Development of thermosensitive poly(n-isopropylacrylamide-co-((2-dimethylamino) ethyl methacrylate))-based nanoparticles for controlled drug release.

Thermosensitive nanoparticles based on poly(N-isopropylacrylamide-co-((2-dimethylamino)ethylmethacrylate)) (poly(NIPA-co-DMAEMA)) copolymers were successfully fabricated by free radical polymerization. The lower critical solution temperature (LCST) of the synthesized nanoparticles was 41 °C and a temperature above which would cause the nanoparticles to undergo a volume phase transition from 140 to 100 nm, which could result in the expulsion of encapsulated drugs. Therefore, we used the poly(NIPA-co-DMAEMA) nanoparticles as a carrier for the controlled release of a hydrophobic anticancer agent, 7-ethyl-10-hydroxy-camptothecin (SN-38). The encapsulation efficiency and loading content of SN-38-loaded nanoparticles at an SN-38/poly(NIPA-co-DMAEMA) ratio of 1/10 (D/P = 1/10) were about 80% and 6.293%, respectively. Moreover, the release profile of SN-38-loaded nanoparticles revealed that the release rate at 42 °C (above LCST) was higher than that at 37 °C (below LCST), which demonstrated that the release of SN-38 could be controlled by increasing the temperature. The cytotoxicity of the SN-38-loaded poly(NIPA-co-DMAEMA) nanoparticles was investigated in human colon cancer cells (HT-29) to compare with the treatment of an anticancer drug, Irinotecan(®) (CPT-11). The antitumor efficacy evaluated in a C26 murine colon tumor model showed that the SN-38-loaded nanoparticles in combination with hyperthermia therapy efficiently suppressed tumor growth. The results indicate that these thermo-responsive nanoparticles are potential carriers for controlled drug delivery.

Development of pH sensitive 2-(diisopropylamino)ethyl methacrylate based nanoparticles for photodynamic therapy.

Photodynamic therapy is an effective treatment for tumors that involves the administration of light-activated photosensitizers. However, most photosensitizers are insoluble and non-specific. To target the acid environment of tumor sites, we synthesized three poly(ethylene glycol) methacrylate-co-2-(diisopropylamino)ethyl methacrylate (PEGMA-co-DPA) copolymers capable of self-assembly to form pH sensitive nanoparticles in an aqueous environment, as a means of encapsulating the water-insoluble photosensitizer, meso-tetra(hydroxyphenyl)chlorin (m-THPC). The critical aggregation pH of the PEGMA-co-DPA polymers was 5.8-6.6 and the critical aggregation concentration was 0.0045-0.0089 wt% at pH 7.4. Using solvent evaporation, m-THPC loaded nanoparticles were prepared with a high drug encapsulation efficiency (approximately 89%). Dynamic light scattering and transmission electron microscopy revealed the spherical shape and 132 nm diameter of the nanoparticles. The in vitro release rate of m-THPC at pH 5.0 was faster than at pH 7.0 (58% versus 10% m-THPC released within 48 h, respectively). The in vitro photodynamic therapy efficiency was tested with the HT-29 cell line. m-THPC loaded PEGMA-co-DPA nanoparticles exhibited obvious phototoxicity in HT-29 colon cancer cells after light irradiation. The results indicate that these pH sensitive nanoparticles are potential carriers for tumor targeting and photodynamic therapy.

Improvement of biodistribution and therapeutic index via increase of polyethylene glycol on drug-carrying liposomes in an HT-29/luc xenografted mouse model.

