Hydrogels. Soft materials for tissue repair Contact lenses Slow or smart drug release implants Diaper absorbent Toys (slime) food

Transcription

1 Hydrogels A hydrogel is a gel in which water is the dispersed media Hydrogel is typically a 3D network of hydrophilic polymer molecules that attract water molecules Many applications, including Soft materials for tissue repair Contact lenses Slow or smart drug release implants Diaper absorbent Toys (slime) food

2 Hydration

3 Hydration - effect of salt

4 Hydrogel Valves

5 Many hydrogels are dynamic

6 Classes of Hydrogels Thermal raise/lower Temperature to gel Gelatin Agar Ionic add ions to gel Agarose Cryogel freeze/thaw cycles create gel Polyvinyl alcohol Covalent chemical bonding of polymers Polyvinyl alcohol/glutaraldehyde

7 A Cooper Union Connection Glue Factory 1845 Patent Instant gelatin in small packages Competing product: gelatin sheets

8 Tissue Engineered Blood Vessels State of art 1. Internal mammary a. 2. Sapphenous vien 3. Artificial materials (>6mm ID; NVG) What is needed? Suture and healing Withstand 400 mmhg No thrombosis No hyperplasia Similar compliance Adjust diameter

9 Tissue Engineering Approaches Layer-by layer assembly Cells (fibroblasts) make collagen layers Roll into multilayer tube Culture under flow and strain Add endothelium Implant Resorbable polymer scaffold seeding Surface treat, seed with smooth muscle cells Culture under flow and strain Add endothelium Implant

10 Human Cell TE Blood Vessel L Heureux et al.

11 Human Cell TE Blood Vessel Niklason et al

12 What makes them work? History prior to L Heureux, Niklason Burst strengths of 10 to 20 mmhg Importance of stress/strain during culture New approaches Used high-ascorbate growth medium» Boosts collagen synthesis Included stress/strain Multistage culture process Burst pressures over 1000 mmhg Outcome differences Elastin observed in L Heureux s method

13 Where are we now? Discovery was 9 years ago In vivo testing is difficult Immunological rejection How to prove safety? Will artery degrade in vivo? Are they arteries? Wall was thicker relative to lumen Less compliant Higher burst pressure

14 Tissue Engineering Manufacturing How to make tissues more efficiently? How to improve control of tissue constructs? Use modern manufacturing methods

15 Electrospinning

16 Salt Leaching Agrawal CM et al, eds, Synthetic Bioabsorbable Polymers for Implants, STP 1396, ASTM, 2000

17 Freeze Drying

18 Phase Separation

19 Bulk methods summary Relatively fast batch processing Often low investment required Non optimal structures (due to randomness): High porosity required for connectedness Permeability often low (especially foams) Strength is low (eg too low to replace bone)

20 CAD-based Porogen Method Mondrinos M et al, Biomaterials 27 (2006)

21 Photopatterning Surface Chem.

22 Microcontact and Microfluidic Printing

23 Micromachining, Soft Lithography Soft Lithography

24 3D Printing Spread powder layer Print powder binder

25 Solid Freeform Fabrication Make arbitrary shapes Limited resolution Incrementally build Layer by layer Fuse Layers to get 3D part Several processes including Fused deposition Drop on demand Laser sintering CONF/SOFE99/waganer/fig-2.gif

26 Current Research on Scaffolds Senior Project/Research Project Opportunity Electrowetting-based tissue manufacturing technology Print:» Hydrogel» Crosslinker» Cells» Growth Factors Dead Live

27 Biomedical Engineering Very broad field Imaging, biosensors, clinical engineering, surgical robotics, and more Strong research orientation Some agreement about 4 year degree contents Growth of acceptance and recruiting Biomedical Applications of ME, ChE, EE, OR, provide countless opportunities Biomedical engineer understands living systems (and creates models) to design, optimize, and test biomedical devices, diagnostic tools, implants,

28 Biomedical Engineering at Cooper Union Centers Kanbar Center Center for Signal Processing, Communications and Computer Engineering Research (S*ProCom 2 ) People: Wootton, Ben-Avi, Duncan, Fontaine, Sidebotham, Delagrammatikas, Ahmad, Ahmed, Cumberbatch, Uglesich, Savizky, Wei, and others

29 Biomedical Engineering at Cooper Union Research and Project Activities include Orthopedic biomechanics Tissue engineering manufacturing Obstructive Sleep Apnea biomechanics and research Operating room safety and thermal management Neural processing of visual data Novel MRI hardware/software development Magnetic resonance elastography Hemostasis and Thrombosis Infrared imaging diagnostics Knee simulator Trans-bronchial needle aspiration tracking system Magnetic muscle activation Novel gait force sensors for free subject studies