Kuiwon Choi

Antitumor efficacy of cisplatin-loaded glycol chitosan nanoparticles in tumor-bearing mice

To make a tumor targeting nano-sized drug delivery system, biocompatible and biodegradable glycol chitosan (M(w)=250 kDa) was modified with hydrophobic cholanic acid. The resulting hydrophobically modified glycol chitosans (HGCs) that formed nano-sized self-aggregates in an aqueous medium were investigated as an anticancer drug carrier in cancer treatment. Insoluble anticancer drug, cisplatin (CDDP), was easily encapsulated into the hydrophobic cores of HGC nanoparticles by a dialysis method, wherein the drug loading efficiency was about 80%. The CCDP-encapsulated HGC (CDDP-HGC) nanoparticles were well-dispersed in aqueous media and they formed a nanoparticles structure with a mean diameter about 300-500 nm. As a nano-sized drug carrier, the CDDP-HGC nanoparticles released the drug in a sustained manner for a week and they were also less cytotoxic than was free CDDP, probably because of sustained release of CDDP from the HGC nanoparticles. The tumor targeting ability of CDDP-HGC nanoparticles was confirmed by in vivo live animal imaging with near-infrared fluorescence Cy5.5-labeled CDDP-HGC nanoparticles. It was observed that CDDP-HGC nanoparticles were successfully accumulated by tumor tissues in tumor-bearing mice, because of the prolonged circulation and enhanced permeability and retention (EPR) effect of CDDP-HGC nanoparticles in tumor-bearing mice. As expected, the CDDP-HGC nanoparticles showed higher antitumor efficacy and lower toxicity compared to free CDDP, as shown by changes in tumor volumes, body weights, and survival rates, as well as by immunohistological TUNEL assay data. Collectively, the present results indicate that HGC nanoparticles are a promising carrier for the anticancer drug CDDP.

A Near‐Infrared‐Fluorescence‐Quenched Gold‐Nanoparticle Imaging Probe for In Vivo Drug Screening and Protease Activity Determination

