The Overview of Porous, Bioactive Scaffolds as Instructive Biomaterials for Tissue Regeneration and Their Clinical Translation

Scaffold geometries designed to promote bone ingrowth by enhancing mechanobiological stimulation and biotransportation - A multiobjective optimisation approach

In a tissue-engineered bone scaffold implant, the process of neo-tissue ingrowth and remodelling into hard lamellar bone occurs slowly; it typically requires a period of several months to a year (or more) to complete. This research considers the design optimisation of a scaffold's unit cell geometry for the purpose of accelerating the rate at which neo-tissue forms in the porous network of the scaffold (ingrowth), and hence, reduce the length of time to complete the bone ingrowth process. In this study, the basic structure of the scaffold is the Schwarz Primitive (P) surface unit cell, selected for its compelling biomechanical and permeability characteristics. The geometry of the scaffold is varied using two parameters (namely iso-value, k, and spatial period, a) within the surface equation defining the Schwarz P-surface unit cell. In total, sixteen different unit cell geometries are considered here with the porosity ranging from 50% to 82%. The design objectives for the scaffold are to (i) enhance mechanobiological stimulus conditions conducive to bone apposition and (ii) enhance permeability to improve the transport of nutrients/oxygen and metabolities to and from the sites of neo-tissue formation throughout the porous scaffold. The independent design variables (k and a) of the periodic unit cell geometry are optimised to best satisfy the design objectives of appositional mechanobiological stimulus and biotransporting permeability. First, a reconstructed sheep mandible computed tomographic (CT)-based finite element (FE) analysis model is used to relate the strain energy density and mechanobiological stimulus to the design variables. Next, a computational fluid dynamics (CFD) model of a 5 × 5 × 5 unit cell scaffold is developed to relate the distributions of pressure and fluid velocity to the design variables. Then, surrogate modelling is undertaken in which bivariate cubic polynomial response surfaces are fitted to the FE and CFD analysis output data to form mathematical functions of each objective with respect to the two design variables. Finally, a multiobjective optimisation algorithm is invoked to determine the best trade-off between the competing design objectives of mechanobiological stimulus and biofluidic permeability. The novel design of the scaffold structure is anticipated to provide a better biomechanical and biotransport environment for tissue regeneration.

A review on the characterization of edible scaffolds for cultured meat: Physical, chemical, biocompatibility, and food safety evaluation methods

Scaffolds are three-dimensional biomaterials that act as structural blueprint for cultured meat precursor cells. The advancement of scaffold fabrication techniques and the development of novel scaffolds specifically designed for cultured meat are evident in numerous scaffold-based cultured meat reports, highlighting the advantages of the scaffolds using different characterization and evaluation techniques encompassing the physical, mechanical, chemical, and biological features of the scaffolds. Considering the potential of scaffolds to be included in cultured meat products, standardization of evaluation techniques could aid in preventing misrepresentation and possible food safety concerns in cultured meat production. Thus, appropriate food safety evaluation methods must be included to properly establish scaffolds as food safe or edible. The standardization of scaffold evaluation methods could aid in increasing the dependability and consumption of scaffold-based cultured meat.

Bacterial cellulose-based scaffold modified with anti-CD29 antibody to selectively capture urine-derived stem cells for bladder repair

Acellular cellulose-based biomaterials hold promising potential for treating bladder injuries. However, the compromised cellular state surrounding the wound impedes the complete reconstruction of the bladder. This necessitates the development of a bio-instructive cellulose-based biomaterial that actively controls cell behavior to facilitate effective bladder regeneration. To develop such an advanced cell-free scaffold, a bacterial cellulose (BC) substrate is elaborately modified through layer-by-layer assembly of heparin and collagen (H/C), followed by glutaraldehyde crosslinking, resulting in a biomimetic nanofibrous scaffold with optimized mechanical properties and reduced salt crystal deposition. Critically, the scaffold is functionalized with anti-CD29 antibodies, enabling selective in situ capture of urine-derived stem cells (USCs) without compromising their viability. The (H/C)-modified BC scaffold exhibits exceptional swelling and extracellular matrix-like architecture, which mirrors the natural bladder environment. Fluorescent immunostaining confirms uniform antibody grafting, confirming the efficacy of this modified biomaterial in attracting and retaining USCs. Overall, this study introduces a BC-based scaffold that has been innovatively modified with CD29, enabling the selective capture of USCs from urine. This innovative acellular biomaterial represents a promising acellular strategy to address the challenges posed by compromised cellular conditions during bladder reconstruction, offering a novel avenue for regenerative bladder therapies.

Synergistic enhancement of angiogenesis and osseointegration in 3D-printed porous polyetheretherketone scaffolds using biomimetic coatings of bone morphogenetic protein-2/fibronectin

This study explored a novel modification method for porous polyetheretherketone (PEEK) implants using a biomimetic coating to achieve synergistic enhancement of vascularization and bone regeneration. Inspired by the natural extracellular matrix (ECM) structure (consists of growth factors and matrix proteins), a biomimetic dual-factor coating capable of releasing bone morphogenetic protein-2 (BMP-2) and fibronectin (FN) was coated on the surface of 3D-printed porous PEEK scaffolds using polydopamine (PDA) as a binder. Experiments conducted with MC3T3-E1 cells or HUVECs in co-culture with scaffolds revealed that the biomimetic coating not only synergically promoted cell migration, adhesion and proliferation, but also enhanced angiogenesis and osteogenic differentiation simultaneously in vivo. The synergistic effect is attributed to the crosstalks between intracellular signaling pathways of FN and BMP-2, as well as the sustained release on account of their combination mitigates explosive release and degradation of BMP-2. Overall, this study designed a novel biomimetic coating modified PEEK scaffolds and confirmed the synergistic mechanism of the scaffolds on osteogenic differentiation and angiogenesis for the first time. These insights have significant implications for the clinical transformation of PEEK dental implants.

In Situ Preparation of Composite Scaffolds Based on Polyurethane and Hydroxyapatite Particles for Bone Tissue Engineering

This article details the in situ preparation of composite scaffolds using polyurethane (PU) and HAp (hydroxyapatite), focusing on the unique properties of buriti oil (Mauritia flexuosa L.) applicable to tissue engineering. PU derived from vegetable oils, particularly buriti oil, has shown promise in bone tissue repair due to its rich bioactive compounds. Buriti oil is an excellent candidate for manufacturing these materials as it is an oil rich in bioactive compounds such as carotenoids, tocopherols, and fatty acids, which have antioxidant and anti-inflammatory properties. Furthermore, buriti oil has oleic acid as its principal fatty acid, which has been investigated as an excellent HAp dispersant. This research aimed to synthesize PU scaffolds from a polyol derived from buriti oil and incorporate HAp in different concentrations into the polymeric matrix through in situ polymerization. The chemical composition of the materials obtained, the distribution of hydroxyapatite particles in the polyurethane matrix, and the thermal stability were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and thermogravimetry (TGA). In addition, to investigate biocompatibility, MTT tests (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium) were conducted using rat bone-marrow-derived mesenchymal stem cells (BMMSC). Characterizations confirm the formation of PU and the presence of HAp in the polymeric matrix, and the materials did not show cytotoxicity.

Silk biomaterials for corneal tissue engineering: From research approaches to therapeutic potentials; A review

The corneal complications can result in opacity and eventual blindness. Furthermore, a shortage of available donors constrains the existing therapeutic options. Therefore, one of the most promising strategies involves the application of biomaterials, particularly silk. Silk has garnered significant attention among these biomaterials due to its natural origin and diverse features derived from different sources. One of the most critical factors of silk is its transparency, which is crucial for the cornea, and there are no concerns about infection. This material also possesses several advantages, including cost-effectiveness in production, biocompatibility in vivo and in vitro, biodegradation, and desirable mechanical characteristics. Modifications in the topographical structure, porosity, and crystallinity of silk enhance its properties and optimize its suitability for wound dressing, efficient drug delivery systems, and various cornea-related treatments. In each layer, silk was examined as a single biomaterial or blended with the others, so, this review aims to explore silk as a potential material for corneal regenerative medicine from a novel viewpoint. By considering a range of studies, a classification system has been developed that categorizes the utilization of silk in the various layers of the cornea and sub-categorizes the different modifications and applications of silk.

