Graphene Hybrid Tough Hydrogels with Nanostructures for Tissue Regeneration.

Over the past few decades, hydrogels have attracted considerable attention as promising biomedical materials. However, conventional hydrogels require improved mechanical properties, such as brittleness, which significantly limits their widespread use. Recently, hydrogels with remarkably improved toughness have been developed; however, their low biocompatibility must be addressed. In this study, we developed a tough graphene hybrid hydrogel with nanostructures. The resultant hydrogel exhibited remarkable mechanical properties while representing an aligned nanostructure that resembled the extracellular matrix of soft tissue. Owing to the synergistic effect of the topographical properties, and the enhanced biochemical properties, the graphene hybrid hydrogel had excellent stretchability, resilience, toughness, and biocompatibility. Furthermore, the hydrogel displayed outstanding tissue regeneration capabilities (e.g., skin and tendons). Overall, the proposed graphene hybrid tough hydrogel may provide significant insights into the application of tough hydrogels in tissue regeneration.

Piezoelectrically and Topographically Engineered Scaffolds for Accelerating Bone Regeneration.

Bone regeneration remains a critical concern across diverse medical disciplines, because it is a complex process that requires a combinatorial approach involving the integration of mechanical, electrical, and biological stimuli to emulate the native cellular microenvironment. In this context, piezoelectric scaffolds have attracted considerable interest owing to their remarkable ability to generate electric fields in response to dynamic forces. Nonetheless, the application of such scaffolds in bone tissue engineering has been limited by the lack of a scaffold that can simultaneously provide both the intricate electromechanical environment and the biocompatibility of the native bone tissue. Here, we present a pioneering biomimetic scaffold that combines the unique properties of piezoelectric and topographical enhancement with the inherent osteogenic abilities of hydroxyapatite (HAp). Notably, the novelty of this work lies in the incorporation of HAp into polyvinylidene fluoride-co-trifluoro ethylene in a freestanding form, leveraging its natural osteogenic potential within a piezoelectric framework. Through comprehensive in vitro and in vivo investigations, we demonstrate the remarkable potential of these scaffolds to accelerate bone regeneration. Moreover, we demonstrate and propose three pivotal mechanisms─(i) electrical, (ii) topographical, and (iii) paracrine─that collectively contribute to the facilitated bone healing process. Our findings present a synergistically derived biomimetic scaffold design with wide-ranging prospects for bone regeneration as well as various regenerative medicine applications.

Engineering Considerations on Large-Scale Cultured Meat Production.

In recent decades, cultured meat has received considerable interest as a sustainable alternative to traditional meat products, showing promise for addressing the inherent problems associated with conventional meat production. However, current limitations on the scalability of production and extremely high production costs have prevented their widespread adoption. Therefore, it is important to develop novel engineering strategies to overcome the current limitations in large-scale cultured meat production. Such engineering considerations have the potential for advancements in cultured meat production by providing innovative and effective solutions to the prevailing challenges. In this review, we discuss how engineering strategies have been utilized to advance cultured meat technology by categorizing the production processes of cultured meat into three distinct steps: (1) cell preparation; (2) cultured meat fabrication; and (3) cultured meat maturation. For each step, we provide a comprehensive discussion of the recent progress and its implications. In particular, we focused on the engineering considerations involved in each step of cultured meat production, with specific emphasis on large-scale production.

Transplantable stem cell nanobridge scaffolds for accelerating articular cartilage regeneration.

Microfracture technique for treating articular cartilage defects usually has poor clinical outcomes due to critical heterogeneity and extremely limited in quality. To improve the effects of current surgical technique (i.e., microfracture technique), we propose the transplantable stem cell nanobridge scaffold, acting as a protective bridge between host tissue and defected cartilage as well as microfracture-derived cells. Nanobridge scaffolds have a sophisticated nanoaligned structure with freestanding and flexible shapes for imposing direct structural guidance to cells including transplanted stem cells and host cells, and it can induce not only chondrocyte migration but also stem cell differentiation, maturation, and growth factor secretion. The transplantable stem cell nanobridge scaffold is capable of reconstructing the defected cartilage with homogeneous architecture and highly enhanced adhesive stress similar with native cartilage tissue by the synergistic effects of stem cells-based chondro-induction and nanotopography-based chondro-conduction. Our findings demonstrate a significant advancement in the traditional treatment technique by using a nanoengineered tool for achieving successful cartilage regeneration.

Engineering considerations of iPSC-based personalized medicine.

