Artificial Tissue Engineering Research Articles

Review of Spider Silk Applications in Biomedical and Tissue Engineering.

This review will present the latest research related to the production and application of spider silk and silk-based materials in reconstructive and regenerative medicine and tissue engineering, with a focus on musculoskeletal tissues, and including skin regeneration and tissue repair of bone and cartilage, ligaments, muscle tissue, peripheral nerves, and artificial blood vessels. Natural spider silk synthesis is reviewed, and the further recombinant production of spider silk proteins. Research insights into possible spider silk structures, like fibers (1D), coatings (2D), and 3D constructs, including porous structures, hydrogels, and organ-on-chip designs, have been reviewed considering a design of bioactive materials for smart medical implants and drug delivery systems. Silk is one of the toughest natural materials, with high strain at failure and mechanical strength. Novel biomaterials with silk fibroin can mimic the tissue structure and promote regeneration and new tissue growth. Silk proteins are important in designing tissue-on-chip or organ-on-chip technologies and micro devices for the precise engineering of artificial tissues and organs, disease modeling, and the further selection of adequate medical treatments. Recent research indicates that silk (films, hydrogels, capsules, or liposomes coated with silk proteins) has the potential to provide controlled drug release at the target destination. However, even with clear advantages, there are still challenges that need further research, including clinical trials.

Tissue Engineering for Cardiovascular Regeneration: Brief Review on Scaffold Fabrication

Tissue engineering is the combination of engineering and fundamental sciences to develop an artificial organ that derived from the tissue human sources. It involves the construction of three main pillars include cell sources, scaffold materials and biological factors. These three important elements are necessary to be incorporated and integrated well, to construct a functional artificial tissue engineering product. Few applications can be associated with the expansion of tissue engineering where cardiovascular regeneration is one of the targets of tissue engineering. Among the fabrication techniques, electrospinning, three-dimensional printing, molding and decellularization, are four engineering methods that are commonly used in fabricating scaffolds for cardiovascular tissue engineering. One of the purposes of the emerging of cardiovascular tissue engineering is the limitation of current commercialized patches or membranes that often cause post-complications following the cardiovascular treatments. This review paper covering a brief introduction on the tissue engineering for cardiovascular regeneration, focusing on the scaffold fabrication.

Synthesis of pure and Cd-doped hydroxyapatite for the photo-catalytic degradation of Amoxicillin and Ciprofloxacin: Crystallographic characterization using XRD

Nanosized hydroxyapatite (HAp) is considered an elementary material for artificial bone tissue engineering and the applications are expanding and one of them is the photocatalytic degradation of environmentally hazardous pollutants. In this research, HAp nanoparticles, in pure form and doped with cadmium (Cd), were synthesized using a conventional wet-chemical precipitation method. Additionally, the synthesized samples such as pure and Cd-doped HAp were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis spectroscopy. Moreover, the XRD analysis allowed for a detailed estimation of the crystallite size, assisting in their tailoring of increased photocatalytic activity. The crystallite sizes of the nano-crystallite Hap were evaluated using the Scherrer Method (SM), Williamson-Hall Method (WHM), Size-Strain Plot (SSP), Halder-Wagner Method (HWM), and Sahadat-Scherrer Method (SSM). The models confirmed the formation of nano crystallite hydroxyapatite in pure and doped form. Cadmium doping in HAp showed great photocatalytic activity for example at 150 min, 31 % amoxicillin and 52 % ciprofloxacin were degraded upon 1.5 wt % Cd doping in HAp crystal. The research demonstrated that doping Cd in HAp crystal improved photocatalytic activity towards antibiotic solution (ciprofloxacin and amoxicillin) under all test circumstances.

Current materials used in artificial vascular tissue engineering

Current materials used in artificial vascular tissue engineering

Synthesis and specific biomedical applications of polymer brushes

The modification of surfaces with various polymer chains through interactions involving strong covalent bonds is a current focal point. The relevance of this subject lies in the diversification of polymeric structures, particularly applicable in biomedical engineering and medicine. Presently, designs for drug carrier systems have reached an advanced stage, and novel polymer-based materials have been successfully synthesized. Polymeric brushes find applications in crucial medical areas such as artificial tissue engineering, implants, and biosensors. The advantages of polymeric brushes include their sensitivity to stimuli, a variety of polymer types and synthesis methods, tunability, and high biocompatibility. This study comparatively examines grafting approaches and polymerization techniques frequently encountered in the literature, highlighting their primary medical applications.

