Preparation Of CDs Fluorescent Probes From Coffee Grounds And Its Application In The Rapid Detection Of VB₁₂ In Serum

Objective:The processing residues of food and agricultural products were used as the raw materials of carbon quantum dots（CDs）,and suitable carbon precursor materials were selected to synthesize CDs.Based on the CDs,a fluorescence probe was established to detect VB₁₂ quickly and sensitively,and was applied to the rapid detection of VB₁₂content in the serum samples.And then verified the sensitivity,specificity and precision of the probe,and the practicability and reliability of the probe in the field of biological sample detection were also explored.Methods:By judging fluorescence intensity,excitation wavelength,fluorescence quantum yield（QY）and the quenching efficiency of VB₁₂ to screen the best precursor materials for constructing probes.The biochar prepared under vacuum and high temperature was used to extract CDs by ultrasonic pyrolysis,and different synthesis conditions were optimized to construct fluorescent probes and methods for detection.Designing VB₁₂ as the target analyte;Using TEM,FTIR,X-ray diffraction and other series of characterization methods to characterize the obtained CDs,and the interaction and quenching mechanism between VB₁₂ and CDs were discussed.The probe was used for the determination of medical VB₁₂injection,and the results were compared with the national standard method"GBT5009.217-2008"to verify the precision and accuracy of the method.The probe was further applied to the VB₁₂detection and recovery experiments in actual serum（rat and human）sample,and the detection results of human serum were combined with dietary intake,clinical symptoms and diagnosis results to determine the risk of insufficient VB₁₂ intake,meanwhile,Verified the reliability of the CDs probe method.Results:It was found that coffee grounds（CG）were relatively good precursors of CDs,and the prepared coffee grounds CDs（CCDs）had the characteristics of smaller size（0.86-4.56nm）,uniform dispersion,high fluorescence intensity（>750a.u）,good stability and biocompatibility.Applied with the unique fluorescence quenching effect of VB₁₂ on CCDs,a VB₁₂ detection method was successfully established using CCDs as the probe.The linear range of the method was 10 ng/m L～1×10~6 ng/m L,R~2=0.9982,and the LOD was 0.61 ng/m L.In the detection of actual samples of medical VB₁₂ injection,compared with the national standard method,the detection result of this probe method was closer to the actual concentration of the sample,and the RSD value（0.12%～1.21%）was better than the RSD detected by the national standard method.（0.67%～1.88%）;And in the detection of rat serum and the serum of pregnant who suffered from the megaloblastic anemia（MGA）,the probe showed the characteristics of wide detection range,high recovery rate,low detection cost,faster detection time,high reliability、sensitivity and specificity.Conclusions:Successfully synthesized CDs with CG,and the probe detection method established by using CG as a probe.In the actual sample VB₁₂ detection,it has low detection cost,short detection time,wide detection range,and high sensitivity.The excellent characteristics of strong specificity and reliability can realize the popular and dynamic detection of VB₁₂ content in different populations at different ages and physiological stages,and further optimize it can be used as a detection method for biological samples in the future.