Crosslinking characteristics of an injectable poly(propylene fumarate)/?-tricalcium phosphate paste and mechanical properties of the crosslinked composite for use as a biodegradable bone cement

Abstract

We investigated the crosslinking characteristics of an injectable composite paste of poly(propylene fumarate) (PPF), N-vinyl pyrrolidinone (N-VP), benzoyl peroxide (BP), sodium chloride (NaCl), and beta-tricalcium phosphate (beta-TCP). We examined the effects of PPF molecular weight, N-VP/PPF ratio, BP/PPF ratio, and NaCl weight percent on the crosslinking temperature, heat release upon crosslinking, gel point, and the composite compressive strength and modulus. The maximum crosslinking temperature did not vary widely among formulations, with the absolute values falling between 38 degrees and 48 degrees C, which was much lower than that of 94 degrees C for poly(methyl methacrylate) bone cement controls tested under the same conditions. The total heat released upon crosslinking was decreased by an increase in PPF molecular weight and a decrease in N-VP/PPF ratio. The gel point was affected strongly by the PPF molecular weight, with a decrease in PPF molecular weight more rapidly leading to a gel point. An increase in initiator concentration had the same effect to a lesser degree. The time frame for curing was varied from 1-121 min, allowing the composite to be tailored to specific applications. The compressive strength and compressive modulus values increased with decreasing N-VP/PPF, increasing NaCl content, and increasing BP/PPF ratio. For all formulations, the compressive strength values fell between 1 and 12 MPa, and the compressive modulus values fell between 23 and 265 MPa. These data suggest that injectable PPF/beta-TCP pastes can be prepared with handling characteristics appropriate for clinical orthopedic applications and that the mechanical properties of the cured composites are suitable for trabecular bone replacement.

Biologically and chemically optimized composites of carbonated apatite and polyglycolide as bone substitution materials

“…Recent suggestions include chitin + HAP by Khor et al 23 ; collagen + HAP by Cui et al 24 ; polyethylene glycol/poly(butyleneterephthalate) + HAP by Liu et al 25,26 ; collagen-hyaluronic acid + HAP by Bakos et al 27 ; unsaturated linear polyesters + ␤-TCP by Mikos et al 28 ; polyurethane + glass ceramics by Ignatius et al 29 ; PLLA (poly-L-lactic acid) + HAP by Verheyen et al, 30 Zhang and Ma, 31 and Uskokovic et al 32 ; PLA + ␣-TCP or glass ceramics by Claes et al 33 ; and carbon + HAP by Li et al 34 Agrawal and Athanasiou were the first (to our knowledge) to combine basic additives (CaCO 3 , NaHCO 3 , HAP) with polyesters (PLGA) to compensate for the release of acidic degradation products. 14 In most cases, the mechanical properties were improved in such composites.…”

“…14 In most cases, the mechanical properties were improved in such composites. The biological response, upon testing, ranged from good, 24,29 to ambiguous, 28,35 to unfavorable. 33 However, none of the materials appears to have achieved the ultimate goal of the clinical surgeon: a device able to replace autologous spongiosa for treatment of bone defect.…”

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…To mimic PMMA cements, PFF/ b-TCP biocomposites were prepared with the addition of vinyl monomer to crosslink PPF. As a result, quick setting and degradable biocomposite cements with a low-heat output and compressive strengths in the range of 1 to 12 MPa were prepared by varying the molecular weight of PPF, as well as the contents of the monomer, b-TCP, initiator, and porogen (NaCl) [453,454]. An acrylic cement with Sr-containing HA as a filler [110] and an injectable polydimethylsiloxane/HA cement [455] have been prepared as well.…”

“…The suspension is liquid at pH within 10-12, but gels quickly at pH \ 9. Injectable composites can be formed with b-TCP to improve mechanical integrity [453]. Similarly, Bennett et al [733] showed that a polydioxanone-co-glycolide-based biocomposite reinforced with HA or b-TCP can be used as an injectable or moldable putty.…”

Fabrication and Characterization of Poly(Propylene Fumarate) Scaffolds with Controlled Pore Structures Using 3-Dimensional Printing and Injection Molding

“…7 Previous studies have also shown that the addition of ceramic components, such as b-tricalcium phosphate, to PPF enhanced both mechanical strength and osteoconductive properties of the scaffold. 8,9 To date, most PPF scaffolds have been fabricated from crosslinking in combination with the salt-leaching technique. 10,11 This method can fabricate highly porous scaffolds with various pore characteristics by controlling the content and size of salt particles.…”