Carbon Dots in Biotechnology and Food Technology: Comparison
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Please note this is a comparison between Version 2 by Jason Zhu and Version 1 by Karen Khachatryan.

Materials with a “nano” structure are increasingly used in medicine and biotechnology as drug delivery systems, bioimaging agents or biosensors in the monitoring of toxic substances, heavy metals and environmental variations. Furthermore, in the food industry, they have found applications as detectors of food adulteration, microbial contamination and even in packaging for monitoring product freshness. Carbon dots (CDs) as materials with broad as well as unprecedented possibilities could revolutionize the economy, if only their synthesis was based on low-cost natural sources. 

  • carbon dots
  • graphene carbon dots
  • carbon quantum dots
  • carbon nanodots

1. Introduction

Research developments leading to increasing control over the synthesis and properties of carbon quantum dots are opening up many new application opportunities for them. The field of their applications is expected to expand further, opening up new prospects for their use in various fields of science and technology. Currently, the greatest potential of carbon dots is seen in sectors related to biotechnology, medicine and the food industry.

2. Applications of Carbon Dots in Biotechnology

The main applications of carbon quantum dots include bioimaging of cellular structures, determining pH and other parameters of the cellular environment, studying the presence and concentration of small-molecule compounds, and monitoring biochemical processes taking place in cells. All of these analyses are feasible on living and apoptotic cells, both in vitro and in vivo [65,66,67][1][2][3]. The main application directions for CDs in biotechnology are shown in Figure 1.
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Figure 1. Main directions of application of CDs in biotechnology.
Selective staining of individual structures found in cells can give insight into their metabolic and proliferative activity, cycle and division phase, and highlight the influence of exogenous factors involved in growth stimulation and regeneration [59][4]. Moreover, with the help of fluorescence microscopy, it is possible to monitor molecular dynamics in real time. This makes it possible to elucidate many hitherto poorly understood phenomena in cell biology related to translocation and interactions between molecules and responses to external stimuli [25][5].
Compounds used in bioimaging should meet several basic criteria. First of all, they must exhibit a lack of cytotoxicity, have high selectivity and fluorescence capabilities. Classical organic dyes are easily degraded, are often prone to photobleaching and, in the case of in vitro studies, can cause contamination of the culture medium. This significantly deteriorates the efficiency of the imaging and detection process [68][6].
Carbon quantum dots, appear to be an excellent solution. They enable the detection of structures and substances with a selectivity unavailable to any other organic molecules, while showing stability, lack of cytotoxic effect and much better biocompatibility compared to metallic quantum dots [59,69][4][7]. It has been shown that the factors that have the greatest influence on the ability of particles to enter cells and accumulate within specific structures are the presence of particular functional groups, electrical charge and degree of hydrophobicity. It therefore follows that by properly selecting the synthesis parameters, it is possible to control which cellular elements will undergo staining. For example, carbon dots obtained by the microwave method will accumulate mainly in the cell membrane and close to the cell nucleus [59,65,70][1][4][8]. There is also a lot of research currently underway on the use of carbon quantum dots in monitoring environmental pH. Changes in pH can significantly affect the color and intensity of their fluorescence. Due to their easy handling, short response time, high sensitivity, and applicability to biological environments, they are of particular interest in areas related to medical and biological sciences [25][5]. Although the mechanism of sensitivity of carbon dots to pH is not fully understood, there are several concepts explaining this relationship. The most widely accepted hypothesis is that base and excited states involve deprotonation or protonation of surface functional groups containing oxygen in their composition. This causes transitions in the energy levels of the particles, which become apparent in changes in their fluorescence. Most carbon dots have pH-sensitive luminescence properties, but depending on the raw materials, method of preparation, structure and morphology, they will respond to changes in different ways [71,72][9][10].

