Carrier-Free Curcumin Nano-Assemblies For Inflammation-Related Diseases Treatment Studies

Background:Inflammation is associated with various chronic and acute diseases,which contribute significantly to organ and tissue dysfunction.Drugs that are currently widely used to treat inflammation-related diseases,such as nonsteroidal anti-inflammatory drugs or glucocorticoids,inevitably cause a range of side effects,which can affect the effectiveness of treatment.Therefore,exploring new approaches to the treatment of inflammation is an urgent clinical problem to be solved.Polyphenols,secondary metabolites of plants,are often present in fruits,vegetables,tea,coffee,and legumes.According to current research,polyphenols have a wide range of antimicrobial(viral,bacterial and fungal),anti-inflammatory,cardioprotective,anti-asthmatic,anti-depressant and anti-anxiety,anti-diabetic,neuroprotective and anti-cancer effects.In addition,since natural polyphenols are an important dietary source for humans,they are generally considered to be safe,thus attracting a wide range of researchers.For example,the maximum safe intake of curcumin,a representative molecule of polyphenols,is 12 g per day,offering long-term safety advantages in its therapeutic use.However,the insolubility and low bioavailability of curcumin have impeded its practical clinical application.In this study,we prepared curcumin nano-assemblies by carrier-free self-assembly method and verified their therapeutic effects on inflammatory diseases,expanding the application area of insoluble natural active polyphenols and providing new ideas for the treatment of inflammation-related diseases.Methods:(1)PEG and curcumin were polymerized in one step by ring-opening reaction of cyclic ether.Solvent-mediated reversed-phase assembly was used to prepare carrier-free curcumin nanoassemblies.(2)The physical and chemical properties of NCAs were characterized by infrared spectrum,nuclear magnetic resonance(NMR),XRD and TG;The ability of NCAs to scavenge DPPH and ABTS radicals was tested in vitro.(3)DCFH-DA fluorescence probe was used to detect the scavenging ability of intracellular reactive oxygen species.Activated RAW264.7 cells as well as normal RAW264.7cells were treated separately with ICG-labelled NCAs,which is to explore whether inflammatory cells have a greater capacity for uptake of NCAs.(4)Activated RAW264.7 cells were treated with different concentrations of free curcumin and NCAs respectively,and the gene expression levels of IL-6,tumor necrosis factor-α and IL-β factors were measured by Real-time q PCR to clarify the anti-inflammatory effects of NCAs at the cellular level.(5)To construct mouse acute sepsis model,ulcerative colitis model and chronic liver fibrosis inflammation model,and to analyze whether NCAs can effectively inhibit inflammation and fibrosis in vivo by detecting relevant serological indicators,staining of tissue sections,q PCR,Western blot and immunohistochemistry,immunofluorescence,ELISA and other techniques.Results:(1)Curcumin nanoassemblies were prepared by a solvent transformation-based nanoprecipitation method in the presence of polyethylene glycol diglycidyl ether(PGDE);the PGDE-curcumin coupling formed a homogeneous nanoassembly of irregular shape and retained the molecular backbone of curcumin under the driving force of the solvent.(2)The results of FT-IR and NMR showed that the characteristic peak of curcumin is entirely consistent between NCAs and free curcumin,indicating that the molecular structure of curcumin was not destroyed,and curcumin and PEG were successfully coupled.DPPH and ABTS radical scavenging assays confirmed that the reactive oxygen scavenging ability of NCAs was preserved compared to free curcumin(3)The uptake of NCAs by activated RAW264.7 cells was significantly increased compared to normal cells.(4)After curcumin and NCAs were administered to activated RAW264.7 cells,the expression of IL-6,tumour necrosis factor-α,and IL-1β was significantly diminished when compared to the control group.The anti-inflammatory ability of NCAs and free curcumin was comparable,indicated that the combination of PEG and curcumin did not significantly damage its anti-inflammatory activity.(5)In the mouse acute sepsis model,compared with the control group,the NCAs-treated mice showed normalized lung histomorphology,significantly improved liver inflammation,and significantly decreased expression levels of IL-6,TNF-a and IL-1β as well as NOX1 and NOX4.(6)The control mice in the mouse model of ulcerative colitis had a significantly shorter colon length than the NCAs-treated mice,and the latter exhibited a marked decrease in colonic inflammation and bleeding,as well as a notable reduction in the expression of inflammatory factors such as MPO,IL-6,TNF-α and IL-1β in the intestinal tissues.(7)In a mouse model of chronic fibrosis,NCAs were found to reduce the extent of liver fibrosis by inhibiting the TGF-β/Smad pathway,further inhibiting collagen production and accelerating the degradation of deposited collagen.ConclusionThe insoluble natural curcumin can be self-assembled into NCAs by covalent modification and retains the antioxidant and anti-inflammatory properties of curcumin,which can be efficiently utilized in living organisms,providing a new idea for the preparation of natural active functional nanomaterials or nanomedicines based on plant functional molecules.