Organ printing as an information technology

Funding Information: This work has been sponsored by the São Paulo Research Foundation (FAPESP), The Brazilian Institute of Biofabrication (INCT-BIOFABRIS) and National Council for Scientific and Technological Development (CNPq). Publisher Copyright: © 2015 Published by Elsevier Ltd.Organ printing is defined as a layer by layer additive robotic computer-aided biofabrication of functional 3D organ constructs with using self-assembling tissue spheroids according to digital model. Information technology and computer-aided design softwares are instrumental in the transformation of virtual 3D bioimaging information about human tissue and organs into living biological reality during 3D bioprinting. Information technology enables design blueprints for bioprinting of human organs as well as predictive computer simulation both printing and post-printing processes. 3D bioprinting is now considered as an emerging information technology and the effective application of existing information technology tools and development of new technological platforms such as human tissue and organ informatics, design automation, virtual human organs, virtual organ biofabrication line, mathematical modeling and predictive computer simulations of bioprinted tissue fusion and maturation is an important technological imperative for advancing organ bioprinting.publishersversionPeer reviewe

Biomechanical properties of human dilated ascending aorta

Publisher Copyright: © 2019 Ivars Brečs et al., published by Sciendo 2019. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.Aneurysms of ascending aorta are dilatation of the first part of the human aorta. They commonly show no clinical symptoms. This condition increases the risk of aorta dissection, which is a life-threatening condition. In this study we attempted to elucidate the changes in the biomechanical properties that occur in the dilated human ascending aorta. Fourteen specimens of ascending aorta wall were mechanically tested under a uniaxial tensile test. Two specimens from each ascending aorta anterior region were cut in longitudinal and circumferential directions. The samples were stretched until rupture of the sample occurred. The obtained experimental data were processed to determine maximal stress, maximal strain and the tangential modulus of elasticity in the linear part of the stress-strain curve. The obtained results showed a remarkable anisotropy of the ascending aorta tissue. We found higher strength of the tissue in the circumferential direction than in the longitudinal direction. There were no statistically significant differences between the strains of the samples. Tangential modulus of elasticity of the aortic samples in the longitudinal direction was significantly lower than the elastic modulus of the samples in the circumferential direction. The tissue in the circumferential direction is stronger and stiffer than in the longitudinal direction.Peer reviewe

General influence of biphasic calcium phosphate on osteoporotic bone density

Funding Information: The study was supported by the National Research Programme No. 2014.10-4/VPP-3/21 “Multifunctional Components and composites, photonics and nanotechnology”. Project No. 4 “Nanocomponents and nanotechnologies for medical applications”. Publisher Copyright: © 2019 Vladislavs Ananjevs et al., published by Sciendo 2019. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.Bone density of the femur body of rabbit was determined in vivo. Experimental osteoporosis was induced by ovariectomy and subsequent injections of methylprednisolone. In the greater trochanter region of right femur, defects were created and filled with granules of hydroxyapatite and tricalcium phosphate (HAP/TCP 70/30) or HAP/TCP 70/30 together with 5% strontium. After three months, the animals were euthanized. The bone mass density of the right and left body of femur was measured by cone beam computed tomography (CT) scan. The results of the study showed that the right femur of the rabbit, where biomaterials had been implanted, and the left femur, where no biomaterial implantation occurred, became denser after filling the defect with HAP/TCP 70/30 ceramic granules or 5% Sr modified HAP/TCP ceramic granules. There was no difference between operated and non-operated legs and HAP/TCP and HAP/TCP with 5% strontium groups.publishersversionPeer reviewe

Comparison of biomechanical and structural properties between human aortic and pulmonary valve

Funding Information: This study was supported by a grant from the Latvian Council of Science.Objective: Pulmonary valve autografts have been reported as clinically effective for replacement of diseased aortic valve (Ross procedure). Published data about pulmonary valve mechanical and structural suitability as a long-term substitute for aortic valve are limited. The aim of this study was to compare aortic and pulmonary valve properties. Methods: Experimental studies of biomechanical properties and structure of aortic and pulmonary valves were carried out on pathologically unchanged human heart valves, collected from 11 cadaveric hearts. Biomechanical properties of 84 specimens (all valve elements: cusps, fibrous ring, commissures, sinotubular junction, sinuses) were investigated using uniaxial tensile tests. Ultrastructure was studied using transmission and scanning electron microscopy. Results: Ultimate stress in circumferential direction for pulmonary valve cusps is higher than for aortic valve (2.78±1.05 and 1.74±0.29 MPa, respectively). Ultimate stress in radial direction for pulmonary and aortic cusps is practically the same (0.29±0.06 and 0.32±0.04 MPa, respectively). In ultrastructural study, different layout and density in each construction element are determined. The aortic and pulmonary valves have common ultrastructural properties. Conclusions: Mechanical differences between aortic and pulmonary valve are minimal. Ultrastructural studies show that the aortic and pulmonary valves have similar structural elements and architecture. This investigation suggests that the pulmonary valve can be considered mechanically and structurally suitable for use as an aortic valve replacement.Peer reviewe