Fabrication and in vitro cytocompatibility evaluation of porous bone scaffold based on cuttlefish bone-derived nano-carbonated hydroxyapatite reinforced with polyethylene oxide/chitosan fibrous structure

A novel porous bone scaffold based on nano-carbonated hydroxyapatite reinforced with fibrous-like structured polyethylene oxide/chitosan network (nCHA/PEO/CS) was introduced and fabricated via freeze-drying. Prior to this, the nCHA was synthesized through a hydrothermal reaction based on cuttlefish bone (CFB, Sepia officinalis). The raw cuttlefish bone (raw-CFB) was first decomposed to obtain cuttlefish bone-derived calcium oxide (CaO-CFB) by calcination at 1000 °C, which was used for synthesizing nCHA. The chemical composition analysis showed that the nCHA formed AB-type CHA with a high carbonate content of 7.38 wt%, which is in the range of carbonate content in native bone (2-9 wt%). The Ca/P molar ratio of nCHA was 1.712, very close to the Ca/P of biological apatite of 1.71. Morphological analysis revealed that nCHA consists of nanosized particles, potentially offering a large surface area to volume to promote ion exchange and cell interaction. The excellent physicochemical and morphological properties of nCHA proposed suitability as a bone scaffold precursor combined with PEO and CS. The nCHA/PEO/CS scaffolds were freeze-dried with varying PEO/CS concentrations. Physicochemical analysis indicated that increasing the PEO/CS concentration decreased the crystallinity of the scaffold, causing it to be lower than the nCHA crystallinity, which may be beneficial for cell growth. Morphological analysis revealed that the scaffold structure comprised nCHA cross-linked within a fibrous-like structured PEO/CS network, which appropriately mimics the fibrous structure of extracellular matrix (ECM) in natural bone. However, the nCHA/PEO/CS-11 scaffold formed more appropriate pores with suitable porosity for cell development, blood vessel formation, and nutrient perfusion. The nCHA/PEO/CS-11 scaffold also demonstrated sufficient compressive strength and good swelling behavior, which may favor bone regeneration. The nCHA/PEO/CS-11 scaffold demonstrated high cytocompatibility and facilitated the adherence of MC3T3E1 cells on the scaffold surface. The nCHA/PEO/CS-11 scaffold also promoted cell osteogenic differentiation. Owing to its desirable and suitable characteristics, the nCHA/PEO/CS-11 scaffold is promising in bone tissue engineering.

Evaluation and optimization of physical, mechanical, and biological characteristics of 3D printed Whitlockite/calcium silicate composite scaffold for bone tissue regeneration using response surface methodology

Calcium phosphate-based bioscaffolds are used for bone tissue regeneration because of their physical and chemical resemblance to human bone. Calcium, phosphate, sodium, potassium, magnesium, and silicon are important components of human bone. The successful biomimicking of human bone characteristics involves incorporating all the human bone elements into the scaffold material. In this work, Mg-Whitlockite (WH) and Calcium Silicate (CS) were selected as matrix and reinforcement respectively, because of their desirable elemental composition and regenerative properties. The magnesium in WH increases mineralization in bone, and the silicon ions in CS support vascularization. The Mg-WH was synthesized using the wet chemical method, and powder characterization tests were performed. Response surface methodology (RSM) is used to design the experiments with a combination of material compositions, infill ratios (IFs), and sintering temperatures (STs). The WH/CS bioceramic composite is 3D printed in three different compositions: 100/0, 75/25, and 50/50 wt%, with IFs of 50%, 75%, and 100%. The physical and mechanical characterization study of printed samples is conducted and the result is optimized using RSM. ANOVA (Analysis of Variance) is used to establish the relationship between input parameters and responses. The optimized input parameters were the WH/CS composition of 50/50 wt%, IF of 50%, and ST of 1150 °C, which bring out the best possible combination of physical and mechanical characteristics. The RSM optimized response was a density of 2.27 g cm-3, porosity of 36.74%, wettability of 45.79%, shrinkage of 25.13%, compressive strength of 12 MPa, and compressive modulus of 208.49 MPa with 92% desirability. The biological characterization studies were conducted for the scaffold samples prepared with optimized input parameters. The biological studies confirmed the capabilities of the WH/CS composite scaffolds in bone regenerative applications.

Development of Recombinant Human Collagen-Based Porous Scaffolds for Skin Tissue Engineering: Enhanced Mechanical Strength and Biocompatibility

Skin tissue engineering scaffolds should possess key properties such as porosity, degradability, durability, and biocompatibility to effectively facilitate skin cell adhesion and growth. In this study, recombinant human collagen (RHC) was used to fabricate porous scaffolds via freeze-drying, offering an alternative to animal-derived collagen where bovine collagen (BC)-based scaffolds were also prepared for comparison. The internal morphology of the RHC scaffolds were characterized by scanning electron microscopy (SEM) and the pore size ranged from 68.39 to 117.52 µm. The results from compression and fatigue tests showed that the mechanical strength and durability of RHC scaffolds could be tailored by adjusting the RHC concentration, and the maximum compressive modulus reached to 0.003 MPa, which is comparable to that of BC scaffolds. The degradation test illustrated that the RHC scaffolds had a slower degradation rate compared to BC scaffolds. Finally, the biocompatibilities of the porous scaffolds were studied by seeding and culturing the human foreskin fibroblasts (HFFs) and human umbilical vein endothelial cells (HUVECs) in samples. The fluorescent images and Cell Counting Kit-8 (CCK-8) assay revealed RHC porous scaffolds were non-cytotoxic and supported the attachment as well as the proliferation of the seeded cells. Overall, the results demonstrated that RHC-based scaffolds exhibited adequate mechanical strength, ideal biodegradability, and exceptional biocompatibility, making them highly suitable for skin-tissue-engineering applications.

Development of Tailored Porous Ti6Al4V Materials by Extrusion 3D Printing

Nowadays, metallic bone replacement is in high demand due to different issues, like sicknesses and accidents. Thus, bone implants are fabricated with tailored properties and microstructure for long-term use in the human body. To improve such implants, 3D printing is the most promising technique. Therefore, this work aims to evaluate the fabrication of porous materials by extrusion 3D printing of Ti6Al4V. Cylindrical samples were fabricated from pellets for metal injection molding of Ti6Al4V powders, creating hexagonal channels with three different sizes. The densification kinetics was evaluated by dilatometry tests, which enabled following the densification of the samples during the sintering cycle. Subsequently, the samples were characterized by scanning electron microscopy and X-ray computed tomography to analyze their microstructure. Compression tests evaluated the mechanical strength of sintered samples. It was found that the hexagonal shape during printing is better defined as the channel size increases. The results show similar behavior for each of the channel sizes during sintering; however, greater densification is obtained as the channel size decreases. Additionally, microporosity is obtained at the particle level, which is completely interconnected, ensuring the passage of fluids through the entire sample. On the other hand, as the channel size increases, Young's modulus and yield strength are considerably reduced. The main conclusion is that parts with two scales of porosity can be designed by the 3D printing extrusion process.

A 3D bioprinted adhesive tissue engineering scaffold to repair ischemic heart injury

Adhesive tissue engineering scaffold (ATES) devices can be secured on tissues by relying on their intrinsic adhesive properties, hence, avoiding the complications such as host tissue/scaffold damage that are associated with conventional scaffold fixation methods like suturing or bioglue. This study introduces a new generation of three-dimensional (3D) bioprinted ATES systems for use as cardiac patches to regenerate the adult human heart. Tyramine-modified methacrylated hyaluronic acid (HAMA-tyr), gelatin methacrylate (GelMA), and gelatin were used to create the hybrid bioink formulation with self-adhesive properties. ATESs were bioprinted and further modified to improve the adhesion properties. In-depth characterization of printing fidelity, pore size, mechanical properties, swelling behavior, as well as biocompatibility was used to create ATESs with optimal biological function. Following in vitro testing, the ATESs were tested in a mouse model of myocardial infarction to study the scaffold adhesive strength in biological milieu. The method developed in this study can be used to manufacture off-the-shelf ATESs with complex cellular and extracellular architecture, with robust potential for clinical translation into a variety of personalized tissue engineering and regenerative medicine applications.

Advancements in bioengineered and autologous skin grafting techniques for skin reconstruction: a comprehensive review

The reconstruction of complex skin defects challenges clinical practice, with autologous skin grafts (ASGs) as the traditional choice due to their high graft take rate and patient compatibility. However, ASGs have limitations such as donor site morbidity, limited tissue availability, and the necessity for multiple surgeries in severe cases. Bioengineered skin grafts (BSGs) aim to address these drawbacks through advanced tissue engineering and biomaterial science. This study conducts a systematic review to describe the benefits and shortcomings of BSGs and ASGs across wound healing efficacy, tissue integration, immunogenicity, and functional outcomes focusing on wound re-epithelialization, graft survival, and overall aesthetic outcomes. Preliminary findings suggest ASGs show superior early results, while BSGs demonstrate comparable long-term outcomes with reduced donor site morbidity. This comparative analysis enhances understanding of bioengineered alternatives in skin reconstruction, potentially redefining best practices based on efficacy, safety, and patient-centric outcomes, highlighting the need for further innovation in bioengineered solutions.

