Fabrication of 3D Printed Poly(lactic acid)/Polycaprolactone Scaffolds Using TGF-β1 for Promoting Bone Regeneration

Advantages of Using 3D Spheroid Culture Systems in Toxicological and Pharmacological Assessment for Osteogenesis Research

Bone differentiation is crucial for skeletal development and maintenance. Its dysfunction can cause various pathological conditions such as rickets, osteoporosis, osteogenesis imperfecta, or Paget's disease. Although traditional two-dimensional cell culture systems have contributed significantly to our understanding of bone biology, they fail to replicate the intricate biotic environment of bone tissue. Three-dimensional (3D) spheroid cell cultures have gained widespread popularity for addressing bone defects. This review highlights the advantages of employing 3D culture systems to investigate bone differentiation. It highlights their capacity to mimic the complex in vivo environment and crucial cellular interactions pivotal to bone homeostasis. The exploration of 3D culture models in bone research offers enhanced physiological relevance, improved predictive capabilities, and reduced reliance on animal models, which have contributed to the advancement of safer and more effective strategies for drug development. Studies have highlighted the transformative potential of 3D culture systems for expanding our understanding of bone biology and developing targeted therapeutic interventions for bone-related disorders. This review explores how 3D culture systems have demonstrated promise in unraveling the intricate mechanisms governing bone homeostasis and responses to pharmacological agents.

Rising role of 3D-printing in delivery of therapeutics for infectious disease

Modern drug delivery to tackle infectious disease has drawn close to personalizing medicine for specific patient populations. Challenges include antibiotic-resistant infections, healthcare associated infections, and customizing treatments for local patient populations. Recently, 3D-printing has become a facilitator for the development of personalized pharmaceutic drug delivery systems. With a variety of manufacturing techniques, 3D-printing offers advantages in drug delivery development for controlled, fine-tuned release and platforms for different routes of administration. This review summarizes 3D-printing techniques in pharmaceutics and drug delivery focusing on treating infectious diseases, and discusses the influence of 3D-printing design considerations on drug delivery platforms targeting these diseases. Additionally, applications of 3D-printing in infectious diseases are summarized, with the goal to provide insight into how future delivery innovations may benefit from 3D-printing to address the global challenges in infectious disease.

Programmed release of vascular endothelial growth factor and exosome from injectable chitosan nanofibrous microsphere-based PLGA-PEG-PLGA hydrogel for enhanced bone regeneration

The healing of large bone defects remains a significant challenge in clinical practice. Accelerating both angiogenesis and osteogenesis can promote effective bone healing. In the natural healing process, angiogenesis precedes osteogenesis, providing a blood supply that supports the subsequent progression of osteogenesis. Developing a biomimetic scaffold that mimics the in vivo environment and promotes the proper sequence of vascularization followed by ossification is crucial for successful bone regeneration. In this study, a novel injectable dual-drug programmed releasing chitosan nanofibrous microsphere-based poly(D, l-lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(D,l-lactide-co-glycolide) (PLGA-PEG-PLGA) hydrogel is fabricated by incorporating vascular endothelial growth factor (VEGF) and microspheres loaded with dental pulp stem cells-derived exosomes (DPSCs-Exo). Rapid release of VEGF promotes the swift initiation of angiogenesis, while DPSCs-Exo release ensures persistent osteogenesis. Our results demonstrate that chitosan microsphere-based PLGA-PEG-PLGA hydrogel significantly promotes angiogenesis in human umbilical vascular endothelial cells and enhances the osteogenic differentiation of pre-osteoblasts. Furthermore, in vivo transplantation of this injectable chitosan microsphere-based PLGA-PEG-PLGA hydrogel into calvarial bone defects markedly promotes bone formation. Overall, our study provides a promising approach for improving bone regeneration by temporally replicating the behavior of angiogenesis and osteogenesis.

Assessment of different manufacturing techniques for the production of bioartificial scaffolds as soft organ transplant substitutes

Introduction: The problem of organs' shortage for transplantation is widely known: different manufacturing techniques such as Solvent casting, Electrospinning and 3D Printing were considered to produce bioartificial scaffolds for tissue engineering purposes and possible transplantation substitutes. The advantages of manufacturing techniques' combination to develop hybrid scaffolds with increased performing properties was also evaluated. Methods: Scaffolds were produced using poly-L-lactide-co-caprolactone (PLA-PCL) copolymer and characterized for their morphological, biological, and mechanical features. Results: Hybrid scaffolds showed the best properties in terms of viability (>100%) and cell adhesion. Furthermore, their mechanical properties were found to be comparable with the reference values for soft tissues (range 1-10 MPa). Discussion: The created hybrid scaffolds pave the way for the future development of more complex systems capable of supporting, from a morphological, mechanical, and biological standpoint, the physiological needs of the tissues/organs to be transplanted.

