Source: UNIVERSITY OF GEORGIA submitted to
BEHAVIOR OF NANOBIOMATERIALS IN THE GASTROINTESTINAL TRACT AND THEIR RISK ASSESSMENT
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
EXTENDED
Funding Source
Reporting Frequency
Annual
Accession No.
1009090
Grant No.
2016-67021-24994
Project No.
GEOW-2015-07812
Proposal No.
2015-07812
Multistate No.
(N/A)
Program Code
A1511
Project Start Date
Mar 1, 2016
Project End Date
Feb 28, 2021
Grant Year
2016
Project Director
Kong, F.
Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
Food Science & Technology
Non Technical Summary
Biomaterials of agricultural and forest origins usually consist of organic components such as polysaccharides, proteins, peptides, or other biopolymeric materials. Macroscale or microscale biomaterials are generally recognized as safe (GRAS) and do not pose health risks to consumers. However, the biological effects and toxicity of nanoscale biomaterials cannot be predicted solely from their chemical structures. There are many factors that may affect the interaction of nanoscale biomaterials with cells and living organisms, including the size, shape, aggregation status, degree of branching, surface properties, and hybrid materials. A particular concern is the safety of hybrid nanomaterials and nanocomposites, such as nanocellulose impregnated with antimicrobial agents including nanosize metal particles, that may pose risks to humans, livestock, and the environment. So far,Little is known about the behavior and the potential side effects of nanobiomaterials as they travel through the GI tract, and how nanobiomaterials may translocate across the cell membrane.To understand the fate and behavior of nanobiomaterials in GI tract, it is critical to have a suitable and robust analytical methodology for detection and characterization of nanobiomaterials. Over the last five years, we have been working on detection and characterization of engineered nanoparticles in food matrices. Because no single technique can address this need and provide all the necessary information, we developed a combination of methods that are sensitive enough for the measurement of low concentrations of nanoparticles in food, can observe the state of aggregation, dispersion, size, structure, shape of nanoparticles and other measurable properties, and are suitable for both liquid and solid food matrices. We have also conducted preliminary trials in the behavior of nanocellulose in the food matrix during digestion. Dynamic stomach and intestinal models were developed providing realistic simulation of physiological conditions in GI tract. This work has built a solid foundation for this project. We hereby propose to examine how nanobiomaterials behave after ingestion, their interaction with food components, the impact on natural gut microflora and the toxicological effect, using both in vitro and in vivo methods.This project will fill the knowledge gap about the behavior of nanocellulose and hybrid nanomaterials during digestion and their toxicity effects.
Animal Health Component
15%
Research Effort Categories
Basic
100%
Applied
0%
Developmental
0%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
8043999115030%
5110650101040%
1025299201030%
Goals / Objectives
Nanobiomaterials, such as cellulose nanofibers (CNF) and CNF-based antimicrobial agents, may enter the gastrointestinal (GI) tract as a food ingredient or through ingestion of food contaminated by packaging materials containing nanomaterials. However, little is known about the behavior and the potential side effects of nanobiomaterials as they travel through the GI tract, including their particle size, interaction with food components and enzymes, and their impact on gut microflora and toxicological effect.The goal of the proposed project is to understand the behavior of nanobiomaterials in the GI tract and their potential toxicological effects. Specific objectives include 1) Develop methodologies to characterize nanocellulose and their nanocomposites by using a combination of suitable detection and characterization techniques and strategies; 2) Determine the particle size of nanobiomaterials in the GI tract, their interaction with food components and enzymes, and the impact on nutrient digestibility; and 3) Investigate the potential toxicity of nanocellulose and nanocomposites and their effects on natural gut microflora and human cells, and their trans-locational behavior in intestinal cell membranes.Both in vitro and in vivo methods will be used for the proposed study. Novel artificial stomach and intestinal systems will be used to investigate the transit and transformation of nanobiomaterials in the GI tract, and their impact on food digestibility. Animal studies using mice will be conducted to examine the toxicological effect and nutrient digestibility as affected by nanobiomaterials. The results from this study will lead to better understanding of nanobiomaterials for better utilization of those novel materials.
Project Methods
Both in vitro and in vivo methods will be used for the proposed study. Novel artificial stomach and intestinal systems will be used to investigate the transit and transformation of nanobiomaterials in the GI tract, and their impact on food digestibility. Animal studies using mice will be conducted to examine the toxic effect andnutrient digestibility as affected by nanobiomaterials. The interaction of CNF with macronutrients and minerals, and the inhibitory effect on enzymes will be examined. This project will fill the knowledge gap about the behavior of nanocellulose and hybrid nanomaterials during digestion and their toxicity effects.In these experiments, each will be repeated at least one time. Significant differences within and between groups in multi-group experiments will be evaluated using ANOVA for repeated measures with Dunn and/or Holm-Sidak post hoc test. A value of p < 0.05 will be considered statistically significant.

