Antitumor Effect of Adriamycin-Encapsulated Nanoparticles of Poly(DL-lactide-co-glycolide)-Grafted Dextran KI-CHOON CHOI,1 JE-YONG BANG,2 CHAN KIM,3 PYOUNG-IL KIM,4 SANG-RAK LEE,5 WAN-TAE CHUNG,6 WOO-DAE PARK,1 JUNG-SUN PARK,7 YEON SOO LEE,8 CHAE-EUN SONG,9 HYE-YOUNG LEE10 1
Department of Pet Science, Seojeong College, Gyeonggi-do 482-777, South Korea
2
Faculty of Environment and Life Sciences, Seoul Women’s University, Seoul 139-774, South Korea
3
AMOMEDI Co., Ltd, 597-2 Wonsanri, Hasungmyun, Gimpo, Gyeonggi-do, South Korea
4
School of Chemical and Biological Engineering, Seoul National University, Seoul 151-742, South Korea
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Department of Animal Science and Environment, Konkuk University, Seoul 143-701, South Korea
6
Nutrition Physiology Division, Department of Livestock Biotechnology & Environment, National Livestock Research Institute, Rural Development Administration, Suwon 441-706, South Korea 7
Department of Hematology-Oncology, Chonnam National University Medical School, Gwangju, South Korea
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School of Information and Mechatronics, GwangJu Institute of Science and Technology, Gwangju 500-712, South Korea
9
Korea Institute of Natural Science Inc., Naju, Jeonnam 520-330, South Korea
10
Department of Beauty Arts, Seokyeong University, Seoul 136-704, South Korea
Received 17 March 2008; revised 29 July 2008; accepted 26 August 2008 Published online 29 September 2008 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jps.21588
ABSTRACT: In this study, we prepared adriamycin (ADR)-encapsulated core–shell type nanoparticles of a poly(DL-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer and evaluated its antitumor activity in vitro and in vivo. The particle size of ADR-encapsulated DexLG nanoparticles was around 50–200 nm and the morphology was spherical shapes at transmission electron microscopy (TEM) observation. Since reconstitution of lyophilized nanoparticles is essential to practical use in vivo, ADR-encapsulated DexLG nanoparticles were lyophilized and reconstituted them into deionized water. Although reconstitution process caused increase of particle size, drug release behavior of nanoparticles was not significantly changed before and after reconstitution process. The ADR-encapsulated DexLG nanoparticles were less cytotoxic than free ADR plus empty nanoparticles at in vitro, while empty DexLG nanoparticles did not significantly affect cell viability. Even if free ADR plus empty nanoparticles are most effective to inhibit tumor growth at tumor-induced animal model using CT-26 cells, ADR-encapsulated DexLG nanoparticles showed increased survivability of mice. These results indicated that ADR-encapsulated DexLG nanoparticles are promising vehicles for antitumor drug delivery. ß 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2104–2112, 2009
Keywords: adriamycin; dextran; core–shell type nanoparticles; poly(DL-lactide-coglycolide); CT-26 colorectal tumor
Correspondence to: Chae-Eun Song (Telephone: þ82-62522-3184; Fax: þ82-62-522-3184; E-mail:
[email protected]) Journal of Pharmaceutical Sciences, Vol. 98, 2104–2112 (2009) ß 2008 Wiley-Liss, Inc. and the American Pharmacists Association
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INTRODUCTION Nanoparticle-based drug delivery system has been extensively investigated due to their potential of
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drug targeting to wanted site of action.1 Since nanoparticles have small sizes below 1000 nm, they can be primarily considered as a device for parenteral injection.2 Nanoparticles have various advantages such as site-specific drug delivery via active or passive targeting mechanism, reduction in the amount of drug administered, minimizing of irritation at injection site, and minimizing side effects. For parenteral injection of drug, various carriers have been developed such as liposomes,3 polymeric micelles,4,5 and core–shell type nanoparticles,6,7 have been reported. Especially, polymeric micelles,4,8 core–shell type nanoparticles,6,7 and hydrophobized polysaccharides9 have received great attention due to their self-assembling characteristics in aqueous environment. Selfassembled nanocarriers are generally characterized of a hydrophobic core and a hydrophilic shell, that is, hydrophobic core acts as a drug incorporation part and outer-shell acts as a safeguard from the attack of reticuloendothelial system. Therefore, they are considered as a superior drug carriers and developed by several researchers.4–11 Dextran is a polysaccharide consisting of glucose molecules, mainly through the 1,6- and partly through the 1,3-glucosidic linkages. Dextrans are characterized to a colloidal, hydrophilic and water solubility. Since dextrans are inert in biological systems and do not affect cell viability, it has been extensively used as a drug carrier system, including for antidiabetics, antibiotics, anticancer drugs, peptides and enzymes.9,12–15 Previously, we reported that DexLG copolymer can form self-assembling nanoparticles as a ADRcarrying vehicles.10 Dextran part in DexLG copolymer would form the hydrophilic outer-shell, due to its aqueous solubility, while PLGA has formed the inner core of the self-assembly, due to its hydrophobic properties. In this study, we have evaluated the antitumor effect of ADR-encapsulated DexLG nanoparticles using CT-26 colon carcinoma cells in vitro and in vivo.
