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/cm2, 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/cm2, 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.

Microstructured dextran hydrogels for burst-free sustained release of PEGylated protein drugs

“…Although burst release can be reduced to some extent, raising the degree of crosslinking often causes incomplete release via the permanent entrapment of proteins in regions of the hydrogel where the mesh size is smaller than the size of the protein drug [21]. Alternatively, burst release can be suppressed by tethering protein drugs to the hydrogels via a cleavable linker [22,23], or by incorporating protein-loaded poly(lactic-co-glycolic acid) micro/nanospheres in a bulk hydrogel matrix [24,25].…”

Photodegradable Gelatin-Based Hydrogels Prepared by Bioorthogonal Click Chemistry for Cell Encapsulation and Release

“…1 To address this problem, light-induced degradation chemistry has been utilized for spatial and temporal degradation of hydrogel structures. 7,11,18,[29][30][31][32][33][34][35][36][37][38][39][40][41] This approach often utilizes a photolabile o-nitrobenzyl (NB) moiety which becomes reactive upon irradiation with ultraviolet (UV) light and induces the cleavage of the adjacent group.…”

Photo-responsive polymeric micelles and prodrugs: synthesis and characterization

“…5-Hydroxy-2-nitrobenzyl alcohol, a difunctional initiator, which contains two hydroxyl groups, namely benzyl and phenolic hydroxyl groups, was used as a photoresponsive molecule because of its chemical stability and rapid cleavage in response to near-UV irradiation (wavelength > 320 nm). 27,28 Being more nucleophilic than the phenolic hydroxyl group, the benzyl hydroxyl group initiated the ROP of aClCL catalyzed by SnOct 2 . The HONB-P(aClCL) n polymers with various P(aClCL) n lengths were obtained by varying the molar ratio of HONB to aClCL.…”