| "Chemical nose" is a kind of array sensor with selectivity and cross-reactivity.Without the antibody or aptamer,"chemical nose" can control analyte-sensor interactions and create a unique pattern or fingerprint to discriminate a large number of analytes by changing and synthesizing the single molecular on the surface of materials.As a significant selective array sensor,"chemical nose" has been used for the detection of various small molecules(metal ions,volatile substances,amino acids)as well as organisms(cells,viruses)which possessing various types of biological macromolecules.In this study,one method for rapid detection of seven pathogenic microorganisms was established based on the "chemical nose" technique by three quaternized magnetic nanoparticles and urease;we also used the method where eleven pathogenic microorganisms were rapidly detected based on the system which consisted of a magnetically nanoparticle conjugated with three different fluorescent proteins.We further used the multichannel magnetically fluorescent nanosensor(dMFN)platform to produce patterns that identify eleven antibiotics.The main points of our work in theses were summarized as follows:1.Pathogenic microorganism detection using magnetic nanoparticle-urease nanosensor:it is known that the response intensity of the "chemical nose" sensor was dependent on the level of displacement determined by three quaternized magnetic nanoparticles-urease binding strength and pathogenic cells-nanoparticles interaction.Based on the ability of urease to hydrolyze urea and increase the pH value of the system,they can make the chromogenic reagent(urea-containing solution and phenol red)a color change from yellow to red.Therefore,different kinds of pathogenic microorganisms and different concentrations of microorganisms can lead different concentrations of urease being desorbed from the surface of magnetic nanoparticles,which resulted in the reactivation of urease hydrolysis activity.The color change of the solution(from yellow to red)can be judged by a microplate reader at a wavelength of 558 nm.After that,fingerprint can be differentiated by linear discriminant analysis(LDA)to diagnose the species and concentration of the pathogenic microorganism.Our approach has been used to measure bacteria with an accuracy of 97.6%for 1 × 104 cfu·mL-1 within 30 min.1 × 102 cfu ml-1 of bacteria could also be detected.2.Pathogenic microorganism detection using magnetic nanoparticle-fluorescent protein nanosensor:the quaternized magnetic nanoparticle was combined with three fluorescent proteins(blue fluorescent protein,green fluorescent protein,red fluorescent protein),and energy transfer from conjugation would quench the fluorescence of the fluorescent proteins.Upon interacting with different species and concentrations of bacteria,different levels of the three FPs can be displaced,which were dependent on the binding strength among quaternized magnetic nanoparticles,FPs and pathogenic cells.The excitation/emission wavelengths were 380/450,480/510,and 555/585 nm for BFP,GFP and RFP,respectively.The raw response data matrix was processed by linear discriminant analysis(LDA).The technique has been employed for bacterial identity with an accuracy of 89.7%for 5×106 cfu·mL-1 within 30min.The limit of detection for the sensor was 5×104 cfu·mL--for all eleven pathogens.3.Antibiotic Screening using magnetic nanoparticle-fluorescent protein nanosensor:representative gram-positive bacteria(Staphylococcus aureus)and gram-negative bacteria(Escherichia coli)treated with eleven antibiotics at their respective their half-maximal inhibitory concentrations(IC50).We further used dMFN platform for screening of antibiotics.Fluorescence response patterns can be obtained on the array and identified via linear discriminant analysis(LDA)and hierarchical clustering analysis(HCA).The canonical scores were obtained from LDA on the fluorescence responses with 97.6%(Staphylococcus aureus)and 95.2%(Escherichia coli). |
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