EXPERIMENTAL Materials Dextran from Leuconostoc mesenteroides (average molecular weights (MW): 77,000), triethylamine (TEA), adriamycin (ADR), and thiazolyl blue tetrazolium bromide (MTT) were purchased from Sigma Chem. Co. (St. Louis, MO). N,N0 -dicyclohexyl carbodiimide (DCC) and 4-(N,N-dimethylamino)DOI 10.1002/jps
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pyridine (DMAP) were purchased from Aldrich Chemical Co. (Milwaukee, WI). Poly(DL-lactide-coglycolide) (PLGA 5005, MW: 5100) was purchased from Wako Pure Chem Co. (Osaka, Japan). The dialysis membranes with a molecular weight cutoff (MWCO) of 8000 g/mol were purchased from Spectra/PorTM Membrane (Spectrum Lab. Inc., Rancho Dominguez, CA). Dichloromethane (DCM) and dimethyl sulfoxide (DMSO) were of HPLC grade and used without further purification. DexLG copolymer was synthesized as reported previously.10 Briefly, Dextran and PLGA were dissolved separately in anhydrous DMSO. 1.5 equivalent amount of DCC in DMSO solution were added to the PLGA/DMSO solution, which was then stirred for 30 min to activate the carboxyl group of the PLGA. The resulting solution was added to the Dextran/DMSO solution containing DMAP, and the reaction was allowed to continue at room temperature for 12 h. The reaction mixture was filtered off to remove the byproducts and then exhaustively dialyzed against deionized water for 3 days. Following this, dialyzed solution was lyophilized for 3 days and then solid product was precipitated three times in DCM to remove unreacted PLGA and dried in a vacuum oven for 2 days. After that, the dried product was dispersed in distilled water to remove unreacted dextran, with this procedure being repeated three times following lyophilized it. The molecular weight (MW) of DexLG copolymer was calculated from elemental analysis as described previously.10 The degree of substitution (DS) of PLGA chains grafted per dextran was estimated by subtracting the determined MW of dextran from the MW of DexLG graft copolymers and dividing by MW of PLGA.10
Preparation of Core–Shell Type Nanoparticles of DexLG Copolymer The DexLG nanoparticles were prepared as reported previously with slight modification.10 ADR was dissolved in 1 mL of DMSO with two equivalent molar ratio of TEA. This solution was mixed with 45 mg of DexLG copolymer in 4 mL of DMSO and stirred for 3 h. This solution was slowly dropped into 20 mL of deionized water for 10 min and then stirred 5 min additionally. This solution was introduced into dialysis tube (MWCO 8000 g/mol) and dialyzed against deionized water for 24 h. The deionized water was exchanged JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 6, JUNE 2009
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intervals of 1 h for 3 h and then exchanged 3 h intervals for 21 h. The dialyzed solution was filtered to remove aggregates and precipitants. After that, they were lyophilized or analyzed. Empty nanoparticles of DexLG copolymer were prepared by same procedure described above with the exception of ADR. For evaluation of drug contents and loading efficiency, 5 mg of ADR-encapsulated DexLG nanoparticles were dissolved in 10 mL of DMSO and diluted it with DMSO. ADR concentration was evaluated using an UV-spectrophotometer (UV spectrophotometer 1201, Shimadzu Co., Kyoto, Japan) at 488 nm. Empty nanoparticles of DexLG were used as a blank test. Drug contents ¼ ½ðdrug weight in the nanoparticlesÞ= ðweight of nanoparticlesÞ 100 Loading efficiency ¼ ½ðResidual drug in the nanoparticleÞ= ðinitial feeding amount of drugÞ 100
Reconstitution Study of ADR-Encapsulated DexLG Nanoparticles Volume of dialyzed nanoparticle solution above mentioned was adjusted to 40 mL, that is, 1 mg DexLG copolymer/mL water. Five milliliters of this solution (i.e., 5 mg polymer/5 mL water) was lyophilized for 3 days to test reconstitution of nanoparticles. One milliliter of deionized water was added to a lyophilized solid. This solution was stirred gently for 10 min and diluted it 10 times for analysis of particle size.
