Construction of bionic tissue engineering cartilage scaffold based on three-dimensional printing and oriented frozen technology

Strategies to engineer articular cartilage with biomimetic zonal features: a review

Articular cartilage (AC) is a highly specialized tissue with restricted ability for self-regeneration, given its avascular and acellular nature. Although a considerable number of surgical treatments is available for the repair, reconstruction, and regeneration of AC defects, most of them do not prioritize the development of engineered cartilage with zonal stratification derived from biomimetic biochemical, biomechanical and topographic cues. In the absence of these zonal elements, engineered cartilage will exhibit increased susceptibility to failure and will neither be able to withstand the mechanical loading to which AC is subjected nor will it integrate well with the surrounding tissue. In this regard, new breakthroughs in the development of hierarchical stratified engineered cartilage are highly sought after. Initially, this review provides a comprehensive analysis of the composition and zonal organization of AC, aiming to enhance our understanding of the significance of the structure of AC for its function. Next, we direct our attention towards the existing in vitro and in vivo studies that introduce zonal elements in engineered cartilage to elicit appropriate AC regeneration by employing tissue engineering strategies. Finally, the advantages, challenges, and future perspectives of these approaches are presented.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

Azithromycin-carrying and microtubule-orientated biomimetic poly (lactic-co-glycolic acid) scaffolds for eyelid reconstruction

Introduction

Tarsal plate repair is the major challenge of eyelid reconstruction for the oculoplastic surgeon. The ideal synthetic tarsal plate substitute should imitate the microstructure and mechanical strength of the natural eyelid. The aim of this work was to develop a novel bionic substitute for eyelid reconstruction.

Methods

Three types of poly(lactic-co-glycolic acid) (PLGA) scaffolds (random, oriented, and azithromycin-loaded oriented scaffolds) were prepared using an improved thermal-induced phase separation technique. The microstructure of the scaffolds was examined by scanning electron microscopy. In vitro cytotoxicity was assessed using scaffold extracts. Fibroblast and primary rat meibomian gland epithelial cells (rMGCs) were cultured within the scaffolds, and their behavior was observed using fluorescence staining. Three types of PLGA scaffolds were implanted into rabbit eyelid defect in vivo to evaluate their inductive tissue repair function.

Results

We successfully fabricated three types of PLGA scaffolds with varying pore architectures, and the axially aligned scaffold demonstrated interconnected and vertically parallel channels. In vitro cytotoxicity tests using scaffold extracts revealed no apparent cytotoxicity. Fluorescence staining showed that both Fibroblast and rMGCs could adhere well onto the pore walls, with fibroblast elongating along the axially aligned porous structure. At 8 weeks post-implantation, all scaffolds were well integrated by fibrovascular tissue. The axially aligned scaffold groups exhibited faster degradation compared to the random scaffold group, with smaller fragments surrounded by mature collagen fibers.

Conclusion

The study found that the axially aligned scaffolds could well support and guide cellular activities in vitro and in vivo. Moreover, the axially aligned scaffold group showed a faster degradation rate with a matched integration rate compared to the random scaffold group. The findings suggest that the oriented scaffold is a promising alternative for eyelid tarsal plate substitutes.

Preparation and Use of Decellularized Extracellular Matrix for Tissue Engineering

The multidisciplinary fields of tissue engineering and regenerative medicine have the potential to revolutionize the practise of medicine through the abilities to repair, regenerate, or replace tissues and organs with functional engineered constructs. To this end, tissue engineering combines scaffolding materials with cells and biologically active molecules into constructs with the appropriate structures and properties for tissue/organ regeneration, where scaffolding materials and biomolecules are the keys to mimic the native extracellular matrix (ECM). For this, one emerging way is to decellularize the native ECM into the materials suitable for, directly or in combination with other materials, creating functional constructs. Over the past decade, decellularized ECM (or dECM) has greatly facilitated the advance of tissue engineering and regenerative medicine, while being challenged in many ways. This article reviews the recent development of dECM for tissue engineering and regenerative medicine, with a focus on the preparation of dECM along with its influence on cell culture, the modification of dECM for use as a scaffolding material, and the novel techniques and emerging trends in processing dECM into functional constructs. We highlight the success of dECM and constructs in the in vitro, in vivo, and clinical applications and further identify the key issues and challenges involved, along with a discussion of future research directions.

