Biomaterials for tissue engineering

From hard tissues to beyond: Progress and challenges of strontium-containing biomaterials in regenerative medicine applications

Tissue engineering and regenerative medicine have emerged as crucial disciplines focused on the development of new tissues and organs to overcome the limitations of traditional treatments for tissue damage caused by accidents, diseases, or aging. Strontium ion (Sr2+) has garnered significant attention for its multifaceted role in promoting regeneration medicine and therapy, especially in bone tissue regeneration. Recently, numerous studies further confirm that Sr2+ also plays a critical in soft tissue regeneration. This review firstly summarizes the influence of Sr2+ on critical biological processes such as osteogenesis, angiogenesis, immune modulation, matrix synthesis, mineralization, and antioxidative defence mechanisms. Then details the classification, properties, advantages, and limitations of Sr-containing biomaterials (SrBMs). Additionally, this review extends to the current applications of SrBMs in regenerative medicine for diverse tissues, including bone, cartilage, skeletal muscle, dental pulp, cardiac tissue, skin, hair follicles, etc. Moreover, the review addresses the challenges associated with current SrBMs and provides insights for their future designing and applications in regenerative medicine.

Advanced collagen-based scaffolds for cartilage and osteochondral regeneration: A review

Osteoarthritis (OA), a prevalent degenerative joint disease, presents a formidable challenge to human health due to its complex pathophysiology. Despite various clinical treatments, a definitive cure for OA remains elusive, leaving patients with only symptomatic relief. Tissue engineering has emerged as a promising approach for OA treatment, offering the potential to restore damaged cartilage and osteochondral tissues. Collagen-based scaffolds, renowned for their superior biocompatibility and bioactivity, hold significant potential in promoting effective cartilage and osteochondral regeneration. Over the past decades, substantial progress has been made in the design and clinical translation of collagen-based scaffolds for cartilage and osteochondral tissue engineering. However, no comprehensive review has yet addressed the application of collagen scaffold materials for OA treatment. This review highlights the advanced fabrication of collagen-based scaffolds, including porous matrices, hydrogels, and microspheres, and their integration with cells, growth factors, and pharmaceuticals for OA therapy. Additionally, it examines the clinical translation of collagen-integrated constructs for managing OA. With continued innovation, collagen-enriched scaffolds are expected to play a pivotal role in improving outcomes for OA patients.

Poly(propylene fumarate) Composite Scaffolds for Bone Tissue Engineering: Innovation in Fabrication Techniques and Artificial Intelligence Integration

Over the past three decades, the biodegradable polymer known as poly(propylene fumarate) (PPF) has been the subject of numerous research due to its unique properties. Its biocompatibility and controllable mechanical properties have encouraged numerous scientists to manufacture and produce a wide range of PPF-based materials for biomedical purposes. Additionally, the ability to tailor the degradation rate of the scaffold material to match the rate of new bone tissue formation is particularly relevant in bone tissue engineering, where synchronized degradation and tissue regeneration are critical for effective healing. This review thoroughly summarizes the advancements in different approaches for PPF and PPF-based composite scaffold preparation for bone tissue engineering. Additionally, the challenges faced by each approach, such as biocompatibility, degradation, mechanical features, and crosslinking, were emphasized, and the noteworthy benefits of the most pertinent synthesis strategies were highlighted. Furthermore, the synergistic outcome between tissue engineering and artificial intelligence (AI) was addressed, along with the advantages brought by the implication of machine learning (ML) as well as the revolutionary impact on regenerative medicines. Future advances in bone tissue engineering could be facilitated by the enormous potential for individualized and successful regenerative treatments that arise from the combination of tissue engineering and artificial intelligence. By assessing a patient's reaction to a certain drug and choosing the best course of action depending on the patient's genetic and clinical characteristics, AI can also assist in the treatment of illnesses. AI is also used in drug research and discovery, target identification, clinical trial design, and predicting the safety and effectiveness of novel medications. Still, there are ethical issues including data protection and the requirement for reliable data management systems. AI adoption in the healthcare sector is expensive, involving staff and facility investments as well as training healthcare professionals on its application.

Advancements in Regenerative Therapies for Orthopedics: A Comprehensive Review of Platelet-Rich Plasma, Mesenchymal Stem Cells, Peptide Therapies, and Biomimetic Applications

Background/Objectives: Regenerative therapies have gained interest in orthopedic applications for their potential to enhance tissue regeneration, functional recovery, and pain modification. This review evaluates the clinical efficacy of platelet-rich plasma (PRP), mesenchymal stem cells (MSCs), peptide-based treatments, and biomimetic materials in orthopedic care, with a focus on pain reduction and functional outcomes. Methods: A structured literature search in PubMed (January 2009-January 2025) identified 160 studies. After applying inclusion criteria prioritizing randomized controlled trials (RCTs) and clinical trials, 59 studies were included: 20 on PRP, 20 on MSCs, 10 on peptide therapies, and 7 on biomimetics. Data extraction focused on pain reduction and functional recovery, with risk of bias assessed using the Cochrane Risk of Bias (RoB) tool and ROBINS-I tool. A random-effects meta-regression analysis was conducted to evaluate the impact of therapy type, sample size, and risk of bias on reported pain reduction outcomes. Results: Meta-regression analysis identified MSC therapy as the most effective intervention for pain reduction (β = 8.45, p < 0.05), with PRP and peptide-based therapies showing moderate improvements, and biomimetic therapies demonstrating the lowest effect. PRP provided short-term pain relief, particularly in acute injuries and tendon repair, though inconsistencies in preparation methods limited success in chronic conditions. MSC therapies demonstrated cartilage regeneration and early osteoarthritis improvement, but high costs and ethical concerns remain barriers to widespread adoption. Peptide-based therapies and biomimetic materials, including engineered scaffolds and autologous protein solutions, showed promise for infection control and wound healing, though further research is needed to optimize dosing, delivery methods, and long-term safety. Conclusions: Regenerative therapies offer significant potential in orthopedic care, with MSC therapies demonstrating the most reliable regenerative effects, PRP providing short-term symptomatic relief, and peptide-based and biomimetic treatments emerging as promising adjuncts. However, standardized protocols and large-scale clinical trials are needed to establish long-term efficacy and improve clinical translation for broader adoption.

Sustainable Nonwoven Scaffolds Engineered with Recycled Carbon Fiber for Enhanced Biocompatibility and Cell Interaction: From Waste to Health

Carbon fibers, driven by ever-increasing demand, are contributing to a continuous rise in the generation of waste and byproducts destined for landfills or incineration. Recycling carbon fibers presents a promising strategy for reducing carbon emissions and conserving resources, thus contributing to more sustainable waste management practices. Discovering applications of recycled carbon fibers (rCFs) would inevitably accelerate the targeted integration of sustainable materials, fostering a circular economy. Herein, we have engineered rCF-based needlepunched nonwoven scaffolds and their blends with polypropylene (PP) fibers, providing the first example of investigating their interactions with human lung epithelial cells (Calu-3) and murine fibroblast cells (NIH/3T3). To promote the adsorption of extracellular matrix proteins such as laminin, these three-dimensional (3D) nonwoven scaffolds are designed and developed to feature tunable porous characteristics and wetting properties. Although cell adhesion and laminin adsorption are minimal on PP fibers, cells are preferentially organized on the rCFs. These nonwovens, composed exclusively of rCFs or their blends with PP fibers, exhibit no cytotoxic effects, with both cell types showing proliferation on the scaffolds and a progressive increase in cell numbers over time. Cell viability and apoptosis assays are also employed to comprehensively evaluate biocompatibility. Thus, our study proves rCF-based nonwoven scaffolds as potential candidates for artificial lung tissue scaffolds.