Analysis The morphology of the polymeric nanoparticles was observed using a transmission electron microscope (TEM, JEOL JEM-2000 FX II, Tokyo, Japan). A drop of nanoparticle suspension containing phosphotungstic acid (0.05% (w/w)) was placed onto a carbon film coated on a copper grid for TEM. Observation was done at 80 kV. Particle size of nanoparticles was measured with a dynamic laser scattering spectrophotometer (DLS-7000, Otsuka Electronics Co., Osaka, Japan). A sample solution prepared by dialysis method was used for particle size measurement (concentration: 0.1 wt.-%). JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 6, JUNE 2009
Drug Release Study The release experiment was carried out in vitro as follows: dialyzed solution above mentioned adjusted a volume to 40 mL with deionized water (i.e., 1 mg polymer/mL water). Five milliliters of this solution introduced into dialysis tube (MWCO: 12,000 g/mol) were placed in 200 mL bottle with 195 mL of PBS, and the media stirred at 100 rpm and 3708C. At specific time intervals, the medium was taken for analysis of drug concentration. After that whole media was replaced with fresh PBS to prevent drug saturation. The concentration of the ADR released into PBS was determined using an UV-spectrophotometer (UV spectrophotometer 1201, Shimadzu Co.) at 488 nm. For comparison with reconstituted nanoparticles, reconstituted nanoparticle solution above mentioned was adapted to this release experiment, that is, 5 mL of reconstituted nanoparticle solution was introduced into dialysis tube and then release test was performed same procedure. In Vitro Cell Cytotoxicity CT-26 (colon carcinoma cell line) maintained in DMEM (10% fetal bovine serum, 5% CO2 at 378C) was used to evaluate the cytotoxicity of nanoparticles by MTT cell proliferation assay. Cells were seeded at a density of 5 103 per well in 96-well plates with 100 mL medium before addition of nanoparticles. After that, ADR, ADR-encapsulated DexLG nanoparticles, and empty DexLG nanoparticles were added into 96-well plates at volume of 100 mL. After 1 and 2 days of incubation, 30 mL of MTT (5 mg/mL) was added to 96-well plates and then incubated for 4 h. The formazan crystals were then solubilized with DMSO and the absorbance (560 nm-test/630 nm-reference) was determined using an automated computer-linked microplate reader (Molecular Device, Co., Sunnyvale, CA). Each measurement of the drug concentration was obtained as the mean value of eight wells. The amount of formazan present is proportional to the number of viable cells, as only living cells will reduce MTT to blue formazan. The results were expressed as a percentage of the absorbance present in the drug-treated cells compared to that in the control cells.
In Vivo CT-26 Tumor Model Animal experiment was performed according to the Animal Experiment Guidance of Seojeong DOI 10.1002/jps
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College. Antitumor activity against solid tumors was evaluated with CT-26 murine tumor cells. CT-26 murine tumor cells (1 105 cells) were inoculated s.c. into the backs of mice (BALB/c mice, 5 weeks old, average bodyweight was 20 g). When tumors were reached to approximately 3 mm 3 mm (approximately 10 days after), the animals were divided into treatment and control groups. Each group consisted of 10 tumor-bearing mice that were ear-tagged and followed-up individually throughout the study. The intravenous administration of drugs or vehicle began on day 10 and first drug injection was determined to beginning of the test, that is, day 0. Each drug was administered at a volume of 0.1 mL/10 g of mice for four times for 16 days at a intervals of 4 days. The control group was received the PBS (pH 7.4, 0.1 M). The mortality was monitored daily and tumor growth was measured at 2- or 3-day intervals by caliper measurement. Tumor volume was calculated using the following formula: Tumor volume (mm3) ¼ (Length width2)/2.
