Phototriggered charge reversal of dendrimer-based nanocomplexes for targeted drug delivery

Abstract

Nanotechnology is widely utilized for drug delivery. Different carriers with unique properties are developed for enhanced therapeutic efficacy. Stimuli-responsive nanocarriers stand out because of controlled drug release and accumulation at the desired sites. However, interstitial fluid pressure, deficient cellular uptake, and failure of endosomal escape still limit efficacy of nanomedicines. Hence, the charge-reversal strategy was put forward, in which negatively charged nanoparticles keep stable in circulation and decrease non-specific delivery. The nanoparticles become positively charged upon applying certain stimulus for deeper penetration, more cellular uptake, and successful endosomal escape. Light as an external stimulus can be controlled spatiotemporally and manipulated easily. Phototriggered charge reversal for drug delivery is promising to maximize therapeutic efficacy and minimize side effects. In this thesis, a photocontrolled charge-reversible drug carrier was developed based on a cationic dendrimer, poly(amidoamine) (PAMAM), and a photoremovable protecting group, boron dipyrromethene (BODIPY). BODIPY-modified PAMAM (BMP) self-assembled with therapeutic agents to form nanoparticles. The nanoparticles were coated with hyaluronic acid (HA) to make the nanoparticles stable and negatively charged to avoid untargeted delivery. Under light irradiation, the nanoparticles turned to be positively charged because of photocleavage of BODIPY groups and re-exposure of amino groups, thereby promoting intracellular delivery and endosomal escape of cargo drugs. In the first study, green light-responsive BMP was used to form nanoparticles with proteins by the ion-π interaction, hydrophobic interaction, and ionic interaction between proteins and BMP. The nanoparticles were further coated with HA and human serum albumin, protecting cargo proteins from degradation and preventing nanoparticle aggregation in serum. The phototriggered charge reversal of protein-encapsulated nanoparticles enhanced cellular uptake and endosomal escape of varieties of proteins with different molecular weights and isoelectric points. In the second study, BMP was used to form nanoparticles with synergistic ferroptosis inducers, chlorin e6 (Ce6) and an inhibitor of ferroptosis suppressor 1 (iFSP1). Ce6-mediated photodynamic therapy (PDT) promotes glutathione deletion, glutathione peroxidase 4 degradation, and lipid peroxide accumulation. However, PDT-induced ferroptosis is prevented by FSP1, a newly found enzyme which can consume reductive CoQ10 to eliminate lipid peroxides. To address this limitation, a novel strategy was developed to trigger ferroptosis by PDT and FSP1 inhibition. The HA-coated nanoparticles could enhance cellular uptake and tumor accumulation of Ce6 and iFSP1 after light irradiation, showing robust induction of ferroptosis and immunogenic cell death in vitro and in vivo. For deeper light penetration, NIR light-responsive BMP (NBMP) was further developed and used to deliver Ce6 and iFSP1. Combined with anti-PD-L1 immunotherapy, the strategy showed efficient tumor growth inhibition. In the third study, NBMP was used to deliver a model tumor antigen, ovalbumin, and a NLRP3 inflammasome agonist, BMS986299. The nanoparticles also showed enhanced intracellular delivery and endosomal escape of cargos under NIR light irradiation. This strategy successfully improved antigen cross-presentation and T cell activation with light irradiation in vitro and in vivo, showing potent anti-tumor efficacy. The inflammasome-activating nanovaccines further enhanced the anti-PD-1 immunotherapy against melanoma and hepatocellular carcinoma with immune memory establishment.