| In recent years,tumor is a serious threat to the health of human beings.Rapid and highly sensitive detection methods for tumor markers are of great significance in the early diagnosis of diseases.However,the traditional methods for tumor markers detection have several defects,such as complicated operation,low sensitivity and the high cost of reagents and instruments.Therefore,it is of great significance to develop simple and sensitive detection methods for tumor markers detection without the need of complex instruments.The liquid crystal based biosensor,which uses liquid crystal as a signal conversion element,can realize the visual detection of the target analyte through a homeotropic-to-tilted alignment transition of liquid crystal molecules.Compared to other analytical approaches,the liquid crystal based biosensor has the advantages of simple,low cost and easy to realize miniaturization without the need of special equipment and light source.However,the liquid crystal based biosensors constructedin literature have the disadvantages of low sensitivity and weak anti-interference ability,which are difficult to meet the requirements of modern analytical techniques.The magnetic beads based immunoassays can not only improve the detection sensitivity through the increasing of the immobilization capacity of the signal molecules,but also simplify the pretreatment process,shorten the immune reaction time and improve the anti-interference ability of the sensor.Therefore,immunomagnetic separation and signal amplification strategies were integrated with high sensitive detection methods such as liquid crystal based biosensors to meet the demand of point-of-carediagnosis.Several immunoassay methods with high sensitivity and strong anti-interference ability without the need of complicated instruments have been established,which were further applied to tumor markers detection.The detail contents are as follows:(1)A novel liquid crystal biosensors based on the integration of enzyme-induced metallization amplification and nanogold-induced silver deposition has been proposed for high sensitive detection of alkaline phosphatase(ALP),and it was further applied to visualized detection of carcinoembryonic antigen(CEA)with the combination of immunomagnetic separation.The AuNPs modified glass slides were used as the substrates,and the integration of enzymatic metallization reaction could induce the deposition of silver nanoparticleson the substrates effectively,which improved the detection sensitivity enormously.The use of magnetic beads as the reaction carrier of immunoassay can achieve the rapid isolation and enrichment of target tumor markers.As a result,the fouling and passivation of the liquid crystal sensing film by complex samples could be avoided,which improved the anti-interference ability of liquid crystal based biosensors greatly.The deposition of silver nanoparticles on the substratecan disrupt the arrangement of liquid crystal molecules and produce birefringence signals.As a result,the target analytes could be detected from the amount of the bright spots and color of the optical images under the polarizing microscope.A simple,sensitive and visualized detection method with good specificity and anti-influence ability was proposed,which presented a new signal-amplification approach for liquid crystal biosensors.(2)The chemiluminescence immunosensor based on the integration of immunomagnetic separationand enzymatic amplification for highly sensitive detection of CEA was fabricated in this work.The magnetic beads were used as the reaction carrier of the immunoassay and the horseradish peroxidase(HRP)was used as a signal tag,which formed immune complexes on the surface of the magnetic bead.The presence of HRP could catalyze luminol to generate chemiluminescent signal,as a result CEA could be detected with high sensitivity.The use of magnetic beads could amplify the detection sensitivity greatly.The detection limit of this method for CEA determination is as low as 4.5 pg/mL,This method not only provides a simple platform for the detection of CEA with high sensitivity and strong specificity,but also shows great potential in the early diagnosis of tumor diseases.(3)The gold nanoparticles(AuNPs)using glutathione as ligand was synthesized,which had good stability and biocompatibility.Then,a non-aggregation and colorimetric strategy based on metal nanoparticles for ascorbic acid(AA)detection was constructed by using the as prepared AuNPs as seeds and catalyst.The presence of AA could reduce Ag~+to Ag~0 on the surface of AuNPs,and the resulting color change of the detection solution and the absorbace of nanosilver at 410 nm was used for AA detection.This strategy combined the target-induced silver deposition reaction and the extraordinarily high molar extinction coefficient of silver nanoparticles,which ownshigh detection sensitivity and the detection limit was as low as 0.75?mol/L.In brief,a simple,fast and sensitive colorimetric assay for AA detection was proposed.This method was applied to AA detection in complex samples,which has a great prospect in bioanalytical applications. |
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