Development of a Mechanically-Stimulated Tissue-Specific Extracellular Matrix Coated Scaffold for Tendon/Bone Interface Engineering

The enthesis is a complex anatomical and functional interface between tendon and bone. Once injured, this site does not readily heal and is repaired with limited success. To aid in repair of the enthesis a commercially available scaffold was chosen, from 3 candidate biomaterials, with fibroblast and osteoblast deposited extracellular matrix (ECM) to create a tendon and bone region, respectively, on the scaffold. To further enhance the ECM deposition, the seeded scaffold was mechanically stimulated in a custom built bioreactor for 35 days. The scaffolds were then evaluated by looking at tissue specific gene activation of mesenchymal stem cells (MSC)s due to the deposited ECM.Out of the three materials, non-degradable polyester fabric (PET), degradable polylactic acid (PLA) fabric, and biologic acellular dermal matrix (ACDM), the PLA fabric had the best combination of ECM deposition and mechanical strength for the project. After selecting a scaffold, we determined the parameters for co-culture medium, with respect to fibroblast and osteoblast mineralization. It was determined that standard growth medium, alpha-MEM + 10% fetal bovine serum + 1000 U/mL penicillin, 1000 μg/mL streptomycin, 2.5 μg/mL amphotericin-B + 3 mM beta-glycerophosphate + 25 μg/mL of ascorbic acid provided low fibroblast mineralization while still allowing for osteoblast mineralization. Fluorescence imaging demonstrated that a co-cultured scaffold could be seeded to produce two distinct tissue specific regions. The transition zone produced had values for collagen and glycosaminoglycan (GAG) deposition between that of the two tissue specific regions. Lastly after mechanical conditioning, stimulating the entire scaffold produced an increase in cell number, and the ratio of collagen to GAG in ECM compared to static culture. When the MSCs were exposed to the tissue specific regions, entirely stretched ECM caused an increase in collagen and tendon-specific GAG gene activation and a decrease in mineralization gene activation compared to tissue culture plastic. Cartilage specific markers were unchanged.In conclusion, a suitable commercially available scaffold was identified. The scaffold was seeded so a tendon specific and bone specific regions were distributed on the scaffold. Mechanically conditioning the scaffolds in a bioreactor increased the activation of tissue specific genes for tendon and bone compared to stem cells seeded on tissue culture plastic. Future work includes a functional scaffold testing in an in vivo tendon-to-bone animal model

Rationalizing the many uses of animals:Application of the 4N justifications beyond meat

Past research has uncovered four common justifications for using animals as food—the 4Ns—that eating meat is Natural, Normal, Necessary, and Nice. The current research investigated the extent to which the 4Ns might apply more generally to other animal uses. Two studies examined the moral justifications people spontaneously offered for various animal uses, including household products, clothing, culling, and horse racing (Study1), and in zoos, TV/film, as pets, and for medical testing (Study 2). Participants offered reasons for why it is okay to use animals and the responses were coded by independent raters. The 4N categories accounted for the majority of justifications across most uses. There was great variability in justification categories offered for each use, and some uses generated justification categories not covered within the 4N scheme, including humane treatment, prioritization of human lives, and sustainability arguments. This research provides a large-scope investigation of animal-use justifications that moves beyond meat consumption

Low-Cost Strider for Guatemala

The purpose of this project was to create a strider, a type of standing rehabilitation device, for children in developing countries who have trouble walking and supporting their full body weight. The project was initially brought to us by Cal Poly professor Brian Self, who had visited a clinic in San Marcos and determined that there were children there who had difficulties with walking and were a need for a rehabilitation device. The team discussed the problem with Dr. Self, Matt Robinson (a local San Luis Obispo prosthetist), and Cal Poly physics professor Pete Schwartz, all of whom had visited San Marcos previously, the determined that the device must also use appropriate technologies so that it could be easily reproduced for a low cost in clinics and for children to use at home in developing countries. For these reasons, the team chose to create the device from bamboo held together with composite joints. After researching material availability in San Marcos and existing bamboo and composite manufacturing techniques, the group designed a triangle-based structure made of dried bamboo for maximum strength. The design was analyzed using engineering analysis for the effects of bending, buckling, impact, and more. The team next created a prototype of the device at Cal Poly and tested it for failure before journeying to Guatemala to re-create the device at the clinic. In San Marcos, the device was completely manufactured in only three days and was also tested using a healthy 11-year-old girl. The team left the completed device, as well as two harnesses, at the clinic and is currently awaiting feedback from Dr. Rojas, who is in charge of the clinic and promised to use the device when disabled children come into the clinic. Nicole will continue to make improvements to the design as well as establish communication and relationships with other clinics interested in the device in the fall

The thermodynamic origins of chiral twist in monolayer assemblies of rod-like colloids

The propagation of chirality across scales is a common but poorly understood phenomenon in soft matter. Here, using computer simulations, we study twisted monolayer assemblies formed by both chiral and achiral rod-like particles in the presence of non-adsorbing polymer and characterise the thermodynamic driving forces responsible for the twisting. We observe assemblies with both like and inverted chirality relative to the rods and show that the preferred twist is already determined during the initial stage of the self-assembly. Depending on the geometry of the constituent rods, the chiral twist is regulated by either the entropy gain of the polymer, or of the rods, or both. This can include important contributions from changes in both the surface area and volume of the monolayer and from rod fluctuations perpendicular to the monolayer. These findings can deepen our understanding of why chirality propagates and of how to control it