Nanoscale fluorescence optical imaging probes are paving the way for novel methods to sense and spot live molecular targets. Various probes have been developed, including semiconductor quantum dots, magnetofluorescent nanoparticles, polymer conjugates, nanocomplexes, and gold nanoparticles (AuNPs). The application of conventional fluorescent probes is limited because they generally display only modest fluorescence changes, thus providing insufficient resolution. The limited degree of resolution is mainly attributed to the low fluorescence-quenching efficiency and specificity of the probes. Therefore, a high quenching efficiency and specific recognition properties by the target biomolecules are essential for the development of supersensitive fluorescence-based probes. Among the diverse candidates, biocompatible AuNPs offer a considerable advantage in obtaining optical images through their nearinfrared-fluorescence (NIRF) quenching properties. Chromophores in close proximity to AuNPs experience strong electronic interactions with the surface, which results in donation of excited electrons to the metal nanoparticles and almost perfect quenching of the fluorescence. However, the use of AuNP probes for in vivo visual biomolecular detection and real-time fluorescence tomography remains to be explored. Herein, we describe the development of a proteasesensitive selfand AuNP-quenched NIRF probe. Proteases— or their inhibitors—are mainly involved in cancer, inflammation, and vascular disease. Sensitive, convenient, and accurate protease-detection systems constitute a crucial tool for the development of drug-screening systems and the early diagnosis of diseases, such as cancer. The most common detection method for protease activity is the use of small peptide substrates containing chromophores at their termini. We previously reported proteaseand kinase-activating sensory systems based on the fluorescence resonance energy transfer (FRET) properties of NIRF Cy or isothiocyanate dyes. Although these systems are sensitive, their applications are limited because of the modest fluorescent changes (which are too weak to be used in vivo). Therefore, a decrease in the noise intensity of the quenched state—to an undetectable level—is required to maximize the fluorescent changes and achieve an efficient in vivo detection of small amounts of protease. Herein, we propose an alternative, simple, robust, and one-step optical fluorescence nanoprobe to be used in: 1) inhibitor drug screening, 2) the detection of target proteases, and 3) the early diagnosis of cancer. The system Cy5.5-substrate/AuNP is believed to induce a strong multi-quenched state, because the AuNPs serve as ultra-efficient quenchers of the molecular excitation energy in a chromophore through their surface-energy-transfer properties, and the Cy5.5 dye, loaded onto the AuNP surfaces, can be self-quenched as a result of a combination of the staticquenching and FRET mechanisms. When the target proteases meet functionalized AuNP probes, cleavage of the Cy5.5-substrate occurs as a consequence of the specific substrate recognition by the protease. This cleavage is manifested in the form of a pronounced NIRF signal recovery caused by dequenching of the NIRF dyes (Figure 1A). To demonstrate the utility of our rationale, we developed a matrix metalloprotease (MMP) fluorescence imaging probe based on AuNPs. MMPs are a family of zinc-dependent endopeptidases that play key roles in several biological processes. In particular, because of their significant role in promoting cancer progression, MMPs have become important targets for new drug development and in vivo tumor diagnosis. We prepared AuNPs (20 nm) stabilized with a Cy5.5substrate, namely, Cy5.5-Gly-Pro-Leu-Gly-Val-Arg-Gly-Cys(amide), where the core-specific substrate, that is, Pro-LeuGly-Val-Arg, shows selectivity for MMP (see the Supporting Information). Transmission electron microscopy (TEM) [*] Dr. S. Lee, Dr. K. Park, S.-Y. Lee, Dr. K. Choi, Dr. I. C. Kwon, Dr. K. Kim Biomedical Research Center Korea Institute of Science and Technology 39-1 Hawolgok-dong, Seongbuk-gu, Seoul, 136-791 (Korea) Fax: (+82)2-958-5909 E-mail: kim@kist.re.kr E.-J. Cha, J.-K. Hong, I.-C. Sun, Prof. C.-H. Ahn Department of Materials Science and Engineering Seoul National University San 56-1, Sillim, Gwanak, Seoul 151-744 (Korea) Fax: (+82) 2-883-8197 E-mail: chahn@snu.ac.kr

Smart Nanocarrier Based on PEGylated Hyaluronic Acid for Cancer Therapy

Tumor targetability and site-specific drug release of therapeutic nanoparticles are key factors for effective cancer therapy. In this study, poly(ethylene glycol) (PEG)-conjugated hyaluronic acid nanoparticles (P-HA-NPs) were investigated as carriers for anticancer drugs including doxorubicin and camptothecin (CPT). P-HA-NPs were internalized into cancer cells (SCC7 and MDA-MB-231) via receptor-mediated endocytosis, but were rarely taken up by normal fibroblasts (NIH-3T3). During in vitro drug release tests, P-HA-NPs rapidly released drugs when incubated with cancer cells, extracts of tumor tissues, or the enzyme Hyal-1, which is abundant in the intracellular compartments of cancer cells. CPT-loaded P-HA-NPs (CPT-P-HA-NPs) showed dose-dependent cytotoxicity to cancer cells (MDA-MB-231, SCC7, and HCT 116) and significantly lower cytotoxicity against normal fibroblasts (NIH-3T3) than free CPT. Unexpectedly, high concentrations of CPT-P-HA-NPs demonstrated greater cytotoxicity to cancer cells than free CPT. An in vivo biodistribution study indicated that P-HA-NPs selectively accumulated into tumor sites after systemic administration into tumor-bearing mice, primarily due to prolonged circulation in the blood and binding to a receptor (CD44) that was overexpressed on the cancer cells. In addition, when CPT-P-HA-NPs were systemically administrated into tumor-bearing mice, we saw no significant increases in tumor size for at least 35 days, implying high antitumor activity. Overall, P-HA-NPs showed promising potential as a drug carrier for cancer therapy.

