Thermally reversible gels for tissue engineering and wound healing.

1. Hydrogel Composites with Carbon
Nanobrushes for Tissue
Engineering
William H. Marks & Carolina I. Ragolta
Additional Authors
Sze C. Yang, George W. Dombi, & Sujata K. Bhatia
March 8, 2013 Sigma Xi
Competition

2. Medical Need: Cardiac
Regeneration
✤ Coronary Artery Disease
is a leading killer of men
and women worldwide
✤ Congestive heart failure
has 1-year mortality rate
of 40%
✤ Image Source: National
Heart Lung and Blood
Institute

3. Medical Need: Cardiac
Regeneration
✤ Myocardial infarction
can lead to death of 109
cardiomyocytes
✤ 1.5 million Americans
suffer myocardial
infarctions each year
✤ Image Source: Medicine.net

4. Abstract
✤ Study carbon nanobrushes (CNBs) embedded in
hydrogels for scaffolding in tissue engineering
✤ CNBs provide internal structure, conductivity, and are
non-toxic
✤ Tested the ability of fibroblasts and myocytes to adhere to
the gel and mechanical properties
✤ CNBs alter mechanical properties providing a high degree
of customization
✤ Gels show promise for many wound healing applications

5. Medical Need: Regenerative
Medicine
✤ Biomaterials must be biocompatible, non-cytotoxic,
non-hemolytic, and non-inflammatory
✤ They must degrade within the physiologic
environment
✤ Must be easily prepared, implantable, and scalable
✤ Must be clinically relevant

6. Prior Related Work
✤ Cell encapsulation for 3D tissue growth (Hunt et al., 2010)
✤ Collagen matrices for fibrogenesis (Chen et al., 2009)
✤ Alginate gels with carbon nanotubes provide mild
inflammatory response (Kawaguchi et al., 2006)
✤ “Scar in a Jar” collagen matrix for flexor tendon healing
(Dombi et al., 1994)
✤ Cartilage tissue engineering by accurately spinning
hydrogels (Coburn et al., 2011)

7. Clinically Relevant Cell Lines
Primary Cardiac Fibroblasts Primary Cardiac Myocytes
Source: Dr. Andrew Pelling, UCL Source: Dr. Poling Kuo, Harvard

8. Carbon Nanobrushes
✤ Electrically conducting
polymers grafted onto
carbon nanotubes
✤ Conductivity of materials is
about 0.1 S/cm
✤ 5-20µm in length
✤ 13-30nm in diameter
✤ Imaged by negatively
staining with
phosphotungstate

9. Pluronic F-127 Poloxamer
Hydrogels
✤ Reverse phase-change properties: solid at 37℃, liquid at
room temperature
✤ Triblock copolymer of PEO-PPO
✤ Non-ionic and biocompatible

10. Preparation of Composite
Hydrogels with Carbon
Nanobrushes
✤ 30wt% poloxamer solution
✤ Various CNB
concentrations
✤ 0vol%
✤ 0.1vol%
✤ 0.5vol%
✤ 1vol%
✤ Solidified at 37℃ and then
seeded with cells and
DMEM

11. Growth of Fibroblasts
Fibroblasts in top layer of poloxamer gel after 48 hours

12. Migration of Fibroblasts
Fibroblasts in middle layer of Fibroblasts in bottom layer of
poloxamer gel after 48 hours poloxamer gel after 48 hours

13. Growth of Myocytes
Myocytes in top layer of poloxamer gel after 48 hours

14. Rheology: Temperature Sweep
Temperature sweep test of gels containing 0vol% and 5vol% CNB

15. Rheology: Time Sweep
Time sweep test of gels containing 0vol% and 5vol% CNB at 37℃

16. Rheology: Frequency Sweep
Frequency sweep test of gels containing 0vol% and 5vol% CNB at 37 ℃
showing a crossover from predominately elastic to predominately viscous

17. Discussion
✤ Hydrogels embedded with CNBs support cell growth and
migration
✤ CNBs change the properties of the gel on a macro scale by
altering the frequency of the sol-gel transition point
✤ Gels transition from predominately elastic to
predominately viscous
✤ Additional degree of customizability

18. Ongoing and Future Work
✤ Properties of gels with different wt% of poloxamer
✤ Incorporating crosslinkers into hydrogels
✤ Injectability
✤ Experiments with additional cell lineages

19. Translational Potential
Skin Grafts Tissue Patches Tissue Scaffold
Source: Medline Source: Gore Source: National
Institute of Standards
and Technology

20. Acknowledgements
✤ Dr. Sujata K. Bhatia, SEAS, Harvard
✤ Dr. Sze C. Yang, University of Rhode Island
✤ Dr. George W. Dombi, University of Rhode Island
✤ Dr. Patrick Campbell, SEAS, Harvard (Disease Biophysics
Group)
✤ Harvard School of Engineering and Applied Sciences