Progress 03/01/19 to 02/29/20

Outputs
Target Audience:The primary target audience for this project includes nanomaterial manufacturers, food companies, governments, regulatory agencies, researchers and scientists seeking to understand the behavior of nanobiomaterials in the gastrointestinal tract and their health implications. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?University of Georgia: three Ph.D. students worked on experimental design and implementation, and data analysis, and writing reports. They also attended IFTannual conference (2019).University of Missouri: two doctoral students and one Master's student wereinvolved in this project. How have the results been disseminated to communities of interest?The results of this project have been disseminated in peer-reviewed journals, at the professional conferences including IFT and IAFP conferences. What do you plan to do during the next reporting period to accomplish the goals?We will continue to study the healthimpact of nanocellulose ingestion using cell models andmice models.

Impacts
What was accomplished under these goals? We determined the effects of subchronic oral CNF consumption on various health aspects of Western diets (WD)-fed mice. The results demonstrated that CNF decreased fat absorption in the jejunum and attenuated WD-induced fatty liver, but slightly decreased lean body mass and affected glucose homeostasis. Additionalin vivostudies showed that CNF decreased the intestinal absorption. Thein vitrostudies suggested that CNF did not decrease the viability of any cells used; however, they prevented epithelial and T cells, but not macrophages, from accessing the viability dye. Taken together, CNF decreased the intestinal absorption non-specifically, which might lead to nutritional risks after long-term exposure. We also studiedthe effects of CNF, CNC, and Tempo-CNF onin vitromilk digestion and mineral adsorption. The effects of anionic NC (TEMPO-CNF and CNC) onin vitrostarch digestion and glucose diffusion were also investigated. Results show that TEMPO-CNF and CNC at high concentrations caused significant reductions in glucose diffusion, especially at 0.36% (w/w) TEMPO-CNF and 2-4% (w/w) CNC. In addition, CNF and TEMPO-CNF at 0.30% (w/w) significantly reduced the amount of free fatty acid produced during intestinal digestion of milk fat. CNC at a concentration of 0.3% (w/w) delayed diffusion of free amino nitrogen during intestinal digestion of milk protein. All three types of NC adsorbed significant amount of Fe, and CNC adsorbed significant amount of Zn, while no significant adsorption was observed on other minerals (Ca, Mg, Zn, Cu and Ag). Results from this study suggest that all three types of NC, when incorporated in food or supplements as zero-calorie fiber, may affect food digestion and nutrient absorption. We also developed novel multifunctional soy protein-based packaging materials with the incorporation of cellulose nanofibril (CNF), Cedrus deodara pine needle extract (PNE), and lactic acid. The effects of the loaded components on the physical and functional properties of nanocomposites were evaluated. Results indicate that the incorporation of CNF into the composite enhanced its tensile strength due to the filling effects of CNF. The addition of CNF and PNE greatly enhanced the light barrier property of films. Moreover, the films containing PNE displayed strong antioxidant activity and significantly improved antimicrobial effects on foodborne pathogens (Escherichia coli O157:H7, Staphylococcus aureus, Salmonella Typhimurium, and Listeria monocytogenes). The incorporation of CNF modified the antimicrobial performance of composite films by mitigating the release of PNE and lactic acid from the film matrix. These results demonstrate that as-prepared nanocomposites possess excellent antioxidant, antimicrobial, and light barrier capacities, which gives them great potential to be used as an active biodegradable food packaging material.

