Purpose The present study is aimed at designing an appropriate co-delivery system for chemotherapeutic drugs and gene drugs with high loading capacity, on-demand release behaviors, efficient endosomal escape, and enhanced nucleic localization, thereby providing efficacious antitumor activity. Methods Schiff-base linked imidazole dendritic mesoporous silica nanoparticles (SL-IDMSN) were developed and employed to load doxorubicin (DOX) and survivin shRNA-expressing plasmid (iSur-pDNA) to form nanocomplexes. The nanoparticles were assessed by structural characterization, drug loading and release, cellular uptake, intracellular distribution, gene transfection, in vitro anti-proliferation of hepatoma cells, and in vivo tumor growth inhibition in H-22 tumor bearing mice. Results SL-IDMSN showed high loading capacity for both DOX and iSur-pDNA due to their hierarchical mesostructures. The cleavage of Schiff-base linkage on SL-IDMSN in the weakly acidic endosomes/lysosomes led to microenvironment-specific release of both DOX and iSur-pDNA. Meanwhile, the imidazole modification could trigger the efficient endosomal escape via proton sponge effect, thereby enhancing nuclear accumulation of iSur-pDNA and gene silencing efficiency. More importantly, these superior performances of SL-IDMSN resulted in their improved inhibitory effects on in vitro cancer cell proliferation and in vivo tumor growth. Conclusions SL-IDMSN is a microenvironment-sensitive and biocompatible nanocarrier for the co-delivery of DOX and iSur-pDNA, which might be a promising carrier for co-delivery of chemotherapeutic drugs and gene drugs for synergistic cancer therapy.
Silencing the inhibitor of apoptosis (IAP) by RNAi is a promising method for tumor therapy. One of the major challenges lies in how to sequentially overcome the system barriers in the course of the tumor targeting delivery, especially in the tumor accumulation and penetration. Herein we developed a novel stimuli-responsive polysaccharide enveloped liposome carrier, which was constructed by layer-by-layer depositing redox-sensitive amphiphilic chitosan (CS) and hyaluronic acid (HA) onto the liposome and then loading IAP inhibitor survivin-shRNA gene and permeation promoter hyaluronidase (HAase) sequentially. The as-prepared HA/HAase/CS/liposome/shRNA (HCLR) nanocarrier was verified to be stable in blood circulation due to the negative charged HA shield. The tumor targeting recognition and the enhanced tumor accumulation of HCLR were visualized by fluorescence resonance energy transfer (FRET) and in vivo fluorescence biodistribution. The deshielding of HA and the protonizing of CS in slightly acidic tumor extracellular pH environment (pHe, 6.8–6.5) were demonstrated by ζ potential change from −23.1 to 29.9 mV. The pHe-responsive HAase release was confirmed in the tumor extracellular mimicking environments, and the intratumoral biodistribution showed that the tumor penetration of HCLR was improved. The cell uptake of HCLR in pHe environment was significantly enhanced compared with that in physiological pH environment. The increased shRNA release of HCLR was approved in 10 mM glutathione (GSH) and tumor cells. Surprisingly, HCLR suppressed the tumor growth markedly through survivin silencing and meanwhile maintained low toxicity to mice. This study indicates that the novel polysaccharide enveloped HCLR is promising in clinical translation, thanks to the stimuli-triggered tumor accumulation, tumor penetration, cell uptake, and intracellular gene release.
Although novel molecular targeted drugs have been recognized as an effective therapy for non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) activating mutations, their efficacy fails to meet the expectation due to the acquired resistance in tumors. Up-regulation of the anti-apoptotic protein Survivin was shown to contribute to the resistance to EGFR tyrosine kinase inhibitors (TKI) in EGFR mutation–positive NSCLC. However, the unorganized tumor blood vessels impeded drug penetration into tumor tissue. The resulting insufficient intracellular drug/gene delivery in drug-resistant cancer cells remarkably weakened the drug efficacy in NSCLC. In this work, a multi-functional drug delivery system AP/ES was developed by using anti-EGFR aptamer (Apt)-modified polyamidoamine to co-deliver erlotinib and Survivin-shRNA. Chloroquine (CQ) was used in combination with AP/ES to normalize tumor vessels for sufficient drug/gene delivery to overcome drug resistance in NSCLC cells. The obtained AP/ES possessed desired physicochemical properties, good biostability , controlled drug release profiles, and strong selectivity to EGFR-mutated NSCLC mediated by Apt. CQ not only enhanced endosomal escape ability of AP/ES for efficient gene transfection to inhibit Survivin, but also showed strong vessel-normalization ability to improve tumor microcirculation , which further promoted drug delivery and enhanced drug efficacy in erlotinib-resistant NSCLC cells. Our innovative gene/drug co-delivery system in combination with CQ showed a promising outcome in fighting against erlotinib resistance both in vitro and in vivo . This work indicates that normalization of tumor vessels could help intracellular erlotinib/Survivin-shRNA delivery and the down-regulation of Survivin could act synergistically with erlotinib for reversal of erlotinib resistance in EGFR mutation-positive NSCLC. Statement of Significance NSCLC patients who benefited from EGFR-TKIs inevitably developed acquired resistance. Previous research focused on synthesis of new generation of molecular targeted drugs that could irreversibly inhibit EGFR with a particular gene mutation to overcome drug resistance. However, they failed to inhibit EGFR with other gene mutations. Activation of bypass signaling pathway and the changes of tumor microenvironment are identified as two of the mechanisms of acquired resistance to EGFR-TKIs. We therefore constructed multifunctional gene/drug co-delivery nanocomplexes AP/ES co-formulated with chloroquine that could target the both two mechanisms. We found that chloroquine not only enhanced endosomal escape ability of AP/ES for efficient gene transfection to inhibit Survivin, but also showed strong vessel-normalization ability to improve tumor microcirculation, which further promoted drug delivery into tumor tissue and enhanced drug efficacy in erlotinib-resistant NSCLC.
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