Cancer-exocytosed Exosomes Loaded With In Situ Biosynthesized Nanoclusters As Smart Drug Carriers For Cancer Theranostics

Drug resistance remains one of the major hurdles to the effective cancer therapy.Recently emerged field of nanotechnology holds great promises for effective and target specific conveyance of therapeutic cargo to malignant sites.Exosomes have been recently come into focus as drug carriers as they are nano-sized,biocompatible and can cross blood brain barriers(BBB).Exosomes exocytose from almost every type of cells and can be separated from body fluids or cell culture medium.Herein,we have developed the new bioresponsive self-assembly of drug-delivery platform through the in situ biosynthesized exosomes(D-Ag NCs@Exo U87),isolated by ultracentrifugation from the cell culture medium of glioblastoma cells(U87)after incubation with[Ag(GSH)]~+and DOX separately and combined.These engineered exosomes are highly cancer targeting and biocompatible,sphere-shaped with the average size of 30-120nm,and can be used as early cancer diagnosis.The D-Ag NCs@Exo U87 showed higher cellular accumulation as compared to D@Exo U87,suggesting the efficiency of the bio-responsive self-assembled silver nanoclusters(Ag NCs)as smart cancer targeting agents.Moreover,the as-prepared D-Ag NCs@Exo U87 cause cytotoxicity involved reactive oxygen species(ROS)damage in cancer cells and have no activity on healthy cells.In addition,the higher efficacy of the intelligent drug release under acidic conditions was clearly observed.This raises the possibility to provide the smart drug delivery platform through the bio-responsive self-assembled exosomes loaded with biocompatible fluorescent nanoclusters including Ag NCs exocytosed from tumor cells for cancer diagnosis and targeted chemotherapy.Cancer is still considered to be fatal disease worldwide,that is a major public concern.Early diagnosis and management are the main attention of researchers to overcome malignancy.Exosomes holds great promise for cancer targeting and transporting the therapeutic agents at the site of interest.Bovine serum albumin(BSA)coated nanoparticles(NPs)has attracted much attention in cancer therapy having their great stability,nontoxicity,non-immunogenecity and ability to bind with many therapeutic drugs.In this study,we developed exosomes loaded with DOX binded BSA-Au NCs,released from already treated U87 cells(E@BSA-Au NCs-DOX)for overcoming drug resistance in cancer chemotherapy.An easy approach was used to achieve in situ,self-assembled fluorescent BSA-Au NCs from cancer cells.Consequently,the exosomes,isolated from treated cancer cells,were observed to be encapsulated with in situ biosynthesized BSA-Au NCs and DOX.The as prepared exosomes(E@BSA-Au NCs-DOX)were sphere-shaped with an average size of 30-120 nm.The E@BSA-Au NCs-DOX presented an excellent anti-tumor activity against their parent cells and enhanced cell apoptosis owing to the combined effects of the BSA-Au NCs and DOX,while displaying no observable activity against normal cells.Moreover,E@BSA-Au NCs-DOX opens the opportunity to be utilized as photosensitizer agents,as they are susceptible to induce more cell death upon exposing to NIR-II irradiation.Providing the outstanding qualities of exosomes for cell targeting and transporting,the loading of NIR-II responsive agents provides stimulating possibilities in phototherapy.It is very urgent to invent highly efficient mode of cancer diagnosis and treatment.Several approaches have been developed for targeted and save therapy including interventional administration,nanocarrier delivery and combined therapy.Although,some clinical aspects are need to overcome including drug resistance,non-targeting and nonspecific damage.Photothermal and photodynamic therapies are promising therapeutic methods with excellent efficiency,low damage and high selectivity that exhibit desirable toxicity at tumor site by producing cytotoxic reactive oxygen species(ROS).Inorganic photosensitizers are considered more ideal to achieve precise therapy as compared to organic photosensitizers as they possess good biocompatibility,excellent light stability and anti-photobleaching properties.Here we prepared the in situ self-assembled BSA@Au Ag NCs after introduction of ionic solution of Au and Ag along with Bovine serum albumin(BSA)solution to cancer cells and investigated their properties.TEM images and elemental characterization confirmed the Au Ag NCs formation.Further,we observed a significant increase in temperature of cell culture under NIR-II in the presence of BSA@Au Ag NCs.Thus,we proposed these nanoparticles as good photothermal agent for cancer therapy as it showed photosensitizing properties under laser irradiation.