Personalized medicine aims to provide tailored medical treatment that considers the clinical, genetic, and environmental characteristics of patients. iPSCs have attracted considerable attention in the field of personalized medicine; however, the inherent limitations of iPSCs prevent their widespread use in clinical applications. That is, it would be important to develop notable engineering strategies to overcome the current limitations of iPSCs. Such engineering approaches could lead to significant advances in iPSC-based personalized therapy by offering innovative solutions to existing challenges, from iPSC preparation to clinical applications. In this review, we summarize how engineering strategies have been used to advance iPSC-based personalized medicine by categorizing the development process into three distinctive steps: 1) the production of therapeutic iPSCs; 2) engineering of therapeutic iPSCs; and 3) clinical applications of engineered iPSCs. Specifically, we focus on engineering strategies and their implications for each step in the development of iPSC-based personalized medicine.

Graphene Hybrid Inner Ear Organoid with Enhanced Maturity.

Inner ear organoids (IEOs) are 3D structures grown in vitro, which can mimic the complex cellular structure and function of the inner ear. IEOs are potential solutions to problems related to inner ear development, disease modeling, and drug delivery. However, current approaches in generating IEOs using chemical factors have a few limitations, resulting in unpredictable outcomes. In this study, we propose the use of nanomaterial-based approaches, specifically by using graphene oxide (GO). GO's unique properties promote cell-extracellular matrix interactions and cell-cell gap junctions, thereby enhancing hair cell formation, which is an essential part of IEO development. We also investigated the potential applications for drug testing. Our findings suggest that GO is a promising candidate for enhancing the functionality of IEOs and advancing our understanding of the problems underlying inner ear development. The use of nanomaterial-based approaches may provide a more reliable and effective method for building better IEOs in the future.

Tissue-engineered tendon nano-constructs for repair of chronic rotator cuff tears in large animal models.

Chronic rotator cuff tears (RCTs) are one of the most common injuries of shoulder pain. Despite the recent advances in surgical techniques and improved clinical outcomes of arthroscopically repaired rotator cuffs (RCs), complete functional recovery-without retear-of the RC tendon through tendon-to-bone interface (TBI) regeneration remains a key clinical goal to be achieved. Inspired by the highly organized nanostructured extracellular matrix in RC tendon tissue, we propose herein a tissue-engineered tendon nano-construct (TNC) for RC tendon regeneration. When compared with two currently used strategies (i.e., transosseous sutures and stem cell injections), our nano-construct facilitated more significant healing of all parts of the TBI (i.e., tendon, fibrocartilages, and bone) in both rabbit and pig RCT models owing to its enhancements in cell proliferation and differentiation, protein expression, and growth factor secretion. Overall, our findings demonstrate the high potential of this transplantable tendon nano-construct for clinical repair of chronic RCTs.

Eggshell membrane-incorporated cell friendly tough hydrogels with ultra-adhesive property.

Adhesive and tough hydrogels have received increased attention for their potential biomedical applications. However, traditional hydrogels have limited utility in tissue engineering because they tend to exhibit low biocompatibility, low adhesiveness, and poor mechanical properties. Herein, the use of the eggshell membrane (ESM) for developing tough, cell-friendly, and ultra-adhesive hydrogels is described. The ESM enhances the performance of the hydrogel network in three ways. First, its covalent cross-linking with the polyacrylamide and alginate chains strengthens the hydrogel network. Second, it provides functional groups, such as amine and carboxyl moieties, which are well known for enhancing the surface adhesion of biomaterials, thereby increasing the adhesiveness of the hydrogel. Third, it is a bioactive agent and improves cell adhesion and proliferation on the constructed scaffold. In conclusion, this study proposes the unique design of ESM-incorporated hydrogels with high toughness, cell-friendly, and ultra-adhesive properties for various biomedical engineering applications.

Therapeutic strategies of three-dimensional stem cell spheroids and organoids for tissue repair and regeneration.

Three-dimensional (3D) stem cell culture systems have attracted considerable attention as a way to better mimic the complex interactions between individual cells and the extracellular matrix (ECM) that occur in vivo. Moreover, 3D cell culture systems have unique properties that help guide specific functions, growth, and processes of stem cells (e.g., embryogenesis, morphogenesis, and organogenesis). Thus, 3D stem cell culture systems that mimic in vivo environments enable basic research about various tissues and organs. In this review, we focus on the advanced therapeutic applications of stem cell-based 3D culture systems generated using different engineering techniques. Specifically, we summarize the historical advancements of 3D cell culture systems and discuss the therapeutic applications of stem cell-based spheroids and organoids, including engineering techniques for tissue repair and regeneration.

Therapeutic Strategies and Enhanced Production of Stem Cell-Derived Exosomes for Tissue Regeneration.

