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button  Structure-Property Relationships in Dental Polymers and Composites
     button  Nanocomposite Dental Materials
  button  Structure-Property Relationships of Hydrogels for Dental and Craniofacial Applications
  button  The Effect of an Organogelator on Bioactive Dental Composites
  button   High-throughput and combinatorial methods for measuring the mechanical properties of dental materials
button  Combinatorial Methods for Rapid Screening of Biomaterials
  button  High-throughput Method for Determining Young’s Modulus of Polymer Blends
  button  Inflammatory Cytokine Quantification of Cell-SCK Interactions via RT-PCR
  button  Peptide Derivatized SCK Nanoparticles
  button  Real-Time Polymerase Chain Reaction
  button  Gradient Library Screening of Cell-Material Interactions
  button  Surface Energy Gradients for Characterizing Cell-Material Interactions
  button  High-throughput Method for Characterizing Cell Response to Polymer Crystallinity
  button   Cellular Response to Bis-GMA/TEGDMA Vinyl Conversion Gradients
button  Metrologies for Tissue Scaffolds
  button  Focal Adhesions of Osteoblasts on Poly(d,l-lactide)/Poly(vinyl alcohol) Blends by Confocal Fluorescence Microscopy
  button   2D -->3D Cell / Scaffold Interactions
  button  Development of a Reference Scaffold
  button   In Vitro Cartilage Development
  button   Gene Expression Profiles of Cells in Response to Tyrosine Polycarbonate Blends
  button Broadband Coherent Anti-Stokes Raman Scattering (CARS) Microscopic Imaging
  button Collinear Optical Coherence and Confocal Fluorescence Microscopies
 

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Gene Expression Profiles of Cells in Response to Tyrosine Polycarbonate Blends
 

Introduction

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Tyrosine-based polycarbonates are promising degradable polymers for orthopedic applications. The physical and chemical nature of the pendant ester substituent affects significantly the mechanical properties, degradation rates, and cellular responses. Assessment of material biocompatibility is a complicated process, which includes both in vitro and in vivo measurement methods, each of which depend on the physical and chemical nature of the material and the biological interaction. Furthermore, a clear framework outlining the critical interactions governing biomaterial performance does not exist. Our efforts have focused on developing in vitro assays for measurement of inflammation and extracellular matrix (ECM) gene regulation, which we anticipate will provide preliminary assessments of in vivo material performance and establish metrologies for biocompatibility thresholds.

Experimental Approach

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DTR polycarbonate homopolymers and blends were spun coat onto 22 mm round glass coverslips. Blends were mixed in various compositions using DTE and DTO tyrosine-derived polycarbonates in 70/30, 50/50, and 30/70 ratios (by mass). The discrete DTE/DTO blends form phase-separated domains whose size and spacing are tunable by varying the composition of the blend.

Significant differences in inflammatory cytokine expression and minimal changes in extracellular matrix production suggested that optimizations could be made with regard to composition. A series of blends were made to outline small areas of physical parameter space to probe whether significant differences in cell response existed and could be measured.

From left to right in the three 5 mm × 5 mm AFM images shown above, the amount of DTO is increasing. The discrete DTE/DTO blends form phase-separated domains under in vacuo, 105 °C annealing conditions. The size and spacing of the domains are tunable by varying the composition of the blend.
 

Results
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Gene copy numbers of interleukin-1B and fibronectin (B & D) after 24 h of surface exposure on the respective homopolymers and blends for RAW 264.7 macrophages and MC 3T3 bone osteoblasts.

The levels of interleukin-1B, and fibronectin were measured to determine if and to what extent discrete DTE/DTO blends affect the expression profiles of the cells. The underlying physico-chemical parameters causing the differences in IL1-? gene expression are unknown at this point and is currently being investigated further. The blends displayed levels of FN that were relative to levels of TCPS.

Phase contrast microscopy was used visualize the populations to examine if gross changes were occurring in the cytoskeleton or in the periphery of the cells. In both the macrophage and osteoblast populations, the cells maintained a consistent, normal morphology on all of the materials and compositions.

Future work involves continuous gradients, ELISA measurements and Correlations with 3D Scaffolds

Funding from a NIST Competence Award and NIH NIBIB
(Integrated Technologies Resource for Polymeric Biomaterials)
are gratefully acknowledged

NRC Postdoctoral Fellowships for M.L.B. & J.S.S.
 

NIST Contributors

 
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Matthew L. Becker
Eric. J. Amis
Lee Ann O. Bailey
Jean S. Stephens
 

Rutgers Collaborators:
 
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Professor Joachim Kohn
Jaap Schut
Aarti Rege
 
 
 
 
 
 
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