Indirect 3D Research Articles

Indirect three-dimensional printing: A method for fabricating polyurethane-urea based cardiac scaffolds.

Biomaterial scaffolds are a key part of cardiac tissue engineering therapies. The group has recently synthesized a novel polycaprolactone based polyurethane‐urea copolymer that showed improved mechanical properties compared with its previously published counterparts. The aim of this study was to explore whether indirect three‐dimensional (3D) printing could provide a means to fabricate this novel, biodegradable polymer into a scaffold suitable for cardiac tissue engineering. Indirect 3D printing was carried out through printing water dissolvable poly(vinyl alcohol) porogens in three different sizes based on a wood‐stack model, into which a polyurethane‐urea solution was pressure injected. The porogens were removed, leading to soft polyurethane‐urea scaffolds with regular tubular pores. The scaffolds were characterized for their compressive and tensile mechanical behavior; and their degradation was monitored for 12 months under simulated physiological conditions. Their compatibility with cardiac myocytes and performance in novel cardiac engineering‐related techniques, such as aggregate seeding and bi‐directional perfusion, was also assessed. The scaffolds were found to have mechanical properties similar to cardiac tissue, and good biocompatibility with cardiac myocytes. Furthermore, the incorporated cells preserved their phenotype with no signs of de‐differentiation. The constructs worked well in perfusion experiments, showing enhanced seeding efficiency. © 2016 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1912–1921, 2016.

LB-S&T-17 THE IMPACT OF MANGANESE SUPEROXIDE DISMUTASE GENE IN SMOOTH MUSCLE ON THE URETHRAL FUNCTION OF STRESS URINARY INCONTINENCE MICE MODEL

INTRODUCTION AND OBJECTIVES: Although various novel tissue engineered urethral scaffolds have been reported in the last decade, less reports are focused on the multi-scale structure of scaffold. Therefore, the structure of those scaffolds are quite different from the actual urethral tissue. In this study, we investigate the feasibility of constructing the 3D multi-scale modified bulbar urethral scaffold, which can be similar to the native urethral structure. METHODS: Five volunteers’ images about their bulbar urethra were obtained through the ultrasound. Those data were used to reform the 3D digital model of bulbar urethra. By using the indirect 3D printing technique, the mould of individual bulbar urethra was constructed. The silk fibroin solution was cast into this mould and freeze-dry procedure was performed, subsequently. After forming the macro porous scaffold, the Acetobacter xylinum was incubated into the scaffold to assemble the cellulose layer. The mechanical tests were perform in all scaffolds. The details of final scaffold were evaluated by the micro CT and scanning electron microscope. Meanwhile, the details of native bulbar urethral structure was compared with those in the constructed scaffold. RESULTS: All scaffold exhibited the ideal mechanical properties. The gross view of the constructed scaffolds was similar to the actual bulbar urethra. In the micro-scale, a typical bilayer structure could be noticed in the scaffold. The pore size of scaffold inner surface was 12.3 2.4mm, which is close to the native urethra (15.2 3.6mm). The pore size of scaffold sublayer and native urethra were 140 34mm and 146 30mm, respectively. In the nano-scale, no statistical difference of fiber diameter was found in the constructed scaffold and native urethra (22.3 6.3 nm vs 24.6 5.0 nm). CONCLUSIONS: Our study demonstrated the feasibility of constructing individual 3D urethral scaffold, which was similar to the structure of native bulbar urethra in multi-scale. Furthermore, the structure of this scaffold could be easily modified by controlling the production process according to the demanding of design. It provide a novel conception for constructing the tissue engineering urethral scaffold.

The pendular mechanism does not determine the optimal speed of loaded walking on gradients

The pendular mechanism does not act as a primary mechanism in uphill walking due to the monotonic behavior of the mechanical energies of the center of mass. Nevertheless, recent evidence shows that there is an important minimization of energy expenditure by the pendular mechanism during walking on uphill gradients. In this study, we analyzed the optimum speed (OPT) of loaded human walking and the pendulum-like determining variables (Recovery R, Instantaneous pendular re-conversion Rint, and Congruity percentage %Cong). Ten young men walked on a treadmill at five different speeds and at three different treadmill incline gradients (0, +7 and +15%), with and without a load carried in their backpacks. We used indirect calorimetry and 3D motion analysis, and all of the data were analyzed by computational algorithms. Rint increased at higher speeds and decreased with increasing gradient. R and %Cong decreased with increasing gradient and increased with speed, independent of load. Thus, energy conversion by the pendular mechanism during walking on a 15% gradient is supported, and although this mechanism can explain the maintenance of OPT at low walking speeds, the pendular mechanism does not fully explain the energy minimization at higher speeds.

