Design,Synthesis Of Bio-Based Matrix Composites And Analysis Their Anti-Microbial And Anti-Viral Activity

Plant disease control is one of the most important processes in plant production.With the advance of the crucial idea of green prevention and control of plant diseases,the strategies of plant disease prevention and control are constantly updated.Among them,the"new green pesticide"has become the core direction of green prevention and control of plant diseases.In this study,bio-based materials were modified by chemical surface modification technology,nanomaterial synthesis technology,and physical ef-fects to synthetic a series of antiviral and antibacterial bio-based composites for differ-ent kinds of pathogens and their causing diseases.By evaluating the antibacterial or an-tiviral effects of each material and their disease control ability,analyzing their action mechanism.We had demonstrated that the series of materials had high antiviral and an-tibacterial activity,and had promising application value,which could provide new strategies for the research and development of new and efficient green pesticides.Based on plant fungi and plant fungal disease,we selected Colletotrichum gloeo-sporioides Penz as the target and introduced a one-step strategy for synthesizing silver nanoparticles（A-AgNPs）from aldehyde group-modified sodium alginate（ASA）.This strategy can control the size of A-AgNPs from 6 nm to 40 nm by changing reaction temperature.Compared to naked n-AgNPs（n-AgNPs）,A-AgNPs were more stable and dispersive,and had higher broad-spectrum activity against plant pathogenic fungi.When the concentration of A-AgNPs was 0.08 n M,the inhibition rates of A-AgNPs on the growth of six plant fungal mycelia were 66.7%（Colletotrichum orbiculare）,100%（Sclerotinia sclerotiorum）,76.6%（Colletotrichum gloeosporioides Penz）,74.9%（Fusarium solani）,71.2%（Rhizoctonia solani Kuhn）and 97.4%（Sphaeropsidales）.The antifungal mechanism test showed that A-AgNPs can through changing cell membrane permeability,inhibiting the synthesis of soluble total protein,damaging DNA structure and inhibiting DNA replication to inhibit the growth of fungal mycelia.Finally,the A-AgNPs showed no inhibition of rice and N.benthamiana seed germination and did not affect the normal life activities of catfish.In summary,we believe that A-AgNPs have potential application value in plant fungal disease control..Based on plant oomycete and plant oomycete disease,we selected Phytophthora capsici（P.capsici）as the target.Herein,a new bio-based nano-antifungal material（CNC@CTAB）was made by coating hexadecyl trimethyl ammonium bromide（CTAB）on the surface of cellulose nanocrystal（CNC）and was applied in the prevention of P.capcisi.Compared to pure CTAB,CNC@CTAB performed a better anti-oomycete ac-tivity both in vitro and in vivo.When the CTAB concentration on the CNC surface was74.0μg/m L,the inhibition rate could be reached as high as 100%.And at the same con-centration.CNC@CTAB could completely inhibit the Phytophthora capsici infect pep-per leaves and corresponding disease index reached 0.Thus,considering CNC@CTAB’s inhibitory activity against Phytophthora capsici and its important characteris-tics of"reducing application and increasing efficiency",we believe that this bio-based nanomaterials can be regarded as a new green nano-fungicide to apply in the oomycetes disease control.Among plant bacterial diseases,we chose Ralstonia solanacearum（R.solanacea-rum）as the research target.And based on the soil p H change during the R.solanacea-rum growth,and p H sensitivity of the Schiff base structure,the oxidized alginate（OSA）was used to crosslink with adipic acid dihydrazide（ADH）and Ca²⁺to fabricated a p H sensitive oxidized alginate-based double-crosslinked hydrogel pesticide carrier.After adding the tetramycin,the carrier exhibited p H-dependent pesticide release behavior and activity against Ralstonia solanacearum.The results showed that the drug release rate and antibacterial activity were most prominent at p H 5（p H of the soil on which bacterial wilt was affected）.Further study also showed that the inhibition rate of the tetramycin loaded gel（82.4%）was higher than that of industrial pesticide difenocona-zole（66.7%）and pure tetramycin（70.3%）.The material can reduce the difficulty of drug application before the onset of R.solanacearum,and improve the prevention effi-ciency of R.solanacearum.Based on the plant viral disease,a dual-action pesticide-loaded hydrogel with the capacity to significantly induce plant resistance against TMV infection and promote plant growth was introduced.The alginate-lentinan-amino-oligosaccharide hydrogel（ALA-hydrogel）was synthesized by using electrostatic action to form an ami-no-oligosaccharide film on the surface of alginate-lentinan drug-loaded hydrogel（AL-hydrogel）.Fourier transform infrared spectrometry（FTIR）,the zeta potential test,scanning electron microscopy（SEM）and elemental analysis were used to characterize the hydrogel,confirming the formation of the amino oligosaccharide film.Pesticide re-lease experiments showed that the sustained-release time of ALA-hydrogel was more twice as long as AL-hydrogel.More importantly,ALA-hydrogel in soil could continu-ously induce plant resistance to against tobacco mosaic virus（TMV）in soil,and accel-erate the release of calcium ions to promote the growth of N.benthamiana.Meanwhile,the ALA-hydrogel maintained an extremely high safety to organisms.Our study provide a strategy that can replace the traditional approach of applying pesticide.In the future,this strategy will has good potential for agricultural production and plant protection ap-plications,and will be gradually valued owing to its simple synthesis method,green synthetic materials,and efficiency in the induction of plant resistance.In summary,based on the onset and pathogenic characteristics of the four major plant diseases,this study had designed and synthesized a sodium alginate-silver nano-particles（A-AgNPs）with high efficiency and broad spectrum antifungal properties,a bio-based nano anti-oomycetes agent（CNC@CTAB）with high anti-oomycete activity and low drug resistance,a p H-responsive,double-crosslinked pesticide-loaded hydrogel and a dual-action pesticide-loaded hydrogel with sustained induction of plant antiviral resistance and promotion of plant growth.More importantly,we had preliminary ex-plored the antimicrobial and antiviral activities of four composite materials,first expla-nation of the anti-phytopathogenic mechanism of silver nanoparticles（cell membrane angle）;reported on the application of CNC in plant disease prevention and control;based on the disease onset characteristics to build a p H-responsive drug carrier for ac-curate drug release;and by using the pesticide on the root to against plant virus.This work was to combine biological polysaccharides with traditional antiviral compounds through simple modification methods and synthesis process to improve or prolong their antiviral and antimicrobial ability,alleviate their damage to plants and the environment,and finally achieve the goal of green prevention and control of plant diseases.So,we believe that this strategy is helpful for the development of new high-efficiency green-friendly agricultural reagents,and has great reference and practical prospect.