Yu-Kyoung Oh

siRNA delivery systems for cancer treatment

With increasing knowledge on the molecular mechanisms of endogenous RNA interference, small interfering RNAs (siRNAs) have been emerging as innovative nucleic acid medicines for treatment of incurable diseases such as cancers. Although several siRNA candidates for the treatment of ocular and respiratory diseases are undergoing clinical trials, there are challenges inherent in the further development of siRNAs for anti-cancer therapeutics, because systemic administration will be required in most cases. In addition to nonspecific off-target and immune stimulation problems, appropriate delivery remains a major hurdle. The technologies developed for delivery of nucleic acid medicines such as plasmid DNA and antisense oligonucleotides have paved the way to rapid progress for in vivo delivery of siRNAs. Here, we review various in vivo delivery strategies including chemical modification, conjugation, lipid-based techniques, polymer-based nanosystems, and physical methods. Moreover, the current progress in siRNA delivery systems for gynecologic, liver, lung, and prostate cancers is discussed.

Cellular uptake mechanism and intracellular fate of hydrophobically modified glycol chitosan nanoparticles

Polymeric nanoparticle-based carriers are promising agents for the targeted delivery of therapeutics to the intracellular site of action. To optimize the efficacy in delivery, often the tuning of physicochemical properties (i.e., particle size, shape, surface charge, lipophilicity, etc.) is necessary, in a manner specific to each type of nanoparticle. Recent studies showed an efficient tumor targeting by hydrophobically modified glycol chitosan (HGC) nanoparticles through the enhanced permeability and retention (EPR) effect. As a continued effort, here the investigations on the cellular uptake mechanism and the intracellular fate of the HGC nanoparticles are reported. The HGC nanoparticle, prepared by a partial derivatization of the free amino groups of glycol chitosan (GC) with 5beta-cholanic acid, had a globular shape with the average diameter of 359 nm and the zeta potential of ca. 22 mV. Interestingly, these nanoparticles showed an enhanced distribution in the whole cells, compared to the parent hydrophilic GC polymers. In vitro experiments with endocytic inhibitors suggested that several distinct uptake pathways (e.g., clathrin-mediated endocytosis, caveolae-mediated endocytosis, and macropinocytosis) are involved in the internalization of HGC. Some HGC nanoparticles were found entrapped in the lysosomes upon entry, as determined by TEM and colocalization studies. Given such favorable properties including low toxicity, biocompatibility, and fast uptake by several nondestructive endocytic pathways, our HGC nanoparticles may serve as a versatile carrier for the intracellular delivery of therapeutic agents.

siRNA Conjugate Delivery Systems

Small interfering RNA (siRNA) has been chemically conjugated to a variety of bioactive molecules, lipids, polymers, peptides, and inorganic nanostructured materials to enhance their pharmacokinetic behavior, cellular uptake, target specificity, and safety. To efficiently deliver siRNAs to the target cells and tissues, many different siRNA bioconjugates were synthesized and characterized, and their gene silencing efficiencies were tested in vitro and in vivo. In this review, recent developments of siRNA bioconjugates are summarized.

Development of in situ-gelling and mucoadhesive acetaminophen liquid suppository

Abstract Conventional suppositories are solid forms which often cause discomfort during insertion. The leakage of suppositories from the rectum also gives uncomfortable feelings to the patients. In addition, when the solid suppositories without mucoadhesivity reach the end of the colon, the drugs can undergo the first-pass effect. To solve these problems, we developed a novel in situ-gelling and mucoadhesive acetaminophen liquid suppository with gelation temperature at 30–36°C and suitable gel strength and bioadhesive force. Poloxamer 407 (P407) or/and poloxamer 188 (P188) were used to confer the temperature-sensitive gelation property. The mixtures of P407 (15%) and P188 (15–20%) existed as a liquid at room temperature, but gelled at 30–36°C. Acetaminophen, the active ingredient of the suppositories, slightly increased gelation temperature, but significantly decreased gel strength and bioadhesive force. To modulate the gel strength and the bioadhesive force of acetaminophen liquid suppositories, bioadhesive polymers such as polyvinylpyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC), hydroxypropylcellulose (HPC), carbopol and polycarbophil were studied. The bioadhesive polymers exerted various impacts on the physicochemical properties of liquid suppositories. The gelation temperature was not significantly affected by PVP, HPMC and HPC, but decreased by carbopol and polycarbophil. Of bioadhesive polymers, carbopol and polycarbophil most significantly enhanced both gel strength and bioadhesive force. The liquid suppositories with carbopol or polycarbophil were inserted into the rectum of rats without difficulty and leakage and retained in the rectum for at least 6 h. These results suggest that in situ-gelling and mucoadhesive liquid suppository for humans can be further developed as a more convenient and effective rectal dosage form.