Using Three-Dimensional Bioprinting to Generate Realistic Models of Wound Healing

Significance: The skin serves as the primary defense against external stimuli, making it vulnerable to damage. Injuries can cause a dysregulated environment, resulting in chronic inflammation and inhibition of cell proliferation and migration, which delays recovery. Innovative approaches, such as three-dimensional (3D) bioprinting, can foster a controlled healing environment by promoting synergy between the skin microbiome and cells. Recent Advances: Traditional approaches to wound healing have focused on fostering an environment conducive to the interplay between cells, extracellular proteins, and growth factors. 3D bioprinting, a manufacturing technology with applications in tissue engineering, deposits biomaterial-based bioink containing living cells to fabricate custom-designed tissue scaffolds in a layer-by-layer fashion. This process controls the architecture and composition of a construct, producing multilayered and complex structures such as skin. Critical Issues: The selection of biomaterials for scaffolds has been a challenge when 3D skin tissue engineering. While prioritizing mechanical properties, current biomaterials often lack the ability to interact with environmental stimuli such as pH, temperature, or oxygen levels. Employing smart biomaterials that integrate bioactive molecules and adapt to external conditions could overcome these limitations. This innovation would enable scaffolds to create a sustainable wound-healing environment, fostering microbiome balance, reducing inflammation, and facilitating cellular recovery and tissue restoration, addressing critical gaps in existing wound care solutions. Future Directions: Novel bioink formulations for skin injury recovery are focused on improving long-term cell viability, proliferation, vascularization, and immune integration. Efficient recovery of the skin microbiome using bioactive molecules has the potential to create microenriched environments that support the recovery of the skin microbiome and restore immune regulation. This promising direction for future research aims to improve patient outcomes in wound care.

Sustainable biofabrication: from bioprinting to AI-driven predictive methods

Biofabrication is potentially an inherently sustainable manufacturing process of bio-hybrid systems based on biomaterials embedded with cell communities. These bio-hybrids promise to augment the sustainability of various human activities, ranging from tissue engineering and robotics to civil engineering and ecology. However, as routine biofabrication practices are laborious and energetically disadvantageous, our society must refine production and validation processes in biomanufacturing. This opinion highlights the research trends in sustainable material selection and biofabrication techniques. By modeling complex biosystems, the computational prediction will allow biofabrication to shift from an error-trial method to an efficient, target-optimized approach with minimized resource and energy consumption. We envision that implementing bionomic rationality in biofabrication will render bio-hybrid products fruitful for greening human activities.

Material and technique fundamentals of nano-hydroxyapatite coatings towards biofunctionalization: a review

Hydroxyapatite (HAp) nanocoatings on titanium alloys (e.g. Ti6Al4V) have been used for prosthetic orthopaedic implants in recent decades because of their osseointegration, bioactivity, and biocompatibility. HAp is brittle with low mechanical strength and poor adhesion to metallic surfaces, which limits its durability and bioactivity. Surface modification techniques have alleviated the imperfections in biomaterials by coating the substrate. Several methods for improving the characteristics of implants, such as physical vapour deposition, the thermal spray method, the sol-gel method, microarc oxidation, and electrochemical deposition methods, have been discussed in this review. These processes provide mechanical strength without sacrificing biocompatibility and may lead to the development of new ideas for future research. This review discusses various selective additives, including carbon allotropes, ceramic materials, metallic materials, and multiple materials, to enhance tribological characteristics, biocompatibility, wear resistance, and mechanical strength. This review focuses on the fabrication of nano-HAps as coatings using selective deposition methods with controlled deposition parameters, paying special attention to recent developments in bone tissue engineering. This report is organized in such a way that it may inspire further research on surface modifications during medical treatment. The present review may help prospective investigators understand the importance of surface modifications for obtaining excellent implantation performance.

Stem Cell-Laden Engineered Patch: Advances and Applications in Tissue Regeneration

Stem cell-based therapies are emerging as significant approaches in tissue engineering and regenerative medicine, applicable to both fundamental scientific research and clinical practice. Despite remarkable results in clinical studies, challenges such as poor standardization of graft tissues, limited sources, and reduced functionality have hindered the effectiveness of these therapies. In this review, we summarize the engineering approaches involved in fabricating stem cell assisted patches and the substantial strategies for designing stem cell-laden engineered patches (SCP) to complement the existing stem cell-based therapies. We then outline the potential applications of SCP in advancing tissue regeneration and regenerative medicine. By combining living stem cells with engineered patches, SCP can enhance the functions of both components, particularly for tissue engineering applications. Finally, we addressed current challenges, such as ethical considerations, high costs, and regulatory hurdles and proposed future research directions to overcome these barriers.

Cavalcante R, Ge C, Franceschi RT, Ma PX. Synthetic helical peptides on nanofibers to activate cell-surface receptors and synergistically enhance critical-sized bone defect regeneration

More than 500,000 bone grafting procedures are performed annually in the USA. Considering the significant limitations of available bone grafts, we previously invented a phase-separation technology to generate nanofibrous poly(l-lactic acid) (PLLA) scaffolds that mimic the bone matrix collagen in nanofiber geometry and enhance bone regeneration. Here we report the development of nanofibrous scaffolds with covalently attached synthetic peptides that mimic native collagen peptides to activate the two main collagen receptors in bone cells, discoidin domain receptor 2 (DDR2) and β1 integrins. We synthesized a PLLA-based graft-copolymer to enable covalent peptide conjugation via a click reaction. Using PLLA and the graft-copolymer, we developed 3D scaffolds with interconnected pores and peptides-containing nanofibers to activate DDR2 and β1 integrins of osteogenic cells. The degradation rate and mechanical properties of the scaffolds are tunable. The peptides-decorated nanofibrous scaffolds demonstrated 7.8 times more mineralized bone regeneration over the control scaffolds without the peptides in a critical-sized bone defect regeneration model after 8 weeks of implantation, showing a synergistic effect of the two peptides. This study demonstrates the power of scaffolds to mimic ECM at both nanometer and molecular levels, activating cell surface receptors to liberate the innate regenerative potential of host stem/progenitor cells.

Advances in tissue engineering of peripheral nerve and tissue innervation - a systematic review

Although various options are available to treat injured organs and peripheral nerves, none is without limitations. Auto- and allografts are the first choice of treatment, but tissue survival or functionality is not guaranteed due to often limited vascular and neural networks. In response, tissue-engineered solutions have been developed, yet clinical translations is rare. In this study, a systematic review was performed on tissue-engineered advancements for peripheral nerves and tissues, to aid future developments in bridging the gap toward the clinic by identifying high-potential solutions and unexplored areas. A systematic search was performed in PubMed, Embase, Web of Science, and Scopus until November 9, 2023. Search terms involved "tissue engineering," "guided," "tissue scaffold," and "tissue graft," together with "innervation" and "reinnervation." Original in vivo or in vitro studies meeting the inclusion criteria (tissue-engineered peripheral nerve/innervation of tissue) and no exclusion criteria (no full text available; written in foreign language; nonoriginal article; tissue-engineering of central nervous system; publication before 2012; insufficient study quality or reproducibility) were assessed. A total of 68 out of 3626 original studies were included. Data extraction was based on disease model, cell origin and host species, biomaterial nature and composition, and external stimuli of biological, chemical or physical origin. Although tissue engineering is still in its infancy, explored innervation strategies of today were highlighted with respect to biomaterials, cell types, and external stimuli. The findings emphasize that natural biomaterials, pre-seeding with autologous cell sources, and solutions for reproductive organs are beneficial for future research. Natural biomaterials possess important cues required for cell-material interaction and closely resemble native tissue in terms of biomechanical, geometrical and chemical composition. Autologous cells induce biomaterial functionalization. As these solutions pose no risk of immunorejection and have demonstrated good outcomes, they are most likely to fulfill the clinical demands.

Hijacking plant skeletons for biomedical applications: from regenerative medicine and drug delivery to biosensing

The field of biomedical engineering continually seeks innovative technologies to address complex healthcare challenges, ranging from tissue regeneration to drug delivery and biosensing. Plant skeletons offer promising opportunities for these applications due to their unique hierarchical structures, desirable porosity, inherent biocompatibility, and adjustable mechanical properties. This review comprehensively discusses chemical principles underlying the utilization of plant-based scaffolds in biomedical engineering. Highlighting their structural integrity, tunable properties, and possibility of chemical modification, the review explores diverse preparation strategies to tailor plant skeleton properties for bone, neural, cardiovascular, skeletal muscle, and tendon tissue engineering. Such applications stem from the cellulosic three-dimensional structure of different parts of plants, which can mimic the complexity of native tissues and extracellular matrices, providing an ideal environment for cell adhesion, proliferation, and differentiation. We also discuss the application of plant skeletons as carriers for drug delivery due to their structural diversity and versatility in encapsulating and releasing therapeutic agents with controlled kinetics. Furthermore, we present the emerging role played by plant-derived materials in biosensor development for diagnostic and monitoring purposes. Challenges and future directions in the field are also discussed, offering insights into the opportunities for future translation of sustainable plant-based technologies to address critical healthcare needs.

