Richelle C. Thomas, Christine E. Schmidt Department of Chemical Engineering University of Texas at Austin 1

The Neuropathy Association “Peripheral Neuropathy Market Approaches US$1B by 2012”, 04/7/2010 /PRNewswire/ 1B affected patients in U.S., Europe & Japan 1B affected patients in U.S., Europe & Japan US $1B industry by 2012 >2.5% growth annually >20M Americans suffer from some form of peripheral neuropathy Annual cost to Medicare US$3.5 B + 2

3 Diabetes Congenital birth defects Cancerous tumors

4 Motor Vehicle Accidents Cuts/Scrapes Wartime

 Eliminating symptoms  Pain  Numbness  Addressing the root cause of the nerve damage 5

Fourth Degree Fifth Degree Injuries Requiring Treatment Peripheral Nerve Axon Endoneurium where Schwann cells are Perineurium Epineurium Third Degree Second Degree First Degree Injuries That Autologously Recover 6

End-to-End Suturing Conduit/ImplantGrafting Communication between nerve stumps Physical guidance to regenerating axons 7

Lee et al. (2002) Gomez et al. (2006) Huang et al. (2008) 8

 Extracellular matrix component  Polyanionic  Hydrophillic  Involved in mediating wound repair  Non-cell adhesive 9

Modulate Swelling Degradation Mechanical Properties Advantages Biocompatible Non-cell adhesive Control local chemical properties Optically transparent High Swelling HA Hydrogels 1 min 20 min2 min 5 min10 min UV Exposure 10 Problem: Amorphous gels only offer chemical and no physical cues

Physical cues are preferred over chemical cues for axon initiation (polarization) 70 %  Physical Cues (microchannels) 30 %  Chemical Cues (NGF or Laminin) Microchannels vs. Laminin 25  m 12  m Gomez, Chen, Schmidt (2007). J. R. Soc Interface. 4(13): Gomez, N., Schmidt, C.E. (2007) Biomaterials. 28 (2):

 Photolithography  Microfluidic patterning  Electrochemical deposition  3D printing 12 Excellent X-Y control Limited control over z- direction coherence of layers and local chemistry Limited in extent of complexity can achieve Expensive equipment required

Template natural polymer hydrogels using self- assembling colloidal crystals for 3D internal architecture 13

Methacrylated Hyaluronic Acid 0.1-1% Photoinitiator Poragen of choice 14

15 Spindle Crystalline Structure Dendritic Crystalline Structure Guanidine Glycine Potassium Dihydrogen Phosphate Urea

0.5% GMHA, 0.5% I2959, cryoSEM

Zawko, Schmidt. (2010) Acta Biomaterialia. Zawko, S.

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spindle crystalline morphology present macroscopic porous network apparent throughout z-dimension complexity not restricted to x-y dimension Scale Bar: 150 um Scale Bar: 500 um Dextran-FITC 19 2 mm 1.5 mm

Zawko, Schmidt. (2010) Acta Biomaterialia. Zawko, S.

sparse crystalline network templating traverses the z-dimension macroscopic porous network apparent throughout z-dimension Scale Bar: 200 um Scale Bar: 300 um Dextran-FITC 22

 Bulk Properties  Swelling  Degradation  Storage Modulus  Effect of templating on hydrogel properties 23

2 3 10mM PBS WSWS 1 hr, 40˚C 50 U/mL Hyaluronidase WtWt 24 % Degradation = __________ x 100% W S - W t WSWS

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26 Not templated hydrogels have ability for degradation to be modulated through PI content and UV exposure

27 Templated hydrogels retain ability for degradation to be modulated through PI content and UV exposure

28 Swell Ratio = _________ W S - W D WDWD 10mM PBS WSWS 1 WDWD 2

29 At completion, templated hydrogels swell more than amorphous Higher PI amounts, reduced swelling

 Strain sweep at constant frequency until reaches plateau  Choose strain in plateau region  Conduct frequency sweep at constant strain and measure storage modulus 30

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 Culture cells in 24 well plate for 24 hours  25,000 cells per well  Put gels in transwells suspended in cell media for 24 hours  Analyze ATP with CellTiter Glo assay 32

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35 Both chemical and physical guidance cues are important to achieve optimum scaffold Simple system for tissue engineering applications – able to be tailored for tissues/applications Retain control over hydrogel properties after templating Impose architecture over 1.5mm z-length scales [urea] Impose architecture that sparsely traverses the z-dimension [KH 2 PO 4 ] Fibroblast cell viability not hindered as result of templating process

 Dr. Christine E. Schmidt  Labmates  Dr. Leandro Forciniti, Sarah Mayes, Dr. John Hardy  Undergraduate Researchers  Shan Modi, Paul Chung, Brittany McGhee 36

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