Construction And Performance Study Of Nano Drug-loaded System Based On Lignin Piperidine Amine

How to reduce the amount of pesticides and improve the utilization rate of pesticides has been a big problem that puzzles pesticide preparations in China.Nano-pesticide has the characteristics of fine particles,wide coverage area per unit drug quantity and high theoretical efficacy,which is a potential solution.However,the specific surface area of nano-pesticide particles is large,and the pesticide particles are in full contact with the air after application,which is easy to be oxidized and decomposed under the sunlight,and the duration of efficacy is short.In this paper,a novel nano-microemulsion was constructed by using piperidyl amine grafted alkali lignin as the drug-loaded material and two original drugs,avermectin and emamectin benzoate which are easy to photolysis as the research objects.The aromatic ring structure of lignin was used to form hydrophobic micro zone to encapsulate the original drug and the phenolic hydroxyl group of lignin and the introduced piperidyl amine structure could protect the original drug from oxidation and photolysis.The nano-microemulsion constructed in this paper has the function of slow-release,and has the obvious protective effect on the photodegradable original drug.Lignin piperidyl amine(Temp-AL)was synthesized by Mannich reaction using alkali lignin(AL)and 4-amion-2,2,6,6-tetramethylpiperidine amine(Temp)as material.Temp-AL were characterized by elemental analysis,infrared spectroscopy,nuclear magnetic hydrogen spectroscopy and electron paramagnetic resonance,which proved that Temp group was successfully grafted into AL molecules.Then Temp-AL and cetyltrimethylammonium bromide(CTAB)were used for electrostatic self-assembly,and long-chain alkyl was introduced into the molecule of Temp-AL to improve the compatibility of Temp-AL with original drug and solvent,and lignin piperidyl amine/CTAB self-assembly product(Temp-AL/CTAB)was obtained.Temp-AL/CTAB was characterized by elemental analysis,infrared spectroscopy,nuclear magnetic hydrogen spectroscopy and electron spin resonance,which proved that CTAB and Temp-AL were successfully self-assembled.Using Temp-AL/CTAB as drug-loaded material,the formulation of the photosensitive pesticide avermectin(AVM)was studied to prepare 1.8% AVM nano-preparation(AVM@Temp-AL/CTAB),and the particle size distribution of drug-loaded microspheres in nano-preparation was 185-219 nm.AVM@Temp-AL/CTAB was characterized by scanning electron microscopy(SEM),thermogravimetric(TG),elemental analysis(EA),and X ray photoelectron spectroscopy(XPS).The results show that the prepared drug-loaded nanospheres have the structural characteristics of AVM mainly distributed in the interior,Temp-AL/CTAB mainly in the outer layer,and are solid microspheres with regular shape.The stability experiment shows that the nano-preparation has good storage stability,and the increase of Temp group content in drug-loaded materials helps to improve the chemical stability of AVM in thermal storage.The sustained release experiment shows that the cumulative release of AVM in the nano-preparation at 72 h was 52.75%,showing a sustained release.The photolysis experiment shows that the half-life of AVM in nano-preparation reached 240.2 h,which was 9.13 times that of the original drug(26.3 h).The affinity experiment of nano-preparation to the target shows that the affinity and adhesion of lignin-based nano-preparation to epipremnum aureum and cabbage leaves are superior to those of traditional microemulsion(C-AVM/ME),and the adhesion of the liquid on the surface of the target is larger,and the scour-resistance performance is stronger.Using Temp-AL/CTAB as drug-loaded material,the formulation of the photosensitive pesticide emamectin benzoate(EMB)was studied to prepare 1.8% EMB nano-preparation(EMB@Temp-AL/CTAB),and the particle size distribution of drug-loaded microspheres in nano-preparation was 237-293 nm.After 14 days of thermal storage experiment,the particle size of nano-preparation increased within 30 nm,and the physical stability are excellent;the decomposition rates of origin drug were less than 5%,and the chemical stability are good,and the increase of temp group content in drug-loaded material is helpful to improve the chemical stability of EMB in thermal storage.The prepared nano-formulation exhibits controlled-release performance,and the cumulative release amounts ranged from 56.27% to 87.33% at 62 h,and it decreased first and then increased with the increase of Temp-AL/CTAB dosage.After UV irradiation for 50 hours,the retention rates of EMB in the nano-preparation ranged from 69.68% to 83.67%,which was 2.27?2.73 times higher than that of the blank sample.The affinity experiment of nano-preparation to the target shows that the affinity and adhesion of lignin-based nano-preparation to epipremnum aureum and cabbage leaves are superior to those of traditional microemulsion(C-EMB/ME),and the adhesion of the liquid on the surface of the target is larger,and the scour-resistance performance is stronger.Temp-AL/CTAB was used as the drug-loaded material to prepare pesticide nano-preparation for AVM with strong hydrophobicity and EMB with strong hydrophilicity,respectively.It was found that the two pesticides nano-preparation show good comprehensive performance.However,the hydrophobicity of the original drug has a certain influence on the properties of the nano-preparation.The stronger the hydrophobicity of the pesticide is,the particles of the original drug tend to be distributed inside the microsphere,and the closer the microsphere structure is,the better the release performance of AVM is,and the release rate and cumulative release amount of the active component are less than that of EMB;The dispersion of AVM has more transparent appearance and better dispersing stability;AVM has a stronger slowing effect on the photolysis rate of the active component and a more significant anti-photolysis effect.