- Email: [email protected]
A novel heparin release system based on blends of biomedical polyurethane and native silk fibroin powder
Abstracts / Journal of Controlled Release 152 (2011) e1–e132
Results and discussion 1 H NMR demonstrated that PEG–PAC–PLA triblock copolymer had block lengths of 5000–1200–4800 g/mol. Dynamic light scattering (DLS) measurements showed that mixed micelles of PEG–PAC–PLA and folate–PEG–PLA at an initial PTX loading of 10 wt.% had average diameters of 160–172 nm with a PDI of 0.10– 0.24 (Table 1). The micelles after UV irradiation became smaller with a diameter reduction of 32–75 nm. The drug loading efficiency of crosslinked micelles ranged from 70% to 88% (Table 1). As expected, the crosslinked micelles were very stable against 1000 times dilution as well as organic solvents (e.g. THF). The stabilization mechanism was based on the photopolymerization of double bonds, which was confirmed by complete disappearance of the double bond absorbance at 250 nm in the UV–Vis spectrum of the micelles after 15 min UV irradiation (Fig. 1a). The cytotoxicity of the crosslinked micelles PEG–PAC–PLA was assessed by MTT assays using KB cells. It was revealed that at the tested micelle concentration range (up to 400 μg/mL), these micelles in the presence of photo initiator I2959 (0.05 wt.%) were non-toxic (Fig. 1b).
a 1.2
the crosslinked micelles the initial micelles
140
Cell viability (%)
120
Abs
0.8 0.6 0.4 0.2 0.0 200
100 80 60 40 20 0
240
280
320
80
60
40
20
0 0
20
40
60
80
100
Time (h) Fig. 2. In vitro PTX release from the mixed micelles of PEG–PAC–PLA/FA–PEG–PLA 80/ 20 at concentrations of 0.33 or 0.066 mg/mL at pH 7.4 and 37 °C.
Conclusion We have developed photo-crosslinked biodegradable micelles based on the triblock copolymer PEG–PAC–PLA. These novel biodegradable micelles have the following features: (i) they are not cytotoxic; (ii) the photo-crosslinking reaction readily takes place in aqueous conditions; (iii) crosslinked micelles are robust, effectively retarding drug release over dilution; and (iv) tumor-targeting micelles can be readily obtained with varying folate densities. These crosslinked biodegradable micelles are potentially interesting for targeted cancer therapy.
b
1.0
micelles, 0.33 mg/mL crosslinked micelles, 0.33 mg/mL micelles, 0.066 mg/mL crosslinked micelles, 0.066 mg/mL
100
Cumulative release (%)
e106
25
100
200
400
Wavelength (nm)
Fig. 1. UV–Vis spectra of crosslinked and non-crosslinked micelles of PEG–PAC–PLA (a) and the cytotoxicity of PEG–PAC–PLA micelles in the presence of photoinitiator I2959 assessed by the MTT assay (KB cell, 24 h incubation) (b).
Table 1 Loading of PTX into mixed micelles of PEG–PAC–PLA and folate–PEG–PLA (PTX feed ratio 10 wt.%). Entry
1 2 3 4 a
Folate–PEG–PLA/ PEG–PAC–PLA (w/w)
Size before irradiation (nm)a/PDI
Size after irradiation (nm)a/PDI
Loading contentb (wt.%)
Loading efficiencyb (%)
0/100 5/95 10/90 20/80
171/0.10 164/0.18 170/0.24 172/0.14
139/0.06 100/0.08 85/0.14 122/0.05
8.8 8.4 7.4 7.0
88 84 74 70
Determined by DLS;
b
determined by HPLC.
