Dehydrated aqueous two-phase system micro-domains retain their shape upon rehydration to allow patterned reagent delivery to cells†
Aqueous reagent solution micro-domains with sharp boundaries and defined shapes are created over cell monolayers within an immiscible bulk aqueous phase through rehydration of freestanding and portable dried reagent patches of the corresponding shape. This is in contrast to typical dissolution of reagent tablets or lyophilized biopolymer patches in aqueous solutions where no discernible reagent solution patterns are formed upon their full hydration. The key to enable the engineering of such stable reagent solution micro-domains is to formulate the reagent patches with polymers that form an aqueous two-phase system (ATPS) upon hydration by the bulk aqueous phase. This paper demonstrates this concept using dried reagent patches that incorporate dextran (DEX) and a bulk aqueous phase comprised of cell culture medium containing poly(ethylene) glycol (PEG). For reagents that prefer to partition in the DEX phase of the resulting ATPS, this procedure results in micro-patterned localization of reagent solution only to regions of the cell monolayer covered with the rehydrated DEX patch. The types of aqueous reagent solution micro-domain shapes that can be formed by the rehydration of such freestanding DEX-reagent patches are surprisingly broad and can be readily controlled by use of different templates for dehydrating the DEX solutions or even by cutting flat patches. The utility of the method is demonstrated through localized delivery of fluorescent molecules and enzymes for cell detachment. The patterned enzymatic detachment of cells enables convenient wound healing assays where cell monolayers can be wounded in different shapes dictated by the silhouette of the original DEX-reagent patches.