Calcium Phosphate Bioceramic Material Local Influence on the Bone Biomechanical Properties at Rabbits with Experimental Osteoporosis

Biomechanical characteristicsof the rabbit cartilagecomponentfrom the femurwereinvestigated.The controlosteoporosishad beenactivatedby ovariectomy alongside theinjections of methylprednisolone. During the experiment defects in the femur’sgreater trochanter zonewas created andafterwardsfilled withthefragmentsof a hydroxyapatite as well astricalcium phosphate(HAP/TCP 70/30) or HAP/TCP 70/30mixedwith five percentstrontium. Threemonths lateranimals were euthanazed, squared samples werecut out from the femur’sbody andlatertested on a bend. The results ofthe research revealedthat the femurs becomemorestringentafter filling offdefects in the greater trochanter zonewith HAP/TCP 70/30or HAP/TCP 70/30mixed with fivepercentstrontium. The ultimate painfor the cartilagecomponentin the controlgroupswas less, than in thetest group.The flexure modulus of flexibilityof a cartilagecomponentin the test groupwas statistically reliable less, than the value of the flexure modulus of flexibilityof the cartilagecomponentin the controlgroups. Therefore, local usage ofcalcium –phosphatic bioceramic componentoverthe greater trochanter partincreasesbiomechanical characteristicsof the cartilagecomponentin the femurof animals.Peer reviewe

Nanotechnological strategies for biofabrication of human organs

Nanotechnology is a rapidly emerging technology dealing with so-called nanomaterials which at least in one dimension have size smaller than 100nm. One of the most potentially promising applications of nanotechnology is in the area of tissue engineering, including biofabrication of 3D human tissues and organs. This paper focused on demonstrating how nanomaterials with nanolevel size can contribute to development of 3D human tissues and organs which have macrolevel organization. Specific nanomaterials such as nanofibers and nanoparticles are discussed in the context of their application for biofabricating 3D human tissues and organs. Several examples of novel tissue and organ biofabrication technologies based on using novel nanomaterials are presented and their recent limitations are analyzed. A robotic device for fabrication of compliant composite electrospun vascular graft is described. The concept of self-assembling magnetic tissue spheroids as an intermediate structure between nano- and macrolevel organization and building blocks for biofabrication of complex 3D human tissues and organs is introduced. The design of in vivo robotic bioprinter based on this concept and magnetic levitation of tissue spheroids labeled with magnetic nanoparticles is presented. The challenges and future prospects of applying nanomaterials and nanotechnological strategies in organ biofabrication are outlined.publishersversionPeer reviewe

Design, Fabrication, and Application of Mini-Scaffolds for Cell Component in Tissue Engineering

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The fusion of tissue spheroids attached to pre-stretched electrospun polyurethane scaffolds

Publisher Copyright: © 2014, © The Author(s) 2014. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.Effective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (<2 µm) porous electrospun meshes and self-assembling (capable of tissue fusion) tissue spheroids as building blocks. Pre-stretched electrospun meshes remained taut in cell culture and were able to support tissue spheroids with minimal deformation. We hypothesize that elastic electrospun scaffolds could be used as temporal support templates for rapid self-assembly of cell spheroids into higher order tissue structures, such as engineered vascular tissue. The aim of this study was to investigate how the attachment of tissue spheroids to pre-stretched polyurethane scaffolds may interfere with the tissue fusion process. Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs. Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number. In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes. Our data demonstrate that tissue spheroids attached to thin stretched elastic electrospun scaffolds have an interrupted tissue fusion process. The resulting tissue-engineered construct phenotype is a direct outcome of the delicate balance of the competing physical forces operating during the tissue fusion process at the interface of the pre-stretched elastic scaffold and the attached tissue spheroids. We have shown that with appropriate treatments, this process can be modulated, and thus, a thin pre-stretched elastic polyurethane electrospun scaffold could serve as a supporting template for rapid biofabrication of thick tissue-engineered constructs without the need for cell invasion.publishersversionPeer reviewe

