Mechanically reinforced hydrogel vehicle delivering angiogenic factor for beta cell therapy.

Type 1 diabetes mellitus (T1DM) is a chronic disease affecting millions worldwide. Insulin therapy is currently the golden standard for treating T1DM; however, it does not restore the normal glycaemic balance entirely, which increases the risk of secondary complications. Beta-cell therapy may be a possible way of curing T1DM and has already shown promising results in the clinic. However, low retention rates, poor cell survival, and limited therapeutic potential are ongoing challenges, thus increasing the need for better cell encapsulation devices. This study aimed to develop a mechanically reinforced vascular endothelial growth factor (VEGF)-delivering encapsulation device suitable for beta cell encapsulation and transplantation. Poly(l-lactide-co-ε-caprolactone) (PLCL)/gelatin methacryloyl (GelMA)/alginate coaxial nanofibres were produced using electrospinning and embedded in an alginate hydrogel. The encapsulation device was physically and biologically characterised and was found to be suitable for INS-1E beta cell encapsulation, vascularization, and transplantation in terms of its biocompatibility, porosity, swelling ratio and mechanical properties. Lastly, VEGF was incorporated into the hydrogel and the release kinetics and functional studies revealed a sustained release of bioactive VEGF for at least 14 days, making the modified alginate system a promising candidate for improving the beta cell survival after transplantation.

Smart alginate inks for tissue engineering applications.

Amazing achievements have been made in the field of tissue engineering during the past decades. However, we have not yet seen fully functional human heart, liver, brain, or kidney tissue emerge from the clinics. The promise of tissue engineering is thus still not fully unleashed. This is mainly related to the challenges associated with producing tissue constructs with similar complexity as native tissue. Bioprinting is an innovative technology that has been used to obliterate these obstacles. Nevertheless, natural organs are highly dynamic and can change shape over time; this is part of their functional repertoire inside the body. 3D-bioprinted tissue constructs should likewise adapt to their surrounding environment and not remain static. For this reason, the new trend in the field is 4D bioprinting - a new method that delivers printed constructs that can evolve their shape and function over time. A key lack of methodology for printing approaches is the scalability, easy-to-print, and intelligent inks. Alginate plays a vital role in driving innovative progress in 3D and 4D bioprinting due to its exceptional properties, scalability, and versatility. Alginate's ability to support 3D and 4D printing methods positions it as a key material for fueling advancements in bioprinting across various applications, from tissue engineering to regenerative medicine and beyond. Here, we review the current progress in designing scalable alginate (Alg) bioinks for 3D and 4D bioprinting in a "dry"/air state. Our focus is primarily on tissue engineering, however, these next-generation materials could be used in the emerging fields of soft robotics, bioelectronics, and cyborganics.

Sumecton reinforced gelatin-based scaffolds for cell-free bone regeneration.

Bone tissue engineering has risen to tackle the challenges of the current clinical need concerning bone fractures that is already considered a healthcare system problem. Scaffold systems for the repair of this tissue have yielded different combinations including biomaterials with nanotechnology or biological agents. Herein, three-dimensional porous hydrogels were engineered based on gelatin as a natural biomaterial and reinforced with synthetic saponite nanoclays. Scaffolds were biocompatible and shown to enhance the inherent properties of pristine ones, in particular, proved to withstand pressures similar to load-bearing tissues. Studies with murine mesenchymal stem cells found that scaffolds had the potential to proliferate and promote cell differentiation. In vivo experiments were conducted to gain insight about the ability of these cell-free scaffolds to regenerate bone, as well as to determine the role that these nanoparticles in the scaffold could play as a drug delivery system. SDF-1 loaded scaffolds showed the highest percentage of bone formation, which was corroborated by osteogenic markers and new blood vessels. Albeit a first attempt in the field of synthetic nanosilicates, these results suggest that the designed constructs may serve as delivery platforms for biomimetic agents to mend bony defects, circumventing high doses of therapeutics and cell-loading systems.

Multi-leveled Nanosilicate Implants Can Facilitate Near-Perfect Bone Healing.