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Liu L, Kong F. 2019. In vitro investigation of the influence of nano-cellulose on starch and milk digestion and mineral adsorption. International Journal of Biological Macromolecules. 137: 1278-85.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Liu L, Kerr WL, Kong F. 2019. Characterization of lipid emulsions during in vitro digestion in the presence of three types of nanocellulose. Journal of Colloid and Interface Science. 545: 317-29.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Liu L, Kong F. 2019. In vitro investigation of the influence of nano-fibrillated cellulose on lipid digestion and absorption. International Journal of Biological Macromolecules. 139: 361-6.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Chen Y, Lin YJ, Nagy T, Kong F, & Guo TL. 2020. Subchronic exposure to cellulose nanofibrils induces nutritional risk by non-specifically reducing the intestinal absorption. Carbohydrate Polymers. 229:115536. p. 1-11.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Yu, Z., Wang, W., Kong, F., Lin, M.*, Mustapha, A.* 2019. Cellulose nanofibril/silver nanoparticle composite as an active food packaging system and its toxicity to human colon cells. Int. J. Biol. Macromol. 129, 887-894
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Yu, Z., Dhital, R., Wang, W., Sun, L., Zeng, W., Mustapha, A.*, Lin, M.* 2019. Development of multifunctional nanocomposites containing cellulose nanofibrils and soy proteins as food packaging material. Food Packag. Shelf Life. 21, 100366.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Liu L, Kong F. Characterization of lipid emulsions during in vitro digestion in the presence of three types of nanocellulose. IFT annual meeting. New Orleans, LA. June 2 - 5, 2019.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Liu L, Kong F. Influence of nanocellulose on in vitro digestion of whey protein isolate. IFT annual meeting. New Orleans, LA. June 2 - 5, 2019.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Lin YJ, Chen Y, Guo T, Kong F. Sub-chronic effect of nanocellulose on small intestine in vivo. The Institute of Food Technologists (IFT) annual meeting. New Orleans, LA. June 2 - 5, 2019
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Kong F. In vitro investigation of the behavior of nanocellulose in human gastrointestinal tract and the influence on food digestion. 13th International Congress on Engineering and Food (ICEF). Melbourne, Australia. September 20-23. 2019.


Progress 03/01/18 to 02/28/19

Outputs
Target Audience:The primary target audience for this project includes nanomaterial manufacturers, food companies, governments,regulatory agencies, researchers and scientists seeking to understand the behavior of nanobiomaterials in thegastrointestinal tract and their health implications. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?University of Georgia: two graduate students were involved in this project under the supervision of Dr. Kong. They worked on experimental design and implementation, and data analysis, and writing reports. They also attended IFTannual conference (2018). One graduate student worked on animal studies using mice under the supervision of Dr. Guo.University of Missouri: three Graduate students were involved in this project under the supervision of Dr. Lin. Through theproject, we built up close collaboration with USDA and the private sector. Dr. Jo Anne Shatkin, President of Vireo Advisors, LLC,served on the advisory committee for one graduate student. How have the results been disseminated to communities of interest?The results have been disseminated to the community through journal publications, and conference presentations. What do you plan to do during the next reporting period to accomplish the goals?We will continue to the study impact of nanocellulose on digestion of lipid emulsions and proteins, as well as the bioavailability of minerals. We will conduct in vivo trials tostudy the toxicological effect and the impact on animal growth.

Impacts
What was accomplished under these goals? In the reporting period, we studiedthe behavior of three types of nanocellulose and its influence on lipid emulsions during digestion.The changes in physicochemical characteristics (including particle size,microstructure, viscosity, and zeta potential) of the emulsions as well as the amount of freefatty acidreleased were studied and compared among the addition of different types/concentrations of fiber as well as digestion phases. We found the colloidal stability of three types of NC differed during each digestion phase. Specifically,cellulosenanocrystals(CNC) formedhydrogelnetworks during the gastric phase, resulting in increased digesta viscosity. Cellulose nano-fibrils (CNF) were stable and had no morphological changes during digestion. TEMPO-oxidized cellulose nano-fibrils (TEMPO-CNF) de-swelled and showed aggregation at the gastric phase. Results showed that all three types of nanocellulose at high concentrations (1% CNF, 0.25-0.36% TEMPO-CNF or 2-3% CNC) delayed initialin vitrodigestion of emulsions, though the final lipolysis extent was nearly the same amongst all (47-55%). In another study,a simulated digestion model, consisting of salivary, gastric and intestinal digestion phases, was used to investigate the effects of NFC on lipid digestion and absorption. To better understand the mechanisms behind, the effects of NFC on lipase activity, micellar solubility of cholesterol and bile acid diffusion were studied in addition to the cholesterol adsorption capacity of NFC, with conventional cellulose as a comparison. Results showed that NFC slightly reduced lipase activity, but NFC or cellulose at concentrations up to 1.1% (w/w) did not significantly influence lipid digestion under simulated intestinal conditions. Moreover, NFC showed greater bile acid retardation effect than cellulose, and slightly higher cholesterol adsorption capacity probably due to its larger specific surface area. Nonetheless, NFC did not significantly affect micellar solubility of cholesterol. These results suggest that NFC, when added into fat-rich foods, may have health benefitsviaits viscosity effect and retardation effect on bile acid absorption. We also synthesized a novel antimicrobial cellulose nanofibril/silver nanoparticle (CNF/AgNP) nanocomposite by an ultraviolet irradiation method and evaluate the toxicity of the nanocomposite to human colon cells. AgNPs coated on CNFs have an average size of ~28 nm and exhibited a surface plasma resonance absorption peak at 402 nm. Coating AgNPs on CNFs interfered with the formation of intra-chain and inter-chain hydrogen bonds of cellulose. Moreover, the CNF/AgNP nanocomposite exhibited significant antimicrobial activities against Escherichia coli O157:H7 by inhibiting DNA replication and damaging cell wall. The nanocomposite also inhibited the growth of Staphylococcus aureus by disrupting cellular functions with the AgNPs attached to cell surfaces and penetrating the cell membrane. No apparent toxicity of the nanocomposite was observed except a high content of CNF/AgNP nanocomposite (≥500 μg/mL) was used to treat Caco-2 and FHC human colon cells in which a significant decrease of cell viability was observed. The toxicity was related to the content, size, and surface charge of UV-synthesized AgNPs on CNFs. These results indicate that the antimicrobial CNF/AgNP nanocomposite prepared by UV irradiation method can be potentially used as an active filler applied in food packaging materials.

