title: Synthesis of photodegradable macromers for conjugation and release of bioactive molecules.
abstract: Hydrogel scaffolds are used in biomedicine to study cell differentiation and tissue evolution, where it is critical to control the delivery of chemical cues both spatially and temporally. While large molecules can be physically entrapped in a hydrogel, moderate molecular weight therapeutics must be tethered to the hydrogel network through a labile linkage to allow controlled release. We synthesized and characterized a library of polymerizable ortho-nitrobenzyl (o-NB) macromers with different functionalities at the benzylic position (alcohol, amine, BOC-amine, halide, acrylate, carboxylic acid, activated disulfide, N-hydroxysuccinyl ester, biotin). This library of polymerizable macromers containing o-NB groups should allow direct conjugation of nearly any type of therapeutic agent and its subsequent controlled photorelease from a hydrogel network. As proof-of-concept, we incorporated the N-hydroxysuccinyl ester macromer into hydrogels and then reacted phenylalanine with the NHS ester. Upon exposure to light (λ = 365 nm; 10 mW/cm(2), 10 min), 81.3% of the phenylalanine was released from the gel. Utilizing the photodegradable macromer incorporating an activated disulfide, we conjugated a cell-adhesive peptide (GCGYGRGDSPG), a protein that exhibits enzymatic activity (bovine serum albumin (BSA)), and a growth factor (transforming growth factor-β1 (TGF-β1)) into hydrogels, controlled their release with light (λ = 365 nm; 10 mW/cm(2), 0-20 min), and verified the bioactivity of the photoreleased molecules. The photoreleasable peptide allows real-time control over cell adhesion. BSA maintains full enzymatic activity upon sequestration and release from the hydrogel. Photoreleased TGF-β1 is able to induce chondrogenic differentiation of human mesenchymal stem cells comparable to native TGF-β1. Through this approach, we have demonstrated that photodegradable tethers can be used to sequester peptides and proteins into hydrogel depots and release them in an externally controlled, predictable manner without compromising biological function.
authors.affiliation: Department of Bioengineering, University of California, Los Angeles , 410 Westwood Plaza, 5121 Eng V, Los Angeles, California 90095, USA.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Griffin
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Schlosser
authors.forename: Sandra F
authors.initials: SF
authors.lastname: Lam
authors.forename: Thi H
authors.initials: TH
authors.lastname: Nguyen
authors.forename: Heather D
authors.initials: HD
authors.lastname: Maynard
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Kasko
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002448:Cell Adhesion / Q000187:drug effects*; D002454:Cell Differentiation; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004337:Drug Carriers / Q000138:chemical synthesis*; D006801:Humans; D020100:Hydrogels; D008027:Light; D059630:Mesenchymal Stem Cells / Q000187:drug effects* / Q000378:metabolism; D009578:Nitrobenzenes / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry; D010782:Photolysis; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1 / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001672:Biocompatible Materials; D004337:Drug Carriers; D020100:Hydrogels; D009578:Nitrobenzenes; D010455:Peptides; D053773:Transforming Growth Factor beta1; D012710:Serum Albumin, Bovine; D010649:Phenylalanine