Tumor-homing multifunctional nanoparticles for cancer theragnosis: Simultaneous diagnosis, drug delivery, and therapeutic monitoring.

Theragnostic multifunctional nanoparticles hold great promise in simultaneous diagnosis of disease, targeted drug delivery with minimal toxicity, and monitoring of treatment. One of the current challenges in cancer treatment is enhancing the tumor-specific targeting of both imaging probes and anticancer agents. Herein, we report tumor-homing chitosan-based nanoparticles (CNPs) that simultaneously execute cancer diagnosis and therapy (cancer theragnosis). These CNPs are unique for their three distinctive characteristics, such as stability in serum, deformability, and rapid uptake by tumor cells. These properties are critical in increasing their tumor targeting specificity and reducing their nonspecific uptake by normal tissues. To develop these CNPs into novel theragnostic nanoparticles, we labeled them with Cy5.5, a near-infrared fluorescent (NIRF) dye, for imaging and also loaded them with paclitaxel (PTX-CNPs), an anticancer drug, for cancer treatment. Cy5.5 labeled PTX-CNPs exhibited significantly increased tumor-homing ability with low nonspecific uptake by other tissues in SCC7 tumor-bearing mice. Theragnostic nanoparticles, Cy5.5 labeled PTX-CNPs, are highly useful for simultaneous diagnosis of early-stage cancer and drug delivery.

PEGylation of hyaluronic acid nanoparticles improves tumor targetability in vivo

A major drawback of hyaluronic acid (HA)-based drug conjugates or nanoparticles for cancer therapy is their preferential accumulation in the liver after systemic administration. In an attempt to investigate the physicochemical characteristics and in vivo fates of poly(ethylene glycol) (PEG)-conjugated HA nanoparticles (HA-NPs), amphiphilic HA derivatives were prepared by varying the degree of PEGylation. The PEGylated HA-NPs formed self-assembled nanoparticles (217-269 nm in diameter) with the negatively charged surfaces in the physiological condition. Although PEGylation of HA-NPs reduced their cellular uptake in vitro, larger amounts of nanoparticles were taken up by cancer cells over-expressing CD44, an HA receptor, than by normal fibroblast cells. The ex vivo images of the organs using an optical imaging technique after the intravenous injection of Cy5.5-labeled nanoparticles into normal mice demonstrated that PEGylation could effectively reduce the liver uptake of HA-NPs and increase their circulation time in the blood. When the nanoparticles were systemically administered into tumor-bearing mice for in vivo real-time imaging, the strongest fluorescence signals were detected at the tumor site of the mice for the whole period of time studied, indicating their high tumor targetability. Interestingly, PEGylated HA-NPs were more effectively accumulated into the tumor tissue up to 1.6-fold higher than bare HA-NPs. The high tumor targetability of PEGylated HA-NPs was further supported by the intravital tumor imaging, in which their rapid extravasation into the tumor tissue was clearly observed. These results suggest that PEGylated HA-NPs can be useful as a means for cancer therapy and diagnosis.

Self-assembled glycol chitosan nanoparticles for the sustained and prolonged delivery of antiangiogenic small peptide drugs in cancer therapy.