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Liu L, Kong F. 2019. Influence of nanocellulose on in vitro digestion of whey protein isolate. Carbohydrate Polymers. 210: 399-411. https://doi.org/10.1016/j.carbpol.2019.01.071. (Impact factor: 6.044)
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Liu L, Kerr WL, Kong F, Dee DR, Lin M. 2018. Influence of nano-fibrillated cellulose (NFC) on starch digestion and glucose absorption. Carbohydrate Polymers. 196: 146-53. https://doi.org/10.1016/j.carbpol.2018.04.116. (Impact factor: 7.182)
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Lin YJ, Shatkin JA, Kong F. 2019. Evaluating mucoadhesion properties of three types of nanocellulose in the gastrointestinal tract in vitro and ex vivo. Carbohydrate Polymers. 210: 157-66. https://doi.org/10.1016/j.carbpol.2019.01.029. (Impact factor: 7.182)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Kong F. Establishing the safety of cellulose nanomaterials for food related uses. IFT annual meeting. Chicago IL. July 16-18, 2018.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Liu L, Kong F. Influence of nano-fibrillated cellulose on starch digestion and glucose absorption. IFT annual meeting. Chicago IL. July 16-18, 2018.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Lin Y, Kong F. Evaluating mucoadhesion properties of nanocellulose in gastrointestinal tract. 2018 TAPPI International Conference on Nanotechnology for Renewable Materials. Madison, WI. June 11 - 15, 2018.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Yu, Z., Lin, S., Wang, W., Zeng, W., Mustapha, A., Lin, M.* 2018. Soy protein-based films incorporated with cellulose nanocrystals and pine needle extract for active packaging. Ind. Crops. Prod. 112, 412-419.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Xiong, Z., Lin, M.*, Lin, H., Huang, M. 2018. Facile synthesis of cellulose nanofiber nanocomposite as a SERS substrate for detection of thiram in juice. Carbohydr. Polym. 189, 79-86.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Yu, Z., Wang, W., Dhital, R., Kong, F., Mustapha, M., Lin, M.* 2019. Antimicrobial effect and toxicity of cellulose nanofibril/silver nanoparticle nanocomposite prepared by an ultraviolet irradiation method. Colloids Surf. B. 180, 212-220.


Progress 03/01/17 to 02/28/18

Outputs
Target Audience:The primary target audience for this project includes nanomaterialmanufacturers, food companies, governments, regulatoryagencies, researchers and scientists seeking to understand the behaviorof nanobiomaterials in the gastrointestinal tract and their healthimplications. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?University of Georgia: two graduate students were involved in this project under the supervision of Dr. Kong. They had workedon experimental design and implementation, and data analysis, and writing reports. They also attended IFT annualconference (2016). One graduate student worked on animal studies using mice under supervision of Dr. Guo. University of Missouri: three Graduate students were involved in this project under the supervision of Dr. Lin. Through the project, we built up close collaboration with USDA and private sector. Dr. Jo Anne Shatkin,President of Vireo Advisors, LLC, served in the advisory committee for our graduate student. How have the results been disseminated to communities of interest?The results have been disseminated to the community through conference presentations. What do you plan to do during the next reporting period to accomplish the goals?We plan to study impact of nanocellulose on digestion of lipid emulsions and proteins, as well as bioavailability of minerals. We will also use cell model and mice model to study toxicological effect and the impact on animal growth.

