Innovative macroporous granules of nanostructured‐hydroxyapatite agglomerates: Bioactivity and osteoblast‐like cell behaviour

Abstract

To modulate the biological response of implantable granules, two types of bioactive porous granules composed of nanostructured-hydroxyapatite (HA) agglomerates and microstructured-HA, respectively, were prepared using a polyurethane sponge impregnation and burnout method. The resulting granules presented a highly porous structure with interconnected porosity. Both types of granules were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry. Results showed that nanostructed-HA granules presented higher surface area and porosity than microstructured-HA granules. In vitro testing using MG63 human osteoblast-like cells showed that on both types of surfaces cells were able to adhere, proliferate, and migrate through the macropores, and a higher growth rate was achieved on nanostructured-HA granules than on microstructured-HA granules (76 and 40%, respectively). In addition, these cells maintained similar expression levels of osteoblastic-associated markers namely collagen type I, alkaline phosphatase, bone morphogenetic protein-2, macrophage colony-stimulating factor, and osteoprotegerin. These innovative nanostructured-HA granules may be considered as promising bioceramic alternative matrixes for bone regeneration and drug release application.

Heparinized nanohydroxyapatite/collagen granules for controlled release of vancomycin

“…Scaffolds were prepared using polyurethane sponge impregnation method described elsewhere. 9 Briefly, polyurethane sponges (Recticel, Belgium) were impregnated with nanoHA slurry. 9 The slurry was prepared using a ratio of 5:4.4:0.2, respectively, of nanoHA powder (g), ultrapure water (mL), and dispersive agent Dolapix CE64 (mL) (Zschimmer & Schwarz, Germany).…”

“…9 Briefly, polyurethane sponges (Recticel, Belgium) were impregnated with nanoHA slurry. 9 The slurry was prepared using a ratio of 5:4.4:0.2, respectively, of nanoHA powder (g), ultrapure water (mL), and dispersive agent Dolapix CE64 (mL) (Zschimmer & Schwarz, Germany). The nanoHA is a highly pure spray-dried powder with an average particle size of 5.0 6 1.0 mm, nanoXIMÁHAp202 (Fluidinova SA, Portugal), being composed by highly crystalline nanoparticles aggregates, as confirmed by high-resolution transmission electron microscopy ( Fig.…”

“…When compared with micro-sized HA, nanoHA shows improved performance, because of large surface-to-volume ratio and higher surface reactivity. 9 In fact, nanoHA has properties that can control protein adsorption such as grain size, pore size, and wettability. 10 Moreover, nanoHA also enhances osteoblast functions like cell proliferation, calcium-containing mineral deposition, and alkaline phosphatase synthesis.…”

“…NanoHA has already been studied as a potential material for drug-delivery systems, namely with vancomycin. 3,11 Among the numerous forms of HA available for clinical applications, porous granules are more advantageous in cases of bone defects or hollows of irregular shapes, 9 as it happens in patients with osteomyelitis. 1 Type I collagen is a natural polymer present in bone 12 that has been increasingly used in tissue engineering and repair.…”

“…The crosslinked collagen sample has a broad band at 3200-3600 cm 21 , indicating the presence of adsorbed water on the material. 9 For the heparinized nanoHA/collagen granules, there was no novel S. aureus ATCC 25923 was used to create a 1.5 3 10 8 CFU/ mL suspension in 0.9% NaCl, which equals to 0.5 Mcfarland equivalence turbidity standard in ambient light, using a densitometer (BioMerieux, France). To allow bacterial adhesion to granules, 20 mg of granules were placed in a glass tube with 1 mL of bacterial suspension and incubated in a gently shaking water bath at 37 C for 1 h. The experiment was performed in triplicate.…”