The release of PTX from crosslinked and non-crosslinked micelles was studied using PB (10 mM, pH 7.4) at 37 °C (Fig. 2). The micelles loaded with PTX were divided into two groups: one with a micelle concentration of 0.33 mg/mL and the other with a micelle concentration of 0.066 mg/mL which is close to the CMC (ca. 2.5 mg/L). At a concentration of 0.33 mg/mL, minimal release of PTX was observed for both crosslinked and non-crosslinked micelles (Fig. 2). At a lower concentration of 0.066 mg/mL, noncrosslinked micelles released most of the drug in 96 h while crosslinked micelles showed only ca. 28% drug release under otherwise the same conditions. These results confirm that photocrosslinked mixed micelles of PEG–PAC–PLA and folate–PEG–PLA have largely improved drug stability.
Acknowledgements This work is financially supported by research grants from the National Natural Science Foundation of China (NSFC 50703028, 20974073, 50973078 and 20874070), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (08KJB150016), Scientific Research Foundation for Returned Overseas Chinese Scholars (Ministry of Education), and the Program of Innovative Research Team of Soochow University.
References [1] E.S. Read, S.P. Armes, Recent advances in shell cross-linked micelles, Chem. Commun. 29 (2007) 3021–3035. [2] A. Rösler, G.W.M. Vandermeulen, H.-A. Klok, Advanced drug delivery devices via selfassembly of amphiphilic block copolymers, Adv. Drug Deliv. Rev. 53 (2001) 95–108. [3] W. Chen, H.C. Yang, R. Wang, R. Cheng, F.H. Meng, W.X. Wei, Z.Y. Zhong, Versatile synthesis of functional biodegradable polymers by combining ring-opening polymerization and postpolymerization modification via Michael-type addition reaction, Macromolecules 43 (2010) 201–207.
doi:10.1016/j.jconrel.2011.08.154
A novel heparin release system based on blends of biomedical polyurethane and native silk fibroin powder Hongjun Yang1, Haiye Xu2, Hongtao Liu2, Chenxi Ouyang3, Weilin Xu2 1 College of Textiles, Donghua University, Shanghai 201620, China 2 Textile Research Center, Wuhan Textile University, Wuhan 430073, China 3 Department of Vascular Surgery, Union Hospital, Tongji Medical College of Huazhong University of Science & Technology, Wuhan 430022, China E-mail address: [email protected] (W. Xu).
Abstracts / Journal of Controlled Release 152 (2011) e1–e132
e107
Abstract summary Native silk fibroin powder (NSFP) carrying heparin was blended with biomedical polyurethane (BPU) to make novel composite membranes for the controlled release of heparin. The release of heparin from the composite membrane can be adjusted by adjusting the blend ratios of NSFP and BPU, the amount of heparin in the membrane and the membrane thickness. The heparin released from the novel release system has excellent bioactivity.
Keywords: Composite membrane, Controlled drug release, Polyurethane, Silk powder, Heparin
Introduction Recently, biomedical polyurethane (BPU) has attracted a great deal of research interest and has been used in small-diameter prosthesis due to its superior mechanical properties and good biocompatibility [1]. However, when polyurethane was used in small-diameter prosthesis as the blood-contacting material, thrombus formation and inflammation still existed [2]. A heparin release system was used to prevent the formation of thrombus on the surface of polyurethane vascular graft. Many methods have been studied for the formulation of the heparin-releasing system [3]. A common issue with those releasing systems is that either the heparin was released within several hours or could not be released from BPU membranes, so a novel formulation for controlled release of heparin is necessary. In this paper, native silk fibroin powder (NSFP) was used in a heparin-releasing system for improving both the quantity and duration of heparin release.
Experimental methods Silk cocoons were firstly degummed to remove sericin. Cocoons were dissolved in 0.25% (w/v) sodium lauryl sulfate and 0.25% (w/v) sodium carbonate aqueous solution at 80 °C for 100 min. The extracted silk cocoons were then ground into fine powder with our purpose-built grinding machine [4,5]. The NSFP was dispersed in an aqueous solution of heparin at a ratio of 1:6 (w/w). Heparinized native silk fibroin powder (H-NSFP) was obtained by drying the blended aqueous solutions of powder and drug in an air circulating oven under 40 °C, followed by grinding again with our purpose-built grinding machine. The drug delivery system based on BPU and H-NSFP was fabricated by a phase inversion technique at room temperature.
