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Josefine Eilsø Nielsen

Associate Professor - Section for Pharmaceutics and Social Pharmacy

Email j.e.nielsen@farmasi.uio.no

Phone +47 22 85 65 92

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Visiting address Sem Sælands vei 3 Farmasibygningen 0371 Oslo

Postal address Postboks 1068 Blindern 0316 Oslo

Other affiliations LINK-Centre for Learning and Education (Student)

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Academic Interests

Development and characterization of drug delivery systems for treatment of infectious diseases.
Use of soft matter and biomaterials based on polymers, colloids, surfactants, peptides, peptidomimetics and proteins in drug delivery.
Development of novel antimicrobial peptides and peptoids with self-assembly properties.
Thermodynamics and structure of self-assembled soft and biological matter.
Lipid vesicles and lipid nanoparticles as drug delivery vehicles.

Teaching

FARM2150 – Formulation of Drugs and Quality Assurance in Drug Production

FARM5200 – The use of biopolymers in drugs and improvement of health

Higher education and employment history

Associate professor, Department of Pharmacy 2024-

Postdoc, Bioengineering, Stanford University 2021-2024

PhD fellow, Department of Chemistry, University of Oslo, 2017-2020

Scientific officer, Norwegian Medicines Agency, 2016-2017

Masters in Pharmacy, University of Oslo, 2015

Zielke, Claudia; Rad, Behzad; Nielsen, Josefine Eilsø; Li, Jiaxin; Pimcharoen, Sopida & Sawant, Manasi [Show all 10 contributors for this article] (2026). Human cathelicidin peptide LL-37 compacts nucleic acids and alters neutrophil extracellular trap structure. Scientific Reports. 16(1). doi: 10.1038/s41598-026-48091-4. Full text in Research Archive Show summary
The human cathelicidin host defense peptide LL-37 is expressed by many cell types, including neutrophils, macrophages, and epithelial cells, and forms complexes with nucleic acids that can have either beneficial or detrimental health effects. We suggest that these differential impacts are directly connected to the extent of nucleic acid binding by LL-37. Here, we use phage λ DNA and techniques such as high-resolution video microscopy, gel electrophoresis, circular dichroism, and displacement assays to show that LL-37 binds non-specifically to dsDNA, condensing it, followed by formation of progressively larger complexes from smaller domains, until “complete” complexation is attained at a (w/w) ratio of DNA/LL-37 of 1:1.7. The morphology of these complexes is concentration-dependent, with relatively low LL-37 amounts yielding loosely aggregated DNA structures and higher LL-37 concentrations leading to well-defined, disc-like complexes of about 150 nm in diameter. The condensation of nucleic acids, which causes a loss of the characteristic B-DNA features, results from interactions of the phosphodiester backbone with cationic amino acid side chains of the peptide at physiological pH, most likely in A-T rich sequences of the nucleic acid. Our results show that the α-helical structure of the peptide with its amphipathic and hydrophobic surfaces is essential. Finally, we show that LL-37 complexation alters the structure of neutrophil extracellular traps (NETs), causing a significant reduction in projected NET area at high LL-37 concentrations. Our data suggest that LL-37 helps prevent nucleic acid dispersal and condenses dsDNA, which may impact the biophysics of NET clearance.
Koynarev, Vladimir Rosenov; Borgos, Kari Kristine Almåsvold; Kohlbrecher, Joachim; Porcar, Lionel; Nielsen, Josefine Eilsø & Lund, Reidar (2024). Antimicrobial Peptides Increase Line Tension in Raft-Forming Lipid Membranes. Journal of the American Chemical Society. ISSN 0002-7863. 146(30), p. 20891–20903. doi: 10.1021/jacs.4c05377. Full text in Research Archive Show summary
