Printable Cell Growth Platform for the Assessment of Biomaterial–cell Interactions: A Focus on Patterns and Mineral Pigments

Cell-decision making is a highly complex and tightly regulated process that depends on the extracellular environment. In their native conditions, cells sense the immediate surroundings and collect cues from the fluid environment and the extracellular matrix, including surface properties such as roughness, porosity, topography, and chemistry, in order to determine their fate. In contrast, researchers traditionally culture cells on flat plastic surfaces that lack most, if not all, of the extracellular cues. As a result, a large gap and inconsistency exist between laboratory results and clinical translation, often leading to costly failures and delayed therapeutics. Alternatively, animal models are used to predict human response; however, no animal is biologically identical to a human. Surface engineering provides an invaluable opportunity to elucidate mechanistic insights behind cell behaviour and disease progression by replicating already at the in vitro stage the physiological and pathological environments of humans. The first step of this ambitious vision is to expand the traditional cell culture platforms to a device suitable for surface engineering approaches.
This thesis proposes a printable cell culture platform compatible with most large-scale fabrication and surface modification techniques. The approach encourages the use of numerous state-of-the-art technologies available through functional coating and printing, while remaining accessible to conventional biological assessment and imaging techniques. In addition, the presented printable cell culture platform is a low-cost and simple device, widely available to researchers who have access to a desktop cutter and a hydrophobic printer. Platform compatibility with coating and printing technologies is a useful element within the future of cell biology. It promotes an interdisciplinary integration of advances in surface modification and biomaterials to regulate and control cell behaviour in vitro, while ensuring translation to mass production.
As a proof-of-concept, the printable cell culture platform was used in this thesis to assess wax printing as a tool for contact guidance and mineral-fibroblast interactions. Wax printing was effective for the low-resolution contact guidance of fibroblasts; and when coupled with laser ablation, patterns of high-resolution (down to 10 μm) were achieved. However, high-resolution patterning requires further optimisation as cell preference over the surface was inconsistent throughout the preliminary trials. In the case of mineral-fibroblast interactions, the platform enabled the assessment of direct and indirect interactions due to its sandwich-like structure. Mineral pigments are highly versatile materials used in materials and biomedical sciences to modify and control the physicochemical properties of surfaces among other applications; thus, minerals have the potential to aid in the overall biomimicry of the cellular environment. The study of the same minerals throughout different experimental settings highlights the restrictions of commonly used platforms and the importance of extensive evaluations through novel approaches when dealing with biomaterials. Furthermore, minerals were used in papermaking to successfully create a 3D environment for cancer cell growth within the printable cell culture platform.
Future studies should focus on improvements in the overall configuration of the printable cell culture platform. The inclusion of microfluidics and a 3D printed case would already greatly improve the ease of use of the platform. In addition, functional printed sensors can be added for electrochemical stimulation, detection, and monitoring during cell culture. From a research perspective, there are three major opportunities to be exploited in the printable cell culture platform: (a) co-culture environments, (b) time-dependent release of drug-loaded porous biomaterial coatings, and (c) papermaking for cell culture. This thesis already explores briefly papermaking for cell culture and its advantage to control the cellular environment in paper-based 3D cancer models. Ultimately, the goal is to enhance the in vitro assessment of biomaterials by replicating physiological conditions through a simple approach, which remains compatible both with laboratory studies and industrial-scale production. Such a goal will bring research a step closer to understanding the intrinsic yet convoluted interplay among biological interactions.