Advances of naturally derived biomedical polymers in tissue engineering

The extensive utilization of natural polymers in tissue engineering is attributed to their excellent biocompatibility, degradability, and resemblance to the natural extracellular matrix. These polymers have a wide range of applications such as delivering therapeutic medicine, detecting diseases, sensing biological substances, promoting tissue regeneration, and treating diseases. This is a brief review of current developments in the properties and uses of widely used biomedical polymers derived from nature. Additionally, it explores the correlation between the characteristics and functions of these materials in different biomedical applications and highlights the prospective direction for the advancement of natural polymer materials in tissue engineering.

Tumor-microenvironment-on-a-chip: the construction and application

Currently, despite the vast amounts of time and money invested in cancer treatment, cancer remains one of the primary threats to human life. The primary factor contributing to the low treatment efficacy is cancer heterogeneity. The unclear molecular mechanisms underlying tumorigenesis, coupled with the complexity of human physiology, and the inability of animal models to accurately replicate the human tumor microenvironment, pose significant hurdles in the development of novel cancer therapies. Tumor-microenvironment-on-chip (TMOC) represents a research platform that integrates three-dimensional cell culture with microfluidic systems, simulating the essential components and physiological traits of the in vivo tumor microenvironment. It offers a dynamic setting within the chip system to study tumor progression, potentially heralding a breakthrough in cancer research. In this review, we will summarize the current advancements in this platform, encompassing various types of TMOCs and their applications in different types of cancer. From our perspective, the TMOC platform necessitates enhanced integration with tissue engineering techniques and microphysiological environments before it can evolve into a more refined preclinical model for cancer research.

Shape memory cycle conditions impact human bone marrow stromal cell binding to RGD- and YIGSR-conjugated poly (glycerol dodecanedioate)

Bioresorbable shape memory polymers (SMP) are an emerging class of polymers that can help address several challenges associated with minimally invasive surgery by providing a solution for structural tissue repair. Like most synthetic polymer networks, SMPs require additional biorelevance and modification for biomedical applications. Methodologies used to incorporate bioactive ligands must preserve SMP thermomechanics and ensure biofunctionality following in vivo delivery. We have previously described the development of a novel thermoresponsive bioresorbable SMP, poly (glycerol dodecanedioate) (PGD). In this study, cell-adhesive peptide sequences RGD and YIGSR were conjugated with PGD. We investigated 1) the impact of conjugated peptides on the fixity (Rf), recovery (Rr), and recovery rate (dRr/dT), 2) the impact of conjugated peptides on cell binding, and 3) the impact of the shape memory cycle (Tprog) on conjugated peptide functionality towards binding human bone marrow stromal cells (BMSC). Peptide conjugation conditions impact fixity but not the recovery or recovery rate (p < 0.01). Peptide-conjugated substrates increased cell attachment and proliferation compared with controls (p < 0.001). Using complementary integrin binding cell-adhesive peptides increased proliferation compared with using single peptides (p < 0.05). Peptides bound to PGD substrates exhibited specificity to their respective integrin targets. Following the shape memory cycle, peptides maintained functionality and specificity depending on the shape memory cycle conditions (p < 0.001). The dissipation of strain energy during recovery can drive differential arrangement of conjugated sequences impacting functionality, an important design consideration for functionalized SMPs. STATEMENT OF SIGNIFICANCE: Shape memory elastomers are an emerging class of polymers that are well-suited for minimally invasive repair of soft tissues. Tissue engineering approaches commonly utilize biodegradable scaffolds to deliver instructive cues, including cells and bioactive signals. Delivering these instructive cues on biodegradable shape memory elastomers requires modification with bioactive ligands. Furthermore, it is necessary to ensure the specificity of the ligands to their biological targets when conjugated to the polymer. Moreover, the bioactive ligand functionality must be conserved after completing the shape memory cycle, for applications in tissue engineering.

Surface-Conjugated Galactose on Electrospun Polycaprolactone Nanofibers: An Innovative Scaffold for Uterine Tissue Engineering

The uterus, a vital organ in the female reproductive system, nurtures and supports developing embryos until maturity. This study focuses on addressing uterine related problems by creating a nanofibrous scaffold to regenerate uterine myometrial tissue, closely resembling the native extracellular matrix (ECM) for enhanced efficacy. To achieve this, we utilized polycaprolactone (PCL) as a biomaterial and employed an electrospinning technique to generate PCL nanofibers in both random and aligned orientations. Due to the inherent hydrophobic nature of PCL nanofibers, a two-step wet chemistry surface modification technique is used, involving the conjugation of galactose onto them. Galactose, a lectin-binding sugar, was chosen to enhance the scaffold's hydrophilicity, thereby improving cell adhesion and fostering l-selectin-based interactions between the scaffold and uterine cells. These interactions, in turn, activated uterine fibroblasts, leading to ECM remodeling. The optimized electrospinning process successfully generated random and aligned nanofibers. Subsequent surface modification was carried out, and the modified scaffold was subjected to various physicochemical characterization, such as the ninhydrin assay, enzyme-linked lectin assay techniques that revealed successful galactose conjugation, and mechanical characterization to assess any changes in material bulk properties resulting from the modification. The tensile strength of random galactose-modified PCL fibers reached 0.041 ± 0.01 MPa, outperforming random unmodified PCL fibers (0.026 ± 0.01 MPa), aligned unmodified PCL fibers (0.011 ± 0.001 MPa), and aligned modified PCL fibers (0.016 ± 0.002 MPa). Cytocompatibility studies with human uterine fibroblast cells showed enhanced viability and proliferation on the modified scaffolds. Initial pilot studies were attempted in the current study involving subcutaneous implantation in the dorsal area of Wistar rats to assess biocompatibility and tissue response before proceeding to intrauterine implantation indicated that the modification did not induce adverse inflammation in vivo. In conclusion, our study introduces a surface-modified PCL nanofibrous material for myometrial tissue engineering, offering promise in addressing myometrial damage and advancing uterine health and reproductive well-being.

Emerging 2D Nanomaterials-Integrated Hydrogels: Advancements in Designing Theragenerative Materials for Bone Regeneration and Disease Therapy

This review highlights recent advancements in the synthesis, processing, properties, and applications of 2D-material integrated hydrogels, with a focus on their performance in bone-related applications. Various synthesis methods and types of 2D nanomaterials, including graphene, graphene oxide, transition metal dichalcogenides, black phosphorus, and MXene are discussed, along with strategies for their incorporation into hydrogel matrices. These composite hydrogels exhibit tunable mechanical properties, high surface area, strong near-infrared (NIR) photon absorption and controlled release capabilities, making them suitable for a range of regeneration and therapeutic applications. In cancer therapy, 2D-material-based hydrogels show promise for photothermal and photodynamic therapies, and drug delivery (chemotherapy). The photothermal properties of these materials enable selective tumor ablation upon NIR irradiation, while their high drug-loading capacity facilitates targeted and controlled release of chemotherapeutic agents. Additionally, 2D-materials -infused hydrogels exhibit potent antibacterial activity, making them effective against multidrug-resistant infections and disruption of biofilm generated on implant surface. Moreover, their synergistic therapy approach combines multiple treatment modalities such as photothermal, chemo, and immunotherapy to enhance therapeutic outcomes. In bio-imaging, these materials serve as versatile contrast agents and imaging probes, enabling their real-time monitoring during tumor imaging. Furthermore, in bone regeneration, most 2D-materials incorporated hydrogels promote osteogenesis and tissue regeneration, offering potential solutions for bone defects repair. Overall, the integration of 2D materials into hydrogels presents a promising platform for developing multifunctional theragenerative biomaterials.

