Preparation of Chondroitin Sulfate-Glycyl-Prednisolone Conjugate Nanogel and Its Efficacy in Rats with Ulcerative Colitis.

A conjugate between chondroitin sulfate (CS) and glycyl-prednisolone (GP), named CS-GP, was produced by carbodiimide coupling at a high GP/CS ratio. CS-GP was not water-soluble and gave a nanogel (NG) in aqueous solution. Two types of nanogels, NG(I) and NG(II), with prednisolone (PD) contents of 5.5 and 21.1% (w/w), respectively, were obtained. They had particle sizes of approximately 280 and 570 nm, respectively, and showed negative ζ-potentials of approximately -40 mV. The PD release rate was slower in the nanogels than in a solution of CS-GP with a PD content of 1.4% (w/w). The PD release rate was slower in NG(II) than in NG(I), and was elevated at pH 7.4 than at pH 6.8. NG(II) was applied in vivo to rats with trinitrobenzene sulfonic acid (TNBS)-induced colitis, and its therapeutic efficacy and pharmacokinetic features were investigated. The therapeutic efficacy of NG(II) was slightly better than that of PD alone. Drug delivery to the lower intestines was enhanced with NG(II). The CS-GP nanogel has potential as a potent DDS for the treatment of ulcerative colitis.

Tumor delivery of liposomal doxorubicin prepared with poly-L-glutamic acid as a drug-trapping agent.

CONTEXT: Poly-l-glutamic acid (PGA) is an anionic polymer with a large number of carboxyl groups that can interact electrostatically with cationic drugs such as doxorubicin (DOX). OBJECTIVE: For stable encapsulation of DOX into liposomes, we prepared triethylamine (TEA)-PGA-liposomes using PGA as an internal trapping agent. METHODS: We prepared TEA-PGA-liposomes by remote loading of DOX with a TEA gradient into preformed liposomes prepared with 1, 2, or 4 mg/mL PGA (molecular weights 4800, 9800, and 20 500), and evaluated their biodistribution and antitumor effects on Lewis lung carcinoma (LLC) tumor-bearing mice. RESULTS: TEA-PGA-liposomes using the higher the molecular weight or concentration of PGA showed a slower release of DOX from the liposomes. TEA-PGA-liposomes prepared with a high concentration of PGA could enhance DOX accumulation in tumors and prolonged DOX circulation in the serum, indicating that DOX may be retained stably in the liposomal interior by interaction with PGA. Furthermore, injection of TEA-PGA-liposomes prepared with 4 mg/mL of PGA9800 or 2 mg/mL PGA20500 strongly inhibited tumor growth in LLC tumor-bearing mice. CONCLUSIONS: PGA may be a potential trapping agent for liposomal DOX for tumor drug delivery.

Membrane Microdomain Structures of Liposomes and Their Contribution to the Cellular Uptake Efficiency into HeLa Cells.

The purpose of this study is to obtain a comprehensive relationship between membrane microdomain structures of liposomes and their cellular uptake efficiency. Model liposomes consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/cholesterol (Ch) were prepared with various lipid compositions. To detect distinct membrane microdomains in the liposomes, fluorescence-quenching assays were performed at temperatures ranging from 25 to 60 °C using 1,6-diphenyl-1,3,5-hexatriene-labeled liposomes and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl. From the data analysis using the response surface method, we gained a better understanding of the conditions for forming distinct domains (Lo, Ld, and gel phase membranes) as a function of lipid composition. We further performed self-organizing maps (SOM) clustering to simplify the complicated behavior of the domain formation to obtain its essence. As a result, DPPC/DOPC/Ch liposomes in any lipid composition were integrated into five distinct clusters in terms of similarity of the domain structure. In addition, the findings from synchrotron small-angle X-ray scattering analysis offered further insight into the domain structures. As a last phase of this study, an in vitro cellular uptake study using HeLa cells was conducted using SOM clusters' liposomes with/without PEGylation. As a consequence of this study, higher cellular uptake was observed from liposomes having Ch-rich ordered domains.

siRNA delivery into tumor cells by cationic cholesterol derivative-based nanoparticles and liposomes.