Inter- and Intra-Operator Reliability of Facial and Dental Measurements Using 3D-Stereophotogrammetry.

The goal of this study was to assess the reproducibility of an innovative method for facial analysis with three-dimensional-stereophotogrammetry (3D-spg). Twelve subjects with no obvious malocclusion participated in this study. For each of them, four photographs were acquired using the LifeViz(TM) , an absolute calibration 3D-spg system. The facial reconstructions were analyzed with the DermaPix(TM) image management software. Two different operators recorded distances between landmarks and each operator repeated the measurements after one week. The intra- and inter-examiner reproducibilities were assessed using the Intraclass Correlation Coefficient (ICC). This study showed reproducible intra and inter-examiners results for facial measurements (ICC comprised between 0.732 and 0.976) except for measurements that involve the inner part of the dental corridor (ICC comprised between 0.598 and 0.914). The measurements recorded by 3D-LifeViz(TM) system are accurate and reliable for research and clinical use. Moreover, it is simple and inexpensive compared with other 3D methods (laser scanner, 3D Computed Tomography, and 3D Cone Beam CT). The inter- and intra-operator reliability of the LifeViz(TM) 3D-spg method was demonstrated. The LifeViz(TM) 3D-spg method might be a useful method to accomplish indirect 3D measurements that are relevant to dental and facial diagnosis. (J Esthet Restor Dent, 2016).

Fabrication of a highly ordered hierarchically designed porous nanocomposite via indirect 3D printing: Mechanical properties and in vitro cell responses

Abstract Design and development of biodegradable scaffolds with highly uniform and controlled internal structure that stimulate tissue regeneration are the focus of many studies. The aim of this work is to apply a modified three-dimensional (3D) printing process to fabricate polymer-matrix composites with controlled internal architecture. Computationally-designed plaster molds with various pore sizes in the range of 300–800 μm were prepared by employing 3D printing of a water-based binder. The molds were converted to e-polycaprolactone (PCL) and PCL/bioactive glass (BG) composite scaffolds by solvent casting and freeze drying methods. Optical and electron microscopy studies revealed that the pore structure was retained without shape distortion of the scaffolds. The wall structure of the pores was composed of a homogeneous fibril interconnected porous surface. The mechanical properties of the scaffolds were evaluated by uniaxial compression and nano-indentation tests. In vitro cell studies by MC3T3-E1 mouse preosteoblast cells showed that the prepared 3D scaffolds supported cell adhesion, tissue growth and cell differentiation. The effect of pore geometry and bioactive glass particles on the mechanical properties and tissue growth were evaluated. The results of mechanical examinations and in vitro cell responses determined the potential of the process for the fabrication of non-load bearing 3D scaffolds.

Near zero shrinkage porous Al2O3 prepared via 3D-printing and reaction bonding

Porous Al2O3 with high porosity (~45%), remarkable flexural strength (~70MPa), and low dimensional change (~1–2%), was produced by indirect 3D printing and reaction bonding. Coarse Al with good flowability was carried out printing green body. The green body was heat treated to get fully oxidized, volume expansion during oxidation simultaneously formed strong neck bonding, not only brought good strength, but also restricted shrinkage. Porous Al2O3 with architecture of macro pores designed by 3D printing and micro pores in the strut formed by packing of particles was obtained. The near zero shrinkage can facilitate precise design of product with complex shape.

First-principles calculations of electronic and optical properties of F, Mn-codoped cubic ZrO2

First-principles calculations based on DFT + U were performed on electronic and optical properties of F, Mn-codoped cubic ZrO2. The calculations show a half-metallic ferromagnetism behavior of the system. Both the direct 2p–3d interaction and the indirect 3d–2p–4d interaction can be expected to contribute to the long range magnetic coupling. By substitutional codoping of F and Mn, it can be found that the band gap is basically unchanged, and the obvious increase near the Fermi level together with the impurity bands at the bottom of upper valence band make the width of upper valence band obviously broaden. Meanwhile, F and Mn codoping induces obvious increase of refractive index, decrease of O 2s/2p-Zr 4d transitions intensities, and new steep absorption peaks at 2.45 eV, which can be used for photo absorption applications.

