Biocomposite material based on dicalcium phosphate dihydrate

Abstract

The results of wet two-stage synthesis of tricalcium phosphate followed by high-temperature treatment are reported. The effect of incorporating tricalcium silicate and alkaline silicate glasses in formation of biocomposite materials based on dicalcium phosphate dihydrate (DCPD) was examined. It was found that use of the bioactive glass 50S25N5P in the amount of up to 10% of the mass content increases the compressive strength and pH to a physiologically safe level in the composite material in comparison to unmodified DCPD. The composite obtained ensures formation of osteoid tissue for 30 days.Key words: biocomposite, dicalcium phosphate dihydrate, bioactive glass, b-tricalcium phosphate. Implantation materials made of bioactive glass and glass ceramics are used in practice in osteoplastic surgery to reduce defects of complex shapes. Attaching and fitting the implant snugly in the bone matrix is the key problem in implanting them: in most cases, the implant is fixed with titanium plates, screws, and pins and gaps are filled with bone chips. Using titanium attachment systems disturbs the integrity of the prosthetic material and causes dangerous stresses in its bulk. An alternative solution is to use bone cements made of hydroxyapatite (HA) Ca 10 (PO 4 ) 6 (OH) 2 and dicalcium phosphate dihydrate (DCPD) CaHPO 4 × 2H 2 O; in attaching bone fragments with the implant material, they ensure a tight fit. The advantage of these compositions is the possibility of injecting them through a syringe, which atraumatically increases the density of bone tissue, for example, the bodies of vertebrae damaged by osteoporosis [1,2].We attempted to create a composite material from DCPD and resorbable, easily hydrated silicate glasses to increase the porosity of cement stone and regulate the pH and initial strength.We know that dicalcium phosphate dihydrate is one of the most soluble calcium phosphates in physiological medium with pH = 7.2 -7.4. The solubility of DCPD (PR = 10 -6.63 ) is higher than the solubility of HA (PR = 10 -117.2 ), and the biodegradation rate is comparable to the rate of regeneration of bone tissue.The high-temperature form of tricalcium phosphateb-Ca 3 (PO 4 ) 2 (b-TCP), obtained by precipitation of calcium nitrate and ammonium hydrophosphate from aqueous solutions with addition of ammonium hydroxide to maintain the pH at 6 -7 according to the following reaction [3] is one of the components for obtaining DCPD 3Ca(NO 3 ) 2 + 2(NH 4 ) 2 HPO 4 + 2NH 4 OH = Ca 3 (PO 4 ) 2 × 2H 2 O¯+ 6NH 4 NO 3 .(1)According to the XPA data, the reaction products are represented by a series of phases of variable composition (Fig. 1a ). The filtered and dried residue is represented by b-TCP after heat treatment at T = 1200°C for 4 h (Fig. 1b ).Synthesis of b-TCP is two-stage and ensures a 100% yield of the final product of the reactions.The IR spectra of the b-Ca 3 (PO 4 ) 2 obtained contains absorption bands corresponding to vibrations of PO 4 3-groups and Ca 2+ . There are no vibrations of hydrophosphate HPO 4 2-, pyrophosphate PO 7 ...

Materials in the Na2O–CaO–SiO2–P2O5 System for Medical Applications

“…It was established that the optimal incorporated bioglass content should be not greater than 10 wt.%, irrespective of the form of the initial β-TCP and the type of glass (amorphous or crystalline), as such composites possess desirable properties [113]: strength in compression 12-20 MPa, pH 4.2-5.5, and high resorption rate 8-20%. The biocompatibility and bioactivity of these composites have been confirmed in vitro and in vivo [113,117].…”

“…In fact, Lukina et al [113,117] investigated bioglass-powder-incorporating brushite cement composites (100 − x)brushite/xBioglass (x = 0, 10, 20 wt.%), where the composition of bioglass was close to that of Bioglass 45S5, i.e., 25 Na 2 O, 20 CaO, 50 SiO 2 , and 5 P 2 O 5 wt.%. Brushite was obtained by Reaction (1).…”

“…Brushite was obtained by Reaction (1). DCPD crystallizes in lamellar crystal forms (≈8 µm long and 2 µm wide), whose physical coupling and intertwining give the cement stone strength [117]. Brushite cement possesses porosity (≈40-45%), pH (≈3.3) and compressive strength (15 MPa), thereby 90brushite/10Bioglass composites demonstrated slightly enhanced pH and compressive strength up to ≈ 3.8 and 16 MPa, respectively, as well as a bimodal pore structure on holding in buffer solution [117].…”

“…DCPD crystallizes in lamellar crystal forms (≈8 µm long and 2 µm wide), whose physical coupling and intertwining give the cement stone strength [117]. Brushite cement possesses porosity (≈40-45%), pH (≈3.3) and compressive strength (15 MPa), thereby 90brushite/10Bioglass composites demonstrated slightly enhanced pH and compressive strength up to ≈ 3.8 and 16 MPa, respectively, as well as a bimodal pore structure on holding in buffer solution [117]. Bioglass incorporation always enhances the pH as bioglass content increases, especially in composites containing crystallized glass granules compared to amorphous glass granules, but decreases the rate of brushite crystallization [113].…”