Evaluation of 3D-Printed Polycaprolactone Scaffolds Coated with Freeze-Dried Platelet-Rich Plasma for Bone Regeneration

Synthesis and Mass Spectrometry Structural Assessment of Polyesteramides Based on ε-Caprolactone and L-Phenylalanine

L-Phenylalanine-ε-caprolactone-based polyesteramides (PCPs) were synthesized via melt polycondensation across a diverse range of molar compositions. The copolymer structure was extensively characterized using nuclear magnetic resonance (NMR) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). NMR analysis confirmed the intercalation of the L-Phenylalanine comonomer units within the polyester backbone. MALDI MS characterization further demonstrated the formation of linear PCP chains with carboxyl end groups. A detailed structural analysis through MALDI MS/MS fragmentation indicated that ester bond scission was the predominant fragmentation mechanism, depicting the polyesteramide sequence in the copolymers. The resulting copolymers were primarily amorphous, except for those with molar compositions of 90/10 and 80/20, which exhibited semi-crystalline structures. Additionally, these PCPs showed an increase in glass transition temperatures with higher amino acid contents and demonstrated good thermal stabilities, as evidenced by a 10% mass loss at elevated temperatures.

Biofabrication Strategies for Oral Soft Tissue Regeneration

Gingival recession, a prevalent condition affecting the gum tissues, is characterized by the exposure of tooth root surfaces due to the displacement of the gingival margin. This review explores conventional treatments, highlighting their limitations and the quest for innovative alternatives. Importantly, it emphasizes the critical considerations in gingival tissue engineering leveraging on cells, biomaterials, and signaling factors. Successful tissue-engineered gingival constructs hinge on strategic choices such as cell sources, scaffold design, mechanical properties, and growth factor delivery. Unveiling advancements in recent biofabrication technologies like 3D bioprinting, electrospinning, and microfluidic organ-on-chip systems, this review elucidates their precise control over cell arrangement, biomaterials, and signaling cues. These technologies empower the recapitulation of microphysiological features, enabling the development of gingival constructs that closely emulate the anatomical, physiological, and functional characteristics of native gingival tissues. The review explores diverse engineering strategies aiming at the biofabrication of realistic tissue-engineered gingival grafts. Further, the parallels between the skin and gingival tissues are highlighted, exploring the potential transfer of biofabrication approaches from skin tissue regeneration to gingival tissue engineering. To conclude, the exploration of innovative biofabrication technologies for gingival tissues and inspiration drawn from skin tissue engineering look forward to a transformative era in regenerative dentistry with improved clinical outcomes.

Use of 3D-Printed Implants in Complex Foot and Ankle Reconstruction

SUMMARY

Treatment of traumatic critical-sized bone defects remains a challenge for orthopaedic surgeons. Autograft remains the gold standard to address bone loss, but for larger defects, different strategies must be used. The use of 3D-printed implants to address lower extremity trauma and bone loss is discussed with current techniques including bone transport, Masquelet, osteomyocutaneous flaps, and massive allografts. Considerations and future directions of implant design, augmentation, and optimization of the peri-implant environment to maximize patient outcome are reviewed.

In Vitro and In Vivo Evaluation of 3D Printed Poly(Ethylene Glycol) Dimethacrylate-Based Photocurable Hydrogel Platform for Bone Tissue Engineering

This study focuses to develop a unique hybrid hydrogel bioink formulation that incorporates poly(ethylene glycol) dimethacrylate (PEGDMA), gelatin (Gel), and methylcellulose (MC). This formulation achieves the necessary viscosity for extrusion-based three-dimensional (3D) printing of scaffolds intended for bone regeneration. After thorough optimization of the hybrid bioink system with Gel, three distinct scaffold groups are investigated in vitro: 0%, 3%, and 6% (w/v) Gel. These scaffold groups are examined for their morphology, mechanical strength, biodegradation, in vitro cell proliferation and differentiation, and in vivo bone formation using a rat cranial defect model. Among these scaffold compositions, the 3% Gel scaffold exhibits the most favorable characteristics, prompting further evaluation as a rat mesenchymal stem cell (rMSC) carrier in a critical-size cranial defect within a Lewis rat model. The compressive strength of all three scaffold groups range between 1 and 2 MPa. Notably, the inclusion of Gel in the scaffolds leads to enhanced bioactivity and cell adhesion. The Gel-containing scaffolds notably amplify osteogenic differentiation, as evidenced by alkaline phosphatase (ALP) and Western blot analyses. The in vivo results, as depicted by microcomputed tomography, showcase augmented osteogenesis within cell-seeded scaffolds, thus validating this innovative PEGDMA-based scaffold system as a promising candidate for cranial bone defect healing.

BMP-2-immobilized PCL 3D printing scaffold with a leaf-stacked structure as a physically and biologically activated bone graft

Although three-dimensional (3D) printing techniques are used to mimic macro- and micro-structures as well as multi-structural human tissues in tissue engineering, efficient target tissue regeneration requires bioactive 3D printing scaffolds. In this study, we developed a bone morphogenetic protein-2 (BMP-2)-immobilized polycaprolactone (PCL) 3D printing scaffold with leaf-stacked structure (LSS) (3D-PLSS-BMP) as a bioactive patient-tailored bone graft. The unique LSS was introduced on the strand surface of the scaffold via heating/cooling in tetraglycol without significant deterioration in physical properties. The BMP-2 adsorbed on3D-PLSS-BMPwas continuously released from LSS over a period of 32 d. The LSS can be a microtopographical cue for improved focal cell adhesion, proliferation, and osteogenic differentiation.In vitrocell culture andin vivoanimal studies demonstrated the biological (bioactive BMP-2) and physical (microrough structure) mechanisms of3D-PLSS-BMPfor accelerated bone regeneration. Thus, bioactive molecule-immobilized 3D printing scaffold with LSS represents a promising physically and biologically activated bone graft as well as an advanced tool for widespread application in clinical and research fields.

Biopolymers and Their Application in Bioprinting Processes for Dental Tissue Engineering

Dental tissues are composed of multiple tissues with complex organization, such as dentin, gingiva, periodontal ligament, and alveolar bone. These tissues have different mechanical and biological properties that are essential for their functions. Therefore, dental diseases and injuries pose significant challenges for restorative dentistry, as they require innovative strategies to regenerate damaged or missing dental tissues. Biomimetic bioconstructs that can effectively integrate with native tissues and restore their functionalities are desirable for dental tissue regeneration. However, fabricating such bioconstructs is challenging due to the diversity and complexity of dental tissues. This review provides a comprehensive overview of the recent developments in polymer-based tissue engineering and three-dimensional (3D) printing technologies for dental tissue regeneration. It also discusses the current state-of-the-art, focusing on key techniques, such as polymeric biomaterials and 3D printing with or without cells, used in tissue engineering for dental tissues. Moreover, the final section of this paper identifies the challenges and future directions of this promising research field.

Advances in additive manufacturing of polycaprolactone based scaffolds for bone regeneration

Critical sized bone defects are difficult to manage and currently available clinical/surgical strategies for treatment are not completely successful. Polycaprolactone (PCL) which is a biodegradable and biocompatible thermoplastic can be 3D printed using medical images into patient specific bone implants. The excellent mechanical properties and low immunogenicity of PCL makes it an ideal biomaterial candidate for 3D printing of bone implants. Though PCL suffers from the limitation of being bio-inert. Here we describe the use of PCL as a biomaterial for 3D printing for bone regeneration, and advances made in the field. The specific focus is on the different 3D printing techniques used for this purpose and various modification that can enhance bone regeneration following the development pathways. We further describe the effect of various scaffold characteristics on bone regeneration both in vitro and the translational assessment of these 3D printed PCL scaffolds in animal studies. The generated knowledge will help understand cell-material interactions of 3D printed PCL scaffolds, to further improve scaffold chemistry and design that can replicate bone developmental processes and can be translated clinically.

