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Robert Czarnomysy1, Anna Bielawska2, Krzysztof Bielawski1 1Department of Synthesis and Technology of Drugs, Medical University of Bialystok, Bialystok 15-089, Poland; 2Department of Biotechnology, Medical University of Bialystok, Bialystok 15-089, PolandCorrespondence: Robert CzarnomysyDepartment of Synthesis and Technology of Drugs, Medical University of Bialystok, Kilinskiego 1, Bialystok 15-089, PolandTel +48 85 748 5700Fax +48 85 748 5718Email robert.czarnomysy@umb.edu.plBackground: Poly(amidoamine) (PAMAM) dendrimers are of considerable interest when used as a carrier for topical drugs for the skin, although little is known about their possible side effects. Therefore, our study was about the impact of 2nd and 3rd generation PAMAM dendrimers on human keratinocytes and fibroblasts cells.Methods: The effect of the tested compounds on collagen biosynthesis was determined using 5[3H]-proline incorporation bioassay. Morphological changes accompanying cell growth inhibition were observed using a confocal microscope. To evaluate the percentage of apoptotic/necrotic cells and the cell growth dynamic of apoptotic features, we performed Annexin V/PI double staining assay, assessed caspase activity, and performed cell cycle analysis by flow cytometry. The flow cytometry method was also used to determine the effect of dendrimers on pro-inflammatory cytokines (IL-6, IL-8 IL-1β).Results: The obtained results showed that as the concentration and the generation of dendrimers increased, collagen biosynthesis decreased. We also observed abnormalities in cell differentiation, which may have caused disturbed secretion of pro-inflammatory cytokines. We found that dendrimers cause chronic inflammation which may cause adverse changes in the skin, ultimately– leading to apoptosis in the case of dendrimers in lower concentrations or necrosis at higher concentrations (especially 3rd generation dendrimers). In addition, the inflammatory path induced by the tested compounds was caused by damage in the mitochondria, which we observed as a significant decrease in the mitochondrial membrane potential.Conclusion: The results of our study showed that PAMAM dendrimers can cause disorders of cell proliferation and differentiation and may be the cause of cell cycle deregulation and chronic adverse inflammation.Keywords: nanocarriers, drug delivery, carrier for topical drugs, apoptosis, cell cycle