BEH. 462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 2: Molecular Design and Synthesis of Biomaterials I: Biodegradable Materials Chemistry of Biodegradable Materials Hydrolytically degraded biomaterials Common hydrolytically unstable linkages Ester (STRUCTURES Example polymers explored for use as biomaterials PLGA polyp (STRUCTURES) Poly(D, L-lactide) Poly (L-lactide) Poly(E-caprolactone) Stereochemistry of lactides: L-VS D-VS. D/L DRAWINGS OF STEREOSTRUCTURE 3D animation? Chemistry of hydrolysis: Physical chemistry of hydroly hydrolysis requires water to access the bonds: so structure has a strong effect on Factors influencing hydrolysis rates a. Degradation rate of PCL PLA PLGA steric interference crystallinity Controlling degradation behavior of solids for devices by choosing the right chemical structure solids may have dife ove factors in degradation rate, it is not surprising that biodegradable ven iffering modes of degradation ETCETCETC Enzymatically degraded biomaterials 1 of 1BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 2: Molecular Design and Synthesis of Biomaterials I: Biodegradable Materials Chemistry of Biodegradable Materials: I. Hydrolytically degraded biomaterials Common hydrolytically unstable linkages: Ester amide (STRUCTURES) Example polymers explored for use as biomaterials: (STRUCTURES) PLGA polypeptides Poly(D,L-lactide) Poly(L-lactide) Poly(ε-caprolactone) Polyanhydrides Stereochemistry of lactides: L- vs. D- vs. D/L DRAWINGS OF STEREOSTRUCTURE, 3D animation? Chemistry of hydrolysis: Physical chemistry of hydrolysis: -hydrolysis requires water to access the bonds: so structure has a strong effect on hydrolysis rates! -Factors influencing hydrolysis rates: 1. Hydrophobicity a. Degradation rate of PCL < PLA < PLGA 2. steric interference 3. crystallinity Controlling degradation behavior of solids for devices by choosing the right chemical structure: Given the above factors in degradation rate, it is not surprising that biodegradable solids may have differing modes of degradation: ETC ETC ETC II. Enzymatically degraded biomaterials 1 of 1