Multifunctional polysulfone/strontium silicate composites with tunable properties through silane functionalization

The development of osteogenic polymer-based bone implants is increasingly essential for load-bearing applications. Upcycling high-performance polysulfone (PSF) waste is a promising option for environmental sustainability. In this study, PSF derived from medical waste served as the matrix, while bioactive strontium silicate (SrSi) acted as the filler. Four silanes with varying chain lengths and functional groups were employed to improve the bonding between the SrSi filler and the PSF matrix. These silane coupling agents included (3-aminopropyl)triethoxysilane (APE), (3-aminopropyl)trimethoxysilane (APM), [3-(2-aminoethylamino)propyl]trimethoxysilane (AEM), and (3-glycidyloxypropyl)trimethoxysilane (GPM). Mechanical properties, in vitro degradation, and antibacterial activity of the composites were examined. Human mesenchymal stem cells (hMSCs) and RAW 264.7 cells were utilized to evaluate the biological functions of the composites. Results indicated that modifying the composite with 5% APE yielded the highest mechanical strength and modulus, with improvements of 42% in compressive strength and 21% in three-point bending strength, along with increases of 130% and 81% in modulus, respectively. After a 12-month soaking period in solutions at pH 7.4 and 5.0, the initial three-point bending strength (120 MPa) of the 5% APE-modified composite decreased to 97 MPa and 80 MPa. Notably, the SrSi significantly enhanced the antibacterial activity of composites compared to PSF alone and inhibited the growth and differentiation of RAW 264.7 cells. Cell growth and osteogenic tests on hMSCs strongly supported the enhanced in vitro osteogenic efficacy of SrSi-containing composites. Given their mechanical properties and biological performance, 5% APE-modified PSF/SrSi-based composites may be suitable for load-bearing applications.