Enzymatic Mineralization of Hydrogels for Bone Tissue Engineering by Incorporation of Alkaline Phosphatase

Abstract

Alkaline Phosphatase (ALP), an enzyme involved in mineralization of bone, was incorporated into three hydrogel biomaterials to induce their mineralization with calcium phosphate (CaP). These were collagen type I, a mussel protein-inspired adhesive consisting of PEG substituted with catechol groups, cPEG, and the PEG-fumaric acid copolymer OPF. After incubation in calcium glycerophosphate (Ca-GP) solution, FTIR, EDS, SEM, XRD, SAED, ICP-OES and von Kossa staining confirmed CaP formation. The amount of mineral formed decreased in the order cPEG > collagen > OPF. Mineral:polymer ratio decreased in the order collagen > cPEG > OPF. Mineralization increased Young’s modulus, most profoundly for cPEG. Such enzymatically mineralized hydrogel-CaP composites could find application as bone regeneration materials.

Introduction to cell–hydrogel mechanosensing

“…Mineralization by cells of tissues or constructs through the release of extracellular products has led to an increase in stiffness of the surrounding matrix [118,119]. Mineralization is a key requirement for bone tissue engineering and regeneration, and it may be achieved in hydrogels by copolymerization with specific functional groups via the addition of calcium and phosphate solutions or alkaline phosphatase, combining with acid peptides or though promotion of cellular osteogenic activity by the addition of growth factors or adhesion molecules [120][121][122][123][124]. In addition to mineralization, other extracellular matrix products may also affect the mechanical characteristics of the hydrogels.…”

Pulsed laser deposition of magnesium-doped calcium phosphate coatings on porous polycaprolactone scaffolds produced by rapid prototyping

“…Samples were coated with a thin gold layer as described previously [28]. EDS analysis was performed in the mapping mode.…”

Additive manufacturing of cell-loaded alginate enriched with alkaline phosphatase for bone tissue engineering application

“…During this period no obvious degradation was observed. ALP has been used to mineralize a range of natural and synthetic hydrogels with calciumphosphate Brought to you by | provisional account Unauthenticated Download Date | 6/11/15 8:08 AM [9][10][11][12][13]25]. However, there is a lack of studies in literature on the biological effects of ALP on cells encapsulated in hydrogels.…”

“…Hydrogel mineralization can be achieved by addition of enzymes such as alkaline phosphatase (ALP) [2], which causes mineralization of bone by cleavage of phosphate from organic phosphate, thereby increasing the local phosphate concentration and en abling precipitation of insoluble phosphate salts. ALP has been added to hydrogel materials to induce their mineralization with calcium phosphate (CaP) during incubation in solutions containing calcium and glycerophosphate (GP), which serves as a substrate for ALP [8][9][10][11][12][13][14].…”