Nanosilicate-functionalized nanofibrous membrane facilitated periodontal regeneration potential by harnessing periodontal ligament cell-mediated osteogenesis and immunomodulation

Although various new biomaterials have enriched the methods for periodontal regeneration, their efficacy is still controversial, and the regeneration of damaged support tissue in the periodontium remains challenging. Laponite (LAP) nanosilicate is a layered two-dimensional nanoscale, ultrathin nanomaterial with a unique structure and brilliant biocompatibility and bioactivity. This study aimed to investigate the effects of nanosilicate-incorporated PCL (PCL/LAP) nanofibrous membranes on periodontal ligament cells (PDLCs) in vitro and periodontal regeneration in vivo. A PCL/LAP nanofibrous membrane was fabricated by an electrospinning method. The characterization of PCL/LAP nanofibrous membrane were determined by scanning electron microscopy (SEM), energy dispersive spectrum of X-ray (EDS), inductively coupled plasma mass spectrometry (ICP-MS) and tensile test. The proliferation and osteogenic differentiation of PDLCs on the PCL/LAP nanofibrous membrane were evaluated. A PDLCs and macrophage coculture system was used to explore the immunomodulatory effects of the PCL/LAP nanofibrous membrane. PCL/LAP nanofibrous membrane was implanted into rat calvarial and periodontal defects, and the regenerative potential was evaluated by microcomputed topography (micro-CT) and histological analysis. The PCL/LAP nanofibrous membrane showed good biocompatibility and bioactivity. It enhanced the proliferation and osteogenic differentiation of PDLCs. The PCL/LAP nanofibrous membrane also stimulated anti-inflammatory and pro-remodeling N2 neutrophil formation, regulated inflammatory responses and induced M2 macrophage polarization by orchestrating the immunomodulatory effects of PDLCs. The PCL/LAP nanofibrous membrane promoted rat calvarial defect repair and periodontal regeneration in vivo. LAP nanosilicate-incorporated PCL membrane is capable of mediating osteogenesis and immunomodulation of PDLCs in vitro and accelerating periodontal regeneration in vivo. It could be a promising biomaterial for periodontal regeneration therapy.

Recent advances on 3D-printed PCL-based composite scaffolds for bone tissue engineering

Population ageing and various diseases have increased the demand for bone grafts in recent decades. Bone tissue engineering (BTE) using a three-dimensional (3D) scaffold helps to create a suitable microenvironment for cell proliferation and regeneration of damaged tissues or organs. The 3D printing technique is a beneficial tool in BTE scaffold fabrication with appropriate features such as spatial control of microarchitecture and scaffold composition, high efficiency, and high precision. Various biomaterials could be used in BTE applications. PCL, as a thermoplastic and linear aliphatic polyester, is one of the most widely used polymers in bone scaffold fabrication. High biocompatibility, low cost, easy processing, non-carcinogenicity, low immunogenicity, and a slow degradation rate make this semi-crystalline polymer suitable for use in load-bearing bones. Combining PCL with other biomaterials, drugs, growth factors, and cells has improved its properties and helped heal bone lesions. The integration of PCL composites with the new 3D printing method has made it a promising approach for the effective treatment of bone injuries. The purpose of this review is give a comprehensive overview of the role of printed PCL composite scaffolds in bone repair and the path ahead to enter the clinic. This study will investigate the types of 3D printing methods for making PCL composites and the optimal compounds for making PCL composites to accelerate bone healing.

The Osteogenic Role of Biomaterials Combined with Human-Derived Dental Stem Cells in Bone Tissue Regeneration

The use of stem cells in regenerative medicine had great potential for clinical applications. However, cell delivery strategies have critical importance in stimulating the differentiation of stem cells and enhancing their potential to regenerate damaged tissues. Different strategies have been used to investigate the osteogenic potential of dental stem cells in conjunction with biomaterials through in vitro and in vivo studies. Osteogenesis has a broad implication in regenerative medicine, particularly for maxillofacial defects. This review summarizes some of the most recent developments in the field of tissue engineering using dental stem cells.

Immobilization and Release of Platelet-Rich Plasma from Modified Nanofibers Studied by Advanced X-ray Photoelectron Spectroscopy Analyses

Platelet-rich Plasma (PRP) is an ensemble of growth factors, extracellular matrix components, and proteoglycans that are naturally balanced in the human body. In this study, the immobilization and release of PRP component nanofiber surfaces modified by plasma treatment in a gas discharge have been investigated for the first time. The plasma-treated polycaprolactone (PCL) nanofibers were utilized as substrates for the immobilization of PRP, and the amount of PRP immobilized was assessed by fitting a specific X-ray Photoelectron Spectroscopy (XPS) curve to the elemental composition changes. The release of PRP was then revealed by measuring the XPS after soaking nanofibers containing immobilized PRP in buffers of varying pHs (4.8; 7.4; 8.1). Our investigations have proven that the immobilized PRP would continue to cover approximately fifty percent of the surface after eight days.

Strategies To Modify the Surface and Bulk Properties of 3D-Printed Solid Scaffolds for Tissue Engineering Applications

3D printing is one of the effective scaffold fabrication techniques that emerged in the 21st century that has the potential to revolutionize the field of tissue engineering. The solid scaffolds developed by 3D printing are still one of the most sought-after approaches for developing hard-tissue regeneration and repair. However, applications of these solid scaffolds get limited due to their poor surface and bulk properties, which play a significant role in tissue integration, loadbearing, antimicrobial/antifouling properties, and others. As a result, several efforts have been directed to modify the surface and bulk of these solid scaffolds. These modifications have significantly improved the adoption of 3D-printed solid scaffolds and devices in the healthcare industry. Nevertheless, the in vivo implant applications of these 3D-printed solid scaffolds/devices are still under development. They require attention in terms of their surface/bulk properties, which dictate their functionality. Therefore, in the current review, we have discussed different 3D-printing parameters that facilitate the fabrication of solid scaffolds/devices with different properties. Further, changes in the bulk properties through material and microstructure modification are also being discussed. After that, we deliberated on the techniques that modify the surfaces through chemical and material modifications. The computational approaches for the bulk modification of these 3D-printed materials are also mentioned, focusing on tissue engineering. We have also briefly discussed the application of these solid scaffolds/devices in tissue engineering. Eventually, the review is concluded with an analysis of the choice of surface/bulk modification based on the intended application in tissue engineering.

Three-Dimensional Impression of Biomaterials for Alveolar Graft: Scoping Review

Craniofacial bone defects are one of the biggest clinical challenges in regenerative medicine, with secondary autologous bone grafting being the gold-standard technique. The development of new three-dimensional matrices intends to overcome the disadvantages of the gold-standard method. The aim of this paper is to put forth an in-depth review regarding the clinical efficiency of available 3D printed biomaterials for the correction of alveolar bone defects. A survey was carried out using the following databases: PubMed via Medline, Cochrane Library, Scopus, Web of Science, EMBASE, and gray literature. The inclusion criteria applied were the following: in vitro, in vivo, ex vivo, and clinical studies; and studies that assessed bone regeneration resorting to 3D printed biomaterials. The risk of bias of the in vitro and in vivo studies was performed using the guidelines for the reporting of pre-clinical studies on dental materials by Faggion Jr and the SYRCLE risk of bias tool, respectively. In total, 92 publications were included in the final sample. The most reported three-dimensional biomaterials were the PCL matrix, β-TCP matrix, and hydroxyapatite matrix. These biomaterials can be combined with different polymers and bioactive molecules such as rBMP-2. Most of the included studies had a high risk of bias. Despite the advances in the research on new three-dimensionally printed biomaterials in bone regeneration, the existing results are not sufficient to justify the application of these biomaterials in routine clinical practice.