Pectin/PVA-Borax Hydrogel with Self-Healing Ability

Hydrogels are polymers with soft and high-water absorption characteristics similar to biological tissues, leading to several potential applications, such as artificial organs, drug delivery, tissue engineering, and strain sensor. Interestingly, hydrogels can be designed to heal themselves after being damaged. In this research, hydrogels with self-healing ability from pectin and polyvinyl alcohol were prepared by simple physical mixing. Borax was used as a crosslinking agent to obtain crosslinked hydrogel structure by the formation of dynamic boron ester bonds. Glycerol was also added to the hydrogels as an anti-freezing agent and a stabilizer. The microstructures, mechanical properties, self-healing ability and swelling properties of the pectin/PVA-borax hydrogels were characterized. The results indicate that the size of microporous structure, modulus, tensile strength, self-healing time, swelling, and equilibrium water content of the pectin/PVA hydrogels increases with the increasing borax contents.

3D printed cathodes for implantable abiotic biofuel cells

3D printing has recently triggered huge attention in several fields such as construction, artificial tissue engineering, food fabrication, wearable electronics, and electrochemical energy storage.This work investigates the fabrication of a 3D-printed abiotic cathode for implantable glucose/oxygen biofuel cells. The ink formulation was optimized to get printable ink with high electro-catalytic activity. Electrode macro porosity was screened in order to identify the better compromise between electrode density and electrochemical performance. A maximum current density of 260 μA/cm2 was obtained with cylindrical electrodes with linear mesh infill and a volumic infill rate of 40%.A complete biofuel cell was assembled using a 3D-printed abiotic cathode and an enzymatic anode in the form of a compressed pellet showing maximum power and current densities of 80 μW/cm2 and 320 μA/cm2, respectively. Moreover, the hybrid biofuel cell was implanted in the intraabdominal region of a rat for three months and after cell explantation, the abiotic cathode displayed a 50% decrease in the current density while the enzymatic anode did not display any residual activity.The 3D printed electrode displayed a 2–3.6 fold increase in current density when compared to homolog 2D electrodes.

4D printing of biodegradable shape memory double-network hydrogel for highly bionic devices

Hydrogels are attractive for bionic devices due to their sensing ability and flexibility, similar to human skin. However, current hydrogels hardly combine mechanical, water retention, sensing, actuating, and degradation performances, which significantly limits the application of hydrogels in highly bionic devices. In this paper, a biodegradable shape memory 4D printing hydrogel ink was prepared by bio-polyurethane (BPU), carboxymethyl chitosan (CMCS), and carbomer (CBM). The hydrogel ink had a high tensile strength (stress of 0.66 MPa, elongation at break of 643%), outstanding water retention (>85.87%), ionic conductivity (8.59 S m−1), and excellent sensing performance (S = 0.051 kPa−1, GF = 2.9). Fourier transform infrared reflection, X-ray diffractometer, and X-ray photoelectron spectroscopy data showed that the BPU, CMCS, and CBM form a double network structure through chemical, hydrogen, and ionic bonding cross-linking, respectively. After 4D printing, a continuous pore structure could be observed by scanning electron microscopy in the hydrogel model. The continuous pore structure provided channels for the movement of ions in the hydrogel model so that the pressure could be converted into a specific signal. Following the signal, a computer-controlled temperature rapidly heated the hydrogel model to 50 °C, and the hydrogel model could change shape autonomously. The excellent properties and highly bionic functions of biodegradable shape memory double-network hydrogel have broken through the limitations of applications in artificial intelligence robotics, human-machine interfaces, tissue engineering, and other fields.

Low-dimensionality carbon-based biosensors: the new era of emerging technologies in bioanalytical chemistry.