The formation of phase separated membrane domains is believed to be essential for the function of the cell. The precise composition and physical properties of lipid bilayer domains play crucial roles in regulating protein activity and governing cellular processes. Perturbation of the domain structure in human cells can be related to neurodegenerative diseases and cancer. Lipid rafts are also believed to be essential in bacteria, potentially serving as targets for antibiotics. An important question is how the membrane domain structure is affected by bioactive and therapeutic molecules, such as surface-active peptides, which target cellular membranes. Here we focus on antimicrobial peptides (AMPs), crucial components of the innate immune system, to gain insights into their interaction with model lipid membranes containing domains. Using small-angle neutron/X-ray scattering (SANS/SAXS), we show that the addition of several natural AMPs (indolicidin, LL-37, magainin II, and aurein 2.2) causes substantial growth and restructuring of the domains, which corresponds to increased line tension. Contrast variation SANS and SAXS results demonstrate that the peptide inserts evenly in both phases, and the increased line tension can be related to preferential and concentration dependent thinning of the unsaturated membrane phase. We speculate that the lateral restructuring caused by the AMPs may have important consequences in affecting physiological functions of real cells. This work thus shines important light onto the complex interactions and lateral (re)organization in lipid membranes, which is relevant for a molecular understanding of diseases and the action of antibiotics.
Nielsen, Josefine Eilsø; Koynarev, Vladimir Rosenov & Lund, Reidar (2023). Peptide meets membrane: Investigating peptide-lipid interactions using small-angle scattering techniques. Current Opinion in Colloid & Interface Science. ISSN 1359-0294. 66. doi: 10.1016/j.cocis.2023.101709. Full text in Research Archive Show summary
Peptide–lipid interactions play an important role in defining the mode of action of drugs and the molecular mechanism associated with many diseases. Model membranes consisting of simple lipid mixtures mimicking real cell membranes can provide insight into the structural and dynamic aspects associated with these interactions. Small-angle scattering techniques based on X-rays and neutrons (SAXS/SANS) allow in situ determination of peptide partition and structural changes in lipid bilayers in vesicles with relatively high resolution between 1-100 nm. With advanced instrumentation, time-resolved SANS/SAXS can be used to track equilibrium and nonequilibrium processes such as lipid transport and morphological transitions to time scales down to a millisecond. In this review, we provide an overview of recent advances in the understanding of complex peptide–lipid membrane interactions using SAXS/SANS methods and model lipid membrane unilamellar vesicles. Particular attention will be given to the data analysis, possible pitfalls, and how to extract quantitative information using these techniques.
Carrer, Manuel; Nielsen, Josefine Eilsø; Cezar, Henrique Musseli; Lund, Reidar; Cascella, Michele & Silva, Thereza Amelia Soares da (2023). Accelerating Lipid Flip-Flop at Low Concentrations: A General Mechanism for Membrane Binding Peptides. The Journal of Physical Chemistry Letters. 14(31), p. 7014–7019. doi: 10.1021/acs.jpclett.3c01284. Full text in Research Archive Show summary
We report a physicochemical investigation of the lipid transport properties of model lipid membranes in the presence of the antimicrobial peptide indolicidin through comparisons of experimental SANS/SAXS scattering techniques to fully atomistic molecular dynamics simulations. In agreement with the experiment, we show that upon peripheral binding of the peptides, even at low concentrations, lipid flip-flop dynamics is greatly accelerated. Computer modeling elucidates the interplay between structural changes and lipid dynamics induced by peptides and proposes a mechanism for the mode of action of antimicrobial peptides, assessing the major role of entropy for the catalysis of the flipping events. The mechanism introduced here is universal for all peptides with preferential peripheral binding to the membrane as it does not depend on the specific amino acid sequence.
Kim, Minsang; Cheon, Yeongmi; Shin, Dongmin; Choi, Jieun; Nielsen, Josefine Eilsø & Jeong, Myeong Seon [Show all 13 contributors for this article] (2023). Real-Time Monitoring of Multitarget Antimicrobial Mechanisms of Peptoids Using Label-Free Imaging with Optical Diffraction Tomography. Advanced Science. doi: 10.1002/advs.202302483. Full text in Research Archive Show summary
