| As a substitute of traditional QDs,Carbon quantum dots(CDs)with a diameter<10 nm are extensively used in optical biological sensors due to their unique optical properties,low toxicity,and biocompatibility.However,the majority of directly obtained CDs are limited by low fluorescent quantum yields(FLQY<50%)and the consequent low detection sensitivity.For this reason,we doped N atoms containing quinquevalent electrons into the CDs,forming N-doped CDs to improve the FLQY.However,CDs cannot specifically select targets.Surface-functionalized CDs with specific recognizers are usually utilized to specifically identify targets.The supramolecular compound?-cyclodextrin(?-CD),a water-soluble,biocompatible,and nontoxic ring-shaped oligosaccharide,is polymerized from one 1,4-glucosidic bond and 7 D-pyran glucoses.Which is possesses both hydrophobic inner cavity and hydrophilic outer environment.The hydrophobic cavity of?-CD enables organic substances,inorganic materials,and biological object molecules with appropriate sizes to be selectively coated through physical and chemical forces,forming stable host–guest inclusion complexes,such as ferrocene and adapters.However,the chemical inertia of?-CD complicates the qualitative or quantitative analysis of the substances that get into the cavity of?-CD.Nevertheless,?-CD functionalized CDs that integrate the properties of supramolecular compounds and the nanometer properties of CDs can be prepared.Molecular recognition and qualitative or quantitative detection can be achieved through the photoinduced electron transfer(PET)of CDs and the specificity of?-CD host–guest recognition.Inspired by these analyses,we used mono(6-amido-6-deoxy)-?-cyclodextrin to functionalize N-doped CDs and synthesized a novel fluorescent nanoprobe that has the fluorescent characteristics of CDs and the specificity of?-CD host–guest recognition,which were used to sensitively detect Target analyte.Moreover,the applicability into real samples was analyzed.1.An easy,dependable,and sensitive cholic acid activity experiment was designed based on?-cyclodextrin-modified carbon dot(?-CD-CD)nanoprobes with specific host–guest recognizing ability and photoelectron transfer capability.The?-CD-CD nanoprobes were characterized by infrared,ultraviolet-visible,and fluorescence spectroscopy and transmission electron microscopy.The fluorescence of the probes under optimized conditions linearly responded to cholic acid concentration from 0.2 to 650?mol·L-1 with a detection limit of 25nmol·L-1.The probes also performed well in detecting cholic acid in serum and urine samples with an average recovery rate of 97.1%–103.4%.Thus,this study provides a reliable,rapid,and easy method of cholic acid detection in body fluids that can be potentially applied in medical studies.2.A novel fluorescent nanometer biosensor integrating a?-cyclodextrin-modified carbon dot(?-CD-CD)fluorescent nanoprobe and ferrocene-marked adapter(ss DNA-Fc)was developed and used to measure platelet-derived growth factor(PDGF)-BB.When no PDGF-BB was added,ss DNA-Fc induced the enhanced fluorescence of?-CD-CD nanoprobes.After adding PDGF-BB,ss DNA-Fc specifically bonded with PDGF-BB.Meanwhile,the?-CD-CDs and Fc in ss DNA-Fc initiated host–guest identification,which then induced photoinduced electron transfer and decreased fluorescence,thereby contributing to the high-sensitivity monitoring of PDGF-BB.This novel approach showed a wide linear range of 10 pg·m L-1 to 8?g·m L-1 and a low detection limit of 6 pg·m L-1(RSD=±4.6%).Moreover,the spiked recovery rate in human serum was 98.2%–106.2%(RSD?±3.79%),indicating that this method can be used to monitor PDGF-BB in human serum.3.Fluorescence quenching induced by exonuclease,specific target recognition by an aptamer,and host–guest recognition were artfully integrated in this study,and a novel nanoscale fluorescent aptasensor for supersensitive detection of acetamiprid was proposed.In the absence of acetamiprid,the aptamer hybridized with complementary DNA at3'end-marked ferrocene(Fc)(c DNA-Fc)to form a double-stranded DNA.Fluorescence intensity was nearly unchanged after Rec Jf exonuclease was added.In the presence of acetamiprid,the aptamer preferentially bound with acetamiprid to form an aptamer–acetamiprid compound;hence,the aptamer could not bind with c DNA-Fc.The single-stranded aptamer and c DNA-Fc were cut off after Rec Jf exonuclease was added,and the Fc released via host–guest recognition rapidly entered the cavity of cyclodextrin and initiated photoinduced electron transfer.Consequently,fluorescence intensity decreased,and acetamiprid was sensitively detected.Under optimal conditions,the intensity of the fluorescence signals was linearly related to target concentration and had a detection range of5 nM–1.2?M and a detection limit of 3 nM(relative standard deviation:±3.9%).The spiked recovery rates obtained from honey and orange juice samples were high.Despite the new method's low cost and simple operation,it presents a satisfactory detection limit,linear range,selectivity,and real sample detection capability.Thus,the method can be extensively applied to detect various pesticides or additives in agriculture and forestry. |
PDF Full Text Request