Controlled delivery of mesenchymal stem cells via biodegradable scaffolds for fracture healing

Biodegradable controlled delivery systems for mesenchymal stem cells (MSCs) have emerged as novel advancements in the field of regenerative medicine, particularly for accelerating bone fracture healing. This detailed study emphasizes the importance of quick and adequate fracture treatment and the limitations of existing methods. New approaches employing biodegradable scaffolds can be placed within a fracture to serve as a mechanical support and allow controlled release of in situ MSCs and bioactive agents. They are made up of polymers and composites which degrade over time, aiding in natural tissue regrowth. The fabrication methods, including 3D printing, electrospinning, and solvent casting, with particulate leaching that enable precise control over scaffold architecture and properties, are discussed. Progress in controlled drug delivery systems including encapsulation techniques and release kinetics is described, highlighting the potential of such strategies to maintain therapeutic benefits over a prolonged time as well as improving outcomes for fracture repair. MSCs play a role in bone regeneration through differentiation using biodegradable scaffolds, paracrine effects, and regulation of inflammation focusing on fracture healing. Current trends and future directions in scaffold technology and MSC delivery, including smart scaffolds with growth factor incorporation and innovative delivery approaches for fracture healing are also discussed.

Optimizations of Placenta Extracellular Matrix-Loaded Silk Fibroin/Alginate 3D-Printed Scaffolds Structurally and Functionally for Bone Tissue Engineering

Recent interest has been focused on extracellular matrix (ECM)-based scaffolds totreat critical-sized bone injuries. In this study, urea was used to decellularize and solubilize human placenta tissue. Then, different concentrations of ECM were composited with 8% alginate (Alg) and 12% silk fibroin (SF) for printing in order to produce a natural 3D construct that resembled bone tissue. The physical and biological features of the printed structures were evaluated entirely in vitro. Finally, a rat model was employed to examine the optimal 3D printed scaffold (5% ECM) as a bone transplant for the healing of cranial bone lesions. The present investigation demonstrated that decellularizing placental tissue fragments led to efficient removal of cell debris. In addition, a remarkable improvement in the printed scaffolds' mechanical and biological properties was observed by increasing the ECM concentration. The histology studies and real-time PCR results demonstrated the acceleration of bone regeneration in the bone lesions treated with 5%ECM-SF/Alg at 4 and 8 weeks after implantation. Overall, these results proved that the placental ECM-printed scaffolds could potentially construct biomimetic grafts to reconstruct significant bone defects and now promise to proceed with clinical studies.

Functionalization of 3D printed poly(lactic acid)/graphene oxide/β-tricalcium phosphate (PLA/GO/TCP) scaffolds for bone tissue regeneration application

The challenge of bone tissue regeneration implies the use of new advanced technologies for the manufacture of polymeric matrices, with 3D printing technology being a suitable option for tissue engineering due to its low processing cost, its simple operation and the wide use of biomaterials in biomedicine. Among the biopolymers used to obtain porous scaffolds, poly(lactic acid) (PLA) stands out due its mechanical and biodegradability properties, although its low bioactivity to promote bone regeneration is a great challenge. In this research, a 3D scaffold based on PLA reinforced with bioceramics such as graphene oxide (GO) and β-tricalcium phosphate (TCP) was designed and characterized by FTIR, XRD, DSC, SEM and mechanical tests. The in vitro biocompatibility, viability, and cell proliferation of the poly-l-lysine (POLYL) functionalized scaffold were investigated using Wharton Jelly mesenchymal stem cells (hWJ-MSCs) and confirmed by XPS. The incorporation of GO/TCP bioceramics into the PLA polymer matrix increased the mechanical strength and provided a thermal barrier during the fusion treatments that the polymeric material undergoes during its manufacturing. The results show that the functionalization of the scaffold with POLYL allows improving the cell adhesion, proliferation and differentiation of hWJ-MSCs. The resulting scaffold PLA/GO/TCP/POLYL exhibits enhanced structural integrity and osteogenic cues, rendering it a promising candidate for biomedical applications.

Mechanical and Physical Characterization of a Biphasic 3D Printed Silk-Infilled Scaffold for Osteochondral Tissue Engineering

Osteochondral tissue damage is a serious concern, with even minor cartilage damage dramatically increasing an individual's risk of osteoarthritis. Therefore, there is a need for an early intervention for osteochondral tissue regeneration. 3D printing is an exciting method for developing novel scaffolds, especially for creating biological scaffolds for osteochondral tissue engineering. However, many 3D printing techniques rely on creating a lattice structure, which often demonstrates poor cell bridging between filaments due to its large pore size, reducing regenerative speed and capacity. To tackle this issue, a novel biphasic scaffold was developed by a combination of 3D printed poly(ethylene glycol)-terephthalate-poly(butylene-terephthalate) (PEGT/PBT) lattice infilled with a porous silk scaffold (derived from Bombyx mori silk fibroin) to make up a bone phase, which continued to a seamless silk top layer, representing a cartilage phase. Compression testing showed scaffolds had Young's modulus, ultimate compressive strength, and fatigue resistance that would allow for their theoretical survival during implantation and joint articulation without stress-shielding mechanosensitive cells. Fluorescent microscopy showed biphasic scaffolds could support the attachment and spreading of human mesenchymal stem cells from bone marrow (hMSC-BM). These promising results highlight the potential utilization of this novel scaffold for osteochondral tissue regeneration as well as highlighting the potential of infilling silk materials within 3D printed scaffolds to further increase their versatility.

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.

Hydrogel-Enhanced Autologous Chondrocyte Implantation for Cartilage Regeneration-An Update on Preclinical Studies

Autologous chondrocyte implantation (ACI) and matrix-induced ACI (MACI) have demonstrated improved clinical outcomes and reduced revision rates for treating osteochondral and chondral defects. However, their ability to achieve lasting, fully functional repair remains limited. To overcome these challenges, scaffold-enhanced ACI, particularly utilizing hydrogel-based biomaterials, has emerged as an innovative strategy. These biomaterials are intended to mimic the biological composition, structural organization, and biomechanical properties of native articular cartilage. This review aims to provide comprehensive and up-to-date information on advancements in hydrogel-enhanced ACI from the past decade. We begin with a brief introduction to cartilage biology, mechanisms of cartilage injury, and the evolution of surgical techniques, particularly looking at ACI. Subsequently, we review the diversity of hydrogel scaffolds currently undergoing development and evaluation in preclinical studies for articular cartilage regeneration, emphasizing chondrocyte-laden hydrogels applicable to ACI. Finally, we address the key challenges impeding effective clinical translation, with particular attention to issues surrounding fixation and integration, aiming to inform and guide the future progression of tissue engineering strategies.

Biocomposite Scaffolds for Tissue Engineering: Materials, Fabrication Techniques and Future Directions

Tissue engineering is an interdisciplinary field that combines materials, methods, and biological molecules to engineer newly formed tissues to replace or restore functional organs. Biomaterials-based scaffolds play a crucial role in developing new tissue by interacting with human cells. Tissue engineering scaffolds with ideal characteristics, namely, nontoxicity, biodegradability, and appropriate mechanical and surface properties, are vital for tissue regeneration applications. However, current biocomposite scaffolds face significant limitations, particularly in achieving structural durability, controlled degradation rates, and effective cellular integration. These qualities are essential for maintaining long-term functionality in vivo. Although commonly utilized biomaterials can provide physical and chemical properties needed for tissue regeneration, inadequate biomimetic properties, as well as insufficient interactions of cells-scaffolds interaction, still need to be improved for the application of tissue engineering in vivo. It is impossible to achieve some essential features using a single material, so combining two or more materials may accomplish the requirements. In order to achieve a proper scaffold design, a suitable fabrication technique and combination of biomaterials with controlled micro or nanostructures are needed to achieve the proper biological responses. This review emphasizes advancements in scaffold durability, biocompatibility, and cellular responsiveness. It focuses on natural and synthetic polymer combinations and innovative fabrication techniques. Developing stimulus-responsive 3D scaffolds is critical, as these scaffolds enhance cell adhesion and promote functional tissue formation while maintaining structural integrity over time. This review also highlights the natural polymers, smart materials, and recent advanced techniques currently used to create emerging scaffolds for tissue regeneration applications.