Exosomes are nanovesicles surrounded by a plasma membrane and carry bioactive molecules (e.g., proteins, lipids, and nucleic acids) of the origin cell type. The bioactive molecules delivered by exosomes to the recipient cells have attracted considerable attention, as they play an important role in intercellular communication. Moreover, exosomes have unique properties, including the ability to penetrate the biological barrier with minimal immunogenicity and side effects, which can influence various physiological and pathological processes. Thus, exosomes are a promising therapeutic platform for various diseases (e.g., malignancies and allergies), as well as for the regeneration of damaged tissues. However, challenges of obtaining exosomes, such as complex extraction procedures, low yield, and difficulty in quantification are yet to be overcome, which limits the use of exosomes in clinical settings. In this review, we describe the state-of-the-art engineering techniques and strategies for highly efficient mass production of exosomes. Moreover, we discuss the functional aspects and potential therapeutic applications of stem cell-derived exosomes, and deliberate upon various engineering techniques and platform combinations for improved tissue regeneration by exosomes.

Engineering plants with carbon nanotubes: a sustainable agriculture approach.

Sustainable agriculture is an important conception to meet the growing food demand of the global population. The increased need for adequate and safe food, as well as the ongoing ecological destruction associated with conventional agriculture practices are key global challenges. Nanomaterials are being developed in the agriculture sector to improve the growth and protection of crops. Among the various engineered nanomaterials, carbon nanotubes (CNTs) are one of the most promising carbon-based nanomaterials owing to their attractive physiochemical properties such as small size, high surface area, and superior mechanical and thermal strength, offering better opportunities for agriculture sector applications. This review provides basic information about CNTs, including their history; classification; and electrical, thermal, and mechanical properties, with a focus on their applications in the agriculture field. Furthermore, the mechanisms of the uptake and translocation of CNTs in plants and their defense mechanisms against environmental stresses are discussed. Finally, the major shortcomings, threats, and challenges of CNTs are assessed to provide a broad and clear view of the potential and future directions for CNT-based agriculture applications to achieve the goal of sustainability.

Exogenous Cysteine Improves Mercury Uptake and Tolerance in Arabidopsis by Regulating the Expression of Heavy Metal Chelators and Antioxidative Enzymes.

Cysteine (Cys) is an essential amino acid component of the major heavy metal chelators, such as glutathione (GSH), metallothioneins (MTs), and phytochelatins (PCs), which are involved in the pathways of mercury (Hg) tolerance in plants. However, the mechanism through which Cys facilitates Hg tolerance in plants remains largely unclear. In this study, we investigated the effects of exogenous Cys on Hg uptake in the seedlings, roots, and shoots of Arabidopsis throughout 6 and 36 h of Hg exposure and on the regulation of Hg detoxification by heavy metal chelators and antioxidative enzymes. The results showed that exogenous Cys significantly improved Hg tolerance during the germination and seedling growth stages in Arabidopsis. Exogenous Cys significantly promoted Hg uptake in Arabidopsis roots by upregulating the expression of the Cys transporter gene AtLHT1, resulting in increased Hg accumulation in the roots and seedlings. In Arabidopsis seedlings, exogenous Cys further increased the Hg-induced glutathione synthase (GS1 and GS2) transcript levels, and the Hg and Hg + Cys treatments greatly upregulated MT3 expression after 36 h exposure. In the roots, MT3 was also significantly upregulated by treatment of 36 h of Hg or Hg + Cys. Notably, in the shoots, MT2a expression was rapidly induced (10-fold) in Hg presence and further markedly increased (20-fold) by exogenous Cys. Moreover, in the seedlings, exogenous Cys upregulated the transcripts of all superoxide dismutase (CuSOD1, CuSOD2, MnSOD1, FeSOD1, FeSOD2, and FeSOD3) within 6 h and subsequently increased the Hg-induced GR1 and GR2 transcript levels at 36 h, all of which could eliminate the promotion of reactive oxygen species production and cell damage caused by Hg. Additionally, exogenous Cys upregulated all the antioxidative genes rapidly in the roots and subsequently increased the expression of CuSOD1, CuSOD2, and MnSOD1 in the shoots. These results indicate that exogenous Cys regulates the transcript levels of heavy metal chelators and antioxidative enzymes differently in a time- and organ-specific manner under Hg stress. Taken together, our study elucidates the positive functional roles of exogenous Cys in the Hg uptake and tolerance mechanisms of Arabidopsis.

Biodegradable and Flexible Nanoporous Films for Design and Fabrication of Active Food Packaging Systems.

