Effect of polycaprolactone on characteristics and morphology of alginate/chitosan/lovastatin composite films - Nguyen Thuy Chinh

Vietnam Journal of Science and Technology 56 (4A) (2018) 13-21 EFFECT OF POLYCAPROLACTONE ON CHARACTERISTICS AND MORPHOLOGY OF ALGINATE/CHITOSAN/LOVASTATIN COMPOSITE FILMS Nguyen Thuy Chinh 1, * , Thach Thi Loc 2 , Le Duc Giang 2 , Ngo Phuong Thuy 3 , Vu Thi Hien 4 , Thai Hoang 1, 5, * 1 Institute for Tropical Technology, Vietnam Academy of Science and Technology 18, Hoang Quoc Viet, Cau Giay, Ha Noi 2 Vinh University, 182 Le Duan, Vinh City, Nghe An 3 Hanoi Pedagogical University 2, No. 32, Nguyen Van Linh, Xuan Hoa, Vinh Phuc 4 Ho Chi Minh City University of Natural Resources and Environment, 236 B Le Van Sy, Tan Binh, Ho Chi Minh City 5 Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi * Email: ntchinh@itt.vast.vn; hoangth@itt.vast.vn Received: 10 July 2018; Accepted for publication: 2 October 2018 ABSTRACT In this work, alginate(AG)/chitosan(CS)/lovastatin(LS)(AG/CS/LS) composite films using polycaprolactone (PCL) as acompatibilizer were prepared by solution method with the ratio of AG/CS and LS content fixed at 4/1 and 10 wt.% (in comparison with the total weight of CS and AG), respectively. The PCL content was varied at 3, 5 and 10 wt.% (wt./wt., calculated on basis of total weight of AG, CS and LS). The role of PCL as a compatibilizer was determined by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and Differential Scanning Calorimetry methods. PCL was found to enhance the compatibility, interaction, and dispersion of CS, AG and LS. The structure of the composite films became more uniform and tight; LS rods were more uniformly dispersed in the AG, CS polymer mixture. The influence of PCL content on the drug release from the composite filmswas also investigated. Keywords: compatibility, polycaprolactone, lovastatin, alginate, solution method. 1. INTRODUCTION Polycaprolactone (PCL) is a biodegradable petroleum-based polymer. It has a semi- crystalline structure with melting pointand glass transition temperature of 55–65 °C and -60 °C, respectively. Its advantageous properties are high toughness, high elongation, and low modulus of elasticity. Thus, it can be blended with other biopolymers, such as polylactic acid (PLA), and starch, etc.to improve itstoughness as well as to produce new biodegradable materials [1-5]. Nguyen Thuy Chinh et al 14 Interestingly, the incorporation of small amounts ( 10 wt.%) of PCL into the starch or PLA/chitosan blend can enhance the compatibility and miscibility of polymers to each other. Rodrigo Ortega-Toro et al. found that melt blending 5 wt.% of PCL and corn thermoplastic starch (with 30 wt.% glycerol) gave a more stretchable and stable films without a notable phase separation [6]. In our previous study [7], PCL was used as a compatibilizer for blends of PLA and chitosan (CS). We observed that PCL increased in the degree of crystallinity, thermal stability, and the miscibility of PLA/CS blend. Since CS is a hydrophobic polymer while alginate (AG) is a hydrophilic polymer, they are difficult to mix and interact with each other. In our previous publications, polyethylene oxide (PEO) was used as a compatibilizer for AG/CS/LS composite films [8-9]. The results showed that PEO can improve the interaction between AG and CS as well as contribute on the LS release from these composites. In literature [9], the effect of PCL on the drug release content and the drug release kinetics of AG/CS/LS composites in pH 2 and pH 7.4 buffer solutions was investigated. However, the structure, morphology, thermal behavior as well as drug release in pH 6.8 buffer solution is still limited to research. Therefore, the aim of this work was to increase the compatibility and dispersion of the components of alginate (AG)/chitosan(CS)/lovastatin (LS) composite films by addition of PCL as a compatibilizer. Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to evaluate the effect of PCL on the compatibility, morphology as well as other characteristics of the AG/CS/LS composite films. 2. EXPERIMENT 2.1. Materials Chitosan (CS, powder, viscosity of 1220 cPs, degree of deacetylation higher than 77 %); sodium alginate (AG, white powder, viscosity of 300–500 mpa.s); lovastatin (LS, powder, purityhigher than 98.0 %); and polycaprolac tone (PCL, melting temperature of 56-64 °C, melting flow index (MFI)of 1.8 g/10 min, number molecular weight (Mn) of 45000 g/mol) were obtained from Sigma-Aldrich, USA; 98 % ethanol 99.5 % acetic acid and dichloromethane were the commercial products of China. 2.2. Preparation of AG/CS/PCL/LS composite films General procedure: 80 mg of AG was dissolved in 20 ml of distilled water (AG solution); 20 mg of CS was dissolved in 20 ml of 1 % acetic acid (CS solution); 10 mg of LS was dissolved in 5 ml of ethanol (LS solution); 3 mg of PCL was dissolved in 5 ml of dichloromethane (PCL solution). Next, the LS solution was poured into the PCL solution before mixing them with AG solution. Then, CS solution was added into the above mixture and they were stirred by sonication for 30 min. Finally, this solution was poured into a petri dish allowing the solvents to evaporate naturally to form the composite film. The composite films with varied PCL content were prepared similarly; the proportion and abbreviation of the composite films were presented in Table 1. 2.3. Characterization of AG/CS/PCL/LS composite films The FTIR spectra of the composite films were recorded at room temperature in air with 4 cm -1 resolution, 16 scans and wave number ranging from 400 to 4000 cm -1 on a Nicolet/Nexus Effect of polycaprolactone on characteristics and morphology of alginate/chitosan/lovastatin 15 670 spectrometer (USA) at Institute for Tropical Technology - Vietnam Academy of Science and Technology(VAST). The morphology of the composite films was determined by Scanning Electron Microscopy (SEM) using an S-4800 FESEM instrument (Hitachi, Japan) at National Institute of Hygiene and Epidemiology. Differential Scanning Calorimetric (DSC)diagrams of the composite films were carried out on a Shimadzu DSC-50 device under N2 atmosphere at heating rate of 10 o C.min −1 from room temperature to 250 o C. The LS drug release content of the composite films was determined based on the data from UV-Vis spectra with the steps as follows:50 mg of each sample was immersed in 500 ml of phosphate buffer solution (PBS, pH 6.8) at 37 o C and placed in an incubated shaker at 120 rpm. At predetermined time intervals, 5 ml of aliquots was withdrawn to carry out the concentration of released LS by UV Spectrophotometer (CINTRA 40, GBC, USA) and replaced with fresh PBS to maintain the total volume. The LS release percent can be determined by the following equation: Drug release [%] = C(t)/C(0) ×100 (1) where C(0) and C(t) represent the amount of loaded and amount of drug released at a time t, respectively. All studies were done in triplicate. Table 1. Compositionsof AG/CS/PCL/LS composite films. Compositions Sample No. AG/CS = 4/1, LS 10 wt.%*, PCL 0 wt.%* P0 AG/CS = 4/1, LS 10 wt.%*, PCL 3 wt.%* PCL3 AG/CS = 4/1, LS 10 wt.%*, PCL 5 wt.%* PCL5 AG/CS = 4/1, LS 10 wt.%*, PCL 10 wt.