NF) sheets. Because the bioprinting was implemented on a nanofibrous surface, the hydrogel-based materials could be printed with enhanced shape resolution compared to printing on a bare hydrogel. Furthermore, the insertion of NF sheets was effective for alleviating the shrinkage distortion of the hydrogel construct, which is inherently generated during the crosslinking process, thereby enhancing shape fidelity throughout the three-dimensional (3D) architecture. In addition to the structural precision, the NF-embedded constructs improved the mechanical properties in terms of compressive strength, modulus, and resilience limit (up to four-fold enhancement). With structural and mechanical supports, we could 3D fabricate complex constructs, including fully opened internal channels, which provided a favorable perfusion condition for cell growth. We confirmed the enhanced bioactivity of the NF-embedded bioprinted construct via cell culture experiments with 80% enhanced proliferation compared to the monolithic one. The synergistic combination of the two flexible materials, NFs and hydrogels, is expected to have extensive applicability in soft tissue engineering.

Tunable Enzymatically Cross-Linked Silk Fibroin Tubular Conduits for Guided Tissue Regeneration

Hollow tubular conduits (TCs) with tunable architecture and biological properties are in great need for modulating cell functions and drug delivery in guided tissue regeneration. Here, a new methodology to produce enzymatically cross-linked silk fibroin TCs is described, which takes advantage of the tyrosine groups present in silk structure that are known to allow the formation of a covalently cross-linked hydrogel. Three different processing methods are used as a final step to modulate the properties of the silk-based TCs. This approach allows to virtually adjust any characteristic of the final TCs. The final microstructure ranges from a nonporous to a highly porous network, allowing the TCs to be selectively porous to 4 kDa molecules, but not to human skin fibroblasts. Mechanical properties are dependent both on the processing method and thickness of the TCs. Bioactivity is observed after 30 days of immersion in simulated body fluid only for the TCs submitted to a drying processing method (50 °C). The in vivo study performed in mice demonstrates the good biocompatibility of the TCs. The enzymatically cross-linked silk fibroin TCs are versatile and have adjustable characteristics that can be exploited in a variety of biomedical applications, particularly in guidance of peripheral nerve regeneration.

Living nanofiber yarn-based woven biotextiles for tendon tissue engineering using cell tri-culture and mechanical stimulation

Non-woven nanofibrous scaffolds have been developed for tendon graft application by using electrospinning strategies. However, electrospun nanofibrous scaffolds face some obstacles and limitations, including suboptimal scaffold structure, weak tensile and suture-retention strengths, and compact structure for cell infiltration. In this work, a novel nanofibrous, woven biotextile, fabricated based on electrospun nanofiber yarns, was implemented as a tissue engineered tendon scaffold. Based on our modified electrospinning setup, polycaprolactone (PCL) nanofiber yarns were fabricated with reproducible quality, and were further processed into plain-weaving fabrics interlaced with polylactic acid (PLA) multifilaments. Nonwoven nanofibrous PCL meshes with random or aligned fiber structures were generated using typical electrospinning as comparative counterparts. The woven fabrics contained 3D aligned microstructures with significantly larger pore size and obviously enhanced tensile mechanical properties than their nonwoven counterparts. The biological results revealed that cell proliferation and infiltration, along with the expression of tendon-specific genes by human adipose derived mesenchymal stem cells (HADMSC) and human tenocytes (HT), were significantly enhanced on the woven fabrics compared with those on randomly-oriented or aligned nanofiber meshes. Co-cultures of HADMSC with HT or human umbilical vein endothelial cells (HUVEC) on woven fabrics significantly upregulated the functional expression of most tenogenic markers. HADMSC/HT/HUVEC tri-culture on woven fabrics showed the highest upregulation of most tendon-associated markers than all the other mono- and co-culture groups. Furthermore, we conditioned the tri-cultured constructs with dynamic conditioning and demonstrated that dynamic stretch promoted total collagen secretion and tenogenic differentiation. Our nanofiber yarn-based biotextiles have significant potential to be used as engineered scaffolds to synergize the multiple cell interaction and mechanical stimulation for promoting tendon regeneration.

STATEMENT OF SIGNIFICANCE

Tendon grafts are essential for the treatment of various tendon-related conditions due to the inherently poor healing capacity of native tendon tissues. In this study, we combined electrospun nanofiber yarns with textile manufacturing strategies to fabricate nanofibrous woven biotextiles with hierarchical features, aligned fibrous topography, and sufficient mechanical properties as tendon tissue engineered scaffolds. Comparing to traditional electrospun random or aligned meshes, our novel nanofibrous woven fabrics possess strong tensile and suture-retention strengths and larger pore size. We also demonstrated that the incorporation of tendon cells and vascular cells promoted the tenogenic differentiation of the engineered tendon constructs, especially under dynamic stretch. This study not only presents a novel tissue engineered tendon scaffold fabrication technique but also provides a useful strategy to promote tendon differentiation and regeneration.

