Twisted Nylon Monofilament Mold Microchips for On-Line Derivatization of Oligosaccharides Utilizing 8-Aminopyrene-1,3,6-Trisulfonic Acid

A method was developed for the on-line derivatization of polysaccharides with 8-aminopyrene-1,3,6-trisulfonic acid (APTS) using a twisted nylon monofilament mold microchip. We embedded a twisted nylon monofilament in a polydimethylsiloxane (PDMS) solution to fabricate a twisted channel. We utilized a polystyrene case with 2 holes and inserted twisted nylon monofilament sutures through these holes. The PDMS prepolymer was poured onto the case and heated. After cooling the PDMS, we peeled the PDMS from the case and cut the PDMS to generate a twisted microchannel and other reservoirs. The two PDMS layers were then exposed to oxygen plasma. Under this manufacturing condition, the two sutures intertwine to form microchip microchannels, resulting in a non-uniform inner diameter and efficient solution mixing. We used maltopentaose as a model sample to optimize the flow rate, reaction temperature, and number of times the sample passed through the microchannel. These conditions were also used for on-line fluorescent labeling of isomaltooligosaccharides. By repeatedly pumping liquid through this twisted microchannel, the reductive amination of saccharides could be achieved in a short period of time.