Cryogenic 3D Printing of w/o Pickering Emulsions Containing Bifunctional Drugs for Producing Hierarchically Porous Bone Tissue Engineering Scaffolds with Antibacterial Capability.

How to fabricate bone tissue engineering scaffolds with excellent antibacterial and bone regeneration ability has attracted increasing attention. Herein, we produced a hierarchical porous ß-tricalcium phosphate (ß-TCP)/poly(lactic-co-glycolic acid)-polycaprolactone composite bone tissue engineering scaffold containing tetracycline hydrochloride (TCH) through a micro-extrusion-based cryogenic 3D printing of Pickering emulsion inks, in which the hydrophobic silica (h-SiO2) nanoparticles were used as emulsifiers to stabilize composite Pickering emulsion inks. Hierarchically porous scaffolds with desirable antibacterial properties and bone-forming ability were obtained. Grid scaffolds with a macroscopic pore size of 250.03 ± 75.88 µm and a large number of secondary micropores with a diameter of 24.70 ± 15.56 µm can be fabricated through cryogenic 3D printing, followed by freeze-drying treatment, whereas the grid structure of scaffolds printed or dried at room temperature was discontinuous, and fewer micropores could be observed on the strut surface. Moreover, the impartment of ß-TCP in scaffolds changed the shape and density of the micropores but endowed the scaffold with better osteoconductivity. Scaffolds loaded with TCH had excellent antibacterial properties and could effectively promote the adhesion, expansion, proliferation, and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells afterward. The scaffolds loaded with TCH could realize the strategy to "kill bacteria first, then induce osteogenesis". Such hierarchically porous scaffolds with abundant micropores, excellent antibacterial property, and improved bone-forming ability display great prospects in treating bone defects with infection.

Antibacterial dental resin composites (DRCs) with synthesized bis-quaternary ammonium monomethacrylates as antibacterial agents.

Three bi-quaternary ammonium methacrylates (biQAMA-12, biQAMA-14, and biQAMA-16) with different alkyl chain length were synthesized with the purpose of endowing dental resin composites (DRCs) with antibacterial activity without sacrificing physicochemical properties of DRCs. All of biQAMAs were confirmed by 1H-NMR spectra and incorporated into Bis-GMA/TEGDMA (60 wt/40 wt) resin matrix with a mass fraction of 5 wt% as antibacterial agent. The obtained resin matrixes were mixed with commercial silaned glass fillers at a mass ratio of 30 wt/70 wt to prepare antibacterial DRCs. The double bond conversion (DC), antibacterial activity against S. mutans., surface charge density, water contact angle, water sorption (WS) and solubility (SL), mechanical properties, and cytotoxicity of biQAMAs containing DRCs were investigated. The DRC without biQAMAs was used as control. The results showed that all biQAMAs containing DRCs had antibacterial rate higher than 90%, and DRC with biQAMA-12 had the highest antibacterial rate due to its highest surface charge density. Adding 5 wt% of biQAMAs would not bring out negative effect on physicochemical properties of DRCs, except for increasing WS, but the resultant WS still met the ISO requirement on WS of restorative materials. Both biQAMA-14 and biQAMA-16 containing DRCs showed higher cytotoxicity than control, thus biQAMA-12 was considered as the optimal antibacterial agent in this research.