No abstract

This study aimed to develop an efficient step-by-step osteosarcoma (OS)-targeting liposome system functionalized with a redox-cleavable, bone- and cluster of differentiation 44 (CD44)-dual-targeting polymer. Furthermore, the effect of coadministration of a tumor-penetrating peptide, internalizing RGD (iRGD), was investigated. First, a bone-targeting moiety, alendronate (ALN), was conjugated with hyaluronic acid (HA), a ligand for CD44. This ALN–HA conjugate was coupled with DSPE–PEG2000–COOH through a bioreducible disulfide linker (−SS−) to obtain a functionalized lipid, ALN–HA–SS–L, to be postinserted into preformed liposomes loaded with doxorubicin (DOX). The roles of ALN, HA, and the redox sensitivity of the ALN–HA–SS–L liposomes (ALN–HA–SS–L–L) in the anti-OS effect were critically evaluated against various reference liposomal formulations (with only ALN, HA, or redox sensitivity). ALN–HA–SS–L–L displayed a zeta potential of −26.07 ± 0.32 mV and selectively disassembled in the presence of a reducing agent, 10 mM glutathione, which can be found in cancer cells. Compared to various reference liposomes, ALN–HA–SS–L–L/DOX had significantly higher cytotoxicity to human OS MG-63 cells alongside high and rapid cellular uptake. In the orthotopic OS nude mouse models, ALN–HA–SS–L–L/DOX showed remarkable tumor growth suppression and prolonged survival time. This result was further improved by the coadministration of iRGD. The antitumor effects of various liposomes were ranked in the same order as the degree of tumor biodistribution shown by in vivo/ex vivo imaging: ALN–HA–SS–L–L coadministered with iRGD > ALN–HA–SS–L–L > HA–SS–L–L > HA–L–L > PEG–L> free drug. ALN–HA–SS–L–L/DOX also reduced the cardiotoxicity of DOX and lung metastases. Overall, this study demonstrated that ALN–HA–SS–L–L/DOX, equipped with bone- and CD44-dual-targeting abilities and redox sensitivity, could be a promising OS-targeted therapy. The efficacy could also be augmented by coadministration of iRGD.

Cancer chemotherapy typically relies on drug endocytosis and inhibits tumor cell proliferation via intracellular pathways; however, severe side effects may arise. In this study, we performed a first attempt to develop macromolecular‐induced extracellular chemotherapy involving biomineralization by absorbing calcium from the blood through a new type of drug, polysialic acid conjugated with folate (folate‐polySia), which selectively induces biogenic mineral formation on tumor cells and results in the pathological calcification of tumors. The macromolecule‐initiated extracellular calcification causes cancer cell death mainly by intervening with the glycolysis process in cancer cells. Systemic administration of folate‐polySia inhibited cervical and breast tumor growth and dramatically improved survival rates in mice. This study provides an extracellular therapeutic approach for malignant tumor diseases via calcification that is ready for clinical trials and offers new insights into macromolecular anticancer drug discovery.

An estrogen (ES)-functionalized cationic liposomal system was developed and exploited for targeted delivery to osteosarcoma. Natural biocompatible chotooligosaccharides (COS, MW2-5 KDa) were covalently tethered to the liposomal surface through a disulfate bond (-SS-) to confer reduction-responsive COS detachment, whereas estrogen was grafted via polyethylene glycol (PEG 2 K) chain to achieve estrogen receptor-targeting. The liposomal carriers were prepared by the ethanol injection method and fluorescent anticancer drug doxorubicin (DOX) was loaded with ammonium sulfate gradient. The physicochemical properties, reduction-sensitivity, and the roles of estrogen on cellular uptake and tumor-targeting were studied. The Chol-SS-COS/ES/DOX liposomes were spherical with an average size about 110 nm, and high encapsulation efficiency. The liposomes were stable in physiological condition but rapidly release the payload in response to tumoral intracellular glutathione (20 mM). MTT cytotoxicity assay confirmed that Chol-SS-COS/ES/DOX liposomes exhibited higher cytotoxicity to MG63 osteosarcoma cells than to liver cells (LO2). Flow cytometry (FCM) and confocal laser scanning microscopy revealed that cellular uptake of Chol-SS-COS/ES/DOX liposomes by MG63, than the free DOX or Chol-SS-COS/DOX. Ex vivo fluorescence distribution study showed that the multifunctional liposomes selectively accumulated in the MG63 xenografts versus the organs. Chol-SS-COS/ES/DOX liposomes strongly inhibited the tumor growth and enhanced the animal survival rate. Overall, the COS grafted estrogen-functionalized cationic liposomes, fortified with glutathione-responsiveness, showed great potential for specific intracellular drug delivery to estrogen receptor-expressing tumors such as osteosarcoma.