Rod-like Shaped Cellulose Nanocrystal-based PH-Responsive Nanomedicines

It has been reported that size,material and shape of nanocarrier have great influence on their therapy effect and drug delivery efficiency of nanomedicines.Nanomedicines based on the rod-like cellulose nanocrystal can evade macrophage,and have a relative long blood circulation time.Therefore,rod-like shaped nanomedicines can enhance cellular uptake and accumulate in tumor tissues.They were expected to overcome the bottleneck problems of cancer therapy.We have designed and prepared a series of acid-sensitive nanomedicines based on cellulose nanocrystals.The pH labile chemical bond enables acid responsive nanomedicine realizing controlled drug release in the acidic environment of the tumor cells,which can greatly improve the anti-tumor effect,and reduce the systemic toxicity and side effects of the anti-tumor drugs.Those nanomedicines have great potential to promot the development of cancer therapy and the application of cellulose nanocrystals.Hence,this paper focoused on the prepartion and biological evluation of rod-like shaped cellulose nanocrystal-based pH-responsive nanomedicines.All of our research work and results were depicted clearly as followed:In the first part,cis-aconityl-doxorubicin?CAD?was synthesized by the ring-opening reaction between cis-aconitic anhydride?CAA?and doxorubicin?DOX?,then CAD labeled nanocrystal rods?CNR??i.e.CAD@CNR?was prepared by the amidation reaction between the 6-carboxylic groups of CAD and the amino groups of aminated cellulose nanocrystal rod.Compared with CNR,CAD@CNR showed similar morphology and crystal structure.The mean length of CAD@CNR was ca.118 nm with aspect ratio ranging from 12 to 15,facilitating their endocytosis.CAD@CNR prodrug was rather stable in pH 7.4 phosphate buffer solution but tended to be hydrolyzed to release DOX under acidic condition.CAD@CNR prodrug was lysosomal pH-controlled drug release.The half maximal inhibitory concentration(IC₅₀)of CAD@CNR prodrug against NCI H 460 cells without NH₄Cl?lysosomotropic weak bases?pretreatment was 1.75 times higher than that with 40 mM NH₄Cl pretreatment,further confirmed that the DOX release from the CAD@CNR prodrug was triggered by the low pH value of lysosome?pH 5.0?.Compared with DOX·HCl,CAD@CNR prodrug showed enhanced cellular uptake ability during 12 or 24 h of incubation due to the endocytosis mechanism of CAD@CNR prodrug.After incubation with cells,CAD@CNR prodrug could be observed by using fluorescence microscope due to the red fluorescence of DOX.In a word,CAD@CNR showed great potential as fluorescence-visible drug delivery system with enhanced cellular uptake and intracellular drug release due to its rod-like morphology,suitable aspect ratio,and acid-triggered drug release.In the second part,based on our previous research works and results of chapter two,CNC-based nanomedicines were built by CAD,polyethylenimine?PEI?,and CNCs through layer-by-layer?LbL?assembly.In vitro,the newly made hybrids nanmomedicines:cis-aconityl-doxorubicin?CAD?@polyethylenimine?PEI?@CNCs?CAD@PEI@CNCs?were still rod-like shape,lysosome pH-controlled DOX release.Meanwhile,CAD@PEI@CNCs hybrids realized high drug loading content??27±4.6?wt%?,and efficient and precise DOX delivering into the nucleus.Moreover,the cellular uptake of CAD@PEI@CNCs hybrids was 20.9,3.8,and 15.5 folds higher than that of DOX·HCl against A549 cells,MCF-7 cells and DOX-resistant MCF-7 ADR cells,respectively.The cytotoxicity of CAD@PEI@CNCs hybrids was much higher than that of DOX·HCl and the pH-irresponsive hybrids against A549 cells,MCF-7 cells and DOX-resistant MCF-7 ADR cells.In vivo,CAD@PEI@CNCs hybrids exhibited good antitumor effect:?42.0±6?%inhibition rate and little harm to the athymic nude mice.Altogether,rod-like-shape pH-responsive CAD@PEI@CNCs hybrids nanomedicines could efficiently overcome the vascular and tumor barriers,and precisely deliver DOX to nucleus to convert DOX therapeutic role.In the third part,based on the research works and results of chapter two and three,thefolatetargetedhybridsnanomedicines:folate/cis-aconityl-doxorubicin@polyethylenimine@CNCs?FA/CAD@PEI@CNCs?nanomedicines were built up by the building blocks of folate?FA?,CAD,PEI and CNCs via the robust LbL assembly technique.The FA/CAD@PEI@CNCs hybrids gathered the negative and positive targetability of nanomdicines.The drug loading content?DLC?of FA/CAD@PEI@CNCs hybrids was 11.3 wt%.FA/CAD@PEI@CNCs nanomedicines showed lysosomal pH-controlled drug release profiles over 24 h.In detail,the cumulative drug release was over 95%at pH 5.5,while the cumulative drug release was only 17%at pH 7.4.In vitro,FA/CAD@PEI@CNCs hybrids nanomedicines had a higher?9.7 folds?mean fluorescent intensity?MFI?than that of DOX·HCl,with enhanced cytotoxicity and decreased IC₅₀ against MCF-7.Thus FA/CAD@PEI@CNCs hybrids nanomedicines displayed efficient targetability and enhanced cellular uptake.These results indicated that FA/CAD@PEI@CNCs nanomedicines were the lysosomal pH-controlled drug release into nucleus,and showed great potential to be high-performance nanomedicines to improve the delivery efficiency and therapy efficacy.In brief,by combination the advantage of cellulose nanocrystal,rod-like shape,acid labile chemical bonds and the folic acid,a series of rod-like pH responsive nanomedicines were obtained,which supplied important insights into the biomedical application of CNCs.