3. Application of Carbon Dots in Food Technology

Food production requires continuous monitoring of the quality of raw materials and the foodstuffs produced from them. At each stage of processing, there is a potential risk of contaminants that can adversely affect product safety. Contaminants can have various sources and include pathogenic microorganisms present in the environment, microbial toxins, heavy metals, biogenic amines, products of the glycosylation process and residues of pesticides and veterinary drugs. The last are a very big problem for meat and grain products [106][11]. Consumption of such contaminated goods may be a serious risk to human health and life. Heavy metals exhibit particularly toxic effects. It is estimated that about 90% of these elements are introduced into the body with food [28,107][12][13]. Some metallic elements, such as lead, chromium and mercury, have devastating effects on health even at low concentrations. Others, which include copper and silver, are not biodegradable and accumulate in internal organs, causing increasingly serious health consequences over time [106][11].
Traditional analytical methods, which include liquid and gas chromatography and mass spectroscopy, are time-consuming, complex, require expensive equipment and skilled personnel. They are therefore unable to meet the needs of effective real-time monitoring of the entire production chain. Therefore, to ensure food safety, there is an urgent need to develop sensitive, accurate, safe and rapid analytical methods. Detection methods based on fluorescence show great potential here. Of all fluorescent materials, carbon dots are the most promising. They provide satisfactory optical properties and high sensitivity, and unlike other quantum dots are characterized by biocompatibility and lack of cytotoxicity. Their low cost of obtaining is also a great advantage, which facilitates their use on a mass scale [106,108,109][11][14][15].
Food safety at every stage of its production is a key aspect of protecting the health and lives of consumers. Physical, chemical as well as biological contamination of food may not only result from direct contamination of food products, but may also pass into it indirectly. Therefore, it is essential to monitor and take care of the quality of the food production at every stage, in line with the ‘farm-to-table’ strategy. This demands an effective method to guarantee food safety [110,111][16][17]. The low toxicity and high sensitivity of CDs makes them suitable for large-scale application. In the food industry, they are applied for the detection and determination of heavy metals, pathogens and additives [112,113,114,115][18][19][20][21]. The main application directions for CDs in food technology are shown in Figure 2.
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Figure 2. Main directions of application of CDs in food technology.
The properties of CDs can be tailored already during the synthesis process, mainly by appropriate functionalization of their surface. Depending on the functional groups present, nanoparticles will show affinity for other types of compounds. Mostly, a given type of carbon dots is particularly selective for one compound and the content of other substances will not affect changes in fluorescence intensity. Other features that can be controlled in the synthesis process are the degradation ability to reduce secondary product contamination by these structures and sensitivity to changes in the concentration of the test compound. Combining nanoparticles with other ligands can also be a good option. Such a treatment can significantly improve their sensitivity to changes in the content of target substances and improve their adsorption capacity [110,116,117,118][16][22][23][24].
Carbon quantum dots can also be used in food preservation. Studies show that they exhibit strong antimicrobial and antioxidant properties, so they can significantly improve product stability and extend shelf life. This is of greatest importance for processed meats, since microbial infections and oxidation processes are the main factors in the loss of quality of these products. Lipid oxidation deteriorates the texture, color and appearance of meat, and secondary products of this process can lead to protein oxidation. This in turn can result in structural changes to these compounds and the formation of toxic substances. However, the antioxidants currently used can negatively affect health and interfere with the original flavor and aroma of the product. CDs are able to assist in combating free radicals while maintaining the sensory value of food items [119,120][25][26].
Carbon dots can also be used as nanofillers in packaging materials. Currently, there is a global search for new plastics that are completely biodegradable and at the same time meet all expectations for their functionality. Most composites composed of biopolymers such as polysaccharides or proteins can exhibit many favorable properties and be completely degradable to carbon dioxide, water and biomass. With these types of materials, however, the problem of poor mechanical and barrier properties often arises. Adding even a small amount of carbon nanoparticles to a polymer film can help overcome these limitations without adversely affecting the food. In addition, such packaging can exhibit properties that classify it as active or smart packaging. Active packaging is capable of reducing the rate of spoilage of food products through increased barrier properties and antimicrobial and antioxidant effects. Smart packaging additionally provides information on biochemical and microbiological changes that have occurred in the food. In the case of films containing carbon quantum dots, the appearance of various compounds providing evidence of product deterioration will induce changes in color and fluorescence intensity [24,121,122][27][28][29]. The possibilities for using carbon dots as a smart and active packaging in food technology are much wider. For example, Da et al. [123][30] analysed the degree of oxidation in bananas and apples using fluorescent coatings on polypropylene film through the photografting mechanism. The quality was evaluated by assessing the number of black spots and areas on the film. Min et al. [124][31] applied carbon dots as a functional filler to prepare a functional film based on gelatine. The resulting films exhibited UV barrier properties and strong antioxidant activity. Carbon dot based sensors are most commonly based on a fluorescence quenching mechanism induced by the surface states of the carbon dots. On this basis, metal ions such as Ag+ [125][32], Fe3+ [126][33], Hg2+ [127][34], Cu2+ [122][29], Ni2+ [128][35] be detected. Ezati et al. [129][36] have devised a method for detecting ammonia and its derivatives using specially prepared carbon dot-containing paper.