Optimizing scaffold pore size for tissue engineering: insights across various tissue types

Scaffold porosity is a critical factor in replicating the complex in vivo microenvironment, directly influencing cellular interactions, migration, nutrient transfer, vascularization, and the formation of functional tissues. For optimal tissue formation, scaffold design must account for various parameters, including material composition, morphology, mechanical properties, and cellular compatibility. This review highlights the importance of interconnected porosity and pore size, emphasizing their impact on cellular behavior and tissue formation across several tissue engineering domains, such as skin, bone, cardiovascular, and lung tissues. Specific pore size ranges enhance scaffold functionality for different tissues: small pores (∼1-2 µm) aid epidermal cell attachment in skin regeneration, moderate pores (∼2-12 µm) support dermal migration, and larger pores (∼40-100 µm) facilitate vascular structures. For bone tissue engineering, multi-layered scaffolds with smaller pores (50-100 µm) foster cell attachment, while larger pores (200-400 µm) enhance nutrient diffusion and angiogenesis. Cardiovascular and lung tissues benefit from moderate pore sizes (∼25-60 µm) to balance cell integration and nutrient diffusion. By addressing critical design challenges and optimizing pore size distributions, this review provides insights into scaffold innovations, ultimately advancing tissue regeneration strategies.

Fabrication and performance of Zinc-based biodegradable metals: From conventional processes to laser powder bed fusion

Zinc (Zn)-based biodegradable metals (BMs) fabricated through conventional manufacturing methods exhibit adequate mechanical strength, moderate degradation behavior, acceptable biocompatibility, and bioactive functions. Consequently, they are recognized as a new generation of bioactive metals and show promise in several applications. However, conventional manufacturing processes face formidable limitations for the fabrication of customized implants, such as porous scaffolds for tissue engineering, which are future direction towards precise medicine. As a metal additive manufacturing technology, laser powder bed fusion (L-PBF) has the advantages of design freedom and formation precision by using fine powder particles to reliably fabricate metallic implants with customized structures according to patient-specific needs. The combination of Zn-based BMs and L-PBF has become a prominent research focus in the fields of biomaterials as well as biofabrication. Substantial progresses have been made in this interdisciplinary field recently. This work reviewed the current research status of Zn-based BMs manufactured by L-PBF, covering critical issues including powder particles, structure design, processing optimization, chemical compositions, surface modification, microstructure, mechanical properties, degradation behaviors, biocompatibility, and bioactive functions, and meanwhile clarified the influence mechanism of powder particle composition, structure design, and surface modification on the biodegradable performance of L-PBF Zn-based BM implants. Eventually, it was closed with the future perspectives of L-PBF of Zn-based BMs, putting forward based on state-of-the-art development and practical clinical needs.

Photobiomodulation associated with alginate-based engineered tissue on promoting chondrocytes-derived biological responses for cartilage regeneration

Articular cartilage is a connective tissue with limited self-healing potential, frequently affected by trauma and degenerative changes, leading to osteoarthritis. Photobiomodulation paired with engineered tissue can improve cartilage's poor intrinsic healing and overcome its restricted self-regeneration. In this study, alginate-based scaffolds were fabricated with varying concentrations of CaCl₂ to achieve optimal mechanical, biocompatible, and biodegradable properties. The fluence-dependence of near-infrared (NIR) laser irradiation (830 nm) on chondrocyte viability and proliferation was investigated in a 2D environment across fluences (2.5-10 J/cm2). Optimal conditions of 3 % w/v CaCl₂ and 5 J/cm2 were identified to construct alginate scaffolds and promote chondrocyte growth in 2D and 3D cultures. Single PBM (830 nm, 5 J/cm2) further exhibited a significant relative intensity of collagen type II immunostaining and stimulation of Col2a1 expression in 2D culture. Multiple PBM sessions (830 nm, 5 J/cm2) significantly enhanced chondrocyte proliferation and glycosaminoglycan production in alginate scaffolds, with a protocol of one session every four days being the most effective. Scanning electron microscopy revealed PBM-induced secretory granule formation, corresponding to a significant increase in extracellular vesicle release. Consequently, integrating PBM and alginate-based scaffolds is a promising technique for accelerating and optimizing cartilage regeneration, with potential application in tissue engineering.

Polymer scaffolds delineate healthy from diseased states at sites distal from the pancreas in two models of type 1 diabetes

Type 1 diabetes (T1D) prevention is currently limited by the lack of diagnostic tools able to identify disease before autoimmune destruction of the pancreatic β cells. Autoantibody tests are used to predict risk and, in combination with glucose dysregulation indicative of β cell loss, to determine administration of immunotherapies. Our objective was to remotely identify immune changes associated with the disease, and we have employed a subcutaneously implanted microporous poly(e-caprolactone) (PCL) scaffold to function as an immunological niche (IN) in two models of T1D. Biopsy and analysis of the IN enables disease monitoring using transcriptomic changes at a distal site from autoimmune destruction of the pancreas, thereby gaining cellular level information about disease without the need for a biopsy of the native organ. Using this approach, we identified gene signatures that stratify healthy and diseased mice in both an adoptive transfer model and a spontaneous onset model of T1D. The gene signatures identified herein demonstrate the ability of the IN to identify immune activation associated with diabetes across models.

An Easy-to-Handle Route for Bicomponent Porous Tubes Fabrication as Nerve Guide Conduits

Over the past two decades, the development of nerve guide conduits (NGCs) has gained much attention due to the impellent need to find innovative strategies to take care of damaged or degenerated peripheral nerves in clinical surgery. In this view, significant effort has been spent on the development of high-performance NGCs by different materials and manufacturing approaches. Herein, a highly versatile and easy-to-handle route to process 3D porous tubes made of chitosan and gelatin to be used as a nerve guide conduit were investigated. This allowed us to fabricate highly porous substrates with a porosity that ranged from 94.07 ± 1.04% to 97.23 ± 1.15% and average pore sizes-estimated via X-ray computed tomography (XCT) reconstruction and image analysis-of hundreds of microns and an irregular shape with an aspect ratio that ranged from 0.70 ± 0.19 to 0.80 ± 0.15 as a function of the chitosan/gelatin ratio. More interestingly, the addition of gelatin allowed us to modulate the mechanical properties, which gradually reduced the stiffness-max strength from 0.634 ± 0.015 MPa to 0.367 ± 0.021 MPa-and scaffold toughness-from 46.2 kJ/m3 to 14.0 kJ/m3-as the gelatin content increased. All these data fall into the typical ranges of the morphological and mechanical parameters of currently commercialized NGC products. Preliminary in vitro studies proved the ability of 3D porous tubes to support neuroblastoma cell (SH-SY5Y) adhesion and proliferation. In perspective, the proposed approach could also be easily implemented with the integration of other processing techniques (e.g., electrospinning) for the design of innovative bi-layered systems with an improved cell interface and molecular transport abilities.

Development of Bioinspired Biphasic Calcium Phosphate Inks for Manufacturing Bone Scaffolds by Robocasting

Robocasting calcium phosphate compounds as a novel approach to creating customized structures with interconnected pores not only overcomes the limitations of traditional fabrication methods of calcium phosphate substitutes but also boosts the potential for bone tissue regeneration. The ink development is a key step in 3D printing. In this study, different inks consisting of magnesium- and sodium-doped carbonated hydroxyapatite, β-tricalcium phosphate, and Pluronic F-127 were prepared to design biomimetic bone scaffolds. To achieve suitable printability and subsequently, structures with high shape fidelity and appropriate mechanical properties, the selected compositions were evaluated by rheological analysis and mechanical tests. The results demonstrated that the prepared inks exhibited shear thinning behavior, and by increasing the concentration of Pluronic and biphasic calcium phosphate (BCP), more consistent gels were obtained that were able to maintain their shape after printing. The compressive strength of the scaffolds varied in the range of ∼8-60 MPa. The morphology of the sintered scaffolds in the scanning electron microscopy images also showed a dual macro- and micropore-size architecture, which can promote the adhesion of proteins and cell behavior. Our findings indicated that bioinspired BCP scaffolds can be fabricated with relatively high precision for use as cancellous bone substitutes.

