Immobilization of a phosphonated analog of matrix phosphoproteins within cross-linked collagen as a templating mechanism for biomimetic mineralization

Abstract

Immobilization of phosphoproteins on a collagen matrix is important for induction of intrafibrillar apatite mineralization. Unlike phosphate esters, polyphosphonic acid has no reactive sites for covalent binding to collagen amine groups. Binding of polyvinylphosphonic acid (PVPA), a biomimetic templating analog of matrix phosphoproteins, to collagen was found to be electrostatic in nature. Thus, an alternative retention mechanism was designed for immobilization of PVPA to collagen by cross-linking the latter with carbodiimide (EDC). This mechanism is based on the principle of size exclusion entrapment of PVPA molecules within the internal water compartments of collagen. By cross-linking collagen with EDC, a zero-length cross-linking agent, the sieving property of collagen is increased, enabling the PVPA to be immobilized within the collagen. Absence of covalent cross-linking between PVPA and collagen was confirmed by FT-IR spectroscopy. Based on these results, a concentration range for immobilized PVPA to template intrafibrillar apatite deposition was established and validated using a single-layer reconstituted type I collagen mineralization model. In the presence of a polyacrylic acid-containing mineralization medium, optimal intrafibrillar mineralization of the EDC-cross-linked collagen was achieved using 500 and 1,000 μg/mL PVPA. The mineralized fibrils exhibited a hierarchical order of intrafibrillar mineral infiltration, as manifested by the appearance of electron-dense periodicity within unstained fibrils. Understanding the basic processes in intrafibrillar mineralization of reconstituted collagen creates opportunities for the design of tissue engineering materials for hard tissue repair and regeneration.

Mechanisms of degradation of the hybrid layer in adhesive dentistry and therapeutic agents to improve bond durability—A literature review

“…Similar to CHX, PVPA binds electrostatically to collagen. However, its use as a potential MMP inhibitor in dentin bonding may be more advantageous than CHX in that PVPA can be trapped in collagen matrices via the use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) [101]. These results suggest that the use of PVPA could enhance the longevity of the dentin-resin bonds.…”

Zinc Induces Apatite and Scholzite Formation during Dentin Remineralization

“…It seems that phosphorylated extracellular proteins play critical roles in the formation of collagenous mineralized tissues and in the regulation of biomineralization [Deshpande et al, 2011]. However, it has been shown that phosphoproteins are non-specific and may be substituted by other immobilized, naturally occurring phosphoproteins to induce apatite deposition within collagen [Gu et al, 2010]. Phosphorylation of dentin collagen has previously been shown to cause a significant surface remineralization of demineralized dentin [Saito et al, 1998;Bertassoni et al, 2011].…”

Hierarchical Structures of Bone and Bioinspired Bone Tissue Engineering

“…[ 91,92,135,147,148 ] Polycarboxylic acids such as polyacrylic acid (PAA) or polyaspartic acid were employed as biomimetic NCP analogs for binding and sequestering calcium ions to prevent aggregation of fl uidic ACP nanoparticles and auto-transformation of the ACP nanoparticles into apatite before they enter into the intrafibrillar water compartments of the collagen fi bril. Additionally, polyphosphates including polyvinylphosphonic acid, small 2016, DOI: 10.1002/smll.201600626 Figure 10 .…”