Pretreatment quality assurance of volumetric modulated arc therapy on patient CT scan using indirect 3D dosimetry system

Purpose: Aim of this study is to clinically implement the COMPASS 3D dosimetry system for pretreatment quality assurance of volumetric modulated arc therapy (VMAT-RapidArc) treatment plans. Methods: For this study, 10 head and neck (H&N) and 10 pelvis VMAT plans dose response from Linac was measured using COMPASS system along with MatriXX Evolution and 3D dose was reconstructed in the patient computed tomography (CT) scan. Dose volume histograms and 3D gamma were used to evaluate the difference between the measured and calculated values. In order to validate the COMPASS system, dose response for open fields were acquired for both homogeneous and inhomogeneous phantoms. Results: The average dose difference between Eclipse treatment planning system (TPS) calculated and COMPASS measured (homogenous medium) in normalization region, inner region, penumbra region and buildup region was less than ±2%. In inhomogeneous phantom, there was a maximum difference of -3.17% in lung, whereas the difference other densities was within ±2%. The systematic increase in the average 3D gamma between the TPS calculated and COMPASS measured for VMAT plans with known dose errors and multi-leaf collimator (MLC) offset errors shows that COMPASS system was sensitive enough to find clinical significant errors. The 3D dose parameters (D95, D1, and average dose) of all H&N and pelvis patients were well within the clinically acceptable tolerance level of ±5%. The average 3D gammas for planning target volumes (PTV) and organ at risks (OAR) of the patients were less than 0.6. Conclusion: The results from this study show that COMPASS along with MatriXX Evolution can be effectively used for pretreatment verification of VMAT plans in the patient anatomy.

Wavelet-Based 3D Reconstruction of Microcalcification Clusters from Two Mammographic Views: New Evidence That Fractal Tumors Are Malignant and Euclidean Tumors Are Benign

The 2D Wavelet-Transform Modulus Maxima (WTMM) method was used to detect microcalcifications (MC) in human breast tissue seen in mammograms and to characterize the fractal geometry of benign and malignant MC clusters. This was done in the context of a preliminary analysis of a small dataset, via a novel way to partition the wavelet-transform space-scale skeleton. For the first time, the estimated 3D fractal structure of a breast lesion was inferred by pairing the information from two separate 2D projected mammographic views of the same breast, i.e. the cranial-caudal (CC) and mediolateral-oblique (MLO) views. As a novelty, we define the “CC-MLO fractal dimension plot”, where a “fractal zone” and “Euclidean zones” (non-fractal) are defined. 118 images (59 cases, 25 malignant and 34 benign) obtained from a digital databank of mammograms with known radiologist diagnostics were analyzed to determine which cases would be plotted in the fractal zone and which cases would fall in the Euclidean zones. 92% of malignant breast lesions studied (23 out of 25 cases) were in the fractal zone while 88% of the benign lesions were in the Euclidean zones (30 out of 34 cases). Furthermore, a Bayesian statistical analysis shows that, with 95% credibility, the probability that fractal breast lesions are malignant is between 74% and 98%. Alternatively, with 95% credibility, the probability that Euclidean breast lesions are benign is between 76% and 96%. These results support the notion that the fractal structure of malignant tumors is more likely to be associated with an invasive behavior into the surrounding tissue compared to the less invasive, Euclidean structure of benign tumors. Finally, based on indirect 3D reconstructions from the 2D views, we conjecture that all breast tumors considered in this study, benign and malignant, fractal or Euclidean, restrict their growth to 2-dimensional manifolds within the breast tissue.

LAS glass–ceramic scaffolds by three-dimensional printing

Abstract Highly porous (>60% open porosity) glass–ceramic scaffolds with remarkable mechanical properties (compression strength of ∼15 MPa) were produced by indirect 3D printing. Precursor glass powders were printed into 3D ordered structures and then heat treated to sinter and develop crystalline phases. The final glass–ceramic contained a β-spodumene solid solution together with a secondary phase of lithium disilicate. The precision of the printed geometry and the density of the struts in the scaffold depended on several processing parameters (e.g. powder size and flowability, layer thickness) and were improved by increasing the binder saturation and drying time. Two types of powders with different particle size distribution (PSD) and flowability were used. Powders with a larger PSD, could be processed within a wider range of printing parameters due to their good flowability; however, the printing precision and the struts density were lower compared to the scaffolds printed using the powder in a smaller average PSD.

Femtosecond laser micromachining of fused silica molds

The use of low-energy femtosecond laser beam combined with chemical etching has been proven to be an efficient method to fabricate three-dimensional structures in fused silica. For high-volume application, this technology--like other serial processes--suffers from a moderate production rate. Here, we show that femtosecond laser can also be employed to fabricate silica molds and other patterned surfaces, including surfaces with high aspect ratio features (> 10). Through appropriate tailoring of silica's surface property and subsequent creation of, for instance, simple elastomeric molding, new opportunities for the indirect 3D, multi-scale spatial characterization of deep laser-fabricated microstructures come along. We demonstrate that those moldings are characterized by a high fidelity (down to the nanometer scale) to the silica mold. These results further advance the applicability of femtosecond laser processing to glass.

