Microfluidic And Paper-based Analysis Systems For Biochemical Assays

Objective(1) In order to investigate the oxygen carrying capacity of red blood cells(RBCs), we designed erythrocyte biosensors based on paperbased electrochemical analytical devices. They could be applied to quantify the amount of oxygen in RBCs under flowing-through oxygen or nitrogen through electrochemical responses.(2) The biomechanics of RBCs is determined by the integrity of their membrane and cytoskeleton structure. Herein we presented a microfluidic system to examine fragility of RBCs based on using hydrodynamic focusing to dilute the buffer solution around RBCs. In addition, electrochemical detection was integrated for preliminary study of RBCs’ biomechanics.(3) We designed a microfluidic system for continuous observation of plant roots under various abiotic stresses.The investigation of reaction of plants under salinization, drought and other abiotic stresses would probably enhance the anti-stress characteristics of plants.Methods(1) In our design, the filter paper was used to cover RBCs while the double sided conductive carbon tape on an ITO glass was applied as the working electrode to collect signals from RBCs for investigation of their oxygen carrying capacity. The detection system could be put into a closed box for the study of influence of flowing-through oxygen or nitrogen on electrochemical responses of RBCs. Our study indicated that oxygen would increase the responses while nitrogen decrease responses, implying the oxygen carrying capacity of RBCs. We compared the oxygen carrying capacity of the RBCs suspension, the RBCs supernatant and the hemoglobin solution.(2) To study osmotic fragility of RBCs, we build a microfluidic channel with the length of 4 cm by applying hydrodynamic focusing to rapidly dilute the buffer solution and integrating gold electrodes in order to combine electrochemical detection. Such system allows us to observe variation of RBCs under low osmotic conditions. Using a CCD camera, the intensity of individual RBCs could be recorded for the study of the fragility of RBCs. We analyzed the influences of flow rates and chemical treatment on the intensity of RBCs. Meanwhile, the electric resistance was monitored using the gold electrodes at different locations.(3) We constructed a microfluidic platform to put individual arabidopsis thaliana inside the independent microenvironment for observation of their development. Using CCD camera to record the growth condition of roots of arabidopsis thaliana. We studied the growth and development process of arabidopsis thaliana root in the system, as well as the influences of space stress, salty stress and plant hormones on their growth.Results(1) Our experiment results showed that the oxygen-carrying ability of RBCs suspension is superior to that of the RBCs supernatant and the hemoglobin solution. Such differences indicated that the biochemical environment of hemoglobin can significantly affect its ability to carry oxygen. The filter paper-protected cell biosensors could not only be used for the study of the oxygen-carrying ability, but also can be used for other cell analysis.(2) Our results indicated that pure water could rapidly dilute the solution so that the intensity of RBCs changed significantly in the microchannel with 4 cm long. This approach could be used to monitor the fragility of RBCs after treated with glutaraldehyde. Meanwhile, it was found that the relative current decreases with the increase of the distance using gold electrodes for detection, implying that it could potentially applied for the study of fragility of RBCs. Our system could possibly provide a simple way for application of fragility of RBCs for clinical diagnosis.(3) Our results indicated that the salty stress could significantly decrease the development of arabidopsis thaliana, including shortened lateral root and wrinkled cells in their root cap and ground meristem. The space stress could influence the diameters and length of the roots. The main influence of auxin(3-indoleacetic acid, IAA) on the development of arabidopsis thaliana was the enhanced growth of the lateral root. Our approach provide detailed evidences for the study of plant development under abiotic stress.