Several studies have shown that nanosilicate-reinforced scaffolds are suitable for bone regeneration. However, hydrogels are inherently too soft for load-bearing bone defects of critical sizes, and hard scaffolds typically do not provide a suitable three-dimensional (3D) microenvironment for cells to thrive, grow, and differentiate naturally. In this study, we bypass these long-standing challenges by fabricating a cell-free multi-level implant consisting of a porous and hard bone-like framework capable of providing load-bearing support and a softer native-like phase that has been reinforced with nanosilicates. The system was tested with rat bone marrow mesenchymal stem cells in vitro and as a cell-free system in a critical-sized rat bone defect. Overall, our combinatorial and multi-level implant design displayed remarkable osteoconductivity in vitro without differentiation factors, expressing significant levels of osteogenic markers compared to unmodified groups. Moreover, after 8 weeks of implantation, histological and immunohistochemical assays indicated that the cell-free scaffolds enhanced bone repair up to approximately 84% following a near-complete defect healing. Overall, our results suggest that the proposed nanosilicate bioceramic implant could herald a new age in the field of orthopedics.

Genetically Engineered Viral Vectors and Organic-Based Non-Viral Nanocarriers for Drug Delivery Applications.

Conventional drug delivery systems are challenged by concerns related to systemic toxicity, repetitive doses, drug concentrations fluctuation, and adverse effects. Various drug delivery systems are developed to overcome these limitations. Nanomaterials are employed in a variety of biomedical applications such as therapeutics delivery, cancer therapy, and tissue engineering. Physiochemical nanoparticle assembly techniques involve the application of solvents and potentially harmful chemicals, commonly at high temperatures. Genetically engineered organisms have the potential to be used as promising candidates for greener, efficient, and more adaptable platforms for the synthesis and assembly of nanomaterials. Genetically engineered carriers are precisely designed and constructed in shape and size, enabling precise control over drug attachment sites. The high accuracy of these novel advanced materials, biocompatibility, and stimuli-responsiveness, elucidate their emerging application in controlled drug delivery. The current article represents the research progress in developing various genetically engineered carriers. Organic-based nanoparticles including cellulose, collagen, silk-like polymers, elastin-like protein, silk-elastin-like protein, and inorganic-based nanoparticles are discussed in detail. Afterward, viral-based carriers are classified, and their potential for targeted therapeutics delivery is highlighted. Finally, the challenges and prospects of these delivery systems are concluded.

Nanoclay-reinforced HA/alginate scaffolds as cell carriers and SDF-1 delivery-platforms for bone tissue engineering.

Bone tissue engineering has come on the scene to overcome the difficulties of the current treatment strategies. By combining biomaterials, active agents and growth factors, cells and nanomaterials, tissue engineering makes it possible to create new structures that enhance bone regeneration. Herein, hyaluronic acid and alginate were used to create biologically active hydrogels, and montmorillonite nanoclay was used to reinforce and stabilize them. The developed scaffolds were found to be biocompatible and osteogenic with mMSCs in vitro, especially those reinforced with the nanoclay, and allowed mineralization even in the absence of differentiation media. Moreover, an in vivo investigation was performed to establish the potential of the hydrogels to mend bone and act as cell-carriers and delivery platforms for SDF-1. Scaffolds embedded with SDF-1 exhibited the highest percentages of bone regeneration as well as of angiogenesis, which confirms the suitability of the scaffolds for bone. Although there are a number of obstacles to triumph over, these bioengineered structures showed potential as future bone regeneration treatments.

The 3D Bioprinted Scaffolds for Wound Healing.

Skin tissue engineering and regeneration aim at repairing defective skin injuries and progress in wound healing. Until now, even though several developments are made in this field, it is still challenging to face the complexity of the tissue with current methods of fabrication. In this review, short, state-of-the-art on developments made in skin tissue engineering using 3D bioprinting as a new tool are described. The current bioprinting methods and a summary of bioink formulations, parameters, and properties are discussed. Finally, a representative number of examples and advances made in the field together with limitations and future needs are provided.