%* PCL10 *Calculated on basis oftotal weight of AG and CS. 3. RESULTS AND DISCUSSION 3.1. FTIR spectra of AG/CS/PCL/LS composite films The FTIR spectra of the composite films P0, PCL3, PCL5, and PCL10 are shown in Figure 1. Compared with the FTIR spectra ofAG, CS, LS and P0 [10], the peaks characterized for hydroxyl, alkyl, double bond carbon, and C-O groups show a lower intensity. The appearance of two new peaks at 3743 cm -1 and 2360 cm -1 corresponds to the presence of PCL. This can be explained by better dispersion and compatibility of AG and CS in presence of PCL, leading to stronger hydrogen bonding of hydroxyl and amine groups in CS with hydroxyl groups of AG. As a result, the shift of the stretching vibrations of hydrogen bonded amine and hydroxyl groups is occurred. The broad peak at 2155 cm −1 of P0 which is assigned to -NH3C group in the polyion complex membrane (causing by the electrostatic interaction between the carboxylate groups of AG and protonated amino groups from CS) [11-13] is also shifted to 2360 cm -1 . This indicates an enhancement in dispersion and interaction of AG and CS due to the presence of PCL compatibilizer. Nguyen Thuy Chinh et al 16 Figure 1. FTIR spectra of P0, PCL3, PCL5, and PCL10 composite films. Figure 2. A hypothetical model of hydrogen bonding between AG, CS, PCL, and LS in composite films. Table 2. Peaks assignments in AG/CS/LS and AG/CS/PCL/LS composite films. Vibrations Samples Wavenumbers (cm -1 ) –NH2, -OH CH C=O, C=C -NH2, CH C-O-C P0 3386 2923 1604 1411 1079 PCL3 3394 2931 1606 1414 1036 PCL5 3395 2934 1606 1415 1037 PCL10 3393 2934 1607 1415 1037 o HO o OH NH2 n CS LS AG O O n PCL Effect of polycaprolactone on characteristics and morphology of alginate/chitosan/lovastatin 17 Table 2 lists the position of some main peaks in spectra of the above samples. It is clear that the slight shift in wave numbers of hydroxyl, amine, and C-O groups in the FTIR spectra of PCL3, PCL5, and PCL10 proved that AG, CS, PCL, and LS can interact through hydrogen bonding between hydroxyl, amine, and C-O groups of AG, CS, PCL, and LS (a hypothetical model is shown in Figure 2). 3.2. Morphology of AG/CS/PCL/LS compositefilms Figure 3 displays FE-SEM images of P0, PCL3, PCL5, and PCL10. It can be seen that LS rods were evenly distributed with smaller sizes in the composite films having PCL as a compatibilizer, especially in the PCL3 and PCL5 composite films. The presence of PCL enhancedinteraction of LS with AG, CS polymersas hypothesis model of hydrogen bonding in Figure 2. Figure 3.FESEM images of P0 (a), PCL3 (b), PCL5 (c), and PCL10 (d) composite films. 3.3. Thermal behavior of AG/CS/PCL/LS composite films DSC diagrams of AG/CS/PCL/LS composite films are demonstrated in Figure 4. The DSC parameters obtained from the DSC diagrams of AG, CS, LS, P0, PCL3, PCL5, and PCL10 are listed in Table 1. The melting temperature and degradation temperature of AG were 119.6 o C and 238.8 o C [14]. There was only one endothermic peak on the DSC diagram of CS at 106.8 o C corresponding to the loss of adsorbed water due to the hygroscopicity of CS [15]. This also caused to observe difficultly the glass transition temperature of CS. It can be recognized 2 endothermic peaks at 174.6 o C and 264.7 o C in the DSC diagram of LS, corresponding to the loss of adsorbed water and the melting of LS [16-17]. From the Figure 4 and Table 1, it can be seen that there was a broad endothermic peak from 75 o C to 170 o C on the DSC diagrams of the P0, PCL3, PCL5 and PCL10 composite films attributing to overlap of the endothermic peak of CS and AG.A small endothermic peak near 185 o C was appeared in the DSC diagram of the P0 Nguyen Thuy Chinh et al 18 sample but it was disappeared in the DSC diagrams of the PCL3, PCL5 and PCL10 samples. In addition, the area of endothermic peak near 134 o C in the DSC diagram of P0 sample is much larger than that in the DSC diagrams of PCL3, PCL5 and PCL10 composite films. The onset melting temperature of