| Objective To explore the formulation of a novel absorbable bone cement made from polypropylene fumarate (PPF) and hydroxyapatite (HA), and to evaluate its in vitro bioactivity.Methods PPF was synthesized using a two-step method. The number-average molecular weight, weight-average molecular weight, and polydispersity index (PDI) of PPF were determined by gel permeation chromatography (GPC). The structure of PPF was analyzed by proton nuclear magnetic resonance (1H NMR). Various formulations of PPF/HA bone cement were prepared, including PPF with different molecular weights (6 h, 8 h), PPF (8 h) with DMPT in 1∶1 and 1∶10 ratios, PPF with different particle sizes of hydroxyapatite, and PPF/HA formulations with varying ratios (100∶10, 100∶20, 100∶30). The mechanical properties and in vitro biocompatibility of the bone cements were further investigated.Results PPF was successfully synthesized via the two-step method. Nitrogen protection and oil pumps reduced the molecular weight distribution (polydispersity, PD) value and accelerated the reaction; however, when the reaction time exceeded 24 h, the molecular weight decreased. The addition of nano-hydroxyapatite enhanced the mechanical properties of the PPF bone cement. The compressive strengths for formulations 1-7 were (95.08±3.40), (119.80±9.57), (84.00±6.36), (116.80±6.94), (125.60±4.09), (147.00±4.30), and (130.40±2.88) MPa, respectively. The elastic moduli were (804.60±15.38), (855.00±16.94), (729.80±40.19), (883.20±6.22), (896.00±7.68), (976.80±18.36), and (920.00±8.83) MPa, respectively. Scanning electron microscopy (SEM) images showed good adhesion and growth of MC3T3-E1 cells on the surface of the bone cement. As the HA content increased, the number of cells also increased. Osteogenic differentiation and mineralization tests showed that the number of calcium nodules for the blank group, PPF, PPF/10%HA, PPF/20%HA, and PPF/30%HA were 101.00±3.60, 100.33±3.05, 115.00±2.00, 141.66±11.93, and 155.00±3.00, respectively. The degradation of PPF in PBS showed a weight loss of (1.41±0.01)% after the first week, and a total weight loss of (7.57±0.06)% over the first four weeks. With the addition of HA, the degradation rate of PPF decreased. The PPF/30%HA composite showed a weight loss of (1.20±0.036)% after the first week and a total weight loss of (5.36±0.08)% over the first four weeks.Conclusion As the molecular weight of PPF, the content and particle size of HA increase, the compressive strength and elastic modulus of the bone cement improve. However, when the HA content exceeds 20%, the mechanical strength of the bone cement decreases. The PPF (8 h) with 200 nm HA at a 100∶20 ratio and in a 1∶1 PPF/DMPT system exhibited the best mechanical properties and good biocompatibility. |
