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Научни трудове на Съюза на учените в България-Пловдив. Серия В. Техника и технологии, т. XV, ISSN 1311 -9419 (Print), ISSN 2534-9384 (On- line), 2017. Scientific Works of the Union of Scientists in Bulgaria-Plovdiv, series C. Technics and Technologies, Vol. XV., ISSN 1311 -9419 (Print), ISSN 2534-9384 (On- line), 2017.
НОВИ ЕЛЕКТРООВЛАКНЕНИ МАТЕРИАЛИ С ОБВИВКА ОТ БИОСЪВМЕСТИМИ ПОЛИЕСТЕРИ И СЪРЦЕВИНА, СЪДЪРОРСЩА 1ТЙР1ТИМИН: ПОЛТИААВАНЕ И СВОЙСТВА
Ирена Борисове ОлоСтоилова, Тлтяраоков,Невент Манолова
Лаборато рияБиологичне активни оолимери,Инятитут по полимер и, Българска академия на науките, ул. акад. Г. Бончев, бл. 103А, 1113
Софло,лъиолрия
NEW ELECTROSPUK MUTPROALUWITH SHELL FROM BIOCOMPATIBLE POLYESTERS ANDCURCUMIN-CONTAINING CORE: LRLPACRNIOAOND YALYTUEILS
Irena Borisova, Olya Stoilova, Iliya Rashkov, Nevena Manolova
Laboratory of Bioactive Polymers , Institute of Polymers, Bulgarian Academy ofSciences, Acad.G. Bonchev St., Ы.103А, 1C13 Sofie, Angaria
Abstract
Currently, coaxial electrospinning has gained considerable interest since it enables obtaining core-shell fibers loaded with bioactive compounds encapsulated in the core. The structure of the fibers provides means to protect the bioactive compound from any damaging effects on storage and to modulate the drug release. In the present work the preparation of new micro- and nanofibrous materials containing curcumin - a bioactive compound of plant origin, was studied. The materials were prepared by coaxial electrospinning using polyvinylpyrrolidone/ curcumin solution for the core and poly(3-hydroxybutyrate)/poly(£-caprolactone) solution for the shell. The core-shell structure was evidenced by transmission electron microscopy and by fluorescence microscopy. The release of curcumin from the coaxial-fiber mats was carried out at 37°C. In addition, the antioxidant activity of the materials was evaluated depending on time.
Keywords: coaxial electrospinning, poly(3-hydroxybutyrate), curcumin, antioxidant activity Introduction
Coaxial electrospinning allows one-step preparation of materials with purposely tailored structure and properties [1]. Moreover, coaxial electrospinning enables obtaining core-shell fibers loaded with bioactive compounds encapsulated in the core. Thus, the core-shell structure of the
fibers provides means to protect the bioactive compound from any damaging effects on storage and to modulate its release.
It is well-known that curcumin as a polyphenolic bioactive compound of plant origin has antimicrobial, antioxidant, and anti-inflammatory activity [2]. However, its poor water solubility and instability under illumination limits its applications. To overcome these drawbacks curcumin has been loaded in different micro- and nanoparticles or fibers [3]. Recently, aliphatic polyesters poly(3-hydroxybutyrate) (PHB) and poly(s-caprolactone) (PCL) have been considered as one of the most promising polymers as carriers of bioactive compounds [4]. It is known that the electrospun materials based on these polyesters combines a number of valuable properties and hence great potential for different biomedical applications.
The present study shows the possibilities for preparation of new electrospun materials with shell from biocompatible polyesters (PHB and PCL) and curcumin-containing core. The properties, curcumin release and antioxidant activity of the materials are studied and reported.
Materials and methods
Poly(3-hydroxybutyrate) (PHB, 330000 g/mol), poly(s-caprolactone) (PCL, 80000 g/mol) and polyvinylpyrrolidone (PVP, 360000 g/mol), as well as commercially available curcumin (Curc) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) were of analytical grade of purity. Chloroform (CHO3), dimethyl sulfoxide (DMSO) and A,A-dimethylformamide (DMF) were of analytical grade and used without further purification.
For the fabrication of PVP/Curc-PHB/PCL core-shell fibers, solution of PVP/Curc (10% curcumin in respect to PVP) in DMSO/H2O = 1/1 (v/v) was used as a core solution. A mixed PHB/PCL (1/1 w/w) solution in CHQ3/DMF = 9/1 (v/v) at a total polymer concentration of 14% (w/v) were used as a shell solution. Coaxial electrospinning of PVP/Curc core and PHB/PCL shell was performed at 17 kV applied voltage, coaxial spinneret-to-collector distance of 20 cm and collector rotation speed of 1200 rpm. The flow rates of the core and shell solutions were 1 and 3 ml/h, respectively.
