Atherosclerosis is a progressive disease that can significantly reduce blood supply to vital organs, being one of the main causes of death worldwide. In this work, a numerical and experimental study in 3D printed stenotic coronary arteries, considering both steady and pulsatile blood flow conditions, is presented. The results revealed that a degree of stenosis superior to 50% creates disturbed flows downstream of the contraction, with an accented increase in the wall shear stress measurements at the stenosis throat. Finally, the multiphase mixture was investigated and compared with a single-phase modelling, and only slight differences were observed right after the stenosis throat.

Atherosclerosis is one of the most serious and common forms of cardiovascular disease and a major cause of death and disability worldwide. It is a multifactorial and complex disease that promoted several hemodynamic studies. Although in vivo studies more accurately represent the physiological conditions, in vitro experiments more reliably control several physiological variables and most adequately validate numerical flow studies. Here, a hemodynamic study in idealized stenotic and healthy coronary arteries is presented by applying both numerical and in vitro approaches through computational fluid dynamics simulations and a high-speed video microscopy technique, respectively. By means of stereolithography 3D printing technology, biomodels with three different resolutions were used to perform experimental flow studies. The results showed that the biomodel printed with a resolution of 50 μm was able to most accurately visualize flow due to its lowest roughness values (Ra = 1.8 μm). The flow experimental results showed a qualitatively good agreement with the blood flow numerical data, providing a clear observation of recirculation regions when the diameter reduction reached 60%.

Advances in three-dimensional cell cultures offer new opportunities in biomedical research and drug development. However, there are still challenges to overcome, including the lack of reliability, repeatability and complexity of tissues obtained by these techniques. In this study, we describe a new bioprinting system called reactive jet impingement (ReJI) for the bioprinting of cell-laden hydrogels. Droplets of gel precursor solutions are jetted at one another such that they meet and react in mid-air before the gel droplets fall to the substrate. This technique offers a combination of deposition rate, cell density and cell viability which is not currently matched by any other bioprinting technique. The importance of cell density is demonstrated in the development of bone microtissues derived from immortalised human bone marrow stem cells. The cells were printed with high viability within a collagen-alginate-fibrin gel, and tissue specific gene expression shows significantly higher tissue maturation rates using the ability of the ReJI system to deposit gels with a high cell density.

Temporary single-cell coating is a useful tool for cell processing, allowing manipulation of cells to prevent cell attachment and agglomeration, before re-establishing normal cell function. In this work, a speckled coating method using a known polycation [poly(l-lysine), PLL] is described to induce cell surface electrostatic charges on three different cell types, namely, two bone cancer cell lines and fibroblasts. The morphology of the PLL speckled coating on the cell surface, internalization and metabolization of the polymer, and prevention of cellular aggregations are reported. Polymer concentration was found to be the key parameter controlling both capsule morphology and cell health. This approach allows a temporary cell coating over the course of 1–2 h, with cells exhibiting phenotypically normal behavior after ingesting and metabolizing the polymer. The process offers a fast and efficient alternative to aid single-cell manipulation for bioprocessing applications. Preliminary work on the application of PLL speckled cell coating in enabling reliable bioprinting is also presented.

Drop-on-demand (DoD) inkjet printing has been explored for a range of applications, including those to selectively deposit cellular material, due to the high accuracy and scalability of such systems when compared with alternative bioprinting techniques. Despite this, there remain considerable limitations when handling cell suspensions due to the agglomeration and sedimentation of cells during printing, leading to a deterioration in jetting performance. The objective of this work was to design and assess the effectiveness of a custom agitation system to maintain cellular dispersion within the ink reservoir during printing. The cell printing performance of an inkjet printer was assessed with and without the use of a custom agitation system, with biological characterisation performed to characterise the impact of the agitator on cellular viability and function. Cell printing performance was retained over a 2 h printing period when incorporating an agitated reservoir, with a gradual reduction in performance observed under a non-agitated configuration. Cell assays indicated that the agitation process did not significantly affect the viability, metabolic activity or morphology of the mesenchymal stromal cell (MSC) or chondrocyte cell types. This study therefore provides a new methodology to increase process reliability within DoD printing platforms when jetting cellularised material.