Engineered nanomaterials for biomedical applications

Engineered nanomaterials (ENM) have emerged as attractive and promising candidates for a wide range of advanced applications including in particular in medicine. However, the increased development of ENM raises the need to carefully assess their potential impact on human health and environment. For that, detailed evaluation of the intrinsic and biological identity of ENM is required for the safe design and use of these materials.

To this effect, the present thesis focuses on the synthesis and biocompatibility assessment of two different classes of nanomaterials, dendrimers and superparamagnetic iron oxide nanoparticles (SPIONs), promising future nanomedicines for drug delivery and imaging agents in magnetic resonance imaging (MRI). Assessment was performed on primary human monocyte derived macrophages (HMDM), primary human bronchial epithelial cells (PBEC), and cell lines. Hereby an insight on the impact of these materials on the immune system and on their promising and potential use as nanomedicines has been obtained. Furthermore, we attempted to use systems biology approaches as a novel tool to identify possible hazard of ENM by using next generation sequencing RNA-Seq and computational tools. Finally, we assessed the bio-nano-interactions by evaluating the effect of the protein corona on the targeting capabilities of ENM and their behaviour. Importantly, the ENM were extensively characterized, using different techniques prior to the toxicity studies.

In Paper I, we evaluated the biocompatibility of a library of polyester dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) including dendrimers with two different surface functionalization, hydroxyl and carboxylic end groups, and two commercial polyamidoamine dendrimers (PAMAM) with amine and hydroxyl end groups. We found excellent biocompatibility for the entire hydroxyl functional bis-MPA dendrimer library, whereas the cationic, but not the neutral PAMAM exerted dose and time dependent cytotoxicity in the cell models tested.

In paper II, using system biology approaches and bioinformatics tools, we were able to identify and validate the toxicity mechanism of PBEC exposed to PAMAMs dendrimers at low doses. Our studies showed that PAMAM-NH2, but not PAMAM-OH, caused down-regulation of cell cycle-related genes and cell cycle arrest in Sphase. Our findings provide evidence of the beneficial use of these new toxicology tools for the future risk assessment of nanomaterials. SPIONs have emerged as promising nanomaterials for biomedical applications, due to their excellent magnetic properties, chemical stability and biocompatibility.

In paper III, ultrasmall superparamagnetic iron oxide nanoparticles (USIRONs) were prepared by a one-pot aqueous approach by using Fe(OH)3 as iron precursor, vitamin C as reducing agent, and dehydroascorbic acid (DHAA) as capping agent. We showed that USIRONs present high crystallinity, long-term colloidal stability, enhanced saturation magnetization, and exhibit excellent biocompatibility as demonstrated in the toxicity evaluation using primary HMDM. When nanoparticles are in contact with physiological fluids, adsorption of proteins on the surface of the nanomaterial will occur, resulting in the establishment of aprotein corona. Whether the protein corona will affect the targeting capabilities of the ENM was investigated.

In paper IV, folic acid (FA)-conjugated iron oxide nanoparticles with poly(ethylene glycol) (PEG) or SiO2 surface coatings were synthetized. We evaluated their biocompatibility and specific targeting effects on HMDM and on ovarian cancer cells, that over express the folic acid receptor. Notably, we demonstrated the nanoparticles (NPs) were nontoxic to cells and that FA specific uptake was observed only for the FA iron oxide SiO2 coated NPs in the presence of serum proteins. Our studies contribute to the development of new nanomaterials and their applications, which may facilitate the clinical translation of the nanomedicines.

List of scientific papers

I. Feliu N, Walter MV, Montañez MI, Kunzmann A, Hult A, Nyström A, Malkoch M, Fadeel B. Stability and biocompatibility of a library of polyester dendrimers in comparison to polymanidoamine dendrimers. Biomaterials. 2012 33(7)1970-81.
https://doi.org/10.1016/j.biomaterials.2011.11.054

II. Feliu N, Kohonen P, Palmberg L, Nyström AM, and Fadeel B. Next generation sequencing reveals low-dose effects of dendrimers in primary human bronchial epithelial cells: a systems biology study. [Submitted]

III. Xiao L, Li J, Brougham DF, Fox EK, Feliu N, Bushmelev A, Schmidt A, Mertens N, Kiessling F, Valldor M, Fadeel B, Mathur S. Water-soluble superparamagnetic magnetite nanoparticles with biocompatible coating for enhanced magnetic resonance imaging. ACS Nano. 2011 5(8) 6315-24.
https://doi.org/10.1021/nn201348s

IV. Krais A, Wortmann L, Hermanns L, Feliu N, Vahter V, Stucky S, Mathur S, Fadeel B. Targeted uptake of folic acid-functionalized iron oxide nanoparticles by ovarian cancer cells in the presence but not in the absence of serum. Nanomedicine. 2014 Jan 31.
https://doi.org/10.1016/j.nano.2014.01.006