Challenges and Pitfalls of Research Designs Involving Magnesium-Based Biomaterials: An Overview

Magnesium-based biomaterials hold remarkable promise for various clinical applications, offering advantages such as reduced stress-shielding and enhanced bone strengthening and vascular remodeling compared to traditional materials. However, ensuring the quality of preclinical research is crucial for the development of these implants. To achieve implant success, an understanding of the cellular responses post-implantation, proper model selection, and good study design are crucial. There are several challenges to reaching a safe and effective translation of laboratory findings into clinical practice. The utilization of Mg-based biomedical devices eliminates the need for biomaterial removal surgery post-healing and mitigates adverse effects associated with permanent biomaterial implantation. However, the high corrosion rate of Mg-based implants poses challenges such as unexpected degradation, structural failure, hydrogen evolution, alkalization, and cytotoxicity. The biocompatibility and degradability of materials based on magnesium have been studied by many researchers in vitro; however, evaluations addressing the impact of the material in vivo still need to be improved. Several animal models, including rats, rabbits, dogs, and pigs, have been explored to assess the potential of magnesium-based materials. Moreover, strategies such as alloying and coating have been identified to enhance the degradation rate of magnesium-based materials in vivo to transform these challenges into opportunities. This review aims to explore the utilization of Mg implants across various biomedical applications within cellular (in vitro) and animal (in vivo) models.

Unveiling the potential of biomaterials and their synergistic fusion in tissue engineering

Inspired by nature, tissue engineering aims to employ intricate mechanisms for advanced clinical interventions, unlocking inherent biological potential and propelling medical breakthroughs. Therefore, medical, and pharmaceutical fields are growing interest in tissue and organ replacement, repair, and regeneration by this technology. Three primary mechanisms are currently used in tissue engineering: transplantation of cells (I), injection of growth factors (II) and cellular seeding in scaffolds (III). However, to develop scaffolds presenting highest potential, reinforcement with polymeric materials is growing interest. For instance, natural and synthetic polymers can be used. Regardless, chitosan and keratin are two biopolymers presenting great biocompatibility, biodegradability and non-antigenic properties for tissue engineering purposes offering restoration and revitalization. Therefore, combination of chitosan and keratin has been studied and results exhibit highly porous scaffolds providing optimal environment for tissue cultivation. This review aims to give an historical as well as current overview of tissue engineering, presenting mechanisms used and polymers involved in the field.

Thermodynamic Analysis of Silk Fibroin-Graphite Hybrid Materials and Their Morphology

Silk fibroin (SF) is a β-sheet-rich protein that is responsible for the remarkable tensile strength of silk. In addition to its mechanical properties, SF is biocompatible and biodegradable, making it an attractive candidate for use in biotic/abiotic hybrid materials. A pairing of particular interest is the use of SF with graphene-based nanomaterials (GBNs). The properties of this interface drive the formation of well-ordered nanostructures and can improve the electronic properties of the resulting hybrid. It was previously demonstrated that SF can form lamellar nanostructures in the presence of graphite; however, the equilibrium morphology and associated driving interactions are not fully understood. In this study, we characterize these interactions between SF and SF lamellar with graphite using molecular dynamics (MD) simulations and umbrella sampling (US). We find that SF lamellar nanostructures have strong orientational and spatial preferences on graphite that are driven by the hydrophobic effect, destabilizing solvent-protein interactions and stabilizing protein-protein and protein-graphite interactions. Finally, we show how careful consideration of these underlying interactions can be applied to rationally modify the nanostructure morphology.

Progress in cardiac tissue engineering and regeneration: Implications of gelatin-based hybrid scaffolds

Cardiovascular diseases, particularly myocardial infarction (MI), remain a leading cause of morbidity and mortality worldwide. Current treatments for MI, more palliative than curative, have limitations in reversing the disease completely. Tissue engineering (TE) has emerged as a promising strategy to address this challenge and may lead to improved therapeutic approaches for MI. Gelatin-based scaffolds, including gelatin and its derivative, gelatin methacrylate (GelMA), have attracted significant attention in cardiac tissue engineering (CTE) due to their optimal physical and biochemical properties and capacity to mimic the native extracellular matrix (ECM). CTE mainly recruits two classes of gelatin/GelMA-based scaffolds: hydrogels and nanofibrous. This article reviews state-of-the-art gelatin/GelMA-based hybrid scaffolds currently applied for CTE and regenerative therapy. Hybrid scaffolds, fabricated by combining gelatin/GelMA hydrogel or nanofibrous scaffolds with other materials such as natural/synthetic polymers, nanoparticles, protein-based biomaterials, etc., are explored for enhanced cardiac tissue regeneration functionality. The engraftment of stem/cardiac cells, bioactive molecules, or drugs into these hybrid systems shows great promise in cardiac tissue repair and regeneration. Finally, the role of gelatin/GelMA scaffolds combined with the 3D bioprinting strategy in CTE will also be briefly highlighted.

Engineering a functional ACL reconstruction graft containing a triphasic enthesis-like structure in bone tunnel for the enhancement of graft-to-bone integration

Background

Anterior cruciate ligament (ACL) rupture is a common sports injury, which causes knee instability and abnormal joint kinematics. The current ACL graft was single-phasic, and not convenient for the formation of enthesis-like tissue in the bone tunnel, resulting in poor integration of graft-to-bone.

Methods

A band-shaped acellular tendon (BAT) was prepared as the core component of the ACL reconstruction graft at first, while sleeve-shaped acellular cartilage (SAC) or sleeve-shaped acellular bone (SAB) was fabricated using a vacuum aspiration system (VAS)-based decellularization protocol. The biocompatibility of the three acellular matrixes was evaluated. Furthermore, a collagen-binding peptide (CBP) derived from the A3 domain of von Willebrand factor was respectively fused into the N-terminal of GDF7, TGFβ3, or BMP2 to synthesize three recombinant growth factors capable of binding collagen (named C-GDF7, C-TGFβ3, or C-BMP2), which were respectively tethered to the BAT, SAC or SAB for improving their inducibilities in stem cell differentiation. An in-vitro experiment was performed to evaluate theirs osteogenic, chondrogenic, and tenogenic inducibilities. Then, C-TGFβ3-tethering SAC (C-TGFβ3@SAC) and C-BMP2-tethering SAB (C-BMP2@SAB) were sequentially surrounded at the bone tunnel part of C-GDF7-tethering BAT (C-GDF7@BAT), thus a sleeve-shaped acellular graft with a triphasic enthesis-like structure in bone tunnel part (named tissue-engineered graft, TE graft) was engineered. Lastly, a canine ACL reconstruction model was used to evaluate the in-vivo performance of this TE graft in enhancing graft-to-bone integration.

Results

The BAT, SAC, and SAB well preserved the structure and components of native tendon, cartilage, and bone, showing good biocompatibility. C-GDF7, C-TGFβ3, or C-BMP2 showed a stronger binding ability to BAT, SAC, and SAB. The C-GDF7@BAT, C-TGFβ3@SAC, or C-BMP2@SAB was a controlled delivery system for the scaffold-specific release of GDF7, TGFβ3, and BMP2, thus showing superior tenogenic, chondrogenic, or osteogenic inducibility, respectively. Using a canine ACL reconstruction model, abundant newly-formed bone and connective collagen fibers could be observed at the integration site between TE graft and bone tunnel at postoperative 16 weeks. Meanwhile, the failure load of the reconstructed ACL by TE graft was significantly higher than that of the autograft.

Conclusion

The TE graft could be used to reconstruct ruptured ACL and augment graft-to-bone integration, thus demonstrating high potential for clinical translation in ACL reconstruction.

Translational potential of this article

The findings of the study indicated that the TE graft could be a novel graft for ACL reconstruction with the ability to augment graft-to-bone integration, which may provide a foundation for future clinical application.

Application of Three-Dimension Printing Nano-Carbonated-Hydroxylapatite to the Repair of Defects in Rabbit Bone

Introduction

Hydroxylapatite (HAp) is a biodegradable bone graft material with high biocompatibility. However, the clinical application of HAp has been limited due to the poor absorption rate in vivo.

