1
|
Chandra DK, Reis RL, Kundu SC, Kumar A, Mahapatra C. Nanomaterials-Based Hybrid Bioink Platforms in Advancing 3D Bioprinting Technologies for Regenerative Medicine. ACS Biomater Sci Eng 2024. [PMID: 38822783 DOI: 10.1021/acsbiomaterials.4c00166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2024]
Abstract
3D bioprinting is recognized as the ultimate additive biomanufacturing technology in tissue engineering and regeneration, augmented with intelligent bioinks and bioprinters to construct tissues or organs, thereby eliminating the stipulation for artificial organs. For 3D bioprinting of soft tissues, such as kidneys, hearts, and other human body parts, formulations of bioink with enhanced bioinspired rheological and mechanical properties were essential. Nanomaterials-based hybrid bioinks have the potential to overcome the above-mentioned problem and require much attention among researchers. Natural and synthetic nanomaterials such as carbon nanotubes, graphene oxides, titanium oxides, nanosilicates, nanoclay, nanocellulose, etc. and their blended have been used in various 3D bioprinters as bioinks and benefitted enhanced bioprintability, biocompatibility, and biodegradability. A limited number of articles were published, and the above-mentioned requirement pushed us to write this review. We reviewed, explored, and discussed the nanomaterials and nanocomposite-based hybrid bioinks for the 3D bioprinting technology, 3D bioprinters properties, natural, synthetic, and nanomaterial-based hybrid bioinks, including applications with challenges, limitations, ethical considerations, potential solution for future perspective, and technological advancement of efficient and cost-effective 3D bioprinting methods in tissue regeneration and healthcare.
Collapse
Affiliation(s)
- Dilip Kumar Chandra
- Department of Biotechnology, National Institute of Technology Raipur, G.E. Road, Raipur, Chhattisgarh 492010, India
| | - Rui L Reis
- 3Bs Research Group, I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Barco, Guimarães 4805-017, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Guimarães 4800-058, Braga,Portugal
| | - Subhas C Kundu
- 3Bs Research Group, I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Barco, Guimarães 4805-017, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Guimarães 4800-058, Braga,Portugal
| | - Awanish Kumar
- Department of Biotechnology, National Institute of Technology Raipur, G.E. Road, Raipur, Chhattisgarh 492010, India
| | - Chinmaya Mahapatra
- Department of Biotechnology, National Institute of Technology Raipur, G.E. Road, Raipur, Chhattisgarh 492010, India
| |
Collapse
|
2
|
Kim JY, Kumar SB, Park CH, Kim CS. Development of cell-laden photopolymerized constructs with bioactive amorphous calcium magnesium phosphate for bone tissue regeneration via 3D bioprinting. Int J Biol Macromol 2024; 267:131412. [PMID: 38593894 DOI: 10.1016/j.ijbiomac.2024.131412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/05/2024] [Accepted: 03/15/2024] [Indexed: 04/11/2024]
Abstract
The synthesis of ideal bioceramics to guide the fate of cells and subsequent bone regeneration within the chemical, biological, and physical microenvironment is a challenging long-term task. This study developed amorphous calcium magnesium phosphate (ACMP) bioceramics via a simple co-precipitation method. The role of Mg2+ in the formation of ACMP is investigated using physicochemical and biological characterization at different Ca/Mg molar ratio of the initial reaction solution. Additionally, ACMP bioceramics show superior cytocompatibility and improved osteogenic differentiation of co-cultured MC3T3-E1 cells. Regulation of the microenvironment with Mg2+ can promote early-stage bone regeneration. For this, bioprinting technology is employed to prepare ACMP-modified 3D porous structures. Our hypothesis is that the incorporation of ACMP into methacrylated gelatin (GelMA) bioink can trigger the osteogenic differentiation of encapsulated preosteoblast and stimulate bone regeneration. The cell-laden ACMP composite structures display stable printability and superior cell viability and cell proliferation. Also, constructs loading the appropriate amount of ACMP bioceramic showed significant osteogenic differentiation activity compared to the pure GelMA. We demonstrate that the dissolved Mg2+ cation microenvironment in ACMP-modified composite constructs plays an effective biochemical role, and can regulate cell fate. Our results predict that GelMA/ACMP bioink has significant potential in patient-specific bone tissue regeneration.