Addressable microfluidics technology for non-sacrificial analysis of biomaterial implants in vivo

Tissue regeneration-promoting and drug-eluting biomaterials are commonly implanted into animals as a part of late-stage testing before committing to human trials required by the government. Because the trials are very expensive (e.g., they can cost over a billion U.S. dollars), it is critical for companies to have the best possible characterization of the materials' safety and efficacy before it goes into a human. However, the conventional approaches to biomaterial evaluation necessitate sacrificial analysis (i.e., euthanizing a different animal for measuring each time point and retrieving the implant for histological analysis), due to the inability to monitor how the host tissues respond to the presence of the material in situ. This is expensive, inaccurate, discontinuous, and unethical. In contrast, our manuscript presents a novel microfluidic platform potentially capable of performing non-disruptive fluid manipulations within the spatial constraints of an 8 mm diameter critical calvarial defect-a "gold standard" model for testing engineered bone tissue scaffolds in living animals. In particular, here, addressable microfluidic plumbing is specifically adapted for the in vivo implantation into a simulated rat's skull, and is integrated with a combinatorial multiplexer for a better scaling of many time points and/or biological signal measurements. The collected samples (modeled as food dyes for proof of concept) are then transported, stored, and analyzed ex vivo, which adds previously-unavailable ease and flexibility. Furthermore, care is taken to maintain a fluid equilibrium in the simulated animal's head during the sampling to avoid damage to the host and to the implant. Ultimately, future implantation protocols and technology improvements are envisioned toward the end of the manuscript. Although the bone tissue engineering application was chosen as a proof of concept, with further work, the technology is potentially versatile enough for other in vivo sampling applications. Hence, the successful outcomes of its advancement should benefit companies developing, testing, and producing vaccines and drugs by accelerating the translation of advanced cell culturing tech to the clinical market. Moreover, the nondestructive monitoring of the in vivo environment can lower animal experiment costs and provide data-gathering continuity superior to the conventional destructive analysis. Lastly, the reduction of sacrifices stemming from the use of this technology would make future animal experiments more ethical.

3D-Printed Polycaprolactone Mechanical Characterization and Suitability Assessment for Producing Wrist-Hand Orthoses

In this research, the mechanical properties of 3D-printed polycaprolactone (PCL), a biocompatible and biodegradable semi-crystalline polyester, available as feedstock for additive manufacturing technology based on the material extrusion process, were determined. The influence of the infill pattern (zig-zag vs. gyroid) and ultraviolet (UV-B) exposure over the specimens' mechanical performances were also investigated to gather relevant data on the process parameter settings for different applications. Specimens and samples of 3D-printed PCL were analyzed through tensile and flexural tests. The experimental data showed the good repeatability of the manufacturing process, as well as a mechanical behavior independent of the specimens' infill pattern at full density. No differences between the failure patterns of the tensile specimens were recorded. UV-B exposure proved to have a significant negative impact on the specimens' tensile strength. The 3D printing of PCL and PCL blends is reported mainly for use in scaffold manufacturing or drug delivery applications. As another novelty, the suitability of commercial PCL filaments for producing patient-customized wrist-hand orthoses was also assessed in this study. Semi-cylindrical PCL samples mimicking the forearm part of a wrist-hand orthosis with hexagonal open pockets were 3D-printed and mechanically tested. The results were discussed in comparison to samples with a similar design, made of polylactic acid. The experiments revealed the need to carefully calibrate the manufacturing parameters to generate defect-free, good quality prints. Once settings were established, promising results were obtained when producing orthoses in a ready-to-use form. On the other hand, the attempts to thermoform flat 3D-printed PCL orthoses proved unsuccessful.