Impacts
What was accomplished under these goals? In the past year, our study focused on the effects of added NFC on solution viscosity, starch digestion and glucose absorption. NFC did not affect α-amylase and α-glucosidase activity, but significantly retarded glucose diffusion, delayed amylolysis and reduced the amount of glucose released during in vitro digestion of starch. Specifically, 1% NFC retarded ∼26.6% of glucose released during the amylolysis process. The greatly increased viscosity of NFC at concentrations >0.5% was thought to be the main mechanism for its potential hypoglycemic effects. NFC suspensions also had higher glucose adsorption capacity than those containing cellulose. In addition, NFC bound 35.6% of the glucose when the initial glucose level was within the range of 5-200 mM. These results suggest that NFC may be useful for building viscosity in food products and serving to inhibit glucose absorption in vivo in starch-containing products. Nanocellulose (NC) could enter human body as food or packaging additives or contaminants andposes unknown risks to health. We studied NC with different modifications for theirmucoadhesive properties in the digestive condition in vitro by four different assays to investigatethe potential impact when consuming NC. Mucoadhesive level of cellulose nanofiber (CNF),2,2,6,6- tetramethylpiperidine-1-oxyl-oxidized CNF (T-CNF), and cellulose nanocrystals (CNC)under gastric and intestinal condition was different for all assays. Overall 0.5% CNF showedhighest mucoadhesive ability in viscometric method both in gastric and intestinal condition, while0.465% T-CNF and 0.5% CNC showed better mucoadhesion by zeta potential and particle sizemethod, respectively. CNF was further tested by the flow-through method and showed retentionon porcine stomach and duodenum specimen. These results showed NC might be mucoadhesive, and future study of the interaction between NC and mucin and mucous membrane is needed. In addition, we havedeterminedthe effects and mechanisms of cellulosenanofiber (CNF) coating incorporated with chitosan and trans-cinnamaldehyde (TC) on thesurvival of different kinds of pathogens on whole and fresh-cut cantaloupes, respectively.The results showed that the CNF coating formed a dense film attached on the sample surface. Itwas effective for elimination of Salmonella enterica and Escherichia coli O157:H7 on the rind,but had relatively inferior effect on the reduction of Listeria monocytogenes. The incorporation of chitosan increased the pH and zeta potential values (P < 0.05), indicating an improvement of thepositive charges on the coating surface. The incorporation of TC had no effect on the pH or zetapotential (P > 0.05), but improved antimicrobial capacity of the coatings on all three kinds ofpathogens. Also, the oxygen barrier capacity of coatings were significantly enhanced (P < 0.05)after incorporating chitosan and/or TC, which was closely related to the increased reduction of theaerobic mold and yeast total colonies (P < 0.05). Overall, the CNF-based coating was preferredfor improving the microbiological safety of whole cantaloupe, but less effective for the fresh-cutsamples.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Lin Y, Kong F. Assessing mucoadhesion properties of nanocellulose in gastrointestinal tract in vitro. 2017 10TH Mini Summit on Food Safety, Policy, and Sustainability. Oct 29-31. Maryland. Liu L, Kong F. Influence of nanocellulose on starch digestion and glucose absorption. 2017 10TH Mini Summit on Food Safety, Policy, and Sustainability. Oct 29-31. Maryland.


Progress 03/01/16 to 02/28/17

Outputs
Target Audience:The primary target audience for this project includes nanomaterial manufacturers, food companies, governments, regulatory agencies,researchersand scientists seeking to understand the behavior of nanobiomaterialsin the gastrointestinal tract and theirhealth implications. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?University of Georgia: two graduate students were involved in this project under the supervision of Dr. Kong. They had worked on experimental design and implementation, and data analysis, and writing reports. They also attendedIFT annual conference (2016). Universit of Missouri: three Graduate students were involved in this project under the supervisionof Dr. Lin. How have the results been disseminated to communities of interest?The results have been disseminated to the community through publications, presentations, and social media. What do you plan to do during the next reporting period to accomplish the goals?University of Georgia: research will be conducted to understand interactions between nanocellulose and micro- and macro- nutrients, including the possible binding with protein, lipidand carbohydrates, and minerals. Study will be also conducted to understand the mucoadhesionbehaviourof nanocellulose. Univerity of Missouri, Columbia: furtherstudies will be conducted to testthe developed films on intestinal bacteria and mammalian cells and determine their toxicity.