Fabrication of Mechanically Enhanced, Suturable, Fibrous Hydrogel Membranes

Poly(vinyl-alcohol) hydrogels have already been successfully utilised as drug carrier systems and tissue engineering scaffolds. However, lacking mechanical strength and suturability hinders any prospects for clinical and surgical applications. The objective of this work was to fabricate mechanically robust PVA membranes, which could also withstand surgical manipulation and suturing. Electrospun membranes and control hydrogels were produced with 61 kDa PVA. Using a high-speed rotating cylindrical collector, we achieved fibre alignment (fibre diameter: 300 ± 50 nm). Subsequently, we created multilayered samples with different orientations to achieve multidirectional reinforcement. Finally, utilising glutaraldehyde as a cross-linker, we created insoluble fibrous-hydrogel membranes. Mechanical studies were performed, confirming a fourfold increase in the specific loading capacities (from 0.21 to 0.84 Nm²/g) in the case of the monolayer samples. The multilayered membranes exhibited increased resistance from both horizontal and vertical directions, which varies according to the specific arrangement. Finally, the cross-linked fibrous hydrogel samples not only exhibited specific loading capacities significantly higher than their counterpart bulk hydrogels but successfully withstood suturing. Although cross-linking optimisation and animal experiments are required, these membranes have great prospects as alternatives to current surgical meshes, while the methodology could also be applied in other systems as well.

Key aspects for conception and construction of co-culture models of tumor-stroma interactions

The tumor microenvironment is crucial in the initiation and progression of cancers. The interplay between cancer cells and the surrounding stroma shapes the tumor biology and dictates the response to cancer therapies. Consequently, a better understanding of the interactions between cancer cells and different components of the tumor microenvironment will drive progress in developing novel, effective, treatment strategies. Co-cultures can be used to study various aspects of these interactions in detail. This includes studies of paracrine relationships between cancer cells and stromal cells such as fibroblasts, endothelial cells, and immune cells, as well as the influence of physical and mechanical interactions with the extracellular matrix of the tumor microenvironment. The development of novel co-culture models to study the tumor microenvironment has progressed rapidly over recent years. Many of these models have already been shown to be powerful tools for further understanding of the pathophysiological role of the stroma and provide mechanistic insights into tumor-stromal interactions. Here we give a structured overview of different co-culture models that have been established to study tumor-stromal interactions and what we have learnt from these models. We also introduce a set of guidelines for generating and reporting co-culture experiments to facilitate experimental robustness and reproducibility.

3D printed polylactic acid/gelatin-nano-hydroxyapatite/platelet-rich plasma scaffold for critical-sized skull defect regeneration

BACKGROUND

Three-dimensional (3D) printing is a capable approach for the fabrication of bone tissue scaffolds. Nevertheless, a purely made scaffold such as polylactic acid (PLA) may suffer from shortcomings and be restricted due to its biological behavior. Gelatin, hydroxyapatite and platelet-rich plasma (PRP) have been revealed to be of potential to enhance the osteogenic effect. In this study, it was tried to improve the properties of 3D-printed PLA scaffolds by infilling them with gelatin-nano-hydroxyapatite (PLA/G-nHA) and subsequent coating with PRP. For comparison, bare PLA and PLA/G-nHA scaffolds were also fabricated. The printing accuracy, the scaffold structural characterizations, mechanical properties, degradability behavior, cell adhesion, mineralization, systemic effect of the scaffolds on the liver enzymes, osteocalcin level in blood serum and in vivo bone regeneration capability in rat critical-sized calvaria defect were evaluated.

RESULTS

High printing accuracy (printing error of < 11%) was obtained for all measured parameters including strut thickness, pore width, scaffold density and porosity%. The highest mean ultimate compression strength (UCS) was associated with PLA/G-nHA/PRP scaffolds, which was 10.95 MPa. A slow degradation rate was observed for all scaffolds. The PLA/G-nHA/PRP had slightly higher degradation rate, possibly due to PRP release, with burst release occurred at week 4. The MTT results showed that PLA/G-nHA/PRP provided the highest cell proliferation at all time points, and the serum biochemistry (ALT and AST level) results indicated no abnormal/toxic influence caused by scaffold biomaterials. Superior cell adhesion and mineralization were obtained for PLA/G-nHA/PRP. Furthermore, all the developed scaffolds showed bone repair capability. The PLA/G-nHA/PRP scaffolds could better support bone regeneration than bare PLA and PLA/G-nHA scaffolds.

CONCLUSION

The PLA/G-nHA/PRP scaffolds can be considered as potential for hard tissue repair.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

Platelet-rich plasma: a comparative and economical therapy for wound healing and tissue regeneration

Rise in the incidences of chronic degenerative diseases with aging makes wound care a socio-economic burden and unceasingly necessitates a novel, economical, and efficient wound healing treatment. Platelets have a crucial role in hemostasis and thrombosis by modulating distinct mechanistic phases of wound healing, such as promoting and stabilizing the clot. Platelet-rich plasma (PRP) contains a high concentration of platelets than naïve plasma and has an autologous origin with no immunogenic adverse reactions. As a consequence, PRP has gained significant attention as a therapeutic to augment the healing process. Since the past few decades, a robust volume of research and clinical trials have been performed to exploit extensive role of PRP in wound healing/tissue regeneration. Despite these rigorous studies and their application in diversified medical fields, efficacy of PRP-based therapies is continuously questioned owing to the paucity of large samplesizes, controlled clinical trials, and standard protocols. This review systematically delineates the process of wound healing and involvement of platelets in tissue repair mechanisms. Additionally, emphasis is laid on PRP, its preparation methods, handling, classification,application in wound healing, and PRP as regenerative therapeutics combined with biomaterials and mesenchymal stem cells (MSCs).

3D Printed and Bioprinted Membranes and Scaffolds for the Periodontal Tissue Regeneration: A Narrative Review

Numerous technologies and materials were developed with the aim of repairing and reconstructing the tissue loss in patients with periodontitis. Periodontal guided bone regeneration (GBR) and guided tissue regeneration (GTR) involves the use of a membrane which prevents epithelial cell migration, and helps to maintain the space, creating a protected area in which tissue regeneration is favored. Over the time, manufacturing procedures of such barrier membranes followed important improvements. Three-dimensional (3D) printing technology has led to major innovations in periodontal regeneration methods, using technologies such as inkjet printing, light-assisted 3D printing or micro-extrusion. Besides the 3D printing of monophasic and multi-phasic scaffolds, bioprinting and tissue engineering have emerged as innovative technologies which can change the way we see GTR and GBR.

