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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 КУРКУМИН-СЪДЪРЖАЩИ НАНОВЛАКНЕСТИ ШТТЕРИАЛИ НА ОСНОВАТА НА ЦЕЛУЛОЗЕН АЦЕТАТ, ПОЛУЧЕНИ ЧРЕЗ ЕЛЕКТРНОВЛАКТЯВАНЕ И ЕАЕТТРОРАЗПРТТКВАНЕ Петя ЦековаТ, Мартя Тнясото1, НЕвенка Манолова1, Илия Рашков1, Надя Маркова2 1Лаборатория Биологично активни полиме ри, Институт по полимери, Българскк академия на нлулите 2Институт по мБългаркка аклеемия на науките
novel curcumin-containing@ellijlosea cetate-based
NANOFIBROUS MATERIALS PREPARED BY ELECTROSPINNING
AND ELECTROSPRAYING Petya Tsekova1*, Mariya SpasovaS Nevena Monolova1, Iliya Rashkov1, Nadya Markova2 1Laboratory of Bioactive Polymers, Institute of Polymers,
Bulga rian Aynd emyof Sciences 2Institute of Microbi olegy,Bulgariyn A cademy of Sciences
Abstract
Curcumin is a naturally occurring phenolic compound with antioxidant properties and antimicrobial activity. The extremely low water solubility of curcumin limits the possibilities for its application in the biomedical field. New polymer materials for enhanced release of curcumin in aqueous medium were developed. Different approaches were used to create curcumin-containing cellulose acetate-based nanofibrous materials of various design using electrospinning and electrospraying. The effects of the composition and the design of the materials on curcumin release were studied. The curcumin-loaded materials exhibited antibacterial activity against pathogenic microorganisms. The results suggest that the obtained new materials are promising for wound dressing applications.
Key words: electrospinning, electrospraying, fibrous materials, curcumin, cellulose acetate Introduction
Cellulose is the most abundant naturally occurring polysaccharide. Bioactive wound dressings that take active part in the healing process may be loaded with naturally occurring compounds to enhance wound healing process (Boateng, 2008). Curcumin is a biologically active substance found in the roots of Curcuma longa plant. This naturally occurring polyphenolic compound 166
manifests antibacterial (Moghadamtousi, 2014), anti-inflammatory (Basnet, 2011) and antitumor (Sarika, 2016) activity. The main disadvantage of Curc is its poor aqueous solubility. Incorporation of Curc in polymer matrix is expected to contribute to obviating this drawback. In the recent years, fibrous nonwoven materials produced by electrospinning have shown great potential as wound dressing materials (Toncheva, 2014; Spasova, 2008).
The aim of the present study was to obtain novel Curc-containing fibrous materials with diverse architecture using the versatility of combining the techniques electrospraying and electrospinning. The morphology and structure of the obtained electrospun materials have been characterized. The antibacterial activity upon contact of the mats with Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli) has been evaluated.
Experimental
Materials
Cellulose acetate (CA, Aldrich) with Mn 30,000 g/mol and acetyl content 39.8%, polyvinylpyrrolidone (PVP, Fluka) with Mr 360.000 g/mol and curcumin (Curc,Merck) were used. Acetone was of analytical grade of purity and was purchased from Sigma-Aldrich.
Preparation of fibrous materials of Curc/PVP-on-CA by conjunction of electrospinning and electrospraying
Curc/PVP-on-CA materials were fabricated by using two pumps for delivering: (i) CA solution and (ii) Curc/PVP solution. The pumps for delivering the spinning solutions were located at an angle of 180° in respect to the rotating collector (1000 rpm). The delivery rate of the spinning solutions was 3 ml/h. The tip-to-collector distance was 15 cm. The applied voltage was provided using a common high voltage power supply at a constant applied voltage of 25 kV. CA solution with concentration 10 wt% in acetone/water (80/20 v/v) was subjected to electrospinning and PVP and Curc mixed solution was electrosprayed. Curc was 10% in respect to polymer(s) weight.
Preparation of fibrous materials of CA and Curc-in-CA by electrospinning
CA and Curc-in-CA fibrous mats were prepared according to the procedure described earlier (Tsekova, 2017).
Characterization of the nanofibrous materials
The morphology of the fibrous materials was evaluated by scanning electron microscopy (SEM) with Jeol JSM-5510 (Jeol Ltd., Japan). X-ray diffraction (XRD) analyses were performed at room temperature using a computer-controlled D8 Bruker Advance ECO powder diffractometer with filtered Cu Ka radiation. The water contact angles of the fibrous materials were measured using an Easy Drop DSA20E KRUSS GmbH apparatus, Germany. The antibacterial activity of the Curc-containing fibrous materials against Gram-positive S. aureus and Gram-negative E. coli was evaluated by using the viable cell-counting method.