Since the last decade, carbon nanomaterials have had a notable impact on different fields such as bioimaging, drug delivery, artificial tissue engineering, and biosensors. This is due to their good compatibility toward a wide range of chemical to biological molecules, low toxicity, and tunable properties. Especially for biosensor technology, the characteristic features of each dimensionality of carbon-based materials may influence the performance and viability of their use. Surface area, porous network, hybridization, functionalization, synthesis route, the combination of dimensionalities, purity levels, and the mechanisms underlying carbon nanomaterial interactions influence their applications in bioanalytical chemistry. Efforts are being made to fully understand how nanomaterials can influence biological interactions, to develop commercially viable biosensors, and to gain knowledge on the biomolecular processes associated with carbon. Here, we present a comprehensive review highlighting the characteristic features of the dimensionality of carbon-based materials in biosensing.

Low coefficient of friction hydrogels with fast self-healing properties inspired by articular cartilage

Hydrogels have potential applications in artificial cartilage, soft robotics, and tissue engineering, owing to their excellent wettability, flexibility, and biocompatibility. However, poor lubrication and fragile mechanical properties often limit their applications. In nature, articular cartilage and cornea are coated by brush-like mucous to realize lubrication. Herein, we present a nature-inspired strategy for improving the lubrication properties of hydrogels. A model hydrogel is prepared using poly(vinyl alcohol), borax, and poly(ethylene oxide). The PEO forms a brush-like hydrophilic lubricating layer on the surface of the hydrogel. Thus, the PVA/Borax/PEO hydrogel exhibits a low coefficient of friction (0.08). In addition, after healing for 30 s in the air, the PVA/Borax/PEO hydrogel with a dynamic borate bond exhibit a 93 % cure in strength. Moreover, PVA/Borax/PEO hydrogels also exhibit excellent underwater self-healing ability. With the combination of lubrication and self-healing properties, the PVA/Borax/PEO hydrogels have great potential for use in a wide variety of fields.

The Advances of Hydrosol–Gel Transition-Based Sensors

Hydrogels, as a type of three-dimensional porous material, have attracted a lot of attention in the fields of drug delivery, artificial tissue engineering, and sensing. Due to their excellent biocompatibility and high sensitivity to external stimuli, they are widely used in the development of various sensors. Among them, the sensors constructed based on the sol–gel transition of target-responsive hydrogels are particularly welcome. Herein, the status of the sensors on the basis of sol–gel transition has been presented. The types of hydrogel sensors and the analytical methods in various application scenarios are illustrated. In addition, the future trends of the sensing systems based on sol–gel transition are briefly discussed.

Bone Tissue Engineering through 3D Bioprinting of Bioceramic Scaffolds: A Review and Update.

Trauma and bone loss from infections, tumors, and congenital diseases make bone repair and regeneration the greatest challenges in orthopedic, craniofacial, and plastic surgeries. The shortage of donors, intrinsic limitations, and complications in transplantation have led to more focus and interest in regenerative medicine. Structures that closely mimic bone tissue can be produced by this unique technology. The steady development of three-dimensional (3D)-printed bone tissue engineering scaffold therapy has played an important role in achieving the desired goal. Bioceramic scaffolds are widely studied and appear to be the most promising solution. In addition, 3D printing technology can simulate mechanical and biological surface properties and print with high precision complex internal and external structures to match their functional properties. Inkjet, extrusion, and light-based 3D printing are among the rapidly advancing bone bioprinting technologies. Furthermore, stem cell therapy has recently shown an important role in this field, although large tissue defects are difficult to fill by injection alone. The combination of 3D-printed bone tissue engineering scaffolds with stem cells has shown very promising results. Therefore, biocompatible artificial tissue engineering with living cells is the key element required for clinical applications where there is a high demand for bone defect repair. Furthermore, the emergence of various advanced manufacturing technologies has made the form of biomaterials and their functions, composition, and structure more diversified, and manifold. The importance of this article lies in that it aims to briefly review the main principles and characteristics of the currently available methods in orthopedic bioprinting technology to prepare bioceramic scaffolds, and finally discuss the challenges and prospects for applications in this promising and vital field.