Abstract Antimicrobial peptides (AMPs) are promising therapeutics in the fight against multidrug‐resistant bacteria. As a mimic of AMPs, peptoids with N ‐substituted glycine backbone have been utilized for antimicrobials with resistance against proteolytic degradation. Antimicrobial peptoids are known to kill bacteria by membrane disruption; however, the nonspecific aggregation of intracellular contents is also suggested as an important bactericidal mechanism. Here,structure‐activity relationship (SAR) of a library of indole side chain‐containing peptoids resulting in peptoid 29 as a hit compound is investigated. Then, quantitative morphological analyses of live bacteria treated with AMPs and peptoid 29 in a label‐free manner using optical diffraction tomography (ODT) are performed. It is unambiguously demonstrated that both membrane disruption and intracellular biomass flocculation are primary mechanisms of bacterial killing by monitoring real‐time morphological changes of bacteria. These multitarget mechanisms and rapid action can be a merit for the discovery of a resistance‐breaking novel antibiotic drug.
König, Nico; Szostak, Szymon Mikolaj; Nielsen, Josefine Eilsø; Dunbar, Martha; Yang, Su & Chen, Weike [Show all 13 contributors for this article] (2023). Stability of Nanopeptides: Structure and Molecular Exchange of Self-assembled Peptide Fibers. ACS Nano. ISSN 1936-0851. 17(13), p. 12394–12408. doi: 10.1021/acsnano.3c01811. Full text in Research Archive Show summary
Often nanostructures formed by self-assembly of small molecules based on hydrophobic interactions are rather unstable, causing morphological changes or even dissolution when exposed to changes in aqueous media. In contrast, peptides offer precise control of the nanostructure through a range of molecular interactions where physical stability can be engineered in and, to a certain extent, decoupled from size via rational design. Here, we investigate a family of peptides that form beta-sheet nanofibers and demonstrate a remarkable physical stability even after attachment of poly(ethylene glycol). We employed small-angle neutron/X-ray scattering, circular dichroism spectroscopy, and molecular dynamics simulation techniques to investigate the detailed nanostructure, stability, and molecular exchange. The results for the most stable sequence did not reveal any structural alterations or unimer exchange for temperatures up to 85 °C in the biologically relevant pH range. Only under severe mechanical perturbation (i.e., tip sonication) would the fibers break up, which is reflected in a very high activation barrier for unimer exchange of ∼320 kJ/mol extracted from simulations. The results give important insight into the relation between molecular structure and stability of peptide nanostructure that is important for, e.g., biomedical applications.
Lone, Abdullah; Nielsen, Josefine Eilsø; Thulstrup, Peter W.; Lund, Reidar; Hansen, Paul Robert & Jenssen, Håvard (2022). Cyclic N-locked indolicidin analogues with antimicrobial activity: Effect of ring size and fatty acid acylation. European Journal of Medicinal Chemistry Reports. ISSN 2772-4174. 6. doi: 10.1016/j.ejmcr.2022.100080. Full text in Research Archive
Nielsen, Josefine Eilsø; Alford, Morgan Ashley; Yung, Deborah Bow Yue; Molchanova, Natalia; Fortkort, John A. & Lin, Jennifer S. [Show all 12 contributors for this article] (2021). Self-Assembly of Antimicrobial Peptoids Impacts Their Biological Effects on ESKAPE Bacterial Pathogens. ACS Infectious Diseases. doi: 10.1021/acsinfecdis.1c00536. Full text in Research Archive
Nielsen, Josefine Eilsø; Prévost, Sylvain François; Jenssen, Håvard & Lund, Reidar (2021). Impact of antimicrobial peptides on: E. coli -mimicking lipid model membranes: Correlating structural and dynamic effects using scattering methods. Faraday discussions. ISSN 1359-6640. 232, p. 203–217. doi: 10.1039/d0fd00046a. Full text in Research Archive
Nielsen, Josefine Eilsø & Lund, Reidar (2021). Molecular Transport and Growth of Lipid Vesicles Exposed to Antimicrobial Peptides. Langmuir. ISSN 0743-7463. 38(1), p. 374–384. doi: 10.1021/acs.langmuir.1c02736. Full text in Research Archive Show summary
