A Comprehensive Mechanical Characterization of Subject-Specific 3D Printed Scaffolds Mimicking Trabecular Bone Architecture Biomechanics

This study presents a polymeric scaffold designed and manufactured to mimic the structure and mechanical compressive characteristics of trabecular bone. The morphological parameters and mechanical behavior of the scaffold were studied and compared with trabecular bone from bovine iliac crest. Its mechanical properties, such as modulus of elasticity and yield strength, were studied under a three-step monotonic compressive test. Results showed that the elastic modulus of the scaffold was 329 MPa, and the one for trabecular bone reached 336 MPa. A stepwise dynamic compressive test was used to assess the behavior of samples under various loading regimes. With microcomputed tomography (µCT), a three-dimensional reconstruction of the samples was obtained, and their porosity was estimated as 80% for the polymeric scaffold and 88% for trabecular bone. The full-field strain distribution of the samples was measured using in situ µCT mechanics and digital volume correlation (DVC). This provided information on the local microdeformation mechanism of the scaffolds when compared to that of the tissue. The comprehensive results illustrate the potential of the fabricated scaffolds as biomechanical templates for in vitro studies. Furthermore, there is potential for extending this structure and fabrication methodology to incorporate suitable biocompatible materials for both in vitro and in vivo clinical applications.

Mechanical properties of polycaprolactone microfilaments for muscular tissue engineering

Polymeric scaffolds can be fabricated as microfilaments to replicate the mechanical characteristics and biological configuration of skeletal muscles and tendons. The microfilaments used in this research were fabricated from polycaprolactone (PCL) pellets by extrusion and a spooling system without using solvents. Their mechanical properties were investigated by applying monotonic and dynamic loads on aligned grouped microfilaments using a customized grip adapter. The fabrication method was simple and produced a homogeneous microfilament with a 90 ± 3 µm diameter. The monotonic tests showed the elasticity of the microfilaments was E = 1863 ± 590 MPa, and their yield strength was σy = 242 ± 45 MPa. The dynamic load test results showed that PCL microfilaments resisted periodic loads for 5.3×105 cycles, retaining a maximum deformation of 55%. The fabricated microfilament has the potential to be used as a biomimetic polymeric scaffold suitable for mechanical stimulation because of its outstanding mechanical behavior during dynamic loading conditions.

Muscle-like Scaffolds for Biomechanical Stimulation in a Custom-Built Bioreactor

Tissue engineering aims to develop in-vitro substitutes of native tissues. One approach of tissue engineering relies on using bioreactors combined with biomimetic scaffolds to produce study models or in-vitro substitutes. Bioreactors provide control over environmental parameters, place and hold a scaffold under desired characteristics, and apply mechanical stimulation to scaffolds. Polymers are often used for fabricating tissue-engineering scaffolds. In this study, polycaprolactone (PCL) collagen-coated microfilament scaffolds were cell-seeded with C2C12 myoblasts; then, these were grown inside a custom-built bioreactor. Cell attachment and proliferation on the scaffolds were investigated. A loading pattern was used for mechanical stimulation of the cell-seeded scaffolds. Results showed that the microfilaments provided a suitable scaffold for myoblast anchorage and that the custom-built bioreactor provided a qualified environment for the survival of the myoblasts on the polymeric scaffold. This PCL-based microfilament scaffold located inside the bioreactor proved to be a promising structure for the study of skeletal muscle models and can be used for mechanical stimulation studies in tissue engineering applications.

Análisis de pintura automotriz mediante espectroscopía Raman para uso forense

La aplicación de las técnicas espectroscópicas en el análisis de la evidencia forense es cada vez más frecuente debido la sensibilidad y confiabilidad de éstas. Se ha encontrado que cuando la evidencia consiste en fragmentos de pintura automotriz, las técnicas microscópicas de análisis visual en conjunto con las técnicas espectroscópicas, como la técnica Raman y el infrarrojo, pueden ayudar a identificar el vehículo del que proviene el fragmento. En este trabajo se demuestra que la técnica Raman resulta muy conveniente en el análisis de pequeños fragmentos de pintura, pues permite establecer su procedencia por comparación del perfil de los espectros, además, permite identificar algunos de los constituyentes de la pintura: matriz polimérica, pigmentos y otros componentes secundarios. En Costa Rica, el uso de la técnica de espectroscopía Raman, como parte de los análisis rutinarios en el Departamento de Ciencias Forenses del OIJ, está en proceso de desarrollo y por ello consideramos que los resultados de esta investigación pueden contribuir a su implementación.

Uso de la espectroscopia Raman en el análisis de fragmentos de pintura automotriz como evidencia forense

<p class="p1">En muchos accidentes de tránsito es difícil establecer la responsabilidad por los daños materiales, las lesiones a las personas o las muertes, debido a que los conductores de los vehículos responsables abandonan el lugar de los hechos. Por eso, es fundamental, como parte de la recolección de la evidencia, intentar recuperar fragmentos de pintura automotriz. El estudio de las características físicas de estos fragmentos puede permitir la identificación del vehículo del que provienen. Sin embargo, con frecuencia, esta evidencia presenta un tamaño reducido, del orden de milímetros cuadrados o menor, lo cual requiere que el análisis de las diferentes propiedades físicas no ofrezca riesgo de alteración de la muestra. Para ello, resulta conveniente utilizar métodos como los que ofrecen las técnicas microscópicas y espectroscópicas. En el presente trabajo se muestran los resultados de los análisis de varios fragmentos de pintura automotriz, realizados con microscopio óptico y microscopía Raman, que podrían ser utilizados como evidencia forense.</p>