Reactive oxygen species responsive drug releasing nanoparticle based on chondroitin sulfate-anthocyanin nanocomplex for efficient tumor therapy.

To develop a reactive oxygen species (ROS) sensitive drug carrier, a chondroitin sulfate (CS)-anthocyanin (ATC) based nanocomplex was developed. Doxorubicin hydrochloride (DOX) was loaded in the CS-ATC nanocomplex (CS-ATC-DOX) via intermolecular stacking interaction. The nanocomplex was fabricated by a simple mixing method in the aqueous phase. The morphology and size of CS-ATC-DOX were determined by ATC content. In the group with 1.5mg/ml of ATC loaded CS-ATC-DOX (CS-ATC2-DOX), the drug content and loading efficiency were 8.5% and 99.1%, respectively. The ROS sensitive drug release of CS-ATC2-DOX was confirmed under in vitro physiological conditions. The results demonstrated that 1.67 times higher DOX release occurred in CS-ATC2-DOX for 48h compared to CS-DOX (ATC absent sample). Drug release and nanocomplex destruction were induced by ROS mediated ATC degradation. We determined that 66.7% of ROS was scavenged by CS-ATC2-DOX. Additionally, an HCT-116 tumor bearing animal model was used to confirm ROS sensitive therapeutic effects of CS-ATC2-DOX. The results indicate that DOX was released from the intravenously injected CS-ATC2-DOX in the tumor tissue. Thus, nuclei shrinkage and dead cells were observed in H&E staining and TUNEL assay, respectively. These data suggest that the tumor growth was effectively inhibited. This study means that CS-ATC2-DOX has potential in improving tumor therapy.

A highly tumor-specific light-triggerable drug carrier responds to hypoxic tumor conditions for effective tumor treatment.

Light-triggered drug delivery is among the most investigated stimulus-response strategies and has been widely explored in cancer treatment. However, the limited specificity of light-triggered drug delivery reduces the therapeutic efficacy and causes considerable undesirable side effects. In this work, we demonstrate a highly tumor-specific light-triggerable drug carrier (H-LTDC) induced by a combination of internal (i.e., tumor hypoxia) and external stimuli (i.e., light). The doxorubicin (DOX)-loaded H-LTDC was self-assembled from type-1-reactive oxygen species (ROStype1)-mediated degradable chondroitin sulfate (CS) conjugated with a photosensitizer (PS), Pheophorbide-a, which has a spherical shape and a uniform size distribution. Under hypoxic conditions, ROSType1 was mainly generated due to the electron-rich sulfate groups in the polysaccharide backbone. The ROStype1 generated by H-LTDC allowed laser-triggered drug release at low oxygen concentrations. From the in vitro cytotoxicity tests with colon cancer cells (HCT-116), under laser irradiation, DOX-loaded H-LTDCs showed higher toxicity under hypoxic conditions than that under normoxic conditions. In vivo and ex vivo biodistribution studies demonstrated that H-LTDCs selectively accumulated in the tumor tissues. As a result, drug-loaded H-LTDCs exhibited high anti-tumor activity in vivo. Overall, we believe that this approach could represent a promising platform for the treatment of tumor and hypoxia-associated diseases without undesirable side effects.

Polymeric photosensitizer-embedded self-expanding metal stent for repeatable endoscopic photodynamic therapy of cholangiocarcinoma.

Photodynamic therapy (PDT) is a new therapeutic approach for the palliative treatment of malignant bile duct obstruction. In this study, we designed photosensitizer-embedded self-expanding nonvascular metal stent (PDT-stent) which allows repeatable photodynamic treatment of cholangiocarcinoma without systemic injection of photosensitizer. Polymeric photosensitizer (pullulan acetate-conjugated pheophorbide A; PPA) was incorporated in self-expanding nonvascular metal stent. Residence of PPA in the stent was estimated in buffer solution and subcutaneous implantation on mouse. Photodynamic activity of PDT-stent was evaluated through laserexposure on stent-layered tumor cell lines, HCT-116 tumor-xenograft mouse models and endoscopic intervention of PDT-stent on bile duct of mini pigs. Photo-fluorescence imaging of the PDT-stent demonstrated homogeneous embedding of polymeric Pheo-A (PPA) on stent membrane. PDT-stent sustained its photodynamic activities at least for 2 month. And which implies repeatable endoscopic PDT is possible after stent emplacement. The PDT-stent after light exposure successfully generated cytotoxic singlet oxygen in the surrounding tissues, inducing apoptotic degradation of tumor cells and regression of xenograft tumors on mouse models. Endoscopic biliary in-stent photodynamic treatments on minipigs also suggested the potential efficacy of PDT-stent on cholangiocarcinoma. In vivo and in vitro studies revealed our PDT-stent, allows repeatable endoscopic biliary PDT, has the potential for the combination therapy (stent plus PDT) of cholangiocarcinoma.