It is well-known that lipids constituting the cytoplasmic membrane undergo continuous reorganization to maintain the appropriate composition important for the integrity of the cell. The transport of lipids is controlled by mainly membrane proteins, but also spontaneous lipid transport between leaflets, lipid “flip–flop”, occurs. These processes do not only occur spontaneously under equilibrium, but also promote structural rearrangements, morphological transitions, and growth processes. It has previously been shown that intravesicular lipid “flip–flop” and intervesicular lipid exchange under equilibrium can be deduced indirectly from contrast variation time-resolved small-angle neutron scattering (TR-SANS) where the molecules are “tagged” using hydrogen/deuterium (H/D) substitution. In this work, we show that this technique can be extended to simultaneously detect changes in the growth and the lipid “flip–flop” and exchange rates induced by a peptide additive on lipid vesicles consisting of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), d-DMPC (1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine), DMPG (1,2-dimyristoyl-sn-glycero-3-phospho-(1′-rac-glycerol)), and small amounts of DMPE-PEG (1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000]). Changes in the overall size were independently monitored using dynamic light scattering (DLS). We find that the antimicrobial peptide, indolicidin, accelerates lipid transport and additionally induces limited vesicular growth. Moreover, in TR-SANS experiments using partially labeled lipid mixtures to separately study the kinetics of the lipid components, we show that, whereas peptide addition affects both lipids similarly, DMPG exhibits faster kinetics. We find that vesicular growth is mainly associated with peptide-mediated lipid reorganization that only slightly affects the overall exchange kinetics. This is confirmed by a TR-SANS experiment of vesicles preincubated with peptide showing that after pre-equilibration the kinetics are only slightly slower.
Nam, Ho Yeon; Choi, Jieun; Kumar, S. Dinesh; Nielsen, Josefine Eilsø; Kyeong, Minkyo & Wang, Sungrok [Show all 15 contributors for this article] (2020). Helicity Modulation Improves the Selectivity of Antimicrobial Peptoids. ACS Infectious Diseases. 6(10), p. 2732–2744. doi: 10.1021/acsinfecdis.0c00356. Full text in Research Archive
Nielsen, Josefine Eilsø; König, Nico; Yang, Su; Skoda, Maximilian W. A.; Maestro, Armando & Dong, He [Show all 8 contributors for this article] (2020). Lipid membrane interactions of self-assembling antimicrobial nanofibers: effect of PEGylation. RSC Advances. 10(58), p. 35329–35340. doi: 10.1039/d0ra07679a. Full text in Research Archive
Nielsen, Josefine Eilsø; Bjørnestad, Victoria Ariel; Pipich, Vitaliy; Jenssen, Håvard & Lund, Reidar (2020). Beyond structural models for the mode of action: How natural antimicrobial peptides affect lipid transport. Journal of Colloid and Interface Science. ISSN 0021-9797. 582, p. 793–802. doi: 10.1016/j.jcis.2020.08.094. Full text in Research Archive Show summary
Hypothesis: Most textbook models for antimicrobial peptides (AMP) mode of action are focused on structural effects and pore formation in lipid membranes, while these deformations have been shown to require high concentrations of peptide bound to the membrane. Even insertion of low amounts of peptides in the membrane is hypothesized to affect the transmembrane transport of lipids, which may play a key role in the peptide effect on membranes. Experiments: Here we combine state-of-the-art small angle X-ray/neutron scattering (SAXS/SANS) techniques to systematically study the effect of a broad selection of natural AMPs on lipid membranes. Our approach enables us to relate the structural interactions, effects on lipid exchange processes, and thermodynamic parameters, directly in the same model system. Findings: The studied peptides, indolicidin, aurein 1.2, magainin II, cecropin A and LL-37 all cause a general acceleration of essential lipid transport processes, without necessarily altering the overall structure of the lipid membranes or creating organized pore-like structures. We observe rapid scrambling of the lipid composition associated with enhanced lipid transport which may trigger lethal signaling processes and enhance ion transport. The reported membrane effects provide a plausible canonical mechanism of AMP-membrane interaction and can reconcile many of the previously observed effects of AMPs on bacterial membranes.