Biomaterial-based 3D bioprinting strategy for orthopedic tissue engineering

The advent of three-dimensional (3D) bioprinting has enabled impressive progress in the development of 3D cellular constructs to mimic the structural and functional characteristics of natural tissues. Bioprinting has considerable translational potential in tissue engineering and regenerative medicine. This review highlights the rational design and biofabrication strategies of diverse 3D bioprinted tissue constructs for orthopedic tissue engineering applications. First, we elucidate the fundamentals of 3D bioprinting techniques and biomaterial inks and discuss the basic design principles of bioprinted tissue constructs. Next, we describe the rationale and key considerations in 3D bioprinting of tissues in many different aspects. Thereafter, we outline the recent advances in 3D bioprinting technology for orthopedic tissue engineering applications, along with detailed strategies of the engineering methods and materials used, and discuss the possibilities and limitations of different 3D bioprinted tissue products. Finally, we summarize the current challenges and future directions of 3D bioprinting technology in orthopedic tissue engineering and regenerative medicine. This review not only delineates the representative 3D bioprinting strategies and their tissue engineering applications, but also provides new insights for the clinical translation of 3D bioprinted tissues to aid in prompting the future development of orthopedic implants. STATEMENT OF SIGNIFICANCE: 3D bioprinting has driven major innovations in the field of tissue engineering and regenerative medicine; aiming to develop a functional viable tissue construct that provides an alternative regenerative therapy for musculoskeletal tissue regeneration. 3D bioprinting-based biofabrication strategies could open new clinical possibilities for creating equivalent tissue substitutes with the ability to customize them to meet patient demands. In this review, we summarize the significance and recent advances in 3D bioprinting technology and advanced bioinks. We highlight the rationale for biofabrication strategies using 3D bioprinting for orthopedic tissue engineering applications. Furthermore, we offer ample perspective and new insights into the current challenges and future direction of orthopedic bioprinting translation research.

Emerging 3D bioprinting applications in plastic surgery

Plastic surgery is a discipline that uses surgical methods or tissue transplantation to repair, reconstruct and beautify the defects and deformities of human tissues and organs. Three-dimensional (3D) bioprinting has gained widespread attention because it enables fine customization of the implants in the patient's surgical area preoperatively while avoiding some of the adverse reactions and complications of traditional surgical approaches. In this paper, we review the recent research advances in the application of 3D bioprinting in plastic surgery. We first introduce the printing process and basic principles of 3D bioprinting technology, revealing the advantages and disadvantages of different bioprinting technologies. Then, we describe the currently available bioprinting materials, and dissect the rationale for special dynamic 3D bioprinting (4D bioprinting) that is achieved by varying the combination strategy of bioprinting materials. Later, we focus on the viable clinical applications and effects of 3D bioprinting in plastic surgery. Finally, we summarize and discuss the challenges and prospects for the application of 3D bioprinting in plastic surgery. We believe that this review can contribute to further development of 3D bioprinting in plastic surgery and provide lessons for related research.

Fabrication of Interleukin-4 Encapsulated Bioactive Microdroplets for Regulating Inflammation and Promoting Osteogenesis

Background

Despite the inherent regenerative ability of bone, large bone defect regeneration remains a major clinical challenge for orthopedic surgery. Therapeutic strategies medicated by M2 phenotypic macrophages or M2 macrophage inducer have been widely used to promote tissue remodeling. In this study, ultrasound-responsive bioactive microdroplets (MDs) encapsulated with bioactive molecule interleukin-4 (IL4, hereafter designated MDs-IL4) were fabricated to regulate macrophage polarization and potentiate the osteogenic differentiation of human mesenchymal stem cells (hBMSCs).

Materials and Methods

The MTT assay, live and dead staining, and phalloidin/DAPI dual staining were used to evaluate biocompatibility in vitro. H&E staining was used to evaluate biocompatibility in vivo. Inflammatory macrophages were further induced via lipopolysaccharide (LPS) stimulation to mimic the pro-inflammatory condition. The immunoregulatory role of the MDs-IL4 was tested via macrophage phenotypic marker gene expression, pro-inflammatory cytokine level, cell morphological analysis, and immunofluorescence staining, etc. The immune-osteogenic response of hBMSCs via macrophages and hBMSCs interactions was further investigated in vitro.

