## 1 Introduction  
These days, nanoparticles are increasingly used worldwide in a wide range of applications including pharmaceutical, cosmetic, biomedical, food, automotive, and military [1]. Given the ever-growing market demand, their annual production is expected to reach 2.5 million tons by 2025 [2].  
The study presented below focused on titanium dioxide (E171), commonly used as a white pigment and softening agent in paint, cosmetics, pharmaceutical products, and food, and containing a certain fraction of particles falling within the nano range [3]. Until very recently, it was considered safe for consumption; however, in light of growing concerns regarding its potential genotoxicity, under the current EFSA (European Food Safety Authority) classification the compound is no longer considered safe for use as a food additive in the European Union [4]. The primary reason for this decision stemmed from its content of an approximately 30-40% [5, 6] fraction of nanoparticles, which have been under intensive scientific scrutiny in recent years because of their suspected negative impact on human health, particularly with respect to the gastrointestinal tract. The WHO (World Health Organization) expects the mortality rates related to gastrointestinal cancer to increase substantially in the 21 st century [7], which underscores the importance of avoiding risk factors exacerbating the incidence of gastrointestinal diseases by discontinuing the use of potentially harmful additives.  
There is still limited understanding of the potential health risks linked to the consumption of foods containing nanoparticles. However, E171 has increasingly been connected to intestinal barrier disorders, including intestinal dysbiosis, which can interfere with the normal functioning of the gastrointestinal tract (GIT) [6]. Several in vitro studies have also documented the adverse effects of TiO\({}_{2}\)/TiO\({}_{2}\) nanoparticles (NPs) on the intestinal epithelial membrane [8]. The intestinal epithelium, which consists of various cell types (such as enterocytes, goblet cells, enteroendocrine cells, Paneth cells, and stem cells), forms the largest mucous membrane surface in the body and acts as a protective barrier against external environments. Enterocytes and goblet cells are the two main types of cells found in the intestine [9; 10] and are responsible for nutrient and water absorption, as well as maintaining intestinal barrier function (IBF) [11; 12]. Different cell cultures have been employed to model human intestinal epithelium [13], with enterocytes represented by Caco-2 cells being one of the most commonly used models [9]. Ultrastruct analyses have shown that these cells resemble human intestinal epithelial cells in terms of morphology and polarity, making Caco-2 cells a reliable in vitro model for studying human intestinal epithelium [14].  
Additionally, little is known about the potential bioaccumulation of TiO\({}_{2}\) NPs within the food chain. Because of the concerns raised in the existing literature, the aim of this study was to evaluate the toxicological effects, including the impact on inflammatory processes, of exposing Caco-2 colon cancer cells to three different types of E171 and TiO\({}_{2}\) NPs.