Heparin-folate-retinoic acid bioconjugates for targeted delivery of hydrophobic photosensitizers.

Amphiphilic heparin-retinoic acid (HR) and heparin-folate-retinoic acid bioconjugates (HFR) were synthesized by chemical conjugation of a hydrophobic anticancer agent all-trans-retinoic acid (RA) and a targeting ligand, folic acid (FA), to the high molecular weight heparin backbone. The HR and HFR bioconjugates had a high RA content (22%, w/w) and could self-assemble into nanoparticles with efficient encapsulation of a hydrophobic photosensitizer, pheophorbide a (PhA). The HFR bioconjugate demonstrated higher PhA loading content and loading efficiency compared to HR bioconjugate. The PhA-loaded HR and HFR nanoparticles had an average diameter of about 70 nm, a negatively charged surface, a sustained release pattern and self-quenching effect in a buffered solution. Furthermore, the cellular uptake of PhA-loaded HFR nanoparticles in folate receptor-positive HeLa cells was higher than that of PhA-loaded HR nanoparticles. Upon irradiation, HFR nanoparticles selectively enhanced the phototoxicity of PhA in HeLa cells while the dark-toxicity of the nanoparticles was minimal without light treatment. HFR nanoparticles also demonstrated targeted anti-cancer effect, improving the cytotoxicity of RA in HeLa cells compared to HR nanoparticles at RA concentration ≥50 µg/mL. The targeting effect of HFR and PhA-loaded HFR nanoparticles was not observed in folate receptor-negative HT-29 cells. The results indicated that HFR nanoparticles may be useful for targeted delivery of hydrophobic PDT agents and as a potential nanocarrier for dual chemo-and photodynamic therapies.

Photodynamic efficacy of photosensitizers under an attenuated light dose via lipid nano-carrier-mediated nuclear targeting.

Photodynamic therapy (PDT) has emerged as a treatment for certain malignant-like skin, head and neck, gastrointestinal, and gynecological cancers. The broader acceptance of PDT treatment for large or deep-seated tumors is still hindered, at least in part, by the low photodynamic efficiency of photosensitizers (PS) in the deep-seated tumor environment where the light energy fluency rate is severely attenuated after propagation via skin and/or tissue barriers. In this report, efficient nuclear-targeted intracellular delivery of PS is achieved using an easily fabricated yet entirely biocompatible and inexpensive polysaccharide-functionalized nanoscale lipid carrier, which triggers the intracellular release of photosensitizers inside cancer cells and targets cell nuclear to achieve a significantly enhanced photocytotoxicity. Cancer cells are killed efficiently even under an extremely low light fluency of 1 mW/cm(2) attenuated via an interval meat layer with a thickness of 3 mm. Therefore, this nuclei-targeting system may contribute to the development of a new generation of PS carriers that fight against deep-seated tumors and that exhibit excellent photodynamic efficiency under faint light irradiation.

Acetylated hyaluronic acid/photosensitizer conjugate for the preparation of nanogels with controllable phototoxicity: synthesis, characterization, autophotoquenching properties, and in vitro phototoxicity against HeLa cells.