Development of a Two-Layer Porous Scaffold Based on Porcine Nasal Septal Cartilage for Orthopedics

The aim of the study was to design a construct based on a nasal septal cartilage plate providing required cell differentiation in different layers to replace a deep osteochondral defect and develop an algorithm of chemical and physical effect sequence to create non-immunogenic two-layer porous structure with requisite elasto-mechanical properties.

Regeneration potential of decellularized periodontal ligament cell sheets combined with 15-deoxy-Δ12,14-prostaglandin J2 nanoparticles in a rat periodontal defect

Periodontitis is a chronic inflammatory disease characterized by loss of attachment and destruction of the periodontium. Decellularized sheet, as an advanced tissue regeneration engineering biomaterial, has been researched and applied in many fields, but its effects on periodontal regeneration remain unclear. In this study, the biological properties of decellularized human periodontal ligament cell (dHPDLC) sheets were evaluated in vitro. Polycaprolactone/gelatin (PCL/GE) nanofibers were fabricated as a carrier to enhance the mechanical strength of the dHPDLC sheet. 15-deoxy-[Formula: see text]-prostaglandin J₂ (15d-PGJ₂) nanoparticles were added for anti-inflammation and regeneration improvement. For in vivo analysis, dHPDLC sheets combined with 15d-PGJ₂ nanoparticles, with or without PCL/GE, were implanted into rat periodontal defects. The periodontal regeneration effects were identified by microcomputed tomography (micro-CT) and histological staining, and immunohistochemistry. The results revealed that DNA content was reduced by 96.6%. The hepatocyte growth factor, vascular endothelial growth factor, and basic fibroblast growth factor were preserved but reduced. The expressions or distribution of collagen I and fibronectin were similar in dHPDLC and nondecellularized cell sheets. The dHPDLC sheets maintained the intact structure of the extracellular matrix. It could be recellularized by allogeneic human periodontal stem ligament cells and retain osteoinductive potential. Newly formed bone, cementum, and PDL were observed in dHPDLC sheets combined with 15d-PGJ₂ groups, with or without PCL/GE nanofibers, for four weeks post-operation in vivo. Bringing together all these points, this new construct of dHPDLC sheets can be a potential candidate for periodontal regeneration in an inflammatory environment of the oral cavity.

Recent advances in bioprinting technologies for engineering different cartilage-based tissues

Inadequate self-repair and regenerative efficiency of the cartilage tissues has motivated the researchers to devise advanced and effective strategies to resolve this issue. Introduction of bioprinting to tissue engineering has paved the way for fabricating complex biomimetic engineered constructs. In this context, the current review gears off with the discussion of standard and advanced 3D/4D printing technologies and their implications for the repair of different cartilage tissues, namely, articular, meniscal, nasoseptal, auricular, costal, and tracheal cartilage. The review is then directed towards highlighting the current stem cell opportunities. On a concluding note, associated critical issues and prospects for future developments, particularly in this sphere of personalized medicines have been discussed.

Advances and prospects in biomimetic multilayered scaffolds for articular cartilage regeneration

Due to the sophisticated hierarchical structure and limited reparability of articular cartilage (AC), the ideal regeneration of AC defects has been a major challenge in the field of regenerative medicine. As defects progress, they often extend from the cartilage layer to the subchondral bone and ultimately lead to osteoarthritis. Tissue engineering techniques bring new hope for AC regeneration. To meet the regenerative requirements of the heterogeneous and layered structure of native AC tissue, a substantial number of multilayered biomimetic scaffolds have been studied. Ideal multilayered scaffolds should generate zone-specific functional tissue similar to native AC tissue. This review focuses on the current status of multilayered scaffolds developed for AC defect repair, including design strategies based on the degree of defect severity and the zone-specific characteristics of AC tissue, the selection and composition of biomaterials, and techniques for design and manufacturing. The challenges and future perspectives of biomimetic multilayered scaffold strategies for AC regeneration are also discussed.