Antiangiogenic peptide drugs have received much attention in the fields of tumor therapy and tumor imaging because they show promise in the targeting of integrins such as alpha(v)beta(3) on angiogenic endothelial cells. However, systemic antiangiogenic peptide drugs have short half-lives in vivo, resulting in fast serum clearance via the kidney, and thus the therapeutic effects of such drugs remain modest. In this study, we prepared self-assembled glycol chitosan nanoparticles and explored whether this construct might function as a prolonged and sustained drug delivery system for RGD peptide, used as an antiangiogenic model drug in cancer therapy. Glycol chitosan hydrophobically modified with 5beta-cholanic acid (HGC) formed nanoparticles with a diameter of 230 nm, and RGD peptide was easily encapsulated into HGC nanoparticles (yielding RGD-HGC nanoparticles) with a high loading efficiency (>85%). In vitro work demonstrated that RGD-HGC showed prolonged and sustained release of RGD, lasting for 1 week. RGD-HGC also inhibited HUVEC adhesion to a beta ig-h3 protein-coated surface, indicating an antiangiogenic effect of the RGD peptide in the HGC nanoparticles. In an in vivo study, the antiangiogenic peptide drug formulation of RGD-HGC markedly inhibited bFGF-induced angiogenesis and decreased hemoglobin content in Matrigel plugs. Intratumoral administration of RGD-HGC significantly decreased tumor growth and microvessel density compared to native RGD peptide injected either intravenously or intratumorally, because the RGD-HGC formulation strongly enhanced the antiangiogenic and antitumoral efficacy of RGD peptide by affording prolonged and sustained RGD peptide delivery locally and regionally in solid tumors.

Tumor-Targeting Peptide Conjugated pH-Responsive Micelles as a Potential Drug Carrier for Cancer Therapy

Herein, we prepared tumor-targeting peptide (AP peptide; CRKRLDRN) conjugated pH-responsive polymeric micelles (pH-PMs) in cancer therapy by active and pH-responsive tumor targeting delivery systems, simultaneously. The active tumor targeting and tumoral pH-responsive polymeric micelles were prepared by mixing AP peptide conjugated PEG-poly(d,l-lactic acid) block copolymer (AP-PEG-PLA) into the pH-responsive micelles of methyl ether poly(ethylene glycol) (MPEG)-poly(beta-amino ester) (PAE) block copolymer (MPEG-PAE). These mixed amphiphilic block copolymers were self-assembled to form stable AP peptide-conjugated and pH-responsive AP-PEG-PLA/MPEG-PAE micelles (AP-pH-PMs) with an average size of 150 nm. The AP-pH-PMs containing 10 wt % of AP-PEG-PLA showed a sharp pH-dependent micellization/demicellization transition at the tumoral acid pH. Also, they presented the pH-dependent drug release profile at the acidic pH of 6.4. The fluorescence dye, TRITC, encapsulated AP-pH-PMs (TRITC-AP-pH-PMs) presented the higher tumor-specific targeting ability in vitro cancer cell culture system and in vivo tumor-bearing mice, compared to control pH-responsive micelles of MPEG-PAE. For the cancer therapy, the anticancer drug, doxorubicin (DOX), was efficiently encapsulated into the AP-pH-PMs (DOX-AP-pH-PMs) with a higher loading efficiency. DOX-AP-pH-PMs efficiently deliver anticancer drugs in MDA-MB231 human breast tumor-bearing mice, resulted in excellent anticancer therapeutic efficacy, compared to free DOX and DOX encapsulated MEG-PAE micelles, indicating the excellent tumor targeting ability of AP-pH-PMs. Therefore, these tumor-targeting peptide-conjugated and pH-responsive polymeric micelles have great potential application in cancer therapy.

Self-assembled hyaluronic acid nanoparticles as a potential drug carrier for cancer therapy: synthesis, characterization, and in vivo biodistribution

To develop a nano-sized drug delivery system for cancer therapy, amphiphilic hyaluronic acid conjugates were synthesized by chemical conjugation of hydrophobic 5β-cholanic acid to the backbone of hyaluronic acid (HA). The HA conjugates could form nano-sized self-aggregates under physiological conditions (PBS, pH = 7.4, 37 °C) via the hydrophobic interaction among 5β-cholanic acids. The HA nanoparticles were spherical in shape and their sizes were in the range of 350–400 nm, depending on the degree of substitution of 5β-cholanic acid. From a cellular experiment using Cy5.5-labeled HA nanoparticles, it was demonstrated that they are efficiently taken up by SCC7 cancer cells which over-express CD44, the receptor for HA. When the Cy5.5-labeled HA nanoparticles were systemically administrated into the tail vein of tumor-bearing mice, most of the nanoparticles were found in tumor and liver sites. In particular, the fluorescence intensity of nanoparticles at the tumor site was 4-fold higher than that of pure HA polymer, which was confirmed by a non-invasive near-infrared fluorescence imaging system. The high tumor targeting ability of HA nanoparticles might result from both their prolonged circulation in blood and high affinity to tumor cells. These results reveal the promising potential of HA nanoparticles as a stable and effective nano-sized drug delivery system for cancer treatment.

