Alaş Melis Özge, Doğan Gamze, Yalcin Mustafa Serkan, Ozdemir Sadin, Genç Rükan
Department of Chemical Engineering, Engineering Faculty, Mersin University, Mersin TR-33343, Turkey.
Faculty of Engineering Department of Bioengineering, Izmir Institute of Technology, Urla-Izmir TR-35430, Turkey.
ACS Omega. 2022 Aug 22;7(34):29967-29983. doi: 10.1021/acsomega.2c02984. eCollection 2022 Aug 30.
Active food packaging has become attractive because of the possibility to provide a longer shelf-life by loading functional agents into the packages to maintain the quality of food products. Herein, photoluminescent and transparent polyvinyl alcohol (PVA)-based composites embedding multicolor fluorescent carbon dots (CD/PVA) were prepared by the solvent casting method. The prepared CDs emit a strong and stable fluorescence in solution while the CD/PVA composite films were transparent, flexible, and showed UV-blocking activity with a strong fluorescence emission. Blue color-emitting CDs showed the highest UV blockage at UVA (87.04%), UVB (87.04%), and UVC (92.22%) regions while PVA alone absorbed only less than 25% of the light in all UV regions. UV blockage capacity was shown to be decreased by half, in line with the emission color shift from blue to red. Thermal properties of the PVA film were improved by the addition of CDs to the polymer, and in vitro cell viability tests showed that none of the CDs were cytotoxic against the human lung fibroblast healthy cell line (MRC-F cells) when integrated into the PVA. The antimicrobial activity of CD/PVA nanofilms was qualitatively determined. The prepared films exhibited good antimicrobial activity against both Gram-positive and Gram-negative bacteria with mild antioxidant and metal chelating activity, and significant inhibition of biofilm formation with a strong link with emitted color and the concentration of the composites. Green- and red-emitting CD/PVA with the highest antimicrobial activity were then analyzed and compared with the plane PVA employing their effect on the shelf-life of strawberries as a model for perishable foods. Fresh strawberries dip coated with CD/PVA and PVA were monitored over time, and virtual evaluations showed that CDs/PVA film coating resulted in reduced weight and moisture loss and significantly inhibited the fungal growth and spoiling for over 6 days at RT and 12 days at fridge conditions maintaining the visual appearance and natural color of the fruit. The findings in this work indicated the potential of reported CD as non-cytotoxic, UV-blocking antimicrobial additives for the development of edible coatings and packages for their use in the food industry, as well as pharmaceutical and healthcare applications.
活性食品包装因其能够通过在包装中负载功能剂来延长食品保质期、保持食品质量而备受关注。在此，通过溶液浇铸法制备了嵌入多色荧光碳点的光致发光透明聚乙烯醇（PVA）基复合材料（CD/PVA）。制备的碳点在溶液中发出强烈且稳定的荧光，而CD/PVA复合薄膜是透明、柔性的，并且具有紫外线阻挡活性以及强烈的荧光发射。发射蓝光的碳点在UVA（87.04%）、UVB（87.04%）和UVC（92.22%）区域表现出最高的紫外线阻挡率，而单独的PVA在所有紫外线区域仅吸收不到25%的光。随着发射颜色从蓝色变为红色，紫外线阻挡能力降低了一半。通过向聚合物中添加碳点，PVA薄膜的热性能得到改善，体外细胞活力测试表明，当碳点整合到PVA中时，它们对人肺成纤维细胞健康细胞系（MRC-F细胞）均无细胞毒性。定性测定了CD/PVA纳米薄膜的抗菌活性。制备的薄膜对革兰氏阳性菌和革兰氏阴性菌均表现出良好的抗菌活性，具有温和的抗氧化和金属螯合活性，并且对生物膜形成有显著抑制作用，这与发射颜色和复合材料浓度密切相关。然后对具有最高抗菌活性的绿色和红色发射CD/PVA进行分析，并与平面PVA进行比较，以它们对草莓保质期的影响作为易腐食品的模型。对用CD/PVA和PVA浸涂的新鲜草莓进行了长期监测，实际评估表明，CDs/PVA薄膜涂层导致重量和水分损失减少，并在室温下显著抑制真菌生长和腐败超过6天，在冷藏条件下抑制12天，同时保持了水果的外观和天然颜色。这项工作的研究结果表明，所报道的碳点作为无细胞毒性、紫外线阻挡抗菌添加剂，在开发用于食品工业以及制药和医疗保健应用的可食用涂层和包装方面具有潜力。