A multi-axis robot-based bioprinting system supporting natural cell function preservation and cardiac tissue fabrication.

Despite the recent advances in artificial tissue and organ engineering, how to generate large size viable and functional complex organs still remains as a grand challenge for regenerative medicine. Three-dimensional bioprinting has demonstrated its advantages as one of the major methods in fabricating simple tissues, yet it still faces difficulties to generate vasculatures and preserve cell functions in complex organ production. Here, we overcome the limitations of conventional bioprinting systems by converting a six degree-of-freedom robotic arm into a bioprinter, therefore enables cell printing on 3D complex-shaped vascular scaffolds from all directions. We also developed an oil bath-based cell printing method to better preserve cell natural functions after printing. Together with a self-designed bioreactor and a repeated print-and-culture strategy, our bioprinting system is capable to generate vascularized, contractible, and long-term survived cardiac tissues. Such bioprinting strategy mimics the in vivo organ development process and presents a promising solution for in vitro fabrication of complex organs.

Laser Assisted Bioprinting of laminin on biodegradable PLGA substrates: Effect on neural stem cell adhesion and differentiation

Laser Assisted Bioprinting (LAB) is recognized to be an enabling and versatile microfabrication technology for regenerative medicine and artificial tissue engineering. Current bioprinting concentrates on a layer-by-layer approach to print cells in consecutive stacks or nets, to recreate specialized tissue functions with a top-down approach. This synthering of proximal cells however reduces the long range correlation of tissue parenchyma and stroma given by natural development, as result of cells mobility and signaling. In this work, laminin, one of the main components of brain extracellular matrix is deposited by LAB on a biodegradable scaffold made of poly(lactic-co-glycolic acid) (PLGA), providing chemical cues for the adhesion and differentiation of neural stem cells NE-4C induced by retinoic acid. Surface roughness and LAB induced aggregates promote the initial adhesion of neuronal stem cells to the PLGA substrate and influence the formation of clusters and interconnection between them. The amount of laminin delivered inside the spot area may be controlled down to sub-monolayer coverage and a positive correlation between the laminin spots and soma of trafficking cells is demonstrated, also by computational modelling. Anisotropic orientation of neurite outgrowth is induced upon differentiation, up to 70% of processes protruding from stem cell clusters. The comparative analysis shows that the topological cue plays a major role in enhabling cluster formation on the scaffold, but the bioprinted laminin spots appear to be regulating the strength of connection between them, opening the way to control the functional morphology of artificial neural tissue constructs.

Chitosan/Polyvinyl Alcohol/ Lauramidopropyl Betaine/2D-HOF Mixed Film with Abundant Hydrogen Bonds Acts as High Mechanical Strength Artificial Skin.

The mechanical properties of artificial skins are complicated to maintain under ensuring air permeability and antimicrobial. Thus, a series of hydrophilic antimicrobial polymer networks are prepared by crosslinking chitosan and polyvinyl alcohol with the lauramidopropyl betaine and hydrogen bond organic framework (CS/PVA/LPB/2D-HOF). The mechanical performance of the control groups and the complex are systematically evaluated to attain an artificial strength skin. The CS/PVA/LPB/2D-HOF complex exhibits strong mechanical abilities than other control groups. By analyzing the IR spectra and the morphology, the synergistic effect of hydrogen bonds between molecules and cracks significantly improves the mechanical properties of the complex. Its maximum tensile strength can reach 29 MPa, and its maximum load capacity can reach 3700 g. Notably, the composite membrane also performs an excellent antimicrobial activity. In vivo and in vitro experiments show that the hybrid membrane can promote tissue regeneration and wound healing (95％). These results may open up the opportunity for future composite material investigations in the artificial skin and tissue engineering field.