In situ gelling and mucoadhesive liquid suppository containing acetaminophen: enhanced bioavailability

Solutions of poloxamers and bioadhesive polymers were previously reported to undergo a phase transition to bioadhesive gels at body temperature. For the development of a convenient acetaminophen-loaded liquid suppository which gels in situ after rectal administration, we studied the release and pharmacokinetics of acetaminophen delivered by the liquid suppository systems composed of poloxamer P 188, P 407 and a bioadhesive polymer, polycarbophil. The release of acetaminophen was differently affected by the components of liquid suppository such as P 188 and polycarbophil. P 188 showed little effect on the release rates of acetaminophen from liquid suppositories. However, polycarbophil significantly delayed the release kinetics of acetaminophen from a certain concentration due to strong gel strength and bioadhesive force. The release rates of acetaminophen did not significantly differ between no polycarbophil and 0.2% polycarbophil-loaded suppositories, while they began to decrease as the concentrations of polycarbophil increased higher than 0.4%. The analysis of release mechanism showed that the release of acetaminophen was proportional to the square root of time, indicating that acetaminophen might be released from the suppositories by Fickian diffusion. Liquid suppository A [P 407/P 188/polycarbophil/acetaminophen (15:19:0.8:2.5%)], which was strongly gelled and mucoadhesive in the rectum, showed more sustained acetaminophen release profile than did other suppositories and gave the most prolonged plasma levels of acetaminophen in vivo. Liquid suppository A also showed higher bioavailibility of acetaminophen than did the conventional formulation. Moreover, liquid suppository A did not cause any morphological damage to the rectal tissues and remained stable for at least 6 month during storage. These results suggest that mucoadhesive and in situ gelling liquid suppository could be a more effective and convenient rectal delivery system of acetaminophen.

Rheological evaluation of thermosensitive and mucoadhesive vaginal gels in physiological conditions.

The timely gelation and retention of in situ-gelling vaginal formulations would be fundamental to improve the efficacy of drugs. In this study, various rheological properties of clotrimazole gels were evaluated for predicting their performance in vagina. Two kinds of thermosensitive and mucoadhesive formulations were composed of poloxamer 407 (P407, 15%), polycarbophil (0.2%), and different amounts of P188 (15 vs. 20%). Both formulations were Newtonian at 20 degrees C but non-Newtonian at 37 degrees C. Although both liquid formulations gelled below the vaginal temperature, they differed in gelation time and viscoelastic properties in the presence of vaginal fluid simulant. At body temperature, the formulation with 20% of P188 gelled within 35 s but it took two times longer for the other one gelled. Upon dilution with simulated vaginal fluid, the formulation with 20% of P188 retained the rheology of a gel, but the other one lost the viscoelastic properties typical for a gel. Moreover, after dilution with simulated vaginal fluid, the elastic modulus was orders of magnitude higher in the formulations with 20% of P188 relative to the other one. These results indicate that the rheological evaluation at the physiologic conditions needs to be preceded to develop more effective in situ-gelling vaginal formulations.

Prolonged antifungal effects of clotrimazole-containing mucoadhesive thermosensitive gels on vaginitis

To develop more effective treatment for vaginal candidasis, clotrimazole (CT) was formulated in mucoadhesive thermosensitive gels (MTG). Several MTG formulations composed of poloxamers (P) 407, 188, and polycarbophil (PC) were prepared. P188 and PC increased the mucoadhesiveness but reduced the syringebility of liquid forms of the gels. Based on the balance between the mucoadhesiveness and syringebility, MTG composed of P407/P188/PC (15/15/0.2 or 15/20/0.2) were further studied. Of the two MTG, the formulation with 15% of P188 gelled at higher temperature and revealed lower elastic modulus. In vitro, sustained release of CT from MTG was observed. In vivo antifungal activity of CT, tested against Candida albicans vaginitis in female rats, was significantly prolonged after vaginal delivery using MTG. At 10 days post-dose, the c.f.u. of C. albicans was more than 10(4)-fold decreased in MTG-treated groups. Moreover, the vaginal delivery of CT in MTG enhanced the viability of epithelial cells without affecting the morphology of vaginal mucosa. These results indicate that CT-containing vaginal MTG might be further developed for safe, convenient, and effective treatment of vaginal candidasis with reduced dosing interval.