Nanotechnology has facilitated the development of active food packaging systems with functions that could not be achieved by their traditional counterparts. Such smart and active systems can improve the shelf life of perishable products and overcome major bottlenecks associated with the fabrication of safe and environmentally friendly food packaging systems. Herein, we used a plasma-enabled surface modification strategy to fabricate biodegradable and flexible nanoporous polycaprolactone-based (FNP) films for food packaging systems. Their capacity for preserving tomatoes, tangerines, and bananas at room and refrigeration temperatures was tested by analyzing various fruit parameters (mold generation, appearance changes, freshness, weight loss, firmness, and total soluble solids contents). Compared with commonly used polyethylene terephthalate-based containers, the proposed system enhanced the fruit storage quality (i.e., retained appearance, reduced weight loss, better firmness, and sugar contents) by controlling moisture evaporation and inhibiting mold generation. Thus, the FNP film represents a new active food packaging strategy.

A Freezing and Thawing Method for Fabrication of Small Gelatin Nanoparticles with Stable Size Distributions for Biomedical Applications.

BACKGROUND: Gelatin, a natural polymer, has a number of advantages as a material for fabricating nanoparticles, such as its hydrophilicity, biodegradability, nontoxicity, and biocompatibility, as well as low cost. Despite these various advantages, gelatin-based nanoparticles still have critical limitation for biomedical applications due to their relatively larger size than those of other materials. METHODS: In this study, a new strategy to design and fabricate small gelatin nanoparticles (GNPs) was proposed. The technique was based on the natural phenomenon where with decreasing temperature, the compression between the molecules of substances increases and the volume shrinks. RESULTS: The average size of the fabricated small GNPs was less than 100 nm and their gelatin properties (including non-cytotoxicity) were well maintained. The drug release profiles of the GNPs were confirmed, for which a simple mathematical model based on the conventional diffusion equation was proposed. There was a burst of drug release in the first 3 days, with different release profiles according to the concentration of model drugs loaded onto the GNPs. It was also demonstrated that the drug release profiles of the proposed mathematical model were consistent with the experimental results. CONCLUSION: Our work proposes that these small GNPs could be used as efficient drug and gene delivery and tissue engineering platforms for various biomedical applications.

Plasma-assisted multiscale topographic scaffolds for soft and hard tissue regeneration.

The design of transplantable scaffolds for tissue regeneration requires gaining precise control of topographical properties. Here, we propose a methodology to fabricate hierarchical multiscale scaffolds with controlled hydrophilic and hydrophobic properties by employing capillary force lithography in combination with plasma modification. Using our method, we fabricated biodegradable biomaterial (i.e., polycaprolactone (PCL))-based nitrogen gas (N-FN) and oxygen gas plasma-assisted flexible multiscale nanotopographic (O-FMN) patches with natural extracellular matrix-like hierarchical structures along with flexible and controlled hydrophilic properties. In response to multiscale nanotopographic and chemically modified surface cues, the proliferation and osteogenic mineralization of cells were significantly promoted. Furthermore, the O-FMN patch enhanced regeneration of the mineralized fibrocartilage tissue of the tendon-bone interface and the calvarial bone tissue in vivo in rat models. Overall, the PCL-based O-FMN patches could accelerate soft- and hard-tissue regeneration. Thus, our proposed methodology was confirmed as an efficient approach for the design and manipulation of scaffolds having a multiscale topography with controlled hydrophilic property.

Rebirth of the Eggshell Membrane as a Bioactive Nanoscaffold for Tissue Engineering.

Eggshell membrane (ESM)-based biomaterials have generated significant interest for their potential biomedical applications, including those in tissue engineering and regenerative medicine. Herein, the development of a bioactive ESM-based nanopatterned scaffold for enhancing the adhesion and functions of cells has been described. To control the shape of the raw ESM with entangled protein fibers, a two-step dissolution technique is used. Subsequently, nanoimprint lithography is applied to the ESM solution to fabricate scaffolds with a nanotopographic surface inspired by the fiber alignment of the extracellular matrix. In this way, the morphology and proliferation of attached osteoblasts are sensitively controlled through their response to the nanopatterned topography of the prepared scaffold, allowing significant improvements in their osteogenic differentiation and growth factor secretion. This study demonstrates the potential use of this bioactive ESM-based nanopatterned substrate as an effective cell and tissue engineering scaffold.

Radially patterned transplantable biodegradable scaffolds as topographically defined contact guidance platforms for accelerating bone regeneration.

