Chitosan microgels obtained by on-chip crosslinking reaction employing a microfluidic device

Abstract

AbstractIn the present work, we report on the preparation of microgels of chitosan crosslinked with sodium tripolyphosphate (TPP) employing the microfluidics technique (MF). To achieve this, several flow focusing geometries were designed and tested. As a first step, a two-inlet flow focusing geometry was employed to emulsify chitosan and the crosslinking reaction was carried out offchip. This procedure did not allow separating the resulting chitosan microgels due to an incomplete crosslinking reaction. A crosslinking reaction on-chip was studied as an alternative. A four-inlet flow focusing geometrywas designed in which three dispersed phases, chitosan 0.25% (w/v), TPP 0.05% (w/v) and acetic acid 1% (v/v) and an continuous phase mineral oil + Span 80 (3% w/v) were employed. The flow rates for the continuous phase were varied from 6.7 to 11.7 μL/min and chitosan microgels were successfully obtained with average diameters from 68 to 42 μm. The average size of the microgels outside the MF device decreased up to ~21% with respect to their size inside the MF device due to partial expulsion of water from the microgels when complete gelation occurred.