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Michal Gorzkiewicz,1,2 Monika Marcinkowska,1 Maciej Studzian,3,4 Iwona Karwaciak,4,5 Lukasz Pulaski,3,4 Barbara Klajnert-Maculewicz1 1Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland; 2Department of Molecular Medicine II, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; 3Department of Oncobiology and Epigenetics, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland; 4Laboratory of Transcriptional Regulation, Institute of Medical Biology PAS, Lodz, Poland; 5Laboratory of Epigenetics, Institute of Medical Biology PAS, Lodz, PolandCorrespondence: Michal Gorzkiewicz, Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, 141/143 Pomorska Street, Lodz, 90-236, Poland, Tel +48 42 635 41 47, Email michal.gorzkiewicz@biol.uni.lodz.plBackground: Mesalazine is one of the main drugs used to treat inflammatory bowel diseases. However, its applicability is limited by its rapid inactivation and removal from the organism, as well as the need for its membrane transporter-dependent cellular uptake to exert therapeutic effect. The present study involved the development of an innovative nanocarrier, based on poly(amidoamine) (PAMAM) dendrimer of the 4th generation, to obtain higher concentrations of the drug in the intestinal epithelial cells, thus increasing its anti-inflammatory potential. The work involved synthesis and in vitro characterization of covalent PAMAM-mesalazine conjugate with succinic linker.Results: PAMAM-mesalazine conjugate was synthesized and characterized by 1H NMR, 13C NMR, FTIR and MALDI-TOF MS. This allowed to confirm the purity of the obtained compound and intermediates. Based on the analyses, it was found that ~45 drug molecules were successfully attached to one molecule of PAMAM dendrimer. The conjugate was then characterized in terms of hydrodynamic diameter, zeta potential, spectral properties, drug release from the carrier, as well as cellular uptake and cytotoxicity in two in vitro models of gastrointestinal epithelium (CaCo-2 and HT-29 human cell lines). Analyzing cellular parameters related to the specific mechanism of action of mesalazine (inhibition of NF-κB signaling, decrease in interleukin and prostaglandin synthesis, and ROS scavenging), we showed that such a dendrimer-based carrier may enhance cellular uptake of the drug, which translated into its improved anti-inflammatory efficacy.Conclusion: The use of PAMAM macromolecule as a carrier for mesalazine increases the bioavailability of the drug, ensuring enhanced cellular uptake and bypassing the need to utilize mesalazine-specific membrane transporters. All these characteristics translate into an improved anti-inflammatory activity of mesalazine in vitro. In conjunction with appropriately designed in vivo studies, such a compound may prove to be a promising alternative to the therapeutics currently used in inflammatory bowel diseases.Graphical Abstract: Keywords: PAMAM dendrimer, mesalazine, inflammatory bowel disease, drug delivery