Compressive strengths of PEG gels with glycerol and bioglass particles
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Compressive strengths of PEG gels with glycerol and bioglass particles Ariel Golshan1, Jenesis A. Curtis2, Vasilios Lianos2, Sina Y. Rabbany3, Roche C. de Guzman3,a) 1
Department of Engineering, Hofstra University, Hempstead, New York 11549, USA Department of Biology, Hofstra University, Hempstead, New York 11549, USA 3 Bioengineering Program, Department of Engineering, Hofstra University, Hempstead, New York 11549, USA a) Address all correspondence to this author. e-mail: [email protected] 2
Received: 10 August 2018; accepted: 24 January 2019
Poly(ethylene glycol) (PEG)-based materials can potentially be used as biomechanical matrices in regenerative medicine and tissue engineering implants including the replacement of intervertebral (IV) disks. Glycerol and other generally recognized as safe (GRAS) plasticizers (low-MW PEG, propylene glycol, and sorbitol) were added to the bulk PEG matrix and gelled using chemical and photochemical methods at different temperatures (21, 37, 59, and 80 °C) and pressures (0 and 90 MPa gauge) settings, and their compression testing properties were acquired and analyzed. Surface incorporation of custom-made bioactive glass particles shortened the blood clotting time (78% compared to no glass particles), while alginate and laponite additives improved the gel’s mechanical properties to 645 kPa compressive modulus, 12% yield strain, and 79 kPa yield strength. This IV disk-modeled hydrogel system endured the cyclic loading and unloading tests at 4% compressive strain indicative of an elastic response, but required improvement to its biomechanical tolerance for downstream bioengineering applications.
Introduction Poly(ethylene glycol) (PEG) is a commonly used biomaterial due to its proven safety record, nontoxicity, and biocompatibility [1, 2, 3, 4, 5]. However, as tissue engineering materials specifically for intervertebral (IV) disk applications, PEG hydrogels alone are not sufficient due to their inherent fragility [6, 7, 8, 9]. Plasticizers are low-molecularweight (MW) compounds that increase the flexibility of polymers by filling up the network spaces, allowing increased polymer mobility [10, 11, 12]. In this study, to improve the compressive strengths and other important mechanical properties of PEG hydrogels, U.S. Food and Drug Administration (FDA)’s generally recognized as safe (GRAS) substances: glycerol (glycerin), propylene glycol, and sorbitol, and relatively low-MW uncrosslinked PEG were utilized as plasticizers (Table I). The crosslinking process of the bulk PEG matrix was conducted using PEG diacrylate (PEGDA) chain intermediates, and the effect of chemical versus photochemical PEGDA chain elongation
ª Materials Research Society 2019
leading to gelation was also investigated at various temperature and pressure conditions, as they (type of crosslinkers, temperature, and pressure) affect the physical properties of gels [13, 14, 15, 16, 17]. Alginate (ALG) biomaterials, the naturally derived polysaccharides that gel via chain interactions linked by multivalent cat
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