Previously, we reported that cationic nanoparticles (NP) composed of diamine-type cholesteryl-3-carboxamide (OH-Chol, N-(2-(2-hydroxyethylamino)ethyl)cholesteryl-3-carboxamide) and Tween 80 could deliver small interfering RNA (siRNA) with high transfection efficiency into tumor cells. In this study, we synthesized new diamine-type cationic cholesteryl carbamate (OH-C-Chol, cholesteryl (2-((2-hydroxyethyl)amino)ethyl)carbamate) and triamine-type carbamate (OH-NC-Chol, cholesteryl (2-((2-((2-hydroxyethyl)amino)ethyl)amino)ethyl)carbamate), and prepared cationic nanoparticles composed of OH-C-Chol or OH-NC-Chol with Tween 80 (NP-C and NP-NC, respectively), as well as cationic liposomes composed of OH-C-Chol or OH-NC-Chol with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) (LP-C and LP-NC, respectively) for evaluation of their possible use as siRNA delivery vectors. LP-C and LP-NC/siRNA complexes (lipoplexes) exhibited larger gene silencing effects than NP-C and NP-NC/siRNA complexes (nanoplexes), respectively, in human breast tumor MCF-7 cells, although the NP-C nanoplex showed high association with the cells. In particular, LP-NC lipoplex could induce strong gene suppression, even at a concentration of 5 nM siRNA. From these results, cationic liposomes composed of OH-NC-Chol and DOPE may have potential as gene vectors for siRNA transfection to tumor cells.

Evaluation of antitumor effect of zoledronic acid entrapped in folate-linked liposome for targeting to tumor-associated macrophages.

In this study, we investigated the possibility of whether depletion of tumor-associated macrophages (TAMs) by zoledronic acid (ZOL) entrapped in folate-linked liposome could inhibit tumor angiogenesis and consequently tumor growth. Abundant expression of folate receptor ß (FRß) mRNA was detected in tumor tissues from subcutaneously implanted FR-negative tumor cells in mice, indicating that FRß mRNA was expressed in TAMs, not in tumor cells. When fluorescent-labeled folic acid was intravenously injected into mice bearing FR-positive human nasopharyngeal tumor KB, and FR-negative human prostate tumor PC-3 and mouse colon adenocarcinoma Colon 26, fluorescence was strongly detected in KB and Colon 26 tumors, and moderately in PC-3 tumor, indicating that folic acid was taken up by TAMs via FRß in PC-3 and Colon 26 tumors. For evaluation of ZOL delivery to TAMs, folate-linked liposomal ZOL (FL-ZOL) for TAM targeting and non-folate-linked liposomal ZOL (L-ZOL) as a control were prepared by incorporation with 0.5 mol% folate-PEG2000-DSPE and 0.5 mol% PEG2000-DSPE, respectively, into the liposomal formulation of egg phosphatidylcholine and cholesterol. FL-ZOL showed high cytotoxicity for KB and murine macrophage RAW264.7 cells, but not for Colon 26 cells, suggested that FL-ZOL was selectively taken up via FR-mediated endocytosis. However, injections of FL-ZOL and L-ZOL did not induce antitumor activities for KB and Colon 26 tumor-bearing mice, and had a lethal effect by high toxicity. From these findings, the severe in vivo toxicity of liposomal ZOL limited its utility for in vivo TAM targeting, although FL-ZOL could selectively induce in vitro cytotoxicity via FR.

siRNA delivery to lung-metastasized tumor by systemic injection with cationic liposomes.

