{Monitoring microconstructs: cell and nanosensor encapsulation in alginate micro-beads}

Monitoring and controlling the microenvironment of cell cultures is an ongoing challenge for many researchers. Much research has been conducted characterising individual aspects such as 3D architecture, mechanical properties, biochemicals, etc. The biggest deficits in existing models for monitoring analytes within the cellular environment is the lack of appropriate means for non invasive, real-time and integrated monitoring of the cellular responses. Nanosensors can overcome these issues: they are porous polymeric nanoparticles that are sensitive to a range of analytes including pH and O2. Microfabrication techniques are innovative tools to obtain controlled microstructures with a defined 3D architecture. In this work uniform sized 3D micro-scaled hydrogel constructs of approximately 300-400 um diameter were fabricated. Through dual incorporation of cells and nanosensors within these constructs we aim to have a real-time, non invasive method to measure microenvironmental pH value and O2 content. Ratiometric fluorescent output from the microenvironment is used to monitor O2 and pH during cell culture. Measurements show that 3D micro-scaled constructs are suitable for cell growth and proliferation. Moreover O2 content and pH within hydrogel cellularised microspheres are shown to have physiological values which enable the maintenance of the hepatic phenotype.