Methods

In this study, carbonated hydroxylapatite (CHAp) with a chemical composition similar to natural bone was synthesized. HAp and CHAp scaffolds were fabricated by 3D printing. Each material was designed by two types of scaffold model with a maximum width of 8 mm and a thickness of 2 mm, ie, structure I (round shape) and structure II (grid shape). Then, the HAp scaffolds were loaded with lutein. These scaffolds were implanted into the 8 mm bone defect on the top of the rabbit skull within 3 hours in the morning. The curative effects of the scaffolds were assessed two months after implantation.

Results

The 3D printed scaffolds did not cause severe inflammation or rejection after implantation. It showed that the porous structures allow bone cells to enter into the scaffolds. Furthermore, CHAp scaffolds were more biocompatible than HAp scaffolds, and showed a higher level of degradation and new bone formation after implantation. Structure II scaffolds with a smaller mineral content degraded faster than structure I, while structure I had better osteoconductive properties than structure II. Besides, the addition of lutein significantly enhanced the rate of new bone formation.

Discussion

The uniqueness of this study lies in the synthesis of 3D printed CHAp scaffolds and the implantation of CHAp in rabbit bone defects. The incorporation of suitable carbonate and lutein into HAp can enhance the osteoinductivity of the graft, and CHAp has a faster degradation rate in vivo, all of which provide a new reference for the research and application of apatite-based composites.

Bone implant substitutes from synthetic polymer and reduced graphene oxide: Current perspective

In the present work, bone implant materials (BIM) were produced, in sheet form which comprises epoxy resin (synthetic polymer) (ER), calcium carbonate (CaCO3), and reduced graphene oxide (R-GO), by open mold method, for the possibility uses in bone tissue engineering. The developed BIM was analyzed for its physico-chemical, mechanical, bioactivity test, antimicrobial study, and biocompatibility. The BIM had excellent mechanical properties such as tensile strength (194.44 + 0.21 MPa), flexural strength (278.76 + 0.41 MPa), and water absorption (02.61 + 0.24%). A pore size distribution study using the HR-SEM has proved the 180 and 255 μm average pore was observed in the BIM structure. The Bioactivity test of BIM was examined after being immersed in a simulated body fluids (SBF) solution. The result of BIM formed an excellent deposition of bone tube apatite crystals. High-resolution scanning electron microscopy (HR-SEM) morphology of the bone tube apatite crystals revealed the diameter size in the range from 100 ± 159 to 210 ± 188 nm. BIM has excellent antimicrobial characteristics against E. coli (8.75 + 0.06 mm) and S. aureus (9.82 + 0.08 mm). The biocompatibility of the study MTT (3-(4, 5-dimethyl) thiazol-2-yl-2, 5-dimethyl tetrazolium bromide) assay using the MG-63 (human osteoblast cell line) has proven to be the 78% viable cell presence in BIM. After receiving the necessary approval, the scaffold with the required strength and biocompatibility could be tested as a bone implant material in large animals.

NIR light-facilitated bone tissue engineering

In the last decades, near-infrared (NIR) light has attracted considerable attention due to its unique properties and numerous potential applications in bioimaging and disease treatment. Bone tissue engineering for bone regeneration with the help of biomaterials is currently an effective means of treating bone defects. As a controlled light source with deeper tissue penetration, NIR light can provide real-time feedback of key information on bone regeneration in vivo utilizing fluorescence imaging and be used for bone disease treatment. This review provides a comprehensive overview of NIR light-facilitated bone tissue engineering, from the introduction of NIR probes as well as NIR light-responsive materials, and the visualization of bone regeneration to the treatment of bone-related diseases. Furthermore, the existing challenges and future development directions of NIR light-based bone tissue engineering are also discussed. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Effect of Electrical Stimulation on PC12 Cells Cultured in Different Hydrogels: Basis for the Development of Biomaterials in Peripheral Nerve Tissue Engineering

Extensive damage to peripheral nerves is a health problem with few therapeutic alternatives. In this context, the development of tissue engineering seeks to obtain materials that can help recreate environments conducive to cellular development and functional repair of peripheral nerves. Different hydrogels have been studied and presented as alternatives for future treatments to emulate the morphological characteristics of nerves. Along with this, other research proposes the need to incorporate electrical stimuli into treatments as agents that promote cell growth and differentiation; however, no precedent correlates the simultaneous effects of the types of hydrogel and electrical stimuli. This research evaluates the neural differentiation of PC12 cells, relating the effect of collagen, alginate, GelMA, and PEGDA hydrogels with electrical stimulation modulated in four different ways. Our results show significant correlations for different cultivation conditions. Electrical stimuli significantly increase neural differentiation for specific experimental conditions dependent on electrical frequency, not voltage. These backgrounds allow new material treatment schemes to be formulated through electrical stimulation in peripheral nerve tissue engineering.

Adipose stem cells in tissue regeneration and repair: From bench to bedside

ADSCs are a large number of mesenchymal stem cells in Adipose tissue, which can be applied to tissue engineering. ADSCs have the potential of multi-directional differentiation, and can differentiate into bone tissue, cardiac tissue, urothelial cells, skin tissue, etc. Compared with other mesenchymal stem cells, ADSCs have a multitude of promising advantages, such as abundant number, accessibility in cell culture, stable function, and less immune rejection. There are two main methods to use ADSCs for tissue repair and regeneration. One is to implant the "ADSCs-scaffold composite" into the injured site to promote tissue regeneration. The other is cell-free therapy: using ADSC-exos or ADSC-CM alone to release a large number of miRNAs, cytokines and other bioactive substances to promote tissue regeneration. The tissue regeneration potential of ADSCs is regulated by a variety of cytokines, signaling molecules, and external environment. The differentiation of ADSCs into different tissues is also induced by growth factors, ions, hormones, scaffold materials, physical stimulation, and other factors. The specific mechanisms are complex, and most of the signaling pathways need to be further explored. This article reviews and summarizes the mechanism and clinical application of ADSCs in tissue injury repair so far, and puts forward further problems that need to be solved in this field, hoping to provide directions for further research in this field.

Leveraging 3D Bioprinting and Photon-Counting Computed Tomography to Enable Noninvasive Quantitative Tracking of Multifunctional Tissue Engineered Constructs

3D bioprinting is revolutionizing the fields of personalized and precision medicine by enabling the manufacturing of bioartificial implants that recapitulate the structural and functional characteristics of native tissues. However, the lack of quantitative and noninvasive techniques to longitudinally track the function of implants has hampered clinical applications of bioprinted scaffolds. In this study, multimaterial 3D bioprinting, engineered nanoparticles (NPs), and spectral photon-counting computed tomography (PCCT) technologies are integrated for the aim of developing a new precision medicine approach to custom-engineer scaffolds with traceability. Multiple CT-visible hydrogel-based bioinks, containing distinct molecular (iodine and gadolinium) and NP (iodine-loaded liposome, gold, methacrylated gold (AuMA), and Gd2 O3 ) contrast agents, are used to bioprint scaffolds with varying geometries at adequate fidelity levels. In vitro release studies, together with printing fidelity, mechanical, and biocompatibility tests identified AuMA and Gd2 O3 NPs as optimal reagents to track bioprinted constructs. Spectral PCCT imaging of scaffolds in vitro and subcutaneous implants in mice enabled noninvasive material discrimination and contrast agent quantification. Together, these results establish a novel theranostic platform with high precision, tunability, throughput, and reproducibility and open new prospects for a broad range of applications in the field of precision and personalized regenerative medicine.

Cissus quadrangularis L extract-loaded tricalcium phosphate reinforced natural polymer composite for guided bone regeneration

Natural medicines plants are significant considerable attention as potential therapeutic agents for bone tissue engineering. Cissus quadrangularis L (CQ). is a potent therapeutic plant known for its own osteogenic properties. In this research work, a phytoconstituents-filled composite was produced by incorporating CQ extract with gelatin (Gel) and pectin (Pec) polymers collective through β- tricalcium phosphate (β-TCP) bioceramic via a green template method. The effect of CQ-filled composite morphology and chemical structural properties, in vitro cytotoxicity, cell proliferation, and differentiation was investigated. FTIR spectroscopic results indicated the prepared materials' structural confirmation. The CQ extract was the alcoholic -OH merge with the hydroxyl and -NH groups in the range of 3000 cm^-1 to 3500 cm^-1. Scanning electron microscopy images showed that the β-TCP ceramic was perfectly embedded in Gel-Pec polymeric matrix, which is important for bone regeneration. In vitro cell culture results indicated that β-TCP/Gel-Pec/CQ composite provided 92.0% of a favorable substrate for mesenchymal stem cell viability. The gene expression and RT-PCR studies represent the materials with good osteogenic expression, especially the β-TCP/Gel-Pec/CQ composite is observed at 168.0% and 188.0% for RUNx2 and OCN, respectively. The result of the physicochemical characterizations and cell viability studies suggest that CQ-loaded β-TCP/Gel-Pec composite can serve as a potential biomaterial for bone tissue repair and regeneration.