CONTEXT: Cationic liposomes can efficiently deliver siRNA to the lung by intravenous injection of cationic liposome/siRNA complexes (lipoplexes). OBJECTIVE: The aim of this study was to examine a formulation of cationic liposomes for siRNA delivery to lung metastasis of breast tumor. MATERIALS AND METHODS: For the preparation of cationic liposomes, 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or dimethyldioctadecylammonium bromide (DDAB) as a cationic lipid and cholesterol (Chol) or 1,2-dioleoyl-L-α-glycero-3-phosphatidylethanolamine (DOPE) as a neutral lipid were used. In vitro and in vivo gene silencing effects by cationic lipoplexes were evaluated after transfection into stably luciferase-expressing human breast tumor MCF-7-Luc cells and after intravenous injection into mice with lung MCF-7-Luc metastasis, respectively. Intracellular localization of siRNA after transfection into MCF-7 cells by cationic lipoplexes and biodistribution of siRNA after intravenous injection of cationic lipoplexes into the mice with lung metastasis were examined by confocal and fluorescent microscopy analyses, respectively. RESULTS: In in vitro transfection, DOTAP/DOPE and DDAB/DOPE lipoplexes of luciferase siRNA strongly suppressed luciferase activity in MCF-7-Luc cells, but DOTAP/Chol and DDAB/Chol lipoplexes did not, although DOTAP/Chol and DDAB/Chol lipoplexes exhibited higher cellular uptake than DOTAP/DOPE and DDAB/DOPE lipoplexes. When their cationic lipoplexes were intravenously injected into mice with lung MCF-7-Luc metastasis, siRNAs were mainly accumulated in the lungs; however, the reduced luciferase activities in the lung-metastasized tumors were observed only by injections of DOTAP/Chol and DOTAP/DOPE lipoplexes, but not by DDAB/Chol and DDAB/DOPE lipoplexes. CONCLUSIONS: DOTAP-based liposomes might be useful as an in vivo siRNA delivery carrier that can induce gene silencing in lung-metastasized tumors.

Development of liposomal nanoconstructs targeting P-selectin (CD62P)-expressing cells by using a sulfated derivative of sialic acid.

PURPOSE: NMSO3, a sulfated derivative of sialic acid, is a specific inhibitor for P-selectin (CD62P)-mediated cell adhesion. We attempted to apply liposomes modified with NMSO3 for selective targeting of activated platelets. METHODS: The binding of fluorescently labeled NMSO3-containing liposomes (NMSO3-liposomes) to CHO cells expressing P-selectin (CHO-P cells) and activated platelets were examined. The distribution of NMSO3-liposomes incorporated into the cells was observed by fluorescence microscopy. RESULTS: The binding assay revealed that NMSO3-liposomes specifically bound to immobilized P-selectin and CHO-P cells in a dose-dependent manner. The binding of NMSO3-liposomes to CHO-P cells was much stronger than that to the parental CHO-K1 cells. Fluorescence microscopic observation showed that NMSO3-liposomes were incorporated into CHO-P cells after the binding and distributed throughout the cytoplasm of the cell. NMSO3-liposomes bound more strongly to thrombin-activated platelets than to resting platelets, as assessed by flow cytometry. CONCLUSIONS: These results suggest that NMSO3-liposomes can be applied for selective drug delivery to activated platelets.

Folate-targeted gadolinium-lipid-based nanoparticles as a bimodal contrast agent for tumor fluorescent and magnetic resonance imaging.

To enhance tumor magnetic resonance imaging (MRI) signals via the selective accumulation of contrast agents, we prepared folate-modified gadolinium-lipid-based nanoparticles as MRI contrast agents. Folate-modified nanoparticles were comprised of polyethylene glycol (PEG)-lipid, gadolinium diethylenetriamine pentaacetic acid lipid, cationic cholesterol derivatives, folate-conjugated PEG-lipid, and Cy7-PEG-lipid. Folate receptor-mediated cellular nanoparticle association was examined in KB cells, which overexpress the folate receptor. The biodistribution of nanoparticles after their intravenous injection into KB tumor-bearing mice was measured. Mice were imaged through in vivo fluorescence imaging and MRI 24 h after nanoparticle injection, and the intensity enhancement of the tumor MRI signal was evaluated. Increased cellular association of folate-modified nanoparticles was inhibited by excess free folic acid, indicating that nanoparticle association was folate receptor-mediated. Irrespective of folate modification, the amount of nanoparticles in blood 24 h after injection was ca. 10% of the injected dose. Compared with non-modified nanoparticles, folate-modified nanoparticles exhibited significant accumulation in tumor tissues without altering other biodistribution, as well as enhanced tumor fluorescence and MRI signal intensity. The results support the feasibility of MRI- and in vivo fluorescence imaging-based tumor visualization using folate-modified nanoparticles and provide opportunities to develop folate targeting-based imaging applications.

