Infectious diseases caused by bacteria are still one of the leading causes of death worldwide, despite decades of antibiotic development. Some of the deadliest pathogens, such as Staphylococcus aureus, are capable surviving phagocytosis by immune cells and lay dormant within the host.

Understanding how S. aureus is capable of colonising multiple tissues and organs is fundamental, yet traditional animal models fail to accurately replicate human cellular interfaces or show how bacteria hide within circulating immune cells. This underscores an urgent need for predictive, human-relevant disease modelling that can also reduce animal testing. In this project we will engineer a microfluidics-based 3D printed human tissue model to track this infection pathway and test novel cell-penetrating therapies under physiological flow.

The engineered tissue will have a monolayer of epithelial or endothelial cells to form a continuous vascular barrier with cardiac or neural cells underneath. A blood-mimicking fluid will be continuously pumped through the vascular barrier, establishing realistic hemodynamic shear stress.

This system will be perfused with human macrophages pre-infected with S. aureus. These immune cells act as "Trojan horses"—they shield the live, dormant bacteria from circulating antibiotics and host defences, allowing the pathogen to travel undetected through the bloodstream. Using automated fluorescence microscopy, we will track how these hijacked immune cells survive in circulation, interact with the vessel wall, adhere under flow conditions, and extravasate across the cellular barrier to release the hidden bacteria directly into the 3D-printed tissue matrix.

To isolate the genetic drivers of this dissemination, we will test S. aureus mutant strains deficient in virulence factors or global stress response regulators. We will quantify their attenuated capacity to survive intracellularly, evade host defences, and establish new infection sites within the tissue matrix compared to wild-type bacteria.

Finally, we will use this model to conceptualise and evaluate advanced antibiotic regimens. We will screen highly penetrant antimicrobials capable of eliminating pathogens hidden inside moving immune cells, alongside combination therapies engineered to cross biological barriers and clear deep-tissue infections.