Both silicon and silica nanoparticles (SiNPs and SiO2NPs, respectively) are currently considered to be promising carriers for targeted drug delivery. However, the available data on their in vivo toxicity are limited. The present study was aimed at investigation of SiNP and SiO2NP (mean diameter 10 and 13 nm, respectively) toxicity using both morphological and functional criteria. Hematological and biochemical parameters were assessed in Sprague-Dawley rats 5, 21 and 60 days after administration of NPs. Inner ear function was determined using otoacoustic emission testing at 21 and 60 days after infusion of NPs. Furthermore, the histological structure of liver, spleen and kidney samples was analyzed. Intravenous infusion of SiNPs or SiO2NPs (7 mg/kg) was not associated with significant changes in hemodynamic parameters. Hearing function remained unchanged over the entire observation period. Both inter- and intragroup changes in blood counts and biochemical markers were non-significant. Histological findings included the appearance of foreign body-type granulomas in the liver and spleen as well as microgranulation in the liver after administration of NPs. The number of granulomas was significantly lower after administration of SiNPs compared with SiO2NPs. In conclusion, both tested types of NPs are relatively biocompatible nanomaterials, at least when considering acute toxicity.

Summary Acute mesenteric ischaemia is a syndrome caused by inadequate blood flow through the mesenteric vessels, resulting in ischaemia and eventual gangrene of the bowel wall. Although relatively rare, it is a potentially life‐threatening condition. The maintenance of haemodynamic stability, along with adequate oxygen saturation, and the correction of any electrolyte imbalance, are of the utmost importance. However, nicotinamide adenine dinucleotide (NAD) biosynthesis modulation by precursor introduction can also be a powerful tool for preventing injury. Nicotinamide riboside is a pyridine‐nucleoside form of vitamin B3 that functions as a precursor to NAD+. The present study investigated nicotinamide riboside's effect on endothelium functional state, microcirculation and intestinal morphology in acute mesenteric ischaemia and reperfusion. Mesenteric ischaemia was simulated after the adaptation period (15 minutes) by occluding the superior mesenteric artery for 60 minutes, followed by a reperfusion period of 30 minutes. The functional state of intestinal microcirculation was evaluated by laser Doppler flowmetry. Endothelial functional activity was studied by using wire myography. Intestinal samples were stained with haematoxylin and eosin for histological analysis. The results revealed that nicotinamide riboside protects the intestinal wall from ischaemia‐reperfusion injury, as well as improving the relaxation function of mesenteric vessels. Nicotinamide riboside's protective effect in small intestine ischaemia‐reperfusion can be used to reduce ischaemia‐reperfusion injury, as well as to preserve intestinal grafts until transplant.