Development of high boron content liposomes and their promising antitumor effect for neutron capture therapy of cancers.

Mercaptoundecahydrododecaborate (BSH)-encapsulating 10% distearoyl boron lipid (DSBL) liposomes were developed as a boron delivery vehicle for neutron capture therapy. The current approach is unique because the liposome shell itself possesses cytocidal potential in addition to its encapsulated agents. BSH-encapsulating 10% DSBL liposomes have high boron content (B/P ratio: 2.6) that enables us to prepare liposome solution with 5000 ppm boron concentration. BSH-encapsulating 10% DSBL liposomes displayed excellent boron delivery efficacy to tumor: boron concentrations reached 174, 93, and 32 ppm at doses of 50, 30, and 15 mg B/kg, respectively. Magnescope was also encapsulated in the 10% DSBL liposomes and the real-time biodistribution of the Magnescope-encapsulating DSBL liposomes was measured in a living body using MRI. Significant antitumor effect was observed in mice injected with BSH-encapsulating 10% DSBL liposomes even at the dose of 15 mg B/kg; the tumor completely disappeared three weeks after thermal neutron irradiation ((1.5-1.8) × 10(12) neutrons/cm(2)). The current results enabled us to reduce the total dose of liposomes to less than one-fifth compared with that of the BSH-encapsulating liposomes without reducing the efficacy of boron neutron capture therapy (BNCT).

Effect of PEG anchor in PEGylation of folate-modified cationic liposomes with PEG-derivatives on systemic siRNA delivery into the Tumor.

In this study, we prepared small interfering RNA (siRNA)/cationic liposome complexes (lipoplexes) modified with folate (FA)-polyethylene glycol (PEG, MW 2000, 3400 or 5000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) to facilitate their uptake into tumor cells via folate receptor (FR), and with PEG1600-cholesterol (PEG1600-Chol) or PEG2000-chondroitin sulfate conjugate (PEG2000-CS), to enhance their systemic stability. Among the FA-PEG-modified siRNA lipoplexes, 0.5 mol% FA-PEG5000-DSPE-modified lipoplexes with 2.5 mol% PEG2000-CS or PEG1600-Chol (LP-0.5F5/2.5P2-CS and LP-0.5F5/2.5P1.6-CL, respectively) exhibited selective growth inhibition of human nasopharyngeal carcinoma KB cells through transduction with polo-like kinase 1 (PLK1) siRNA. Furthermore, the LP-0.5F5/2.5P2-CS and LP-0.5F5/2.5P1.6-CL lipoplexes exhibited decreased agglutination with erythrocytes through PEGylation, and markedly decreased the accumulation of siRNA in murine lungs after systemic injection. Finally, systemic injection of LP-0.5F5/2.5P2-CS and LP-0.5F5/2.5P1.6-CL lipoplexes resulted in accumulation of siRNA in KB tumor xenografts. These findings suggest that PEGylation of FA-PEG5000-DSPE-modified siRNA lipoplexes with PEG2000-CS or PEG1600-Chol might improve their systemic stability without the loss of selective transfection activity in tumor cells.

Tumor environment changed by combretastatin derivative (Cderiv) pretreatment that leads to effective tumor targeting, MRI studies, and antitumor activity of polymeric micelle carrier systems.

PURPOSE: To evaluate effect of a vascular disrupting agent, a combretastatin derivative (Cderiv), on tumor targeting for polymeric micelle carrier systems, containing either a diagnostic MRI contrast agent or a therapeutic anticancer drug. METHODS: Cderiv was pre-administered 72 h before polymeric micelle MRI contrast agent injection. Accumulation of the MRI contrast agent in colon 26 murine tumor was evaluated with or without pretreatment of Cderiv by ICP and MRI. RESULTS: Significantly higher accumulation of the MRI contrast agent was found in tumor tissues when Cderiv was administered at 72 h before MRI contrast agent injection. T(1)-weighted images of the tumor exhibited substantial signal enhancement in tumor area at 24 h after the contrast agent injection. In T(1)-weighted images, remarkable T(1)-signal enhancements were observed in part of tumor, not in whole tumor. These results indicate that Cderiv pretreatment considerably enhanced the permeability of the tumor blood vessels. Antitumor activity of adriamycin encapsulated polymeric micelles with the Cderiv pretreatment suppressed tumor growth in 44As3 human gastric scirrhous carcinoma-bearing nude mice. CONCLUSIONS: Pretreatment of Cderiv enhanced tumor permeability, resulting in higher accumulation of polymeric micelle carrier systems in solid tumors.

