379 research outputs found
Recommended from our members
Direct Freeform Fabrication of Spatially Heterogeneous Living Cell-Impregnated Implants
The objectives of this work are the development of the processes, materials, and tooling to
directly “3-D print” living, pre-seeded, patient-specific implants of spatially heterogeneous
compositions. The research presented herein attempts to overcome some of the challenges to
scaffolding, such as the difficulty of producing spatially heterogeneous implants that require
varied seeding densities and/or cell-type distributions. In the proposed approach, living implants
are fabricated by the layer-wise deposition of pre-cell-seeded alginate hydrogel. Although
alginate hydrogels have been previously used to mold living implants, the properties of the
alginate formulations used for molding were not suitable for 3-D printing. In addition to changing
the formulation to make the alginate hydrogels “printable,” we developed a robotic hydrogel
deposition system and supporting CAD software to deposit the gel in arbitrary geometries. We
demonstrated this technology’s capabilities by printing alginate gel implants of multiple materials
with various spatial heterogeneities, including, implants with completely embedded material
clusters. The process was determined to be both viable (94±5% n=15) and sterile (less than one
bacterium per 0.9 µL after 8 days of incubation). Additionally, we demonstrated the printing of a
meniscus cartilage-shaped gel generated directly from a CT Scan. The proposed approach may
hold advantages over other tissue printing efforts [5,9]. This technology has the potential to
overcome challenges to scaffolding and could enable the efficient fabrication of spatially
heterogeneous, patient-specific, living implants.Mechanical Engineerin
Characterization of mesenchymal stem cells and fibrochondrocytes in three-dimensional co-culture: analysis of cell shape, matrix production, and mechanical performance
Customized biomaterials to augment chondrocyte gene therapy
A persistent challenge in enhancing gene therapy is the transient availability of the target gene product. This is particularly true in tissue engineering applications. The transient exposure of cells to the product could be insufficient to promote tissue regeneration. Here we report the development of a new material engineered to have a high affinity for a therapeutic gene product. We focus on insulin-like growth factor-I (IGF-I) for its highly anabolic effects on many tissues such as spinal cord, heart, brain and cartilage. One of the ways that tissues store IGF-I is through a group of insulin like growth factor binding proteins (IGFBPs), such as IGFBP-5. We grafted the IGF-I binding peptide sequence from IGFBP-5 onto alginate in order to retain the endogenous IGF-I produced by transfected chondrocytes. This novel material bound IGF-I and released the growth factor for at least 30 days in culture. We found that this binding enhanced the biosynthesis of transfected cells up to 19-fold. These data demonstrate the coordinated engineering of cell behavior and material chemistry to greatly enhance extracellular matrix synthesis and tissue assembly, and can serve as a template for the enhanced performance of other therapeutic proteins
Matrix metalloproteinase activity and inhibition in articular cartilage : effects on composition and biophysical properties and relevance to osteoarthritis
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995.Includes bibliographical references (leaves 172-183).by Lawrence Justin Bonassar.Ph.D
Recommended from our members
A Study of Variable Stiffness Alginate Printing for Medical Applications
Technologies for multi-material 3D-printing of anatomical shapes are useful
both for fabrication of heterogeneous cell-seeded implants as well as for
fabrication of synthetic models for surgical planning and training. For both these
applications, it would be desirable to print directly with biological materials to
best emulate the target’s properties. Using a novel material platform, we
describe a series of experiments attempting to print variable-stiffness hydrogels.
We vary compliances by alternating 2% alginate hydrogel and a Dextran-infused
calcium chloride post-crosslinker. Stiffness throughout the construct ranged
from 4 kPa to 20 kPa as a function of post-crosslinker concentration, which was
spatially specified by the user.Mechanical Engineerin
Recommended from our members
Improved Quality of 3D-Printed Tissue Constructs Through Enhanced Mixing of Alginate Hydrogels
While alginate hydrogel is a desirable material platform for Solid Freeform Fabrication (SFF) of
cell-seeded tissue engineering scaffolds, achieving consistently high-quality results can be
challenging. Local variations in the material properties cause inconsistent material deposition
behavior and consequently decrease the resultant geometric fidelity of the construct. The effects
of gel mixing on material property consistency, geometric fidelity, and cell viability were
characterized in an attempt to improve the formulation’s compatibility with SFF processing.
Material homogeneity was quantified through a novel experimental setup composed of an
EnduraTEC mechanical test-frame and custom syringe-extrusion jig. Cell viability and
geometric fidelity were assessed using standard protocol. The baseline mechanical stiffness of
the printed samples was 16±3 kPa (n=6). We found that increasing mixing reduced material
inconsistency and improved geometric fidelity, without adversely affecting cell viability: the
printed construct quality was drastically improved by increasing mixing well beyond previously
established limits.Mechanical Engineerin
- …