Safety and tumor tissue accumulation of pegylated graphene oxide nanosheets for co-delivery of anticancer drug and photosensitizer

Here, we report the safety, tumor accumulation and potential of polyethylene glycol-grafted graphene oxide (pGO) as a multimodal nanocarrier of photosensitizers and synergistic anticancer agents. First, both graphene oxide (GO) and pGO were synthesized, and their in vitro and in vivo toxicities were tested. When 80 mg/kg was injected intravenously into mice, there was 100% fatality in the GO-treated group, but 100% survival among mice treated with pGO nanosheets. Treatment of cells with a photosensitizer chlorin e6 (Ce6) in pGO nanophysisorplexes significantly enhanced cellular delivery compared to that seen with Ce6 alone. The combination and dose reduction indexes revealed that combining doxorubicin (Dox) with Ce6 with at a molar ratio of 1:2 provided the highest synergism. The Ce6- and Dox-loaded pGO nanophysisorplexes (Ce6/Dox/pGO) were 148.0 ± 18.0 nm in size. Molecular imaging of mice showed that Ce6/Dox/pGO could accumulate in tumor tissues over 3 days. Moreover, in SCC tumor-bearing mice, the photodynamic anticancer effects of Ce6/Dox/pGO were higher than those of Ce6/pGO or Dox/pGO. Moreover, tumor sections from illuminated mice treated with Ce6/Dox/pGO showed substantial disruption of tumor nuclei, whereas the other groups did not. Our results suggest that pGO nanosheets have superior in vivo safety relative to GO, and that it is possible to enhance the tumor tissue distribution and photodynamic anticancer effects of systemically administered Ce6 by forming multimodal nanophysisorplexes with pGO and synergistic anticancer chemotherapeutics such as Dox.

Hyaluronic acid–polyethyleneimine conjugate for target specific intracellular delivery of siRNA

A novel target specific small interfering RNA (siRNA) delivery system was successfully developed using polyethyleneimine (PEI)-hyaluronic acid (HA) conjugate. Anti-PGL3-Luc siRNA was used as a model system suppressing the PGL3-Luc gene expression. The siRNA/PEI-HA complex with an average size of ca. 21 nm appeared to be formed by electrostatic interaction between the negatively charged siRNA and the positively charged PEI of PEI-HA conjugate. The cytotoxicity of siRNA/PEI-HA complex to B16F1 cells was lower than that of siRNA/PEI complex according to the MTT assay. When B16F1 and HEK-293 cells were treated with fluorescein isothiocyanate (FITC) labeled siRNA/PEI-HA complex, B16F1 cells, with a lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), showed higher green fluorescent intensity than HEK-293 cells because of the HA receptor mediated endocytosis of the complex. Accordingly, the PGL3-Luc gene silencing of anti-PGL3-Luc siRNA/PEI-HA complex was more efficient in B16F1 cells than in HEK-293 cells. In addition, the inhibited PGL3-Luc gene silencing effect in the presence of free HA in the transfection medium revealed that siRNA/HA-PEI complex was selectively taken up to B16F1 cells via HA receptor mediated endocytosis. All these results demonstrated that the intracellular delivery of anti-PGL3-Luc siRNA/PEI-HA complex could be facilitated by the HA receptor mediated endocytosis.

Tumor specificity and therapeutic efficacy of photosensitizer-encapsulated glycol chitosan-based nanoparticles in tumor-bearing mice

We reported the development of new nanoscale drug carriers, chitosan-based nanoparticles (CNPs) that can be used for photodynamic therapy. These carriers could encapsulate a photosensitizer, protophorphyrin IX (PpIX), and deliver it to tumor tissue. We already reported that CNPs presented the enhanced tumor target specificity in cancer therapy and imbibed various water insoluble anticancer agents into the hydrophobic multicores of nanoscale particles. In this study, we prepared photosensitizer-encapsulated CNPs by self-assembling amphiphilic glycol chitosan-5beta-cholanic acid conjugates in an aqueous environment and then encapsulating the water-insoluble photosensitizer (PpIX), with high drug-loading efficiency (>90%) by using a dialysis method. Freshly prepared PpIX-encapsulated CNPs (PpIX-CNPs) had an average diameter of 290nm and were stable in aqueous solutions for 1 month. As nanoscale drug carriers, PpIX-CNPs exhibited a sustained release profile in vitro and were non-toxic to tumor cells in the dark. In a cell culture system, we observed rapid cellular uptake of the PpIX-CNPs and the released PpIX from CNPs became highly phototoxic upon visible irradiation. In SCC7 tumor-bearing mice, PpIX-CNPs exhibited enhanced tumor specificity and increased therapeutic efficacy compared to free PpIX. Taken together, our results indicate that PpIX-CNPs have potential as an effective drug delivery system for clinical photodynamic therapy.