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domain, that is, PLGA act as a drug incorporation site with biodegradability and dextran main chain act as a hydrophilic outer-shell of the nanoparticles. The composition and molecular weight of DexLG copolymer was summarized in Table 1. The core–shell type nanoparticles of DexLG copolymer were prepared by nanoprecipitationdialysis method. First of all, nanoparticles were formed by nanoprecipitation, that is, organic solvent containing polymer plus drug was slowly dropped into aqueous solution and then nanoparticles were formed instantly. Since DMSO has high boiling temperature and is difficult to remove it by rotary-evaporation, dialysis procedure was employed to remove organic solvent. Even if direct dialysis procedure10,17 is more simple and efficient method to make nanoparticles, nanoprecipitation was better to reduce particle size of nanoparticles. At this moment, the reason of reduced particle size at nanoprecipitation method is not clear. At nanoprecipitation process, organic solvent is immediately mixed with water and then nanoparticles are instantly formed. Otherwise, at direct dialysis process, water must be slowly entered the dialysis membrane and then slowly mixed with organic solvent. Therefore, nanoparticles must be formed slowly at direct dialysis procedure. It is suggested that these diffusion of solvent into aqueous phase is one of the reason of particle size changes. As shown in Table 1, particle size of DexLG nanoparticles was increased according to the increase of PLGA content in the copolymer. Figure 1 shows TEM images of DexLG nanoparticles. As shown in Figure 1, all of the DexLG copolymer are able to form spherical nanoparticles in the aqueous solution and their particle size was almost similar to the particle size measurements. We choose ADR as an anticancer agent and encapsulated into core–shell type nanoparticles of
RESULTS AND DISCUSSION Characterization of Core–Shell Type Nanoparticles of DexLG Copolymer In a previous work,10 we reported that DexLG copolymer were synthesized by conjugation of PLGA to dextran and it can formed core–shell type nanoparticles via self-assembling process. Dextran is extensively investigated as a biomaterials and antitumor drug delivery carriers due to their water solubility, prolong the half-lives of antitumor drug, biocompatibility, immunoneutrality, and passive targeting to tumor.12,13 For these kinds of application, dextran is required to be modified hydrophobic.10,16,17 We rendered dextran using PLGA copolymer as a hydrophobic Table 1. Characterization of PLGA-g-Dextran Copolymer
Particle Size (nm)
Dextran DexLG-1 DexLG-2 DexLG-3 PLGA
M na
DSb
Intensity Ave.
Weight Ave.
Number Ave.
77,000 85,700 96,400 108,600 5100
— 1.7 3.8 6.2 —
91 31 110 29 141 36
— 72 13 103 21 130 29 —
56 28 92 19 120 32
a
Number-average molecular weight (Mn) of DexLG was calculated from elemental analysis. The degree of substitution (DS) of PLGA chains grafted per dextran was estimated by subtracting the determined MW of dextran from the MW of DexLG graft copolymers and dividing by MW of PLGA. b
DOI 10.1002/jps
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Figure 1. TEM photographs of empty nanoparticles of DexLG-1 (a), DexLG-2 (b), and DexLG-3 (c).
DexLG copolymer. The drug contents and loading efficiency was shown in Table 2. As shown in Table 2, drug contents and loading efficiency were increased according to the PLGA content in the copolymer composition. When initial drug feeding amount was increased, drug contents was increased but loading efficiency was decreased. Particle size was increased according to the increase of drug contents and PLGA contents in the copolymer composition. These results showed that DexLG can form nanoparticles about 50– 200 nm in their particle size. Small particle size less than 200 nm is more desirable for long blood circulation of drug and then passive drug targeting.1 Most of ADR-encapsulated nanoparticles has sub-200 nm sizes except for the case of DexLG-3. Generally, drug-encapsulated nanoparticles is required to store as a lyophilized solid form rather than aqueous solution because of drug can liberated from nanoparticles in the aqueous
environment. Resultantly, lyophilized solid form of drug-encapsulated nanoparticle formulation is favorable for long-term storage. Therefore, lyophilized nanoparticle formulation must be reconstituted into aqueous solution before administration into human. Their reconstitution factor is one of the most important factors in the whole process of nanoparticle formulation preparation and application.18–20 Normally, nanoparticles can be aggregated significantly by reconstitution process without use of cryoprotectants. For reconstitution of nanoparticles into aqueous solution, cryoprotectants such as glucose, lactose, trehalose, manitol, and so on is required to avoid aggregation or precipitation of nanoparticles.18–20 Figure 2 shows the particle size distribution of reconstituted ADR-encapsulated DexLG-2 nanoparticles. As shown in Figure 2, particle size of ADR-encapsulated nanoparticles before lyophilization was 104 23 nm by weight average. Size of
Table 2. Characterization of Reconstitution of ADR-Encapsulated DexLG Nanoparticles Polymer/Drug Weight Ratio (mg/mg) Before lyophilization DexLG-1 45/5 DexLG-2 45/5 40/10 DexLG-3 45/5 After lyophilization DexLG-1 45/5 DexLG-2 45/5 40/10 DexLG-3 45/5
Particle Size (nm)
Drug Contents (%, w/w)
Loading Efficiency (%, w/w)
Intensity Ave.
