Recently, the droplet microfluidic system attracts interests due to its high throughput and low cost to detect and screen. The picoliter micro-droplets from droplet microfluidics are uniform with respect to the size and shape, and could be used as monodispensed micro-reactors for encapsulation and detection of single cell or its metabolites. Therefore, it is indispensable to characterize micro-droplet and its application from droplet microfluidic system. We first constructed the custom-designed droplet microfluidic system for generating micro-droplets, and then used the micro-droplets to encapsulate important amino acids such as glutamic acid, phenylalanine, tryptophan or tyrosine to test the droplets' properties, including the stability, diffusivity and bio-compatibility for investigating its application for amino acid detection and sorting. The custom-designed droplet microfluidic system could generate the uniformed micro-droplets with a controllable size between 20 to 50 microm. The micro-droplets could be stable for more than 20 h without cross-contamination or fusion each other. The throughput of detection and sorting of the system is about 600 micro-droplets per minute. This study provides a high-throughput platform for the analysis and screening of amino acid-producing microorganisms.
Amino Acids ; isolation & purification ; Microfluidic Analytical Techniques ; Microfluidics ; instrumentation

Objective To explore whether voluntary wheel running affects liver oxidative stress by regulating the Nrf2/HO-1 pathway,thereby alleviating HFFC diet-related lipid deposition in the liver.Methods Eight-week-old C57BL/6J mice were randomly divided into a normal diet group(NC group,n=10)and high-fat,fructose,and cholesterol diet group(HFFC group,n=20)after 1 week of adaptive feeding.Ten weeks of feeding later,mice in the HFFC group were divided into a quiet group(HFFC group,n=10)and HFFC combined with exercise group(HFFC+EX group,n=10).HFFC+EX group mice were caged with voluntary running wheels for free movement,and the number of running wheels was recorded every day for 8 weeks.After the last treatment,the mice were sacrificed by fasting for 12 hours at an interval of 24 hours,and the blood and liver were collected for analysis.Results(1)Body weight,liver weight,and liver index of mice fed the HFFC diet were significantly higher than those of the NC group,which significantly decreased after exercise(P＜0.05).(2)Compared with the NC group,HDL-C and LDL-C in the HFFC group were significantly increased,and the LDL-C level was significantly decreased after 8 weeks of exercise(P＜0.05).(3)The liver fat droplet area and liver TG content in the HFFC group were significantly higher than those in the NC group,whereas those in HFFC+EX group were significantly decreased(P＜0.05).(4)Compared with the NC group,the content of oxidase MDA in the HFFC group were significantly increased,and nuclear translocation and gene expression of Nrf2 were significantly decreased.After exercise,the activities of SOD and T-AOC were significantly increased,and the nuclear translocation and gene expression of Nrf2 and expression levels of HO-1 and SOD-1 were significantly increased(P＜0.05).(5)The number of apoptotic hepatocytes and CHOP expression in the HFFC diet group were significantly higher than those in the NC group,whereas the number of apoptotic hepatocytes,and CHOP and Bax/Bcl-2 expression in the exercise group were significantly lower than those in the NC group(P＜0.05).Conclusions Voluntary wheel can alleviate HFFC diet induced liver lipid deposition by regulating the Nrf2/HO-1 pathway,thereby alleviating oxidative stress and reducing apoptosis in liver cells.