Modeling poly(ethylene glycol) Diacrylate Hydrogels Synthesized by EosinY/TEA Visible Light Photopolymerization

Transcription

1 Modeling poly(ethylene glycol) Diacrylate Hydrogels Synthesized by EosinY/TEA Visible Light Photopolymerization Chu-Yi Lee, Georgia Papavasiliou, Omar Khalil and Fouad Teymour Department of Biomedical Engineering Department of Chemical and Biological Engineering Illinois Institute of Technology, Chicago IL Annual Meeting-November 5, 203

2 203 Motivation: Tissue Engineered Scaffolds 3D crosslinked structures of water soluble polymers High water retention capacity Tunable mechanical and physical properties (elastic modulus, crosslink density and swelling ratio) Patel et al. Tissue Eng. (9), 2005 Biocompatible: selectivity of biofunctionalization cell adhesion ligands: growth factors : degradable peptide domains: + cells enzymes

3 203 PEG Diacrylate Hydrogel Synthesis Free Radical Photopolymerization - Visible Light (λ = 54 nm) Photoinitiation: Photosensitive dye (Eosin Y) /Coinitiator (Triethanolamine) Monomers PEGDA NVP O C Acryl-PEG-RGD O ( O ( n O Acryl-PEG-RGD N H RGD Reaction Cell λ = 54 nm Sample volume: 52 µl

4 Objective Develop and validate a kinetic model of PEGDA hydrogel formation by free-radical photopolymerization Photoinitiation mechanism Light absorption experiments: Varied I o, [Eosin Y], [TEA] I I t = 0 ε l c 0 c, ε I t Developed and validated a kinetic model of photoinitiation Linear polymerization model: NVP polymerization Computational Model of Hydrogel Formation Hydrogel properties RGD incorporation 203

5 Proposed Photoinitiation Mechanism 203 Eosin Y Photobleaching fit Regeneration of Eosin Y.. fit Avens and Bowman. J Pol Sci Part A, 2009: Encinas et al. Polymer, 2009, 50:

6 203 Photoinitiation: Effect of Intensity [Eosin Y] = 2.5 x0-5 M No TEA [Eosin Y] = 5 x0-5 M No TEA [Eosin Y] = 7.5 x0-5 M No TEA [Eosin Y] = 2.5 x0-5 M With TEA [Eosin Y] = 5 x0-5 M With TEA [Eosin Y] = 7.5 x0-5 M With TEA

7 Photoinitiation: Effect of Eosin Y No TEA I 0 = 4.3 mw/cm 2 No TEA I 0 = 28.6 mw/cm 2 No TEA I 0 = 42.9 mw/cm 2 With TEA I 0 = 4.3 mw/cm 2 With TEA I 0 = 28.6 mw/cm 2 With TEA I 0 = 42.9 mw/cm 2 203

8 Photoinitiation: Model Comparison Exp Model % Trasmitted light Eosin=2.5e-5 I 0 = % Trasmitted light Intensity Eosin=2.5e-5 I 0 = % Trasmitted light Eosin=2.5e-5 I 0 = % Trasmitted light Eosin=5e-5 I 0 = % Trasmitted light Eosin=5e-5 I 0 = % Trasmitted light Eosin=5e-5 I 0 = EosinY % Trasmitted light Eosin=7.5e-5 I 0 =4.3 % Trasmitted light Eosin=7.5e-5 I 0 =28.6 % Trasmitted light Eosin=7.5e-5 I 0 =

9 Photoinitiation Mechanism: Validation with NVP polymerization hν polymerize +THF dry D :2.4mm Precipitation mm Varied: I o, [Eosin Y], [TEA] Intensity (mw/cm 2 ) Intensity distribution) Layering Location (mm) 203

10 Photoinitiation Model: validation with polynvp conversion 0.2 [EosinY] 0 Varied [Eosin Y] x0-4 Conversion of PNVP x0-5 5x x time(sec) 203

11 Computational Model of Hydrogel Formation Kinetic mechanism Photoinitiation Propagation (PEGDA, NVP, Acryl-PEG-RGD) Termination (by Combination) Pendant double bond propagation Chain Transfer to TEA Primary Radical Termination Population balances QSSA for Radicals Pseudokinetic Rate Constants Numerical Fractionation Technique Teymour and Campbell; Macromolecules.(32), 994 Q 2 sol Time (sec) gel point

12 Experimental Design and Model Validation Model Predictions Experiments # units in gel gel fraction = # units in sol + # units in gel # of crosslinks in the gel CLD = # of repeat units in the gel Gel fraction / swelling ratio fixed [Double Bonds] [ RGD] = # of RGD in the gel # of repeat units in the gel # of crosslinks in the gel CLD = # of repeat units in the gel 25 IYRGD (radiolabeling) / swelling ratio fixed overall [Monomer] 203

13 Crosslink Density as a function of PEGDA fraction PEGDA MW = 3400 g/mol; 5 minute exposure Dimensionless Crosslink Density High [PDB] Region PEGDA fraction PEGDA fraction

14 Crosslink Density as a function of PEGDA fraction PEGDA MW = 575 g/mol; 5 minute exposure Dimensionless Crosslink Density PEGDA fraction PEGDA fraction PEGDA fraction

15 Crosslink Density Dynamics Dimensionless Crosslink crosslink density Density % 20% 30% 50% 60% 70% 80% 85% 98% Time 50% 60% 30% 20% 0% 80% 85% 98% 70% % 48% 0 % 9 % /Q w % 00% 9% 0% 48 % 80 % 85 % 00 %

16 Gel Fraction Dynamics 20% 50% 0% 5% 80% Gel fraction Gel fraction 85% 98% 0.2 5% 0% 20% 0 50% 80% 85% 95% Time (sec) 203 Gel Fraction % 80% 9% 85% 00% 0% 0 % 9 % 48 % 80 % 85 % 00 %

17 RGD Incorporation 0. Dimensionless RGD (wt basis) Model 2 min 5 min RGD Precursor Concentration (mg/ml) 203 Annual Meeting Dimensionless RGD Incorporation (wt basis) min 5 min Experiments RGD Precursor Concentration (mg/ml)

18 Crosslink Density as a function of [RGD] Dimensionless Dimensionless Crosslink Crosslink Density Density 5.05E E E E E E E E E E E E E E-02 Model (5(2 min) min) [RGD] (mg/ml).20e-0.40e-0.00e-0.20e-0.00e E-02 /Qw /Qw 8.00E E E E E E E E+00 Experiments Experiments (5(2 min) min) [RGD] (mg/ml)

19 Conclusions Validated photoinitiation kinetic mechanism Coupling measurements in light absorption and modeling of photoinitiation Validation of a model of linear polymerization of polynvp with conversion Developed a computational model of hydrogel formation Model simulations compared favorably with experimental measurements crosslink density, gel fraction dynamics, RGD incorporation The combined study provides a predictive capability for design and optimization of scaffolds for tissue engineering applications

20 203 Annual Meeting Acknowledgements Graduate Students Reza Ghodsi Neha Bansal Michael Turturro Undergraduate Students Joshua James Funding Sources