Results

The bioactive MDs-IL4 scaffold showed good cytocompatibility in RAW 264.7 macrophages and hBMSCs. The results confirmed that the bioactive MDs-IL4 scaffold could reduce inflammatory phenotypic macrophages, as evidenced by changing in morphological features, reduction in pro-inflammatory marker gene expression, increase of M2 phenotypic marker genes, and inhibition of pro-inflammatory cytokine secretion. Additionally, our results indicate that the bioactive MDs-IL4 could significantly enhance the osteogenic differentiation of hBMSCs via its potential immunomodulatory properties.

Conclusion

Our results demonstrate that the bioactive MDs-IL4 scaffold could be used as novel carrier system for other pro-osteogenic molecules, thus having potential applications in bone tissue regeneration.

Functionalized multidimensional biomaterials for bone microenvironment engineering applications: Focus on osteoimmunomodulation

As bone biology develops, it is gradually recognized that bone regeneration is a pathophysiological process that requires the simultaneous participation of multiple systems. With the introduction of osteoimmunology, the interplay between the immune system and the musculoskeletal diseases has been the conceptual framework for a thorough understanding of both systems and the advancement of osteoimmunomodulaty biomaterials. Various therapeutic strategies which include intervention of the surface characteristics or the local delivery systems with the incorporation of bioactive molecules have been applied to create an ideal bone microenvironment for bone tissue regeneration. Our review systematically summarized the current research that is being undertaken in the field of osteoimmunomodulaty bone biomaterials on a case-by-case basis, aiming to inspire more extensive research and promote clinical conversion.

Anatomically and Biomechanically Relevant Monolithic Total Disc Replacement Made of 3D-Printed Thermoplastic Polyurethane

Various implant treatments, including total disc replacements, have been tried to treat lumbar intervertebral disc (IVD) degeneration, which is claimed to be the main contributor of lower back pain. The treatments, however, come with peripheral issues. This study proposes a novel approach that complies with the anatomical features of IVD, the so-called monolithic total disc replacement (MTDR). As the name suggests, the MTDR is a one-part device that consists of lattice and rigid structures to mimic the nucleus pulposus and annulus fibrosus, respectively. The MTDR can be made of two types of thermoplastic polyurethane (TPU 87A and TPU 95A) and fabricated using a 3D printing approach: fused filament fabrication. The MTDR design involves two configurations—the full lattice (FLC) and anatomy-based (ABC) configurations. The MTDR is evaluated in terms of its physical, mechanical, and cytotoxicity properties. The physical characterization includes the geometrical evaluations, wettability measurements, degradability tests, and swelling tests. The mechanical characterization comprises compressive tests of the materials, an analytical approach using the Voigt model of composite, and a finite element analysis. The cytotoxicity assays include the direct assay using hemocytometry and the indirect assay using a tetrazolium-based colorimetric (MTS) assay. The geometrical evaluation shows that the fabrication results are tolerable, and the two materials have good wettability and low degradation rates. The mechanical characterization shows that the ABC-MTDR has more similar mechanical properties to an IVD than the FLC-MTDR. The cytotoxicity assays prove that the materials are non-cytotoxic, allowing cells to grow on the surfaces of the materials.

The Effect of PCL Addition on 3D-Printable PLA/HA Composite Filaments for the Treatment of Bone Defects

The still-growing field of additive manufacturing (AM), which includes 3D printing, has enabled manufacturing of patient-specific medical devices with high geometrical accuracy in a relatively quick manner. However, the development of materials with specific properties is still ongoing, including those for enhanced bone-repair applications. Such applications seek materials with tailored mechanical properties close to bone tissue and, importantly, that can serve as temporary supports, allowing for new bone ingrowth while the material is resorbed. Thus, controlling the resorption rate of materials for bone applications can support bone healing by balancing new tissue formation and implant resorption. In this regard, this work aimed to study the combination of polylactic acid (PLA), polycaprolactone (PCL) and hydroxyapatite (HA) to develop customized biocompatible and bioresorbable polymer-based composite filaments, through extrusion, for fused filament fabrication (FFF) printing. PLA and PCL were used as supporting polymer matrices while HA was added to enhance the biological activity. The materials were characterized in terms of mechanical properties, thermal stability, chemical composition and morphology. An accelerated degradation study was executed to investigate the impact of degradation on the above-mentioned properties. The results showed that the materials' chemical compositions were not affected by the extrusion nor the printing process. All materials exhibited higher mechanical properties than human trabecular bone, even after degradation with a mass loss of around 30% for the polymer blends and 60% for the composites. It was also apparent that the mineral accelerated the polymer degradation significantly, which can be advantageous for a faster healing time, where support is required only for a shorter time period.