In vitro and in vivo biocompatibility of decellularized cellulose scaffolds functionalized with chitosan and platelet rich plasma for tissue engineering applications

This study describes the fabrication of cellulose scaffold (CS) and cellulose-chitosan (CS/CHI) scaffolds from the immature endosperm of Borassus flabellifer (Linn.) (BF) loaded with platelet rich plasma (PRP). Thus, developed scaffolds were evaluated for their physicochemical and mechanical behavior, growth factor release and biological performance. Additionally, in vivo response was assessed in a sub cutaneous rat model to study vascularization, host inflammatory response and macrophage polarization. The results of this study demonstrated that CS and CS/CHI scaffolds with PRP demonstrated favorable physiochemical and morphogical properties. The scaffold groups CS-PRP and CS/CHI-PRP were able to release growth factors in a well sustained manner under physiological conditions. The presence of PRP in cellulosic scaffolds did show significant differences in their behavior when investigated under in vitro studies, where the release of diverse cytokines improved the cellular proliferation and differentiation of osteoblasts. Finally, the PRP enriched scaffolds when studied under in vivo conditions showed increased angiogenesis and re-epithelialization with adequate collagen deposition and tissue remodeling. Our results suggest that besides the conventional carrier systems, this new-generation of plant-based cellulosic scaffolds with/without any modification can serve as a suitable carrier for PRP encapsulation and release, which can be used in numerous tissue regenerative therapies.

Use of Polyesters in Fused Deposition Modeling for Biomedical Applications

In recent years, 3D printing techniques experienced a growing interest in several sectors, including the biomedical one. Their main advantage resides in the possibility to obtain complex and personalized structures in a cost-effective way impossible to achieve with traditional production methods. This is especially true for Fused Deposition Modeling (FDM), one of the most diffused 3D printing methods. The easy customization of the final products' geometry, composition and physico-chemical properties is particularly interesting for the increasingly personalized approach adopted in modern medicine. Thermoplastic polymers are the preferred choice for FDM applications, and a wide selection of biocompatible and biodegradable materials is available to this aim. Moreover, these polymers can also be easily modified before and after printing to better suit the body environment and the mechanical properties of biological tissues. This review focuses on the use of thermoplastic aliphatic polyesters for FDM applications in the biomedical field. In detail, the use of poly(ε-caprolactone), poly(lactic acid), poly(lactic-co-glycolic acid), poly(hydroxyalkanoate)s, thermo-plastic poly(ester urethane)s and their blends has been thoroughly surveyed, with particular attention to their main features, applicability and workability. The state-of-the-art is presented and current challenges in integrating the additive manufacturing technology in the medical practice are discussed. This article is protected by copyright. All rights reserved.

Influence of 3D Printing Parameters on the Mechanical Stability of PCL Scaffolds and the Proliferation Behavior of Bone Cells

Introduction The use of scaffolds in tissue engineering is becoming increasingly important as solutions need to be found for the problem of preserving human tissue, such as bone or cartilage. In this work, scaffolds were printed from the biomaterial known as polycaprolactone (PCL) on a 3D Bioplotter. Both the external and internal geometry were varied to investigate their influence on mechanical stability and biocompatibility. Materials and Methods: An Envisiontec 3D Bioplotter was used to fabricate the scaffolds. First, square scaffolds were printed with variations in the strand width and strand spacing. Then, the filling structure was varied: either lines, waves, and honeycombs were used. This was followed by variation in the outer shape, produced as either a square, hexagon, octagon, or circle. Finally, the internal and external geometry was varied. To improve interaction with the cells, the printed PCL scaffolds were coated with type-I collagen. MG-63 cells were then cultured on the scaffolds and various tests were performed to investigate the biocompatibility of the scaffolds. Results: With increasing strand thickness and strand spacing, the compressive strengths decreased from 86.18 + 2.34 MPa (200 µm) to 46.38 + 0.52 MPa (600 µm). The circle was the outer shape with the highest compressive strength of 76.07 + 1.49 MPa, compared to the octagon, which had the lowest value of 52.96 ± 0.98 MPa. Varying the external shape (toward roundness) geometry, as well as the filling configuration, resulted in the highest values of compressive strength for the round specimens with honeycomb filling, which had a value of 91.4 + 1.4 MPa. In the biocompatibility tests, the round specimens with honeycomb filling also showed the highest cell count per mm², with 1591 ± 239 live cells/mm2 after 10 days and the highest value in cell proliferation, but with minimal cytotoxic effects (9.19 ± 2.47% after 3 days).

Characterization of Biological Properties of Dental Pulp Stem Cells Grown on an Electrospun Poly(l-lactide-co-caprolactone) Scaffold

Poly(l-lactide-co-caprolactone) (PLCL) electrospun scaffolds with seeded stem cells have drawn great interest in tissue engineering. This study investigated the biological behavior of human dental pulp stem cells (hDPSCs) grown on a hydrolytically-modified PLCL nanofiber scaffold. The hDPSCs were seeded on PLCL, and their biological features such as viability, proliferation, adhesion, population doubling time, the immunophenotype of hDPSCs and osteogenic differentiation capacity were evaluated on scaffolds. The results showed that the PLCL scaffold significantly supported hDPSC viability/proliferation. The hDPSCs adhesion rate and spreading onto PLCL increased with time of culture. hDPSCs were able to migrate inside the PLCL electrospun scaffold after 7 days of seeding. No differences in morphology and immunophenotype of hDPSCs grown on PLCL and in flasks were observed. The mRNA levels of bone-related genes and their proteins were significantly higher in hDPSCs after osteogenic differentiation on PLCL compared with undifferentiated hDPSCs on PLCL. These results showed that the mechanical properties of a modified PLCL mat provide an appropriate environment that supports hDPSCs attachment, proliferation, migration and their osteogenic differentiation on the PLCL scaffold. The good PLCL biocompatibility with dental pulp stem cells indicates that this mat may be applied in designing a bioactive hDPSCs/PLCL construct for bone tissue engineering.

Thomas L, Nair PD. Assessing the 3D Printability of an Elastomeric Poly(caprolactone-co-lactide) Copolymer as a Potential Material for 3D Printing Tracheal Scaffolds

The advent of 3D printing technology has made remarkable progress in the field of tissue engineering. Yet, it has been challenging to reproduce the desired mechanical properties of certain tissues by 3D printing. This was majorly due to the lack of 3D printable materials possessing mechanical properties similar to the native tissue. In this study, we have synthesized four different ratios of poly(caprolactone-co-lactide (PLCL) and tested their 3D printing capabilities. The physicochemical properties of the material were characterized using Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Furthermore, the mechanical properties were assessed using the universal testing machine (UTM). The ratio with the higher lactide content was found to have better printability. Out of the different ratios assessed, a suitable ratio having the desired mechanical properties and printability was identified and 3D printed into a tracheal scaffold. Thus, PLCL can be a potential material for 3D printing of tissues like the trachea.

Clinically relevant preclinical animal models for testing novel cranio-maxillofacial bone 3D-printed biomaterials

Bone tissue engineering is a rapidly developing field with potential for the regeneration of craniomaxillofacial (CMF) bones, with 3D printing being a suitable fabrication tool for patient-specific implants. The CMF region includes a variety of different bones with distinct functions. The clinical implementation of tissue engineering concepts is currently poor, likely due to multiple reasons including the complexity of the CMF anatomy and biology, and the limited relevance of the currently used preclinical models. The 'recapitulation of a human disease' is a core requisite of preclinical animal models, but this aspect is often neglected, with a vast majority of studies failing to identify the specific clinical indication they are targeting and/or the rationale for choosing one animal model over another. Currently, there are no suitable guidelines that propose the most appropriate animal model to address a specific CMF pathology and no standards are established to test the efficacy of biomaterials or tissue engineered constructs in the CMF field. This review reports the current clinical scenario of CMF reconstruction, then discusses the numerous limitations of currently used preclinical animal models employed for validating 3D-printed tissue engineered constructs and the need to reduce animal work that does not address a specific clinical question. We will highlight critical research aspects to consider, to pave a clinically driven path for the development of new tissue engineered materials for CMF reconstruction.