Results and discussion Fig. 1 shows the morphology of the composite membrane. A smooth surface with micropores and NSFP was obtained on the surface of the composite membrane prepared by a phase inverse technique at room temperature. The micropores and NSFP provided channels for the release of heparin from the composite. The release of heparin from NSFP/BPU composite membranes was investigated. The effect of three parameters, NSFP/BPU blend ratios, the amount of drug in the membrane and the membrane thickness, on the release rate were studied. As shown in Figs. 2 and 3, the release of heparin from the composite membranes decreased with the increase of NSFP content and membrane thickness when the same amount of heparin was added into the membrane. However, the release increased with the increase of heparin content in the composite membranes with the same NSFP/BPU blend ratio and thickness (Fig. 4). Therefore, the release of heparin from the membrane can be controlled by adjusting three parameters, NSFP/BPU blend ratios, the amount of heparin in the membrane and membrane thickness.
Fig.1. The morphology of a NSFP/BPU composite membrane prepared by a phase inversion technique at room temperature. Distilled water was used as coagulation solution in this study and NSFP containing heparin uniformly distributed into membrane.
Fig. 2. Release profiles of heparin from NSFP/BPU composite membranes with different NSFP/BPU ratios. The thickness of membranes was about 110 μm and the amount of heparin sodium in membranes was 10% (a. NSFP/BPU = 30/70; b. NSFP/BPU = 50/50; c. NSFP/BPU = 70/30).
Fig. 3. Release profiles of heparin from NSFP/BPU (30/70) composite membranes containing the same loading amount of heparin but with different membrane thickness (a. 110 μm; b. 160 μm; c. 210 μm).
e108
Abstracts / Journal of Controlled Release 152 (2011) e1–e132
Platinum (IV)-coordinate polymers for cancer drug delivery Jun Yang, Weiwei Mao, Meihua Sui, Jianbin Tang, Youqing Shen Center for Bionanoengineering and Nanomedicine and Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China E-mail address: [email protected] (Y. Shen). Abstract summary Platinum (IV)-coordinate polymers were synthesized using dihydroxy platinum (IV) (ACHP) as a comonomer with dianhydrides and diamines. The backbone-type polymer–drug conjugates had both higher platinum content and good water-solubility. They showed higher cytotoxicity compared with Pt (IV) monomers toward MDA-MB-468 cells. Fig. 4. Release profiles of heparin from NSFP/BPU (30/70) composite membranes containing different amounts of heparin for 48 h. The thickness of membranes was 110 μm (a. heparin = 5%; b. heparin = 7.5%; c. heparin = 10%).
