André Luiz Jardini

Poly-lactic acid synthesis for application in biomedical devices — A review

Bioabsorbable polymers are considered a suitable alternative to the improvement and development of numerous applications in medicine. Poly-lactic acid (PLA,) is one of the most promising biopolymers due to the fact that the monomers may produced from non toxic renewable feedstock as well as is naturally occurring organic acid. Lactic acid can be made by fermentation of sugars obtained from renewable resources as such sugarcane. Therefore, PLA is an eco-friendly product with better features for use in the human body (nontoxicity). Lactic acid polymers can be synthesized by different processes so as to obtain products with an ample variety of chemical and mechanical properties. Due to their excellent biocompatibility and mechanical properties, PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues. In order to maximize the benefits of its use, it is necessary to understand the relationship between PLA material properties, the manufacturing process and the final product with desired characteristics. In this paper, the lactic acid production by fermentation and the polymer synthesis such biomaterial are reviewed. The paper intends to contribute to the critical knowledge and development of suitable use of PLA for biomedical applications.

Cranial reconstruction: 3D biomodel and custom-built implant created using additive manufacturing.

Additive manufacturing (AM) technology from engineering has helped to achieve several advances in the medical field, particularly as far as fabrication of implants is concerned. The use of AM has made it possible to carry out surgical planning and simulation using a three-dimensional physical model which accurately represents the patients anatomy. AM technology enables the production of models and implants directly from a 3D virtual model, facilitating surgical procedures and reducing risks. Furthermore, AM has been used to produce implants designed for individual patients in areas of medicine such as craniomaxillofacial surgery, with optimal size, shape and mechanical properties. This work presents AM technologies which were applied to design and fabricate a biomodel and customized implant for the surgical reconstruction of a large cranial defect. A series of computed tomography data was obtained and software was used to extract the cranial geometry. The protocol presented was used to create an anatomic biomodel of the bone defect for surgical planning and, finally, the design and manufacture of the patient-specific implant.

Electrospun Polyurethane Membranes For Tissue Engineering Applications

Tissue Engineering proposes, among other things, tissue regeneration using scaffolds integrated with biological molecules, growth factors or cells for such regeneration. In this research, polyurethane membranes were prepared using the electrospinning technique in order to obtain membranes to be applied in Tissue Engineering, such as epithelial, drug delivery or cardiac applications. The influence of fibers on the structure and morphology of the membranes was studied using scanning electron microscopy (SEM), the structure was evaluated by Fourier transform infrared spectroscopy (FT-IR), and the thermal stability was analyzed by thermogravimetry analysis (TGA). In vitro cells attachment and proliferation was investigated by SEM, and in vitro cell viability was studied by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays and Live/Dead® assays. It was found that the membranes present an homogeneous morphology, high porosity, high surface area/volume ratio, it was also observed a random fiber network. The thermal analysis showed that the membrane degradation started at 254°C. In vitro evaluation of fibroblasts cells showed that fibroblasts spread over the membrane surface after 24, 48 and 72h of culture. This study supports the investigation of electrospun polyurethane membranes as biocompatible scaffolds for Tissue Engineering applications and provides some guidelines for improved biomaterials with desired properties.

Bio-based polyurethane for tissue engineering applications: How hydroxyapatite nanoparticles influence the structure, thermal and biological behavior of polyurethane composites

In this work, thermoset polyurethane composites were prepared by the addition of hydroxyapatite nanoparticles using the reactants polyol polyether and an aliphatic diisocyanate. The polyol employed in this study was extracted from the Euterpe oleracea Mart. seeds from the Amazon Region of Brazil. The influence of hydroxyapatite nanoparticles on the structure and morphology of the composites was studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the structure was evaluated by Fourier transform infrared spectroscopy (FT-IR), thermal properties were analyzed by thermogravimetry analysis (TGA), and biological properties were studied by in vitro and in vivo studies. It was found that the addition of HA nanoparticles promoted fibroblast adhesion while in vivo investigations with histology confirmed that the composites promoted connective tissue adherence and did not induce inflammation. In this manner, this study supports the further investigation of bio-based, polyurethane/hydroxyapatite composites as biocompatible scaffolds for numerous tissue engineering applications.

Microstructural and Mechanical Characterization of a Custom-Built Implant Manufactured in Titanium Alloy by Direct Metal Laser Sintering

Custom-built implants manufacture has always presented difficulties which result in high cost and complex fabrication, mainly due to patients’ anatomical differences. The solution has been to produce prostheses with different sizes and use the one that best suits each patient. Additive manufacturing technology, incorporated into the medical field in the late 80s, has made it possible to obtain solid biomodels facilitating surgical procedures and reducing risks. Furthermore, this technology has been used to produce implants especially designed for a particular patient, with sizes, shapes, and mechanical properties optimized, for different areas of medicine such as craniomaxillofacial surgery. In this work, the microstructural and mechanical properties of Ti6Al4V samples produced by direct metal laser sintering (DMLS) are studied. The microstructural and mechanical characterizations have been made by optical and scanning electron microscopy, X-ray diffraction, and microhardness and tensile tests. Samples produced by DMLS have a microstructure constituted by hexagonal α′ martensite with acicular morphology. An average microhardness of 370 HV was obtained and the tensile tests showed ultimate strength of 1172 MPa, yield strength of 957 MPa, and elongation at rupture of 11%.

