Construction Of Molybdenum Disulfide-based Sensing Interfaces And Their Application In The Detection Of Exosome

Gastric cancer is one of the most common cancers in the world,which has seriously threatened human health due to its high mortality rate.In order to effectively prolong the life of gastric cancer patients,how to achieve early detection and diagnosis of gastric cancer has become an urgent problem.Tumor-associated biomarkers can provide accurate information about the occurrence and underlying mechanisms of cancer,which is considered as promising molecules for early diagnosis of gastric cancer.Compared with traditional biomarkers,exosome vesicles have phospholipid bilayer structures,which can effectively protect the contents of the vesicles（such as DNA,RNA,proteins,etc.）from being degraded by various extracellular enzymes.Therefore,it is considered as one of the promising tumor biomarkers for disease diagnosis.Biosensor is one of the effective means for highly sensitive detection of exosomes due to their low cost,easy operation,high sensitivity and good selectivity.To efficiently improve the sensitivity and stability of biosensors,a popular method is introducing nanomaterials with large specific surface area,high biocompatibility,and easy surface functionalization into the construction of biosensors.Based on this concept,this thesis employed graphene-like molybdenum disulfide nanosheets as material unit to develop high-performance molybdenum disulfide-based nanocomposites through chemical synthesis.Subsequently,biosensors are designed for exosomes detection with high-performance based on the developed nanocomposites.The thesis is mainly divided into the following two aspects:1.A surface-enhanced Raman scattering（SERS）biosensor for highly sensitive detection of exosomes was developed based on gold nanostars-functionalized molybdenum disulfide nanocomposites（MoS₂-AuNSs）.The ROX-labeled aptamer（ROX-Apt）was immobilized on the surface of MoS₂-AuNSs nanocomposite through hybridization reaction to construct a nanoprobe,which can specifically detect exosomes.Due to the synergistic enhancement effect of AuNSs and MoS₂,the Raman signal of ROX can be significantly enhanced.At this moment,the SERS signal is the strongest.It should be noted that aptamers is used to specifically bind to exosomes.With the added of exosomes,ROX-Apt specifically binds to exosomes by recognizing the exosome surface transmembrane protein CD63.A ROX-Apt-exosome complex was formed and released from the surface of the nanocomposite,resulting in the decrease of the SERS signal.As expected,the designed SERS biosensor could detect exosomes in the range of 5.5×10¹-5.5×10⁵ particles/μL with a detection limit of 17 particles/μL.In addition,the biosensor also exhibited good selectivity and acceptable practical detection capability,indicating it has a great potential for exosome detection in biological samples.2.An electrochemical biosensor for label-free detection of exosomes was developed based on molybdenum disulfide-based multilayer nanoprobes.On the basis of our previous research work,we further introduced the electrochemical indicator thionine（Thi）into the construction of a molybdenum disulfide-based multilayer nanoprobe（MoS₂-AuNPs-Thi）.Subsequently,anti-CD63aptamer was assembled on the surface of the multilayer nanoprobe via Au-S bond to specifically recognize the transmembrane protein CD63 on the surface of exosomes,which was used to specifically capture and detect exosomes.In the presence of exosomes,a classical"sandwich"structure was formed on the electrode surface through the reaction of MoS₂-based multilayer probes,exosomes and probe DNA,leading to a"signal-on"detection mechanism.Compared with single-layer nanoprobes,multilayer nanoprobes can load more electrochemical signal molecule thionine（Thi）,which greatly enhances the electrochemical signal.As a result,the designed biosensor has a wide detection range（5.5×10¹-5.5×10⁶ particles/μL）and low detection limit（23particles/μL）for exosomes detection.Selective experimental result showed that our proposed detection strategy can well distinguish gastric cancer patients from healthy individuals,further demonstrating that the designed sensor is a promising method in clinical diagnosis.