The normal results of thrombin time (TT), activated partial thromboplastin time (APTT) and prothrombin time (PT) for a healthy blood plasma were regarded as 16 ± 5 s, 28 ± 4 s and 11 ± 3 s, respectively [2]. The three parameters, TT, APTT and PT, were used to evaluate the bioactivity of heparin released from composite membranes and the results are shown in Table 1. The three parameters all exceeded the measurement limit of the clot-detection instrument, indicating that the heparin released from NSFP/BPU composite membranes has excellent bioactivity. Table 1 TT, APTT and PT of NSFP/BPU composite membrane containing heparin. The percentage of heparin 0% 5% 7.5% 10%
Clot time (s) TT
APTT
PT
14.6 N150 N150 N150
37.3 N 200 N 200 N 200
12.5 N 150 N 150 N 150
Conclusion In this study, Silk fibroin powder was prepared by a mechanical grinding method and used in a heparin release system. The release of heparin from the membrane was evaluated and the results indicated that the release of heparin can be controlled effectively by adjusting the amount of heparin in the membrane, the blend ratios of NSFP and BPU and the membrane thickness. Acknowledgements This work was supported by the 973 Project of China (No. 2009CB526402) and the National Natural Science Foundation of China (No. 50873079). References [1] M.T. Khorasani, S. Shorgashti, Fabrication of microporous inversion method as small material polyurethane by spray phase diameter vascular grafts, J. Biomed. Mater. Res. Part A 77A (2006) 253–260. [2] Q. Lv, C. Cao, H. Zhu, A novel solvent system for blending of polyurethane and heparin, Biomaterials 24 (2003) 3915–3919. [3] K. Christensen, R. Larsson, H. Emanuelsson, G. Elgue, A. Larsson, Heparin coating of the stent graft-effects on platelets, coagulation and complement activation, Biomaterials 22 (2001) 349–355. [4] W.L. Xu, W.G. Cui, W.B. Li, W.Q. Guo, Development and characterizations of super-fine wool powder, Powder Technol. 140 (2004) 136–140. [5] W.L. Xu, W.Q. Guo, W.B. Li, Thermal analysis of ultrafine wool powder, J. Appl. Polym. Sci. 87 (2003) 2372–2376.
doi:10.1016/j.jconrel.2011.08.155
Keywords: Platinum (IV)-conjugate, Platinum (IV) prodrug, Drug delivery Introduction cis-Diamminedichloroplatinum (II) (cisplatin) and related compounds are still among the most used anticancer drugs against a variety of types of cancer [1, 2]. However, cisplatin has severe toxic side-effects [3] and cancer cells can easily develop drug resistance to these Pt(II) based drugs. Among the large variety of platinum compounds explored aimed at improving the antitumor efficiency while minimizing the adverse side effects, platinum (Pt) (IV) complexes, as the prodrugs of Pt (II), have been found to overcome some of the problems associated with cisplatin and its analogs [4,5]. The high kinetic inertness of Pt (IV) complexes relative to their Pt (II) analogs stabilizes the drugs, which is proposed as a better way of delivering cisplatin (or its analogs) to the target tumor cell. Pt(IV) drugs are also found less subject to some drug resistance mechanisms [6]. The six-coordinate Pt(IV) center can be used to modify the drugs for lipophilicity, stability, reduction behavior, and biological activity [7], and overcoming Glutathione-S-Transferase Mediated Drug Resistance [8]. Many Pt (IV) prodrugs were synthesized and tested for cancer chemotherapy [9,10]. They were also grafted on carbon nanotubes [11,12], nanoparticles [4] or peptides for enhanced efficacy or targeting [13]. Herein, we report novel platinum (IV)-coordinate polymers as backbone type drug conjugates. The conjugates have relatively high platinum content and similar or higher cytotoxicity compared with their monomers. Experimental methods c,c,t-Pt(NH3)2(OH)2Cl2(ACHP) and c,c,t-Pt(NH3)2Cl2(OOCCH2CH2CO2H)2(DSCP) were synthesized according to the reported references [14,15]. Synthesis of Pt (IV) conjugate, ACPPEG5. ACPA was prepared by mixing ACHP with cyclobutan-1,2,3,4-tetracarboxylic dianhydride (CBTA) in DMSO at 60 °C for 24 h, and precipitated in methanol. ACPPEG5 was synthesized by reacting ACPA with poly(ethylene glycol) methyl ether (mPEG550, average Mn ~ 550) in the presence of EDC and DMAP. The resulting solution was dialyzed against H2O and lyophilized. Synthesis of Pt (IV) conjugate, DEACP and DPAP. The DSCP was reacted with ethylene diamine or piperazine, respectively, under the addition of EDC and NHS. In vitro cytotoxicity assay. The cytotoxicity of the Pt (IV) conjugates were assessed by using the MTT cell proliferation assays. The cells were incubated with drugs for 72 h and post-incubated for 24 h before being measured by a MTT reagent using a universal microplate spectrophotometer.