Fiber-reinforced scaffolds in soft tissue engineering

Soft tissue engineering has been developed as a new strategy for repairing damaged or diseased soft tissues and organs to overcome the limitations of current therapies. Since most of soft tissues in the human body are usually supported by collagen fibers to form a three-dimensional microstructure, fiber-reinforced scaffolds have the advantage to mimic the structure, mechanical and biological environment of natural soft tissues, which benefits for their regeneration and remodeling. This article reviews and discusses the latest research advances on design and manufacture of novel fiber-reinforced scaffolds for soft tissue repair and how fiber addition affects their structural characteristics, mechanical strength and biological activities in vitro and in vivo. In general, the concept of fiber-reinforced scaffolds with adjustable microstructures, mechanical properties and degradation rates can provide an effective platform and promising method for developing satisfactory biomechanically functional implantations for soft tissue engineering or regenerative medicine.

Recent advances on biomedical applications of scaffolds in wound healing and dermal tissue engineering

The tissue engineering field has developed in response to the shortcomings related to the replacement of the tissues lost to disease or trauma: donor tissue rejection, chronic inflammation and donor tissue shortages. The driving force behind the tissue engineering is to avoid the mentioned issues by creating the biological substitutes capable of replacing the damaged tissue. This is done by combining the scaffolds, cells and signals in order to create the living, physiological, three-dimensional tissues. A wide variety of skin substitutes are used in the treatment of full-thickness injuries. Substitutes made from skin can harbour the latent viruses, and artificial skin grafts can heal with the extensive scarring, failing to regenerate structures such as glands, nerves and hair follicles. New and practical skin scaffold materials remain to be developed. The current article describes the important information about wound healing scaffolds. The scaffold types which were used in these fields were classified according to the accepted guideline of the biological medicine. Moreover, the present article gave the brief overview on the fundamentals of the tissue engineering, biodegradable polymer properties and their application in skin wound healing. Also, the present review discusses the type of the tissue engineered skin substitutes and modern wound dressings which promote the wound healing.

The effect of mechanical loads on the degradation of aliphatic biodegradable polyesters

Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices. The performances during biodegradation process play crucial roles for final realization of their functions. Because physiological and biochemical environment in vivo significantly affects biodegradation process, large numbers of studies on effects of mechanical loads on the degradation of aliphatic biodegradable polyesters have been launched during last decades. In this review article, we discussed the mechanism of biodegradation and several different mechanical loads that have been reported to affect the biodegradation process. Other physiological and biochemical factors related to mechanical loads were also discussed. The mechanical load could change the conformational strain energy and morphology to weaken the stability of the polymer. Besides, the load and pattern could accelerate the loss of intrinsic mechanical properties of polymers. This indicated that investigations into effects of mechanical loads on the degradation should be indispensable. More combination condition of mechanical loads and multiple factors should be considered in order to keep the degradation rate controllable and evaluate the degradation process in vivo accurately. Only then can the degradable devise achieve the desired effects and further expand the special applications of aliphatic biodegradable polyesters.

The use of bioactive peptides to modify materials for bone tissue repair

It has been well recognized that the modification of biomaterials with appropriate bioactive peptides could further enhance their functions. Especially, it has been shown that peptide-modified bone repair materials could promote new bone formation more efficiently compared with conventional ones. The purpose of this article is to give a general review of recent studies on bioactive peptide-modified materials for bone tissue repair. Firstly, the main peptides for inducing bone regeneration and commonly used methods to prepare peptide-modified bone repair materials are introduced. Then, current in vitro and in vivo research progress of peptide-modified composites used as potential bone repair materials are reviewed and discussed. Generally speaking, the recent related studies have fully suggested that the modification of bone repair materials with osteogenic-related peptides provide promising strategies for the development of bioactive materials and substrates for enhanced bone regeneration and the therapy of bone tissue diseases. Furthermore, we have proposed some research trends in the conclusion and perspectives part.

Disruption of diphenylalanine assembly by a Boc-modified variant

Peptide-based biomaterials are key to the future of diagnostics and therapy, promoting applications such as tissue scaffolds and drug delivery vehicles. To realise the full potential of the peptide systems, control and optimisation of material properties are essential. Here we investigated the co-assembly of the minimal amyloid motif peptide, diphenylalanine (FF), and its tert-butoxycarbonyl (Boc)-modified derivative. Using Atomic Force Microscopy, we demonstrated that the co-assembled fibers are less rigid and show a curvier morphology. We propose that the Boc-modification of FF disrupts the hydrogen bond packing of adjacent N-termini, as supported by Fourier transform infrared and fluorescence spectroscopic data. Such rationally modified co-assemblies offer chemical functionality for after-assembly modification and controllable surface properties for tissue engineering scaffolds, along with tunable morphological vs. mechanical properties.