Liposomes modified with a high concentration of polyethylene glycol (PEG) could significantly prolong the retention time of the carried drug in the circulation, thus improving the drug accumulation in the tumor. In this study, 6 mol% rather than 0.9 mol% PEGylated liposomes (100 nm in diameter) encapsulated with indium-111 were used in a human colorectal carcinoma HT-29/luc tumor-bearing mouse model for comparing the PEGylation effect. Pharmacokinetics, biodistribution, passive-targeted assay, bioluminescence imaging (BLI) and tumor growth measurements were used for the spatial and temporal distribution, tumor localization and therapeutic evaluation of the drug. Pharmacokinetic studies indicated that the terminal half-life (T((1/2))lambdaz) and C(max) of 6 mol% PEG (111)In liposomes were similar to those of 0.9 mol% PEG (111)In liposomes. In the blood, the total body clearance (Cl) of 6 mol% PEG (111)In liposomes was about 1.7-fold lower and the area under the curve (AUC) was 1.7-fold higher than those of 0.9 mol% PEG (111)In liposomes. These results showed that the long-term circulation and localization of 6 mol% PEGylated liposomes was more appropriate for use in the tumor-bearing animal model. In addition, the biodistribution of 6 mol% PEG (111)In liposomes showed significantly lower uptake in the liver, spleen, kidneys, small intestine and bone marrow than those of 0.9 mol% PEG (111)In liposomes. The clearance rate of both drugs from the blood decreased with time, with the maximum at 24 h post intravenous (i.v.) injection. Prominent tumor uptake and the highest tumor/muscle ratios were found at 48 h post injection. Both AUC and relative ratio of the AUCs (RR-AUC) also showed that 6 mol% PEGylated liposomes significantly reduced the uptake of drugs in the reticuloendothelial system (RES), yet enhanced the uptake in the tumor. Gamma scintigraphy at 48 h post injection also demonstrated more distinct tumor uptake with 6 mol% PEG (111)In liposomes as compared to that of 0.9 mol% PEGylated liposomes (p<0.01). BLI and in vivo tumor growth tracing showed that growth in tumor volume could largely be inhibited by 6 mol% PEG (111)In liposomes. The results suggest that 6 mol% PEGylated liposomes might be a more suitable liposomal carrier for drug delivery than 0.9 mol% PEGylated liposomes, not only by reducing the drug accumulation in the RES or its related organs, but by prolonging drug circulation and eventually enhancing the targeting efficiency in the tumor to reach a better therapeutic index.

Therapeutic and scintigraphic applications of polymeric micelles: combination of chemotherapy and radiotherapy in hepatocellular carcinoma.

This study evaluated a multifunctional micelle simultaneously loaded with doxorubicin (Dox) and labeled with radionuclide rhenium-188 ((188)Re) as a combined radiotherapy and chemotherapy treatment for hepatocellular carcinoma. We investigated the single photon emission computed tomography, biodistribution, antitumor efficacy, and pathology of (188)Re-Dox micelles in a murine orthotopic luciferase-transfected BNL tumor cells hepatocellular carcinoma model. The single photon emission computed tomography and computed tomography images showed high radioactivity in the liver and tumor, which was in agreement with the biodistribution measured by γ-counting. In vivo bioluminescence images showed the smallest size tumor (P<0.05) in mice treated with the combined micelles throughout the experimental period. In addition, the combined (188)Re-Dox micelles group had significantly longer survival compared with the control, (188)ReO4 alone (P<0.005), and Dox micelles alone (P<0.01) groups. Pathohistological analysis revealed that tumors treated with (188)Re-Dox micelles had more necrotic features and decreased cell proliferation. Therefore, (188)Re-Dox micelles may enable combined radiotherapy and chemotherapy to maximize the effectiveness of treatment for hepatocellular carcinoma.

Preparation and therapeutic evaluation of (188)Re-thermogelling emulsion in rat model of hepatocellular carcinoma.