Results and discussion 1 H NMR demonstrated that PEG–PAC–PLA triblock copolymer had block lengths of 5000–1200–4800 g/mol. Dynamic light scattering (DLS) measurements showed that mixed micelles of PEG–PAC–PLA and folate–PEG–PLA at an initial PTX loading of 10 wt.% had average diameters of 160–172 nm with a PDI of 0.10– 0.24 (Table 1). The micelles after UV irradiation became smaller with a diameter reduction of 32–75 nm. The drug loading efficiency of crosslinked micelles ranged from 70% to 88% (Table 1). As expected, the crosslinked micelles were very stable against 1000 times dilution as well as organic solvents (e.g. THF). The stabilization mechanism was based on the photopolymerization of double bonds, which was confirmed by complete disappearance of the double bond absorbance at 250 nm in the UV–Vis spectrum of the micelles after 15 min UV irradiation (Fig. 1a). The cytotoxicity of the crosslinked micelles PEG–PAC–PLA was assessed by MTT assays using KB cells. It was revealed that at the tested micelle concentration range (up to 400 μg/mL), these micelles in the presence of photo initiator I2959 (0.05 wt.%) were non-toxic (Fig. 1b).
a 1.2
the crosslinked micelles the initial micelles
140
Cell viability (%)
120
Abs
0.8 0.6 0.4 0.2 0.0 200
100 80 60 40 20 0
240
280
320
80
60
40
20
0 0
20
40
60
80
100
Time (h) Fig. 2. In vitro PTX release from the mixed micelles of PEG–PAC–PLA/FA–PEG–PLA 80/ 20 at concentrations of 0.33 or 0.066 mg/mL at pH 7.4 and 37 °C.
Conclusion We have developed photo-crosslinked biodegradable micelles based on the triblock copolymer PEG–PAC–PLA. These novel biodegradable micelles have the following features: (i) they are not cytotoxic; (ii) the photo-crosslinking reaction readily takes place in aqueous conditions; (iii) crosslinked micelles are robust, effectively retarding drug release over dilution; and (iv) tumor-targeting micelles can be readily obtained with varying folate densities. These crosslinked biodegradable micelles are potentially interesting for targeted cancer therapy.
b
1.0
micelles, 0.33 mg/mL crosslinked micelles, 0.33 mg/mL micelles, 0.066 mg/mL crosslinked micelles, 0.066 mg/mL
100
Cumulative release (%)
e106
25
100
200
400
Wavelength (nm)
Fig. 1. UV–Vis spectra of crosslinked and non-crosslinked micelles of PEG–PAC–PLA (a) and the cytotoxicity of PEG–PAC–PLA micelles in the presence of photoinitiator I2959 assessed by the MTT assay (KB cell, 24 h incubation) (b).
Table 1 Loading of PTX into mixed micelles of PEG–PAC–PLA and folate–PEG–PLA (PTX feed ratio 10 wt.%). Entry
1 2 3 4 a
Folate–PEG–PLA/ PEG–PAC–PLA (w/w)
Size before irradiation (nm)a/PDI
Size after irradiation (nm)a/PDI
Loading contentb (wt.%)
Loading efficiencyb (%)
0/100 5/95 10/90 20/80
171/0.10 164/0.18 170/0.24 172/0.14
139/0.06 100/0.08 85/0.14 122/0.05
8.8 8.4 7.4 7.0
88 84 74 70
Determined by DLS;
b
determined by HPLC.
