Biofabrication : reappraising the definition of an evolving field

Biofabrication is an evolving research field that has recently received significant attention. In particular, the adoption of Biofabrication concepts within the field of Tissue Engineering and Regenerative Medicine has grown tremendously, and has been accompanied by a growing inconsistency in terminology. This article aims at clarifying the position of Biofabrication as a research field with a special focus on its relation to and application for Tissue Engineering and Regenerative Medicine. Within this context, we propose a refined working definition of Biofabrication, including Bioprinting and Bioassembly as complementary strategies within Biofabrication

A Multifunctional Nanocomposite Hydrogel for Endoscopic Tracking and Manipulation

Herein, the fabrication of multi‐responsive and hierarchically organized nanomaterial using core‐shell SrF2 upconverting nanoparticles, doped with Yb3+, Tm3+, Nd3+ incorporated into gelatin methacryloyl matrix, is reported. Upon 800 nm excitation, deep monitoring of 3D‐printed constructs is demonstrated. Addition of magnetic self‐assembly of iron oxide nanoparticles within the hydrogel provides anisotropic structuration from the nano‐ to the macro‐scale and magnetic responsiveness permitting remote manipulation. The present study provides a new strategy for the fabrication of a novel highly organized multi‐responsive material using additive manufacturing, which can have important implications in biomedicine

A construção ortodoxa dos números : dos números naturais aos complexos

In this work, we investigated the construction of natural, integer, rational, real, complex, quaternion and Octonion numbers. More precisely, the set of real numbers was achieved by applying two methods: Dedekind Cuts and Equivalence Classes of Cauchy Sequences. Our study is only based on using Peano Axioms, which are directly related to the natural numbers, in order to get the basic properties satis ed by these numbers. In addition, we carefully proved the elementary results involving real numbers. This process in question was developed constructively throughout of the concepts of the integer and rational numbers. Next, we show that it is possible to establish the existence of complex numbers along with their more usual arithmetic properties. Finally, we nish each chapter of our work showing some possible applications in each set worked.No presente trabalhos, investigamos, cuidadosamente, a construção do números Naturais, inteiros, Racionais, Reais e Complexos. Sendo que, o conjunto dos números reais foi obtido através dos conhecidos métodos: Cortes de Dedekind e Classes de Equivalência por sequência de Cauchy. O estudo consistiu em utilizar os famosos Axiomas de Peano, ps quais estão relacionados aos números naturais, em ordem a obter as em conhecidas propriedades elementares, satisfeitas para todos esses números. E, a partir deste conhecimento, encontramos rigorosamente as provas dos resultados básicos envolvendo os números reais. Este processo em questão, foi desenvolvida de maneira construtiva através dos números inteiros e racionais. Em seguida, mostramos que é possível estabelecer a existência de números complexos, juntamente com suas propriedades aritméticas mais usuais. Por fim, terminamos cada capítulo do nosso trabalho, mostrando algumas possíveis aplicações em cada conjunto trabalhado

Tissue-specific melt electrowritten polymeric scaffolds for coordinated regeneration of soft and hard periodontal tissues

Periodontitis is a chronic inflammatory condition that often causes serious damage to tooth-supporting tissues. The limited successful outcomes of clinically available approaches underscore the need for therapeutics that cannot only provide structural guidance to cells but can also modulate the local immune response. Here, three-dimensional melt electrowritten ( i.e., poly(ε-caprolactone)) scaffolds with tissue-specific attributes were engineered to guide differentiation of human-derived periodontal ligament stem cells (hPDLSCs) and mediate macrophage polarization. The investigated tissue-specific scaffold attributes comprised fiber morphology (aligned vs. random) and highly-ordered architectures with distinct strand spacings (small 250 μm and large 500 μm). Macrophages exhibited an elongated morphology in aligned and highly-ordered scaffolds, while maintaining their round-shape on randomly-oriented fibrous scaffolds. Expressions of periostin and IL-10 were more pronounced on the aligned and highly-ordered scaffolds. While hPDLSCs on the scaffolds with 500 μm strand spacing show higher expression of osteogenic marker (Runx2) over 21 days, cells on randomly-oriented fibrous scaffolds showed upregulation of M1 markers. In an orthotopic mandibular fenestration defect model, findings revealed that the tissue-specific scaffolds ( i.e., aligned fibers for periodontal ligament and highly-ordered 500 μm strand spacing fluorinated calcium phosphate [F/CaP]-coated fibers for bone) could enhance the mimicking of regeneration of natural periodontal tissues

Fixation of Hydrogel Constructs for Cartilage Repair in the Equine Model: A Challenging Issue

