title: Rheological characterization of polysaccharide-poly(ethylene glycol) star copolymer hydrogels.
abstract: Binding interactions between low molecular weight heparin (LMWH) and heparin-binding peptides (HBP) have been applied as a strategy for the assembly of hydrogels that are capable of sequestering growth factors and delivering them in a controlled manner. In this work, the assembly of four-arm star poly(ethylene glycol) (PEG)-LMWH conjugate with PEG-HBP conjugates has been investigated. The interactions between LMWH and the heparin-binding regions of antithrombin III (ATIII) or the heparin interacting protein (HIP) have been characterized via heparin affinity chromatography and surface plasmon resonance (SPR); results indicate that the two peptides have slightly different affinities for heparin and LMWH, and bind LMWH with micromolar affinity. Solutions of the PEG-LMWH and of mixtures of the PEG-LMWH and PEG-HBP were characterized via both bulk rheology and laser tweezer microrheology. Interestingly, solutions of PEG-LMWH (2.5 wt % in PBS) form hydrogels in the absence of PEG-ATIII or PEG-HIP, with storage moduli, determined via bulk rheological measurements, in excess of the loss moduli over frequencies of 0.1-100 Hz. The addition of PEG-ATIII or PEG-HIP increases the moduli in direct proportion to the number of cross-links introduced. Characterization of the hydrogels via microrheology shows the gel microstructure is composed of polymer-rich fibrillar structures surrounded by polymer-depleted buffer. Potential applications of these hydrogels are discussed.
authors: Department of Materials Science and Engineering, Delaware Biotechnology Institute, University of Delaware, Newark, Delaware 19716, USA.
authors: Nori
authors: N
authors: Yamaguchi
authors: Byeong-Seok
authors: BS
authors: Chae
authors: Le
authors: L
authors: Zhang
authors: Kristi L
authors: KL
authors: Kiick
authors: Eric M
authors: EM
authors: Furst
mesh_terms: D000595:Amino Acid Sequence; D002846:Chromatography, Affinity; D006493:Heparin / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry*; D008969:Molecular Sequence Data; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*; D012212:Rheology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D020349:Surface Plasmon Resonance
chemical_list: D020100:Hydrogels; D011108:Polymers; D011134:Polysaccharides; D011092:Polyethylene Glycols; D006493:Heparin