BACKGROUND: The healing of large critical-sized bone defects remains a clinical challenge in modern orthopedic medicine. The current gold standard for treating critical-sized bone defects is autologous bone graft; however, it has critical limitations. Bone tissue engineering has been proposed as a viable alternative, not only for replacing the current standard treatment, but also for producing complete regeneration of bone tissue without complex surgical treatments or tissue transplantation. In this study, we proposed a transplantable radially patterned scaffold for bone regeneration that was defined by capillary force lithography technology using biodegradable polycaprolactone polymer. RESULTS: The radially patterned transplantable biodegradable scaffolds had a radial structure aligned in a central direction. The radially aligned pattern significantly promoted the recruitment of host cells and migration of osteoblasts into the defect site. Furthermore, the transplantable scaffolds promoted regeneration of critical-sized bone defects by inducing cell migration and differentiation. CONCLUSIONS: Our findings demonstrated that topographically defined radially patterned transplantable biodegradable scaffolds may have great potential for clinical application of bone tissue regeneration.

Eggshell membrane as a bioactive agent in polymeric nanotopographic scaffolds for enhanced bone regeneration.

A bone regeneration scaffold is typically designed as a platform to effectively heal a bone defect while preventing soft tissue infiltration. Despite the wide variety of scaffold materials currently available, such as collagen, critical problems in achieving bone regeneration remain, including a rapid absorption period and low tensile strength as well as high costs. Inspired by extracellular matrix protein and topographical cues, we developed a polycaprolactone-based scaffold for bone regeneration using a soluble eggshell membrane protein (SEP) coating and a nanotopography structure for enhancing the physical properties and bioactivity. The scaffold exhibited adequate flexibility and mechanical strength as a biomedical platform for bone regeneration. The highly aligned nanostructures and SEP coating were found to regulate and enhance cell morphology, adhesion, proliferation, and differentiation in vitro. In a calvaria bone defect mouse model, the scaffolds coated with SEP applied to the defect site promoted bone regeneration along the direction of the nanotopography in vivo. These findings demonstrate that bone-inspired nanostructures and SEP coatings have high potential to be applicable in the design and manipulation of scaffolds for bone regeneration.

Synergistic effects of gelatin and nanotopographical patterns on biomedical PCL patches for enhanced mechanical and adhesion properties.

Biomedical patches have been known as important biomaterial-based medical devices for the clinical treatment of tissue and organ diseases. Inspired by the extracellular matrix-like aligned nanotopographical pattern as well as the unique physical and biocompatible properties of gelatin, we developed strength-enhanced biomedical patches by coating gelatin onto the nanopatterned surface of polycaprolactone (PCL). The relative contributions of the nanotopographical pattern (physical factor) and gelatin coating (chemical factor) in enhancing the mechanical and adhesive properties of PCL were quantitatively investigated. The nanotopographical pattern increased the surface area of PCL, allowing more gelatin to be coated on its surface. The biomedical patch made from gelatin-coated nanopatterned PCL showed strong mechanical and adhesive properties (tensile strength: ~14.5 MPa; Young's modulus: ~60.2 MPa; and normal and shear adhesive forces: ~1.81 N/cm2 and ~352.3 kPa) as well as good biocompatibility. Although the nanotopographical pattern or gelatin coating alone could enhance these physical properties of PCL in both dry and wet environmental conditions, both factors in combination further strengthened the properties, indicating the importance of synergistic cues in driving the mechanical behavior of biomedical materials. This strength-enhanced biomedical patch will be especially useful for the treatment of tissues such as cartilage, tendon, and bone.

Tendon-Inspired Nanotopographic Scaffold for Tissue Regeneration in Rotator Cuff Injuries.

Acute and chronic rotator cuff (RC) tears are common etiologies of shoulder disabilities. Despite the advanced surgical techniques and graft materials available for tendon repair, the high re-tear rate remains a critical challenge in RC healing. Inspired by the highly organized nanotopography of the extracellular matrix (ECM) in tendon tissue of the shoulder, nanotopographic scaffolds are developed using polycaprolactone for the repair and regeneration of RC tendons. The scaffolds show appropriate flexibility and mechanical properties for application in tendon tissue regeneration. It is found that the highly aligned nanotopographic cues of scaffolds could sensitively control and improve the morphology, attachment, proliferation, and differentiation of tendon-derived cells as well as promote their wound healing capacity in vitro. In particular, this study showed that the scaffolds could promote tendon regeneration along the direction of the nanotopography in the rabbit models of acute and chronic RC tears. Nanotopographic scaffold-augmented rotator cuff repair showed a more appropriate healing pattern compared to the control groups in a rabbit RC tear model. We demonstrated that the tendon ECM-like nanoscale structural cues of the tendon-inspired patch may induce the more aligned tissue regeneration of the underlying tissues including tendon-to-bone interface.