Biomimetic modification of synthetic hydrogels by incorporation of adhesive peptides and calcium phosphate nanoparticles: in vitro evaluation of cell behavior

Abstract

The ultimate goal of this work was to develop a biocompatible and biomimetic in situ crosslinkable hydrogel scaffold with an instructive capacity for bone regenerative treatment. To this end, synthetic hydrogels were functionalized with two key components of the extracellular matrix of native bone tissue, i.e. the three-amino acid peptide sequence RGD (which is the principal integrin-binding domain responsible for cell adhesion and survival of anchorage-dependent cells) and calcium phosphate (CaP) nanoparticles in the form of hydroxyapatite (which are similar to the inorganic phase of bone tissue). Rat bone marrow osteoblast-like cells (OBLCs) were encapsulated in four different biomaterials (plain oligo(poly(ethylene glycol) fumarate) (OPF), RGDmodifi ed OPF, OPF enriched with CaP nanoparticles and RGD-modifi ed OPF enriched with CaP nanoparticles) and cell survival, cell spreading, proliferation and mineralized matrix formation were determined via cell viability assay, histology and biochemical analysis for alkaline phosphatase activity and calcium. This study showed that RGD peptide sequences promoted cell spreading in OPF hydrogels and hence play a crucial role in cell survival during the early stage of culture, whereas CaP nanoparticles signifi cantly enhanced cell-mediated hydrogel mineralization. Although cell spreading and proliferation activity were inhibited, the combined effect of RGD peptide sequences and CaP nanoparticles within OPF hydrogel systems elicited a better biological response than that of the individual components. Specifi cally, both a sustained cell viability and mineralized matrix production mediated by encapsulated OBLCs were observed within these novel biomimetic composite systems.

Subcutaneous tissue response and osteogenic performance of calcium phosphate nanoparticle-enriched hydrogels in the tibial medullary cavity of guinea pigs

“…In order to mimic the physiological condition, H 3 PO 4 (3.56 M) and Ca(OH) 2 (5.92 M) were prepared in PBS, and the precursors compounds were used at a stoichiometric Ca/P ratio of 1.67 to obtain a final solid content of ~ 0.3 g/ml (30% w/v). This method resulted in stable needle-shaped hydroxyapatite nanoparticles with an average length of 76 nm and a diameter of 19 nm, and minor traces of monetite as a secondary CaP phase, as confirmed by XRD and TEM [16].…”

“…Differently, the dense structure of OPF-CaP scaffolds was maintained by both the presence of homogeneously distributed CaP nanoparticles throughout the polymeric matrix and reduced water content (approximately two times less than OPF hydrogels [16,29].…”

“…A homogeneous suspension of nano-sized calcium phosphate (CaP) particles was prepared according to a wet-chemical precipitation process as previously described [16]. In order to mimic the physiological condition, H 3 PO 4 (3.56 M) and Ca(OH) 2 (5.92 M) were prepared in PBS, and the precursors compounds were used at a stoichiometric Ca/P ratio of 1.67 to obtain a final solid content of ~ 0.3 g/ml (30% w/v).…”

“…Recently, we showed that CaP nanoparticle-enriched OPF hydrogels also have a stimulatory effect on mineralized matrix production by encapsulated rat osteoblast-like stem cells (OBLCs) in vitro [16]. This advantage of OPF-CaP hydrogels suggests their potential for application as a bone substitute material.…”

Biological responses to nanomaterials: understanding nano-bio effects on cell behaviors

“…Composite materials can take advantage of the properties of all used compounds, and the content and the ratio of the components can be adjusted to mimic natural bone properties. Bongio et al (2011) developed in situ crosslinkable hydrogel scaffolds by oligo poly(ethylene glycol) fumarate (OPF) and functionalized the synthetic hydrogels (Kumar et al, 2015). Reprinted with permission from Kumar et al (2015).…”