Operability analysis and conception of microreactor by integration of Reverse Engineering and Rapid Manufacturing

Abstract The propose of this work is to develop high precision microfabrication faci lities using computer aided technologies as Reverse Engineering (RE) and Rapid Manufacturing (RM) process to analyze and design of microreactor. The microreactor is usually a continuous flow reactor in contrast to a batch reactor. The goal of microreactors is the optimization of conventional chemical plants, and also to open the way to research new process technologies and to synthesis of new products. In this work, microreactors fabricated using FDM method (Fused Deposition Modeling), were digitalized, using a 3D scanning, to redesign the object. The widths and thickness of the microchannels produced were analyzed by RE, and alterations and adjusts were performed in redesign strategies for better application. The approaches presented are also fundamental to verify microreactors geometry and for modeling/simulation by finite element analysis (FEA), to assure the metrological accuracy of geometry and optimization of process parameters. The integration of RE and RM computer aided technologies to conception and analysis of microreator, has been used to produce several different small scale microchannel devices for chemical processing applications.

Infrared laser stereolithography: prototype construction using special combination of compounds and laser parameters in localised curing process

Infrared Laser Stereolithography (ILS) is a novel and cost-effective method to produce three-dimensional (3D) plastic objects. An infrared laser beam is exploited to achieve localised curing with a thermosensitive resin containing a curing agent and a filling material. Physical and chemical models describing the localised curing process in ILS are presented. Differential scanning calorimetry (DSC) is used to characterise the curing process and to evaluate the curing rate as a function of temperature and activation energy. A mathematical simulation model, using the finite element method software Ansys, is applied to predict cure profiles of the resin as a function of laser radiation conditions, showing good agreement with experimental results. This novel stereolithographic process can provide 3D solid structures with good spatial resolution and no significant shrinkage. The stoichiometric amount and type of silica is found to be critical to confine the curing process to a localised volume.

Empirical models for end-use properties prediction of LDPE: application in the flexible plastic packaging industry

The objective of this work is to develop empirical models to predict end use properties of low density polyethylene (LDPE) resins as functions of two intrinsic properties easily measured in the polymers industry. The most important properties for application in the flexible plastic packaging industry were evaluated experimentally for seven commercial polymer grades. Statistical correlation analysis was performed for all variables and used as the basis for proper choice of inputs to each model output. Intrinsic properties selected for resin characterization are fluidity index (FI), which is essentially an indirect measurement of viscosity and weight average molecular weight (MW), and density. In general, models developed are able to reproduce and predict experimental data within experimental accuracy and show that a significant number of end use properties improve as the MW and density increase. Optical properties are mainly determined by the polymer morphology.

Ethanol Steam Reforming for Hydrogen Production in Microchannel Reactors: Experimental Design and Optimization

Abstract In this investigation, an experimental design procedure using prior literature information has been used to guide the localization of optimal points for reaction kinetics study. Three kinetic models were identified and the Pareto domain was circumscribed for a set of three decision variables and two objective functions to find an optimal solution. From the range of Pareto-optimal solutions obtained, the kinetic model considered to be the most reliable was used to explore the optimal operating region. Finally, the experimental design points were chosen to ensure a sufficient range of operating conditions to identify the reaction kinetics.

3D-Printed Craniosynostosis Model: New Simulation Surgical Tool

BACKGROUND Craniosynostosis is a complex disease once it involves deep anatomic perception, and a minor mistake during surgery can be fatal. The objective of this report is to present novel 3-dimensional-printed polyamide craniosynostosis models that can improve the understanding and treatment complex pathologies. METHODS The software InVesalius was used for segmentation of the anatomy image (from 3 patients between 6 and 9 months old). Afterward, the file was transferred to a 3-dimensional printing system and, with the use of an infrared laser, slices of powder PA 2200 were consecutively added to build a polyamide model of cranial bone. RESULTS The 3 craniosynostosis models allowed fronto-orbital advancement, Pi procedure, and posterior distraction in the operating room environment. All aspects of the craniofacial anatomy could be shown on the models, as well as the most common craniosynostosis pathologic variations (sphenoid wing elevation, shallow orbits, jugular foramen stenosis). Another advantage of our model is its low cost, about 100 U.S. dollars or even less when several models are produced. CONCLUSIONS Simulation is becoming an essential part of medical education for surgical training and for improving surgical safety with adequate planning. This new polyamide craniosynostosis model allowed the surgeons to have realistic tactile feedback on manipulating a childs bone and permitted execution of the main procedures for anatomic correction. It is a low-cost model. Therefore our model is an excellent option for training purposes and is potentially a new important tool to improve the quality of the management of patients with craniosynostosis.