Development of Antibacterial and Remineralising Composite Bone Cements

The thesis aim is to develop composite cement with (1) optimized curing time/ high reaction rate to prevent cement leakage (1) high monomer conversion to provide good strength, (2) water-sorption to compensate shrinkage and promote anti-bacterial release, (3) release of ions and antimicrobial to remineralise the bone structure and prevent infection, (5), assess the adhesive properties of composites and (4) antibacterial efficacy against various strains of Staphylococcus aureus. Curing time, reaction rate, monomer conversion/ shrinkage was assessed using FTIR and Raman. Water-sorption and anti-bacterial (polylysine and gentamicin) release into deionized water (DW) and simulated body fluid (SBF) were assessed using gravimetrical studies, and UV/ HPLC spectroscopy respectively. Flexural strength, modulus and compressive strength were assessed up to 1 months of SBF storage. Antibacterial efficacy was assessed via bacterial growth in suspension and biofilm formation on disc. Adhesive properties were assessed via pushout and shaerbond test. One way Anova, Two way Anova, Kruskal–Wallis one-way analysis of variance, regression analysis, factorial analysis were used to analyze the data. Increasing initiator and activator concentrations decreased curing time. Furthermore, they enhanced monomer conversion and strength. Addition of calcium phosphate fillers and antimicrobials decreased the curing time and monomer conversion. The major factors enhancing water-sorption were calcium filler and antimicrobial level. Calcium ion and gentamicin (Gen) release was enhanced by the use of deionized water instead of SBF, calcium fillers and polylysine. Higher polylysine (PLS) release was seen with low levels of antibacterial in the filler phase. Flexural strength, modulus and compressive strength were decreased with the addition of calcium fillers and antimicrobials. Lastly, PLS showed reduced bacterial growth in surrounding medium and on set material discs. These materials are therefore promising antibacterial injectable bone composites that could remineralise the bone structure and may prevent postoperative infection. These cements can be used for load bearing areas (vertebroplasty, Hip arthroplasty, dental filling) and non-load bearing areas (bone augmentation etc.)