References

  1. Espina-Casado, J.; Fontanil, T.; Fernández-González, A.; Cal, S.; Obaya, Á.J.; Díaz-García, M.E.; Badia-Laino, R. Carbon dots as multifunctional platform for intracellular pH sensing and bioimaging. In vitro and in vivo studies. Sens. Actuators B Chem. 2021, 346, 130555.
  2. Pourmadadi, M.; Rahmani, E.; Rajabzadeh-Khosroshahi, M.; Samadi, A.; Behzadmehr, R.; Rahdar, A.; Ferreira, L.F.R. Properties and application of carbon quantum dots (CQDs) in biosensors for disease detection: A comprehensive review. J. Drug Deliv. Sci. Technol. 2023, 80, 104156.
  3. Prakash, A.; Yadav, S.; Yadav, U.; Saxena, P.S.; Srivastava, A. Recent advances on nitrogen-doped carbon quantum dots and their applications in bioimaging: A review. Bull. Mater. Sci. 2023, 46, 7.
  4. Janus, Ł. Synteza i Badanie Właściwości Węglowych Kropek Kwantowych do Zastosowań w Medycynie. Ph.D. Thesis, Politechnika Krakowska, Kraków, Poland, 2022.
  5. Molaei, M.J. A review on nanostructured carbon quantum dots and their applications in biotechnology, sensors, and chemiluminescence. Talanta 2019, 196, 456–478.
  6. Sheikh Mohd Ghazali, S.A.I.; Fatimah, I.; Zamil, Z.N.; Zulkifli, N.N.; Adam, N. Graphene quantum dots: A comprehensive overview. Open Chem. 2023, 21, 20220285.
  7. Iravani, S.; Varma, R.S. Green synthesis, biomedical and biotechnological applications of carbon and graphene quantum dots. A review. Environ. Chem. Lett. 2020, 18, 703–727.
  8. Can, V.; Onat, B.; Cirit, E.S.m.; Sahin, F.; Canbek Ozdil, Z.C. Metal-Enhanced Fluorescent Carbon Quantum Dots via One-Pot Solid State Synthesis for Cell Imaging. ACS Appl. Bio Mater. 2023, 6, 1798–1805.
  9. Liu, C.; Zhang, F.; Hu, J.; Gao, W.; Zhang, M. A mini review on pH-sensitive photoluminescence in carbon nanodots. Front. Chem. 2021, 8, 605028.
  10. Tao, X.; Liao, M.; Wu, F.; Jiang, Y.; Sun, J.; Shi, S. Designing of biomass-derived carbon quantum dots@ polyvinyl alcohol film with excellent fluorescent performance and pH-responsiveness for intelligent detection. Chem. Eng. J. 2022, 443, 136442.
  11. Zhu, X.; Jiang, W.; Zhao, Y.; Liu, H.; Sun, B. Single, dual and multi-emission carbon dots based optosensing for food safety. Trends Food Sci. Technol. 2021, 111, 388–404.
  12. Torres, S.; Bogireddy, N.K.R.; Kaur, I.; Batra, V.; Agarwal, V. Heavy metal ion detection using green precursor derived carbon dots. iScience 2022, 25, 103816.
  13. Mitra, S.; Chakraborty, A.J.; Tareq, A.M.; Emran, T.B.; Nainu, F.; Khusro, A.; Idris, A.M.; Khandaker, M.U.; Osman, H.; Alhumaydhi, F.A. Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. J. King Saud Univ.-Sci. 2022, 34, 101865.
  14. Li, T.; Li, Z.; Huang, T.; Tian, L. Carbon quantum dot-based sensors for food safety. Sens. Actuators A Phys. 2021, 331, 113003.
  15. Sobiech, M.; Luliński, P.; Wieczorek, P.P.; Marć, M. Quantum and carbon dots conjugated molecularly imprinted polymers as advanced nanomaterials for selective recognition of analytes in environmental, food and biomedical applications. TrAC Trends Anal. Chem. 2021, 142, 116306.
  16. Shi, X.; Wei, W.; Fu, Z.; Gao, W.; Zhang, C.; Zhao, Q.; Deng, F.; Lu, X. Review on carbon dots in food safety applications. Talanta 2019, 194, 809–821.
  17. Luo, X.; Han, Y.; Chen, X.; Tang, W.; Yue, T.; Li, Z. Carbon dots derived fluorescent nanosensors as versatile tools for food quality and safety assessment: A review. Trends Food Sci. Technol. 2020, 95, 149–161.
  18. Fan, H.; Zhang, M.; Bhandari, B.; Yang, C.-H. Food waste as a carbon source in carbon quantum dots technology and their applications in food safety detection. Trends Food Sci. Technol. 2020, 95, 86–96.
  19. Zheng, L.; Qi, P.; Zhang, D. Identification of bacteria by a fluorescence sensor array based on three kinds of receptors functionalized carbon dots. Sens. Actuators B Chem. 2019, 286, 206–213.