Weight Ave.
Number Ave.
3.2 3.8 6.2 4.1
29.8 35.6 26.4 38.5
110 21 121 29 165 88 203 62
97 18 104 23 137 47 191 53
89 14 93 17 118 39 168 35
3.1 3.8 6.1 4.0
— — — —
107 36 146 63 205 80 278 71
98 28 135 82 172 44 221 67
91 28 112 30 167 43 196 46
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Figure 2. Changes of particle size distribution before and after reconstitution of ADR-encapsulated DexLG-2 nanoparticles (polymer/drug weight ratio ¼ 45/5). For reconstitution of nanoparticles, ADR-encapsulated DexLG nanoparticles were lyophilized and reconstituted it in the deionized water. Five micrograms of nanoparticle was reconstituted in the 1 mL of deionized water for 10 min by gentle magnetic stirring and diluted it with deionized water for analysis of particle size.
reconstituted nanoparticles (DexLG-2, 45/5) was slightly increased and its size distribution was slightly widened. It suggested that ADRencapsulated DexLG nanoparticles were slightly increased during the lyophilization/reconstitution process. At all of the cases, precipitation of nanoparticles did not occur during the reconstitution process although particle size was slightly increased as shown in Table 2. Drug contents were not significantly changed before and after reconstitution process. We suggested that plenty of hydroxyl group must be exposed on the nanoparticle surfaces due to their core–shell structure10 and abundance of hydrophilic moiety on the nanoparticle surfaces might be the reason of superior reconstitution factor of this nanoparticles without aid of cryoprotectants. Figures 3 and 4 show the effect of reconstitution process on the drug release behavior in vitro. Figure 3 shows changes of ADR release rate from DexLG nanoparticles before and after reconstitution against copolymer composition. As shown in Figure 3, before reconstitution of nanoparticles, ADR was released rapidly for 1 day and then sustained released for several days. After reconstitution of nanoparticles, changes of ADR release rate from DexLG nanoparticles was not significantly different even if release rate of drug after DOI 10.1002/jps
Figure 3. The effect of copolymer composition on the ADR release from DexLG nanoparticles before and after reconstitution. DexLG-1 (a), DexLG-2 (b), and DexLG-3 (c) nanoparticles. Just after dialysis procedure, ADRencapsulated DexLG nanoparticles solution was adapted to the drug release experiment for before reconstitution. After reconstitution of nanoparticles, release experiment was performed after reconstituted it.
reconstitution was slightly decreased. It suggested that increased particle size after reconstitution might be the cause of decreased release rate of ADR. Figure 4 shows the effect of reconstitution process on the drug release behavior against drug contents in vitro. As shown in JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 6, JUNE 2009
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against CT-26 colon carcinoma cells. Figure 5 shows the cytotoxicity of ADR-encapsulated DexLG nanoparticles with comparison of free ADR against CT-26 cells in vitro. To compare free ADR and nanoparticles at same condition, free ADR plus empty DexLG nanoparticles were treated to CT-26 cells with an equivalent concentration of ADR-encapsulated nanoparticles. As
Figure 4. The effect of drug contents on the ADR release from DexLG nanoparticles before and after reconstitution. ADR-encapsulated DexLG nanoparticles with 3.8% (w/w) (a) and 6.2% (w/w) (b).
Figure 4, the variations of drug contents itself was not obviously affected from the reconstitution process and drug release also slightly decreased after reconstitution process. Resultantly, lyophilized ADR-encapsulated DexLG nanoparticles can successfully reconstituted into aqueous solution. Reconstitution process did not significantly affected the characteristics and drug release behavior of ADR-encapsulated DexLG nanoparticles, indicating that nanoparticles between before and after reconstitution maintain their peculiar properties.
