聚丙烯酰胺季铵盐大分子药物的环境毒性评价及其实验设计

Environmental toxicities evaluation and experimental design of polymeric drugs based on polyacrylamide quaternary ammonium salts

聚丙烯酰胺季铵盐(PAM-QAS)是丙烯酰胺(AM)与丙烯酰胺季铵盐(AM-QAS)的无规共聚物,因兼具聚丙烯酰胺的土壤改良特性和大分子季铵盐的抑菌特性,在抑制土壤病原真菌、改良和修复病土等领域有良好的应用前景。但人们对季铵盐具有较高环境毒性的传统认识,极大地限制了这类新型大分子药物的应用。如何结合PAM-QAS的应用环境,综合、客观地评价其环境毒性,是大分子药物设计和应用中亟待解决的问题。通过在PAM-QAS中修饰荧光基团直观地观察其在土壤中的吸附与淋溶特性,以及结合土壤吸附和淋溶实验用鱼类经口急性毒性实验和蚯蚓毒性实验评价PAM-QAS经土壤吸附后的实际环境毒性,为PAM-QAS的田间应用提供了一定科学依据。该实验内容涉及聚合物结构表征与应用、大分子药物在复杂环境下的定性检测,以及药物的环境毒性评价等诸多环节,具有一定的综合性与探索性,有利于提高学生的综合素质、科研能力和创新能力。

[Objective]Because of the huge damage caused by soil-borne fungal diseases in agriculture,polyacrylamide quaternary ammonium salts(PAM-QAS)have been introduced to control soil-borne fungal diseases,such as banana Fusarium wilt,which is caused by Fusariumoxysporum f.sp.cubense(Foc).As a random copolymer of acrylamide and acrylamide quaternary ammonium salt,PAM-QAS shows significant improvement properties on soil and good antifungal activities against soil-borne fungal diseases,such as Foc.Thus,PAM-QAS has a good application prospect in the control of soil-borne fungal diseases and improving soil.However,traditional small molecular quaternary ammonium salts have been well-known to show high environmental toxicities,greatly limiting their application.Thus,visually evaluating the environmental toxicities of PAM-QAS based on exact application environments has become an urgent issue in the design and application of PAM-QAS.In this work,multiple experiments were designed to visually demonstrate the low environmental toxicity of PAM-QAS.[Methods]To visualize PAM-QAS,a very small amount of a fluorescent group(FL)was introduced into PAM-QAS to obtain fluorescent-labeled PAM-QAS(PAM-QAS-FL).Thus,its adsorption and leaching characteristics in soil could be observed intuitively.From the soil adsorption and leaching experiments,the actual environmental toxicities of PAM-QAS after soil adsorption could be evaluated using fish oral acute toxicity and earthworm toxicity experiments,which gave a good perspective for the field application of PAM-QAS.[Results]The soil adsorption and leaching experiments intuitively showed that under an application rate of 0.6 g per kilogram of dry soil in the field,which was about three times the commonly applied amount,PAM-QAS-FL could be stably adsorbed and retained in the soil,with only a few free PAM-QASs leaching into environmental water.Thus,the impact of PAM-QAS on the environment could be greatly reduced.The fish acute toxicity of simulated rain leaching solution containing PAM-QAS and soil(LC50L),the fish acute toxicity of a suspension containing PAM-QAS and soil(LC50S),and the earthworm toxicity of PAM-QAS(LC50)were all higher than 600 mg per kilogram of dry soil.Meanwhile,the LC50L,LC50S,and LC50(earthworm)for small molecule quaternary ammonium salt(benzalkonium chloride(BC))were about 70,150,and 150 mg per kilogram of dry soil,respectively.These results demonstrate that compared with BC,the environmental toxicity of PAM-QAS is significantly reduced,and it is safe for both fish and earthworms.[Conclusions]By simulating the effects of drugs infiltrating groundwater with rainwater and mixing with soil and water in practical production applications,LC50L and LC50S were introduced to evaluate the fish toxicity of soil leaching solutions and water/soil/drug mixtures,respectively.A more accurate environmental toxicity assessment method for PAM-QAS was thus established.This work covers several aspects,such as structure characterization and application of functional polymers,qualitative detection of polymeric drugs in complex environments,and environmental toxicity evaluation of drugs.It is comprehensive and exploratory to a certain extent and is conducive to improving students'comprehensive quality,scientific research,and innovation ability.