Results
Representative SEM images of the obtained CA and Curc/PVP-on-CA are shown in Figure 1. Electrospinning of CA solutions resulted in preparation of fibers with mean fiber diameter 780 ± 110 nm (Fig, 1A). The mean fiber diameter of Curc-in-CA fibers was 1150 ± 260 nm (Tsekova, 2017). As seen, in Curc/PVP-on-CA mats Curc/PVP particles were deposited on the CA fibers. Formation of Curc/PVP particles was observed on the surface of the mats as well as in their bulk. This finding is evidence that the used concentrations of the Curc/PVP solution are suitable for the formation of separated particles. The average size of the small and large particles in the Curc/PVP-on-CA material was 1060 ± 220 nm and 6070±430 nm, respectively. The microparticles obtained by electrospraying have great potential as carriers for delivery of biologically active substances, for wound dressing applications, etc.
A B
Figure 1. SEM micrographs of fibrous mats from: A. CA mat; and B. Curc/PVP-ow-CA.
X-ray diffraction analysis of CA and Curc/PVP-ow-CA mats and Curc powder recorded in 29 range from 5 to 60° was performed and XRD patterns are shown in Figure 2. The presence of the main diffraction peaks of pure Curc powder located at 29=8.9°, 14.5°, 17.2°, 18.2°, and 23.3° were detected. Characteristic peaks for Curc were absent in the XRD pattern of Curc/PVP-ow-CA mat, thus implying that Curc was in amorphous state.
CA mat
Figure 2. XRD patterns of: CA mat, Curc/PVP-ow-CA mat and Curc powder.
10
20
30 40
2 theta angle (")
50
60
Digital photographs of water droplets deposited on the surface of the mats are presented in Figure 3. It was found that the CA and Curc-z'w-CA mats were hydrophobic with water contact angles 123° and 129.4°, respectively. In contrast, the value of the water contact angle for Curc/PVP-ow-CA mat was much lower ca. 81°. This was attributed to the addition of the water-soluble polymer - PVP and thus higher wettability of the mat was achieved.
A. 123° B. 129.4° C. 81°
Figure 3. Digital photographs of water droplets on the surface of mats: A. CA, B. Curc-iw-CA and
C. Curc/PVP-ow-CA.
Moreover, the antibacterial activity of the fibrous CA, Curc-iw-CA and Curc/PVP-ow-CA mats against the pathogenic microorganisms S. aureus and E. coli was evaluated. The number of survived bacteria was assessed by plating and counting of CFU on solid medium after the contact of fibrous mats with the suspension (Figure not shown). It was found that neat CA mats did not inhibit the growth of bacterial cells and after 24 hours of contact, the number of the cells increased to over 6 logs for S. aureus and to more than 6.5 logs for E. coli. In contrast, a decrease in the number of the viable cells for the exposure time of 2 h was observed for the Curc-containing mats. Moreover, Curc/PVP-ow-CA mat showed the capability to kill all the S. aureus cells within 24 h of contact. On the other hand, Curc was released more slowly from the Curc-iw-CA mat where the phenolic compound was incorporated in the CA fibers. In this case decrease in the viable cell number was observed, however, the antibacterial efficacy was lower (ca. 2 logs).
Conclusion.
Novel fibrous mats based on CA containing biologically active substance - Curc were prepared by conjunction of electrospinning and electrospraying techniques. The Curc/PVP particles were electrosprayed on the CA fibers in order to modulate the wetting of the fibrous materials and to facilitate the dissolution and release of Curc from the obtained mats. Moreover, the Curc-containing mats exhibited antibacterial activity against S. aureus and E. coli.
Acknowledgment.
The authors thank the National Science Fund of Bulgaria for the financial support (Grant number DFNI-T02/1 -2014).
References:
Basnet P., Skalko-Basnet N., Molecules, 16, 4567-4598 (2011).
Boateng J., Matthews K., Stevens H., Eccleston G., J. Pharm. Sci., 97, 2892-2923 (2008). Moghadamtousi S., Kadir H., Hassandarvish P., Tajik H., Abubakar S., Zandi K., Biomed. Res. Iwt., Article ID 186864, 1-12 (2014).
Sarika P., James N., Kumar P., Raj D., Mater. Sci. Ewg. C, 68, 251-257 (2016). Spasova M., Paneva D., Manolova N., Radenkov P., Rashkov I., Macromol. Biosci., 8, 153-162 (2008).
Toncheva A., Spasova M., Paneva D., Manolova N., Rashkov I., Iwt. J. Polym. Mater. Polym. Biomater., 63, 657-671 (2014).
Tsekova P., Spasova M., Manolova N., Markova N., Rashkov I., Mater. Sci. Ewg. C, 73, 206-214 (2017).
*e-mail: [email protected]