The release of PTX from crosslinked and non-crosslinked micelles was studied using PB (10 mM, pH 7.4) at 37 °C (Fig. 2). The micelles loaded with PTX were divided into two groups: one with a micelle concentration of 0.33 mg/mL and the other with a micelle concentration of 0.066 mg/mL which is close to the CMC (ca. 2.5 mg/L). At a concentration of 0.33 mg/mL, minimal release of PTX was observed for both crosslinked and non-crosslinked micelles (Fig. 2). At a lower concentration of 0.066 mg/mL, noncrosslinked micelles released most of the drug in 96 h while crosslinked micelles showed only ca. 28% drug release under otherwise the same conditions. These results confirm that photocrosslinked mixed micelles of PEG–PAC–PLA and folate–PEG–PLA have largely improved drug stability.
Acknowledgements This work is financially supported by research grants from the National Natural Science Foundation of China (NSFC 50703028, 20974073, 50973078 and 20874070), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (08KJB150016), Scientific Research Foundation for Returned Overseas Chinese Scholars (Ministry of Education), and the Program of Innovative Research Team of Soochow University.
References [1] E.S. Read, S.P. Armes, Recent advances in shell cross-linked micelles, Chem. Commun. 29 (2007) 3021–3035. [2] A. Rösler, G.W.M. Vandermeulen, H.-A. Klok, Advanced drug delivery devices via selfassembly of amphiphilic block copolymers, Adv. Drug Deliv. Rev. 53 (2001) 95–108. [3] W. Chen, H.C. Yang, R. Wang, R. Cheng, F.H. Meng, W.X. Wei, Z.Y. Zhong, Versatile synthesis of functional biodegradable polymers by combining ring-opening polymerization and postpolymerization modification via Michael-type addition reaction, Macromolecules 43 (2010) 201–207.
doi:10.1016/j.jconrel.2011.08.154
A novel heparin release system based on blends of biomedical polyurethane and native silk fibroin powder Hongjun Yang1, Haiye Xu2, Hongtao Liu2, Chenxi Ouyang3, Weilin Xu2 1 College of Textiles, Donghua University, Shanghai 201620, China 2 Textile Research Center, Wuhan Textile University, Wuhan 430073, China 3 Department of Vascular Surgery, Union Hospital, Tongji Medical College of Huazhong University of Science & Technology, Wuhan 430022, China E-mail address: [email protected] (W. Xu).
Abstracts / Journal of Controlled Release 152 (2011) e1–e132
e107
Abstract summary Native silk fibroin powder (NSFP) carrying heparin was blended with biomedical polyurethane (BPU) to make novel composite membranes for the controlled release of heparin. The release of heparin from the composite membrane can be adjusted by adjusting the blend ratios of NSFP and BPU, the amount of heparin in the membrane and the membrane thickness. The heparin released from the novel release system has excellent bioactivity.
Keywords: Composite membrane, Controlled drug release, Polyurethane, Silk powder, Heparin
Introduction Recently, biomedical polyurethane (BPU) has attracted a great deal of research interest and has been used in small-diameter prosthesis due to its superior mechanical properties and good biocompatibility [1]. However, when polyurethane was used in small-diameter prosthesis as the blood-contacting material, thrombus formation and inflammation still existed [2]. A heparin release system was used to prevent the formation of thrombus on the surface of polyurethane vascular graft. Many methods have been studied for the formulation of the heparin-releasing system [3]. A common issue with those releasing systems is that either the heparin was released within several hours or could not be released from BPU membranes, so a novel formulation for controlled release of heparin is necessary. In this paper, native silk fibroin powder (NSFP) was used in a heparin-releasing system for improving both the quantity and duration of heparin release.
Experimental methods Silk cocoons were firstly degummed to remove sericin. Cocoons were dissolved in 0.25% (w/v) sodium lauryl sulfate and 0.25% (w/v) sodium carbonate aqueous solution at 80 °C for 100 min. The extracted silk cocoons were then ground into fine powder with our purpose-built grinding machine [4,5]. The NSFP was dispersed in an aqueous solution of heparin at a ratio of 1:6 (w/w). Heparinized native silk fibroin powder (H-NSFP) was obtained by drying the blended aqueous solutions of powder and drug in an air circulating oven under 40 °C, followed by grinding again with our purpose-built grinding machine. The drug delivery system based on BPU and H-NSFP was fabricated by a phase inversion technique at room temperature.
