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(2022)ThesisThere has been a rapid-growing market and academic enthusiasm for small wearable molecular diagnostic platforms driven by the growing demand for continuous monitoring of human health. Wearable devices need to be portable, stretchable, and ideally re-configurable to be able to work for different analytes. Such flexible physiological monitoring devices which are non-invasive or minimally-invasive represent the next frontier of biomedical diagnostics. They may make it possible to predict and prevent diseases or facilitate treatment by diagnosing diseases at the initial stages. However, there are many problems that restrict further applications of these devices. Firstly, there are a limited number of bio-materials which are highly flexible, biocompatible and have anti-fouling properties; such biomaterials are needed as substrates for wearable devices. Secondly, traditional biosensors used in wearable devices focus on the detection of physical signals (such as heartbeat) and small chemical molecules, e.g. Na+, K+. These are not sufficient to provide in depth health information which requires sensing of large molecules such as proteins, ideally in real time, which is currently challenging. This provides a motivation to develop highly sensitive wearable biosensors for the detection of large molecules in sweat. This thesis centres on the development of a bio-material based wearable device for continuous detection of crucial analytes in human sweat. To achieve this target, our first aim was to design a highly bio-compatible flexible material as a substrate for wearable devices. A tough and anti-fouling three-network hydrogel has been prepared by integrating a zwitterionic polymer network into a robust double-network hydrogel. Secondly, to fill the gap between technological development of continuous and non-invasive detection of different analytes in human sweat, a patterned sweat-based biosensor was created for the detection of key biomolecules. This sensor was produced by placing specific aptamers or enzymes on flexible working electrodes. In addition, nanotechnology methods have been applied to refine the bio-sensing interface to further increase the sensitivity of our sensors. Finally, a sample collection chip has been combined with our high sensitivity sensors to fabricate a wearable device for sweat bio-sensing purposes. Future research may involve integration of a commercially available wireless signal readout module with this wearable biosensing device. The outcomes of this work may provide new insights for the development of wearable devices for continuous measurement of a spectrum of analytes in sweat, as an important step towards point-of-care diagnostics
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(2024)ThesisOsteochondral tissue comprises of complex chemical, cellular and physical gradients which pose an immense challenge for repair via traditional tissue engineering approaches. Granular hydrogels have emerged as an exciting new opportunity for control of micro- and macro- scale properties for fabrication of complex tissue environments. This thesis explores the utility of gelMA-microgel based granular scaffolds for tissue engineering, with a focus on the osteochondral interface. First, scaffolds were optimised for MSC chondrogenesis by manipulating interstitial filler volume. Higher volumes were found to promote cell sphericity, proliferation, and aggregation, which led to enhanced chondrogenic matrix deposition. Second, incorporation of bioactive Laponite® -RD and -XLG nanosilicates is explored for MSC osteogenesis. Nanosilicate inclusion significantly enhanced MSC osteogenesis but was not found to be osteo-inductive. Third, embedded extrusion printing was utilised for deposition of a bone-mimetic ink in optimised MSC-laden microgel suspensions. Photo-crosslinkable gelMA microgels allowed tuning of ink properties, thus improving robustness. Over 21 days, MSCs exhibited gradient-like chondrogenic ECM deposition away from the bone and mineralisation close to it. Lastly, vascular structures were fabricated using a casting approach for straight channels and direct writing with a sacrificial ink for complex geometries. Design of a novel PDMS-based reactor allowed channel fabrication and long-term perfusion of constructs within the same setup. Taken together, this thesis demonstrates the modularity and versatility of gelMA microgel based granular suspensions and lays the foundation for their use in the fabrication of complex tissue models replete with vasculature.