A proposal is herein examined for a novel yet simple design of a polymeric nanogel, with tumor targeting properties and a controllable phototoxicity, utilizing a low molecular weight-hyaluronic acid (HA(LM))/photosensitizer conjugate. HA(LM) was acetylated prior to being dissolved in DMSO (Ac-HA(LM)) and then was conjugated with different amounts of pheophorbide a (Pba), resulting in the formulation of self-organizing nanogels in aqueous solutions (Ac-HA-Pba 1, 2, and 3). The nanogels observed were below 200 nm in size, with a monodispersed size distribution. The nanogels displayed auto photoquenching qualities in PBS, while their fluorescent intensity strongly correlated with the amount of Pba in the organic solvent (DMSO or DMF). The critical self-quenching concentration (CQC) of the conjugates was found to have decreased as the content of Pba rose. Although Pba was conjugated with HA, the nanogel's photoactivity, in terms of fluorescent properties, singlet oxygen generation, and photocytotoxicity, was approximately maintained. Confocal imaging and FACS analysis showed that Ac-HA-Pba nanogels were rapidly internalized into HeLa cells via an HA-induced endocytosis mechanism, a process which could be blocked with the application of an excess of HA polymer. The results of the study indicate that HA-based nanogels can potentially be applied in photodynamic therapy (PDT).

Self-quenching polysaccharide-based nanogels of pullulan/folate-photosensitizer conjugates for photodynamic therapy.

Self-quenching polysaccharide-based nanogels synthesized from pullulan/folate-pheophorbide-a (Pheo-A) conjugates were investigated for their potential to reduce photosensitizer (PS) phototoxicity in normal tissue and to enhance the efficacy of tumor treatment. While the nanogels showed photoactive properties including fluorescence and singlet oxygen generation in organic solvent (DMF), these properties were suppressed in PBS due to the self-quenching of photosensitizer moieties similar to the fluorescence resonance energy transfer (FRET) effect. When the PFP2 nanogel was co-incubated with esterase or HeLa cancer cells, its photoactivity was restored. These results demonstrate that the nanogel was internalized in cancer cells by folate receptor-mediated endocytosis and was then disintegrated by various enzymes in the lysosome, leading to restoration of photoactivity. In an in vivo study, free Pheo-A showed fluorescence immediately after injection; however, nanogel fluorescence was detected 30 min after injection, increased significantly over 12 h, and was maintained beyond 3 weeks. The phototoxic properties of the nanogel were similar to those of free Pheo-A, resulting in an IC(50) < 0.25 and apoptic cell death. Based on these results, we suggest that self-quenching PFP nanogels can be used to design new photodynamic therapies with minimal unfavorable phototoxicity.

Cancer cell specific targeting of nanogels from acetylated hyaluronic acid with low molecular weight.

In order to develop a novel self-assembly as a means of cancer cell targeting, self-organized nanogels were prepared from acetylated hyaluronic acid with low molecular weight (AC-HA(LM)). Three samples were obtained (AC-HA(LM)1, 2 and 3) with degrees of acetylation, 0.8, 2.1, or 2.6 acetyl groups per unit (2 glucose rings) of HA(LM) to control their hydrophobicity. The mean diameters of AC-HA(LM)2 and 3 were less than 300 nm with unimodal size distribution, while that of AC-HA(LM)1 was above 400 nm. The critical aggregation concentrations (CAC) of the nanogels in distilled water were < 1 x 10(-1) mg/mL. The doxorubicine (DOX) loading efficiencies and loading contents of AC-HA(LM) increased as the degree of acetylation increased, in particular, the loading efficiency of AC-HA(LM)3 reached above 90%. AC-HA(LM)3 nanogels showed IC(50) at 1300 ng/mL of the DOX concentration against HeLa cells (with HA-binding receptors) similar to free DOX. For monitoring of specific interaction with a carcinoma cell line (HeLa cells with HA-binding receptors), AC-HA(LM)3 was labeled with FITC and observed with a confocal microscope. HeLa cells were strongly luminated by interactions with fluorescence-labeled AC-HA(LM)3 nanogels; however, this luminance was significantly decreased by competition inhibition of free HA. This result indicates that modified HA maintains the ability to interact with HA-binding receptors. The selective cytotoxicity and interaction of AC-HA(LM) nanogels may help reduce side effects of anti-cancer drugs in clinical use.