Results and discussion Fig. 1 shows the morphology of the composite membrane. A smooth surface with micropores and NSFP was obtained on the surface of the composite membrane prepared by a phase inverse technique at room temperature. The micropores and NSFP provided channels for the release of heparin from the composite. The release of heparin from NSFP/BPU composite membranes was investigated. The effect of three parameters, NSFP/BPU blend ratios, the amount of drug in the membrane and the membrane thickness, on the release rate were studied. As shown in Figs. 2 and 3, the release of heparin from the composite membranes decreased with the increase of NSFP content and membrane thickness when the same amount of heparin was added into the membrane. However, the release increased with the increase of heparin content in the composite membranes with the same NSFP/BPU blend ratio and thickness (Fig. 4). Therefore, the release of heparin from the membrane can be controlled by adjusting three parameters, NSFP/BPU blend ratios, the amount of heparin in the membrane and membrane thickness.
Fig.1. The morphology of a NSFP/BPU composite membrane prepared by a phase inversion technique at room temperature. Distilled water was used as coagulation solution in this study and NSFP containing heparin uniformly distributed into membrane.
Fig. 2. Release profiles of heparin from NSFP/BPU composite membranes with different NSFP/BPU ratios. The thickness of membranes was about 110 μm and the amount of heparin sodium in membranes was 10% (a. NSFP/BPU = 30/70; b. NSFP/BPU = 50/50; c. NSFP/BPU = 70/30).
Fig. 3. Release profiles of heparin from NSFP/BPU (30/70) composite membranes containing the same loading amount of heparin but with different membrane thickness (a. 110 μm; b. 160 μm; c. 210 μm).
e108
Abstracts / Journal of Controlled Release 152 (2011) e1–e132
Platinum (IV)-coordinate polymers for cancer drug delivery Jun Yang, Weiwei Mao, Meihua Sui, Jianbin Tang, Youqing Shen Center for Bionanoengineering and Nanomedicine and Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China E-mail address: [email protected] (Y. Shen). Abstract summary Platinum (IV)-coordinate polymers were synthesized using dihydroxy platinum (IV) (ACHP) as a comonomer with dianhydrides and diamines. The backbone-type polymer–drug conjugates had both higher platinum content and good water-solubility. They showed higher cytotoxicity compared with Pt (IV) monomers toward MDA-MB-468 cells. Fig. 4. Release profiles of heparin from NSFP/BPU (30/70) composite membranes containing different amounts of heparin for 48 h. The thickness of membranes was 110 μm (a. heparin = 5%; b. heparin = 7.5%; c. heparin = 10%).
