Electrophoresis Separation And Online Field Amplified Sample Stacking Of DNA On A PDMS Microchip

Small sample consumption is one of the main features of capillary electrophoresis(CE)and microchip electrophoresis(MCE),which is also the reason of their poor sensitivity.Online sample preconcentration is effective for increasing the sensitivity without use of expensive equipment.Field-amplified sample injection(FASI),known as the most common sample preconcentration method,is mainly used in CE and MCE.Here we combined on-chip field-amplified sample injection with highly efficient separation ability of a chip electrop-horesis system to achieve improved separation of DNA.In the first chapter,sample introduction methods of microchip electrophoresis are introduced,and common online preconcentration techniques,particularly the applications of field-amplified sample stacking in CE and MCE are summarized.In the second chapter,separation and detection of DNA with microchip electrophoresis system of PDMS substrate with a simple cross-channel pattern is demonstrated.Factors that affect the separation efficiency,such as the treatment of PDMS surface,injection voltage,injection time,concentration of dye(EB)were examined.Eleven fragments of DNA Marker were successfully separated within 6 min under optimized conditions:injection voltage 200 V,injection time 8 s and concentration of EB 3 ?g/mL.In the third chapter,we introduced field-amplified sample injection mechanism to the simple cross-channel PDMS microchip electrophoresis system by introducing a deionized water plug into the sample loading channel.With fluorescein sodium as the probe molecule,factors such as the viscosity of background electrolyte(BGE),height difference of liquid level between front and end reservoirs of the separation channel,stacking voltage were optimized.Under the optimal conditions of 1%HEC as BGE,liquid level difference of 2 cm,stacking voltage 300 V,stacking time 100 s,we demonstrated detection of fluorescein sodium with a concentration factor of 500.The above FASI/MCE protocol was also successfully used in the online stacking and separation of DNA Maker with a concentration factor of 15.In this paper,nucleic acids were successfully separated on microchip electrophoresis system of PDMS with simple cross-channel.The developed online FASI-MCE method possess the advantages of simple voltage procedures and easy operation.This work shows that fast separation and sensitive detection of DNA with low cost PDMS chip electrophoresis system is feasible.