Fluorescence Biosensor Based On Functional Nanomaterials And Its Application In The Detection Of Disease Markers

With the increasing attention to people’s health problems,the early detection and diagnosis of diseases have attracted more and more attentions.The detection of disease markers plays a vital role in disease discovery and diagnosis,but clinical detection methods are generally complicated and expensive.Biosensor is a good candidate for detecting disease markers in a simple way.Most of the developed biosensors can be used to detecte disease markers,however,due to the high requirements of early diagnosis and the complexity of biological environment,the developed biosensors are still insensitivity and inaccuracy.So it is necessary to construct some easy,inexpensive and accuracy biosensors with high sensitivity.At present,there are two main methods for improving biosensor sensitivity:（1）using some functionalized nanomaterials to amplify the detection signal.（2）using some strategies to reduce the background signal.Increasing the accuracy of the biosensor can be achieved by using the ratio method.Based on the reported literatures about new nanomaterials,the specific contents are summarized as follows:（1）In chapter 2,the manganese dioxide（MnO₂）nanosheets with high quenching rate are used to reduce the background signal to improve the sensitivity of the detection of trypsin.A novel“turn-on”fluorescent trypsin detection platform based on carbon dots-MnO₂（CDs-MnO₂）nanocomposites and ascorbic acid-loaded apoferritin（APOAA）was fabricated.By adjusting the pH,ascorbic acid（AA）was encapsulated in the cavity of trypsin-sensitive apoferritin.As a super quencher,MnO₂ nanosheets can effectively quench the fluorescence of CDs and reduce the background fluorescence to a lower level.The trypsin can cleave APOAA to release AA,AA can disintegrate MnO₂ nanosheets to recover the fluorescence of CDs.The sensitive detection of trypsin was relized by measuring the fluorescence fluctuation of CDs.An excellent performance and high sensitivity of trypsin determination were observed with a detection limit（LOD）of 0.3411 ng/mL.This work provides us with a unique strategy for trypsin detection in human serum samples,which reveals the potential applications in clinical detection.（2）In chapter 3,the ratio strategy is adopted to reduce the interference signal and improve the accuracy and sensitivity of detection.A dual emission ratiometric fluorescence sensor was constructed for the sensitive and accurate detection of copper ions.In this experiment,gold nanoclusters（AuNCs）and N-doped carbon quantum dots（CDs）were encapsulated into ZIF-8 accroding to one-pot method to fabricate the double-emission fluorescent probe（CDs/AuNCs@ZIF-8）.The probe was used to detect Cu²⁺based on the fact that Cu²⁺can quench the fluorescence of AuNCs and has no effect on the fluorescence of CDs.The ratiometric detection of Cu²⁺is achieved by measuring the ratio of fluorescence intensity of AuNCs and CDs.This ratiometric fluorescent sensor exhibits excellent sensitivity and selectivity for Cu²⁺with a linear range of 1 nM-1 mM and detection limits as low as 0.3324 nM.Compared to the conventional single-emission fluorescent sensors,the accuracy and sensitivity of this dual emission ratiometric fluorescence sensor are greatly improved.（3）In chapter 4,the mesoporous silicon（MSNs）with high loading rate is used to amplify signal for the sensitive detection of glutathione（GSH）.In detail,glucose was loaded into the pores of MSNs.Negatively charged MnO₂ nanosheets were assembled on the MSNs through electrostatic interactions.The nanosheets were reduced by GSH,which results in the release of glucose.The released glucose was merasued by the commercial personal glucose meter.GSH can be quantified by this method in the 100nM to 10μM concentration range,with a 34 nM limit of detection.This method was applied to human serum samples,and satisfactory results were also obtained.That reveals the sensor has a large practical application prospect.