PCL-Coated Multi-Substituted Calcium Phosphate Bone Scaffolds with Enhanced Properties

Abstract

Ionic substitutions within the hydroxyapatite lattice are a widely used approach to mimic the chemical composition of the bone mineral. In this work, Sr-substituted and Mg- and Sr-co-substituted calcium phosphate (CaP) scaffolds, with various levels of strontium and magnesium substitution, were prepared using the hydrothermal method at 200 °C. Calcium carbonate skeletons of cuttlefish bone, ammonium dihydrogenphosphate (NH4H2PO4), strontium nitrate (Sr(NO3)2), and magnesium perchlorate (Mg(ClO4)2) were used as reagents. Materials were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Whole powder pattern decomposition refinements of XRD data indicated that increased magnesium content in the Mg- and Sr-co-substituted scaffolds was related to an increased proportion of the whitlockite (WH) phase in the biphasic hydroxyapatite (HAp)/WH scaffolds. In addition, refinements indicate that Sr2+ ions have replaced Ca2+ sites in the WH phase. Furthermore, PCL-coated Mg-substituted and Sr- and Mg-co-substituted scaffolds, with the HAp:WH wt. ratio of 90:10 were prepared by vacuum impregnation. Results of compression tests showed a positive impact of the WH phase and PCL coating on the mechanical properties of scaffolds. Human mesenchymal stem cells (hMSCs) were cultured on composite scaffolds in an osteogenic medium for 21 days. Immunohistochemical staining showed that Mg-Sr-CaP/PCL scaffold exhibited higher expression of collagen type I than the Mg-CaP/PCL scaffold, indicating the positive effect of Sr2+ ions on the differentiation of hMSCs, in concordance with histology results. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis confirmed an early stage of osteogenic differentiation.

Calcium Phosphate Loaded Biopolymer Composites—A Comprehensive Review on the Most Recent Progress and Promising Trends

“…The investigation of the combination of PCL with bioceramic particles such as CaPs is a related topic of current research, and intensive efforts have been made to elaborate the most ideal composite for biomedical applications. In tissue engineering, PCL-CaP composites can be used as scaffolds [164][165][166][167][168][169] as well as coatings [37,[170][171][172][173][174][175][176][177][178].…”

“…Xu et al [165] fabricated 3D artificial polycaprolactone (PCL)-HAp bones by the fused deposition modeling technique. Bauer et al [166] recently prepared PCL-coated multi-substituted calcium phosphate bone scaffolds with improved properties. They used ionic doping within the hydroxyapatite phase to imitate the chemical composition of the bone mineral.…”

Biomimetic Scaffolds Based on Mn2+-, Mg2+-, and Sr2+-Substituted Calcium Phosphates Derived from Natural Sources and Polycaprolactone

“…In our previous studies, individual (Mg 2+ and Sr 2+ ) and dual-ion substitutions (Mg 2+ and Sr 2+ ) into the HAp crystal structure have been studied [26,27]. Mechanical (compression) tests were performed on uncoated and PCL-coated Mg and Mg-Sr substituted calcium-phosphate structures.…”

“…The compressive strengths of the uncoated scaffolds ranged between 0.20 and 0.35 MPa, while the coated scaffolds showed values higher than 1.1 MPa. In vitro cell culture studies showed that scaffolds are nontoxic and provide an adequate 3D support for cell attachment and proliferation [26].…”

Biominerals Added Bioresorbable Calcium Phosphate Loaded Biopolymer Composites

“…They concluded that the incorporation of bioactive glass (BG) increased the bioactivity, and the ion-doping changed the physical-chemical composition of the biomaterial in a way that enhanced its biological effect. The CaP or bioactive glass containing PCL composites are widely used as scaffold materials in bone tissue engineering [ 39 , 40 , 41 , 42 , 43 , 44 , 45 ]; however, in our work, we have focused on developing biodegradable and highly biocompatible thin layers onto the surfaces of metallic implants. The biominerals added nanocrystalline calcium phosphate powder had been embedded into a biopolymer matrix to enhance the adherence and control of the bioresorbility of the coating.…”