Iron Oxide Magnetic Nanoparticles Exhibiting Zymolyase-like Lytic Activity

Iron oxide magnetic nanoparticles(Fe3O4 MNPs)as a typical nanozyme exhibit superiority over natural enzymes in terms of low synthesis cost,ease of bulk production,reusability,high stability and tolerance to harsh operational and storage condition.Although much progress has been made to explore the Fe3O4 MNPs for various biocatalytic activities and corresponding applications,few studies reported lytic activity.In this paper,the Fe3O4 MNPs were synthesized by co-precipitation method and were then employed to catalyze the disruption of yeast cells,the following is a detailed study:The second chapter of this paper,ferrous chloride,ferric chloride as raw materials,sodium hydroxide as precipitant,through the chemical co-precipitation method to prepare Fe3O4 MNPs.And their crystal structure,chemical composition and morphology were characterized by using X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM)and high-resolution transmission electron microscopy(HRTEM).The results show that the spherical morphology Fe3O4 MNPs with a diameter of about 17.7 nm and a specific surface area of 100.6× 0.3m2·g-1 was synthesized successfully.The third chapter of this paper,Fe3O4 MNPs was used as biocatalyst to disruption Saccharomyces cerevisiae cells,and the following experimental results were obtained:1)The lytic activity of Fe3O4 MNPs was studied by UV-Vis spectrophotometer.The results showed that at 25? and pH=7.5,Fe3O4 MNPs could almost completely lyse cells within 10 min.The lytic activity of Fe3O4 MNPs was better than that of nature zymolyase.2)The reaction kinetics of Fe3O4 MNPs was studied under different concentraction of Saccharomyces cerevisiae cells.The results showed that the kinetic equation of Fe3O4 MNPs was in accordance with the typical Michaelis Menten equation.By drawing the double reciprocal curve,the apparent kinetic parameter Km was obtained,which was 4.94 × 104 cfu·mL-1.The results indicated that Fe3O4 MNPs had a high affinity with Saccharomyces cerevisiae cells.At the same time,Kcat/Km=15.2 L·mol-1·h-1,Kcat=7.53 × 105 cfu·mol-1·h-1 were obtained,which confirmed the activity of the synthesized Fe3O4 MNPs.3)The effent of different temperature and pH on the activity of Fe3O4 MNPs was studied.When the temperature increased from 25? to 60?and the pH changed from 4 to 10,the Fe3O4 MNPs maintained a good stability.The activity of the iron ion leaching solution was studied in different pH ranges.The results showed that the leaching solution of iron ion had no lytic activity,indicating that the lytic activity was all from Fe3O4 MNPs.4)The reusability of Fe3O4 MNPs was studied in PBS and water,and the activity of the first cycle was taken as 100%.The results showed that after the Fe3O4 MNPs was stored in the two solvents for 20 h in the second cycle,the Fe3O4 MNPs maintained 80%of the initial activity,and still had a good activity in the third cycle.It shows that Fe3O4 MNPs has the performance of repeated use.5)Since zymolyase have basic proteases and ?-1,3-glucanase,the production of Fe3O4 MNPs was discussed.The results showed that Fe3O4 MNPs did not have the lytic activity of these two enzymes,indicating that the special lytic mechanism of Fe3O4 MNPs is worthy of further study in the future.