Collapse
Affiliation(s)
- Ju Yeon Kim
- Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea; Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea
| | - Shrestha Bishnu Kumar
- Department of Chemical, Biological, and Bioengineering, North Carolina A&T State University, Greensboro, NC 27411, USA
| | - Chan Hee Park
- Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea; Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea; Department of Mechanical Design Engineering, Jeonbuk National University, Jeonju 561-756, Republic of Korea.
| | - Cheol Sang Kim
- Department of Bionanosystem Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea; Department of Bionanotechnology and Bioconvergence Engineering, Graduate School, Jeonbuk National University, Jeonju 561-756, Republic of Korea; Department of Mechanical Design Engineering, Jeonbuk National University, Jeonju 561-756, Republic of Korea.
| |
Collapse
|
3
|
Das S, Jegadeesan JT, Basu B. Gelatin Methacryloyl (GelMA)-Based Biomaterial Inks: Process Science for 3D/4D Printing and Current Status. Biomacromolecules 2024; 25:2156-2221. [PMID: 38507816 DOI: 10.1021/acs.biomac.3c01271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
Tissue engineering for injured tissue replacement and regeneration has been a subject of investigation over the last 30 years, and there has been considerable interest in using additive manufacturing to achieve these goals. Despite such efforts, many key questions remain unanswered, particularly in the area of biomaterial selection for these applications as well as quantitative understanding of the process science. The strategic utilization of biological macromolecules provides a versatile approach to meet diverse requirements in 3D printing, such as printability, buildability, and biocompatibility. These molecules play a pivotal role in both physical and chemical cross-linking processes throughout the biofabrication, contributing significantly to the overall success of the 3D printing process. Among the several bioprintable materials, gelatin methacryloyl (GelMA) has been widely utilized for diverse tissue engineering applications, with some degree of success. In this context, this review will discuss the key bioengineering approaches to identify the gelation and cross-linking strategies that are appropriate to control the rheology, printability, and buildability of biomaterial inks. This review will focus on the GelMA as the structural (scaffold) biomaterial for different tissues and as a potential carrier vehicle for the transport of living cells as well as their maintenance and viability in the physiological system. Recognizing the importance of printability toward shape fidelity and biophysical properties, a major focus in this review has been to discuss the qualitative and quantitative impact of the key factors, including microrheological, viscoelastic, gelation, shear thinning properties of biomaterial inks, and printing parameters, in particular, reference to 3D extrusion printing of GelMA-based biomaterial inks. Specifically, we emphasize the different possibilities to regulate mechanical, swelling, biodegradation, and cellular functionalities of GelMA-based bio(material) inks, by hybridization techniques, including different synthetic and natural biopolymers, inorganic nanofillers, and microcarriers. At the close, the potential possibility of the integration of experimental data sets and artificial intelligence/machine learning approaches is emphasized to predict the printability, shape fidelity, or biophysical properties of GelMA bio(material) inks for clinically relevant tissues.
Collapse
Affiliation(s)
- Soumitra Das
- Materials Research Centre, Indian Institute of Science, Bangalore, India 560012
| | | | - Bikramjit Basu
- Materials Research Centre, Indian Institute of Science, Bangalore, India 560012
| |
Collapse
|
4
|
Zimmerling A, Sunil C, Zhou Y, Chen X. Development of a Nanoparticle System for Controlled Release in Bioprinted Respiratory Scaffolds. J Funct Biomater 2024; 15:20. [PMID: 38248687 PMCID: PMC10816437 DOI: 10.3390/jfb15010020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 12/21/2023] [Accepted: 01/05/2024] [Indexed: 01/23/2024] Open
Abstract
The use of nanoparticle systems for the controlled release of growth factors is a promising approach to mimicking of the biochemical environment of native tissues in tissue engineering. However, sustaining growth factor release inside an appropriate therapeutic window is a challenge, particularly in bioprinted scaffolds. In this study, a chitosan-coated alginate-based nanoparticle system loaded with hepatocyte growth factor was developed and then incorporated into bioprinted scaffolds. The release kinetics were investigated with a focus on identifying the impact of the chitosan coating and culture conditions. Our results demonstrated that the chitosan coating decreased the release rate and lessened the initial burst release, while culturing in dynamic conditions had no significant impact compared to static conditions. The nanoparticles were then incorporated into bioinks at various concentrations, and scaffolds with a three-dimensional (3D) structure were bioprinted from the bioinks containing human pulmonary fibroblasts and bronchial epithelial cells to investigate the potential use of a controlled release system in respiratory tissue engineering. It was found that the bioink loaded with a concentration of 4 µg/mL of nanoparticles had better printability compared to other concentrations, while the mechanical stability of the scaffolds was maintained over a 14-day culture period. The examination of the incorporated cells demonstrated a high degree of viability and proliferation with visualization of the beginning of an epithelial barrier layer. Taken together, this study demonstrates that a chitosan-coated alginate-based nanoparticle system allows the sustained release of growth factors in bioprinted respiratory tissue scaffolds.
