Thiol–Ene Photopolymerizations Provide a Facile Method To Encapsulate Proteins and Maintain Their Bioactivity

• Published in: Biomacromolecules 2012-08, Vol.13 (8), p.2410-2417
• Main Authors: McCall, Joshua D, Anseth, Kristi S
• Format: Article
• Language: English
• Subjects: Acrylates - chemistry; Applied sciences; Biological and medical sciences; Biotechnology; Click Chemistry; Cross-Linking Reagents - chemistry; Elastic Modulus; Enzyme Stability - radiation effects; Exact sciences and technology; Free Radicals - chemistry; Fundamental and applied biological sciences. Psychology; Hydrogels - chemical synthesis; Hydrogels - chemistry; Immobilization of enzymes and other molecules; Immobilization techniques; Methods. Procedures. Technologies; Muramidase - chemistry; Norbornanes - chemical synthesis; Norbornanes - chemistry; Physicochemistry of polymers; Polyethylene Glycols - chemical synthesis; Polyethylene Glycols - chemistry; Polymerization; Polymerization - radiation effects; Polymers and radiations; Rheology; Shear Strength; Sulfhydryl Compounds - chemistry
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm300671s

Photoinitiated polymerization remains a robust method for fabrication of hydrogels, as these reactions allow facile spatial and temporal control of gelation and high compatibility for encapsulation of cells and biologics. The chain-growth reaction of macromolecular monomers, such as acrylated PEG and hyaluronan, is commonly used to form hydrogels, but there is growing interest in step-growth photopolymerizations, such as the thiol–ene “click” reaction, as an alternative. Thiol–ene reactions are not susceptible to oxygen inhibition and rapidly form hydrogels using low initiator concentrations. In this work, we characterize the differences in recovery of bioactive proteins when exposed to similar photoinitiation conditions during thiol–ene versus acrylate polymerizations. Following exposure to chain polymerization of acrylates, lysozyme bioactivity was approximately 50%; after step-growth thiol–ene reaction, lysozyme retained nearly 100% of its prereaction activity. Bioactive protein recovery was enhanced 1000-fold in the presence of a thiol–ene reaction, relative to recovery from solutions containing identical primary radical concentrations, but without the thiol–ene components. When the cytokine TGFβ was encapsulated in PEG hydrogels formed via the thiol–ene reaction, full protein bioactivity was preserved.