Study On Smart Responsive Modified Lignin-based Nano-micelles For Drug Delivery

Lignin is an amorphous natural polymer.It is widely found in the xylem of herbs and woody plants.It is the second abundant renewable natural resource in the world.There are abundant active groups in the structure of lignin,such as hydroxyl,carbonyl,carboxyl,etc.,which make lignin easy to be modified,hence lignin can be endowed with the characteristics of modified segments,and become more versatile.Therefore,modified lignin-based nano-micelles can be prepared through the chemical modification of lignin based on its structural and chemical composition characteristics,which is helpful to broaden the high value utilization of lignin.In this paper,lignin was modified and highly active reaction sites were introduced.Then,two kinds of intelligent responsive nano-micelles were prepared by using two design ideas,and their applications in biomedical field were explored.(1)pH-responsive drug-carrying micelles.Acryloylated lignin(AAL)was prepared by the modification of lignin with acrylyl chloride.Then,AAL-g-MAA copolymer was prepared by graft copolymerization of AAL with methacrylic acid(MAA).Finally,pH sensitive nano-micelles were prepared by solvent exchange method.The structure of the polymer was characterized by 1H NMR,Fourier transform infrared spectroscopy(FTIR)and GPC.The self-assembled micelles were characterized by transmission electron microscopy(TEM)and Malvin laser particle size analyzer(DLS)to determine the shape,size and Zeta potential of the micelles at different pH values.The results showed that the AAL-g-MAA micelles were spherical and the particle size was about 50 nm.The particle size of micelles decreased with the increase of dripping speed and increased with the increase of initial concentration.In addition,the micelles had good stability.The particle size did not change obviously after standing for 3 days.Zeta potential test showed that the micelles had zero potential point between pH 3 and 4.Use it for ibuprofen(IBU)loading,the encapsulation rate of micelles reached 78.1%.In addition,drug release from the AAL-g-MAA@IBU micelles could be controlled by altering the pH values.At pH 1.5,the release of IBU was only 15.82%after 72 h,and at pH 7.4,the release of IBU was 92.31%within 72 h.In vitro cell experimental results showed that AAL-g-MAA micelle had no cytotoxicity on normal cells(hBMSC and NIH-3T3),but had obvious anti-proliferation effect on human colon cancer cells(HT-29).When the dose of AAL-g-MAA micelle was 0.3 mg/mL,the survival rate of HT-29 cells was only 42.8%,while the cell survival rate of hBMSC cells and NIH-3T3 cells was about 90%.The results of cell fluorescence imaging analysis further confirmed this conclusion.These results demonstrate that the constructed pH-responsive micelles can be used in the biomedical field,especially for the encapsulation and delivery of drugs with poor stability or water solubility.(2)Photothermal responsive micelles.Using lignin as raw material,the maleated lignin-g-N isopropylacrylamide-N,N dimethylacrylamide polymers were prepared by graft copolymerization.Then,the photosensitizer IR825 molecule was introduced by chemical bonding.The polymer can be self-assembled into nano micelles by solvent exchange method.The structure of the polymer was verified using 1H NMR,FTIR,and UV-visible near infrared spectroscopy.TEM results showed that the micelles were spherical and about 60 nm in diameter.DLS was used to analyze the factors affecting the hydration diameter of micelles.The results showed that the particle size decreased with the increase of water dripping speed,but increased with the increase of initial concentration and initial water content.The temperature responsiveness of the polymer micelles was verified by UV-Vis spectrophotometer and it was found that the micelles disintegrated completely at 38℃.The results of photothermal analysis show that the micelle has excellent photothermal stability.Under the irradiation of 808 nm NIR laser(1 W/cm2),the micelle can be heated from 25℃ to 40℃ in 5 min,then cooled to 25℃ in water bath,and then irradiated for 5 min with 1W/cm2 NIR of 808 nm.The heating efficiency did not significantly reduced after four cycles.In terms of drug delivery,the drug loading capacity and encapsulation efficiency of micelles reached 33.09%and 49.46%,respectively.The release rate of the micelles at 8 h under normal environment was only 21.98%.However,the release rate increased greatly when the 808 nm near-infrared laser(1 W/cm2)was used for 5 min at the 4th hour,and the release rate reached 73.64%at the 8th hour.The results of in vitro cell experiments showed that the cell mortality rate of the drug-loading micelles group was 90.6%after 5 min of irradiation.Animal experiments show that micelles can achieve a high value of fluorescence imaging signals 3 h after injection.The micelles had low biotoxicity and significant thermal imaging effect.The tumor inhibition efficiency was as high as 77.5%after irradiation.In this study,intelligent responsive lignin nanomicrobial micelles were designed to realize environment-induced drug trigger release and multi-mode combination therapy for cancer,which provide a new path for the high-value utilization of lignin.