Collapse
Affiliation(s)
- Amanda Zimmerling
- Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada (X.C.)
- Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada;
| | - Christina Sunil
- Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada (X.C.)
| | - Yan Zhou
- Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada;
| | - Xiongbiao Chen
- Division of Biomedical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada (X.C.)
- Department of Mechanical Engineering, College of Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada
| |
Collapse
|
5
|
Patrocinio D, Galván-Chacón V, Gómez-Blanco JC, Miguel SP, Loureiro J, Ribeiro MP, Coutinho P, Pagador JB, Sanchez-Margallo FM. Biopolymers for Tissue Engineering: Crosslinking, Printing Techniques, and Applications. Gels 2023; 9:890. [PMID: 37998980 PMCID: PMC10670821 DOI: 10.3390/gels9110890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 11/02/2023] [Accepted: 11/07/2023] [Indexed: 11/25/2023] Open
Abstract
Currently, tissue engineering has been dedicated to the development of 3D structures through bioprinting techniques that aim to obtain personalized, dynamic, and complex hydrogel 3D structures. Among the different materials used for the fabrication of such structures, proteins and polysaccharides are the main biological compounds (biopolymers) selected for the bioink formulation. These biomaterials obtained from natural sources are commonly compatible with tissues and cells (biocompatibility), friendly with biological digestion processes (biodegradability), and provide specific macromolecular structural and mechanical properties (biomimicry). However, the rheological behaviors of these natural-based bioinks constitute the main challenge of the cell-laden printing process (bioprinting). For this reason, bioprinting usually requires chemical modifications and/or inter-macromolecular crosslinking. In this sense, a comprehensive analysis describing these biopolymers (natural proteins and polysaccharides)-based bioinks, their modifications, and their stimuli-responsive nature is performed. This manuscript is organized into three sections: (1) tissue engineering application, (2) crosslinking, and (3) bioprinting techniques, analyzing the current challenges and strengths of biopolymers in bioprinting. In conclusion, all hydrogels try to resemble extracellular matrix properties for bioprinted structures while maintaining good printability and stability during the printing process.
Collapse
Affiliation(s)
- David Patrocinio
- CCMIJU, Bioengineering and Health Technologies, Jesus Usón Minimally Invasive Surgery Center, 10071 Cáceres, Spain; (D.P.); (V.G.-C.); (J.B.P.)
| | - Victor Galván-Chacón
- CCMIJU, Bioengineering and Health Technologies, Jesus Usón Minimally Invasive Surgery Center, 10071 Cáceres, Spain; (D.P.); (V.G.-C.); (J.B.P.)
| | - J. Carlos Gómez-Blanco
- CCMIJU, Bioengineering and Health Technologies, Jesus Usón Minimally Invasive Surgery Center, 10071 Cáceres, Spain; (D.P.); (V.G.-C.); (J.B.P.)
| | - Sonia P. Miguel
- CPIRN-IPG, Center of Potential and Innovation of Natural Resources, Polytechnic of Guarda, 6300-559 Guarda, Portugal (M.P.R.)
- CICS-UBI, Health Science Research Center, University of Beira Interior, 6201-506 Covilhã, Portugal
| | - Jorge Loureiro
- CPIRN-IPG, Center of Potential and Innovation of Natural Resources, Polytechnic of Guarda, 6300-559 Guarda, Portugal (M.P.R.)
| | - Maximiano P. Ribeiro
- CPIRN-IPG, Center of Potential and Innovation of Natural Resources, Polytechnic of Guarda, 6300-559 Guarda, Portugal (M.P.R.)