An additive manufacturing-based 3D printed poly ɛ-caprolactone/alginate sulfate/extracellular matrix construct for nasal cartilage regeneration

Various composite scaffolds with different fabrication techniques have been applied in cartilage tissue engineering. In this study, poly ɛ-caprolactone (PCL) was printed by fused deposition modeling method, and the prepared scaffold was filled with Alginate (Alg): Alginate-Sulfate (Alg-Sul) hydrogel to provide a better biomimetic environment and emulate the structure of glycosaminoglycans properly. Furthermore, to enhance chondrogenesis, different concentrations of decellularized extracellular matrix (dECM) were added to the hydrogel. For cellular analyses, the adipose-derived mesenchymal stem cells were seeded on the hydrogel and the results of MTT assay, live/dead staining, and SEM images revealed that the scaffold with 1% dECM had better viscosity, cell viability, and proliferation. The study was conducted on the optimized scaffold (1% dECM) to determine mechanical characteristics, chondrogenic differentiation, and results demonstrated that the scaffold showed mechanical similarity to the native nasal cartilage tissue along with possessing appropriate biochemical features, which makes this new formulation based on PCL/dECM/Alg:Alg-Sul a promising candidate for further in-vivo studies.

Additive Manufacturing of α-Amino Acid Based Poly(ester amide)s for Biomedical Applications

α-Amino acid based polyester amides (PEAs) are promising candidates for additive manufacturing (AM), as they unite the flexibility and degradability of polyesters and good thermomechanical properties of polyamides in one structure. Introducing α-amino acids in the PEA structure brings additional advantages such as (i) good cytocompatibility and biodegradability, (ii) providing strong amide bonds, enhancing the hydrogen-bonding network, (iii) the introduction of pendant reactive functional groups, and (iv) providing good cell-polymer interactions. However, the application of α-amino acid based PEAs for AM via fused deposition modeling (FDM), an important manufacturing technique with unique processing characteristics and requirements, is still lacking. With the aim to exploit the combination of these advantages in the creation, design, and function of additively manufactured scaffolds using FDM, we report the structure-function relationship of a series of α-amino acid based PEAs. The PEAs with three different molecular weights were synthesized via the active solution polycondensation, and their performance for AM applications was studied in comparison with a commercial biomedical grade copolymer of l-lactide and glycolide (PLGA). The PEAs, in addition to good thermal stability, showed semicrystalline behavior with proper mechanical properties, which were different depending on their molecular weight and crystallinity. They showed more ductility due to their lower glass transition temperature (T_g; 18-20 °C) compared with PLGA (57 °C). The rheology studies revealed that the end-capping of PEAs is of high importance for preventing cross-linking and further polymerization during the melt extrusion and for the steadiness and reproducibility of FDM. Furthermore, our data regarding the steady 3D printing performance, good polymer-cell interactions, and low cytotoxicity suggest that α-amino acid based PEAs can be introduced as favorable polymers for future AM applications in tissue engineering. In addition, their ability for formation of bonelike apatite in the simulated body fluid (SBF) indicates their potential for bone tissue engineering applications.

Vascularized bone regeneration accelerated by 3D-printed nanosilicate-functionalized polycaprolactone scaffold

Critical oral-maxillofacial bone defects, damaged by trauma and tumors, not only affect the physiological functions and mental health of patients but are also highly challenging to reconstruct. Personalized biomaterials customized by 3D printing technology have the potential to match oral-maxillofacial bone repair and regeneration requirements. Laponite (LAP) nanosilicates have been added to biomaterials to achieve biofunctional modification owing to their excellent biocompatibility and bioactivity. Herein, porous nanosilicate-functionalized polycaprolactone (PCL/LAP) was fabricated by 3D printing technology, and its bioactivities in bone regeneration were investigated in vitro and in vivo. In vitro experiments demonstrated that PCL/LAP exhibited good cytocompatibility and enhanced the viability of bone marrow mesenchymal stem cells (BMSCs). PCL/LAP functioned to stimulate osteogenic differentiation of BMSCs at the mRNA and protein levels and elevated angiogenic gene expression and cytokine secretion. Moreover, BMSCs cultured on PCL/LAP promoted the angiogenesis potential of endothelial cells by angiogenic cytokine secretion. Then, PCL/LAP scaffolds were implanted into the calvarial defect model. Toxicological safety of PCL/LAP was confirmed, and significant enhancement of vascularized bone formation was observed. Taken together, 3D-printed PCL/LAP scaffolds with brilliant osteogenesis to enhance bone regeneration could be envisaged as an outstanding bone substitute for a promising change in oral-maxillofacial bone defect reconstruction.

Application of dental stem cells in three-dimensional tissue regeneration

Dental stem cells can differentiate into different types of cells. Dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, stem cells from apical papilla, and dental follicle progenitor cells are five different types of dental stem cells that have been identified during different stages of tooth development. The availability of dental stem cells from discarded or removed teeth makes them promising candidates for tissue engineering. In recent years, three-dimensional (3D) tissue scaffolds have been used to reconstruct and restore different anatomical defects. With rapid advances in 3D tissue engineering, dental stem cells have been used in the regeneration of 3D engineered tissue. This review presents an overview of different types of dental stem cells used in 3D tissue regeneration, which are currently the most common type of stem cells used to treat human tissue conditions.

Bone regeneration in rat calvarial defects using dissociated or spheroid mesenchymal stromal cells in scaffold-hydrogel constructs

Background

Three-dimensional (3D) spheroid culture can promote the osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSC). 3D printing offers the possibility to produce customized scaffolds for complex bone defects. The aim of this study was to compare the potential of human BMSC cultured as 2D monolayers or 3D spheroids encapsulated in constructs of 3D-printed poly-L-lactide-co-trimethylene carbonate scaffolds and modified human platelet lysate hydrogels (PLATMC-HPLG) for bone regeneration.

Methods

PLATMC-HPLG constructs with 2D or 3D BMSC were assessed for osteogenic differentiation based on gene expression and in vitro mineralization. Subsequently, PLATMC-HPLG constructs with 2D or 3D BMSC were implanted in rat calvarial defects for 12 weeks; cell-free constructs served as controls. Bone regeneration was assessed via in vivo computed tomography (CT), ex vivo micro-CT and histology.

Results

Osteogenic gene expression was significantly enhanced in 3D versus 2D BMSC prior to, but not after, encapsulation in PLATMC-HPLG constructs. A trend for greater in vitro mineralization was observed in constructs with 3D versus 2D BMSC (p > 0.05). In vivo CT revealed comparable bone formation after 4, 8 and 12 weeks in all groups. After 12 weeks, micro-CT revealed substantial regeneration in 2D BMSC (62.47 ± 19.46%), 3D BMSC (51.01 ± 24.43%) and cell-free PLATMC-HPLG constructs (43.20 ± 30.09%) (p > 0.05). A similar trend was observed in the histological analysis.

Conclusion

Despite a trend for superior in vitro mineralization, constructs with 3D and 2D BMSC performed similarly in vivo. Regardless of monolayer or spheroid cell culture, PLATMC-HPLG constructs represent promising scaffolds for bone tissue engineering applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02642-w.