Tough hydrogels with tunable soft and wet interfacial adhesion

Hydrogels that possess adequate toughness in bulk and at soft interface are highly desirable. We report a fully physically crosslinked dual Amylopectin (Amy, the first network)/poly(N-hydroxyethyl acrylamide) (PHEAA, the second network) hydrogel, where both networks were hydrogen bonding (H-bonding) crosslinked, with super toughness in bulk and tunable adhesion at hydrogel-soft tissue interface. Through adjustment of hydrogen bond density, strong and tough hydrogels were prepared that exhibited different levels of adhesion strength and three adhesive failure mechanisms. We replaced Amy with oxidized starch (OSA) to synthesize dual and hybrid chemically/physically crosslinked OSA/PHEAA double network (DN) hydrogels that were capable of forming Schiff's bases at hydrogel-hydrogel or hydrogel-tissue interfaces, aside from interfacial H-bonding, incurring sustained, high interfacial toughness (1850 J m−2 hydrogel-hydrogel and 610 J m−2 hydrogel-tissue) in wet environments. Such tough and adhesive DN hydrogels have great potential in various applications such as engineering of artificial soft tissues or implantable devices that are intended to adhere to internal organs or tissues.

Functionalizing Double-Network Hydrogels for Applications in Remote Actuation and in Low-Temperature Strain Sensing.

Multifunctional hydrogels have important applications in various fields such as artificial muscles, wearable devices, soft robotics, and tissue engineering, especially for those with favorable mechanical properties, good low-temperature resistance, and stimuli-responsive capabilities. In the current study, a type of polyacrylamide/sodium alginate/carbon nanotube (PAAm/SA/CNT) double-network (DN) hydrogel was fabricated, which exhibited a high tensile strength of 271.68 ± 6.04 kPa, a favorable conductivity of 1.38 ± 0.17 S·m-1, and a good self-healing ability under heating conditions. In addition, the composite hydrogel exhibited controllable photomechanical deformations under near-infrared irradiation, such as bending, swelling, swimming, and object grasping. To further broaden the applications of the hydrogel in low-temperature environments, calcium chloride (CaCl2) was introduced into such a PAAm/SA/CNT DN hydrogel as an additive. Interestingly, the tensile/compressive strengths as well as elasticity were well-maintained at a temperature as low as -20 °C. In addition, the PAAm/SA/CNT/CaCl2 hydrogel presented excellent conductivity, recoverability, and strain-sensing capability under such extreme conditions. Overall, the investigations conducted in this paper have provided potentially new methods and inspirations for the generation of multifunctional PAAm/SA/CNT/CaCl2 hybrid DN hydrogels toward extended applications.

Effect of mold assemblies-induced interfaces in the mechanical actuation of electro-responsive ionic liquid-based polycationic hydrogels

This work aims the development of electro-active polycationic soft-actuators based on copolymers of 2-hydroxyethyl methacrylate (HEMA) and 1-butyl-3-vinylimidazolium chloride (BVImCl), cross-linked with N,N’-methylene bis(acrylamide), and reinforced with mesoporous silica nanoparticles. Polycationic hydrogels were obtained by free radical polymerization in aqueous solution and using mold assemblies presenting different surface properties (e.g. Teflon® and glass). Obtained results demonstrated that a mold assembly-induced effect, at the mold/polymerization solution interface, originates “surface-to-bulk” heterogeneous copolymer concentration gradients when using Teflon®-Teflon® and Teflon®-glass mold assemblies, while homogeneous hydrogel networks were obtained when using only glass mold assemblies. Results were compared with those obtained from cross-linked poly(2-hydroxyethyl methacrylate) hydrogels to prove that the observed surface-induced polymerization effect occurs only in the presence of the ionic liquid co-monomer. Hydrogels synthesized in Teflon®-Teflon® molds presented the highest mechanical response under external electric stimulus and in different aqueous media of different pH and ionic strength. On the contrary, hydrogels synthesized in glass-glass mold assemblies presented limited mechanical actuation and only when immersed in saline aqueous media. The mechanical actuation of hydrogels synthesized in Teflon®-glass molds was shown to depend on the orientation of the applied electric current. The electro-actuation response of the synthesized electro-active polycationic hydrogels was discussed based on the ion enrichment/depletion mechanism. All prepared cationic hydrogels were also able to generate small electrical currents. Overall, these results show that mold assemblies presenting different surface properties can be employed to tune the electro-actuation responsiveness of ionic liquid-based soft actuators and lead to the development of engineering devices with a broad range of applications, including artificial muscles and tissue engineering scaffolds.

