Antioxidant-Rich Black Rice

Development of Antioxidant Black Rice Polyurethane Biocomposite for Food Packaging and Wound Healing Applications Wound dressings are medical textile products that assist in rapid healing of wounds under medically appropriate conditions and environments (Ersoy et al., 2015). Medical (biomedical) textiles, also called Medtech textile materials, have shown rapid development in the textile industry in recent years. Medical textiles are textile materials produced or designed for medical applications. Materials such as surgical threads, wound dressings, gauze bandages, bandages, and artificial organs are among medical textile products (Doğan and Başal, 2009). Medical textiles are textile materials commonly designed for use in all fields of medicine and surgery. Medical textiles should demonstrate biological compatibility with surrounding tissue and show compatibility with various materials. Depending on the field of application, the general properties required from medical textiles can be listed as: strength, antitoxic properties, elasticity, antiallergic properties, durability, and biocompatibility. Biomedical materials can become contaminated with bacteria, and at this point, sterilization of biomedical materials is one of the very important and carefully considered factors (Al-sherbini et al., 2015). Antioxidants have become one of the important topics in human nutrition in recent years. This is due to their ability to eliminate free radicals. Additionally, synthetic and natural antioxidants are used to process foods to prevent their decomposition over long periods. While these antioxidants protect food, they simultaneously exhibit protective properties against substances that cause food oxidation (Yavaşer, 2011). Antioxidants strengthen the body's immune system and have properties such as delaying aging. Black rice is a food source with high antioxidant value. Black rice derives its aroma from acetyl pyrrole, while its color comes from anthocyanin, cyanidin, and 3-O-beta glucoside (Shao et al., 2018). PU is a copolymer containing urethane groups in its structure (Yeganeh and Hojati-Talemi, 2007). Good physical and mechanical properties and biocompatibility provide a wide range of applications (Gültekin, 2006). With these properties, it is also used as a wound dressing material. Wound dressing prevents the risk of water loss on the wound surface and facilitates epidermal cell migration (Zlatanic et al., 2004). Figure 1 shows the linear PU structure.

Figure 1. Linear PU structure (Zlatanic et al., 2004)

In this study, materials that could exhibit food packaging product and wound healing tape properties were produced from PU-Black rice biocomposites using the electrospinning method. Characterization studies of nanostructured composites were performed using structural (FTIR), morphological (FEGSEM), thermal (DSC), and mechanical (tensile) analysis/testing. The prepared black rice-reinforced PU nanofiber structures are expected to have significant potential as packaging products mainly in the food sector and as wound healing tape materials in tissue engineering.

2. Materials and Method

2.1 Materials Used

Black rice was obtained from a local market in Istanbul. In biocomposite production, PU (Lubrizol advanced material inc. Cleveland United States) and organic solvents such as Dimethylformamide (DMF-HCON(OH3)2) (Sigma-Aldrich/Turkey) and Ethyl Acetate (C4H8O2) (Sigma-Aldrich/Turkey) were used to dissolve polymers. During the electrospinning stage, greaseproof paper was used as the substrate material in biocomposite production.

2.2 Production of Black Rice-Reinforced PU Nanofibers

via Electrospinning Method

PU and black rice-reinforced PU nanofibers at 1%, 5%, and 8% were dissolved in a DMF/Ethyl acetate solvent system mixed at a volume ratio of 80/20 for 2 hours at 40°C, and then prepared for the nanofiber production process via the electrospinning method. The nanofiber production process was provided from 14% PU and 14% PU matrix reinforced with 1%, 5%, and 8% black rice solutions. The parameter values listed in Table 1 were used as the basis in the production process. Table 1 shows the parameter values applied to the electrospinning solutions. Figure 2 shows the biocomposite product production stages.

