Effect of Molecular Weight and Functionality on Acrylated Poly(caprolactone) for Stereolithography and Biomedical Applications

Authors: 
Brian J. Green, Kristan S. Worthington, Jessica R. Thompson, Spencer J. Bunn, Mary Rethwisch, Emily E. Kaalberg, Chunhua Jiao, Luke A. Wiley, Robert F. Mullins, Edwin M. Stone, Elliott H. Sohn, Budd A. Tucker, and C. Allan Guymon

Degradable polymers are integral components in many biomedical polymer applications. The ability of these materials to decompose in situ has become a critical component for tissue engineering, allowing scaffolds to guide cell and tissue growth while facilitating gradual regeneration of native tissue. The objective of this work is to understand the role of prepolymer molecular weight and functionality of photocurable poly(caprolactone) (PCL) in determining reaction kinetics, mechanical properties, polymer degradation, biocompatibility, and suitability for stereolithography. PCL, a degradable polymer used in a number of biomedical applications, was functionalized with acrylate groups to enable photopolymerization and 3D printing via stereolithography. PCL prepolymers with different molecular weight and functionality were studied to understand the role of molecular structure on reaction kinetics, mechanical properties and degradation rates. The mechanical properties of photocured PCL were dependent on cross-link density and directly related to the molecular weight and functionality of the prepolymers. High molecular weight, low functionality PCLDA prepolymers exhibited lower modulus and higher strain at break while low molecular weight, high functionality PCLTA prepolymers exhibited lower strain at break and higher modulus. Additionally, degradation profiles of cross-linked PCL followed a similar trend, with low cross-link density leading to degradation times up to 2.5 times shorter than more highly cross-linked polymers. Furthermore, photopolymerized PCL showed biocompatibility both in vitro and in vivo, causing no observed detrimental effects on seeded murine induced pluripotent stem cells or when implanted into pig retinas. Finally, the ability to create 3-dimensional PCL structures is shown by fabrication of simple structures using digital light projection stereolithography. Low molecular weight, high functionality PCLTA prepolymers printed objects with feature sizes near the hardware resolution limit of 50 μm. This work lays the foundation for future work in fabricating micro-scale PCL structures for a wide range of tissue regeneration applications.

Journal: 
Biomacromolecules
Publication Date: 
Mon, 09/10/2018
Pubmed ID: 
30044915