| In the aptamer-based microcantilever array sensor,the sensing recognition unit is the cantilever beam array whose surface is modified by aptamers in the manner of a self-assembled monolayer.When the target molecule is present interacting with the aptamer,the interaction between them results in the surface stress of the cantilever changing,then inducing cantilever deflection(or vibration frequency variation).A detection method constructed by detecting the relationship between cantilever deflection(or vibration frequency variation)and the concentration of target molecules,which is called aptamer-based microcantilever array sensor.This sensor can convert the information of the chemical reaction on the cantilever surface into the mechanical movement of the microcantilever and has the advantages of simple operation,sensitive detection,free-label etc.Based on the cantilever deflection mode of this sensor,our paper mainly studied the following contents:1.A novel method for detecting epithelial tumor marker MUC1 was successfully constructed by using the principle of mucin 1(MUC1)and aptamer interaction inducing the change of surface stress on the microcantilever.In this method,MUC1 was determined simply and label-free with good sensitivity and selectivity.The linear range was from 5 nmol/L to 500 nmol/L with the lowest detection limit was 0.9 nmol/L(S/N=3).In the meantime,the dynamic process of the binding of MUC1 to the aptamer was revealed according to the relationship of the deflection signal of the microcantilever over time.Furthermore,it also can be used to diagnose human breast carcinoma MCF-7 cells with MUC1 as their biomarkers with the lowest detection limits of 213 cells/mL.Therefore,it is worthy for pointing out that the successful use of microcantilever aptasensor in detecting biomarker in the early stage of cancer even can extend to disease diagnosis and biological analysis.2.A signal-amplifying strategy by using Au nanoparticle(NP)-DNA conjugates was developed to detect dopamine(DA)based on aptamer functionalized-microcantilever array sensor.Au NP-DNA conjugates were combined on the microcantilever functionalized by aptamer firstly.In the presence of DA,the aptamers captured DA and released Au NP-DNA conjugates,bringing the surface stress change resulting in the microcantilever deflection.The ability of detecting DA was improved by approximately fifteen-fold compared with that of microcantilever array functionalized by aptamers alone.The deflection value of microcantilever array was linearly dependent on DA concentration in the range from 0.5 to 4 ?mol/L,with the limit of detection 77.3 nmol/L.This aptamer-based microcantilever array sensor introducing Au NP-DNA conjugates into the nanomechanical transducers is label-free,high-effective and low-cost for quantitative detection of DA,which may be further extended to the detection of various kinds of low-molecular-weight samples and provides a promising outlook for detecting other molecules using nanoparitcles as signal-amplifying strategy.3.A microcantilever array sensor for simultaneous detection of two biomarkers carcino-embryonic antigen(CEA)and alpha fetoprotein(AFP)has been constructed by aptamer-antibody sandwich assay and microcantilever multi-array and combining with capillary independent modification technology.The lowest detection limits of CEA and AFP were 1.3 ng/mL and 0.6 ng/mL,respectively,which were 7-fold and 12-fold higher than those without the sandwich structure.In addition,this approach employed a readout technology-real-time monitoring the profile of cantilever.This readout technique provides absolute values of the cantilever profile rather than relative variations of the local slope in less than one second.The proposed microcantilever array sensing system detects two components with enhanced the detection sensitivity and lies a foundation for simultaneous detecting more components.It can be applied to simultaneously detect various kinds of aims in biochemical research and clinical diagnosis. |
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