Mimicking the Nanostructure of Bone: Comparison of Polymeric Process-Directing Agents

Abstract

The nanostructure of bone has been replicated using a polymer-induced liquid-precursor (PILP) mineralization process. This polymer-mediated crystallization process yields intrafibrillar mineralization of collagen with uniaxially-oriented hydroxyapatite crystals. The process-directing agent, an anionic polymer which we propose mimics the acidic non-collagenous proteins associated with bone formation, sequesters calcium and phosphate ions to form amorphous precursor droplets that can infiltrate the interstices of collagen fibrils. In search of a polymeric agent that produces the highest mineral content in the shortest time, we have studied the influence of various acidic polymers on the in vitro mineralization of collagen scaffolds via the PILP process. Among the polymers investigated were poly-L aspartic acid (PASP), poly-L-glutamic acid (PGLU), polyvinylphosphonic acid (PVPA), and polyacrylic acid (PAA). Our data indicate that PASP and the combination of PGLU/PASP formed stable mineralization solutions, and yielded nano-structured composites with the highest mineral content. Such studies contribute to our goal of preparing biomimetic bone graft substitutes with composition and structure that mimic bone.

Synergistic intrafibrillar/extrafibrillar mineralization of collagen scaffolds based on a biomimetic strategy to promote the regeneration of bone defects

“…The biomimetic mineralization through this process is called intrafibrillar mineralization. 8,9,14,[25][26][27] In contrast to the classical crystallization pathways, the nonclassical crystallization route involves mesoscopic transformations of self-assembled, metastable, or amorphous precursor particles into nanoparticulate superstructures. 28,29 Because this process assembles materials from the nanoscopic scale to large sizes, it is also called the bottom-up strategy.…”

“…[35][36][37][38] The minor phase formed in this process is composed of metastable, amorphous, liquid-phase nanodroplets, which are the precursors of ACP. 25 It has been proposed that these precursors can be drawn into the interstices of the collagen fibrils by capillary forces of fluidic nature. Subsequently, due to the transformation of ACP to HA, collagen fibrils are embedded with HA nanocrystals similar to the natural bone structure.…”

Water-Soluble Cellulose Derivatives Are Sustainable Additives for Biomimetic Calcium Phosphate Mineralization

“…Yamane, et al showed that cholesterol-bearing pullulan and mannan nanogels favor the formation of amorphous calcium phosphate (ACP) or HAP, depending on the calcium precursor concentration initially present in the reaction mixture [19]. Dogan and Öner [20] and Thula, et al [21] found strong effects of carboxylmethyl inulin (CMI), a biodegradable and non-toxic polysaccharide-based polycarboxylate, on the nucleation and growth of HAP.…”

Synthesis, characterization, and application of nano hydroxyapatite and nanocomposite of hydroxyapatite with granular activated carbon for the removal of Pb2+ from aqueous solutions

“…Ability of HAp to remove cations such as cadmium [22], lead [22][23], copper [22], zinc [24], magnesium [24], strontium [23], lanthanum, Europium [25],vanadium [26], iron and anions carbonate and fluoride [27] are well recognized and many mechanisms have been suggested for its action. Hydroxyapatite nanocrystals can be synthesized via numerous synthetic routes, using a range of different reactants, such as Wet chemical methods precipitation [28][29][30][31][32][33] Sol Gel method [34][35][36][37] hydrothermal techniques [38][39][40][41][42] biomimetic deposition [35,[43][44] and electro deposition [45]. As far as the synthesis of HAp is concerned the properties of the final product is highly variable depending on the method of synthesis [38] .…”