A major challenge in understanding nanoplastic toxicity (or nanoparticles in general) lies in establishing the causal relationships between its physical properties and biological impact. This difficulty can be attributed to surface alterations that follow the formation of a biological complex around the nanoplastic, as exemplified by protein coronae. The protein corona is known to be responsible for the biological response elicited, although its own structure and attributes remain unknown. We approach this knowledge gap by independently studying the structure of soft and hard coronae using neutron scattering techniques. We investigated the formation and the structure of corona proteins (human serum albumin and lysozyme) and the resulting protein corona complexes with polystyrene nanoplastics of different sizes (20 and 200 nm) and charges. Soft corona complexes (regardless of protein type) adopted a structure where the nanoplastics were surrounded by a loose protein layer (∼2–3 protein molecules thick). Hard corona complexes formed fractal-like aggregates, and the morphology of which is known to be harmful to cellular membranes. In most cases, hard-corona coated nanoplastics also formed fractal-like aggregates in solution. Nanoplastic size affected the structures of both the protein corona and the intrinsic protein: more significant conformational change was observed in the hard corona proteins around smaller nanoparticles compared to larger ones, as the self-association forces holding the nanoplastic/protein complex together were stronger. This also implies that protein-dependent biochemical processes are more likely to be disrupted by smaller polystyrene nanoplastics, rather than larger ones.

Plastic waste is ubiquitously spread across the world and its smaller analogs-microplastics and nanoplastics-raise particular health concerns. While biological impacts of microplastics and nanoplastics have been actively studied, the chemical and biological bases for the adverse effects are sought after. This work explores contributory factors by combining results from in vitro and model mammalian membrane experimentation to assess the outcome of cell/nanoplastic interactions in molecular detail, inspecting the individual contribution of nanoplastics and different types of protein coronae. The in vitro study showed mild cytotoxicity and cellular uptake of polystyrene (PS) nanoplastics, with no clear trend based on nanoplastic size (20 and 200 nm) or surface charge. In contrast, a nanoplastic size-dependency on bilayer disruption was observed in the model system. This suggests that membrane disruption resulting from direct interaction with PS nanoplastics has little correlation with cytotoxicity. Furthermore, the level of bilayer disruption was found to be limited to the hydrophilic headgroup, indicating that transmembrane diffusion was an unlikely pathway for cellular uptake-endocytosis is the viable mechanism. In rare cases, small PS nanoplastics (20 nm) were found in the vicinity of chromosomes without a nuclear membrane surrounding them; however, this was not observed for larger PS nanoplastics (200 nm). We hypothesize that the nanoplastics can interact with chromosomes prior to nuclear membrane formation. Overall, precoating PS particles with protein coronae reduced the cytotoxicity, irrespective of the corona type. When comparing the two types, the extent of reduction was more apparent with soft than hard corona.

When ultrasound waves are applied to a compressible Newtonian fluid, bulk viscosity plays an important parameter to cause attenuation. Ultrasound spectroscopy is an important technique to characterise and determine the physico-chemical properties of many food components because it is a non-invasive, non-destructive, easy and accurate technique. The aim of this study was to find the bulk viscosity of three brands of sunflower and extra-virgin olive oil by using the Navier's-Stoke equation across a temperature range of 5°C to 40°C and to test the hypothesis that there is a significant difference in the value of bulk viscosity between the different brands of sunflower and olive oil used. The value of bulk viscosity was not found to be constant over the operating frequency range of 12-100 MHz, which suggested edible oils are non-Newtonian fluids. Also, no significant statistical difference of bulk viscosity values was found between different brands of the same oil (p ≥ 0.05). This shows bulk viscosity is not affected by small compositional variations. Acoustic spectroscopy is increasingly being used to characterise food materials. More studies on bulk viscosity must be employed in order to be able to utilise this technology to its full strength.

Ultrasound waves are longitudinal sound waves of frequency of 20 kHz or more. As low amplitude ultrasonic waves do not significantly modify the material under examination, they can be used to analyse the material. However, high amplitude ultrasonic waves can be used to process food as they have the capacity to alter the food material by cavitation. Nowadays ultrasound processing is increasingly being used in the dairy industry. The use of high amplitude ultrasound by itself may not be effective in in bringing about the desired processing effects. Hence, it can be coupled with pressure or heat or both to get the desired results. Thermosonication involves the simultaneous use of low frequency ultrasound waves (20 kHz) along with heat; and the both together have some synergistic effect. When heat and ultrasound is used together, the process temperature is considerably reduced compared to the conventional heating process, making it a green and economical technology as less energy is consumed; this in turn makes it a cost-efficient process. If thermosonication is seen to bring about the desired effects in milk, then it can be used as a commercial method to treat and homogenize milk in the future.