From nano to macro: Enabling Nanotechnologies for Human Organ Biofabrication (Electrospun Nanofibers and Hybrid Technique)

This review proposes to present how materials at nanolevel scale can contribute to the development of three-dimensional (3D) structures, human tissues, and organs which have macrolevel organization. Specific nanomaterials such as nanofibers and nanoparticles are presented and discussed in their application for biofabricating 3D human tissues and organs. The concept of self-assembling magnetic tissue spheroids as an intermediate mesolevel structure between nano and macrolevel organization and building blocks for biofabrication in dual scale level of complex 3D human tissues and organs is detached. The challenges and perspectives of employing nanomaterials and nanotechnological strategies in the biofabrication were also traced

Investigation of the effect of nozzle design on rheological bioprinting properties using computational fluid dynamics

Bioprinting is the utilization of techniques derived from three-dimensional printing to generate complex biologicalstructures which may replace natural tissues or organs. It employs high spatial resolution depositionof different cell types, growth factors and biomaterials. Those together form bioinks, which are the bioprintinginputs, analogously to conventional inks with regard to inkjet printing. In extrusion bioprinting, continuousbioink filaments are deposited layer by layer on a surface by means of an extruder nozzle, employing thedisplacement of a piston or pneumatic pressure. If mechanical stresses applied on a cell membrane exceed acritical value, which depends on the cell type, the cell membrane may disrupt. Computational fluid dynamics(CFD) simulations of the bioink extrusion were done to evaluate shear stresses caused by the internal pressureof extruder nozzles during bioprinting. Different three-dimensional conical nozzle designs were testedby varying angles of convergence, lengths, input diameters and output diameters of the nozzles. The powerlawmodel, with constants k = 109.73 Pa·s0,154 and n = 0.154, was used to describe the expected non-Newtonian behavior of the bioink. Shear stresses and shear rates were evaluated for each nozzle design consideringdifferent pressures or velocities as boundary conditions at the nozzle entrance. The maximum wallshear stress value on each different nozzle varied between 1,038 Pa and 4,915 Pa. The results indicated whichdetails of nozzle geometry are most relevant in order to optimize bioprinting. The best conditions for bioinkrheology were also evaluated to ensure good printability and high cell viability.Keywords: bioink, bioprinting, biofabrication, 3D printing, CFD

Oxidative Nanopatterning of Titanium Surface Influences mRNA and MicroRNA Expression in Human Alveolar Bone Osteoblastic Cells

Titanium implants have been extensively used in orthopedic and dental applications. It is well known that micro- and nanoscale surface features of biomaterials affect cellular events that control implant-host tissue interactions. To improve our understanding of how multiscale surface features affect cell behavior, we used microarrays to evaluate the transcriptional profile of osteoblastic cells from human alveolar bone cultured on engineered titanium surfaces, exhibiting the following topographies: nanotexture (N), nano+submicrotexture (NS), and rough microtexture (MR), obtained by modulating experimental parameters (temperature and solution composition) of a simple yet efficient chemical treatment with a H2SO4/H2O2 solution. Biochemical assays showed that cell culture proliferation augmented after 10 days, and cell viability increased gradually over 14 days. Among the treated surfaces, we observed an increase of alkaline phosphatase activity as a function of the surface texture, with higher activity shown by cells adhering onto nanotextured surfaces. Nevertheless, the rough microtexture group showed higher amounts of calcium than nanotextured group. Microarray data showed differential expression of 716 mRNAs and 32 microRNAs with functions associated with osteogenesis. Results suggest that oxidative nanopatterning of titanium surfaces induces changes in the metabolism of osteoblastic cells and contribute to the explanation of the mechanisms that control cell responses to micro- and nanoengineered surfaces