Antitumor Effect of ADR-Encapsulated DexLG Nanoparticles To study the antitumor activity of ADR-encapsulated DexLG nanoparticles, cytotoxicity of free ADR, ADR-encapsulated DexLG nanoparticles, and empty DexLG nanoparticles were tested JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 6, JUNE 2009
Figure 5. Cytotoxicity of ADR-encapsulated DexLG nanoparticles against CT-26 tumor cells. Cells were exposed to free ADR þ empty nanoparticles (weight ratio of ADR/empty nanoparticles was 1/9.) and ADRencapsulated DexLG nanoparticles for 1 (a) and 2 days (b). For comparison, empty nanoparticles alone were treated for 1 and 2 days (c). DOI 10.1002/jps
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shown in Figure 5, free ADR showed inherent cytotoxicity against CT-26 cells as a dose-dependent manner. ADR-encapsulated DexLG nanoparticles was less cytotoxic than free ADR plus empty nanoparticles. These results indicated that sustained release properties of ADR-encapsulated DexLG nanoparticles must be the lower cytotoxicity of nanoparticles compared to free ADR plus empty nanoparticles. As shown in Figure 5, the differences between free ADR plus empty nanoparticle and ADR-encapsulated DexLG nanoparticles were slightly decreased at 2 days of treatment. In other words, empty nanoparticle itself did not significantly inhibit the growth of tumor cell as shown in Figure 5. More than 90% of tumor cells were survived at 1000 mg/mL. To investigate the potential of in vivo antitumor activity, CT-26 colon carcinoma cells were injected subcutaneously (s.c.) in the back of mice as a tumor-induced animal model. Approximately 10 days of tumor implantation into back of the mice, tumor xenografts were well induced and incidence of tumor approximately 3–5 mm in diameter was observed. Mice were divided three groups, that is, PBS for control group, free ADR plus empty nanoparticle, and ADR-encapsulated DexLG nanoparticles. As shown in Figure 6,
Figure 6. Survival ratio of ADR or nanoparticle treated mice. Drug or ADR-encapsulated DexLG nanoparticles were administered at day 15 for 16 days at intervals of 4 days. Eight mouse were used for each group. PBS was injected for control group. Dose of ADR was 10 mg ADR/kg mouse. For comparison, free ADR was mixed with empty DexLG nanoparticle (dose of empty nanoparticles: 100 mg/kg) (ADR þ DexLG NP 10 mg/kg). Calculated amount of ADR-encapsulated DexLG nanoparticles (10 mg ADR/kg mouse) was injected. DOI 10.1002/jps
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Figure 7. Tumor growth after drug injection. Drug or vehicle administration was started at day 15 for 15 days at intervals of 3 days. Eight mice were used for each group. Tumor volume was measured by caliper method. Tumor volume was calculated using the following formula: Tumor volume (mm3) ¼ (length width2)/2. Measurement of tumor growth stopped when survivability were less than four mice.
survivability was checked every day. At treatment with control group, survived mice were gradually decreased according to the time course. Especially, survived mice treated with free ADR plus empty nanoparticle were more rapidly decreased than control group, indicating that free ADR must be highly cytotoxic to animal11 at this dose, while ADR-encapsulated DexLG nanoparticles showed increased survivability of mice. As shown in Figure 7, tumor volume at control group was rapidly increased while tumor growth with free ADR plus empty nanoparticle-treated mice was not significantly increased. At mice treated with nanoparticles, tumor growth was effectively inhibited until 37 days but tumor volume was rapidly increased after that. Although free ADR plus empty nanoparticles was most effective to inhibit tumor growth, survivability was lower than that of ADR-encapsulated DexLG nanoparticles as shown in Figure 6. These results indicated that nanoparticles are effective to inhibit tumor growth and increased survivability of animals.
CONCLUSION ADR-encapsulated core–shell type nanoparticles were prepared to evaluate antitumor activity. JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 6, JUNE 2009
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ADR-encapsulated DexLG nanoparticles showed around 50–200 nm in particle sizes and spherical shapes. After reconstitution of nanoparticles, size was slightly increased while drug release was not significantly changed. The nanoparticles were less cytotoxic than free ADR plus empty nanoparticles in vitro cell cytotoxicity using CT-26 colon carcinoma cells. Even if free ADR plus empty nanoparticles are most effective to inhibit tumor growth at tumor-induced animal model using CT-26 cells, nanoparticles showed increased survivability of mice. These results suggested that ADR-encapsulated DexLG nanoparticles are promising vehicles for antitumor drug delivery.
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