In-vitro and in-vivo evaluation of angiogenic potential of a novel lithium chloride loaded silk fibroin / alginate 3D porous scaffold with antibacterial activity, for promoting diabetic wound healing

Healing diabetic ulcers with chronic inflammation is a major challenge for researchers and professionals, necessitating new strategies. To rapidly treat diabetic wounds in rat models, we have fabricated a composite scaffold composed of alginate (Alg) and silk fibroin (SF) as a wound dressing that is laden with molecules of lithium chloride (LC). The physicochemical, bioactivity, and biocompatibility properties of Alg-SF-LC scaffolds were investigated in contrast to those of Alg, SF, and Alg-SF ones. Afterward, full-thickness wounds were ulcerated in diabetic rats in order to evaluate the capacity of LC-laden scaffolds to regenerate skin. The characterization findings demonstrated that the composite scaffolds possessed favorable antibacterial properties, cell compatibility, high swelling, controlled degradability, and good uniformity in the interconnected pore microstructure. Additionally, in terms of wound contraction, re-epithelialization, and angiogenesis improvement, LC-laden scaffolds revealed better performance in diabetic wound healing than the other groups. This research indicates that utilizing lithium chloride molecules loaded in biological materials supports the best diabetic ulcer regeneration in vivo, and produces a skin replacement with a cellular structure comparable to native skin.

Theranostic Applications of Scaffolds in Current Biomedical Research

Theranostics, a remarkable combination of diagnostics and therapeutics, has given rise to tissue/organ-format theranostic scaffolds that integrate targeted therapy and real-time disease monitoring. The scaffold is a 3D structuring template for cell or tissue attachment and growth. These scaffolds offer unprecedented opportunities for personalized medicine and hold great potential for revolutionizing healthcare. Recent advancements in fabrication techniques have enabled the creation of highly intricate and precisely engineered scaffolds with controllable physical and chemical properties, enhancing their therapeutic potential for tissue engineering and regenerative medicine. This paper proposes a new categorization method for scaffolds in tissue engineering based on the relativity of scaffold design-independent parameters. Five types of scaffolds are defined at different levels, highlighting the importance of understanding and analyzing scaffold types. It possesses the ability to seamlessly integrate diagnostics and therapeutics within a single platform, enhancing the efficacy and precision of personalized medicine. Natural scaffolds derived from biomaterials and synthetic scaffolds fabricated by human intervention are discussed, with synthetic scaffolds offering advantages such as tunable mechanical properties and controlled drug delivery, while natural scaffolds provide inherent biocompatibility and bioactivity, making them ideal for promoting cellular responses. The use of synthetic scaffolds shows great promise in advancing regenerative medicine and improving patient outcomes. The transfer of new technologies and changes in society have accelerated the evolution of health monitoring into the era of personal health monitoring. Using emerging health data, cost-effective analytics, wireless sensor networks, mobile smartphones, and easy internet access, the combination of these technologies is expected to accelerate the transition to personal health monitoring outside of traditional healthcare settings. The main objective of this review article is to provide a comprehensive overview of the theranostic applications of scaffolds in current biomedical research, highlighting their dual role in therapy and diagnostics. The review aims to explore the latest advancements in scaffold design, fabrication, and functionalization, emphasizing how these innovations contribute to improved therapeutic efficacy, targeted drug delivery, and the real-time monitoring of disease progression across various medical fields.

Morphological, sterical, and localized thermodynamics in the adsorption of CO2 by activated biocarbon from the white rot fungi Trametes gibbosa

The capture of CO2 by biochar has recently become one of the cornerstones of circular economy models for a sustainable society. In this work, we synthesized an activated biocarbon using Trametes gibbosa (BioACTG) in a one-step synthesis. We investigated CO2 adsorption mechanisms under five different temperatures using a statistical physics approach. The data was better represented by the multilayer model with two distinguished energies, providing more accurate values for the estimated parameters. According to the number of carbon dioxide molecules per site (n) and the densities of the receptor sites (Dzif), the tendency to form a second layer increased as the temperature increased. The adsorption of CO2 on BioACTG was exothermic (the values of Qasat = 15.5 mmol/g at 273 K decrease to 10.5 mmol/g at 353 K), and the temperature influenced CO2 as well as the morphological features of the process. A computational approach was used to investigate the electronic properties of the adsorbate, showing that its lowest unoccupied orbital (LUMO) heavily contributed to the high efficiency of the process which was ruled by pore diffusion mechanisms driven by energetic fluctuations. Other molecules present in CO2-rich mixtures were also investigated, showing that their concentration limited their competitiveness with CO2.

In Vitro Evaluation of Cellular Interactions with Nanostructured Spheres of Alginate and Zinc-Substituted Carbonated Hydroxyapatite

The increasing demand for effective bone regeneration materials drives the exploration of biomaterials with enhanced bioactivity and biocompatibility, such as zinc-substituted compounds. This study investigates the in vitro cellular interactions with nanostructured spheres composed of alginate/carbonated hydroxyapatite (CHA), compared to zinc-substituted CHA (ZnCHA). This work aimed to compare the physicochemical properties and biological effects of ZnCHA and CHA on osteoblasts. ZnCHA was synthesized using a wet chemical method, followed by characterization through X-ray diffraction, Fourier transform infrared spectroscopy, total organic carbon analysis, Wavelength-dispersive X-ray spectroscopy, and BET surface area analysis to assess ion release and structural changes. Biological evaluation was conducted using cell viability, proliferation, and biomineralization assays on osteoblasts. Results showed successful incorporation of zinc and carbonate, leading to reduced crystallinity and increased surface area. Cell viability and proliferation assays indicated ZnCHA's cytocompatibility and enhanced osteoblastic activity, with increased mineralization nodules compared to CHA samples. The study concludes that ZnCHA composites are promising candidates for bone tissue engineering, demonstrating improved cytocompatibility and potential for further preclinical evaluations.

Characterization of a decellularized pericardium extracellular matrix hydrogel for regenerative medicine: insights on animal-to-animal variability

In the past years, the use of hydrogels derived from decellularized extracellular matrix (dECM) for regenerative medicine purposes has significantly increased. The intrinsic bioactive and immunomodulatory properties indicate these materials as promising candidates for therapeutical applications. However, to date, limitations such as animal-to-animal variability still hinder the clinical translation. Moreover, the choice of tissue source, decellularization and solubilization protocols leads to differences in dECM-derived hydrogels. In this context, detailed characterization of chemical, physical and biological properties of the hydrogels should be performed, with attention to how these properties can be affected by animal-to-animal variability. Herein, we report a detailed characterization of a hydrogel derived from the decellularized extracellular matrix of bovine pericardium (dBP). Protein content, rheological properties, injectability, surface microstructure, in vitro stability and cytocompatibility were evaluated, with particular attention to animal-to-animal variability. The gelation process showed to be thermoresponsive and the obtained dBP hydrogels are injectable, porous, stable up to 2 weeks in aqueous media, rapidly degrading in enzymatic environment and cytocompatible, able to maintain cell viability in human mesenchymal stromal cells. Results from proteomic analysis proved that dBP hydrogels are highly rich in composition, preserving bioactive proteoglycans and glycoproteins in addition to structural proteins such as collagen. With respect to the chemical composition, animal-to-animal variability was shown, but the biological properties were not affected, which remained consistent in different batches. Taken together these results show that dBP hydrogels are excellent candidates for regenerative medicine applications.

Harnessing extracellular vesicles-mediated signaling for enhanced bone regeneration: novel insights into scaffold design

The increasing prevalence of bone replacements and complications associated with bone replacement procedures underscores the need for innovative tissue restoration approaches. Existing synthetic grafts cannot fully replicate bone vascularization and mechanical characteristics. This study introduces a novel strategy utilizing pectin, chitosan, and polyvinyl alcohol to create interpenetrating polymeric network (IPN) scaffolds incorporated with extracellular vesicles (EVs) isolated from human mesenchymal stem cells (hMSCs). We assess the osteointegration and osteoconduction abilities of these modelsin vitrousing hMSCs and MG-63 osteosarcoma cells. Additionally, we confirm exosome properties through Transmission Electron Microscopy (TEM), immunoblotting, and Dynamic Light Scattering (DLS).In vivo, chick allantoic membrane assay investigates vascularization characteristics. The study did not includein vivoanimal experiments. Our results demonstrate that the IPN scaffold is highly porous and interconnected, potentially suitable for bone implants. EVs, approximately 100 nm in size, enhance cell survival, proliferation, alkaline phosphatase activity, and the expression of osteogenic genes. EVs-mediated IPN scaffolds demonstrate promise as precise drug carriers, enabling customized treatments for bone-related conditions and regeneration efforts. Therefore, the EVs-mediated IPN scaffolds demonstrate promise as precise carriers for the transport of drugs, allowing for customized treatments for conditions connected to bone and efforts in regeneration.

