Study On Capillary Self-Driven Microfluidic Chip For Ricin Detection

Ricin toxin(RT)is a potential biological warfare agent and bioterrorism agent for its high toxicity,wide distribution and easy preparation.It has long been listed as a Class B biological warfare agent by CDC of United States,and in the control list of Convention on the Prohibition of Chemical and Biological Weapons.In recent years,ricin is frequently associated with terrorist incidents with the spread of extremism and terrorism.Therefore,it is particularly important to develop the on-site rapid detection technology of ricin toxin.A new material with ultra-large surface area named nanoforests is prepared by Micro-Electro-Mechanical System(MEMS)processing technology.The single nanofiber is upright on the substrate with a diameter of about 200~400 nm,a height of5.0?m and a density of about 20/?m~2.Their hydrophilicity and fiber pores provide capillary driven force.Self-driven test provides information of the flow rate of PBS solution is to be about 5 mm/s in the micro-channel on the basis of nanoforests structure.The surface area of high density and nano-scale fibers increased by 100 times and 10times respectively when compared with the planar and micropillar structures with the same base area.The three-dimensional structure of the nanoforests with ultra-large surface area can greatly improve the binding capacity of recognition molecules,thus improving the sensitivity of detection.Based on this material,a new microfluidic chip for point-of-care test is created for dectection of RT,which is sensitive,specific,rapid,accurate and convenient.The linear range of detection is from 10 pg/mL to 6.25 ng/mL and the limit of detection(LOD)is lower than 10 pg/mL.There is no cross reactivity with abrin toxin(AT),botulinum neurotoxin A(BoNT/A),Clostridium perfringens epsilon toxin(ETX).The sensitivity of milk samples can still reach 40 pg/mL,which indicates that the chip can be used for quantitativedetectionofactualfoodsamples.Comparedwiththe immunochromatographic test strip,the microfluidic chip has an advantage of high sensitivity,and the quantitative analysis can be realized within a certain range.Most microfluidic chips require complex equipments to provide driving force,which will make them costly and bulky.Driven by the capillary force,the chip with nano-forests structure inside makes the detection simple and fast.Combined with the miniaturized detection terminal,the platform can be miniaturized,portable,and automated,achieving the goal of simple,fast and efficient analysis.These characteristics make the chip an ideal candidate for the development of rapid detection methods.In addition,the principle of immune response is mostly based on the recognition of antigen and antibody,and then the signals are detected and analyzed through fluorescence,enzyme,magnetic beads,electrochemistry and other markers.Antigen-antibody interaction occurring in the microfluidic channel,which is a solid/solution interface,obeys general mass law principles in solid-phase immunoassays.However,the rapidity is limited by the binding kinetics of antigen-antibodies,which requires long incubation time to recognize.Unfortunately,the flow velocity in microfluidic channel has to be slowed down in order to reach an optimal reaction time,which inevitably leads to a long sample-to-result duration.Therefore,the study has proposed a new method to accelerate the immune reaction to address the major shortcoming based on temperature gradient.By integrating two temperature modules on the opposite side of solid-phase immunoassay carriers,the temperature gradient can be formed.This result in mass-transfer of biomolecules from the warmer medium to the opposite,where the biorecognition events are rapidly driven to complete within a few seconds.This method has few components,low cost and is easy to integrate.Combined with microfluidic chips,it can be miniaturized,portable,automated,and achieving the goal of simple,fast and efficient analysis.