the composite films containing PCL is higher than that of P0 composite films. These evidences mean that the structure of the AG/CS/PCL/LS composite films containing PCL is more uniform and closer than that of the P0 sample, therefore, the AG/CS/PCL/LS composites films are more difficult to be melted. Table 1. DSC parameters obtained from DSC diagrams of AG, CS, LS, P0, PCL3, PCL5 and PCL10 composite films. Sample Onset melting temperature ( o C) Melting temperature ( o C) Melting enthalpy (J/g) AG 76.3 119.6 358.6 CS - 106.8 130.6 LS - 174.6 264.7 90.3 74.1 P0 75.6 134.0 444.6 PCL3 100.9 132.1 374.5 PCL5 79.4 119.9 464.8 PCL10 94.8 125.5 488.0 Figure 3. DSC diagrams of P0 (1), PCL3 (2), PCL5 (3) and PCL10 (4) composite films. 3.4. Drug release study To consider the effect of PCL on the drug release from AG/CS/PCL/LS composite films, the LS release content from the AG/CS/PCL/L composite films in pH 6.8 phosphate buffer solution is calculated according to Eq. 1 and performed in Figure 4. It can be seen that the drug release content is increased as increasing the testing time and corresponded to 2 periods [18-19]. Effect of polycaprolactone on characteristics and morphology of alginate/chitosan/lovastatin 19 The first period is occurred for first 10 testing hours with near 90 wt.% of LS released continuously. This period is considered as the quick release process. Then, the drug release becomes slower and stable with about 5 wt.% of drug released for next 20 testing hours. The total drug release content is near 95 wt.% for all tested samples during 30 testing hours. The drug release content from the PCL3, PCL5 and PCL10 composite films is lower than that of P0 sample. This can be also explained by the improvement of the interaction between AG, CS, and LS in presence of PCL compatibilizer in the composite films. Figure 4. LS release content from P0, PCL3, PCL5 and PCL10 composite films in pH 6.8 phosphate buffer solution. 4. CONCLUSIONS The alginate/chitosan/polycaprolactone/lovastatin (AG/CS/PCL/LS) composite films were prepared by solution method. The presence of PCL as a compatibilizer contributes to enhance the compatibility, interaction and dispersion of CS, AG and LS in the composite films, therefore, LS rods are more uniformly dispersed in the AG/CS//LS composite films, leading to the structure of the composite films is more uniform and tighter. The total LS drug release content from P0, PCL3, PCL5, and PCL10 composite films is near 95 % for 30 testing hours in pH 6.8 phosphate buffer solution. Acknowledgements. The authors would like to thank the Vietnam National Foundation for Science and Technology Development (NAFOSTED) for financial support (grant number 104.02-2017.17, period of 2017–2020). REFERENCES 1. Esmaeilzadeh J., Hesaraki S., Mehdi Hadavi S. M., Esfandeh M., Hosein Ebrahimzadeh M. - Microstructure and mechanical properties of biodegradable poly (D/L) lactic acid/polycaprolactone blends processed from the solvent-evaporation technique, Materials Science and Engineering C 71 (2017) 807–819 0 20 40 60 80 100 0 5 10 15 20 25 30 D ru g r el ea se ( % ) Time (hours) P0 PCL3 PCL5 PCL10 Nguyen Thuy Chinh et al 20 2. Di H., Tian-jiao W., Ge H., Yi-yi D., Yang D., Qin Z., Qiang F. - Synthesis of Janus POSS star polymer and exploring its compatibilization behavior for PLLA/PCL polymer blends, Polymer 136 (2018) 84-91. 3. Kamolrat C., Siriwan P. - Poly(lactic acid)/Polycaprolactone blends compatibilized with block copolymer, Energy Procedia 34 (2013) 542–548. 4. Chen C. C., Chueha J. Y.,Tseng H., Huang H. M., Lee S. Y. -Preparation and characterization of biodegradable PLA polymeric blends, Biomaterials 24 (2003) 1167– 1173. 