Synthesis Of Metal-based Nano-drugs And Evaluation Of Their Anti-PRRSV And Antibacterial Biological Effects

Porcine Reproductive and Respiratory Syndrome(PRRS)is an immunosuppressive disease caused by Porcine Reproductive and Respiratory Syndrome Virus(PRRSV).PRRS is a highly lethal immunosuppressive disease caused by the Porcine Reproductive and Respiratory Syndrome virus(PRRSV),which has a specific host in pigs.Although PRRSV has evolved to be significantly less virulent,it is still one of the major causes of economic losses in the livestock industry.As China is not only the world’s largest pork producer but also the world’s largest pork consumer market,the current means of preventing and controlling PRRS are mainly through the administration of traditional inactivated and modified live virus vaccines and the feeding of anti-inflammatory drugs;however,these methods have only been partially effective in disease control.Currently,metal-based nanomedicines synthesised by biomolecular templates have attracted widespread interest in the biomedical field due to their controllable size,fluorescence tunability,good biocompatibility,and significant antiviral activity.Based on this current situation,this thesis combines the experience of the precious metal nanoclusters designed in our laboratory with their biological effect evaluation to design and synthesize gold cluster-based drugs with high efficiency in the inhibition of PRRSV,characterize and evaluate the material’s physical and chemical properties and biosafety,and finally validate the material’s viral inhibition effect.The bismuth-based drugs with high biosafety and specific bioactivity were also synthesized using the functional peptide GSH as a template,and their physicochemical properties,antiviral effects,and bacterial inhibitory biological effects were investigated.The development of PRRSV drugs with single-stranded positive RNA genetic information has important implications for the prevention and treatment of coronaviruses with the same single-stranded positive RNA.The main research elements of this topic are specified as follows:1.Synthesis of anti-PRRSV active gold nanoclusters and evaluation of their antiviral effectsIn this thesis,the CY functional peptide,which has been screened for its specific targeting function against PRRSV,was used as a template for the synthesis of gold clusters(CY-Au NCs)with specific biological effects.The physical and chemical properties and molecular composition of CY-Au NCs were first characterised: the morphological dimensions of CY-Au NCs were characterised by high-resolution transmission electron microscopy with dynamic light scattering;the fluorescence properties of the materials were determined by fluorescence spectrophotometry;the UV-visible absorption spectra of CY-Au NCs and CY peptides were collected by UV-visible spectrophotometry to analyse the optical absorption properties;the experiments were carried out by Fourier transform infrared spectrophotometer to initially investigate the changes in the functional groups of CY peptides before and after the reaction;MALDI-TOF-MS was used to characterize the molecular composition of the materials and clarify their structural composition.Secondly,the experiments were carried out to investigate the effect of the gold cluster drug on cell viability by CCK-8 kit assay experiments and to find out the maximum tolerated drug concentration of the experimental cells.Thirdly,the effect of the antiviral activity of the drug was verified: the experiments were carried out to investigate the effect of the drug on the inhibition of virus adsorption,replication,inactivation and treatment by means of molecular biology such as PCR and q RT-PCR.The results of the experiments show that the prepared gold clusters have precise molecular composition and good fluorescence properties,while the results of the antiviral experiments show that the prepared gold cluster drugs are effective in inhibiting the adsorption and replication of viruses,and have significant effects in inactivation and infection treatment.The experiments were carried out to lay the foundation for further investigation into the mechanism of action of the drugs.2.Synthesis of small-sized bismuth nanodrugs and evaluation of their anti-PRRSV and antibacterial activitySmall-sized bismuth nanodrugs(GSH-Bi NPs)were synthesized by optimizing experimental conditions using glutathione(GSH),which has special biological activity,as a template,and their biosafety,antiviral,and antibacterial effects were initially evaluated.The effects of factors such as p H,synthesis temperature,reaction time,and different material ratios on the preparation and preservation of the materials were investigated.The morphological dimensions of the bismuth nanodrugs were characterized by high-resolution transmission electron microscopy with dynamic light scattering.The effect of different concentrations of GSH-Bi NPs on cell viability was also investigated by CCK-8 kit assay experiments combined with hemolysis experiments to preliminarily evaluate their biosafety.The antiviral effect of GSH-Bi NPs was initially determined by an indirect immunofluorescence assay.In order to investigate the antibacterial activity of GSH-Bi NPs in vitro,the inhibition effect of the materials against S.aureus,E.coli,and rice blast was investigated by an in vitro concentrationdependent inhibition assay and a bacterial plaque assay.The experimental results showed that the GSH-Bi NPs were small in size and well dispersed,and the bismuth nano-drugs maintained good stability after ultrafiltration with 0.9% Na Cl solution.They also had good biosafety and certain antiviral and antibacterial effects.