Impacts
What was accomplished under these goals? University of Georgia: Dr. Kong's group had characterized two types of nanocellulose, CNF and CNC, and investigated the effect and causes of nanocellulose slowing mineral diffusion across the membrane.Particle size and viscosity of nanocellulose were determining by dynamic light scattering and rheometer. A simple model was built to test iron diffusion. Dialysis tubing (8kDa cut-off) loaded with 1mL water was put in solution with 100mg/L ferrous sulfate and various nanocellulose concentration and stirred for 1.5hour. Dialyzable iron (DI) was analyzed by colorimetric methods using 1,10-phenanthroline. Next, to test if binding of ions was the actual cause of lower iron diffusion, a solution with 100mg/L ferrous and 0.68% CNC or 0.12% CNF was prepared as above. The test groups were mixed at higher concentration of nanocellulose for 30min to allow interaction, and then diluted to the concentration as control before adding dialysis tubing. Here both pH2 and 5.5 were tested to mimic digestion pH. The results indicated that the average diameter of CNC and CNF was 139.8±4.4nm and 348.9±25.2nm, respectively. 2.7% CNC was more toward Newtonian fluid with viscosity of 0.0041Pa·s while 0.4% CNF was shear-thinning fluid with consistency of 1.04Pa·s and Power-Law index of 0.34 at 25°C. Mathematical modeling of the kinetics of DI showed exponential decay with nanocellulose concentration. Predicted equations are DI=81.44e^-1.24CNC% and DI=99.255e^-7.03CNF%. It was further confirmed that this effect was due to viscosity because whether allowing interaction or not didn't change DI both in pH2 or 5.5, but different pH changed DI. In conclusion,CNC and CNF could both decrease iron diffusion across the intestinal membrane, and this is possibly due to increased viscosity but not iron binding. This information could bring up the awareness when using nanocellulose as food additive in the future. University of Missouri, Columbia: In Dr. Lin's group,studies were carried out to 1) develop methodologies to characterize nanocellulose and their nanocomposites by using a combination of suitable detection and characterization techniques and strategies; 2) investigate the antimicrobial and toxicity of nanocellulose and nanocomposites and their effects on natural gut microflora and human cells. Cellulose nanofibers (CNFs) from commercial source was used in this study. A CNF film was prepared using a solution of CNFs, hydrolyzed polyvinyl alcohol (PVA), and glycerol. The solution was poured into square plastic petri plates and stored at room temperature for 24 h to form a film. Silver nanoparticles (AgNPs) were impregnated into the CNF films by reduction method using AgNO3 and NaBH4 solution. The CNFs and AgNP-CNF films were characterized by transmission electron microscopy (TEM). It was found that AgNPs were tightly attached onto the CNFs. Around 70% of the AgNPs were in the size range of 5-10 nm. The average size of these AgNPs was 7.03 ± 2.97 nm. Silver content on the hybrid was determined to be 1.06 ± 0.22% (w/w) using inductively coupled plasma (ICP) analysis. The CNF film and AgNP-CNF film were measured by scanning electron microscopy and energy dispersive X-ray spectrometry (SEM-EDS) analysis. The dense and pilotaxitic structure formed by cellulose fibrils were observed. The silver particles were found on the surface of the films.?Gluconobacter xylinus was grown for 7 days and the resulting cellulose film was stored in sterile DI water for two days. Bacterial cellulose (BC) slurry was combined with PVA and glycerol and the mixture poured into a large petri dish and dried overnight at 45oC. PVA-BC films were coated with AgNPs by reduction method. The incorporation of AgNPs was visually seen as a change in the color of the film from bright yellow to brownish yellow. Film samples were cut into 20 mm × 50 mm strips and analyzed by a texture analyzer. The thickness of the modified BC film was ~0.07 mm. The films will be used for further studies about their antimicrobial properties and toxicity.

Publications

  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Liou, P., Nayigiziki, F.X., Kong, F., Mustapha, A. and Lin, M., 2017. Cellulose nanofibers coated with silver nanoparticles as a SERS platform for detection of pesticides in apples. Carbohydrate Polymers, 157, pp.643-650