Hydrothermally processed 1D hydroxyapatite: Mechanism of formation and biocompatibility studies

Recent developments in bone tissue engineering have led to an increased interest in one-dimensional (1D) hydroxyapatite (HA) nano- and micro-structures such as wires, ribbons and tubes. They have been proposed for use as cell substrates, reinforcing phases in composites and carriers for biologically active substances. Here we demonstrate the synthesis of 1D HA structures using an optimized, urea-assisted, high-yield hydrothermal batch process. The one-pot process, yielding HA structures composed of bundles of ribbons and wires, was typified by the simultaneous occurrence of a multitude of intermediate reactions, failing to meet the uniformity criteria over particle morphology and size. To overcome these issues, the preparation procedure was divided to two stages: dicalcium phosphate platelets synthesized in the first step were used as a precursor for the synthesis of 1D HA in the second stage. Despite the elongated particle morphologies, both the precursor and the final product exhibited excellent biocompatibility and caused no reduction of viability when tested against osteoblastic MC3T3-E1 cells in 2D culture up to the concentration of 2.6mg/cm(2). X-ray powder diffraction combined with a range of electron microscopies and laser diffraction analyses was used to elucidate the formation mechanism and the microstructure of the final particles. The two-step synthesis involved a more direct transformation of DCP to 1D HA with the average diameter of 37nm and the aspect ratio exceeding 100:1. The comparison of crystalline domain sizes along different crystallographic directions showed no signs of significant anisotropy, while indicating that individual nanowires are ordered in bundles in the b crystallographic direction of the P63/m space group of HA. Intermediate processes, e.g., dehydration of dicalcium phosphate, are critical for the formation of 1D HA alongside other key aspects of this phase transformation, it must be investigated in more detail in the continuous design of smart HA micro- and nano-structures with advanced therapeutic potentials.

Effects of different fluid shear stress patterns on the in vitro degradation of poly(lactide-co-glycolide) acid membranes

The applications of poly (lactide-co-glycolide) acid (PLGA) for coating or fabricating polymeric biodegradable stents (BDSs) have drawn more attention. The fluid shear stress has been proved to affect the in vitro degradation process of PLGA membranes. During the maintenance, BDSs could be suffered different patterns of fluid shear stress, but the effect of these different patterns on the whole degradation process is unclear. In this study, in vitro degradation of PLGA membranes was examined with steady, sinusoid, and squarewave fluid shear stress patterns in 150 mL deionized water at 37°C for 20 days, emphasizing on the changes in the viscosity of the degradation solution, mechanical, and morphological properties of the samples. The unsteady fluid shear stress with the same average magnitude as the steady one accelerate the in vitro degradation process of PLGA membranes in terms of maximum fluid shear stress and "window" of effectiveness. Maximum fluid shear stress accelerates the in vitro degradation of molecular fragments that diffused out in the solution while the "window" of effectiveness affects too in the early stage. Besides, maximum fluid shear stress and "window" of effectiveness accelerates the in vitro loss of tensile modulus and ultimate strength of the PLGA membranes while the maximum fluid shear stress plays the leading role in the decrease of tensile modulus at the early degradation stage. This study could help advance the degradation design of PLGA membranes under different fluid shear stress patterns for biomedical applications like stents and drug release systems. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 23-30, 2017.

A novel method to in vitro evaluate biocompatibility of nanoscaled scaffolds

This study provided a new method to in vitro evaluate the biocompatibility of nanoscaled scaffolds for tissue engineering with neutrophils other than ordinary cell culture. The neutrophils were separated from human peripheral blood of healthy subjects. In vitro degradation product of nanohydroxyapatite/collagen (nHAC), nanohydroxyapatite/collagen/poly (L-lactic acid) (nHACP), and nHACP reinforced by chitin fibers (nHACP/CF) in the D-Hank's Balanced Salt Solution (D-HBSS) was used as the testing solution, which was thereafter mixed with the neutrophils. It was shown that the cell survival rate in the testing solutions had no significant difference from that in the D-HBSS (control). However, from both gene and protein expression levels, the lactate dehydrogenase and tumor necrosis factor-alpha of the neutrophils in the nHACP/CF testing solution were found lowest during the whole testing period; the main reasons of which might be that the calcium release rate of the scaffold was slowest and that the pH value of its degradation solution was nearest to that of human body. Moreover, in vivo experiments showed that most inflammation reactions happened for nHAC and poly (L-lactic acid) groups, while the least inflammation reactions happened for nHACP/CF group in the subcutaneous dorsum of mice at 2 weeks after the surgery, which confirmed the in vitro findings. These results indicated that the pH value and the certain metal iron concentration of the nanoscaled scaffold degradation solution should be two important factors that significantly affect its biocompatibility. This study provides a simple and effective biocompatibility test method for biodegradable nanoscaled tissue engineering scaffolds. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2117-2125, 2016.