3D printing of Al2O3/Cu–O interpenetrating phase composite

Porous alumina preforms were fabricated by indirect 3D printing using a blend of alumina and dextrin as a precursor material. The bimodal granulate powder distribution with a bed density of 0.8 g/cm3 was increased to 1.4 g/cm3 by overprinting. The porosity of the sintered bodies was controlled by adjusting the printing liquid to precursor powder ratio in the range of 33–44 vol%. The green bodies exhibited bending strengths between 4 and 55 MPa. An isotropic linear shrinkage of ~17% was obtained due to dextrin decomposition and Al2O3 sintering at 1600 °C. Post-pressureless infiltration of the sintered preforms with a Cu–O alloy at 1300 °C for 1.5 h led to the formation of a dense Al2O3/Cu–O interpenetrating phase composite (IPC). X-ray analysis of the fabricated composites showed the presence of α-Al2O3, Cu and Cu2O. CuAl2O4 spinel was not observed at the grain boundaries during HRTEM examination. The Al2O3/Cu–O interpenetrating phase composite revealed a fracture toughness of 5.5 ± 0.3 MPam1/2 and a bending strength of 236 ± 32 MPa. In order to demonstrate technological capability of this approach, complex-shaped bodies were fabricated.

Effect of scaffold architecture and pore size on smooth muscle cell growth

Tissue engineering has the potential to replace damaged tissues and organs. Diffusion limitation of cell growth in three-dimensional (3D) scaffolds is a significant constraint in most tissue engineering applications. This study describes a scaffold architecture that improves mass transfer. Scaffolds with three different geometries of villi architecture (0.5, 1, 0.5; 0.5, 1, 1; 1, 1, 1 mm; villus diameter, height, intervillus spacing, respectively) were fabricated by indirect 3D printing technique. The ability of these scaffolds to support smooth muscle cell growth was investigated in vitro. Smooth muscle cells attached to the scaffolds uniformly after 1 day of culture, and the cell density in the scaffold with small villi feature (0.5 mm) was significantly higher as compared to that for the scaffold with large villi features (1 mm) after 14 days of culture. To evaluate the effect of scaffold pore size on cell growth, scaffolds with three different pore size ranges (50-100, 100-150, and 150-200 microm) were fabricated by the solvent casting and particulate leaching technique. Scaffold pore size did not significantly affect cell growth after 14 days of culture. Optimization in the architectural design of scaffolds provides an alternative method to improve diffusion limitation in the 3D constructs.

Novel 3D collagen scaffolds fabricated by indirect printing technique for tissue engineering

This article reports the mechanical properties and in vitro evaluation of a collagen scaffold fabricated using an indirect 3D printing technique. Collagen scaffolds, featuring predefined internal channels and capillary networks, were manufactured using phase change printing. It was observed that the collagen scaffolds featured internal channels and a hierarchical structure that varied over length scales of 10-400 microm. In vitro evaluation using hMSCs demonstrated that the resultant collagen based scaffolds have the ability to support hMSC cell attachment and proliferation; cells can migrate and survive deep within the structure of the scaffold. The cell numbers increased 2.4 times over 28 days in culture for the lysine treated scaffolds. The cells were spread along the collagen fibers to form a 3D structure and extracellular matrix was detected on the surface of the scaffolds after 4 weeks in culture. The crosslinking treatment enhanced the biostability and dynamic properties of the collagen scaffolds significantly.

Coupled physical and digital cadaver dissection followed by a visual test protocol provides insights into the nature of anatomical knowledge and its evaluation

This research effort compared and contrasted two conceptually different methods for the exploration of human anatomy in the first-year dissection laboratory by accomplished students: "physical" dissection using an embalmed cadaver and "digital" dissection using three-dimensional volume modeling of whole-body CT and MRI image sets acquired using the same cadaver. The goal was to understand the relative contributions each method makes toward student acquisition of intuitive sense of practical anatomical knowledge gained during "hands-on" structural exploration tasks. The main instruments for measuring anatomical knowledge under this conceptual model were questions generated using a classification system designed to assess both visual presentation manner and the corresponding response information required. Students were randomly divided into groups based on exploration method (physical or digital dissection) and then anatomical region. The physical dissectors proceeded with their direct methods, whereas the digital dissectors generated and manipulated indirect 3D digital models. After 6 weeks, corresponding student anatomical assignment teams compared their results using photography and animated digital visualizations. Finally, to see whether each method provided unique advantages, a visual test protocol of new visualizations based on the classification schema was administered. Results indicated that all students, regardless of gender, dissection method, and anatomical region dissected performed significantly better on questions presented as rotating models requiring spatial ordering or viewpoint determination responses in contrast to requests for specific lexical feature identifications. Additional results provided evidence of trends showing significant differences in gender and dissection method scores. These trends will be explored with further trials with larger populations.

