Microscopic Adjustment Of Capillary Self-driven Behavior For Visual Quantitative Biosensors

With the rapid progress of analytical technology,visual biosensors has shown great advantage in home healthcare,accident points and emergency situations,especially necessary in a variety of situations lacking laboratory equipment.Among various quantitative approaches,distance-based visual quantitative detection methods are developed rely on reading the visual signal length for corresponding target concentrations.In recent years,another novel length-based readout method was developed using visualized ink bars owing to volumetric expansion in gas-generation reactions.In the sealed devices,the generated gas could push up the ink bars to move along channels,where the moving distance is closely related with the target concentrations.The distance-based methods are user-friendly and can be integrated into portable analytical devices.An excellent distance-based biosensor should be real-time,affordable,sensitive,specific,equipment-free,and deliverable to the end user without any training,acting like a thermometer.While the use of the current instruments is promising,they may still be too expensive and complicated for developing areas,where various challenges need to be addressed.Herein,we have developed a series of accessible,reusable and quantitative sensor based on capillary behavior change in the capillary tube without auxiliary equipment.The main contents are as follows:1.Capillarity is an extremely common physical-chemical phenomenon related to wettability in nature,which has wide theoretical and practical interest.Herein,we reported a facile sensing device based on capillary force change in vertical capillary tube.In this height-based capillary sensor,the inner surface of the capillary tube was modified with a layer of molecules with wetting responsibility based on the well-known simple surface chemistry.With targets in different concentrations,the wettability of the surface modified with responsive molecules would produce different changes.The responsive surfaces would change the capillary force of the vertical capillary tube,and result in different column height.Like a thermometer.H+ and phenol has been quantified visually based on the height of the liquid inside the capillary tube.2.The microRNAs in life processes show various regulatory functions and their close relationship with certain diseases,so the quantitative detection of miRNAs is very important.With targets in different concentrations,the wettability of the surface modified with responsive molecules would produce different changes.In order to make the visual capillary behavior signal more accurate,we have a larger change in the wettability caused by enzyme amplification for miRNA-21 detection.The visual quantification of miRNAs in the range of 10-13 M?10-8 M was finally achieved(the LOD is 2.5 pM),and the detection of miRNA-16,miRNA-24 and miRNA-26a confirmed that the method has good selectivity.3.DNA hydrogels have received considerable attention in analytical science for their good biocompatibility,processability and excellent designability.We describe an innovative way to prepare a sensitive sensor based on the thermal reversible principle of DNA hydrogel and the principle of capillary action.In this sensor,gel film is subtly prepared in a capillary tube.Because of the slight change in the internal structure of gel,its permeability can be increased by the addition of some specific targets.The capillary behavior is thus changed due to the different permeability of the hydrogel film.The duration time of the target solution flowing through the capillary tube with a specified length is used to quantify this change.With this proposed method,0.01 ?L of hydrogel is sufficient to realize the sensitive detection of cocaine,which has a low detection limit(1.17 nM)and good selectivity.4.DNA molecules have been utilized both as powerful synthetic building blocks to create nanoscale architectures and as inconstant programmable templates for assembly of biosensors.In this paper,a versatile,scalable and multiplex detection system is reported based on an extending fluorescent resonance energy transfer(FRET)cascades on a linear DNA assemblies.Seven combinations of three kinds of targets are successfully detected through the changes of fluorescence spectra because of the three-steps FRET or non-FRET continuity mechanisms.This nano-assembled FRET-based nanowire is extremely significant for the development of rapid,simple and sensitive detection system.