3D-Printed Regenerative Magnesium Phosphate Implant Ensures Stability and Restoration of Hip Dysplasia.

Osteoarthritis of the hip is a painful and debilitating condition commonly occurring in humans and dogs. One of the main causes that leads to hip osteoarthritis is hip dysplasia. Although the current surgical methods to correct dysplasia work satisfactorily in many circumstances, these are associated with serious complications, tissue resorption, and degeneration. In this study, a one-step fabrication of a regenerative hip implant with a patient-specific design and load-bearing properties is reported. The regenerative hip implant is fabricated based on patient imaging files and by an extrusion assisted 3D printing process using a flexible, bone-inducing biomaterial. The novel implant can be fixed with metallic screws to host bone and can be loaded up to physiological loads without signs of critical permanent deformation or failure. Moreover, after exposing the hip implant to accelerated in vitro degradation, it is confirmed that it is still able to support physiological loads even after losing ≈40% of its initial mass. In addition, the osteopromotive properties of the novel hip implant is demonstrated as shown by an increased expression of osteonectin and osteocalcin by cultured human mesenchymal stem cells after 21 days. Overall, the proposed hip implant provides an innovative regenerative and mechanically stable solution for hip dysplasia treatment.

The Manufacture of Unbreakable Bionics via Multifunctional and Self-Healing Silk-Graphene Hydrogels.

Biomaterials capable of transmitting signals over longer distances than those in rigid electronics can open new opportunities for humanity by mimicking the way tissues propagate information. For seamless mirroring of the human body, they also have to display conformability to its curvilinear architecture, as well as, reproducing native-like mechanical and electrical properties combined with the ability to self-heal on demand like native organs and tissues. Along these lines, a multifunctional composite is developed by mixing silk fibroin and reduced graphene oxide. The material is coined "CareGum" and capitalizes on a phenolic glue to facilitate sacrificial and hierarchical hydrogen bonds. The hierarchal bonding scheme gives rise to high mechanical toughness, record-breaking elongation capacity of ≈25 000%, excellent conformability to arbitrary and complex surfaces, 3D printability, a tenfold increase in electrical conductivity, and a fourfold increase in Young's modulus compared to its pristine counterpart. By taking advantage of these unique properties, a durable and self-healing bionic glove is developed for hand gesture sensing and sign translation. Indeed, CareGum is a new advanced material with promising applications in fields like cyborganics, bionics, soft robotics, human-machine interfaces, 3D-printed electronics, and flexible bioelectronics.

Soft Electronic Materials with Combinatorial Properties Generated via Mussel-Inspired Chemistry and Halloysite Nanotube Reinforcement.

Soft and electrically active materials are currently being utilized for intelligent systems, including electronic skin, cybernetics, soft robotics, and wearable devices. However, fabricating materials that fulfill the complex requirements of such advanced applications remains a challenge. These attributes include electronic, adhesive, self-healing, flexible, moldable, printable, and strong mechanical properties. Inspired by the recent interest in transforming monofunctional materials into multifunctional ones through nanoreinforcement and mussel-inspired chemistry, we have designed a simple two-step methodology based on halloysite nanotube (HNT) and polydopamine (PDA) to address the grand challenges in the field. In brief, HNTs were coated with PDA and embedded within a poly(vinyl alcohol) (PVA)-based polymeric matrix in combination with ferric ions (Fe3+). The final composite displayed a 3-fold increase in electrical conductivity, a 20-fold increase in mechanical stiffness, and a 7-fold increase in energy dissipation in comparison to their nonfunctional counterparts, which arose from a combination of nanotube alignment and mussel-inspired chemistry. Moreover, the developed composite could elongate up to 30000% of its original length, maintain its electrical properties after 600% strain, self-heal within seconds (both electrically and mechanically), and display strain-sensitivity. Finally, it was 3D-printable and thus amenable for engineering of customized wearable electronics.

Oxygen releasing hydrogels for beta cell assisted therapy.

