| The nano-biosensor technology offers a significant solution for food safety detection and early cancer diagnosis,which are two concerns in the society.In particular,DNA functionalized nanomaterials with high biocompatibility,large specific surface areas,high stability and short response time can largely improve the detection performance over the target substances.In this study,DNA functionalized quantum dots(QDs)were prepared and used to construct four types of food safety and cancer marker biosensors.The main contents are listed below.(1)A type of QD-DNA nanocomposite sensors was prepared by combining Mn-doped Zn S room-temperature phosphorescent(Mn-Zn S RTP)QDs with functional DNA-BHQ2.Then an RTP sensing system for trace detection of genetically-modified mark sequence cauliflower mosaic virus 35 S promoter(Ca MV 35S)DNA was built on basis of the phosphorescent resonance energy transfer(PRET).This sensing system had a detection limit of 4.03 n M and a detection range of 12-300 n M.The use of phosphorescence properties avoids the interference from the background fluorescence in biological samples and is very feasible for analysis and detection of Ca MV 35 S in biological samples.(2)The DNA complementary sequence of Ca MV 35 S was cut,designed and used to surface-modify Mn-Zn S RTP QDs.In this way,two types of DNA functionalized RTP QDs(P1 and P2)were prepared for the induced assembly and aggregation of the target substances.Based on the exciton energy transfer(EET)effect from small-size QDs to large-size QDs,an RTP QD EET phosphorescent nanosensor system was built for trace detection of Ca MV 35 S.This system had a linear range of 10-200 n M in detecting Ca MV 35 S with a correlation coefficient of 0.991,and a detection limit of(3?)0.48 n M.This easy and marker-free biosensor largely simplifies the RTP nanosensing system.(3)Since mi RNA21 is a marker of many human tumors,trace detection of mi RNA21 significantly contributes to early tumor diagnosis.A type of RTP nanocomposite materials was prepared by combining Mn-Zn S RTP QDs with functional ROX-DNA.The trace mi RNA-21 detection was realized on basis of PRET.This sensing system had a detection limit of 1.60 n M and a detection range of 8-80 n M.This sensing system did not need any complex preprocessing and avoided interference from the background fluorescence in biological fluids.Thus,it can be used to detect mi RNA-21 in biological fluids(serum),It provides a reliable method for early diagnosis of tumors.(4)A type of fluorescent biological QDs(Bio-dots)probe was prepared via a one-step hydrothermal method and starting from the TC-base-rich single-strand DNA(ss DNA).The fluorescence life of the Bio-dots was up to 10.7 ns and much longer than CQDs.The melamine in milk was identified and detected by using the base pairing principle.Under the optimal conditions,this Bio-dot fluorescence sensor in melamine detection had a linear range of 5-600 ?M and detection limit of(3?)1.4 ?M.The Bio-dots can emit fluorescence and function as a function identifying gene group.Moreover,the raw material ss DNA is basically nontoxic and the synthesis process does not involve other toxic substances.Thus,the Bio-dots are green and environmental-friendly luminescnet functional materials.In conclusion,4 types of biosensors were built by preparing DNA functionalized RTP and fluorescent QDs,and can be used to detect representative food safety and cancer-related substances.The principle of DNA base pairing in biology can be used to construct PRET system,Moreover,this study expands the application of nanosensors into the field of biosensors and offers a new way for detecting food safety and cancer-related substances in real biological samples and for developing novel DNA functionalized QD sensors. |
PDF Full Text Request