5. SembaT., KitagawaK., IshiakuU.S., HamadaH. - The effect of crosslinking on the mechanical properties of polylactic acid/polycaprolactone blends, J. Appl. Polym. Sci. 101 (2006) 1816–1825. 6. Ortega-Toro R., Munoz A., Talens P., Chiralt A. - Improvement of properties of glycerol plasticized starch films by blending with a low ratio of polycaprolactone and/or polyethylene glycol. Food Hydrocolloids 56 (2016) 9-19. 7. Trang N. T. T, Chinh N. T, Thanh D. T. M, Hang T. T. X., Giang N. V., Hoang T., Quan P. M., Giang L. D., Thai N. V., and Lawrence G. -Investigating the properties and hydrolysis ability of poly-lactic acid/chitosan nanocomposites using polycaprolactone. Journal of Nanoscience and Nanotechnology15 (12) (2015) 9585– 9590 8. Chinh N. T., Ly N. T. H., Mai T. T., Trang N. T. T., Loc T. T., Giang L. D., Tung N. Q., Hoang T. - Characteristic and properties of chitosan/alginate polymer blend carrying lovastatin drug, Vietnam Journal of Science and Technology 54 (2B) (2016) 118-124. 9. Loc T. T, Hoang T., Chinh N. T., Giang L. D. - The effect of some compatibilizers on the drug release from alginate/chitosan/lovastatins films, Vietnam Journal of Chemistry 56 (3) (2018) 389-393. 10. Chinh N. T., Loc T. T, Giang L. D., Trang N. T. T., Mai T. T., Hoang T. - Effect of polyethylene oxide on properties of chitosan/alginate/lovastatin, Vietnam Journal of Science and Technology 56 (2A) (2018)156-162. 11. Cui-Yun Y., Xi-Chen Z., Fang-Zhou Z., Xian-Zheng Z., Si-Xue C., Ren-Xi Z. - Sustained release of antineoplastic drugs from chitosan-reinforced alginate microparticle drug delivery systems, International Journal of Pharmaceutics 357 (2008) 15-21. 12. Loreana L., Alexandre L.P., Valfredo F., Mauro C. M. L, Hellen K. S. - Development and evaluation of pH-sensitive sodium alginate/chitosan microparticles containing the antituberculosis drug rifampicin, Materials Science and Engineering C 39 (2014) 161-167. 13. Mohy Eldin M. S., Omer A. M., Wassel M. A., Tamer T. M., AbdElmonem M. S., Ibrahim S. A. - Oval smart pH sensitive chitosan grafted alginate hydrogel microcapsules for oral protein delivery: I. preparation and characterization, International Journal of Pharmacy and Pharmaceutical Sciences 7 (10) (2015) 331-337. 14. Helmiyati and Aprilliza M.- Characterization and properties of sodium alginate from brown algae used as an ecofriendly superabsorbent, IOP Conf. Ser.: Mater. Sci. Eng. 188 (2017) 012-019. 15. Sarwar A., Katas H., Samsudin S. N., Zin N. M. - Regioselective sequential modification of chitosan via azide-alkyne click reaction: synthesis, characterization, and antimicrobial activity of chitosan derivatives and nanoparticles, PLoS ONE 10 (4) (2015) e0123084. Effect of polycaprolactone on characteristics and morphology of alginate/chitosan/lovastatin 21 16. Yoshida M. I., Oliveira M. A., Gomes E. C. L., Mussel W. N., Castro W. V., Soares C. D. V. - Thermal characterization of lovastatin in pharmaceutical formulations, Journal of Thermal Analysis and Calorimetry 106 (3) (2011) 657-664. 17. Basavaraj K. Nanjwade, Ganesh K. Derkar, Hiren M. Bechra, Veerendra K. Nanjwade and F.V. Manvi - Design and characterization of nanocrystals of lovastatin for solubility and dissolution enhancement, J. Nanomedic Nanotechnol. 2 (2011) 107. 18. Tarafder S., Nansen K., Bose S. - Lovastatin release from polycaprolactone coated β- tricalcium phosphate: Effects of pH, concentration and drug–polymer interactions, Materials Science and Engineering C 33 (2013) 3121–3128. 19. Liang L., Jinfeng L., Shanshan S., Linlin W., Chenjun S., Yujiao S., Zhenglin L., Shirui M. - Effect of formulation variables on in vitro release of a water-soluble drug from chitosan-sodium alginate matrix tablets, Asia Journal of Pharmaceutical Sciences 10 (2015) 314-321.