Biomimetic hydroxyapatite coating on pore walls improves osteointegration of poly(L‐lactic acid) scaffolds

Abstract

Polymer-ceramic composites obtained as the result of a mineralization process hold great promise for the future of tissue engineering. Simulated body fluids (SBFs) are widely used for the mineralization of polymer scaffolds. In this work an exhaustive study with the aim of optimizing the mineralization process on a poly(L-lactic acid) (PLLA) macroporous scaffold has been performed. We observed that when an air plasma treatment is applied to the PLLA scaffold its hydroxyapatite nucleation ability is considerably improved. However, plasma treatment only allows apatite deposition on the surface of the scaffold but not in its interior. When a 5 wt % of synthetic hydroxyapatite (HAp) nanoparticles is mixed with PLLA a more abundant biomimetic hydroxyapatite layer grows inside the scaffold in SBF. The morphology, amount, and composition of the generated biomimetic hydroxyapatite layer on the pores' surface have been analyzed. Large mineralization times are harmful to pure PLLA as it rapidly degrades and its elastic compression modulus significantly decreases. Degradation is retarded in the composite scaffolds because of the faster and extensive biomimetic apatite deposition and the role of HAp to control the pH. Mineralized scaffolds, covered by an apatite layer in SBF, were implanted in osteochondral lesions performed in the medial femoral condyle of healthy sheep. We observed that the presence of biomimetic hydroxyapatite on the pore's surface of the composite scaffold produces a better integration in the subchondral bone, in comparison to bare PLLA scaffolds.

An “in vitro” experimental model to predict the mechanical behavior of macroporous scaffolds implanted in articular cartilage

“…The micropores are approximately 10 µm and result from the dissolution of dioxane crystals formed in the freeze extraction process (Figure 1a). The microstructure is similar to that obtained in previous works [8][9][10][11][12]. Figure 1b shows the PCL scaffold filled with the PVA gel after 6 cycles of freezing and thawing.…”

“…This group has previously proposed a procedure to produce PCL or Polylactide scaffolds that combines freeze extraction and the use of porogen microparticles [8][9][10][11][12]. These scaffolds will have a pore architecture characterized by large interconnected spherical pores with microporous pore walls.…”

An experimental fatigue study of a porous scaffold for the regeneration of articular cartilage

“…These mean pores size were obtained by measuring the size of 10 micro and macro pores in 3 different SEM photos. The structure is similar to the ones obtained in previous works (Santamaría et al 2012) (Lebourg, Suay Antón, and Gómez Ribelles 2010) (Deplaine et al 2013) . Without fatigue, the structure of the dry and immersed scaffold is very similar.…”

Structural, mechanical and in vitro studies on pulsed laser deposition of hydroxyapatite on additive manufactured polyamide substrate

“…Coating with HA can be done by many techniques with desired features like surface chemistry, energy, roughness, morphology and crystallinity [26−28] , which influences the cellular response to biomaterials. Techniques like plasma spraying [29] , flame spraying [30] , ion-beam process [31] , electrophoretic deposition [32] , radio frequency sputtering [33] , biomimetic coating [34] and a combination of these techniques are commonly used. However, these techniques are unable to fulfil the necessary features for enhanced cell growth [35] , but pulsed laser deposition (PLD) yields almost high quality HA coating with uniform and dense layer and high adhesion to the substrate [36,37] .…”