Formulation and Evaluation of Chitosan-PLGA Biocomposite Scaffolds Incorporated with Quercetin Liposomes Made by QbD Approach for Improved Healing of Oral Lesions

The current research aims to develop and evaluate chitosan-PLGA biocomposite scaffolds in combination with quercetin liposomes to accomplish the desired impact in oral lesions where pharmacotherapeutic agent treatment through circulation could only reach the low content at the target. Optimization of quercetin-loaded liposomes was carried out using 32 factorial design. The preparation of porous scaffolds comprising produced quercetin-loaded liposomes by thin-film method was carried out in the current study using a unique strategy combining solvent casting and gas foaming procedures. The prepared scaffolds were tested for physicochemical properties, in vitro quercetin release study, ex vivo drug permeation and retention research using goat mucosa, antibacterial activity, and cell migration studies on fibroblast L929 cell lines. Improved cell growth and migration were seen in the order control < liposomes < proposed system. The proposed system has been examined for its biological and physicochemical features, and it has the potential to be utilized as an efficient therapy for oral lesions.

Adipose-Derived Mesenchymal Stromal Cells: A Tool for Bone and Cartilage Repair

The osteogenic and chondrogenic differentiation ability of adipose-derived mesenchymal stromal cells (ASCs) and their potential therapeutic applications in bone and cartilage defects are reported in this review. This becomes particularly important when these disorders can only be poorly treated by conventional therapeutic approaches, and tissue engineering may represent a valuable alternative. Being of mesodermal origin, ASCs can be easily induced to differentiate into chondrocyte-like and osteocyte-like elements and used to repair damaged tissues. Moreover, they can be easily harvested and used for autologous implantation. A plethora of ASC-based strategies are being developed worldwide: they include the transplantation of freshly harvested cells, in vitro expanded cells or predifferentiated cells. Moreover, improving their positive effects, ASCs can be implanted in combination with several types of scaffolds that ensure the correct cell positioning; support cell viability, proliferation and migration; and may contribute to their osteogenic or chondrogenic differentiation. Examples of these strategies are described here, showing the enormous therapeutic potential of ASCs in this field. For safety and regulatory issues, most investigations are still at the experimental stage and carried out in vitro and in animal models. Clinical applications have, however, been reported with promising results and no serious adverse effects.

Addition of Resolvins D1 or E1 to Collagen Membranes Mitigates Their Resorption in Diabetic Rats

Uncontrolled diabetes is characterized by aberrant inflammatory reactions and increased collagenolysis. We have reported that it accelerates the degradation of implanted collagen membranes (CM), thus compromising their function in regenerative procedures. In recent years, a group of physiological anti-inflammatory agents called specialized pro-resolving lipid mediators (SPMs) have been tested as a treatment for various inflammatory conditions, either systemically or locally, via medical devices. Yet, no study has tested their effect on the fate of the biodegradable material itself. Here, we measured the in vitro release over time of 100 or 800 ng resolvin D1 (RvD1) incorporated into CM discs. In vivo, diabetes was induced in rats with streptozotocin, while buffer-injected (normoglycemic) rats served as controls. Resolvins (100 or 800 ng of RvD1 or RvE1) were added to biotin-labeled CM discs, which were implanted sub-periosteally over the calvaria of rats. Membrane thickness, density, and uniformity were determined by quantitative histology after 3 weeks. In vitro, significant amounts of RvD1 were released over 1-8 days, depending on the amount loaded. In vivo, CMs from diabetic animals were thinner, more porous, and more variable in thickness and density. The addition of RvD1 or RvE1 improved their regularity, increased their density, and reduced their invasion by the host tissue significantly. We conclude that addition of resolvins to biodegradable medical devices can protect them from excessive degradation in systemic conditions characterized by high degree of collagenolysis.

Strategy Based on Michael Addition Reaction for the Development of Bioinspired Multilayered and Multiphasic 3D Constructs

The high incidence of osteochondral defects has increased the interest in the development of improved repairing alternatives, with tissue engineering being considered a promising approach. The hierarchical, complex structure of osteochondral tissue requires the design of a biomimetic multilayered scaffold. Here, a multilayered and multiphasic 3D macroporous structure was achieved at subzero temperature by the Michael addition reaction of amino functionalities of collagen with acryloyl groups of a bifunctionalized poly(ε-caprolactone). This green approach has been successfully applied to crosslink layers of different composition, both for their efficient sequential formation and connection. Polyethylenimine functionalized nano-hydroxyapatite (nHApLPEI) was added to the bottom layer. The resulting hybrid cryogels were characterized by morphology, equilibrium swelling ratios, compressive strength analysis, and MTS assay. They presented good stability, integrity, and biocompatibility. The results revealed that the properties of the prepared constructs may be tuned by varying the composition, number, and thickness of the layers. The Young modulus values were between 3.5 ± 0.02 and 10.5 ± 0.6 kPa for the component layers, while for the multilayered structures they were more than 7.3 ± 0.2 kPa. The equilibrium swelling ratio varied between 4.6 and 14.2, with a value of ~10.5 for the trilayered structure, correlated with the mean pore sizes (74–230 µm).

Synthesis and characterization of UV curable biocompatible hydrophilic copolymers containing siloxane units

Tissues are highly three-dimensional structure complexes composed of different cell types and their interactions. One of the main challenges in tissue engineering is the inability to produce large, highly perfused scaffolds in which cells can grow at a high cell density and viability. Poly(dimethyl siloxane) (PDMS) is used as a flexible, biocompatible cell culture substrate with tunable mechanical properties. However, its fragility and hydrophobicity still pose a challenge. Here, we present a new strategy for the three-step one-pot synthesis of novel biocompatible hydrophilic copolymers containing siloxane units. In the first step, free radical copolymerization of acrylic acid (AA), butyl methacrylate (BMA), and 2-hydroxyethyl methacrylate (HEMA) was carried out in dioxane (DO) solution in the presence of 2,2'-azodiisobutyronitrile (AIBN). In the second step, the copolymers were modified with diepoxypropoxypropyl-terminated polydimethylsiloxane (DE-PDMS), and in the third step, the copolymers were additionally modified with glycidyl methacrylate (GMA). The modified copolymers were characterized by FTIR, NMR spectroscopy and elemental analysis. Films of modified copolymers were prepared by UV curing. SEM studies revealed microphase separated morphology with distribution of PDMS domains. The mechanical properties of the films depended on the amount of incorporated silicone modifier. The films were more hydrophilic than PDMS films. All novel copolymers showed high biocompatibility.

3D bioprinting and its innovative approach for biomedical applications

3D bioprinting or additive manufacturing is an emerging innovative technology revolutionizing the field of biomedical applications by combining engineering, manufacturing, art, education, and medicine. This process involved incorporating the cells with biocompatible materials to design the required tissue or organ model in situ for various in vivo applications. Conventional 3D printing is involved in constructing the model without incorporating any living components, thereby limiting its use in several recent biological applications. However, this uses additional biological complexities, including material choice, cell types, and their growth and differentiation factors. This state-of-the-art technology consciously summarizes different methods used in bioprinting and their importance and setbacks. It also elaborates on the concept of bioinks and their utility. Biomedical applications such as cancer therapy, tissue engineering, bone regeneration, and wound healing involving 3D printing have gained much attention in recent years. This article aims to provide a comprehensive review of all the aspects associated with 3D bioprinting, from material selection, technology, and fabrication to applications in the biomedical fields. Attempts have been made to highlight each element in detail, along with the associated available reports from recent literature. This review focuses on providing a single platform for cancer and tissue engineering applications associated with 3D bioprinting in the biomedical field.