3D Printed Hydroxyapatite/Silk Fibroin/Polycaprolactone Artificial Bone Scaffold and Bone Tissue Engineering Materials Constructed with Double-Transfected Bone Morphogenetic Protein-2 and Vascular Endothelial Growth Factor Mesenchymal Stem Cells to Repair Rabbit Radial Bone Defects

To examine the effect of bone tissue engineering material constructed via 3D printed nanohydroxyapatite/silk fibroin/polycaprolactone (nHA/SF/PCL) artificial bone scaffolds and doubletransfected BMP-2/VEGF mesenchymal stem cells in repairing rabbit radial bone defects, 60 New Zealand rabbits were randomly selected, and with the establishment of a 15 mm bone defect model upon the middle of the anterior right radius bone. The rabbits were randomly divided into 4 groups, with each group composed of 15 rabbits: Group A (nHA/SF/PCL BMP-2/VEGF), Group B (simple nHA/SF/PCL), Group C (simple BMP-2/VEGF), Group D (blank control). Our team recorded the eating, movement, redness, exudation, and so forth across each sample group following the operation. The bone protein expression levels were measured via western blotting following 12 weeks post-operation. Histological observation was carried performed via tissue sections. Following the operation procedure, the wound healed healthily across the 4 experimental groups, no serious infections occurred, only a few rabbits exhibited redness, exudation, pus, and other phenomena, and there was no significant difference present in each group (P > 0.05). The A group took the shortest time to recover its autonomous activity ability, followed by the B group, and the D group took the longest time to recover its autonomous activity ability. From western blotting tests, the A group possessed the highest BMP-2 and OCN expression levels, and have significant difference existed with the B, C, and D group (P < 0.05). The order of expression level of BMP-2 and OCN across the other three groups were group C > group B > group D, respectively. The results of a histological section performed at 12 weeks post-operation revealed that there was no immune response present and no adverse inflammatory reaction occurring within each experimental group. Among the rabbits, the A group exhibited an apparent plate layer new bone formation, bone trabeculae were arranged regularly, and there was no obvious space within the new bone tissue; furthermore, the repair of the bone defect was completed. The B group still exhibited some bone scaffold remaining within the implantation area, and there was a small gap between the new bone tissue, and several bone defects had not been repaired. The C group of bone defects presented only a small number of new bone formation, and bone defect repair effect was not obvious. The D group still possessed large bone defects and exhibited poor repair of bone defects. The nHA/SF/PCL composite of artificial bone scaffold and double-transfected BMP-2/VEGF mesenchymal stem cells was effective in repairing radial bone defects within rabbits, and was superior to using nHA/SF/PCL bone scaffolds alone.

Biomimetic TiO2-chitosan/sodium alginate blended nanocomposite scaffolds for tissue engineering applications.

The study is aimed to synthesize potent metal oxide based biomimetic nanocomposites to overcome the risk associated with artificial bone tissue engineering. High purity TiO2 nanoparticles are synthesized via hydrothermal route. A biomimetic nanocomposite scaffolds containing chitosan-sodium alginate (4: 4) blended with three different (0.5, 1, and 1.5wt%) concentrations of hydrothermally synthesized TiO2 nanoparticles are obtained by solvent casting technique. The physico-chemical and thermal degradation properties of as-synthesized TiO2 nanoparticles and their nanocomposite scaffolds are analyzed. In-vitro cytotoxicity and biocompatibility of the prepared TiO2 nanoparticles and nanocomposites are tested against human bladder tumor (UC6) and osteosarcoma (MG-63) cell lines. Antibacterial property is tested against Escherichia coli and Staphylococcus aureus. These studies reveal that TiO2 nanoparticles and polymeric nanocomposites contain good physico-chemical and mechanical properties for enhanced in-vitro biocompatibility suitable for biomedical applications. Biomimetically prepared chitosan-sodium alginate scaffold containing TiO2 nanoparticles (1wt%) is found to exhibit superior biocompatibility for bone tissue engineering applications.