3D bioprinting of methacrylated hyaluronic acid (MeHA) hydrogel with intrinsic osteogenicity

Abstract

In bone regenerative medicine there is a need for suitable bone substitutes. Hydrogels have excellent biocompatible and biodegradable characteristics, but their visco-elastic properties limit their applicability, especially with respect to 3D bioprinting. In this study, we modified the naturally occurring extracellular matrix glycosaminoglycan hyaluronic acid (HA), in order to yield photo-crosslinkable hydrogels with increased mechanical stiffness and long-term stability, and with minimal decrease in cytocompatibility. Application of these tailor-made methacrylated hyaluronic acid (MeHA) gels for bone tissue engineering and 3D bioprinting was the subject of investigation. Visco-elastic properties of MeHA gels, measured by rheology and dynamic mechanical analysis, showed that irradiation of the hydrogels with UV light led to increased storage moduli and elastic moduli, indicating increasing gel rigidity. Subsequently, human bone marrow derived mesenchymal stromal cells (MSCs) were incorporated into MeHA hydrogels, and cell viability remained 64.4% after 21 days of culture. Osteogenic differentiation of MSCs occurred spontaneously in hydrogels with high concentrations of MeHA polymer, in absence of additional osteogenic stimuli. Addition of bone morphogenetic protein-2 (BMP-2) to the culture medium further increased osteogenic differentiation, as evidenced by increased matrix mineralisation. MeHA hydrogels demonstrated to be suitable for 3D bioprinting, and were printed into porous and anatomically shaped scaffolds. Taken together, photosensitive MeHA-based hydrogels fulfilled our criteria for cellular bioprinted bone constructs within a narrow window of concentration.

Recent Advances in Photo-Crosslinkable Hydrogels for Biomedical Applications

“…Finally, the MeHA pre-polymers are produced by freeze-drying the dialyzed solution. These pre-polymers (0.25 to 4.0) (w/v) can be used to fabricate MeHA hydrogel constructs in the presence of UV light and Irgacure 2959 through various microfabrication strategies (e.g.,electrospinning, micromolding and bioprinting) [105,106]. Similar to GelMA hydrogel, the mechanical properties of MeHA hydrogel can be tuned by varying the pre-polymer concentration or light exposure duration [106,107].…”

“…These pre-polymers (0.25 to 4.0) (w/v) can be used to fabricate MeHA hydrogel constructs in the presence of UV light and Irgacure 2959 through various microfabrication strategies (e.g.,electrospinning, micromolding and bioprinting) [105,106]. Similar to GelMA hydrogel, the mechanical properties of MeHA hydrogel can be tuned by varying the pre-polymer concentration or light exposure duration [106,107]. For instance, elastic modulus of MeHA hydrogel was increased from 1.3 to 10.6kPa when the pre-polymer concentration was increased from 1 to 3 (w/v) [106] (Table 3).…”

“…Similar to GelMA hydrogel, the mechanical properties of MeHA hydrogel can be tuned by varying the pre-polymer concentration or light exposure duration [106,107]. For instance, elastic modulus of MeHA hydrogel was increased from 1.3 to 10.6kPa when the pre-polymer concentration was increased from 1 to 3 (w/v) [106] (Table 3). Besides mechanical properties, the degradation rate of MeHA hydrogel can be adjusted by varying its pre-polymer concentration.…”

“…Besides mechanical properties, the degradation rate of MeHA hydrogel can be adjusted by varying its pre-polymer concentration. When the pre-polymer concentration was increased from 1 to 3, enzymatic degradation of MeHA hydrogel was decreased from 100 to 50 after 1day of incubation in hyaluronidase solution [106]. High degradability of MeHA hydrogel is imperative for cell remodeling in 3D tissue-engineered constructs [103].…”

“…MeHA hydrogels have also been used to generate tissue engineered cartilage- and bone-like tissue constructs for cartilage and bone regeneration, respectively [104,106]. To further improve biofunctionality of MeHA hydrogel, incorporating other organic or inorganic components into it can enhance its mechanical and chemical properties.…”