Using Mass Spectrometry to Investigate the Structural Features of Photocrosslinked Co-Networks based on Gelatin and Poly
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Using Mass Spectrometry to Investigate the Structural Features of Photocrosslinked Co-Networks based on Gelatin and Poly(ethylene glycol) Methacrylates Benjamin F. Pierce, Axel T. Neffe, and Andreas Lendlein Center for Biomaterial Development and Berlin-Brandenburg Center for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Kantstr. 55, 14513 Teltow, Germany ABSTRACT Gelatin was functionalized with glycidyl methacrylate and photocrosslinked in the presence of poly(ethylene glycol) dimethacrylate (PEGDMA) or poly(ethylene glycol) monomethacrylate (PEGMA) to create a biopolymer-based system with tailorable properties. These co-networks were hydrolyzed using 6 M HCl and the degradation products were analyzed and identified using matrix-assisted laser desorption/ionizationtime of flight (MALDI-TOF) mass spectrometry. This technique successfully identified gelatin-derived peptides such as FLPEPPE, SFLPEPPE, and SFLPEPPEE as well as an accompanying PEG-g-poly(methacrylic acid) component. No oligo- or polymethacrylates were monitored at any molecular weight range above m/z = 500, which indicated that they possessed lower molecular weights. An in vitro hydrolytic degradation experiment performed in pH 7.4 PBS buffer solution at 37 °C showed that these networks, which were prepared without the addition of a potentially toxic photoinitiator, exhibited mass loss of up to 50 wt% at 6 weeks of incubation time. These results provide valuable insight into how these functional gelatin-based co-network biomaterials will perform in a biological setting. INTRODUCTION Biopolymer-based biomaterials are of high interest for biomaterial-induced autoregeneration of tissue because they can perform key functions, which are usually carried out by the extracellular matrix (ECM). Gelatin is an excellent building block for such biomaterials because it is non-immunogenic, pro-angiogenic, and degradable [1-2]. Gelatin may be chemically crosslinked with small bifunctional crosslinkers to form hydrogels with mechanical properties dictated by the crosslinking density rather than the triple helical content [3,4], physically crosslinked via tyrosine-derived aromatic moieties to form processable gels based on supramolecular interactions [5-7], or functionalized with photochemically crosslinkable groups to enable an injectable gelatin-based solution that may be crosslinked using laser irradiation [8]. Previously, we have reported a biopolymer-based system based on gelatin functionalized with glycidyl methacrylate, which was photopolymerized in the presence of varying amounts of oligomeric poly(ethylene glycol) dimethacrylate (PEGDMA, Mn = 550 g·mol-1) and poly(ethylene glycol) methacrylate (PEGMA, Mn = 285 g·mol-1) without the addition of a potentially toxic photoinitiator. Tailorable mechanical properties were observed in this class of gelatin-based hydrogels (G’ = 0.7-145 kPa), while the amounts of triple helices were
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minimized ( 800 (m/z = 807.551, 849.624, 936.581, 978.563, and 1065.486), which were evident
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