The Role of Blood Clot in Guided Bone Regeneration: Biological Considerations and Clinical Applications with Titanium Foil

In Guided Bone Regeneration (GBR) materials and techniques are essential to achieve the expected results. Thanks to their properties, blood clots induce bone healing, maturation, differentiation and organization. The preferred material to protect the clot in Guided Bone Regeneration is the titanium foil, as it can be shaped according to the bone defect. Furthermore, its exposition in the oral cavity does not impair the procedure. We report on five clinical cases in order to explain the management of blood clots in combination with titanium foil barriers in different clinical settings. Besides being the best choice to protect the clot, the titanium foil represents an excellent barrier that is useful in GBR due to its biocompatibility, handling, and mechanical strength properties. The clot alone is the best natural scaffold to obtain the ideal bone quality and avoid the persistence of not-resorbed granules of filler materials in the newly regenerated bone. Even though clot contraction still needs to be improved, as it impacts the volume of the regenerated bone, future studies in GBR should be inspired by the clot and its fundamental properties.

Nanosilicate-Functionalized Polycaprolactone Orchestrates Osteogenesis and Osteoblast-Induced Multicellular Interactions for Potential Endogenous Vascularized Bone Regeneration

Massive oral and maxillofacial bone defect regeneration remains a major clinical challenge due to the absence of functionalized bone grafts with ideal mechanical and proregeneration properties. In the present study, Laponite (LAP), a synthetic nanosilicate, is incorporated into polycaprolactone (PCL) to develop a biomaterial for bone regeneration. It is explored whether LAP-embedded PCL would accelerate bone regeneration by orchestrating osteoblasts to directly and indirectly induce bone regeneration processes. The results confirmed the presence of LAP in PCL, and LAP is distributed in the exfoliated structure without aggregates. Incorporation of LAP in PCL slightly improved the compressive properties. LAP-embedded PCL is biocompatible and exerts pronounced enhancements in cell viability, osteogenic differentiation, and extracellular matrix formation of osteoblasts. Furthermore, osteoblasts cultured on LAP-embedded PCL facilitate angiogenesis of vessel endothelial cells and alleviate osteoclastogenesis of osteoclasts in a paracrine manner. The addition of LAP to the PCL endows favorable bone formation in vivo. Based upon these results, LAP-embedded PCL shows great potential as an ideal bone graft that exerts both space-maintaining and vascularized bone regeneration synergistic effects and can be envisioned for oral and maxillofacial bone defect regeneration.

The integration of pore size and porosity distribution on Ti-6A1-4V scaffolds by 3D printing in the modulation of osteo-differentation

PURPOSE

In this study, pore size and porosity distribution of porous Ti-6Al-4V scaffolds (pTi) were controlled by 3D printing. The effects of pore size distribution at a constant porosity, or porosity distribution at a constant pore size pertaining to functions of adhesion, proliferation, and differentiation of the mouse embryonic osteoblast precursor (MC3T3-E1) cells were researched separately.

METHODS

3D printing was used to design five groups of pTi, designated as PS₃₀₀/HP, PS₃₀₀/LP, PS₅₀₀/HP, PS₅₀₀/LP, and PS₈₀₀/HP based on pore size and porosity distribution. MC3T3-E1 cells were cultured on pTi, and non-porous Ti-6Al-4V samples (npTi) were prepared as control. The pTi was characterized with the scanning electron microscopy (SEM). MC3T3-E1 cells were stained via AlamarBlue assay and viability and proliferation analyzed. The mRNA levels of alkaline phosphatase (ALP), osteocalcin (OCN), collagentype-1 (Col-1), and runt-related transcription factor 2 (Runx2) in MC3T3-E1 cells were analyzed by real-time PCR analysis.

RESULTS

The average pore size and porosity of pTi were recorded as (301 ± 9 μm, 58.8 ± 1.8%), (300 ± 9 μm, 43.4 ± 1.3%), (501 ± 11 μm, 58.3 ± 1.2%), (499 ± 12 μm, 42.7 ± 1.1%), and (804 ± 10 μm, 58.9 ± 1.3%), respectively. SEM images confirmed active attachment of cells and oriented with the direction of metal rod after pTi/MC3T3-E1 co-culture for 3 and 7 days. In addition, MC3T3-E1 cells grown on the PS₈₀₀/HP displayed significantly higher proliferation compared with each group after 3 days incubation (p < 0.05). Moreover, cells showed some degree of proliferation in all groups, with the highest value recorded for PS₈₀₀/HP after culture for 7 days (p < 0.05). The gene expression pattern of ALP, OCN, Col-1, and Runx2 confirmed that these were down-regulated when pore size increased or porosity decreased of pTi (p < 0.05).

CONCLUSION

The pTi facilitated the adhesion and differentiation of osteoblast when pore size decreased or porosity increased. The scaffold model resembles physical modification with porous structures, which has potential application in the surface modifications of Ti implant.

Bone formation with functionalized 3D printed poly-ε-caprolactone scaffold with plasma-rich-fibrin implanted in critical-sized calvaria defect of rat

Background/purpose

Space-making is one of the essential factors for bone regeneration in severe bony defect. To test the hypothesis that an appropriately designed scaffold may be beneficial for the bone formation in defect, the new bone formed in the critical-size calvarial defect of rat was examined after implanted with a 3D-printed poly-ɛ-caprolactone (PCL) scaffold, retaining with and without plasma rich fibrin (PRF).

Materials and methods

Thirty-two rats were divided into four groups (control, PCL, PRF, and PCL-plus-PRF). A custom-made 3D-printed PCL scaffold, 900 μm in pore size, retaining with and without PRF, was implanted into a critical-sized calvarial defect, 6 mm in diameter. Animals were sacrificed at week-4 or 8 after implantation for assessing the new bone formation by dental radiography, micro-computed tomography (μ-CT), and histology.

Results

By radiography and μ-CT, significantly greater mineralization areas/volumes were observed in defects with 3D-printed scaffold groups compared to that without the scaffold in both two-time points. However, no advantage was found by adding PRF. Histology showed that bone tissues grew into the central zone of the critical defect when 3D-printed PCL scaffold was present. In contrast, for the groups without the scaffolds, new bones were formed mostly along defect borders, and the central zones of the defects were collapsed and healed with thin connective tissue.

Conclusion

Our results suggest that the use of a 900 μm pore size 3D-printed PCL scaffold may have the potential in facilitating the new bone formation.

The Application of Polycaprolactone in Three-Dimensional Printing Scaffolds for Bone Tissue Engineering

Bone tissue engineering commonly encompasses the use of three-dimensional (3D) scaffolds to provide a suitable microenvironment for the propagation of cells to regenerate damaged tissues or organs. 3D printing technology has been extensively applied to allow direct 3D scaffolds manufacturing. Polycaprolactone (PCL) has been widely used in the fabrication of 3D scaffolds in the field of bone tissue engineering due to its advantages such as good biocompatibility, slow degradation rate, the less acidic breakdown products in comparison to other polyesters, and the potential for loadbearing applications. PCL can be blended with a variety of polymers and hydrogels to improve its properties or to introduce new PCL-based composites. This paper describes the PCL used in developing state of the art of scaffolds for bone tissue engineering. In this review, we provide an overview of the 3D printing techniques for the fabrication of PCL-based composite scaffolds and recent studies on applications in different clinical situations. For instance, PCL-based composite scaffolds were used as an implant surgical guide in dental treatment. Furthermore, future trend and potential clinical translations will be discussed.

