The “Forgotten” Hydroxyapatite Crystals in Regenerative Bone Tissue Engineering: A Critical Review
Anastasios-Nektarios Tzavellas,
Chrysoula Katrilaka,
Niki Karipidou,
Magdalini Kanari,
Maria Pitou,
Georgios Koliakos,
Angeliki Cheva,
Theodora Choli-Papadopoulou,
Amalia Aggeli,
Eleftherios Tsiridis
Affiliations
Anastasios-Nektarios Tzavellas
1st Orthopaedic and Trauma Department, 424 Military General Hospital of Thessaloniki, 56429 Thessaloniki, PC, Greece
Chrysoula Katrilaka
Department of Chemical Engineering, School of Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Niki Karipidou
Department of Chemical Engineering, School of Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Magdalini Kanari
Department of Chemical Engineering, School of Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Maria Pitou
School of Chemistry, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Georgios Koliakos
Laboratory of Biochemistry, School of Medicine, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Angeliki Cheva
Laboratory of Pathology, School of Medicine, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Theodora Choli-Papadopoulou
School of Chemistry, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Amalia Aggeli
Department of Chemical Engineering, School of Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, PC, Greece
Eleftherios Tsiridis
Center of Orthopaedics and Regenerative Medicine (C.O.RE.), Center of Interdisciplinary Research and Innovation (C.I.R.I.), Aristotle University of Thessaloniki, Balkan Center, 57001 Thessaloniki, PC, Greece
Bone regeneration using Bone Morphogenetic Proteins (BMPs) alongside various engineered scaffolds has attracted considerable attention over the years. The field has seen extensive research in preclinical animal models, leading to the approval of two products and guiding the quest for new materials. Natural and synthetic polymers, ceramics, and composites have been used to fabricate the necessary porous 3D scaffolds and delivery systems for BMPs. Interestingly, all reported applications in the literature are triumphant. Evaluation of the results is typically based on histologic assessment after appropriate staining and radiological modalities, providing morphological identification of the newly formed bone and describing cells and the organic compound. Remarkably, while these evaluation methods illustrate mineralization, they are not capable of identifying hydroxyapatite crystals, the mineral component of the bone, which are crucial for its mechanical properties, structure, integrity, and long-term stability of regenerated bone tissue. This review aims to focus on the different scaffolds used in bone tissue engineering applications and underline the pressing need for techniques that could recognize the presence of hydroxyapatite crystals as well as their characteristics in bone tissue engineering, which will provide a more complete and comprehensive assessment of the successful results.