Silk-Based Biomaterials for Designing Bioinspired Microarchitecture for Various Biomedical Applications

Biomaterial research has led to revolutionary healthcare advances. Natural biological macromolecules can impact high-performance, multipurpose materials. This has prompted the quest for affordable healthcare solutions, with a focus on renewable biomaterials with a wide variety of applications and ecologically friendly techniques. Imitating their chemical compositions and hierarchical structures, bioinspired based materials have elevated rapidly over the past few decades. Bio-inspired strategies entail extracting fundamental components and reassembling them into programmable biomaterials. This method may improve its processability and modifiability, allowing it to meet the biological application criteria. Silk is a desirable biosourced raw material due to its high mechanical properties, flexibility, bioactive component sequestration, controlled biodegradability, remarkable biocompatibility, and inexpensiveness. Silk regulates temporo-spatial, biochemical and biophysical reactions. Extracellular biophysical factors regulate cellular destiny dynamically. This review examines the bioinspired structural and functional properties of silk material based scaffolds. We explored silk types, chemical composition, architecture, mechanical properties, topography, and 3D geometry to unlock the body's innate regenerative potential, keeping in mind the novel biophysical properties of silk in film, fiber, and other potential forms, coupled with facile chemical changes, and its ability to match functional requirements for specific tissues.

Application of 3D printed patient-specific instruments in the treatment of large tibial bone defects by the Ilizarov technique of distraction osteogenesis

Background

The Ilizarov technique of distraction osteogenesis is an effective treatment for tibia defect. However, repeated attempts to reduce due to the complexity of the bone defect during the operation will increase the operation time and iatrogenic injury, and excessive radiation exposure. Three-dimensional (3D)-printed patient-specific instrument (PSI) for preoperative 3D planning and intraoperative navigation have the advantages of accuracy and visualization. The purpose of this study is to investigate whether 3D-printed PSI is helpful to correct tibial bone defects accurately and effectively.

Method

From May 2019 to September 2022, 19 patients with tibial bone defects were treated, including 9 males and 10 females, aged 37 to 64 years. There were 4 cases in proximal tibia, 9 in midshaft tibia and 6 in distal tibia. All were treated with Ilizarov technique of distraction osteogenesis. 3D-printed PSI was used in 9 cases, while traditional surgery was used in 10 cases. All patients underwent computed tomography before surgery. Computer software was used to analyze the measurement results, design and print PSI. During the operation, PSI was used to assist in reduction of tibia. Operation times were recorded in all cases, the number of fluoroscopy during the operation, and the varus/valgus, anteversion/reversion angle after the operation were measured. All measurement data were expressed by means ± SD, and Student's t test was used to examine differences between groups. The chi square test or Fisher's precise test was used to compare the counting data of the two groups.

Result

All PSI matched well with the corresponding tibia bone defect, and were consistent with the preoperative plan and intraoperative operation. The affected limb had a good reduction effect. The operation time from the beginning of PSI installation to the completion of Ilizarov ring fixator installation was 31.33 ± 3.20 min, while that in the traditional operation group was 64.10 ± 6.14 min (p < 0.001). The times of fluoroscopy in the PSI group during operation was 10.11 ± 1.83, and that in the traditional operation group was 27.60 ± 5.82. The reduction effect of tibia in PSI group was better than that in traditional operation group, with the average angle of PSI group is 1.21 ± 0.24°, and that of traditional operation group is 2.36 ± 0.33° (p < 0.001).

Conclusion

The PSI simplifies procedures, reduces the difficulty of the operation, improves the accuracy of the operation, and provides a good initial position when used in distraction osteogenesis to treat the tibial defects.

Can Our Blood Help Ensure Antimicrobial and Anti-Inflammatory Properties in Oral and Maxillofacial Surgery?

In recent decades, the potential of PRF has been extensively studied. The number of studies about PRF has increased three times since the year 2012, but the full spectrum of its fundamental properties, such as antimicrobial and anti-inflammatory activity, is not clearly described. In oral and maxillofacial surgery, PRF is described in alveolar ridge preservation, orthognathic surgery, cleft lip and palate surgery, maxillary sinus augmentation, and dental implant placement as demonstrating favorable results and its clinical advantages. The structural complexity, inhomogeneous nature, and clotting ability of PRF make its antimicrobial effect evaluation complicated. Nevertheless, most of the used antimicrobial testing methods are based on antibacterial agent diffusion ability in culture media. Because the oral and maxillofacial region is the most frequent area of PRF application, its antimicrobial activity evaluation also prevails in the oral microbiome. PRF's biological potential is highly dependent on the specific preparation protocol and methodology used; it should be carefully prepared and kept under proper conditions to keep cellular content alive. PRF's influence on living cells demonstrates a stimulating effect on bone regeneration, and an angiogenetic effect, and it provides anti-inflammatory activity. According to analyzed studies, PRF demonstrated success in oral and maxillofacial surgery in various methods of application. Antibacterial and anti-inflammatory properties were proven by antibacterial activity against different bacterial species, sustained growth factor, sustained release, and cell activity on the material application. Accurately and correctly prepared PRF can ensure antibacterial and anti-inflammatory properties, and it can be a beneficial clinical tool in oral and maxillofacial surgery.

Tissue Engineering for Gastrointestinal and Genitourinary Tracts

The gastrointestinal and genitourinary tracts share several similarities. Primarily, these tissues are composed of hollow structures lined by an epithelium through which materials need to flow with the help of peristalsis brought by muscle contraction. In the case of the gastrointestinal tract, solid or liquid food must circulate to be digested and absorbed and the waste products eliminated. In the case of the urinary tract, the urine produced by the kidneys must flow to the bladder, where it is stored until its elimination from the body. Finally, in the case of the vagina, it must allow the evacuation of blood during menstruation, accommodate the male sexual organ during coitus, and is the natural way to birth a child. The present review describes the anatomy, pathologies, and treatments of such organs, emphasizing tissue engineering strategies.

A Doubly Fmoc-Protected Aspartic Acid Self-Assembles into Hydrogels Suitable for Bone Tissue Engineering

Hydrogels have been used as scaffolds for biomineralization in tissue engineering and regenerative medicine for the repair and treatment of many tissue types. In the present work, we studied an amino acid-based material that is attached to protecting groups and self-assembles into biocompatible and stable nanostructures that are suitable for tissue engineering applications. Specifically, the doubly protected aspartic residue (Asp) with fluorenyl methoxycarbonyl (Fmoc) protecting groups have been shown to lead to the formation of well-ordered fibrous structures. Many amino acids and small peptides which are modified with protecting groups display relatively fast self-assembly and exhibit remarkable physicochemical properties leading to three-dimensional (3D) networks, the trapping of solvent molecules, and forming hydrogels. In this study, the self-assembling fibrous structures are targeted toward calcium binding and act as nucleation points for the binding of the available phosphate groups. The cell viability, proliferation, and osteogenic differentiation of pre-osteoblastic cells cultured on the formed hydrogel under various conditions demonstrate that hydrogel formation in CaCl₂ and CaCl₂-Na₂HPO₄ solutions lead to calcium ion binding onto the hydrogels and enrichment with phosphate groups, respectively, rendering these mechanically stable hydrogels osteoinductive scaffolds for bone tissue engineering.

Biomedical Applications of Microfluidic Devices: A Review

Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.