Diabetes is a serious chronic disease, which globally affects more than 400 million patients. Beta cell therapy has potential to serve as an effective cure to type 1 diabetes and several studies have already shown promising results in this regard. One of the major obstacles in cell therapy, however, is the hypoxic environment that therapeutic cells are subjected to immediately after the transplantation. In this study, a new approach is presented, based on hydrogels composed of thiolated hyaluronic acid (tHA), 8-arm-Poly(ethylene glycol)-Acrylate (PEGA), and calcium peroxide (CPO) as an oxygen releasing system. Hydrogels containing 0, 7.5, and 30% CPO were prepared, and the presence of CPO was confirmed via FTIR and Alizarin Red within the network. Oxygen release kinetics were monitored over time, and the results revealed that the hydrogels containing 30% CPO could release oxygen for at least 30 h. All three combinations were found to be injectable and suitable for beta cell therapy based on their mechanical and rheological properties. Additionally, to investigate the functionality of the system, insulin secreting INS-1E reporter cell clusters were encapsulated, and their viability was evaluated, which showed that CPO incorporation enhanced cell survival for at least three days.

Flexible and Green Electronics Manufactured by Origami Folding of Nanosilicate-Reinforced Cellulose Paper.

Today's consumer electronics are made from nonrenewable and toxic components. They are also rigid, bulky, and manufactured in an energy-inefficient manner via CO2-generating routes. Though petroleum-based polymers such as polyethylene terephthalate and polyethylene naphthalate can address the rigidity issue, they have a large carbon footprint and generate harmful waste. Scalable routes for manufacturing electronics that are both flexible and ecofriendly (Fleco) could address the challenges in the field. Ideally, such substrates must incorporate into electronics without compromising device performance. In this work, we demonstrate that a new type of wood-based [nanocellulose (NC)] material made via nanosilicate (NS) reinforcement can yield flexible electronics that can bend and roll without loss of electrical function. Specifically, the NSs interact electrostatically with NC to reinforce thermal and mechanical properties. For instance, films containing 34 wt % of NS displayed an increased young's modulus (1.5 times), thermal stability (290 → 310 °C), and a low coefficient of thermal expansion (40 ppm/K). These films can also easily be separated and renewed into new devices through simple and low-energy processes. Moreover, we used very cheap and environmentally friendly NC from American Value Added Pulping (AVAP) technology, American Process, and therefore, the manufacturing cost of our NS-reinforced NC paper is much cheaper ($0.016 per dm-2) than that of conventional NC-based substrates. Looking forward, the methodology highlighted herein is highly attractive as it can unlock the secrets of Fleco electronics and transform otherwise bulky, rigid, and "difficult-to-process" rigid circuits into more aesthetic and flexible ones while simultaneously bringing relief to an already-overburdened ecosystem.

Tough magnesium phosphate-based 3D-printed implants induce bone regeneration in an equine defect model.

One of the important challenges in bone tissue engineering is the development of biodegradable bone substitutes with appropriate mechanical and biological properties for the treatment of larger defects and those with complex shapes. Recently, magnesium phosphate (MgP) doped with biologically active ions like strontium (Sr2+) have shown to significantly enhance bone formation when compared with the standard calcium phosphate-based ceramics. However, such materials can hardly be shaped into large and complex geometries and more importantly lack the adequate mechanical properties for the treatment of load-bearing bone defects. In this study, we have fabricated bone implants through extrusion assisted three-dimensional (3D) printing of MgP ceramics modified with Sr2+ ions (MgPSr) and a medical-grade polycaprolactone (PCL) polymer phase. MgPSr with 30 wt% PCL (MgPSr-PCL30) allowed the printability of relevant size structures (>780 mm3) at room temperature with an interconnected macroporosity of approximately 40%. The printing resulted in implants with a compressive strength of 4.3 MPa, which were able to support up to 50 cycles of loading without plastic deformation. Notably, MgPSr-PCL30 scaffolds were able to promote in vitro bone formation in medium without the supplementation with osteo-inducing components. In addition, long-term in vivo performance of the 3D printed scaffolds was investigated in an equine tuber coxae model over 6 months. The micro-CT and histological analysis showed that implantation of MgPSr-PCL30 induced bone regeneration, while no bone formation was observed in the empty defects. Overall, the novel polymer-modified MgP ceramic material and extrusion-based 3D printing process presented here greatly improved the shape ability and load-bearing properties of MgP-based ceramics with simultaneous induction of new bone formation.

