Enzymatic hydrolysis for pre-treating human serum before titanium dioxide nanoparticles assessment by spICP-MS

The current use of inorganic nanoparticles (NPs) in many industrial sectors, particularly in the food industry, has led to growing concerns about the toxicity of these emerging materials to humans. Therefore, NPs assessment in foodstuff, environmental materials and biological fluids is becoming an important topic, and the development of reliable quantification/characterization analytical methods is needed. The presence of NPs in blood and urine can be expected because of the bioavailability/assimilation of these entities by the organism. However, the determination of NPs in biofluids is a challenge mainly due to the complexity of the sample and the low levels of NPs (basal levels). The research on new methodologies for sample treatment is therefore needed. The possibilities of enzymatic hydrolysis followed by centrifugal ultrafiltration for isolating titanium dioxide nanoparticles (TiO₂ NPs) from serum samples have been explored in the current research. Hydrolysis of serum's matrix components was performed with a pancreatin-lipase mixture (0.1 %(w/v) each one) operating at pH 7.4 and 37 °C for 4.0 h under orbital - horizontal shaking at 150 rpm. In addition, centrifugal ultrafiltration (30 kDa molecular weight cutoff (MWCO) membrane) was optimised for removing enzymes residues and other matrix's components. The developed method showed a limit of detection of 6.89 × 10³ NPs mL^-1, and a limit of detection in size of 36 nm, whereas analytical recovery for spiking assays with 100 nm TiO₂ NPs were within the 103-114 % range.