Radiolabeled Lipiodol(®) (Guerbet, Villepinte, France) is routinely used in hepatoma therapy. The temperature-sensitive hydrogel polyethylene glycol-b-poly-DL-lactic acid-co-glycolic acid-b-polyethylene glycol triblock copolymer is used as an embolic agent and sustained drug release system. This study attempted to combine the polyethylene glycol-b-poly-DL-lactic acid-co-glycolic acid-b-polyethylene glycol hydrogel and radio-labeled Lipiodol to form a new radio-thermogelling emulsion, rhenium-188-N,N'-1,2-ethanediylbis-L-cysteine diethyl-ester dihydrochloride-Lipiodol/hydrogel ((188)Re-ELH). The therapeutic potential of (188)Re-ELH was evaluated in a rodent hepatoma model. Rhenium-188 chelated with N,N'-1,2-ethanediylbis-L-cysteine diethyl-ester dihydrochloride was extracted with Lipiodol to obtain rhenium-188-N,N'-1,2-ethanediylbis-L-cysteine diethyl-ester dihydrochloride-Lipiodol ((188)Re-EL), which was blended with the hydrogel in equal volumes to develop (188)Re-ELH. The (188)Re-ELH phase stability was evaluated at different temperatures. Biodistribution patterns and micro-single-photon emission computed tomography/computed tomography images in Sprague Dawley rats implanted with the rat hepatoma cell line N1-S1 were observed after in situ tumoral injection of ~3.7 MBq (188)Re-ELH. The therapeutic potential of (188)Re-EL (48.58±3.86 MBq/0.1 mL, n=12) was evaluated in a 2-month survival study using the same animal model. The therapeutic effects of (188)Re-ELH (25.52±4.64 MBq/0.1 mL, n=12) were evaluated and compared with those of (188)Re-EL. The responses were assessed by changes in tumor size and survival rates. The (188)Re-ELH emulsion was stable in the gel form at 25°C-35°C for >52 hours. Biodistribution data and micro-single-photon emission computed tomography/computed tomography images of the (188)Re-ELH group indicated that most activity was selectively observed in hepatomas. Long-term (188)Re-ELH studies have demonstrated protracted reductions in tumor volumes and positive effects on the survival rates (75%) of N1-S1 hepatoma-bearing rats. Conversely, the 2-month survival rate was 13% in the control sham group. Therapeutic responses differed significantly between the two groups (P<0.005). Thus, the hydrogel enhanced the injection stability of (188)Re-EL in an animal hepatoma model. Given the synergistic results, direct (188)Re-ELH intratumoral injection is a potential therapeutic alternative for hepatoma treatment.

Monitoring tumor response with [18F]FMAU in a sarcoma-bearing mouse model after liposomal vinorelbine treatment.

OBJECTIVE: Previous studies have shown that the accumulation level of FMAU in tumor is proportional to its proliferation rate. This study demonstrated that 2'-deoxy-2'-[(18)F]fluoro-ß-d-arabinofuranosyluracil ([(18)F]FMAU) is a promising PET probe for noninvasively monitoring the therapeutic efficacy of 6% PEGylated liposomal vinorelbine (lipo-VNB) in a subcutaneous murine NG4TL4 sarcoma mouse model. METHODS: Female syngenic FVB/N mice were inoculated with NG4TL4 cells in the right flank. After tumor size reached 150 ± 50 mm(3) (day 0), lipo-VNB (5mg/kg) was intravenously administered on days 0, 3 and 6. To monitor the therapeutic efficacy of lipo-VNB, [(18)F]FMAU PET was employed to evaluate the proliferation rate of tumor, and it was compared with that observed from [(18)F]FDG/[(18)F]fluoroacetate PET. The expression of proliferating cell nuclear antigen (PCNA) in tumor during treatment was determined by semiquantitative analysis of immunohistochemical staining. RESULTS: A significant inhibition (p<0.001) in tumor growth was observed on day 3 after a single dose treatment. The tumor-to-muscle ratio (T/M) derived from [(18)F]FMAU-PET images of lipo-VNB-treated group declined from 2.33 ± 0.16 to 1.26 ± 0.03 after three doses of treatment, while that of the control remained steady. The retarded proliferation rate of lipo-VNB-treated sarcoma was confirmed by PCNA immunohistochemistry staining. However, both [(18)F]FDG and [(18)F]fluoroacetate microPET imaging did not show significant difference in T/M between the therapeutic and the control groups throughout the entire experimental period. CONCLUSION: Lipo-VNB can effectively impede the growth of NG4TL4 sarcoma. [(18)F]FMAU PET is an appropriate modality for early monitoring of the tumor response during the treatment course of lipo-VNB.