Preliminary study on the preparation of antler powder/chitosan/β-glycerophosphate sodium/polyvinyl alcohol porous hydrogel scaffolds and their osteogenic effects

Introduction: The production of bone-like structural scaffolds through bone tissue engineering technology is a promising method for bone regeneration to repair bone defects. Deer antler, an easily harvested and abundantly sourced initial bone tissue structure, resembles the composition and structure of human cancellous bone and can serve as a new material for allogeneic bone transplantation. Methods: This study involved the preparation and characterization of antler powder/chitosan/β-glycerophosphate sodium/polyvinyl alcohol (AP/CS/β-GP/PVA) porous hydrogel scaffolds to verify their material properties and osteogenic mechanisms. The microstructure, hydrophilicity, and mechanical properties of the scaffolds were studied using Scanning Electron Microscopy (SEM), contact angle measurement, and a universal material testing machine. The interactions between the various components were investigated using Fourier-Transform Infrared Spectroscopy (FTIR). Biocompatibility, osteogenic properties, and expression of osteogenesis-related proteins of the scaffolds were evaluated through Cell Counting Kit-8 (CCK-8) assays, alkaline phosphatase staining, Alizarin Red staining, live/dead cell staining, and Western blot analysis. Results: The results showed that as the content of deer antler powder increased, both the hydrophilicity and mechanical properties of the scaffold materials improved, while the porosity slightly decreased with an increase in deer antler powder content. Cell culture experiments demonstrated that scaffolds with a higher proportion of deer antler powder were beneficial for the proliferation and differentiation of mouse pre-osteoblast (MC3T3-E1) cells, with the scaffolds containing 10% and 8% deer antler powder showing the best effects. The upregulation of RUNX2, OCN, OSX, and OPN protein expression may promote differentiation. Discussion: Therefore, the AP/CS/β-GP/PVA hydrogel scaffolds have the potential to become a promising biomaterial for bone tissue engineering.

Fabrication of polymeric microspheres for biomedical applications

Polymeric microspheres (PMs) have attracted great attention in the field of biomedicine in the last several decades due to their small particle size, special functionalities shown on the surface and high surface-to-volume ratio. However, how to fabricate PMs which can meet the clinical needs and transform laboratory achievements to industrial scale-up still remains a challenge. Therefore, advanced fabrication technologies are pursued. In this review, we summarize the technologies used to fabricate PMs, including emulsion-based methods, microfluidics, spray drying, coacervation, supercritical fluid and superhydrophobic surface-mediated method and their advantages and disadvantages. We also review the different structures, properties and functions of the PMs and their applications in the fields of drug delivery, cell encapsulation and expansion, scaffolds in tissue engineering, transcatheter arterial embolization and artificial cells. Moreover, we discuss existing challenges and future perspectives for advancing fabrication technologies and biomedical applications of PMs.

Avastin-Loaded 3D-Printed Alginate Scaffold as an Effective Antiadhesive Barrier to Prevent Postsurgical Adhesion Bands Formation

Postoperative adhesion can cause complications, such as pain and organ blockage, in the abdominal regions. To address this issue, surgical techniques and antiadhesive treatments are applied. Given the significant role of vascularization in adhesion band formation, Avastin (Ava) that targets vascular endothelial growth factor (VEGF) can be applied to prevent peritoneal adhesion bands. Moreover, Alginate (Alg), a natural polysaccharide, is a promising physical barrier to prevent adhesion bands. Incorporating Ava into Alg hydrogel in a form of 3D-printed scaffold (Alg/Ava) has potential to suppress inflammation and angiogenesis, leading to reduce peritoneal adhesion bands. Following physical, morphological, and biocompatibility evaluations, the efficacy of Alg and Ava alone and their combination in Alg/Ava on the formation of postsurgical adhesions is evaluated. Upon confirming physical stability and sustained release of Ava, the Alg/Ava scaffold effectively diminishes both the extent and strength of adhesion bands. Histopathological examination shows that the reduction in fibrosis and inflammation is responsible for preventing adhesion bands by the Alg/Ava scaffold. Additionally, the cytokine assessment reveals that this is due to the inhibition in the secretion of VEGF and Interleukin 6 suppressing vascularization and inflammatory pathways. This study suggests that a 3D-printed Alg/Ava scaffold has great potential to prevent the postsurgical adhesion bands.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Chitosan-2D Nanomaterial-Based Scaffolds for Biomedical Applications

Chitosan (CS) and two-dimensional nanomaterial (2D nanomaterials)-based scaffolds have received widespread attention in recent times in biomedical applications due to their excellent synergistic potential. CS has garnered much attention as a biomedical scaffold material either alone or in combination with some other material due to its favorable physiochemical properties. The emerging 2D nanomaterials, such as black phosphorus (BP), molybdenum disulfide (MoS2), etc., have taken huge steps towards varying biomedical applications. However, the implementation of a CS-2D nanomaterial-based scaffold for clinical applications remains challenging for different reasons such as toxicity, stability, etc. Here, we reviewed different types of CS scaffold materials and discussed their advantages in biomedical applications. In addition, a different CS nanostructure, instead of a scaffold, has been described. After that, the importance of 2D nanomaterials has been elaborated on in terms of physiochemical properties. In the next section, the biomedical applications of CS with different 2D nanomaterial scaffolds have been highlighted. Finally, we highlighted the existing challenges and future perspectives of using CS-2D nanomaterial scaffolds for biomedical applications. We hope that this review will encourage a more synergistic biomedical application of the CS-2D nanomaterial scaffolds and their utilization clinical applications.

Synthesis and Physicochemical Characterization of Gelatine-Based Biodegradable Aerogel-like Composites as Possible Scaffolds for Regenerative Medicine

Regenerative medicine is an interdisciplinary field aiming at restoring pathologically damaged tissues and whole organs by cell transplantation in combination with proper supporting scaffolds. Gelatine-based ones are very attractive due to their biocompatibility, rapid biodegradability, and lack of immunogenicity. Gelatine-based composite hydrogels, containing strengthening agents to improve their modest mechanical properties, have been demonstrated to act as extracellular matrices (ECMs), thus playing a critical role in "organ manufacturing". Inspired by the lysyl oxidase (LO)-mediated process of crosslinking, which occurs in nature to reinforce collagen, we have recently developed a versatile protocol to crosslink gelatine B (Gel B) in the presence or absence of LO, using properly synthesized polystyrene- and polyacrylic-based copolymers containing the amine or aldehyde groups needed for crosslinking reactions. Here, following the developed protocol with slight modifications, we have successfully crosslinked Gel B in different conditions, obtaining eight out of nine compounds in high yield (57-99%). The determined crosslinking degree percentage (CP%) evidenced a high CP% for compounds obtained in presence of LO and using the styrenic amine-containing (CP5/DMAA) and acrylic aldehyde-containing (CPMA/DMAA) copolymers as crosslinking agents. ATR-FTIR analyses confirmed the chemical structure of all compounds, while optical microscopy demonstrated cavernous, crater-like, and labyrinth-like morphologies and cavities with a size in the range 15-261 µm. An apparent density in the range 0.10-0.45 g/cm3 confirmed the aerogel-like structure of most samples. Although the best biodegradation profile was observed for the sample obtained using 10% CP5/DMAA (M3), high swelling and absorption properties, high porosity, and good biodegradation profiles were also observed for samples obtained using the 5-10% CP5/DMAA (M4, 5, 6) and 20% CPMA/DMAA (M9) copolymers. Collectively, in this work of synthesis and physicochemical characterization, new aerogel-like composites have been developed and, based on their characteristics, which fit well within the requirements for TE, five candidates (M3, M4, M5, M6, and M9) suitable for future biological experiments on cell adhesion, infiltration and proliferation, to confirm their effective functioning, have been identified.

Decellularized Bovine Skeletal Muscle Scaffolds: Structural Characterization and Preliminary Cytocompatibility Evaluation

Skeletal muscle degeneration is responsible for major mobility complications, and this muscle type has little regenerative capacity. Several biomaterials have been proposed to induce muscle regeneration and function restoration. Decellularized scaffolds present biological properties that allow efficient cell culture, providing a suitable microenvironment for artificial construct development and being an alternative for in vitro muscle culture. For translational purposes, biomaterials derived from large animals are an interesting and unexplored source for muscle scaffold production. Therefore, this study aimed to produce and characterize bovine muscle scaffolds to be applied to muscle cell 3D cultures. Bovine muscle fragments were immersed in decellularizing solutions for 7 days. Decellularization efficiency, structure, composition, and three-dimensionality were evaluated. Bovine fetal myoblasts were cultured on the scaffolds for 10 days to attest cytocompatibility. Decellularization was confirmed by DAPI staining and DNA quantification. Histological and immunohistochemical analysis attested to the preservation of main ECM components. SEM analysis demonstrated that the 3D structure was maintained. In addition, after 10 days, fetal myoblasts were able to adhere and proliferate on the scaffolds, attesting to their cytocompatibility. These data, even preliminary, infer that generated bovine muscular scaffolds were well structured, with preserved composition and allowed cell culture. This study demonstrated that biomaterials derived from bovine muscle could be used in tissue engineering.