Boundary Element Analysis of Three-Dimensional Exponentially Graded Isotropic Elastic Solids

A numerical implementation of the Somigliana identity in displacements for the solution of 3D elastic problems in exponentially graded isotropic solids is presented. An expression for the fundamental solution in displacements Uj`, was deduced by Martin et al. (Proc. R. Soc. Lond. A, 458, pp. 1931–1947, 2002). This expression was recently corrected and implemented in a Galerkin indirect 3D BEM code by Criado et al. (Int. J. for Numerical Methods in Engineering, 2006). Starting from this expression of Uj`, a new expression for the fundamental solution in tractions Tj` has been deduced in the present work. These quite complex expressions of the integral kernels Uj` and Tj` have been implemented in a collocational direct 3D BEM code. The numerical results obtained for 3D problems with known analytic solutions verify that the new expression for Tj` is correct. Excellent accuracy is obtained with very coarse boundary element meshes, even for a relatively high grading of elastic properties considered.

Quantitative structure–activity relationships for small non-peptide antagonists of CXCR2: Indirect 3D approach using the frontal polygon method

The chemokine receptor, CXCR2, plays an important role in recruiting granulocytes to sites of inflammation and has been proposed as an important therapeutic target. A number of CXCR2 antagonists have been synthesized and evaluated; however, quantitative structure–activity relationship (QSAR) models have not been developed for these molecules. Most CXCR2 antagonists can be grouped into four related categories: N, N′-diphenylureas, nicotinamide N-oxides, quinoxalines, and triazolethiols. Based on these categories, we developed a QSAR model for 59 nonpeptide antagonists of CXCR2 using a partial 3D comparison of the antagonists with local fingerprints obtained from rigid and flexible fragments of the molecules. Each compound was represented by calculated structural descriptors that encoded atomic charge, molar refraction, hydrophobicity, and geometric features. We obtained good conventional R 2 coefficients, high leave-one-out cross-validated values for the whole dataset ( R cv 2 = 0.785 ) , as well as for the dataset divided into subsets of triazolethiol derivatives ( R cv 2 = 0.821 ) and joint subset of N′-diphenylureas, nicotinamide N-oxides, N, N ′-diphenylureas, and quinoxaline derivatives and quinoxalines derivatives ( R cv 2 = 0.766 ) , indicating a good predictive ability and robustness of the model. Additionally, charge distribution was found to be a significant contributor in modeling whole dataset. Using our model, structural fragments (submolecules) responsible for the antagonist activity were also identified. These data suggest the QSAR models developed here may be useful in guiding the design of CXCR2 antagonists from molecular fragments.

Effect of Si content on magnetic properties and intersublattice exchange interactions in GdFe 11− xSi xTi compounds

Induction melted GdFe 11− x Si x Ti alloys ( x⩽2) with ThMn 12-type structure have been investigated. The decrease of Curie temperature, magnetic moment and anisotropy constant are ruled by Si 3p electron transfer into Fe 3d band. The increase of the exchange interaction parameter between Gd and Fe sublattice shows that indirect 3d–4f interaction is enhanced.

Electronic structure of Si-skeleton materials.

The electronic structures of Si-skeleton chainlike [one-dimensional (1D)] and planar [two-dimensional (2D)] materials have been calculated by the first-principles local-density-functional method. 1D Si-skeleton material (chain polysilane) has a directly-allowed-type band structure with a band gap of about 4 eV. Interchain interaction disappears, independently of the chain configuration, if each chain is located over 8 A\r{} from other chains. Therefore, the electronic structure of some polysilane-chain aggregations can be discussed in terms of the result for the corresponding isolated polysilane chain. 2D material (planar polysilane) has an indirect band gap of 2.48 eV as well as a direct band gap of 2.68 eV. This structure is an intermediary between direct (1D) and indirect (3D). A characteristic single, double, and treble degeneracy is found at the highest occupied valence-band state, depending on the structure dimension of 1D, 2D, or 3D Si skeleton, respectively.