BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Microfabrication technology for the engineering of 3D cell laden m icrogels for cell culture and tissue engineering - Professor Marcel Karpe rien\, University of Twente\, Enschede\, Netherlands DTSTART:20170208T080000Z DTEND:20170208T083000Z UID:TALK69745@talks.cam.ac.uk CONTACT:Ilana Spilka DESCRIPTION:It is increasingly recognized that cells respond differently i n 2D and in 3D cell culture. To address this fundamental issue\, my labora tory has developed various microfabrication technologies for the on-chip p roduction of microgels in a size range of 30 to 100µM either laden with a single cell or with multiple cells in a 3D environment. These platforms c an be used for the on-chip production of cell laden microgels using a vari ety of hydrogel materials cross linking in stable macromolecular networks either by photo crosslinking\, ionic crosslinking or enzymatic crosslinkin g. In a side-by-side comparison of these 3 crosslinking methods we demonst rate that on chip crosslinking of PEGDA with UV-light has detrimental effe cts on cell survival and cell function. More than 50% of cells died after 1 day. The remaining cells became metabolically arrested and stopped funct ioning after 3 days. This is due to the relatively high dosage of UV light that is needed for on chip cross linking of the polymers in stable macrom olecular networks due to the short retention time of the microgel droplets on chip. Much more favourable cell survival of approximately 80% cell sur vival after 1 day was observed when cells were embedded in alginate microg els hydrogels by on chip ionic cross linking. Long term cell survival was excellent. However\, these microgels disintegrated within 14 days of cultu re due to leakage of Ca++ ions out of the gel resulting in escape of cells . On chip enzymatic cross linking of tyramine-polymer conjugates proved mo st favourable: Cell survival after 1 day was >95% and the microgels remain ed stable also in long term cultures of more than 4 weeks with neglectable cell escape. Cells remained metabolically active. When human Mesenchymal Stem Cells were encapsulated in these microgels either as single cell or a s multiple cells\, the cells efficiently differentiated into adipocytes an d into osteoblasts depending on the culture conditions. Differentiation ca n be tuned by modifying the mechanical properties of the microgels and by varying the composition of the polymers.\n \nBy introducing small variatio ns in these microfluidic platforms\, we are also able to produce cell lade n hollow microgels with a fully crosslinked shell. When MSCs were captured in the centre of these microgels they spontaneously started to aggregate. The speed of aggregation was tightly and inversely controlled by the cros slinking density of the core of the microgel. Cell aggregation was achieve d both in vitro and in ex vivo organ culture models suggesting that these hollow microgels can be used as in vivo microbioreactors whereby the cross -linked shell separates the gel’s inside from the body. \n\nIn conclusio n\, using microfluidics in combination with enzymatically cross linkable p olymer conjugates it is possible to efficiently develop cell laden microge ls in various configurations. This new technology enables to study cell be haviour in a 3D environment as a function of mechanical properties and gel composition at the single cell level. Furthermore\, it enables the format ion of micro bioreactors for long term culture of cells. Finally\, these c ell laden microgels can be used as building blocks for more complex tissue structures by combining the cell laden microgels with other materials. Th is opens the possibility to develop complex and modular bio-inks for biofa brication processes.\n LOCATION:Online END:VEVENT END:VCALENDAR