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3D Tissue Scaffolds

Summary:

Our goal is to develop advanced measurement tools and standards for measuring scaffold properties and their impact on biological response.  

Description:

Use of 3D tissue scaffolds as a template for regeneration is the basis of tissue engineering. These tools will enable a better understanding cell-scaffold interactions, including identification of the relationships of cell response on 2D surfaces to that in 3D scaffolds, and will facilitate improved design of future scaffold-based medical products. These measurement tools and standards advance the ability of researchers to develop scaffolds that direct stem cell differentiation.

Additional Technical Details:


Drivers: 

  • The U.S. is in a healthcare cost crisis. We spend more of our GDP (18%) on healthcare than any other nation; second on the list Switzerland at 11%.
  • In 2004, the estimated total cost of treatment and lost wages associated with musculoskeletal diseases was $849 billion, equal to 8% of the GDP (American Academy of Orthopeadic Surgeons) 
  • Bone grafting is the second most common transplant procedure (blood is first) with 500,000 bone grafts performed each year in the US; 2.2 million procedures worldwide
  • Diabetes, a major tissue engineering target (pancreatic islets), affects 6 million patients and costs $125B/yr (6% of US healthcare spending).
  • We spend $35 billion annually (3% of healthcare costs) to care for the 100,000 patients with end stage organ failure waiting for organ transplants.

 

Reference Material Scaffolds: Reference material scaffolds are being developed that can serve as a calibration point for comparing scaffold measurements between different labs. The first generation reference scaffolds have been deployed and focus on scaffold structure and porosity. A second generation reference scaffold has been deployed and focuses on measuring cell response (adhesion and proliferation) to 3D scaffolds.  
 

Figure showing how a reference material scaffold can be used as a control for testing scaffolds. 

How Do You Use Reference Scaffolds? If two different labs run the NIST reference scaffolds as a control in their tests, then scaffold measurements from different labs can be compared. The y-axis may be any scaffold measurement such as porosity, permeability or cell adhesion.

 

First Generation - Scaffold Structure: A reference scaffold has been developed with input from ASTM Committee F04. The scaffolds were made by freeform fabrication since this approach offers the tightest control over scaffold structural morphology. Scaffold structure and porosity have been characterized using microscopy, gravimetrics and μCT imaging. These well-characterized reference scaffolds can serve as standards during development of scaffolds-based products where structure and scaffold porosity are measured.

 

 A picture of NIST reference material scaffolds RM8395, RM8396 and RM8396.

Left: Three different reference material scaffolds in their packaging: RM8395, RM8396 and RM8397. Middle: Table of RM scaffold properties. Right: 3D X-ray tomograph of RM8397.


Second Generation - Cell Response:
Second generation reference material scaffolds were deployed in May 2013 are desigend for measuring cell response. These are freeform fabricated scaffolds that fit into a 96-well plate for cell culture experiments. One unit is 24 scaffolds that have been structurally characterized and for which the cell responses of cell adhesion and proliferation have been measured. The reference scaffold plate can be run as a control in cell culture experiments to serve as a calibration point between different labs.

Pictures of reference material scaffold RM8397 for cell culture.

Left: Reference material scaffolds RM8394 are deployed. One unit is a 96-well plate with 24 scaffolds. RM8394 has strut diameter 300 μm, strut spacing 500 μm and porosity 60%. Middle: 3D X-ray tomograph of RM8394. Right: Fluorescence micrograph of MC3T3-E1 osteoblasts cultured 1 d on RM8394. Red staining is actin and green staining is the nucleus.

 

Links to Reference Scaffolds:

 
  

3D Scaffold Libraries: Cells respond differently to different materials. Chemistry, mechanics and structure of the materials have strong impact on whether cells adhere, proliferate, migrate or differentiate. We have pioneered the development of a suite of combinatorial screening methods for 3D scaffolds. Previous combinatorial approaches for screening cell-material interactions have focused on planar (2D) surfaces or films. However, biomaterials are commonly used in 3D scaffolds and cells behave differently when cultured in a 3D environment.  Thus, "combi" tests for many types of scaffolds and properties have been developed for a "scaffoldomics" approach.   

 

A figure illustrating how many approaches for screening cell response to polymer scaffold properties have been devised for a scaffoldomics approach.

"Combi" approaches for screening a wide range of 3D scaffolds have been developed to comprise a "scaffoldomics" approach.  

 

Links to Scaffold Library Fabrication YouTube Videos:

 

Cell-Material Interactions: Combi screens provide exciting "hits" that we can explore with more rigorously. Our goal is to enable design of improved scaffolding materials by determining how 3D scaffold properties influence stem cell differentiation. Much of our current knowledge of biomaterials is phenomenological.  In order for tissue engineering to advance, a mechanistic understanding of how material properties direct stem cell function must be developed.

   

Figures showing that integrins av and b3 are required for stem cells to interpret the modulus of their 3D environment. 

Left: Primary human bone marrow stromal cells (hBMSCs) deposit mineralized matrix when encapsulated in stiff poly(ethylene glycol) tetramethacrylate (PEGTM) hydrogels (21 d). Middle: During culture in PEGTM gels, hBMSCs deposit a matrix containing fibronectin (7 d). Right: RGDS peptides, antibodies that block integrin av , and antibodies that block integrin b3 , inhibit PEGTM-modulus-induced hBMSC mineralization (14 d, 5% PEGTM gels, 11 kPa compressive modulus). These results suggest that interactions between RGD peptides and avb3 integrins (not b1 integrins) are required for osteogenic differentiation of hBMSCs in stiff PEGTM gels.

 

Major Accomplishments:

  • Deployed first reference materials for the tissue engineering industry: reference material scaffolds developed in collaboration with ASTM that enable inter-lab comparison of scaffold measurements (RM8394, RM8395, RM8396, RM8397)
  • Developed a suite of combi methods for screening 3D tissue scaffolds comprising a scaffoldomics approach.
  • Developed the world's first combinatorial method for screening cell response to 3D tissue scaffold properties.
  • First demonstration that the modulus of 3D scaffolds can direct osteoblast differentiation
Image of a stem cell on a nanofiber scaffold.

Start Date:

October 1, 2007

End Date:

ongoing

Lead Organizational Unit:

mml

Customers/Contributors/Collaborators:


Peter Bajcsy, Software & Systems Division, NIST

Joachim Kohn, New Jersey Center for Biomaterials, Rutgers University

Wolgang Losert, Department of Physics, University of Maryland

Antonio Possolo, Statistical Engineering Division, NIST

Pam Robey, National Institute of Dental and Craniofacial Research, NIH

Amitabh Varshney, University of Maryland Institute for Advanced Computer Studies (UMIACS), University of Maryland

Hockin Xu, School of Dentistry, University of Maryland, Baltimore

Marian Young, National Institute of Dental and Craniofacial Research, NIH

Staff:

Carl Simon, Jr. - Project Leader
Paula Baker
Subhadip Bodhak
Desu Chen
Stephen Florczyk
Nathan Hotaling
Sumona Sarkar
Elissa Williams

Associated Products:

Contact

Carl G. Simon, Jr., Ph.D.
Biosystems & Biomaterials Division
carl.simon@nist.gov
301-975-8574