Slow and steady wins the race: Fractionated near-infrared treatment empowered by graphene-enhanced 3D scaffolds for precision oncology

Surgically addressing tumors poses a challenge, requiring a tailored, multidisciplinary approach for each patient based on the unique aspects of their case. Innovative therapeutic regimens combined to reliable reconstructive methods can contribute to an extended patient's life expectancy. This study presents a detailed comparative investigation of near-infrared therapy protocols, examining the impact of non-fractionated and fractionated irradiation regimens on cancer treatment. The therapy is based on the implantation of graphene oxide/poly(lactic-co-glycolic acid) three-dimensional printed scaffolds, exploring their versatile applications in oncology by the examination of pro-inflammatory cytokine secretion, immune response, and in vitro and in vivo tumor therapy. The investigation into cell death patterns (apoptosis vs necrosis) underlines the pivotal role of protocol selection underscores the critical influence of treatment duration on cell fate, establishing a crucial parameter in therapeutic decision-making. In vivo experiments corroborated the profound impact of protocol selection on tumor response. The fractionated regimen emerged as the standout performer, achieving a substantial reduction in tumor size over time, surpassing the efficacy of the non-fractionated approach. Additionally, the fractionated regimen exhibited efficacy also in targeting tumors in proximity but not in direct contact to the scaffolds. Our results address a critical gap in current research, highlighting the absence of a standardized protocol for optimizing the outcome of photodynamic therapy. The findings underscore the importance of personalized treatment strategies in achieving optimal therapeutic efficacy for precision cancer therapy.

Carboxymethyl cellulose-agarose hydrogel in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanofibers: A novel tissue engineered skin graft

Healing chronic and critical-sized full-thickness wounds is a major challenge in the healthcare sector. Scaffolds prepared using electrospinning and hydrogels serve as effective treatment options for wound healing by mimicking the native skin microenvironment. Combining synthetic nanofibers with tunable hydrogel properties can effectively overcome limitations in skin scaffolds made only with nanofibers or hydrogels. In this study, a biocompatible hybrid scaffold was developed for wound healing applications using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibers embedded with hydrogel made of 2 % carboxymethyl cellulose (CMC) blended with 1 % agarose. Hybrid scaffolds, characterized for surface morphology, swellability, porosity, and degradation, were found to be suitable for wound healing. Furthermore, the incorporation of CMC-agarose hydrogel into nanofibers significantly enhanced their mechanical strength compared to PHBV nanofibers alone (p < 0.05). Extract cytotoxicity and direct cytotoxicity tests showed that the hybrid scaffolds developed in this study are cytocompatible (>75 % viability). Furthermore, human adult dermal fibroblasts (HDFa) and human adult immortalized keratinocytes (HaCaT) adhesion, viability, and proliferation studies revealed that the hybrid scaffolds exhibited a significant increase in cell proliferation over time, similar to PHBV nanofibers. Finally, the developed hybrid scaffolds were evaluated in rat full-thickness wounds, demonstrating their ability to promote full-thickness wound healing with reepithelialization and epidermis closure.

Mesenchymal stem cell therapy in diabetic foot ulcer: An updated comprehensive review

Background

Diabetes has evolved into a worldwide public health issue. One of the most serious complications of diabetes is diabetic foot ulcer (DFU), which frequently creates a significant financial strain on patients and lowers their quality of life. Up until now, there has been no curative therapy for DFU, only symptomatic relief or an interruption in the disease's progression. Recent studies have focused attention on mesenchymal stem cells (MSCs), which provide innovative and potential treatment candidates for several illnesses as they can differentiate into various cell types. They are mostly extracted from the placenta, adipose tissue, umbilical cord (UC), and bone marrow (BM). Regardless of their origin, they show comparable features and small deviations. Our goal is to investigate MSCs' therapeutic effects, application obstacles, and patient benefit strategies for DFU therapy.

Methodology

A comprehensive search was conducted using specific keywords relating to DFU, MSCs, and connected topics in the databases of Medline, Scopus, Web of Science, and PubMed. The main focus of the selection criteria was on English-language literature that explored the relationship between DFU, MSCs, and related factors.

Results and Discussion

Numerous studies are being conducted and have demonstrated that MSCs can induce re-epithelialization and angiogenesis, decrease inflammation, contribute to immunological modulation, and subsequently promote DFU healing, making them a promising approach to treating DFU. This review article provides a general snapshot of DFU (including clinical presentation, risk factors and etiopathogenesis, and conventional treatment) and discusses the clinical progress of MSCs in the management of DFU, taking into consideration the side effects and challenges during the application of MSCs and how to overcome these challenges to achieve maximum benefits.

Conclusion

The incorporation of MSCs in the management of DFU highlights their potential as a feasible therapeutic strategy. Establishing a comprehensive understanding of the complex relationship between DFU pathophysiology, MSC therapies, and related obstacles is essential for optimizing therapy outcomes and maximizing patient benefits.

3D-bioprinted alginate-based bioink scaffolds with β-tricalcium phosphate for bone regeneration applications

Background/purpose

3D-printed bone tissue engineering is becoming recognized as a key approach in dentistry for creating customized bone regeneration treatments fitting patients bone defects requirements. 3D bioprinting offers an innovative method to fabricate detailed 3D structures, closely emulating the native bone micro-environment and better bone regeneration. This study aimed to develop an 3D-bioprintable scaffold using a combination of alginate and β-tricalcium phosphate (β-TCP) with the Cellink® BioX printer, aiming to advance the field of tissue engineering.

Materials and methods

The physical and biological properties of the resulting 3D-printed scaffolds were evaluated at 10 %, 12 %, and 15 % alginate combined with 10 % β-TCP. The scaffolds were characterized through printability, swelling behavior, degradability, and element analysis. The biological assessment included cell viability, alkaline phosphatase (ALP) activity.

Results

10 % alginate/β-TCP 3D printed at 25 °C scaffold demonstrated the optimal condition for printability, swelling capability, and degradability of cell growth and nutrient diffusion. Addition of β-TCP particles significantly improved the 3D printed material viscosity over only alginate (P < 0.05). 10 % alginate/β-TCP enhanced MG-63 cell's proliferation (P < 0.05) and alkaline phosphatase activity (P < 0.001).

Conclusion

This study demonstrated in vitro that 10 % alginate/β-TCP bioink characteristic for fabricating 3D acellular bioprinted scaffolds was the best approach. 10 % alginate/β-TCP bioink 3D-printed scaffold exhibited superior physical properties and promoted enhanced cell viability and alkaline phosphatase activity, showing great potential for personalized bone regeneration treatments.

Physically cross-linked scaffold composed of hydroxyapatite-chitosan-alginate-polyamide has potential to trigger bone regeneration in craniofacial defect

Recently, the fabrication of a scaffold from biomaterials has been increased due to the lack of adequate natural bone for grafting. In this study, hydroxyapatite-chitosan-alginate-polyamide (HCAP) synthetic scaffold was fabricated using the thermally induced phase separation (TIPS) technique. The scaffold was cross-linked with either a chemical cross-linker (calcium chloride, 2-hydroxyethyl methacrylate (HEMA), or glutaraldehyde (GTA)) or a physical cross-linker (gamma irradiation (IR)) resulting in scaffolds HCAP-CaCl2, HCAP-HEMA, HCAP-GTA, and HCAP-IR, respectively. The cross-linked scaffolds were characterized based on physicochemical properties, cytotoxicity, and biocompatibility. HCAP-GTA showed the highest density and the lowest swelling ratio and biodegradation rate closely matching with those of the HCAP-IR. Porosity and density of the HCAP, HCAP-IR, and HCAP-GTA scaffolds were 92.14, 87.26, and 83.33 %, and 0.241, 0.307, and 0.335 g/cm3, respectively. The swelling ratio for the same scaffolds was 149, 110, and 108 % after 72 h of observation. Brine shrimp cytotoxicity and RBC biocompatibility assay confirmed the non-toxic nature of HCAP-IR and HCAP-GTA scaffolds. The HCAP-IR scaffold was tested for bone regeneration in the rabbit mandible defect model. Histological analysis revealed the regeneration of new bone and restoration of bone defect at the site of injury. These findings indicate that radiation induced physically cross-linked HCAP scaffold could be used as an alternative in bone defect replacement therapy.

