The in situ synthesis of biphasic calcium phosphate scaffolds with controllable compositions, structures, and adjustable properties

Abstract

In this study, biphasic calcium phosphate (BCP) porous scaffolds with controllable phase compositions, controllable macropore percentages, and thus adjustable properties were in situ prepared by sintering a series of composites consisted of calcium phosphate cement (CPC) and porous resin negative mold made from rapid prototyping (RP) technique. The CPC pastes were formed by mixing a powder mixture of tetracalcium phosphate and anhydrous dicalcium phosphate with liquid phase of diluted phosphate acid solution. Results show that the phase composition was easily adjustable by controlling both weight ratio of the powder mixture to the liquid phase (P/L) and concentration of the liquid phase. The macropore structure of the BCP scaffold can be regulated by using different RP negative molds. Through in vitro compressive strength (CS) and immersion tests, it was demonstrated that both macropore percentage and phase composition played important roles in the CS and also the dissolving rates of the scaffolds. As the macropore percentage of the scaffold increased, its CS decreased but the dissolving rate increased; also, as the weight ratio of hydroxyapatite to tricalcium (HA/TCP) in the scaffold increased, the CS first increased and then decreased but the dissolving rate uniformly decreased. The CS values of the BCP scaffolds with a HA/TCP weight ratio of 59:41 were 5.84 +/- 1.16 MPa for a total porosity of approximately 67.67% containing a macropore percentage of 30%, and 3.34 +/- 0.79 MPa for a total porosity of approximately 70.90% containing a macropore percentage of 50%, respectively, comparable to the corresponding levels of human cancellous bone (2-12 MPa).

A review of the mechanical behavior of CaP and CaP/polymer composites for applications in bone replacement and repair

“…All others reported observing either a peak in strength [55,71,72] or simply a decrease in strength [50,57,61]. The data from Metsger et al [74], which reported the increase in strength, are not included in Fig.…”

“…3 because the paper does not provide specific data points. Habibovic et al [72], Guo et al [71] and Raynaud et al [55] showed maximum strengths at approximately 20, 40 and 10 wt.% b-TCP, respectively. In contrast, Miranda et al [70], Shiota et al [63] and Ruys et al [73] all showed a monotonic decrease in strength.…”

“…Without considering any other variables, compressive [63,[70][71][72], flexural [55,70] and biaxial compression strength data [73] for bulk materials and for HA and BCP scaffolds are combined from multiple studies and strength plotted against b-TCP content (Fig. 3).…”

Controlled electrophoretic deposition of HAp/β-TCP composite coatings on piranha treated 316L SS for enhanced mechanical and biological properties

“…If the coating material is dissolved too fast, before the growth of bones or the equilibrium of the implants, the coating is simply worthless. The dissolution rate of HAp is very slow in vivo and may take years to be resorbed [14].β-TCP is chemically stable and has a fairly fast bio resorption rate [15].These reasons justify the development of BCP coatings to achieve the anticipated dissolution rate [16].Many coating techniques such as plasma spraying [17], dip coating [18], sputter coating [19], bio mimetic coating [20], and electrodeposition [21] have been employed to coat ceramics on metal implants.…”

Electrically Polarized Biphasic Calcium Phosphates: Adsorption and Release of Bovine Serum Albumin

“…Among various CPs, hydroxyapatite [HAp, Ca 10 (PO 4 ) 6 (OH) 2 ] and β-tricalcium phosphate [β-TCP, Ca 3 (PO 4 ) 2 ] are most commonly used ones. The high degradation rate of β-TCP makes it difficult to match with the new bone growth rate 4. Some research has been reported on biphasic calcium phosphates (BCPs), consisting of HAp and β-TCP, in which degradation rate can potentially match the new bone growth rate 5-8.…”