Table 1. Biocomposite production parameters via electrospinning method (Bozkurt et al., 2017)

Figure 2. Production of black rice-reinforced PU nanofibers via electrospinning method

2.3 Characterization Studies

Structural analysis of the produced biocomposites was performed using a Jasco 6600 FTIR instrument at wavelength ranges of 400-4000 cm-1, and functional groups present in the sample structures were identified based on percent transmittance (%T) values. Morphological analysis was performed by taking high-resolution nanofiber images using a Quanta FEG 450 FEGSEM instrument, and the average diameter thicknesses of these nanofibers were measured using Image j (2011) software. Thermal analysis was performed on 10 mg weighed biocomposite samples using a Hitachi 7000X instrument with DSC analysis in 3 steps at a heating rate of 10°C/min in the temperature range of -50-140°C. Mechanical analysis was performed according to ASTM standards; samples cut to 1x5 cm dimensions had their thicknesses measured with an OKR brand micrometer, and mechanical properties were determined using a Zwickline test instrument set at a 500 N load, 5 mm/minute tensile speed, and 10 mm jaw spacing. In the test process, three replicates were performed from four different samples and average values were used as the basis.

3. Discussion

3.1 FTIR Analysis

When evaluating the PU structure spectrum, the N-H stretch band was found at 3325 cm-1, the CH2 stretch band at 2956 cm-1, and the C=O absorption bands at 1701 and 1727 cm-1. The C-C stretch bands in the benzene ring were found at frequency values of 1464 cm-1 and 1597 cm-1, the N-H and C-N bonds in the amide group at wavelength 1527 cm-1, and the C-O-C stretch bands at wavelengths 916 cm-1 and 1100 cm-1 (Chiono et al., 2014). Black rice particles reduced the wavelength intensity of the functional groups present in the PU structure while also slightly shifting the stretch band values. In the 14% PU-8% black rice biocomposite structure, overlapping of the functional groups of PU and black rice particles was observed, and this was determined to support biocomposite formation from these structures. Figure 3 shows the FTIR spectrum of the PU-Black rice biocomposite.

Figure 3. FTIR spectrum of PU-Black rice biocomposite

3.2 FEGSEM Analysis

It was determined that black rice particles reinforced in the polymeric matrix reduced agglomeration formation with increasing concentration amount. As the concentration ratio of reinforced black rice particles increased, black rice particles were observed to coat uniformly on the fibers. Additionally, it was determined that nanofiber distribution changes depending on flow rate, voltage, distance between the collector plate and feeding needle, and collector plate rotation speed during the electrospinning stage. From the FEGSEM images, it was determined that the fiber structures of samples with increasing concentration amounts took on a uniform shape and the fibers became thinner without showing agglomeration (Tijing et al., 2012; Bozkurt et al., 2017). The nanofiber diameters from the FEGSEM images in Figure 4 were measured using Image j (2011) software. Nanofiber diameters became thinner with increasing concentration of black rice particles. Image j (2011) software revealed that nanofiber diameters were 30-350 nm. Approximately 50 nanofiber structures had their diameters measured and average diameter values were used as the basis. Figure 4 shows the FEGSEM images of PU-Black rice biocomposites.

Figure 4. FEGSEM images of PU-Black rice biocomposites

3.3 DSC Analysis

When examining the thermal analysis results of the PU-Black rice biocomposite, compared to pure PU polymer, an increase in glass transition temperature (Tg) and melting point (Tm) was observed in black rice-reinforced biocomposites with increasing black rice concentration. High thermal property biocomposites were obtained for use as food packaging and wound healing products (Anandhan and Lee, 2014). Figure 5 shows the DSC analysis results of PU-Black rice biocomposites.

Figure 5. DSC analysis values of PU-Black rice biocomposites

3.4 Tensile Analysis

It was observed that with increasing concentration percentages of black rice particles reinforced in the PU matrix, the strength value increased linearly. As can be understood from the FEGSEM images obtained as a result of morphological examination, black rice particles coat uniformly on polymer fibers and agglomeration formation was not observed, which is consistent with our results in mechanical properties showing an increase for these biocomposites. Biocomposites with strength exceeding mechanical results found in comparable studies in the literature were produced. The strength value obtained in the 14% PU-8% Black rice sample was determined to be the highest value obtained in our study. This increase in strength was concluded to result from both the polymeric matrix with high load-bearing capacity, the reinforcement of black rice particles, and the uniform distribution in the biocomposite (Bozkurt et al., 2017). Figure 6 shows the tensile test value graph of PU-Black rice biocomposites.

