Research Of QCM Biosensor Based On Nanomagnetic Beads For Lead Ions

As the non-biodegradation characteristic,lead will be accumulated constantly once it was exposed to the environment.The harm of lead ions will be more serious with the increasing development of industry.Even a tiny amount of lead ions may cause mental retardation in children due to their special sensitivity to lead ions.Presently,many methods have been studied for lead ion detection,but the requirement for reducing cost,simplifying operation,improving selectivity and sensitivity of Pb²⁺detection is still a challenging research field.Quartz Crystal Microbalance（QCM）have attracted great attentions of researchers in various fields as the advantages of high sensitivity,low cost,reproducibility and so on.And they have great research potential in the detection of low concentration of lead.Nano-Magnetic Beads（NMBs）,which have the advantages of superparamagnetism,small size effect and easy separation,can be used for amplifying the detection signal to improve the sensitivity of biosensor.In view of these,our group innovatively combined the advantages of NMBs and QCM,and designed a simple and highly sensitive biosensor for the detection of lead ions.In our study,the catalytic chain（DNA1）of GR-5 DNAzyme was immobilized on the gold film surface of QCM electrode by Au-S bond.Substrate strand of GR-5 DNAzyme（DNA2）that combined with NMBs was hybridized with DNA1 through base pair complementary.In the presence of lead ions,DNA2 was specifically cut into two segments at the RNA site（rA）,which breaking off the hybridization.DNA2 and NMBs were separated from the DNA1 and detached from the QCM,causing a change in the mass on the QCM surface,which in turn caused a large change in the resonant frequency.Therefore,the concentration of lead ions can be detected by testing the frequency change values.In the experiment,we have determined different concentrations of lead ions using our biosensor.The results showed that a perfect linear relationship between the change values in frequency and the logarithm of the concentration of lead ions was obtained from 1 pM to 50 nM with the correlation coefficient value of 0.99634.Moreover,our biosensor have low detection limit of 0.3 pmol/L（S/N=3）and good specificity.In order to further validate the practical performance of our biosensor,we have tested the recoveries of our QCM biosensor with different concentrations of Pb²⁺in ultrapure water and Wahaha drinking water,respectively.The results showed average recoveries of 98.784±4.045%in ultrapure water and97.115±6.465%in Wahaha drinking water.And the errors are all acceptable.Compared with most existed methods,our biosensor were not only simple to operate,low in cost,but also have low detection limit and good specificity,and are expected to be used for the actual analysis of lead ions in drinking water.In addition,our design method provides a new idea for the research of the biosensors based on NMBs and QCM for other substances detection.