A self-healable, moldable and bioactive biomaterial gum for personalised and wearable drug delivery.

One of the long-standing challenges in materials science involves synthesizing biomaterials that recapitulate important features of native biological tissues. Even though, the number of available biomaterials at the moment are virtually limitless, few of them has unlocked all the secrets of the human body by mimicking the combinatorial-like material properties of our tissues and organs. Inspired by the human body, we have developed a polymeric gum, which combines stretchability, toughness, strength, flexibility, and self-healing. It also exhibits a high bioactivity that can target and eliminate bacterial infections fast and reliably. Notably, this material is moldable into almost any complex shape, and therefore suitable as a building block for wearables designed to conform directly with the curved and personalized anatomy of patients. It also exhibits excellent drug retention and release capacity, which altogether makes it suitable for applications in personalized wearable drug-delivery devices.

Sericin grafted multifunctional curcumin loaded fluorinated graphene oxide nanomedicines with charge switching properties for effective cancer cell targeting.

Fluorinated graphene has recently gained much attention for cancer drug delivery, owing to its peculiar properties including high electronegativity difference, magnetic resonance imaging contrast agent, and the photothermal effect. However, the hydrophobic nature of fluorinated graphene greatly hinders its application as a biological material. Herein, a novel green method is reported for synthesis of a pH-sensitive charge-reversal and water-soluble fluorinated graphene oxide, modified with polyethyleneimine anchored to sericin-polypeptide (FPS). This nanocarrier was further loaded with curcumin (Cur), and characterized as a nanocarrier for anti-cancer drug delivery. The synthesized nanocarriers contain two different pH-sensitive amide linkages, which are negatively charged in blood pH (≈7.4) and can prolong circulation times. The amide linkages undergo hydrolysis once they reach the mildly acidic condition (pH≈6.5, corresponding to tumor extracellular matrix), and subsequently once reached the lower acidic condition (pH≈5.5, corresponded to endo/lysosomes microenvironment), the FPS charge can be switched to positive (≈+28 mV), which aids the nuclear release. This nanocarrier was designed to selectively enhance cell internalization and nuclear-targeted delivery of curcumin in HeLa, SkBr3 and PC-3 cancer cells. Moreover, FPS-Cur demonstrated high curcumin loading capacity, prolonged curcumin release and promotion of apoptosis in HeLa, SkBr3 and PC-3 cells. Therefore, with its pH-responsive charge-reversal properties, FPS-Cur would be a promising candidate for chemotherapy of cervical, breast and prostate cancers.

Self-Healing Hydrogels: The Next Paradigm Shift in Tissue Engineering?

Given their durability and long-term stability, self-healable hydrogels have, in the past few years, emerged as promising replacements for the many brittle hydrogels currently being used in preclinical or clinical trials. To this end, the incompatibility between hydrogel toughness and rapid self-healing remains unaddressed, and therefore most of the self-healable hydrogels still face serious challenges within the dynamic and mechanically demanding environment of human organs/tissues. Furthermore, depending on the target tissue, the self-healing hydrogels must comply with a wide range of properties including electrical, biological, and mechanical. Notably, the incorporation of nanomaterials into double-network hydrogels is showing great promise as a feasible way to generate self-healable hydrogels with the above-mentioned attributes. Here, the recent progress in the development of multifunctional and self-healable hydrogels for various tissue engineering applications is discussed in detail. Their potential applications within the rapidly expanding areas of bioelectronic hydrogels, cyborganics, and soft robotics are further highlighted.

