Enhanced in Vitro Mineralization and in Vivo Osteogenesis of Composite Scaffolds through Controlled Surface Grafting of l-Lactic Acid Oligomer on Nanohydroxyapatite

Abstract

Nanocomposite of hydroxyapatite (HA) surface grafted with L-lactic acid oligomer (LAc oligomer) (op-HA) showed improved interface compatibility, mechanical property, and biocompatibility in our previous study. In this paper, composite scaffolds of op-HA with controlled grafting different amounts of LAc oligomer (1.1, 5.2, and 9.1 wt %) were fabricated and implanted to repair rabbit radius defects. The dispersion of op-HA nanoparticles was more uniform than n-HA in chloroform and nanocomposites scaffold. Calcium and phosphorus exposure, in vitro biomineralization ability, and cell proliferation were much higher in the op-HA1.1 wt %/PLGA scaffolds than the other groups. The osteodifferentiation and bone fusion in animal tests were significantly enhanced for op-HA5.2 wt %/PLGA scaffolds. The results indicated that the grafted LAc oligomer of 5.2 or 9.1 wt %, which formed a barrier layer on the HA surface, prevented the exposure of nucleation sites. The shielded nucleation sites of op-HA particles (5.2 wt %) might be easily exposed as the grafted LAc oligomer was decomposed easily by enzyme systems in vivo. Findings from this study have revealed that grafting 1.1 wt % amount of LAc oligomer on hydroxyapatite could improve in vitro mineralization, and 5.2 wt % could promote in vivo osteogenesis capacity of composite scaffolds.

In Vitro and in Vivo Study of Poly(Lactic–co–Glycolic) (PLGA) Membranes Treated with Oxygen Plasma and Coated with Nanostructured Hydroxyapatite Ultrathin Films for Guided Bone Regeneration Processes

“…Our results agree with those of other previously published studies, where they even observed the formation of new cortex and recanalisation of the marrow cavity via inspection [15].…”

“…In particular, the broad absorbance band at 1031-1042 cm −1 corresponding to the (υ 3 ) asymmetric vibration lines of (PO 4 ) 3− group indicates an amorphous Ca-P structure [34]. Moreover, the study of the HA surface chemical composition by means of X-ray photoelectron spectroscopy ( Figure 7) enables identification of the typical chemical states of the components in Polymers 2017, 9, 410 8 of 15 an ideal hydroxyapatite surface. Also, the estimated Ca/P ratio of 1.34 (see Table 1 with the atomic composition percentages) is in good agreement with other quasi-stoichiometric HA structures obtained by magnetron sputtering techniques in an inert atmosphere [35].…”

“…Furthermore, medical products such as screws, plates and cylinders made of this material have been shown to form a natural bond with the bone in vivo [14]. Therefore, including HA within a biomaterial may allow us to regulate its pH, preventing inflammatory reactions and inducing bone formation [15].…”

Resorbable nanocomposites with bone-like strength and enhanced cellular activity

“…33–38 Grafting organic molecules to the surface of ceramic nanoparticles enhances their dispersion in organic polymers as well as interfacial binding between the polymer and ceramic phases, resulting in improved mechanical properties and stimulation of cell attachment, proliferation, and differentiation. 37,39–45 However, the effects of surface grafting on mechanical and biological properties of reactive and settable nHA/polymer composite cements have not been investigated. Furthermore, studies investigating grafting of polyisocyanates to nHA have utilized solvents such as dimethyl formamide (DMF), which are cytotoxic and not suitable for injectable biomaterials.…”

Tissue-engineered composite scaffold of poly(lactide-co-glycolide) and hydroxyapatite nanoparticles seeded with autologous mesenchymal stem cells for bone regeneration

“…The new bone formation was guided by the scaffold of g-HA/PLGA. There were few fibrous tissues at the interface of the implant and new bones compared to the cell-free scaffold of g-HA/PLGA, which was reported by Wang et al (2016).…”