# Bioavailability of Liposomal Vitamin C in Powder Form: A Randomized, Double-Blind, Cross-Over Trial
## 5 Conclusions  
In brief, using technology devoid of organic solvents, a liposomal vitamin C suspension was obtained, which, after mixing with maltodextrin, was dehydrated in a disc spray dryer. The resulting powder-like microcapsules, with an average particle diameter of 23.4 \(\pm\) 1.2 \(\mu\)m, were composed of a carbohydrate material encapsulating liposomal vitamin C particles. Visible under the SEM, the intact surface of the microcapsules provided a barrier protecting both the liposomes and the encapsulated vitamin C from the undesirable effects of external stressors. In cryogenic transmission electron microscopy (cryo-TEM) observations, we confirmed the presence in the hydrated powder of liposomes (mainly LUV) with preserved integrity of the phospholipid bilayer and a spherical shape and smooth surface. The liposomes we obtained were characterized by a relatively small particle size (262 \(\pm\) 49.8 nm) and the narrow width of distribution (span = 0.500), as well as the high absolute value of the zeta potential (-41.44 \(\pm\) 0.30 mV, that is >30 mV) obtained for the hydrated powder, further confirming the lack of negative effects of spray drying on product quality. In the present study, the main emphasis was laid on demonstrating the absence of negative effects of spray drying on the properties and pharmacokinetic profile of the obtained liposomal vitamin C powder. This was important because dehydration of lipid carrierssignificantly prolongs the shelf life of the product, eliminates the need to include preservatives in its composition (this is necessary in the case of liquid liposomal suspensions), reduces transport and distribution costs, and, at the same time, broadens the possibilities of its practical applications. The liposomal vitamin C powder we obtained is, by design, intended for use in the production of dietary supplements (tablets, capsules with powder, vitamin premixes, jellies, etc.) and nutraceuticals but also functional foods. Due to the limited thermal stability of ascorbic acid, the use of liposomal vitamin C in high-temperature-processed products may be difficult and result in the need to modify the manufacturing process of vitamin C-fortified foods. An additional difficulty in the case of inclusion of liposomal vitamin C in the form of powder in formulations of complex composition may be the presence of components such as protein or fat, the removal of which during the procedure of sample preparation for observation under a cryogenic electron microscope (cryo-TEM) may realistically disturb the result of the determination aimed at confirming the presence of intact liposomes in the finished product. Given the limitations above, further experiments would be needed to determine the effects of various technological processes, including thermal food preservation, extrusion, high-pressure homogenization, and selected matrices, on the stability of incorporated liposomal vitamin C. It would also be important to determine the effect of powdered liposomal vitamin C on the sensory properties of enriched foods [2]. The main principle behind liposomal technology is to enhance the absorption of encapsulated active substances, thereby increasing bioavailability. In the initial stage of our study, using the widely recognized Caco-2 cell model, we compared the bioavailability of non-liposomal and liposomal ascorbic acid. The results show that liposomal vitamin C had 22.28% higher bioavailability compared to non-liposomal vitamin C, as measured in the basal layer of the Caco-2 cell model. Given that these results were obtained under controlled laboratory conditions, which are inherently predictive, liposomal vitamin C powder was also evaluated in a clinical trial. In the clinical study, we assessed the pharmacokinetic properties of the tested formulations, including AUC, C\({}_{\text{max}}\), C\({}_{\text{10h}}\), C\({}_{\text{24h}}\), and T\({}_{\text{max}}\).