  20. Sharifi, S.; Vahed, S.Z.; Ahmadian, E.; Dizaj, S.M.; Eftekhari, A.; Khalilov, R.; Ahmadi, M.; Hamidi-Asl, E.; Labib, M. Detection of pathogenic bacteria via nanomaterials-modified aptasensors. Biosens. Bioelectron. 2020, 150, 111933.
  21. Yue, X.-Y.; Zhou, Z.-J.; Wu, Y.-M.; Li, Y.; Li, J.-C.; Bai, Y.-H.; Wang, J.-L. Application Progress of Fluorescent Carbon Quantum Dots in Food Analysis. Chin. J. Anal. Chem. 2020, 48, 1288–1296.
  22. Ansari, S.; Masoum, S. Recent advances and future trends on molecularly imprinted polymer-based fluorescence sensors with luminescent carbon dots. Talanta 2021, 223, 121411.
  23. Han, A.; Hao, S.; Yang, Y.; Li, X.; Luo, X.; Fang, G.; Liu, J.; Wang, S. Perspective on recent developments of nanomaterial based fluorescent sensors: Applications in safety and quality control of food and beverages. J. Food Drug Anal. 2020, 28, 486.
  24. Wang, H.; Liu, S.; Song, Y.; Zhu, B.-W.; Tan, M. Universal existence of fluorescent carbon dots in beer and assessment of their potential toxicity. Nanotoxicology 2019, 13, 160–173.
  25. Zhao, L.; Zhang, M.; Bhandari, B.; Bai, B. Microbial and quality improvement of boiled gansi dish using carbon dots combined with radio frequency treatment. Int. J. Food Microbiol. 2020, 334, 108835.
  26. Zhao, L.; Zhang, M.; Wang, H.; Devahastin, S. Effect of addition of carbon dots to the frying oils on oxidative stabilities and quality changes of fried meatballs during refrigerated storage. Meat Sci. 2022, 185, 108715.
  27. Kumar, L.; Gaikwad, K.K. Carbon dots for food packaging applications. Sustain. Food Technol. 2023, 1, 185–199.
  28. Moradi, M.; Molaei, R.; Kousheh, S.A.; Guimarães, J.T.; McClements, D.J. Carbon dots synthesized from microorganisms and food by-products: Active and smart food packaging applications. Crit. Rev. Food Sci. Nutr. 2023, 63, 1943–1959.
  29. Wu, J.; Chen, X.; Zhang, Z.; Zhang, J. “Off-on” fluorescence probe based on green emissive carbon dots for the determination of Cu2+ ions and glyphosate and development of a smart sensing film for vegetable packaging. Microchim. Acta 2022, 189, 131.
  30. Das, P.; Ganguly, S.; Margel, S.; Gedanken, A. Immobilization of heteroatom-doped carbon dots onto nonpolar plastics for antifogging, antioxidant, and food monitoring applications. Langmuir 2021, 37, 3508–3520.
  31. Min, S.; Ezati, P.; Rhim, J.-W. Gelatin-based packaging material incorporated with potato skins carbon dots as functional filler. Ind. Crops Prod. 2022, 181, 114820.
  32. Cayuela, A.; Soriano, M.L.; Kennedy, S.R.; Steed, J.; Valcárcel, M. Fluorescent carbon quantum dot hydrogels for direct determination of silver ions. Talanta 2016, 151, 100–105.
  33. Lai, T.; Zheng, E.; Chen, L.; Wang, X.; Kong, L.; You, C.; Ruan, Y.; Weng, X. Hybrid carbon source for producing nitrogen-doped polymer nanodots: One-pot hydrothermal synthesis, fluorescence enhancement and highly selective detection of Fe (III). Nanoscale 2013, 5, 8015–8021.
  34. Zhang, R.; Chen, W. Nitrogen-doped carbon quantum dots: Facile synthesis and application as a “turn-off” fluorescent probe for detection of Hg2+ ions. Biosens. Bioelectron. 2014, 55, 83–90.
  35. Li, Y.; Liu, C.; Chen, M.; An, Y.; Zheng, Y.; Tian, H.; Shi, R.; He, X.; Lin, X. Solvent-free preparation of tannic acid carbon dots for selective detection of Ni2+ in the Environment. Int. J. Mol. Sci. 2022, 23, 6681.
  36. Ezati, P.; Khan, A.; Rhim, J.-W.; Kim, J.T.; Molaei, R. pH-Responsive strips integrated with resazurin and carbon dots for monitoring shrimp freshness. Colloids Surf. B Biointerfaces 2023, 221, 113013.
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