Printing New Bones: From Print-and-Implant Devices to Bioprinted Bone Organ Precursors

Regenerating large bone defects remains a significant clinical challenge, motivating increased interest in additive manufacturing and 3D bioprinting to engineer superior bone graft substitutes. 3D bioprinting enables different biomaterials, cell types, and growth factors to be combined to develop patient-specific implants capable of directing functional bone regeneration. Current approaches to bioprinting such implants fall into one of two categories, each with their own advantages and limitations. First are those that can be 3D bioprinted and then directly implanted into the body and second those that require further in vitro culture after bioprinting to engineer more mature tissues prior to implantation. This review covers the key concepts, challenges, and applications of both strategies to regenerate damaged and diseased bone.

Clinical Safety Assessment of Autologous Freeze-Drying Platelet-Rich Plasma for Bone Regeneration in Maxillary Sinus Floor Augmentation: A Pilot Study

The purpose of this clinical study is to evaluate the safety and preliminary efficacy of autologous freeze-drying platelet-rich plasma (FD-PRP) on bone regeneration in maxillary sinus floor augmentation as a preliminary pilot study. Five patients that required sinus floor augmentation to facilitate the placement of dental implants participated in this clinical study. The PRP was prepared from the autologous peripheral blood and was lyophilized and stored at −20 °C for 4 weeks before surgery. At surgery, triple-concentrated FD-PRP (x3FD-PRP) mixed with synthetic bone grafting materials was rehydrated following the transplantation into the sinus floor. The primary outcome was a safety verification of x3FD-PRP, evaluated in terms of the clinical course and consecutive blood tests. The secondary outcome was clinical efficacy focused on bone regeneration in sinus floor augmentation evaluated by radiographic examination and implant stability. There were no adverse events, such as systemic complications, excessive inflammatory reactions, severe infection, or local site healing complications, besides those on the usual course associated with surgery. Vertical augmented height was maintained, and the initial stability of implants was achieved post-operatively in 6 months. The results obtained in this study suggest that x3FD-PRP can be used safely for bone engineering in clinical practice. Further studies are required to draw a conclusion concerning the efficacy of x3FD-PRP since this was a pilot study with a single arm and a small sample size.

Facile modification of polycaprolactone nanofibers with egg white protein

Synthetic polymers remain to be a major choice for scaffold fabrication due to their structural stability and mechanical strength. However, the lack of functional moieties limits their application for cell-based therapies which necessitate modification and functionalization. Blending synthetic polymers with natural components is a simple and effective way to achieve the desired biological properties for a scaffold. Herein, nanofibrous mats made of polycaprolactone (PCL) and egg white protein (EWP) blend were developed and further evaluated for use as a scaffold for tissue engineering applications. Homogeneous distribution of EWP was achieved throughout the nanofibrous mats, as shown by immunohistochemistry. ATR-FTIR analysis and contact angle measurements have further confirmed the presence of EWP on the surface of the samples. The swelling test showed that PCL/EWP nanofibers have higher water uptake than PCL nanofibrous mats. Also, EWP addition on the nanofibrous mats resulted in an increase in the tensile strength and Young's modulus of the mats, indicating that the presence of protein can greatly enhance the mechanical properties of the mats. A significantly higher, more uniform, and dispersed cell spreading was observed on days 7 and 14 than that on neat PCL mats, demonstrating the importance of providing the required cues for cell homing by the availability of EWP. Hence, EWP is shown to be a simple and low-cost source for the functionalization of PCL nanofibrous mats. EWP is, therefore, a facile candidate to enhance cellular interactions of synthetic polymers for a wide range of tissue engineering applications.

Potential of Lyophilized Platelet Concentrates for Craniofacial Tissue Regenerative Therapies

Objective: The use of platelet concentrates (PCs) in oral and maxillofacial surgery, periodontology, and craniofacial surgery has been reported. While PCs provide a rich reservoir of autologous bioactive growth factors for tissue regeneration, their drawbacks include lack of utility for long-term application, low elastic modulus and strength, and limited storage capability. These issues restrict their broader application. This review focuses on the lyophilization of PCs (LPCs) and how this processing approach affects their biological and mechanical properties for application as a bioactive scaffold for craniofacial tissue regeneration. Materials and Methods: A comprehensive search of five electronic databases, including Medline, PubMed, EMBASE, Web of Science, and Scopus, was conducted from 1946 until 2019 using a combination of search terms relating to this topic. Results: Ten manuscripts were identified as being relevant. The use of LPCs was mostly studied in in vitro and in vivo craniofacial bone regeneration models. Notably, one clinical study reported the utility of LPCs for guided bone regeneration prior to dental implant placement. Conclusions: Lyophilization can enhance the inherent characteristics of PCs and extends shelf-life, enable their use in emergency surgery, and improve storage and transportation capabilities. In light of this, further preclinical studies and clinical trials are required, as LPCs offer a potential approach for clinical application in craniofacial tissue regeneration.

A Current Overview of Scaffold-Based Bone Regeneration Strategies with Dental Stem Cells

Bone defects due to trauma or diseases still pose a clinical challenge to be resolved in the current tissue engineering approaches. As an alternative to traditional methods to restore bone defects, such as autografts, bone tissue engineering aims to achieve new bone formation via novel biomaterials used in combination with multipotent stem cells and bioactive molecules. Mesenchymal stem cells (MSCs) can be successfully isolated from various dental tissues at different stages of development including dental pulp, apical papilla, dental follicle, tooth germ, deciduous teeth, periodontal ligament and gingiva. A wide range of biomaterials including polymers, ceramics and composites have been investigated for their potential as an ideal bone scaffold material. This article reviews the properties and the manufacturing methods of biomaterials used in bone tissue engineering, and provides an overview of bone tissue regeneration approaches of scaffold and dental stem cell combinations as well as their limitations.

Evaluation of Bone Gain and Complication Rates after Guided Bone Regeneration with Titanium Foils: A Systematic Review

Guided bone regeneration techniques are increasingly used to enable the subsequent placement of dental implants. This systematic review aims to analyze the success rate of these techniques in terms of bone gain and complications rate using titanium membranes as a barrier element. Electronic and hand searches were conducted in PubMed/Medline, Scielo, Scopus and Cochrane Library databases for case reports, case series, cohort studies and clinical trials in humans published up to and including 19 September 2020. Thirteen articles were included in the qualitative analysis. Bone gain both horizontally and vertically was comparable to that obtained with other types of membranes more commonly used. The postoperative complication rate was higher that of native collagen membranes and non-resorbable titanium-reinforced membranes, and similar that of crosslinked collagen membranes and titanium meshes. The survival rate of the implants was similar to that of implants placed in native bone. Due to the limited scientific literature published on this issue, more randomized clinical trials comparing occlusive titanium barriers and other types of membranes are necessary to reach more valid conclusions.

3D bioprinting and craniofacial regeneration

BACKGROUND

Considering the structural and functional complexity of the craniofacial tissues, 3D bioprinting can be a valuable tool to design and create functional 3D tissues or organs in situ for in vivo applications. This review aims to explore the various aspects of this emerging 3D bioprinting technology and its application in the craniofacial bone or cartilage regeneration.

METHOD

Electronic database searches were undertaken on pubmed, google scholar, medline, embase, and science direct for english language literature, published for 3D bioprinting in craniofacial regeneration. The search items used were 'craniofacial regeneration' OR 'jaw regeneration' OR 'maxillofacial regeneration' AND '3D bioprinting' OR 'three dimensional bioprinting' OR 'Additive manufacturing' OR 'rapid prototyping' OR 'patient specific bioprinting'. Reviews and duplicates were excluded.