Tumor burden talks in cancer treatment with PEGylated liposomal drugs.

PURPOSE: PEGylated liposomes are important drug carriers that can passively target tumor by enhanced permeability and retention (EPR) effect in neoplasm lesions. This study demonstrated that tumor burden determines the tumor uptake, and also the tumor response, in cancer treatment with PEGylated liposomal drugs in a C26/tk-luc colon carcinoma-bearing mouse model. METHODS: Empty PEGylated liposomes (NanoX) and those encapsulated with VNB (NanoVNB) were labeled with In-111 to obtain InNanoX and InVNBL in high labeling yield and radiochemical purity (all >90%). BALB/c mice bearing either small (58.4±8.0 mm(3)) or large (102.4±22.0 mm(3)) C26/tk-luc tumors in the right dorsal flank were intravenously administered with NanoVNB, InNanoX, InVNBL, or NanoX as a control, every 7 days for 3 times. The therapeutic efficacy was evaluated by body weight loss, tumor growth inhibition (using calipers and bioluminescence imaging) and survival fraction. The scintigraphic imaging of tumor mouse was performed during and after treatment. RESULTS: The biodistribution study of InVNBL revealed a clear inverse correlation (r (2) = 0.9336) between the tumor uptake and the tumor mass ranged from 27.6 to 623.9 mg. All three liposomal drugs showed better therapeutic efficacy in small-tumor mice than in large-tumor mice. Tumor-bearing mice treated with InVNBL (a combination drug) showed the highest tumor growth inhibition rate and survival fraction compared to those treated with NanoVNB (chemodrug only) and InNanoX (radionuclide only). Specific tumor targeting and significantly increased tumor uptake after periodical treatment with InVNBL were evidenced by scintigraphic imaging, especially in mice bearing small tumors. CONCLUSION: The significant differences in the outcomes of cancer treatment and molecular imaging between animals bearing small and large tumors revealed that tumor burden is a critical and discriminative factor in cancer therapy using PEGylated liposomal drugs.

Monitoring tumor response with radiolabeled nucleoside analogs in a hepatoma-bearing mouse model early after doxisome(®) treatment.

PURPOSE: This study aims to demonstrate that 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) positron emission tomography (PET) is a promising modality for noninvasively monitoring the therapeutic efficacy of Doxisome(®) in a subcutaneous hepatoma mouse model. PROCEDURES: Male BALB/c nu/nu mice were inoculated with HepG2 hepatoma xenograft in the right flank. Doxisome(®) (5 mg/kg, three times a week for 2 weeks) was intravenously administrated for treatment. (18)F-FLT-microPET, biodistribution studies, and immunohistochemistry of Ki-67 were performed. RESULTS: A significant difference (p < 0.05) in tumor volume was observed on day 5 between treated and control groups. The tumor-to-muscle ratio derived from (18)F-FLT-PET and (123)I-ICdR-microSPECT images of Doxisome(®)-treated mice dropped from 12.55 ± 0.76 to 3.81 ± 0.31 and from 2.48 ± 0.42 to 1.59 ± 0.08 after a three-dose treatment, respectively, while that of the control group remained steady. The retarded proliferation rate of treated xenograft was confirmed by Ki-67 immunohistochemistry staining. CONCLUSIONS: This study clearly demonstrated that Doxisome(®) is an effective anti-cancer drug against the growth of HepG2 hepatoma and that (18)F-FLT-PET could provide early information of tumor response during treatment.

Development and validation of an anion-exchange HPLC method for the determination of fluoride content and radiochemical purity in [18F]NaF.