The morphology and core-shell structure of the obtained PVP/Curc-PHB/PCL fibers were studied by scanning electron microscopy (using a Philips SEM 515), transmission electron microscopy (using a JEM 2100 instrument operating at 200 kV) and fluorescence microscopy (using Carl Zeiss fluorescence microscope NU-2).
Results and discussion
The PVP/Curc-PHB/PCL materials were composed of uniform and defect-free fibers as shown by SEM analyses (Fig. 1A). In addition, TEM micrograph (Fig. 1B) clearly evidenced the core-shell structure - a defined dark core and a light shell were observed along the fiber length of the PVP/Curc-PHB/PCL materials. It is known that curcumin is a fluorescent compound, which enable observation by fluorescence microscopy without any addition of fluorescence probe. Indeed, the intensive fluorescence, characteristic of the curcumin in PVP/Curc-PHB/PCL materials appeared (Fig. 1C). This result evidenced that curcumin is uniformly distributed in the fibers.
ABC
Figure 1. Morphology and structure of PVP/Curc-PHB/PCL core-shell fibers: SEM (A), TEM (B) micrographs and fluorescence microscopy (C) image
Thermal properties of the PVP/Curc-PHB/PCL materials were studied by differential scanning calorimetry (performed with a TA Instruments Q200 at a heating rate of 10°C/min from -20 to 200°C). The DSC thermograms of the PHB and PVP/Curc-PHB/PCL are presented in Figure 2. The peak corresponding to the melting temperature of PHB was shifted to lower temperatures - from 166°C for PHB fibers to 164.5°C in the case of PVP/Curc-PHB/PCL. No peak corresponding to the melting point of curcumin (at 175°Q was observed. This indicated that in the core of the PVP/Curc-PHB/PCL, curcumin was amorphous. In addition, PHB crystallinity degree (%) was calculated using the heat of fusion of 100% crystal polymer. The crystallinity degree of PHB from PVP/Curc-PHB/PCL (30%) increased as compared to the PHB fibers (41%). These results, as well the lowering melting temperature of PHB in PVP/Curc-PHB/PCL material probably may be attributed to intermolecular interactions between the polymers and the phenolic compound curcumin.
Figure 2. DSC thermograms (first heating run)
The in vitro release of curcumin from the core-shell PVP/Curc-PHB/PCL materials after storage for one year, was carried out in acetate buffer (pH 5.5) containing Tween 20 (95.5/0.5 v/v) for 24 h at 37°C. The cumulative release percentages of curcumin are presented in Fig. 3. As seen, after 24 h of the release, about 31% of the loaded curcumin had left the core. This result indicated that the core-shell structure successfully can protect and preserve the bioactive compound inside the core after one year of storage and to modulate its release.
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Figure 3. In vitro curcumin release from PVP/Curc-PHB/PCL mats after one-year storage
The effectiveness of the curcumin antioxidant activity after being loaded in the core of the PVP/Curc-PHB/PCL fiber mats was evaluated by DPPH assay. DPPH is a stable free radical, which ethanol solution gives deep violet colour with absorption at 517 nm. The reaction was followed spectrophotometrically by monitoring the decrease of the absorbance of DPPH in the presence of PVP/Curc-PHB/PCL. Antioxidant tests were performed after one-year storage of the materials. As shown in Fig. 4, the DPPH scavenging ability of the loaded in the core curcumin was more than 40% even after 5 min of reaction, as expressed by the calculated antioxidant activity percentage (AA, %). The prepared core-shell materials protect and preserve curcumin during storage, hence keeping its properties undamaged. It was proven that the loaded in the core curcumin preserved its activity.
Time, min
Figure 4. Antioxidant activity percentage of PVP/Curc-PHB/PCL mats after one-year storage
Conclusions
New electrospun materials with shell from biocompatible polyesters (PHB and PCL) and curcumin-containing core were prepared and characterized. The in vitro release and antioxidant effectiveness of the curcumin after being loaded in the core of the PVP/Curc-PHB/PCL fiber mats proved that the core-shell structure successfully can protect and preserve its properties after one year of storage and to modulate its release.
References
1. A. Yarin, E. Zussman, Polymer 45, 2977-2980 (2004).
2. R. Sharma, A. Gescher, W. Steward, Eur. J. Cancer 41, 1955-1968 (2005).
3. O. Naksuriya, S. Okonogi, R. Schiffelers, W. Hennink, Biomaterials 35, 3365-3383 (2014).
4. M. Reddy, S. Vivekanandhan, M. Misra, S. Bhatia, A. Mohanty, Prog. Polym. Sci. 38, 16531689 (2013).
Acknowledgments: Financial support from the National Science Fund (Grant DFNI T02/1 2014) is kindly acknowledged.
e-mail manolova@polymer.bas.bg