Enhanced antitumor efficacy of folate-linked liposomal doxorubicin with TGF-ß type I receptor inhibitor.

Tumor cell targeting of drug carriers is a promising strategy and uses the attachment of various ligands to enhance the therapeutic potential of chemotherapy agents. Folic acid is a high-affinity ligand for folate receptor, which is a functional tumor-specific receptor. The transforming growth factor (TGF)-ß type I receptor (TßR-I) inhibitor A-83-01 was expected to enhance the accumulation of nanocarriers in tumors by changing the microvascular environment. To enhance the therapeutic effect of folate-linked liposomal doxorubicin (F-SL), we co-administrated F-SL with A-83-01. Intraperitoneally injected A-83-01-induced alterations in the cancer-associated neovasculature were examined by magnetic resonance imaging (MRI) and histological analysis. The targeting efficacy of single intravenous injections of F-SL combined with A-83-01 was evaluated by measurement of the biodistribution and the antitumor effect in mice bearing murine lung carcinoma M109. A-83-01 temporarily changed the tumor vasculature around 3 h post injection. A-83-01 induced 1.7-fold higher drug accumulation of F-SL in the tumor than liposome alone at 24 h post injection. Moreover F-SL co-administrated with A-83-01 showed significantly greater antitumor activity than F-SL alone. This study shows that co-administration of TßR-I inhibitor will open a new strategy for the use of FR-targeting nanocarriers for cancer treatment.

Accelerated blood clearance was not induced for a gadolinium-containing PEG-poly(L-lysine)-based polymeric micelle in mice.

PURPOSE: Accelerated blood clearance (ABC) is induced by repeated injections of PEGylated liposomes. In this study, the ABC was investigated for a gadolinium-containing PEG-poly(L-lysine)-based polymeric micelle (Gd-micelle) and PEGylated liposome (Gd-liposome) in mice. MATERIALS AND METHODS: Effects of the first injection of Gd-micelle on the tissue distribution of the second dose of Gd-micelle were studied. Additionally, effects of the first injection of Gd-micelle, Gd-liposome, empty liposome, polyethyleneglycol (PEG(500,000)), and PEG-lipid on the distribution of the second dose of the Gd-liposome were evaluated. RESULTS: Results indicated that the tissue distribution of the second injection of the Gd-micelle at a dose of 33, 5, or 2 micromol Gd/kg was not affected by the first injection of the Gd-micelle at different doses and time intervals or of the empty PEGylated liposome 7 days before. ABC of Gd-liposome at a dose of 2.3 micromol Gd/kg (corresponding to 10 micromol lipids/kg) was observed when the empty PEGylated liposome or Gd-liposome, but not the Gd-micelle, PEG(500,000) or PEG-lipid, was pre-administered. CONCLUSIONS: The hydrophobic core of the micelle or lipid bilayer of PEGylated liposome has a major effect on this phenomenon. These studies have significant implications for the evaluation of PEG-poly(L-lysine)-based micellar formulation of Gd-based contrast agents.

Development of an in vitro drug release assay of PEGylated liposome using bovine serum albumin and high temperature.

In this study, to establish the conditions of a drug release assay for PEGylated liposome formulations that relates with the drug stability profile in serum in vivo, the influences of incubation temperature and serum protein in the release buffer were examined using liposomal doxorubicin (DXR). In in vitro drug release assays, a PEGylated liposomal DXR in phosphate buffered saline (PBS) at 37 degrees C showed higher drug release rate than non-PEGylated formulation although PEGylated liposomal DXR had higher stability than an equivalent non-PEGylated formulation following intravenous injection. When bovine serum albumin (BSA) and increased temperature, 50 degrees C, were used to accelerate drug release from the liposomes and to mimic in vivo result, non-PEGylated liposomal DXR showed conversely higher release than a PEGylated formulation. Since high temperature increased BSA adsorption onto liposomes, BSA may cause non-PEGylated liposomes instability more than PEGylated ones, resulting in the reverse of the drug release rate of both liposomes. This finding suggested that the conditions in the drug release assay with PEGylated liposomal DXR may be able to be set by a combination of BSA and providing additional thermal energy.