(18)F-labeled sodium fluoride ([(18)F]NaF) is a useful bone imaging agent that has been demonstrated to be significantly more accurate than (99m)Tc-labeled methylene diphosphonate for the detection of both sclerotic and lytic lesions in various malignancies. A reliable anion-exchange HPLC method equipped with suppressed conductivity and radioactive detectors has been developed in order to analyze the content of NaF and radiochemical purity in [(18)F]NaF radiopharmaceuticals. The method described for fluoride analysis uses an isocratic elution of NaF in a Hamilton anion-exchange column using a mobile phase that consists of 7.5 mM sodium carbonate and 0.018 mM potassium thiocyanate. The flow rate was 1.0 ml/min. The method was validated in accordance with several parameters, including system suitability, specificity, precision, accuracy, linearity, robustness, limit of detection and limit of quantification. The results are described as follows: (1) The system suitability includes the tailing factor, theoretical plate number and resolution, which are 1.192534, 2729.6594 and 16.7415, respectively. (2) For specificity, the solvent peak and chloride ion did not interfere with the retention time of the fluoride. (3) The percentage coefficient of variation for analysis of precision, including repeatability and intermediate precision, is less than 2.0%. (4) Accuracy of method is within the range of 98%-102%. (5) The range of linearity is from 10 to 400 µg/ml, with the correlation coefficient (R(2)) always being above 0.9985. (6) The data of method robustness are within acceptance criteria. (7) The limit of detection and limit of quantification are 0.0678 and 0.20 µg/ml, respectively. All of the analysis results demonstrate that this method is highly sensitive, convenient, specific and suitable for quantification of NaF over a wide linear range. Therefore, the method can be successfully performed for routine analysis of fluoride content in [(18)F]NaF radiopharmaceuticals and reduce the time required for analysis.

Pharmacokinetics and dosimetry of (111)In/(188)Re-labeled PEGylated liposomal drugs in two colon carcinoma-bearing mouse models.

PEGylated liposomes are important drug carriers for nanomedicine cancer therapy. PEGylated liposomes can encapsulate radio- and chemo-drugs and passively target tumor sites via enhanced permeability and retention effect. This study estimated the pharmacokinetics and dosimetry after administration of radio-chemotherapeutics ((111)In-labeled vinorelbine [VNB]-encapsulated liposomes, InVNBL, and (188)Re-labeled doxorubicin [DXR]-encapsulated liposomes, ReDXRL) for radionuclide therapy in two colon carcinoma-bearing mouse models. A C26 colon carcinoma tumor/ascites mouse model and a subcutaneous solid tumor-bearing mouse model were employed. Biodistribution studies of InVNBL and ReDXRL after intraperitoneal administration in tumor/ascites-bearing mice (protocol A) and intravenous administration in subcutaneous solid tumor-bearing mice (protocol B) were performed. The radiation dose to normal tissues and tumors were calculated based on the results of distribution studies in mice, using the OLINDA/EXM program. The cumulated activities in most organs after administration of InVNBL in either the tumor/ascites-bearing mice (protocol A) or the subcutaneous solid tumor-bearing mice (protocol B) were higher than those of ReDXRL. Higher tumor-to-normal-tissues absorption dose ratios (T/NTs) were observed after administration of InVNBL than those of ReDXRL for protocol A. The T/NTs for the liver, spleen, and red marrow after injection of InVNBL for protocol B were similar to those of ReDXRL. The critical organ was found to be red marrow, and thus the red marrow absorption dose defined the recommended maximum administration activity of these liposomal drugs. Characterization of pharmacokinetics and dosimetry is needed to select the appropriate radiotherapeutics for specific tumor treatment applications. The results suggest that InVNBL is a promising therapeutic agent, which is as good as ReDXRL, in two mouse tumor models.

Evaluation of pharmacokinetics of 111In-labeled VNB-PEGylated liposomes after intraperitoneal and intravenous administration in a tumor/ascites mouse model.