OBJECTIVE: To report on the experiences with the use of commercial and autologous fibrin glue (AFG) and of an alternative method based on a 3D-printed polycaprolactone (PCL) anchor for the fixation of hydrogel-based scaffolds in an equine model for cartilage repair. METHODS: In a first study, three different hydrogel-based materials were orthotopically implanted in nine horses for 1-4 weeks in 6 mm diameter full-thickness cartilage defects in the medial femoral trochlear ridge and fixated with commercially available fibrin glue (CFG). One defect was filled with CFG only as a control. In a second study, CFG and AFG were compared in an ectopic equine model. The third study compared the efficacy of AFG and a 3D-printed PCL-based osteal anchor for fixation of PCL-reinforced hydrogels in three horses for 2 weeks, with a 4-week follow-up to evaluate integration of bone with the PCL anchor. Short-term scaffold integration and cell infiltration were evaluated by microcomputed tomography and histology as outcome parameters. RESULTS: The first study showed signs of subchondral bone resorption in all defects, including the controls filled with CFG only, with significant infiltration of neutrophils. Ectopically, CFG induced clear inflammation with strong neutrophil accumulation; AFG was less reactive, showing fibroblast infiltration only. In the third study the fixation potential for PCL-reinforced hydrogels of AFG was inferior to the PCL anchor. PCL reinforcement had disappeared from two defects and showed signs of dislodging in the remaining four. All six constructs fixated with the PCL anchor were still in place after 2 weeks. At 4 weeks, the PCL anchor showed good integration and signs of new bone formation. CONCLUSIONS: The use of AFG should be preferred to xenogeneic products in the horse, but AFG is subject to individual variations and laborious to make. The PCL anchor provides the best fixation; however, this technique involves the whole osteochondral unit, which entails a different conceptual approach to cartilage repair

Clinical effects of two doses of butorphanol with detomidine for intravenous premedication of healthy warmblood horses

Objective: To compare the effects of two different doses of butorphanol combined with detomidine administered intravenously (IV) on quality of sedation, degree of ataxia and anaesthetic induction in horses. Study design: Randomized, blinded, clinical study. Animals: A total of 40 client-owned healthy warmblood horses scheduled for elective surgery under general anaesthesia. Methods: Horses were randomly allocated to be administered 8 μg kg–1 detomidine IV plus either 20 or 50 μg kg–1 butorphanol IV, with the principal investigator blinded to group allocation. Head height was measured before drug injection and 2 minutes thereafter. Data were compared using unpaired t test. Horses were filmed and scored using Simple Descriptive Scales for sedation (2 and 15 minutes after IV injection), ataxia (at walk, immediately after the 2 minute time point) and quality of swing-door induction following diazepam and ketamine administration. Data are shown as median (and range where appropriate). Scores were compared using chi-square tests (p <0.05). Results: There were 14 and 17 horses in high-dose (HD) and low-dose (LD) groups respectively. Data from nine horses were excluded. Mean head height reduction did not differ between groups (p = 0.86), nor did sedation scores at 2 minutes (median = 3 in both groups; p = 0.09) or 15 minutes (median = 2 in both groups; p = 0.63). There was no significant difference in the requirement for additional detomidine (p = 0.73) or in induction quality between groups (p = 0.99), but initial ataxia was significantly greater in the HD group 2 (1–3) versus 2.5 (1–3) in the LD group (p = 0.017). Conclusions and clinical relevance: In healthy warmblood horses, simultaneous administration of 50 rather than 20 μg kg–1 butorphanol with 8 μg kg–1 detomidine does not provide greater sedation or affect induction, but it causes more pronounced ataxia shortly after IV injection

Converging biofabrication and organoid technologies: the next frontier in hepatic and intestinal tissue engineering?

Adult tissue stem cells can form self-organizing 3D organoids in vitro. Organoids resemble small units of their organ of origin and have great potential for tissue engineering, as well as models of disease. However, current culture technology limits the size, architecture and complexity of organoids. Here, we review the establishment of intestinal and hepatic organoids and discuss how the convergence of organoids and biofabrication technologies can help overcome current limitations, and thereby further advance the translational application of organoids in tissue engineering and regenerative medicine

Surgical osteochondral defect repair in the horse—a matter of form or function?

Focal cartilaginous and osteochondral lesions can have traumatic or chondropathic degenerative origin. The fibrocartilaginous repair tissue that forms naturally, eventually undergoes fibrillation and degeneration leading to further disruption of joint homeostasis. Both types of lesion will therefore eventually lead to activity‐related pain, swelling and decreased mobility and will frequently progress to osteoarthritis. Most attempts at realising cartilage regeneration have so far resulted in cartilage repair (and not regeneration). The aim of this article was to review experimental research on surgical cartilage restoration techniques performed so far in equine models. Currently available surgical options for treatment of osteochondral lesions in the horse are summarised. The experimental validity of equine experimental models is addressed and finally possible avenues for further research are discussed

Kinematics

In three-dimensional continuum mechanics, the integral-gradient theorem, which is the basis of Green's transformation, often called “the divergence theorem,” is a tool of central importance. All the shapes of bodies should be such as to make the integral-gradient theorem apply whenever the fields integrated are smooth to the degrees ordinarily assumed. The first statement in the theorem makes the sets of finite perimeter a Boolean algebra with respect to intersection and union. This chapter discusses a theorem that relates sets of finite perimeter directly to the integral-gradient theorem. The chapter presents a local analysis of the equilibrium and motion of continuous media. © 1977, Academic Press, Inc