- CICS-UBI, Health Science Research Center, University of Beira Interior, 6201-506 Covilhã, Portugal
| | - Paula Coutinho
- CPIRN-IPG, Center of Potential and Innovation of Natural Resources, Polytechnic of Guarda, 6300-559 Guarda, Portugal (M.P.R.)
- CICS-UBI, Health Science Research Center, University of Beira Interior, 6201-506 Covilhã, Portugal
| | - J. Blas Pagador
- CCMIJU, Bioengineering and Health Technologies, Jesus Usón Minimally Invasive Surgery Center, 10071 Cáceres, Spain; (D.P.); (V.G.-C.); (J.B.P.)
- CIBER CV, Centro de Investigación Biomédica en Red—Enfermedades Cardiovasculares, 28029 Madrid, Spain;
| | - Francisco M. Sanchez-Margallo
- CIBER CV, Centro de Investigación Biomédica en Red—Enfermedades Cardiovasculares, 28029 Madrid, Spain;
- Scientific Direction, Jesus Usón Minimally Invasive Surgery Center, 10071 Cáceres, Spain
- TERAV/ISCIII, Red Española de Terapias Avanzadas, Instituto de Salud Carlos III (RICORS, RD21/0017/0029), 28029 Madrid, Spain
| |
Collapse
|
6
|
Brooks AK, Ramsey RG, Zhang N, Yadavalli VK. Tunable Light-Actuated Interpenetrating Networks of Silk Fibroin and Gelatin for Tissue Engineering and Flexible Biodevices. ACS Biomater Sci Eng 2023; 9:5793-5803. [PMID: 37698556 DOI: 10.1021/acsbiomaterials.3c00741] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
Soft materials with tunable properties are valuable for applications such as tissue engineering, electronic skins, and human-machine interfaces. Materials that are nature-derived offer additional advantages such as biocompatibility, biodegradability, low-cost sourcing, and sustainability. However, these materials often have contrasting properties that limit their use. For example, silk fibroin (SF) has high mechanical strength but lacks processability and cell-adhesive domains. Gelatin, derived from collagen, has excellent biological properties, but is fragile and lacks stability. To overcome these limitations, composites of gelatin and SF have been explored. However, mechanically robust self-supported matrices and electrochemically active or micropatterned substrates were not demonstrated. In this study, we present a composite of photopolymerizable SF and photogelatin, termed photofibrogel (PFG). By incorporating photoreactive properties in both SF and gelatin, control over material properties can be achieved. The PFG composite can be easily and rapidly formed into free-standing, high-resolution architectures with tunable properties. By optimizing the ratio of SF to gelatin, properties such as swelling, mechanical behavior, enzymatic degradation, and patternability are tailored. The PFG composite allows for macroscale and microscale patterning without significant swelling, enabling the fabrication of structures using photolithography and laser cutting techniques. PFG can be patterned with electrically conductive materials, making it suitable for cell guidance and stimulation. The versatility, mechanical robustness, bioactivity, and electrochemical properties of PFG are shown for skeletal muscle tissue engineering using C2C12 cells as a model. Overall, such composite biomaterials with tunable properties have broad potential in flexible bioelectronics, wound healing, regenerative medicine, and food systems.