Textile Technologies and Tissue Engineering: A Path Toward Organ Weaving

Textile technologies have recently attracted great attention as potential biofabrication tools for engineering tissue constructs. Using current textile technologies, fibrous structures can be designed and engineered to attain the required properties that are demanded by different tissue engineering applications. Several key parameters such as physiochemical characteristics of fibers, microarchitecture, and mechanical properties of the fabrics play important roles in the effective use of textile technologies in tissue engineering. This review summarizes the current advances in the manufacturing of biofunctional fibers. Different textile methods such as knitting, weaving, and braiding are discussed and their current applications in tissue engineering are highlighted.

Textile cell-free scaffolds for in situ tissue engineering applications

In this article, the benefits offered by micro-fibrous scaffold architectures fabricated by textile manufacturing techniques are discussed: How can established and novel fiber-processing techniques be exploited in order to generate templates matching the demands of the target cell niche? The problems related to the development of biomaterial fibers (especially from nature-derived materials) ready for textile manufacturing are addressed. Attention is also paid on how biological cues may be incorporated into micro-fibrous scaffold architectures by hybrid manufacturing approaches (e.g. nanofiber or hydrogel functionalization). After a critical review of exemplary recent research works on cell-free fiber based scaffolds for in situ TE, including clinical studies, we conclude that in order to make use of the whole range of favors which may be provided by engineered fibrous scaffold systems, there are four main issues which need to be addressed: (1) Logical combination of manufacturing techniques and materials. (2) Biomaterial fiber development. (3) Adaption of textile manufacturing techniques to the demands of scaffolds for regenerative medicine. (4) Incorporation of biological cues (e.g. stem cell homing factors).

Formation of hierarchical bone-like apatites on silk microfiber templates via biomineralization

Hierarchical bone-like apatites can be formed on silk microfiber templates and the resulting biocomposites achieved good cytocompatibility.

Simultaneous inhibition of EGFR and MET receptors with phytochemical conjugated magnetic nanocarriers: in silico and in vitro study

Beta-sitosterol,dl-alpha-tocopherol and 1,3,8-P-menthatriene ofMentha piperitaconjugated superparamagnetic iron-oxide nanoparticles (SPIONs) potentially inhibit EGFR and MET expressing cancer cells.

Comparative evaluation of in vivo biocompatibility and biodegradability of regenerated silk scaffolds reinforced with/without natural silk fibers

Nowadays, exceptional advantages of silk fibroin over synthetic and natural polymers have impelled the scientists to application of this biomaterial for tissue engineering purposes. Recently, we showed that embedding natural degummed silk fibers in regenerated Bombyx mori silk-based scaffold significantly increases the mechanical stiffness, while the porosity of the scaffolds remains the same. In the present study, we evaluated degradation rate, biocompatibility and regenerative properties of the regenerated 2% and 4% wt silk-based composite scaffolds with or without embedded natural degummed silk fibers within 90 days in both athymic nude and wild-type C57BL/6 mice through subcutaneous implantation. In all scaffolds, a suitable interconnected porous structure for cell penetration was seen under scanning electron microscopy. Compressive tests revealed a functional relationship between fiber reinforcement and compressive modulus. In addition, the fiber/fibroin composite scaffolds support cell attachment and proliferation. On days 30 to 90 after subcutaneous implantation, the retrieved tissues were examined via gross morphology, histopathology, immunofluorescence staining and reverse transcription-polymerase chain reaction as shown in Figure 1 . Results showed that embedding the silk fibers within the matrix enhances the biodegradability of the matrix resulting in replacement of the composite scaffolds with the fresh connective tissue. Fortification of the composites with degummed fibers not only regulates the degradation profile but also increases the mechanical performance of the scaffolds. This report also confirmed that pore size and structure play an important role in the degradation rate. In conclusion, the findings of the present study narrate key role of additional surface area in improving in vitro and in vivo biological properties of the scaffolds and suggest the potential ability of these fabricated composite scaffolds for connective tissue regeneration. [Figure: see text]