RESULTS

Search with above described criteria yielded 476 articles, which reduced to 108 after excluding reviews. Further screening of individual articles led to 77 articles to which 9 additional articles were included from references, and 18 duplicate articles were excluded. Finally we were left with 68 articles to be included in the review.

CONCLUSION

Craniofacial tissue and organ regeneration has been reported a success using bioink with different biomaterial and incorporated stem cells in 3D bioprinters. Though several attempts have been made to fabricate craniofacial bone and cartilage, the strive to achieve desired outcome still continues.

Freeze-Drying of Platelet-Rich Plasma: The Quest for Standardization

The complex biology of platelets and their involvement in tissue repair and inflammation have inspired the development of platelet-rich plasma (PRP) therapies for a broad array of medical needs. However, clinical advances are hampered by the fact that PRP products, doses and treatment protocols are far from being standardized. Freeze-drying PRP (FD-PRP) preserves platelet function, cytokine concentration and functionality, and has been proposed as a consistent method for product standardization and fabrication of an off-the-shelf product with improved stability and readiness for future uses. Here, we present the current state of experimental and clinical FD-PRP research in the different medical areas in which PRP has potential to meet prevailing medical needs. A systematic search, according to PRISMA (Preferred Reported Items for Systematic Reviews and Meta-Analyses) guidelines, showed that research is mostly focused on wound healing, i.e., developing combination products for ulcer management. Injectable hydrogels are investigated for lumbar fusion and knee conditions. In dentistry, combination products permit slow kinetics of growth factor release and functionalized membranes for guided bone regeneration.

Influence of Material Structure on Forces Measured during Abrasive Waterjet (AWJ) Machining

Material structure is one of the important factors influencing abrasive waterjet (AWJ) machining efficiency and quality. The force measurements were performed on samples prepared from two very similar steels with different thicknesses and heat treatment. The samples were austenitized at 850 °C, quenched in polymer and tempered at various temperatures between 20 °C and 640 °C. The resulting states of material substantially differed in strength and hardness. Therefore, samples prepared from these material states are ideal for testing of material response to AWJ. The force measurements were chosen to test the possible influence of material structure on the material response to the AWJ impact. The results show that differences in material structure and respective material properties influence the limit traverse speed. The cutting to deformation force ratio seems to be a function of relative traverse speed independently on material structure.

Evaluation of the osteogenic potential of rat adipose-derived stem cells with different polycaprolactone/alginate-based nanofibrous scaffolds: an in vitro study

Background

Bone tissue engineering is a widely growing field that requires the combination of cells, scaffolds and signaling molecules. Adipose derived stem cells (ADSCs) are an accessible and abundant source of mesenchymal stem cells with high plasticity. Polycaprolactone/alginate (PCL/Alg) composite scaffolds have been used in bone regeneration and nano-hydroxyapatite (n-HA) is used as a reinforcing, osteoconductive component in scaffold fabrication. This study was conducted to assess the ability of three different PCL/Alg based scaffolds to induce osteogenic differentiation of ADSCs and to compare between them.

Methods

The study comprised 5 groups; negative control group with ADSCs cultured in complete culture media, positive control group with ADSCs cultured in osteogenic differentiation media, and 3 experimental groups with ADSCs seeded onto 3 scaffolds: S1 (PCL/Alg), S2 (PCL/Alg/Ca) and S3 (PCL/Alg/Ca/n-HA) respectively and cultured in osteogenic media. Mineralization and gene expression were assessed by Alizarin red S (ARS) staining and real time quantitative polymerase chain reaction (RT-qPCR). Evaluation was done at 7, 14 and 21 days.

Results

ARS staining reflected a time dependent increase through days 7, 14 and 21, with S3 (PCL/Alg/Ca/n-HA) group showing the highest mineralization levels. RT-qPCR detected upregulation of ALP gene expression at day 7 and decline thereafter. S2 (PCL/Alg/Ca) and S3 (PCL/Alg/Ca/n-HA) groups showed significantly higher gene expression levels than S1 (PCL/Alg).

Conclusions

ADSCs and PCL/Alg-based scaffolds compose a good tissue engineering complex for bone regeneration. Addition of n-HA to PCL/Alg scaffolds and crosslinking with CaCl2 efficiently improve the osteogenic potential of ADSCs.

Current Trends in Research on Bone Regeneration: A Bibliometric Analysis

Background

Bone regeneration is a frequent research topic in clinical studies, but macroscopic studies on the clinical application of bone regeneration are rare. We conducted a bibliometric analysis, using international databases, to explore the clinical application and mechanism of bone regeneration, to highlight the relevant research hotspots and prospects. Material and Methods. Scientific reports on bone regeneration published during 2009–2019 were retrieved from PubMed. VOSviewer for cooccurrence keywords and authorship analysis. BICOMB software was used to retrieve high-frequency words and construct a text/coword matrix. The matrix was inputted into gCLUTO software, managed by biclustering analysis, in order to identify hotspots, which could achieve mountain and matrix visualizations. The matrix was also analyzed by using Ucinet 6 software for social network analysis. A strategic diagram was used for further analysis of the research hotspots of bone regeneration by “SCIMAT” software. We searched the Web of Science for relevant articles.

Results

Eighty-nine high-frequency major MeSH terms were obtained from 10237 articles and were divided into 5 clusters. We generated a network visualization map, an overlay visualization mountain map, and a social network diagram. Then, the MeSH terms were subdivided into 7 categories according to each diagram; current research hotspots were identified as scaffold, drug effect, osseointegration in dental implant, guided bone regeneration, factors impacting bone regeneration, treatment of bone and tissue loss, and bone regeneration in dental implants.

Conclusion

BICOMB, VOSviewer, and other bibliometric tools revealed that dental implants, scaffolds, and factors impacting bone regeneration are hot research topics, while scaffolds also hold promise from the perspective of bone tissue regeneration.

3D printing of silk fibroin-based hybrid scaffold treated with platelet rich plasma for bone tissue engineering

3D printing/bioprinting are promising techniques to fabricate scaffolds with well controlled and patient-specific structures and architectures for bone tissue engineering. In this study, we developed a composite bioink consisting of silk fibroin (SF), gelatin (GEL), hyaluronic acid (HA), and tricalcium phosphate (TCP) and 3D bioprinted the silk fibroin-based hybrid scaffolds. The 3D bioprinted scaffolds with dual crosslinking were further treated with human platelet-rich plasma (PRP) to generate PRP coated scaffolds. Live/Dead and MTT assays demonstrated that PRP treatment could obviously promote the cell growth and proliferation of human adipose derived mesenchymal stem cells (HADMSC). In addition, the treatment of PRP did not significantly affect alkaline phosphatase (ALP) activity and expression, but significantly upregulated the gene expression levels of late osteogenic markers. This study demonstrated that the 3D printing of silk fibroin-based hybrid scaffolds, in combination with PRP post-treatment, might be a more efficient strategy to promote osteogenic differentiation of adult stem cells and has significant potential to be used for bone tissue engineering.

•

3D printing technology was used to fabricate silk fibroin-based hybrid scaffold for bone tissue engineering.

•

Human platelet-rich plasma (PRP) was obtained and implemented to treat 3D printed scaffolds.

•

The PRP treated composite scaffold improved cell proliferation and increased late marker of osteogenic gene expression.