We created a hybrid nano-bioprinting system, which combines the initial patterning capabilities of direct cell writing with the active patterning capabilities of superparamagnetic nanoparticles. Biofabrication conditions, including printing parameters and scaffold biopolymer properties, may affect cell viability, nanoparticle manipulation and patterning capabilities. Nanoparticles were printed under varied conditions either in the biopolymer or loaded inside cells. Cell viability, alginate viscosity, nanoparticle movement and printing resolution were measured. We now show that while nanoparticles decreased cell viability, nozzle size had no significant effect. High printing pressure decreased cell viability, but viability loss was not accentuated by nanoparticles. High nanoparticle concentrations increased alginate viscosity at higher alginate concentrations. Nanoparticle velocity in response to a magnetic field was a function of nanoparticle diameter and scaffold viscosity, which agreed with a mathematical model of nanoparticle movement. Finally, the nano-bioprinting system resolution and patterning precision were not affected by nanoparticles in the prepolymer solution. These data suggest that nanoparticle incorporation in solid freeform fabrication does not change biofabrication parameters unless high nanoparticle concentrations are used. Future work includes developing vascularized tissue engineering constructs using the nano-bioprinting system.

Purpose Despite the rapid development of fused deposition modeling (FDM), the insufficient mechanical strength of the printed objects is one of the biggest stumbling blocks for practical applications. Therefore, the purpose of this study is to emphasize on the importance of homogeneous heating condition and heating effect in the improvement of the mechanical strength of objects. Design/methodology/approach The authors first analyze the problem of the present heating system under a heating bed and chamber by using a commonly used home FDM printer. Next, they investigate the heating effect on the mechanical properties of FDM-printed objects in terms of layer thickness, heating duration and additional pressure with heating. The printed objects are treated in a mold by forced convection heating. Findings As the layer thickness decreases, the mechanical performance of the FDM-printed objects is remarkably enhanced by thermal heating because of the result of strong interfacial bonding among the rasters and layers. In addition, longer heating duration and higher external pressure play pivotal roles in the mechanical performance by reducing voids in the internal structure of the printed objects, leading to high densification and complete filling at the interfaces. Originality/value The present findings, for the first time, show that controlling uniform heat transfer is highly important for the mechanical performance of FDM three-dimensional printed objects. The authors suggest that the future developed home or personal FDM types should consider the homogeneous temperature environment during the printing process by properly heating the inside chamber. In addition, the results indicate the effectiveness of heating and pressure treatment to the objects for the reinforced mechanical performance and better surface finish.

Bacterial flagella are particularly attractive bio-templates for nanotubes due to their tubular structures and small inner and outer diameters. In this work, flagella isolated from Salmonella typhimurium were used as templates for silica-mineralized nanotubes. The process involved pretreatment of flagella with aminopropyltriethoxysilane (APTES), followed by the addition of tetraethoxysilane (TEOS). By controlling the concentration of TEOS and the reaction time, we developed a simple and precise method for creating silica-mineralized flagella nanotubes (SMFNs) with various thicknesses of the silica layer. It is demonstrated that flagella can be utilized for the fabrication of SMFNs with tunable thickness. A thicker silica layer was obtained as the concentration ratio of TEOS and reaction time was increased. The present experimental evidence has shown the feasibility of using such fabrication techniques to manufacture nanotubes without genetic modification of flagella which retain the original morphology.

We evaluate a method for biofilm disinfection by raising biofilm temperature using the photothermal effect of a gold nanorod cluster. Gold nanorods (GNRs) are capable of generating enough heat to lyse bacteria by heating biofilm via laser irradiation. To test this, GNRs are synthesized using wet chemistry and a single GNR cluster is fabricated using photo-lithography technique. The GNR cluster is directly applied to the biofilm and its effects on bacteria are measured before and after laser irradiation. The photothermal effect of GNRs on the biofilm structure results in a considerable reduction of cell viability and biofilm thickness. Several quantitative measurements of bacterial mortality and biofilm destruction show an increase in efficacy with increasing durations of laser irradiation. Scanning electron microscopy images of the irradiated bacteria show obvious morphological damage such as rupture or collapse of the bacterial cell membrane in the biofilm. These results indicate that GNRs are useful and a potential material for use in photothermal treatments, particularly biofilm disinfection.

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