Pectin Methacrylate (PEMA) and Gelatin-Based Hydrogels for Cell Delivery: Converting Waste Materials into Biomaterials.

The emergence of nontoxic, eco-friendly, and biocompatible polymers derived from natural sources has added a new and exciting dimension to the development of low-cost and scalable biomaterials for tissue engineering applications. Here, we have developed a mechanically strong and durable hydrogel composed of an eco-friendly biopolymer that exists within the cell walls of fruits and plants. Its trade name is pectin, and it bears many similarities with natural polysaccharides in the native extracellular matrix. Specifically, we have employed a new pathway to transform pectin into a ultraviolet (UV)-cross-linkable pectin methacrylate (PEMA) polymer. To endow this hydrogel matrix with cell differentiation and cell spreading properties, we have also incorporated thiolated gelatin into the system. Notably, we were able to fine-tune the compressive modulus of this hydrogel in the range ∼0.5 to ∼24 kPa: advantageously, our results demonstrated that the hydrogels can support growth and viability for a wide range of three-dimensionally (3D) encapsulated cells that include muscle progenitor (C2C12), neural progenitor (PC12), and human mesenchymal stem cells (hMSCs). Our results also indicate that PEMA-gelatin-encapsulated hMSCs can facilitate the formation of bonelike apatite after 5 weeks in culture. Finally, we have demonstrated that PEMA-gelatin can yield micropatterned cell-laden 3D constructs through UV light-assisted lithography. The simplicity, scalability, processability, tunability, bioactivity, and low-cost features of this new hydrogel system highlight its potential as a stem cell carrier that is capable of bridging the gap between clinic and laboratory.

A Protein-Based, Water-Insoluble, and Bendable Polymer with Ionic Conductivity: A Roadmap for Flexible and Green Electronics.

Proteins present an ecofriendly alternative to many of the synthetic components currently used in electronics. They can therefore in combination with flexibility and electroactivity uncover a range of new opportunities in the field of flexible and green electronics. In this study, silk-based ionic conductors are turned into stable thin films by embedding them with 2D nanoclay platelets. More specifically, this material is utilized to develop a flexible and ecofriendly motion-sensitive touchscreen device. The display-like sensor can readily transmit light, is easy to recycle and can monitor the motion of almost any part of the human body. It also displays a significantly lower sheet resistance during bending and stretching regimes than the values typically reported for conventional metallic-based conductors, and remains fully operational after mechanical endurance testing. Moreover, it can operate at high frequencies in the kilohertz (kHz) range under both normal and bending modes. Notably, our new technology is available through a simple one-step manufacturing technique and can therefore easily be extended to large-scale fabrication of electronic devices.

Combinatorial Screening of Nanoclay-Reinforced Hydrogels: A Glimpse of the "Holy Grail" in Orthopedic Stem Cell Therapy?

Despite the promise of hydrogel-based stem cell therapies in orthopedics, a significant need still exists for the development of injectable microenvironments capable of utilizing the  regenerative potential of donor cells. Indeed, the quest for biomaterials that can direct stem cells into bone without the need of external factors has been the "Holy Grail" in orthopedic stem cell therapy for decades. To address this challenge, we have utilized a combinatorial approach to screen over 63 nanoengineered hydrogels made from alginate, hyaluronic acid, and two-dimensional nanoclays. Out of these combinations, we have identified a biomaterial that can promote osteogenesis in the absence of well-established differentiation factors such as bone morphogenetic protein 2 (BMP2) or dexamethasone. Notably, in our "hit" formulations we observed a 36-fold increase in alkaline phosphate (ALP) activity and a 11-fold increase in the formation of mineralized matrix, compared to the control hydrogel. This induced osteogenesis was further supported by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy. Additionally, the Montmorillonite-reinforced hydrogels exhibited high osteointegration as evident from the relatively stronger adhesion to the bone explants as compared to the control. Overall, our results demonstrate the capability of combinatorial and nanoengineered biomaterials to induce bone regeneration through osteoinduction of stem cells in a natural and differentiation-factor-free environment.