The effect of the thermosensitive biodegradable PLGA–PEG–PLGA copolymer on the rheological, structural and mechanical properties of thixotropic self-hardening tricalcium phosphate cement

The current limitations of calcium phosphate cements (CPCs) used in the field of bone regeneration consist of their brittleness, low injectability, disintegration in body fluids and low biodegradability. Moreover, no method is currently available to measure the setting time of CPCs in correlation with the evolution of the setting reaction. The study proposes that it is possible to improve and tune the properties of CPCs via the addition of a thermosensitive, biodegradable, thixotropic copolymer based on poly(lactic acid), poly(glycolic acid) and poly(ethylene glycol) (PLGA–PEG–PLGA) which undergoes gelation under physiological conditions. The setting times of alpha-tricalcium phosphate (a-TCP) mixed with aqueous solutions of PLGA–PEG–PLGA determined by means of time-sweep curves revealed a lag phase during the dissolution of the a-TCP particles. The magnitude of the storage modulus at lag phase depends on the liquid to powder ratio, the copolymer concentration and temperature. A sharp increase in the storage modulus was observed at the time of the precipitation of calcium deficient hydroxyapatite (CDHA) crystals, representing the loss of paste workability. The PLGA–PEG–PLGA copolymer demonstrates the desired pseudoplastic rheological behaviour with a small decrease in shear stress and the rapid recovery of the viscous state once the shear is removed, thus preventing CPC phase separation and providing good cohesion. Preliminary cytocompatibility tests performed on human mesenchymal stem cells proved the suitability of the novel copolymer/a-TCP for the purposes of mini-invasive surgery.Peer Reviewe

Additional file 1 of Synergistic antibacterial action of the iron complex and ampicillin against Staphylococcus aureus

Additional file 1: Table S1. Primers used for Quantitative Real–Time PCR. Table S2. Electronic spectral data of aqueous solutions of Fe16. Table S3. Expression of the all tested genes of S. aureus shown as Fold change after exposure environmental stress of AMP, Fe16 and Fe16+AMP relative to no treated S. aureus with use of rpoB as housekeeping gene. Figure S1. Physico-chemical characterization of the Fe16 complex. Figure S2. ζ-potential of Fe16, AMP and Fe16+AMP measured in MiliQ water at pH 8.2