Widely used food-grade nanomaterials (TiO2 and SiO2) increase cytotoxicity, cellular uptake, and cellular translocation of co-ingested pesticide, boscalid.

Laser printers emit high levels of nanoparticles (PM0.1) during operation. Although it is well established that toners contain multiple engineered nanomaterials (ENMs), little is known about inhalation exposures to these nanoparticles and work practices in printing centers. In this report we present a comprehensive inhalation exposure assessment of indoor microenvironments at six commercial printing centers in Singapore, the first such assessment outside of the United States, using real-time personal and stationary monitors, time-integrated instrumentation and multiple analytical methods. Extensive presence of ENMs, including titanium dioxide, iron oxide and silica, were detected in toners and in airborne particles collected from all six centers studied. We document high transient exposures to emitted nanoparticles (peaks of ~500,000 particles/cm 3 , lung deposited surface area of up to 220 m 2 /cm 3 , and PM0.1 up to 16 g/m 3 ) with complex PM0.1 chemistry that included 40-60 wt% organic carbon, 10-15 wt% elemental carbon, and 14 wt% trace elements. We also record 271.6 -474.9 pmol/mg of Environmental Protection Agency-priority polycyclic aromatic hydrocarbons. These findings highlight the potentially high occupational inhalation exposures to nanoparticles with complex compositions resulting from widespread usage of nano-enabled toners in the printing industry, as well as inadequate ENM specific exposure control measures in these settings. congeners detected in PCP, background indoor ambient air, toners, and outdoor environment (PDF).

Statement of OriginalityI hereby certify that the work embodied in this thesis is the result of original research and has not been submitted for a higher degree to any other University or Institution.

Exploitation of nature-derived materials is an important approach to promote environmental sustainability. Among these materials, cellulose is of particular interest due to its abundance and relative ease of access. As a food ingredient, cellulose nanofibers (CNFs) have found interesting applications as emulsifiers and modulators of lipid digestion and absorption. In this report, we show that CNFs can also be modified to modulate the bioavailability of toxins, such as pesticides, in the gastrointestinal tract (GIT) by forming inclusion complexes and promoting interaction with surface hydroxyl groups. CNFs were successfully functionalized with (2-hydroxypropyl)-β-cyclodextrin (HPBCD) using citric acid as a crosslinker via esterification. Functionally, the potential for pristine and functionalized CNFs (FCNFs) to interact with a model pesticide, boscalid, was tested. Based on direct interaction studies, adsorption of boscalid saturated at around 3.09% on CNFs and at 12.62% on FCNFs. Using an in vitro GIT simulation platform, the adsorption of boscalid on CNFs/FCNFs was also studied. The presence of a high-fat food model was found to have a positive effect in binding boscalid in a simulated intestinal fluid environment. In addition, FCNFs were found to have a greater effect in retarding triglyceride digestion than CNFs (61% vs 30.6%). Overall, FCNFs were demonstrated to evoke synergistic effects of reducing fat absorption and pesticide bioavailability through inclusion complex formation and the additional binding of the pesticide onto surface hydroxyl groups on HPBCD. By adopting food-compatible materials and processes for production, FCNFs have the potential to be developed into a functional food ingredient for modulating food digestion and the uptake of toxins.

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