Collapse
|
7
|
Cavallo A, Al Kayal T, Mero A, Mezzetta A, Guazzelli L, Soldani G, Losi P. Fibrinogen-Based Bioink for Application in Skin Equivalent 3D Bioprinting. J Funct Biomater 2023; 14:459. [PMID: 37754873 PMCID: PMC10532308 DOI: 10.3390/jfb14090459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/25/2023] [Accepted: 08/31/2023] [Indexed: 09/28/2023] Open
Abstract
Three-dimensional bioprinting has emerged as an attractive technology due to its ability to mimic native tissue architecture using different cell types and biomaterials. Nowadays, cell-laden bioink development or skin tissue equivalents are still at an early stage. The aim of the study is to propose a bioink to be used in skin bioprinting based on a blend of fibrinogen and alginate to form a hydrogel by enzymatic polymerization with thrombin and by ionic crosslinking with divalent calcium ions. The biomaterial ink formulation, composed of 30 mg/mL of fibrinogen, 6% of alginate, and 25 mM of CaCl2, was characterized in terms of homogeneity, rheological properties, printability, mechanical properties, degradation rate, water uptake, and biocompatibility by the indirect method using L929 mouse fibroblasts. The proposed bioink is a homogeneous blend with a shear thinning behavior, excellent printability, adequate mechanical stiffness, porosity, biodegradability, and water uptake, and it is in vitro biocompatible. The fibrinogen-based bioink was used for the 3D bioprinting of the dermal layer of the skin equivalent. Three different normal human dermal fibroblast (NHDF) densities were tested, and better results in terms of viability, spreading, and proliferation were obtained with 4 × 106 cell/mL. The skin equivalent was bioprinted, adding human keratinocytes (HaCaT) through bioprinting on the top surface of the dermal layer. A skin equivalent stained by live/dead and histological analysis immediately after printing and at days 7 and 14 of culture showed a tissuelike structure with two distinct layers characterized by the presence of viable and proliferating cells. This bioprinted skin equivalent showed a similar native skin architecture, paving the way for its use as a skin substitute for wound healing applications.
Collapse
Affiliation(s)
- Aida Cavallo
- Institute of Life Sciences, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
- Institute of Clinical Physiology, National Research Council, 54100 Massa, Italy
| | - Tamer Al Kayal
- Institute of Clinical Physiology, National Research Council, 54100 Massa, Italy
| | - Angelica Mero
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Andrea Mezzetta
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | | | - Giorgio Soldani
- Institute of Clinical Physiology, National Research Council, 54100 Massa, Italy
| | - Paola Losi
- Institute of Clinical Physiology, National Research Council, 54100 Massa, Italy
| |
Collapse
|
8
|
Zhe M, Wu X, Yu P, Xu J, Liu M, Yang G, Xiang Z, Xing F, Ritz U. Recent Advances in Decellularized Extracellular Matrix-Based Bioinks for 3D Bioprinting in Tissue Engineering. MATERIALS (BASEL, SWITZERLAND) 2023; 16:3197. [PMID: 37110034 PMCID: PMC10143913 DOI: 10.3390/ma16083197] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/30/2023] [Accepted: 04/15/2023] [Indexed: 06/19/2023]
Abstract
In recent years, three-dimensional (3D) bioprinting has been widely utilized as a novel manufacturing technique by more and more researchers to construct various tissue substitutes with complex architectures and geometries. Different biomaterials, including natural and synthetic materials, have been manufactured into bioinks for tissue regeneration using 3D bioprinting. Among the natural biomaterials derived from various natural tissues or organs, the decellularized extracellular matrix (dECM) has a complex internal structure and a variety of bioactive factors that provide mechanistic, biophysical, and biochemical signals for tissue regeneration and remodeling. In recent years, more and more researchers have been developing the dECM as a novel bioink for the construction of tissue substitutes. Compared with other bioinks, the various ECM components in dECM-based bioink can regulate cellular functions, modulate the tissue regeneration process, and adjust tissue remodeling. Therefore, we conducted this review to discuss the current status of and perspectives on dECM-based bioinks for bioprinting in tissue engineering. In addition, the various bioprinting techniques and decellularization methods were also discussed in this study.
Collapse
Affiliation(s)
- Man Zhe
- Animal Experiment Center, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Xinyu Wu
- West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
| | - Peiyun Yu
- LIMES Institute, Department of Molecular Brain Physiology and Behavior, University of Bonn, Carl-Troll-Str. 31, 53115 Bonn, Germany
| | - Jiawei Xu
- Orthopedic Research Institute, Department of Orthopedics, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Ming Liu
- Orthopedic Research Institute, Department of Orthopedics, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Guang Yang
- Animal Experiment Center, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Zhou Xiang
- Orthopedic Research Institute, Department of Orthopedics, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Fei Xing
- Department of Orthopaedics and Traumatology, Biomatics Group, University Medical Center of the Johannes Gutenberg University, Langenbeckstr. 1, 55131 Mainz, Germany
| | - Ulrike Ritz
- Department of Orthopaedics and Traumatology, Biomatics Group, University Medical Center of the Johannes Gutenberg University, Langenbeckstr. 1, 55131 Mainz, Germany
| |
Collapse
|