Integrating Laser-based bioprinting strategies with articular joint microphysiological systems

This thesis aims to advance technologies that enable the reproducible fabrication of complex in vitro models with a high degree of spatial control using laser-based bioprinting. Laser-Induced Forward Transfer (LIFT) is systematically characterised as a cell-printing technique and explored for its integration with living microfluidic systems to study the early pathophysiology of osteoarthritis (OA). This work addresses key challenges in miniaturization, standardization, and fabrication of microphysiological systems, progressing from larger bioreactor platforms towards micropatterned OoC models. By establishing LIFT as an enabling technology for the precise organisation of cells within microfluidic environments, this thesis evaluates the scalability, throughput, feasibility and fabrication constraints of in vitro microfluidic models and discusses their potential adoption in the broader scientific community.
This thesis originates from the scientific question of how early onset OA can be more effectively modelled in a fully human in vitro system. While previous studies have made important progress in developing in vitro OA models, many lack interconnection between different tissues of the knee joint. Such interactions are essential to capture healthy joint function and disease progression in interconnected models encompassing bone, cartilage and synovial lining. Chapter 2 addresses this challenge by engineering a perfusable bioreactor platform for joint modelling in vitro. The chapter describes the design and feasibility of combining four key knee joint tissues within a dually perfused bioreactor chamber. Volumetric Bioprinting (VBP) is used to fabricate a porous cell-laden structure mimicking trabecular bone, connected to a synovial lining compartment through an osteochondral interface designed to reproduce native transport properties. Human mesenchymal stromal cells (hMSC) are differentiated osteogenically within the VBP scaffolds, demonstrating the feasibility of integrating multiple tissue compartments.
However, the platform highlights limitations associated with larger bioreactor systems, including complex assembly, susceptibility to bubbles and leakage, and limited scalability. These challenges motivate the development of more compact and interoperable systems. Chapter 3 explores fabrication technologies capable of introducing microarchitectures in OoC platforms. Several 3D printing techniques were evaluated in terms of resolution, speed, reproducibility, and cell compatibility. LIFT is identified as a promising technology due to its versatility in printing a wide range of biomaterials and cellular suspensions.
Chapter 4 provides a detailed experimental characterisation of LIFT as a high-resolution bioprinting technology for micropatterning vascular co-cultures. A novel metric was introduced to quantify print quality across different ink viscosities, defining a reproducible printability window. Cell deposition was shown to follow a Poisson distribution, enabling predictive patterning of cellular geometries. Chapter 5 applies this framework to micropattern vascular networks in an open-top OoC of the synovial lining, further optimising LIFT for perfusable vascular networks with open lumens under continuous perfusion.
Chapter 6 expands the characterisation of LIFT to cartilaginous spheroids, improving deposition efficiency through an image-guided automation algorithm, “target-and-shoot”. Combining MEW and LIFT enables automated delivery of ACPC spheroids into mechanically reinforcing meshes. Chapter 7 further expands the LIFT printability library by micropatterning coacervates as stable microcarriers. Collectively, this thesis demonstrates LIFT micropatterning of biomaterials, single cells, cell suspensions, co-cultures, cartilaginous spheroids and stable microcarriers.