The normal results of thrombin time (TT), activated partial thromboplastin time (APTT) and prothrombin time (PT) for a healthy blood plasma were regarded as 16 ± 5 s, 28 ± 4 s and 11 ± 3 s, respectively [2]. The three parameters, TT, APTT and PT, were used to evaluate the bioactivity of heparin released from composite membranes and the results are shown in Table 1. The three parameters all exceeded the measurement limit of the clot-detection instrument, indicating that the heparin released from NSFP/BPU composite membranes has excellent bioactivity. Table 1 TT, APTT and PT of NSFP/BPU composite membrane containing heparin. The percentage of heparin 0% 5% 7.5% 10%
Clot time (s) TT
APTT
PT
14.6 N150 N150 N150
37.3 N 200 N 200 N 200
12.5 N 150 N 150 N 150
Conclusion In this study, Silk fibroin powder was prepared by a mechanical grinding method and used in a heparin release system. The release of heparin from the membrane was evaluated and the results indicated that the release of heparin can be controlled effectively by adjusting the amount of heparin in the membrane, the blend ratios of NSFP and BPU and the membrane thickness. Acknowledgements This work was supported by the 973 Project of China (No. 2009CB526402) and the National Natural Science Foundation of China (No. 50873079). References [1] M.T. Khorasani, S. Shorgashti, Fabrication of microporous inversion method as small material polyurethane by spray phase diameter vascular grafts, J. Biomed. Mater. Res. Part A 77A (2006) 253–260. [2] Q. Lv, C. Cao, H. Zhu, A novel solvent system for blending of polyurethane and heparin, Biomaterials 24 (2003) 3915–3919. [3] K. Christensen, R. Larsson, H. Emanuelsson, G. Elgue, A. Larsson, Heparin coating of the stent graft-effects on platelets, coagulation and complement activation, Biomaterials 22 (2001) 349–355. [4] W.L. Xu, W.G. Cui, W.B. Li, W.Q. Guo, Development and characterizations of super-fine wool powder, Powder Technol. 140 (2004) 136–140. [5] W.L. Xu, W.Q. Guo, W.B. Li, Thermal analysis of ultrafine wool powder, J. Appl. Polym. Sci. 87 (2003) 2372–2376.
doi:10.1016/j.jconrel.2011.08.155
Keywords: Platinum (IV)-conjugate, Platinum (IV) prodrug, Drug delivery Introduction cis-Diamminedichloroplatinum (II) (cisplatin) and related compounds are still among the most used anticancer drugs against a variety of types of cancer [1, 2]. However, cisplatin has severe toxic side-effects [3] and cancer cells can easily develop drug resistance to these Pt(II) based drugs. Among the large variety of platinum compounds explored aimed at improving the antitumor efficiency while minimizing the adverse side effects, platinum (Pt) (IV) complexes, as the prodrugs of Pt (II), have been found to overcome some of the problems associated with cisplatin and its analogs [4,5]. The high kinetic inertness of Pt (IV) complexes relative to their Pt (II) analogs stabilizes the drugs, which is proposed as a better way of delivering cisplatin (or its analogs) to the target tumor cell. Pt(IV) drugs are also found less subject to some drug resistance mechanisms [6]. The six-coordinate Pt(IV) center can be used to modify the drugs for lipophilicity, stability, reduction behavior, and biological activity [7], and overcoming Glutathione-S-Transferase Mediated Drug Resistance [8]. Many Pt (IV) prodrugs were synthesized and tested for cancer chemotherapy [9,10]. They were also grafted on carbon nanotubes [11,12], nanoparticles [4] or peptides for enhanced efficacy or targeting [13]. Herein, we report novel platinum (IV)-coordinate polymers as backbone type drug conjugates. The conjugates have relatively high platinum content and similar or higher cytotoxicity compared with their monomers. Experimental methods c,c,t-Pt(NH3)2(OH)2Cl2(ACHP) and c,c,t-Pt(NH3)2Cl2(OOCCH2CH2CO2H)2(DSCP) were synthesized according to the reported references [14,15]. Synthesis of Pt (IV) conjugate, ACPPEG5. ACPA was prepared by mixing ACHP with cyclobutan-1,2,3,4-tetracarboxylic dianhydride (CBTA) in DMSO at 60 °C for 24 h, and precipitated in methanol. ACPPEG5 was synthesized by reacting ACPA with poly(ethylene glycol) methyl ether (mPEG550, average Mn ~ 550) in the presence of EDC and DMAP. The resulting solution was dialyzed against H2O and lyophilized. Synthesis of Pt (IV) conjugate, DEACP and DPAP. The DSCP was reacted with ethylene diamine or piperazine, respectively, under the addition of EDC and NHS. In vitro cytotoxicity assay. The cytotoxicity of the Pt (IV) conjugates were assessed by using the MTT cell proliferation assays. The cells were incubated with drugs for 72 h and post-incubated for 24 h before being measured by a MTT reagent using a universal microplate spectrophotometer.