Nanoliposomes are important drug carriers that can passively target tumor sites by the enhanced permeability and retention (EPR) effect in neoplasm lesions. This study evaluated the biodistribution and pharmacokinetics of 111In-labeled vinorelbine (VNB)-encapsulated PEGylated liposomes (IVNBPL) after intraperitoneal (i.p.) and intravenous (i.v.) administration in a C26/tk-luc colon carcinoma ascites mouse model. IVNBPL was prepared by labeling VNB-encapsulated PEGylated liposomes with 111In-oxine. BALB/c mice were i.p. inoculated with 2 x 10(5) C26/tk-luc cells in 500 muL of phosphate-buffered saline. Peritoneal tumor lesions were confirmed by 124I-FIAU/micro-PET (positron emission tomography) and bioluminescence imaging. Ascites production was examined by ultrasound imaging on day 10 after tumor cell inoculation. The pharmacokinetics and biodistribution studies of IVNBPL in a tumor/ascites mouse model were conducted. The labeling efficiency was more than 90%. The in vitro stability in human plasma at 37 degrees C for 72 hours was 83% +/- 3.5%. For i.p. administration, the areas under curves (AUCs) of ascites and tumor were 6.78- and 1.70-fold higher, whereas the AUCs of normal tissues were lower than those via the i.v. route. This study demonstrates that i.p. administration is a better approach than i.v. injection for IVNBPL, when applied to the treatment of i.p. malignant disease in a tumor/ascites mouse model.

Therapeutic efficacy evaluation of 111In-labeled PEGylated liposomal vinorelbine in murine colon carcinoma with multimodalities of molecular imaging.

UNLABELLED: In our previous studies using combined radioisotopes with chemotherapeutic liposomal drugs (i.e., (111)In-labeled polyethylene glycol (PEG)ylated liposomal vinorelbine) we have reported possible therapeutic efficiency in tumor growth suppression. Nevertheless, the challenge remains as to whether this chemotherapy has a therapeutic effect as good as that of combination therapy. The goal of this study was to investigate the real therapeutic effectiveness of 6 mol% PEG (111)In-vinorelbine liposomes via the elevation of the radiation dosage and reduction in the concentration of chemotherapeutic agents. METHODS: Murine colon carcinoma cells transfected with dual-reporter genes (CT-26/tk-luc) were xenografted into BALB/c mice. The biodistribution was estimated to determine the drug profile and targeting efficiency of (111)In-vinorelbine liposomes. Bioluminescence imaging and (18)F-FDG small-animal PET were applied to monitor the therapeutic response after drug administration. The survival in vivo was estimated and linked with the toxicologic and histopathologic analyses to determine the preclinical safety and feasibility of the nanomedicine. RESULTS: Effective long-term circulation of radioactivity in the plasma was achieved by 6 mol% PEG (111)In-vinorelbine liposomes, and this dose showed significantly lower uptake in the reticuloendothelial system than that of 0.9 mol% PEG (111)In-vinorelbine liposomes. Selective tumor uptake was represented by cumulative deposition, and the maximum accumulation was at 48 h after injection. The combination therapy exhibited an additive effect for tumor growth suppression as tracked by caliper measurement, bioluminescence imaging, and small-animal PET. Furthermore, an improved survival rate and reduced tissue toxicity were closely correlated with the toxicologic and histopathologic results. CONCLUSION: The results demonstrated that the use of 6 mol% PEG (111)In-vinorelbine liposomes for passively targeted tumor therapy displayed an additive effect with combined therapy, not only by prolonging the circulation rate because of a reduction in the phagocytic effect of the reticuloendothelial system but also by enhancing tumor uptake. Thus, this preclinical study suggests that 6 mol% PEG (111)In-vinorelbine liposomes have the potential to increase the therapeutic index and reduce the toxicity of the passively nanotargeted chemoradiotherapies.