[Tumor permeability of nanocarriers observed by dynamic contrast-enhanced magnetic resonance imaging].

The structure of tumor vasculature is crucial for the nanocarrier-mediated chemotherapy. Recently, transforming growth factor-ß (TGF-ß) inhibitor was reported to increase the tumor accumulation of nanocarriers by changing the structure of tumor vasculature. To identify the parameters of tumor vasculature function following TGF-ß inhibitor (A-83-01) treatment, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was performed using Gd-DTPA and its liposomal formulation (Gd-L) as contrast agents. Observation of tumor MR image before, during, and after injection of contrast agent could calculate the parameters of vascular function, such as volume transfer constant between blood plasma and extracellular space (K(trans)) and fractional plasma volume (v(p)). A-83-01 treatment significantly increased these parameters within 24 h that was positively related to pericyte coverage and tumor cell proliferation. Furthermore, apparent diffusion coefficient (ADC) determined by diffusion-weighed imaging was decreased by A-83-01 treatment, suggesting the decrease of tumor interstitial fluid pressure. Vascular function of the tumor improved by A-83-01 treatment well assessed on post-Gd-L-enhanced MR images, which predicted delivery of liposomal drug to the tumor. These findings suggest that DCE-MRI and, in particular, K(trans) and v(p) quantitation, provide important additional information about tumor vasculature by A-83-01 treatment.

Design of folate-linked liposomal doxorubicin to its antitumor effect in mice.

PURPOSE: Tumor cell targeting is a promising strategy for enhancing the therapeutic potential of chemotherapy agents. Polyethylene glycol (PEG)-coated (sterically stabilized) liposomes show enhanced accumulation on the surface of tumors, but steric hindrance by PEGylation reduces the association of the liposome-bound ligand with its receptor. To increase folate receptor (FR) targeting, we optimized the concentration and PEG spacer length of folate-PEG-lipid in liposomes. EXPERIMENTAL DESIGN: Three types of folate-linked liposomal doxorubicin were designed and prepared by optimizing the concentration and PEG spacer length of folate-PEG-lipid in PEGylated or non-PEGylated liposomes and by masking folate-linked liposomes where the folate ligand is "masked" by adjacent PEG spacers. The liposome targeting efficacy was evaluated in vitro and in vivo. RESULTS: In human oral carcinoma KB cells, which overexpress FR, modification with sufficiently long PEG spacer and a high concentration of folate ligand to non-PEGylated liposomes increased the FR-mediated association and cytotoxicity more than with PEGylated and masked folate-linked liposomes. On the contrary, in mice bearing murine lung carcinoma M109, modification with the folate ligand in PEGylated and masked folate-linked liposomes showed significantly higher antitumor effect than with non-PEGylated liposomes irrespective of the length of time in the circulation after intravenous injection. CONCLUSIONS: The results of this study will be beneficial for the design and preparation of ligand-targeting carriers for cancer treatment.

Implication of spinal protein kinase Cgamma isoform in activation of the mouse brain by intrathecal injection of the protein kinase C activator phorbol 12,13-dibutyrate using functional magnetic resonance imaging analysis.