Figure 6. Tensile test values of PU-Black rice biocomposites

4. Conclusion

When the study results were evaluated, biocompatible and biodegradable food packaging products and wound dressing tape were successfully produced from black rice-reinforced PU matrix materials. The functional groups determined as a result of FTIR analysis and the properties of black rice and PU substances were determined to be contained in the PU-Black rice biocomposite structure. As a result of FEGSEM analyses, the fiber sizes of PU and PU-Black rice nanofibers were measured using Image J (2011) software and determined to be 30-350 nm. The fact that these fine fibers were not broken, with black rice particles uniformly wrapping PU fibers, resulted in the observation that nanofiber diameters became thinner. When mechanical tests were applied to the produced biocomposites, the PU-8% Black rice biocomposite achieved the highest test value compared to other samples. In continuation of this study, conducting tests such as antioxidant and cell culture on biocomposite samples could provide direction to studies planned to be conducted in later stages.

Acknowledgement

We thank the Istanbul Arel University ArelPOTKAM (Polymer Technologies and Composite Application and Research Center) team for their assistance in biocomposite production and characterization studies, and the management and staff of Zwick-Roell company for their assistance in mechanical analysis studies of the biocomposites.

• References

  ERSOY, Y., DURAN, M., & TAYYAR, A. E. (2015). Medical Textiles and Wound Dressing. Düzce University Journal of Science and Technology, 3(2).

  DOĞAN, G., & BAŞAL, G. (2009). Applications of biopolymer nanofibers obtained by electrospinning method as drug delivery systems, wound dressings and tissue scaffolds. Textile Technology Electronic Journal, 3(2), 58-70.

  AL-SHERBINI, A., RAGAB, S. S., & EL-SAYED, H. H. (2015). Antimicrobial Effects of Silver Nanoparticles Mediated Cosmetic Cream and Cotton Gauze on Candida Strains. Journal of Pharmacy and Biological Science, 10(3), 69-75.

  YAVAŞER, R. (2011). Comparison of antioxidant capacity of natural and synthetic antioxidant compounds, Master's Thesis, Adnan Menderes University, Institute of Science, Aydın.

  SHAO, Y., Hu, Z., YU, Y., MOU, R., ZHU, Z., & BETA, T. (2018). Phenolic acids, anthocyanins, proanthocyanidins, antioxidant activity, minerals and their correlations in non-pigmented, red, and black rice. Food Chemistry, 239, 733-741.

  YEGANEH, H., & HOJATI-TALEMI, P. (2007). Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly (ethylene glycol). Polymer Degradation and Stability, 92(3), 480-489.

  GÜLTEKİN, G. (2006). Production of fatty acid-based polyurethane films for wound dressing material applications, Master's Thesis, Istanbul Technical University Institute of Science, Istanbul.

  ZLATANIĆ, A., LAVA, C., ZHANG, W., & PETROVIĆ, Z. S. (2004). Effect of structure on properties of polyols and polyurethanes based on different vegetable oils. Journal of Polymer Science Part B: Polymer Physics, 42(5), 809-819.

  BOZKURT, Y., SAHIN, A., SUNULU, A., AYDOGDU, M. O., ALTUN, E., OKTAR, F. N., ... & GUNDUZ, O. (2017). Electrospun Nanocomposite Materials, A Novel Synergy of Polyurethane and Bovine Derived Hydroxyapatite. In Journal of Physics: Conference Series (Vol. 829, No. 1, p. 012015). IOP Publishing.

  CHIONO, V., MOZETIC, P., BOFFITO, M., SARTORI, S., GIOFFREDI, E., SILVESTRI, A., ... & DI MEGLIO, F. (2014). Polyurethane-based scaffolds for myocardial tissue engineering. Interface Focus, 4(1), 20130045.

  TIJING, L. D., RUELO, M. T. G., AMARJARGAL, A., PANT, H. R., PARK, C. H., KIM, D. W., & KIM, C. S. (2012). Antibacterial and superhydrophilic electrospun polyurethane nanocomposite fibers containing tourmaline nanoparticles. Chemical Engineering Journal, 197, 41-48.

  ANANDHAN, S., & LEE, H. S. (2014). Influence of organically modified clay mineral on domain structure and properties of segmented thermoplastic polyurethane elastomer. Journal of Elastomers & Plastics, 46(3), 217-232.

Dr. Asst. Prof. Yeşim Müge Şahin Center Director Istanbul Arel University - ArelPOTKAM Erdi Buluş Materials and Metallurgical Engineer Material Technologies Specialist Istanbul Arel University ArelPOTKAM