3D Melt-Extrusion Printing of Medium Chain Length Polyhydroxyalkanoates and Their Application as Antibiotic-Free Antibacterial Scaffolds for Bone Regeneration
Elena Marcello, Rinat Nigmatullin, Pooja Basnett, Muhammad Salman Maqbool, M. Auxiliadora Prieto, Jonathan C. Knowles, Aldo R. Boccaccini, Ipsita Roy
Abstract
High Resolution Image Download MS PowerPoint Slide In this work, we investigated, for the first time, the possibility of developing scaffolds for bone tissue engineering through three-dimensional (3D) melt-extrusion printing of medium chain length polyhydroxyalkanoate (mcl-PHA) (i.e., poly(3-hydroxyoctanoate- co -hydroxydecanoate- co -hydroxydodecanoate), P(3HO- co -3HD- co -3HDD)). The process parameters were successfully optimized to produce well-defined and reproducible 3D P(3HO- co -3HD- co -3HDD) scaffolds, showing high cell viability (100%) toward both undifferentiated and differentiated MC3T3-E1 cells. To introduce antibacterial features in the developed scaffolds, two strategies were investigated. For the first strategy, P(3HO- co -3HD- co -3HDD) was combined with PHAs containing thioester groups in their side chains (i.e., PHACOS), inherently antibacterial PHAs. The 3D blend scaffolds were able to induce a 70% reduction of Staphylococcus aureus 6538P cells by direct contact testing, confirming their antibacterial properties. Additionally, the scaffolds were able to support the growth of MC3T3-E1 cells, showing the potential for bone regeneration. For the second strategy, composite materials were produced by the combination of P(3HO- co -3HD- co -HDD) with a novel antibacterial hydroxyapatite doped with selenium and strontium ions (Se–Sr–HA). The composite material with 10 wt % Se–Sr–HA as a filler showed high antibacterial activity against both Gram-positive ( S. aureus 6538P) and Gram-negative bacteria ( Escherichia coli 8739), through a dual mechanism: by direct contact (inducing 80% reduction of both bacterial strains) and through the release of active ions (leading to a 54% bacterial cell count reduction for S. aureus 6538P and 30% for E. coli 8739 after 24 h). Moreover, the composite scaffolds showed high viability of MC3T3-E1 cells through both indirect and direct testing, showing promising results for their application in bone tissue engineering.