The aim of the present study was to investigate whether direct activation of protein kinase C (PKC) in the spinal cord could change brain activation using a functional magnetic resonance imaging (fMRI) analysis in mice that lack the PKCgamma gene. The activation of spinal PKC by intrathecal (i.t.) injection with phorbol 12,13-dibutyrate (PDBu), a specific PKC activator, caused a time-dependent decrease in paw-withdrawal latency to the heat thermal stimulus. In contrast, i.t. injection of PDBu failed to cause thermal hyperalgesia in mice which lacked the PKCgamma gene. We found that the i.t. injection with PDBu caused a remarkable increase in the activity of several brain regions in wild-type mice compared with vehicle injection. In the somatosensory cortex and lateral and medial thalamus, i.t. injection of PDBu produced a dramatic and time-dependent increase in signal intensity at 1-6h after i.t. PDBu injection. In contrast, i.t. injection of PDBu produced a delayed but significant increase in signal intensity at 3-6h in the cingulate cortex, at 4-6h in the nucleus accumbens and at 3-6h in the ventral tegmental area. In addition, all effects of PDBu were abolished in mice that lacked the PKCgamma gene. These results suggest that the activation of spinal PKCgamma associated with the activation of ascending pain transmission may be an important factor in chronic pain-like hyperalgesia with changes in emotionality.

Polymeric micelles modified by folate-PEG-lipid for targeted drug delivery to cancer cells in vitro.

A novel technique was developed for the formation of ligand-targeted polymeric micelles that can be applicable to various ligands. For tumor-specific drug delivery, camptothecin (CPT)-loaded polymeric micelles were modified by folate to produce a folate-receptor-targeted drug carrier. Folate-linked PEG5000-distearoylphosphatidylethanolamine (folate-PEG5000-DSPE) was added when preparations of drug-loaded polymeric micelles, resulting in folate ligands exposed to the surface. Folate-modified CPT-loaded polymeric micelles (F-micelle) were evaluated by measuring cellular uptake using a flow cytometer, fluorescence microscopy, and confocal laser scanning microscopy, and by cytotoxicity measurement. The results revealed that F-micelle showed higher cellular uptake in KB cells overexpressing folate receptor (FR) and higher cytotoxicity compared with non-folate modified CPT-loaded polymeric micelles (plain micelles) in KB cells, but not in FR-negative HepG2 cells. This result indicated that polymeric micelles were successfully modified by the folate-linked lipid.

Preparation of chondroitin sulfate-adipic acid dihydrazide-doxorubicin conjugate and its antitumour characteristics against LLC cells.

Macromolecule-antitumour drug conjugates can reach tumour sites specifically via the enhanced permeability and retention (EPR) effect. It is desirable to release the drug efficiently from the conjugate at acidic pH in the tumour tissue or in the endosomes of cancer cells. In this study, we attempted to produce a carrier system with a labile chemical bond at acidic pH. Adipic acid dihydrazide (ADH)-chondroitin sulfate (CS) (termed CS-ACH) was synthesised by a two-step method, with the introduction of formyl groups followed by reductive amination using ADH. Doxorubicin (DOX) was conjugated to CS-ACH by simple mixing at acidic pH. The conjugate, designated CS-ACH-DOX, showed gradual drug release pH dependently at 37 °C; after incubation for seven days, more than 60% of DOX was released at pH 4, whereas less than 20% was released at pH 7. CS-ACH-DOX showed in vitro cytotoxicity against Lewis lung carcinoma (LLC) cells, which was less effective than that of DOX itself. However, CS-ACH-DOX inhibited tumour growth more than DOX in LLC tumour-bearing mice. These results suggested that CS-ACH-DOX might accumulate in tumours via the EPR effect and release DOX effectively at acidic pH. CS-ACH-DOX was considered to act as a drug delivery system with tumour targeting.

Novel ultra-deformable vesicles entrapped with bleomycin and enhanced to penetrate rat skin.

Beta-sitosterol 3-beta-D-glucoside (Sit-G), an absorption enhancer, was incorporated into ultra-deformable vesicles containing bleomycin to attenuate drug toxicity in human keratinocytes. The presence of Sit-G increased drug entrapment and improved in vitro stability of ultra-deformable vesicles. Confocal laser scanning microscopy revealed the extent to which Sit-G facilitated the penetration of ultra-deformable vesicles containing fluorescent probes into rat skin upon non-occlusive topical application. Furthermore, treatment with preparations incorporating Sit-G resulted in elevated epidermal and dermal concentrations of bleomycin. Ultra-deformable formulation contained Sit-G maintained flexibility for penetration through the skin, increased entrapment efficiency of bleomycin and stability in vitro, and significantly increased distribution of bleomycin in epidermis and dermis compared with those without Sit-G.