Recombinant and genetic code expanded collagen-like protein as a tailorable biomaterial

Collagen occurs in nature with a dedicated triple helix structure and is the most preferred biomaterial in commercialized medical products. However, concerns on purity, disease transmission, and the reproducibility of animal derived collagen restrict its applications and warrants alternate recombinant sources. The expression of recombinant collagen in different prokaryotic and eukaryotic hosts has been reported with varying degrees of success, however, it is vital to elucidate the structural and biological characteristics of natural collagen. The recombinant production of biologically functional collagen is restricted by its high molecular weight and post-translational modification (PTM), especially the hydroxylation of proline to hydroxyproline. Hydroxyproline plays a key role in the structural stability and higher order self-assembly to form fibrillar matrices. Advancements in synthetic biology and recombinant technology are being explored for improving the yield and biomimicry of recombinant collagen. It emerges as reliable, sustainable source of collagen, promises tailorable properties and thereby custom-made protein biomaterials. Remarkably, the evolutionary existence of collagen-like proteins (CLPs) has been identified in single-cell organisms. Interestingly, CLPs exhibit remarkable ability to form stable triple helical structures similar to animal collagen and have gained increasing attention. Strategies to expand the genetic code of CLPs through the incorporation of unnatural amino acids promise the synthesis of highly tunable next-generation triple helical proteins required for the fabrication of smart biomaterials. The review outlines the importance of collagen, sources and diversification, and animal and recombinant collagen-based biomaterials and highlights the limitations of the existing collagen sources. The emphasis on genetic code expanded tailorable CLPs as the most sought alternate for the production of functional collagen and its advantages as translatable biomaterials has been highlighted.

Scaffold-based bone tissue engineering in microgravity: potential, concerns and implications

One of humanity's greatest challenges is space exploration, which requires an in-depth analysis of the data continuously collected as a necessary input to fill technological gaps and move forward in several research sectors. Focusing on space crew healthcare, a critical issue to be addressed is tissue regeneration in extreme conditions. In general, it represents one of the hottest and most compelling goals of the scientific community and the development of suitable therapeutic strategies for the space environment is an urgent need for the safe planning of future long-term manned space missions. Osteopenia is a commonly diagnosed disease in astronauts due to the physiological adaptation to altered gravity conditions. In order to find specific solutions to bone damage in a reduced gravity environment, bone tissue engineering is gaining a growing interest. With the aim to critically investigate this topic, the here presented review reports and discusses bone tissue engineering scenarios in microgravity, from scaffolding to bioreactors. The literature analysis allowed to underline several key points, such as the need for (i) biomimetic composite scaffolds to better mimic the natural microarchitecture of bone tissue, (ii) uniform simulated microgravity levels for standardized experimental protocols to expose biological materials to the same testing conditions, and (iii) improved access to real microgravity for scientific research projects, supported by the so-called democratization of space.

Hyaluronic Acid Scaffolds for Loco-Regional Therapy in Nervous System Related Disorders

Hyaluronic acid (HA) is a Glycosaminoglycan made of disaccharide units containing N-acetyl-D-glucosamine and glucuronic acid. Its molecular mass can reach 10 MDa and its physiological properties depend on its polymeric property, polyelectrolyte feature and viscous nature. HA is a ubiquitous compound found in almost all biological tissues and fluids. So far, HA grades are produced by biotechnology processes, while in the human organism it is a major component of the extracellular matrix (ECM) in brain tissue, synovial fluid, vitreous humor, cartilage and skin. Indeed, HA is capable of forming hydrogels, polymer crosslinked networks that are very hygroscopic. Based on these considerations, we propose an overview of HA-based scaffolds developed for brain cancer treatment, central and peripheral nervous systems, discuss their relevance and identify the most successful developed systems.

Biomaterials for Tissue Engineering Applications and Current Updates in the Field: A Comprehensive Review

Tissue engineering has emerged as an interesting field nowadays; it focuses on accelerating the auto-healing mechanism of tissues rather than organ transplantation. It involves implanting an In Vitro cultured initiative tissue or a scaffold loaded with tissue regenerating ingredients at the damaged area. Both techniques are based on the use of biodegradable, biocompatible polymers as scaffolding materials which are either derived from natural (e.g. alginates, celluloses, and zein) or synthetic sources (e.g. PLGA, PCL, and PLA). This review discusses in detail the recent applications of different biomaterials in tissue engineering highlighting the targeted tissues besides the in vitro and in vivo key findings. As well, smart biomaterials (e.g. chitosan) are fascinating candidates in the field as they are capable of elucidating a chemical or physical transformation as response to external stimuli (e.g. temperature, pH, magnetic or electric fields). Recent trends in tissue engineering are summarized in this review highlighting the use of stem cells, 3D printing techniques, and the most recent 4D printing approach which relies on the use of smart biomaterials to produce a dynamic scaffold resembling the natural tissue. Furthermore, the application of advanced tissue engineering techniques provides hope for the researchers to recognize COVID-19/host interaction, also, it presents a promising solution to rejuvenate the destroyed lung tissues.

Li-Doped Bioactive Ceramics: Promising Biomaterials for Tissue Engineering and Regenerative Medicine

Lithium (Li) is a metal with critical therapeutic properties ranging from the treatment of bipolar depression to antibacterial, anticancer, antiviral and pro-regenerative effects. This element can be incorporated into the structure of various biomaterials through the inclusion of Li chloride/carbonate into polymeric matrices or being doped in bioceramics. The biocompatibility and multifunctionality of Li-doped bioceramics present many opportunities for biomedical researchers and clinicians. Li-doped bioceramics (capable of immunomodulation) have been used extensively for bone and tooth regeneration, and they have great potential for cartilage/nerve regeneration, osteochondral repair, and wound healing. The synergistic effect of Li in combination with other anticancer drugs as well as the anticancer properties of Li underline the rationale that bioceramics doped with Li may be impactful in cancer treatments. The role of Li in autophagy may explain its impact in regenerative, antiviral, and anticancer research. The combination of Li-doped bioceramics with polymers can provide new biomaterials with suitable flexibility, especially as bio-ink used in 3D printing for clinical applications of tissue engineering. Such Li-doped biomaterials have significant clinical potential in the foreseeable future.

Design considerations of benchtop fluid flow bioreactors for bio-engineered tissue equivalents in vitro

One of the major aims of bio-engineering tissue equivalents in vitro is to create physiologically relevant culture conditions to accurately recreate the cellular microenvironment. This often includes incorporation of factors such as the extracellular matrix, co-culture of multiple cell types and three-dimensional culture techniques. These advanced techniques can recapitulate some of the properties of tissue in vivo, however fluid flow is a key aspect that is often absent. Fluid flow can be introduced into cell and tissue culture using bioreactors, which are becoming increasingly common as we seek to produce increasingly accurate tissue models. Bespoke technology is continuously being developed to tailor systems for specific applications and to allow compatibility with a range of culture techniques. For effective perfusion of a tissue culture many parameters can be controlled, ranging from impacts of the fluid flow such as increased shear stress and mass transport, to potentially unwanted side effects such as temperature fluctuations. A thorough understanding of these properties and their implications on the culture model can aid with a more accurate interpretation of results. Improved and more complete characterisation of bioreactor properties will also lead to greater accuracy when reporting culture conditions in protocols, aiding experimental reproducibility, and allowing more precise comparison of results between different systems. In this review we provide an analysis of the different factors involved in the development of benchtop flow bioreactors and their potential biological impacts across a range of applications.

Advances for the treatment of lower extremity arterial disease associated with diabetes mellitus

Lower extremity arterial disease (LEAD) is a major vascular complication of diabetes. Vascular endothelial cells dysfunction can exacerbate local ischemia, leading to a significant increase in amputation, disability, and even mortality in patients with diabetes combined with LEAD. Therefore, it is of great clinical importance to explore proper and effective treatments. Conventional treatments of diabetic LEAD include lifestyle management, medication, open surgery, endovascular treatment, and amputation. As interdisciplinary research emerges, regenerative medicine strategies have provided new insights to treat chronic limb threatening ischemia (CLTI). Therapeutic angiogenesis strategies, such as delivering growth factors, stem cells, drugs to ischemic tissues, have also been proposed to treat LEAD by fundamentally stimulating multidimensional vascular regeneration. Recent years have seen the rapid growth of tissue engineering technology; tissue-engineered biomaterials have been used to study the treatment of LEAD, such as encapsulation of growth factors and drugs in hydrogel to facilitate the restoration of blood perfusion in ischemic tissues of animals. The primary purpose of this review is to introduce treatments and novel biomaterials development in LEAD. Firstly, the pathogenesis of LEAD is briefly described. Secondly, conventional therapies and therapeutic angiogenesis strategies of LEAD are discussed. Finally, recent research advances and future perspectives on biomaterials in LEAD are proposed.