Bio-inspired hydrogel composed of hyaluronic acid and alginate as a potential bioink for 3D bioprinting of articular cartilage engineering constructs

Bioprinting is a promising tool to fabricate well-organized cell-laden constructs for repair and regeneration of articular cartilage. The selection of a suitable bioink, in terms of composition and mechanical properties, is crucial for the development of viable cartilage substitutes. In this study, we focused on the use of one of the main cartilage components, hyaluronic acid (HA), to design and formulate a new bioink for cartilage tissue 3D bioprinting. Major characteristics required for this application such as printability, biocompatibility, and biodegradability were analyzed. To produce cartilage constructs with optimal mechanical properties, HA-based bioink was co-printed with polylactic acid (PLA). HA-based bioink was found to improve cell functionality by an increase in the expression of chondrogenic gene markers and specific matrix deposition and, therefore, tissue formation. These results indicate that it is a promising bioink candidate for cartilage tissue engineering based in 3D bioprinting. STATEMENT OF SIGNIFICANCE: The recent appearance of 3D printing technology has enabled great advances in the treatment of osteochondral disorders by fabrication of cartilage tissue constructs that restore and/or regenerate damaged tissue. In this attempt, the selection of a suitable biomaterial, in terms of composition and mechanical properties, is crucial. In this study, we describe for first time the development of a bioink based on the main component of cartilage, HA, with suitable biological and mechanical properties, without involving toxic procedure, and its application  in cartilage tissue bioprinting. Hybrid constructs prepared by co-printing  this  bioink and thermoplastic polymer PLA provided an optimal niche for chondrocyte growth and maintenance as well as mechanical properties necessary to support load forces exerted in native tissue. We highlight the translation potential of this HA-based bioink in the clinical arena.

Biopolymers as bone substitutes: a review

Human bones have unique structures and characteristics, and replacing a natural bone in the case of bone fracture or bone diseases is a very complicated problem. The main goal of this paper was to summarize the recent research on polymer materials as bone substitutes and for bone repair. Bone treatment methods, bone substitute materials as well as their advantages and drawbacks, and manufacturing methods were reviewed. Biopolymers are the most promising materials in the field of artificial bones and using biopolymers with the shape memory effect can improve the integration of an artificial bone into the human body by better mimicking the structure and properties of natural bones, decreasing the invasiveness of surgical procedures by producing deployable implants. It has been shown that the application of the rapid prototyping technology for artificial bones allows the customization of bone substitutes for a patient and the creation of artificial bones with a complex structure.

3D Printing Technologies for Flexible Tactile Sensors toward Wearable Electronics and Electronic Skin

3D printing has attracted a lot of attention in recent years. Over the past three decades, various 3D printing technologies have been developed including photopolymerization-based, materials extrusion-based, sheet lamination-based, binder jetting-based, power bed fusion-based and direct energy deposition-based processes. 3D printing offers unparalleled flexibility and simplicity in the fabrication of highly complex 3D objects. Tactile sensors that emulate human tactile perceptions are used to translate mechanical signals such as force, pressure, strain, shear, torsion, bend, vibration, etc. into electrical signals and play a crucial role toward the realization of wearable electronics and electronic skin. To date, many types of 3D printing technologies have been applied in the manufacturing of various types of tactile sensors including piezoresistive, capacitive and piezoelectric sensors. This review attempts to summarize the current state-of-the-art 3D printing technologies and their applications in tactile sensors for wearable electronics and electronic skin. The applications are categorized into five aspects: 3D-printed molds for microstructuring substrate, electrodes and sensing element; 3D-printed flexible sensor substrate and sensor body for tactile sensors; 3D-printed sensing element; 3D-printed flexible and stretchable electrodes for tactile sensors; and fully 3D-printed tactile sensors. Latest advances in the fabrication of tactile sensors by 3D printing are reviewed and the advantages and limitations of various 3D printing technologies and printable materials are discussed. Finally, future development of 3D-printed tactile sensors is discussed.