Fred Allen

Accelerated differentiation of osteoblast cells on polycaprolactone scaffolds driven by a combined effect of protein coating and plasma modification

A combined effect of protein coating and plasma modification on the quality of the osteoblast-scaffold interaction was investigated. Three-dimensional polycaprolactone (PCL) scaffolds were manufactured by the precision extrusion deposition (PED) system. The structural, physical, chemical and biological cues were introduced to the surface through providing 3D structure, coating with adhesive protein fibronectin and modifying the surface with oxygen-based plasma. The changes in the surface properties of PCL after those modifications were examined by contact angle goniometry, surface energy calculation, surface chemistry analysis (XPS) and surface topography measurements (AFM). The effects of modification techniques on osteoblast short-term and long-term functions were examined by cell adhesion, proliferation assays and differentiation markers, namely alkaline phosphatase activity (ALP) and osteocalcin secretion. The results suggested that the physical and chemical cues introduced by plasma modification might be sufficient for improved cell adhesion, but for accelerated osteoblast differentiation the synergetic effects of structural, physical, chemical and biological cues should be introduced to the PCL surface.

Fabrication and plasma treatment of 3D polycaprolactane tissue scaffolds for enhanced cellular function

This paper reports a solid free-form fabrication (SFF) technology-based precision extrusion deposition (PED) process to manufacture three-dimensional (3D) polycaprolactane (PCL) scaffolds and their surface treatment with a plasma source for enhanced osteoblast cell adhesion and proliferation. The PED process allows us to manufacture tissue engineering scaffolds based on designed geometry with complete interconnectivity and controllable porosity. The as-fabricated PCL scaffolds have a pattern with a 0/90° strut configuration of 300 µm pore size and 250 µm strut width. In order to improve cellular activity on 3D PCL scaffolds, they were surface-treated with an oxygen-based plasma source. The surface hydrophilicity and total surface energy of PCL was increased with plasma treatment. Comparisons of different plasma treatment times, including 30 seconds, and 1, 2, 3, 5 and 7 minutes, were performed to identify the plasma treatment duration suggesting higher cellular adhesion and proliferation. The maximum value of total surface energy and its components (polar and dispersive) was observed in 3-min treated PCL scaffolds. In addition, the positive effect of plasma treatment was observed in stregth of cell adhesion, which was increased 55% on 3-min plasma-treated scaffolds compared to untreated and other plasma treatment duriations. Cell culture study over a 7-day period also showed that the cell number on 3-min treated scaffolds is 3-fold the number of cells on untreated scaffolds.

Steady Unidirectional Laminar Flow Inhibits Monolayer Formation by Human and Rat Microvascular Endothelial Cells

Endothelialization of artificial vascular grafts is rapid and complete in numerous animal models, including dogs and rats, but not in human patients. One possible explanation for this well-known, yet puzzling observation might be that monolayer formation of human endothelial cells (ECs), and of canine or rodent ECs, is affected differently by flow-induced shear stress. To begin testing this hypothesis, the authors wounded confluent monolayers of cultured rat and human ECs and exposed these cultures for 20 h to unidirectional steady laminar shear stress of 10 dyn/cm(2) induced by fluid flow perpendicular to the wound boundaries. In comparison to experimental control cultures simultaneously maintained under static (no-flow) conditions, flow-induced shear stress attenuated the monolayer formation (sheet migration) in both human and rat ECs. In brief, compared to control, the average human EC monolayer formation under shear was reduced by 33% whereas the average rat EC monolayer formation was reduced by 34%. Furthermore, the cell responses showed a dependence on fluid flow direction that differed per species. When exposed to shear stress, human EC monolayer formation was reduced by 16% in the upstream direction (opposing the direction of flow) and reduced by 50% in the downstream direction (with the direction of flow), whereas rat EC monolayer formation was reduced by 64% upstream and showed no change downstream. These findings suggest that although overall monolayer formation is inhibited by fluid-induced shear stress to the same extent in both species, there are cell type- and/or species-dependent migration responses to fluid-induced shear stress, and that different flow conditions possibly contribute to species-specific patterns of endothelialization.

A combinatorial effect of plasma modification and protein coating on osteoblast differentiation for tissue engineering scaffolds

Summary form only given. Physical and chemical cues introduced on the microenvironment of cell may alter and regulate the cellular activity. Up to now, the positive effect of plasma modification and protein coating of biopolymer on cell attachment and proliferation has been studied excessively on planar surfaces1. However, based on our knowledge, the synergetic effect of plasma modification and protein coating on 3D scaffolds for long term cellular response including differentiation has not been studied. In this study, we investigated the combinatorial effect of adhesive protein coating and plasma modification on polycaprolactane (PCL) scaffolds for osteoblast differentiation compared to adhesive protein coating and plasma modification alone. We worked on four different groups of scaffolds; unmodified PCL (UP), plasma modified PCL (PP), fibronectin coated PCL (FNP) and plasma modified-fibronectin coated PCL (P-FNP). The surface characterization was done by contact angle measurement, surface energy calculation, surface roughness via atomic force microscopy, surface chemistry via X-ray photoelectron spectroscopy. The biological characterization was done through measuring strength of cellular adhesion, measuring rate of metabolic activity over time, observing early and later stage differentiation rate via alkaline phosphatase activity and osteocalcin secretion. Based on results, we found that rate of cellular differentiation strongly depends on the combination of physical, chemical and biological modification of PCL surfaces. More specifically, the early and later differentiation markers, the alkaline phosphatase activity and osteocalcin expression, increased more rapidly on plasma modified-fibronectin coated (P-FNP) scaffolds compared to UP, FNP, P-FNP.

Work in progress - an evidence-based intervention system to enhance engineering education

A major difficulty in assessment is the problem known as ‘closing the loop’ — ensuring that assessment data is used effectively for program improvement and to enhance student learning. There are a number of reasons why current assessment procedures do not always succeed at this necessary phase of the process. First and foremost is that assessment has been tied to accreditation and viewed by many faculty and administrators as a necessary evil to be dealt with as little expenditure of time and effort as possible. As long as some program changes can be linked to the assessment process — thus satisfying the external accreditors — the bulk of the data being collected can be safely ignored. A second factor is the data itself. In order for the assessment process to be effective, the right kind of data must be collected in the right amount. However, there seems little consensus as to the kind and amount of data to collect. Finally, the nature of faculty instruction in higher education can itself be an impediment. Faculty instructors are often unaware of how their particular courses fit into the overall curriculum, beyond vague knowledge of what pre-requisite courses should have been taught. A partial solution to these problems is currently under development through a partnership between Drexel University and Untra Academic Management Solutions, LLC. The proposed solution is the development of an Instructional Decision Support System (IDSS). We define an IDSS as an interactive computer-based information system which links student characteristics, student performance, instructor characteristics, learning outcomes, and instructional methods to inform faculty decisions on the appropriate educational pedagogy to improve student learning. As envisioned, the IDSS provides student and course data in context to each faculty instructor as he or she teaches their course.