Reasoning on Pore Terminology in 3D Bioprinting

Terminology is pivotal for facilitating clear communication and minimizing ambiguity, especially in specialized fields such as chemistry. In materials science, a subset of chemistry, the term "pore" is traditionally linked to the International Union of Pure and Applied Chemistry (IUPAC) nomenclature, which categorizes pores into "micro", "meso", and "macro" based on size. However, applying this terminology in closely-related areas, such as 3D bioprinting, often leads to confusion owing to the lack of consensus on specific definitions and classifications tailored to each field. This review article critically examines the current use of pore terminology in the context of 3D bioprinting, highlighting the need for reassessment to avoid potential misunderstandings. We propose an alternative classification that aligns more closely with the specific requirements of bioprinting, suggesting a tentative size-based division of interconnected pores into 'parvo'-(d < 25 µm), 'medio'-(25 < d < 100 µm), and 'magno'-(d > 100 µm) pores, relying on the current understanding of the pore size role in tissue formation. The introduction of field-specific terminology for pore sizes in 3D bioprinting is essential to enhance the clarity and precision of research communication. This represents a step toward a more cohesive and specialized lexicon that aligns with the unique aspects of bioprinting and tissue engineering.

Osteogenic Potential of Human Dental Pulp Stem Cells (hDPSCs) Growing on Poly L-Lactide-Co-Caprolactone and Hyaluronic Acid (HYAFF-11TM) Scaffolds

Bone tissue engineering using different scaffolds is a new therapeutic approach in regenerative medicine. This study explored the osteogenic potential of human dental pulp stem cells (hDPSCs) grown on a hydrolytically modified poly(L-lactide-co-caprolactone) (PLCL) electrospun scaffold and a non-woven hyaluronic acid (HYAFF-11™) mesh. The adhesion, immunophenotype, and osteogenic differentiation of hDPSCs seeded on PLCL and HYAFF-11™ scaffolds were analyzed. The results showed that PLCL and HYAFF-11™ scaffolds significantly supported hDPSCs adhesion; however, hDPSCs' adhesion rate was significantly higher on PLCL than on HYAFF-11™. SEM analysis confirmed good adhesion of hDPSCs on both scaffolds before and after osteogenesis. Alizarin red S staining showed mineral deposits on both scaffolds after hDPSCs osteogenesis. The mRNA levels of runt-related transcription factor 2 (Runx2), collagen type I (Coll-I), osterix (Osx), osteocalcin (Ocn), osteopontin (Opn), bone sialoprotein (Bsp), and dentin sialophosphoprotein (Dspp) gene expression and their proteins were higher in hDPSCs after osteogenic differentiation on both scaffolds compared to undifferentiated hDPSCs on PLCL and HYAFF-11™. These results showed that PLCL scaffolds provide a better environment that supports hDPSCs attachment and osteogenic differentiation than HYAFF-11™. The high mRNA of early osteogenic gene expression and mineral deposits observed after hDPSCs osteogenesis on a PLCL mat indicated its better impact on hDPSCs' osteogenic potential than that of HYAFF-11™, and hDPSC/PLCL constructs might be considered in the future as an innovative approach to bone defect repair.

Mesenchymal stem cells-based drug delivery systems for diabetic foot ulcer: A review

The complication of diabetes, which is known as diabetic foot ulcer (DFU), is a significant concern due to its association with high rates of disability and mortality. It not only severely affects patients’ quality of life, but also imposes a substantial burden on the healthcare system. In spite of efforts made in clinical practice, treating DFU remains a challenging task. While mesenchymal stem cell (MSC) therapy has been extensively studied in treating DFU, the current efficacy of DFU healing using this method is still inadequate. However, in recent years, several MSCs-based drug delivery systems have emerged, which have shown to increase the efficacy of MSC therapy, especially in treating DFU. This review summarized the application of diverse MSCs-based drug delivery systems in treating DFU and suggested potential prospects for the future research.

Development of Bioactive Scaffolds for Orthopedic Applications by Designing Additively Manufactured Titanium Porous Structures: A Critical Review

We overview recent findings achieved in the field of model-driven development of additively manufactured porous materials for the development of a new generation of bioactive implants for orthopedic applications. Porous structures produced from biocompatible titanium alloys using selective laser melting can present a promising material to design scaffolds with regulated mechanical properties and with the capacity to be loaded with pharmaceutical products. Adjusting pore geometry, one could control elastic modulus and strength/fatigue properties of the engineered structures to be compatible with bone tissues, thus preventing the stress shield effect when replacing a diseased bone fragment. Adsorption of medicals by internal spaces would make it possible to emit the antibiotic and anti-tumor agents into surrounding tissues. The developed internal porosity and surface roughness can provide the desired vascularization and osteointegration. We critically analyze the recent advances in the field featuring model design approaches, virtual testing of the designed structures, capabilities of additive printing of porous structures, biomedical issues of the engineered scaffolds, and so on. Special attention is paid to highlighting the actual problems in the field and the ways of their solutions.

Synergistic effect of chitosan-alginate composite hydrogel enriched with ascorbic acid and alpha-tocopherol under hypoxic conditions on the behavior of mesenchymal stem cells for wound healing

BACKGROUND

In regenerative medicine, especially skin tissue engineering, the focus is on enhancing the quality of wound healing. Also, several constructs with different regeneration potentials have been used for skin tissue engineering. In this study, the regenerative properties of chitosan-alginate composite hydrogels in skin wound healing under normoxic and hypoxic conditions were investigated in vitro.

METHODS

The ionic gelation method was used to prepare chitosan/alginate (CA) hydrogel containing CA microparticles and bioactive agents [ascorbic acid (AA) and α-tocopherol (TP)]. After preparing composite hydrogels loaded with AA and TP, the physicochemical properties such as porosity, pore size, swelling, weight loss, wettability, drug release, and functional groups were analyzed. Also, the hemo-biocompatibility of composite hydrogels was evaluated by a hemolysis test. Then, the rat bone marrow mesenchymal stem cells (rMSCs) were seeded onto the hydrogels after characterization by flow cytometry. The survival rate was analyzed using MTT assay test. The hydrogels were also investigated by DAPI and H&E staining to monitor cell proliferation and viability. To induce hypoxia, the cells were exposed to CoCl2. To evaluate the regenerative potential of rMSCs cultured on CA/AA/TP hydrogels under hypoxic conditions, the expression of the main genes involved in the healing of skin wounds, including HIF-1α, VEGF-A, and TGF-β1, was investigated by real-time PCR.

RESULTS

The results demonstrated that the prepared composite hydrogels were highly porous, with interconnected pores that ranged in sizes from 20 to 188 μm. The evaluation of weight loss showed that the prepared hydrogels have the ability to biodegrade according to the goals of wound healing. The reduction percentage of CA/AA/TP mass in 21 days was reported as 21.09 ± 0.52%. Also, based on wettability and hemolysis tests of the CA/AA/TP, hydrophilicity (θ = 55.6° and 53.7°) and hemocompatibility with a hemolysis ratio of 1.36 ± 0.19 were evident for them. Besides, MTT assay, DAPI, and H&E staining also showed that the prepared hydrogels provide a suitable substrate for cell growth and proliferation. Finally, based on real-time PCR, increased expression levels of VEGF and TGF-β1 were observed in rMSCs in hypoxic conditions cultured on the prepared hydrogels.

CONCLUSIONS

In conclusion, this study provides evidence that 3D CA/AA/TP composite hydrogels seeded by rMSCs in hypoxic conditions have great potential to improve wound healing.

Role and architectural significance of porous chitosan-based scaffolds in bone tissue engineering

In designing and fabricating scaffolds to fill the bone defects and stimulate new bone formation, the biomimetics of the construct is a crucial factor in invoking the bone microenvironment to promote osteogenic differentiation. Regarding structural traits, changes in porous characteristics of the scaffolds, such as pore size, pore morphology, and percentage porosity, may patronize or jeopardize their other physicochemical and biological properties. Chitosan (CS), a biodegradable naturally occurring polymer, has recently drawn considerable attention as a scaffolding material in tissue engineering and regenerative medicine. CS-based microporous scaffolds have been reported to aid osteogenesis under both in vitro and in vivo conditions by supporting cellular attachment and proliferation of osteoblast cells and the formation of mineralized bone matrix. This related notion may be found in numerous earlier research, even though the precise mechanism of action that encourages the development of new bone still needs to be understood completely. This article presents the potential correlations and the significance of the porous properties of the CS-based scaffolds to influence osteogenesis and angiogenesis during bone regeneration. This review also goes over resolving the mechanical limitations of CS by blending it with other polymers and ceramics.