Biomimetic Mineralization on 3D Printed PLA Scaffolds: On the Response of Human Primary Osteoblasts Spheroids and In Vivo Implantation.

Marianna O C Maia-Pinto,Bruna Nunes Teixeira,Ana Carolina B Brochado,Suelen C Sartoretto,Gutemberg G Alves,Rossana M S M Thiré,Marcelo J Uzeda,Adriana T N N Alves,Mônica D Calasans-Maia

doi:10.3390/polym13010074

Abstract

This study aimed to assess the response of 3D printed polylactic acid (PLA) scaffolds biomimetically coated with apatite on human primary osteoblast (HOb) spheroids and evaluate the biological response to its association with Bone Morphogenetic Protein 2 (rhBMP-2) in rat calvaria. PLA scaffolds were produced via 3D printing, soaked in simulated body fluid (SBF) solution to promote apatite deposition, and characterized by physical-chemical, morphological, and mechanical properties. PLA-CaP scaffolds with interconnected porous and mechanical properties suitable for bone repairing were produced with reproducibility. The in vitro biological response was assessed with human primary osteoblast spheroids. Increased cell adhesion and the rise of in vitro release of growth factors (Platelet-Derived Growth Factor (PDGF), Basic Fibroblast Growth Factor (bFGF), Vascular Endothelial Growth Factor (VEGF) was observed for PLA-CaP scaffolds, when pre-treated with fetal bovine serum (FBS). This pre-treatment with FBS was done in a way to enhance the adsorption of serum proteins, increasing the number of bioactive sites on the surface of scaffolds, and to partially mimic in vivo interactions. The in vivo analysis was conducted through the implantation of 3D printed PLA scaffolds either alone, coated with apatite (PLA-CaP) or PLA-CaP loaded with rhBMP-2 on critical-sized defects (8 mm) of rat calvaria. PLA-CaP+rhBMP2 presented higher values of newly formed bone (NFB) than other groups at all in vivo experimental periods (p < 0.05), attaining 44.85% of NFB after six months. These findings indicated two new potential candidates as alternatives to autogenous bone grafts for long-term treatment: (i) 3D-printed PLA-CaP scaffold associated with spheroids, since it can reduce the time of repair in situ by expression of biomolecules and growth factors; and (ii) 3D-printed PLA-CaP functionalized rhBMP2 scaffold, a biocompatible, bioactive biomaterial, with osteoconductivity and osteoinductivity.

Highlights

Bone healing is a complex physiological process of reconstructing bone tissue that depends on the type and extent of the injury and patient’s age and gender [1,2]
The pore volume for each was in the same range and indicated that calcium phosphate (CaP) coating does not interfere with the scaffold architecture (Table 1)
The present results shown that the 3D polylactic acid (PLA)-CaP scaffolds can effectively load recombinant human bone morphogenetic protein-2 (rhBMP-2), according to the levels detected by Enzyme-Linked Immunosorbent Assay (ELISA), maintaining similar concentrations to those found on the absorbable collagen sponges (ACS) that comes in the INFUSE® kit [90]

Summary

Introduction

Bone healing is a complex physiological process of reconstructing bone tissue that depends on the type and extent of the injury and patient’s age and gender [1,2]. The body can follow two routes for repair: healing and regeneration. Healing corresponds to fibrous accumulation in the injured area, with scar formation and loss of tissue function. Regeneration produces a new tissue without loss of function. In cases where the body cannot repair the injury by itself, some known clinical strategies are available, including the use of biomaterials, even though significant limitations affect the choice for treatment [3]. Autografts, where bone tissue is taken from the patient, allografts (bone harvested from cadavers), and xenografts (bone taken from another species) present potential risk of contamination, limited available quantities, and undesired immune response [4,5,6,7]

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