Tensiometric estimation of material properties of tissue spheroids

Tissue spheroids have been proposed to use as building blocks in biofabrication and as bioinks in 3D bioprinting technologies. Tissue fusion is an ubiqious phenomenon during embryonic development. Biomimetic tissue spheroid fusion is a fundamental constructional principle of emerging organ printing technology because closely placed tissue spheroids could fuse into tissue and organ-like constructs in fusion permissive bioprintable hydrogel. From physical point of view tissue spheroids could be considered as a visco-elastic-plastic soft matter or complex fluid. We hypothesize that quantitative estimation of material properties of tissue spheroids using tensiometry could predict their tissue spreading and tissue fusion behavior as well as provide a powerful insight about possible speed of post-printed tissue and organ-like constructs compaction and maturation. Tissue spheroids from human fibroblasts, ovine and human chondrocytes and immortalised human keratinocytes have been biofabricated using non-adhesive cell culture plates (Corning, USA). For estimation of material properties of tissue spheroids commercial tensiometer Microsquisher have been emploied (CellScale, Toronto, Canada). Modulus of elasticity of tissue spheroids have been calculated based on peformed tissue compression tests. In order to identify structural determinants of material properties of tissue spheroids standard perturbants of cytoskeleton such as Cytochalasin D (Sigma, USA) for disruption of microfilaments and Nocodazole (Sigma, USA) for disruption of microtubules have been used. Viability of tissue spheroids have been also estimated and their morphology have been analysed using light microscopy, histochemistry, immunohistochemistry, semithin sections stained wih toluidine blue and transmission and scanning electron microscopy. Kinetics of tissue spheroids spreading on electrospun polyurethane matrices have been analysed. Kinetics of two closely placed tissue spheroids fusion have been analysed in hanging drop. Additionally toxic effect of water solution of paramagnetic gadolinium salt (Omniscan®, GE Health Care, USA) on material properties of tissue spheroids have been investigated. It have been demonstrated that material properties of tissue spheroids biofabricated from different cell types have different modulus of elasticity. Even tissue spheroids biofabricated the same cell types but from different species have different material properties. Incubation with Cytochlasin D dramatically reduces estimated material properties of tissue spheroids. Incubation with Nocodazole does not significantly change material properties of tissue spheroids. Material properties of tissue spheroids from chondrocytes (chondrospheres) correlates very well with increasing deposition and accumulation of extracellular matrix (confirmed by expression of collagen type II and glycosoaminoglycans). The incubation with toxic concentration of gadolinium solution dramatically reduces material properties of chondrospheres. There is no any significant correlation between material properties of tissue spheriods and their spreading kinetics. However, there is a certain correction between material properties of tissue spheroids and their tissue fusion kinetics. Our data demonstrate that beside already well established role of cell adhesion receptors such as cadherin and integrins in the realisation of cell cohesion inside tissue spheroids the structural determinants of material properties of tissue spheroids also include components of cytoskeleton such as actin micofilaments and accumulated extracellular matrix. It is possible to predict post-printing tissue fusion behaviour of tissue spheroids based on preliminary estimation of their material properties. Finally, it have been also shown that material properties of tissue spheroids correlate with their viability. Thus, tensiometry is a valuable method for systematic characterization of material properties of tissue spheroids and for prediction of tissue spheroids post-printed tissue fusion behaviour

Commercial articulated collaborative in situ 3D bioprinter for skin wound healing

In situ bioprinting is one of the most clinically relevant techniques in the emerging bioprinting technology because it could be performed directly on the human body in the operating room and it does not require bioreactors for post-printing tissue maturation. However, commercial in situ bioprinters are still not available on the market. In this study, we demonstrated the benefit of the originally developed first commercial articulated collaborative in situ bioprinter for the treatment of full-thickness wounds in rat and porcine models. We used an articulated and collaborative robotic arm from company KUKA and developed original printhead and correspondence software enabling in situ bioprinting on curve and moving surfaces. The results of in vitro and in vivo experiments show that in situ bioprinting of bioink induces a strong hydrogel adhesion and enables printing on curved surfaces of wet tissues with a high level of fidelity. The in situ bioprinter was convenient to use in the operating room. Additional in vitro experiments (in vitro collagen contraction assay and in vitro 3D angiogenesis assay) and histological analyses demonstrated that in situ bioprinting improves the quality of wound healing in rat and porcine skin wounds. The absence of interference with the normal process of wound healing and even certain improvement in the dynamics of this process strongly suggests that in situ bioprinting could be used as a novel therapeutic modality in wound healing.publishersversionPeer reviewe