Tumor-targeting hyaluronic acid nanoparticles for photodynamic imaging and therapy

Tumor-targeted imaging and therapy have been the challenging issue in the clinical field. Herein, we report tumor-targeting hyaluronic acid nanoparticles (HANPs) as the carrier of the hydrophobic photosensitizer, chlorin e6 (Ce6) for simultaneous photodynamic imaging and therapy. First, self-assembled HANPs were synthesized by chemical conjugation of aminated 5β-cholanic acid, polyethylene glycol (PEG), and black hole quencher3 (BHQ3) to the HA polymers. Second, Ce6 was readily loaded into the HANPs by a simple dialysis method resulting in Ce6-loaded hyaluronic acid nanoparticles (Ce6-HANPs), wherein in the loading efficiency of Ce6 was higher than 80%. The resulting Ce6-HANPs showed stable nano-structure in aqueous condition and rapid uptake into tumor cells. In particular Ce6-HANPs were rapidly degraded by hyaluronidases abundant in cytosol of tumor cells, which may enable intracellular release of Ce6 at the tumor tissue. After an intravenous injection into the tumor-bearing mice, Ce6-HANPs could efficiently reach the tumor tissue via the passive targeting mechanism and specifically enter tumor cells through the receptor-mediated endocytosis based on the interactions between HA of nanoparticles and CD44, the HA receptor on the surface of tumor cells. Upon laser irradiation, Ce6 which was released from the nanoparticles could generate fluorescence and singlet oxygen inside tumor cells, resulting in effective suppression of tumor growth. Overall, it was demonstrated that Ce6-HANPs could be successfully applied to in vivo photodynamic tumor imaging and therapy simultaneously.

Comparative study of photosensitizer loaded and conjugated glycol chitosan nanoparticles for cancer therapy.

This study reports that tumor-targeting glycol chitosan nanoparticles with physically loaded and chemically conjugated photosensitizers can be used in photodynamic therapy (PDT). First, the hydrophobic photosensitizer, chlorin e6 (Ce6), was physically loaded onto the hydrophobically-modified glycol chitosan nanoparticles (HGC), which were prepared by self-assembling amphiphilic glycol chitosan-5β-cholanic acid conjugates under aqueous conditions. Second, the Ce6s were chemically conjugated to the glycol chitosan polymers, resulting in amphiphilic glycol chitosan-Ce6 conjugates that formed self-assembled nanoparticles in aqueous condition. Both Ce6-loaded glycol chitosan nanoparticles (HGC-Ce6) and Ce6-conjugated chitosan nanoparticles (GC-Ce6) had similar average diameters of 300 to 350 nm, a similar in vitro singlet oxygen generation efficacy under buffer conditions, and a rapid cellular uptake profile in the cell culture system. However, compared to GC-Ce6, HGC-Ce6 showed a burst of drug release in vitro, whereby 65% of physically loaded drugs were rapidly released from the particles within 6.5h in the buffer condition. When injected through the tail vein into tumor bearing mice, HGC-Ce6 did not accumulate efficiently in tumor tissue, reflecting the burst in the release of the physically loaded drug, while GC-Ce6 showed a prolonged circulation profile and a more efficient tumor accumulation, which resulted in high therapeutic efficacy. These comparative studies with drug-loaded and drug-conjugated nanoparticles showed that the photosensitizer-conjugated glycol chitosan nanoparticles with excellent tumor targeting properties have potential for PDT in cancer treatment.