Polylactide Perspectives in Biomedicine: From Novel Synthesis to the Application Performance

The incessant developments in the pharmaceutical and biomedical fields, particularly, customised solutions for specific diseases with targeted therapeutic treatments, require the design of multicomponent materials with multifunctional capabilities. Biodegradable polymers offer a variety of tailored physicochemical properties minimising health adverse side effects at a low price and weight, which are ideal to design matrices for hybrid materials. PLAs emerge as an ideal candidate to develop novel materials as are endowed withcombined ambivalent performance parameters. The state-of-the-art of use of PLA-based materials aimed at pharmaceutical and biomedical applications is reviewed, with an emphasis on the correlation between the synthesis and the processing conditions that define the nanostructure generated, with the final performance studies typically conducted with either therapeutic agents by in vitro and/or in vivo experiments or biomedical devices.

Optimizing Design Parameters of PLA 3D-Printed Scaffolds for Bone Defect Repair

Current materials used to fill bone defects (ceramics, cement) either lack strength or do not induce bone repair. The use of biodegradable polymers such as PLA may promote patient healing by stimulating the production of new bone in parallel with a controlled degradation of the scaffold. This project aims to determine the design parameters maximising scaffold mechanical performance in such materials. Starting from a base cylindrical model of 10 mm height and of outer and inner diameters of 10 and 4 mm, respectively, 27 scaffolds were designed. Three design parameters were investigated: pore distribution (crosswise, lengthwise, and eccentric), pore shape (triangular, circular, and square), and pore size (surface area of 0.25 mm2, 0.5625 mm2, and 1 mm2). Using the finite element approach, a compressive displacement (0.05 mm/s up to 15% strain) was simulated on the models and the resulting scaffold stiffnesses (N/mm2) were compared. The models presenting good mechanical behaviors were further printed along two orientations: 0° (cylinder sitting on its base) and 90° (cylinder laying on its side). A total of n = 5 specimens were printed with PLA for each of the retained models and experimentally tested using a mechanical testing machine with the same compression parameters. Rigidity and yield strength were evaluated from the experimental curves. Both numerically and experimentally, the highest rigidity was found in the model with circular pore shape, crosswise pore distribution, small pore size (surface area of 0.25 mm2), and a 90° printing orientation. Its average rigidity reached 961 ± 32 MPa from the mechanical testing and 797 MPa from the simulation, with a yield strength of 42 ± 1.5 MPa. The same model with a printing orientation of 0° resulted in an average rigidity of 515 ± 7 MPa with a yield strength of 32 ± 1.6 MPa. Printing orientation and pore size were found to be the most influential design parameters on rigidity. The developed design methodology should accelerate the identification of effective scaffolds for future in vitro and in vivo studies.

Modified Histopathological Protocol for Poly-ɛ-Caprolactone Scaffolds Preserving Their Trabecular, Honeycomb-like Structure

Poly-ɛ-caprolactone (PCL) is now widely studied in relation to the engineering of bone, cartilage, tendons, and other tissues. Standard histological protocols can destroy the carefully created trabecular and honeycomb-like architecture of PCL scaffolds, and could lead to scaffold fibers swelling, resulting in the displacement or compression of tissues inside the scaffold. The aim of this study was to modify a standard histopathological protocol for PCL scaffold preparation and evaluate it on porous cylindrical PCL scaffolds in a rat model. In 16 inbred Wag rats, 2 PCL scaffolds were implanted subcutaneously to both inguinal areas. Two months after implantation, harvested scaffolds were first subjected to μCT imaging, and then to histopathological analysis with standard (left inguinal area) and modified histopathological protocols (right inguinal area). To standardize the results, soft tissue percentages (STPs) were calculated on scaffold cross-sections obtained from both histopathological protocols and compared with corresponding µCT cross-sections. The modified protocol enabled the assessment of almost 10× more soft tissues on the scaffold cross-section than the standard procedure. Moreover, STP was only 1.5% lower than in the corresponding µCT cross-sections assessed before the histopathological procedure. The presented modification of the histopathological protocol is cheap, reproducible, and allows for a comprehensive evaluation of PCL scaffolds while maintaining their trabecular, honeycomb-like structure on cross-sections.