No abstract

Composites based on calcium phosphates in the matrix of biopolymer (citrated plasma and fibrin) were synthesized in neutral and alkaline medium. At pH 7 brushite composites were obtained, whereas at pH 11 amorphized hydroxyapatite was precipitated. Disruption of precipitation conditions led to the formation of tricalcium phosphate impurity, which was detected by XRD after thermal treatment of composites at 800 °C. Composition and morphology of calcium phosphates did not depend on biopolymer nature. To determine bioactivity degree, composites were incubated in model Simulated Body Fluid (SBF) for 75 days. It was found that composites based on amorphized hydroxyapatite incorporated in biopolymer matrix have maximum growth of biomimetic layer of apatite.

Biomaterials based on hydroxyapatite with controllable composition and properties are promising in the field of regenerative bone replacement. One approach to regulate the phase composition of the materials is the introduction of biopolymer-based additives into the synthesis process. The purpose of present study was to investigate the formation of hydroxyapatite-based hybrid materials in the presence of 6–24% platelet-poor plasma (PPP) additive, at a [Ca2+]/[PO43−] ratio of 1.67, pH 11, and varying maturing time from 4 to 9 days. The mineral component of the materials comprised 53% hydroxyapatite/47% amorphous calcium phosphate after 4 days of maturation and 100% hydroxyapatite after 9 days of maturation. Varying the PPP content between 6% and 24% brought about the formation of materials with rather defined contents of amorphous calcium phosphate and biopolymer component and the desired morphology, ranging from typical apatitic conglomerates to hybrid apatite-biopolymer fibers. The co-precipitated hybrid materials based on hydroxyapatite, amorphous calcium phosphate, and PPP additive exhibited increased solubility in SBF solution, which defines their applicability for repairing rhinoplastic defects.

Nanocomposites based on apatitic tricalcium phosphate in an autofibrin matrix were obtained by precipitation at a Ca/P ratio of 1.50, pH 9 and a maturation time from 30 min to 7–14 days. The resorbability of nanocomposites was determined by the composition of calcium phosphates, which, during long-term maturation, formed as the calcium-deficient hydroxyapatite with a Ca/P ratio of 1.66, whereas biopolymer matrix favored the formation of more soluble calcium phosphates with a Ca/P ratio of 1.53–1.59. It was found that the fibrin clot stabilized, along with apatitic tricalcium phosphate, the phase of amorphous calcium phosphate, which after 800 °C was transformed into resorbable α-tricalcium phosphate. Citrated plasma inhibited the conversion of apatitic tricalcium phosphate into stoichiometric hydroxyapatite, which also facilitated the formation of resorbable β-tricalcium phosphate after 800 °C. The combined effect of the maturation time and the biopolymer matrix determined the composition, physicochemical and morphological properties of nanocomposites and the possibililty to control its extent of resorption

Applying of blood biopolymers to regulate the phase composition is promising in designing the hydroxyapatite-based hybrid biomaterials with controllable resorbability. Hybrid materials based on hydroxyapatite and platelet-poor plasma (PPP) were formed in conditions of chemical precipi-tation at pH 11, [Ca2+] / [PO43–] ratio 1.67, PPP volume fraction of 6–24%, maturing time of 4–9 days. Mineral component of the materials was represented as 53% hydroxyapatite / 47% amor-phous calcium phosphate after 4 days of maturation, and 100% hydroxyapatite after 9 days of maturation. Varying PPP content from 6% to 24% provided forming of materials with rather de-fined content of amorphous calcium phosphate and biopolymer component, having desired mor-phology ranging from typical apatitic conglomerates to hybrid apatite-biopolymer fibers. Co-precipitated hybrid materials based on hydroxyapatite and PPP are promising for bone regen-eration in osteoplastic and maxillofacial applications.