Molchanova, Natalia; Nielsen, Josefine Eilsø; Sørensen, Kristian B; Krishna, Bala; Hansen, Paul Robert & Lund, Reidar [Show all 8 contributors for this article] (2020). Halogenation as a tool to tune antimicrobial activity of peptoids. Scientific Reports. 10(1). doi: 10.1038/s41598-020-71771-8. Full text in Research Archive Show summary
Abstract Antimicrobial peptides have attracted considerable interest as potential new class of antibiotics against multi-drug resistant bacteria. However, their therapeutic potential is limited, in part due to susceptibility towards enzymatic degradation and low bioavailability. Peptoids (oligomers of N -substituted glycines) demonstrate proteolytic stability and better bioavailability than corresponding peptides while in many cases retaining antibacterial activity. In this study, we synthesized a library of 36 peptoids containing fluorine, chlorine, bromine and iodine atoms, which vary by length and level of halogen substitution in position 4 of the phenyl rings. As we observed a clear correlation between halogenation of an inactive model peptoid and its increased antimicrobial activity, we designed chlorinated and brominated analogues of a known peptoid and its shorter counterpart. Short brominated analogues displayed up to 32-fold increase of the activity against S. aureus and 16- to 64-fold against E. coli and P. aeruginosa alongside reduced cytotoxicity. The biological effect of halogens seems to be linked to the relative hydrophobicity and self-assembly properties of the compounds. By small angle X-ray scattering (SAXS) we have demontrated how the self-assembled structures are dependent on the size of the halogen, degree of substitution and length of the peptoid, and correlated these features to their activity.
Lone, Abdullah; Thomsen, Thomas T; Nielsen, Josefine Eilsø; Thulstrup, Peter W; Klitgaard, Rasmus N & Løbner-Olesen, Anders [Show all 9 contributors for this article] (2019). Structure-activity study of an all-D antimicrobial octapeptide D2D. Molecules. ISSN 1431-5157. 24(24). doi: 10.3390/molecules24244571. Full text in Research Archive
Nielsen, Josefine Eilsø; Lind, Tania Kjellerup; Lone, Abdullah; Gerelli, Yuri; Hansen, Paul Robert & Jenssen, Håvard [Show all 8 contributors for this article] (2019). A biophysical study of the interactions between the antimicrobial peptide indolicidin and lipid model systems. Biochimica et Biophysica Acta - Biomembranes. ISSN 0005-2736. 1861(7), p. 1355–1364. doi: 10.1016/j.bbamem.2019.04.003. Full text in Research Archive Show summary
The naturally occurring peptide indolicidin from bovine neutrophils exhibits strong biological activity against a broad spectrum of microorganisms. This is believed to arise from selective interactions with the negatively charged cytoplasmic lipid membrane found in bacteria. We have investigated the peptide interaction with supported lipid model membranes using a combination of complementary surface sensitive techniques: neutron reflectometry (NR), atomic force microscopy (AFM), and quartz crystal microbalance with dissipation monitoring (QCM-D). The data are compared with small-angle X-ray scattering (SAXS) results obtained with lipid vesicle/peptide solutions. The peptide membrane interaction is shown to be significantly concentration dependent. At low concentrations, the peptide inserts at the outer leaflet in the interface between the headgroup and tail core. Insertion of the peptide results in a slight decrease in the lipid packing order of the bilayer, although not sufficient to cause membrane thinning. By increasing the indolicidin concentration well above the physiologically relevant conditions, a deeper penetration of the peptide into the bilayer and subsequent lipid removal take place, resulting in a slight membrane thinning. The results suggest that indolicidin induces lipid removal and that mixed indolicidin-lipid patches form on top of the supported lipid bilayers. Based on the work presented using model membranes, indolicidin seems to act through the interfacial activity model rather than through the formation of stable pores.
Nielsen, Josefine Eilsø; Bjørnestad, Victoria Ariel & Lund, Reidar (2018). Resolving the structural interactions between antimicrobial peptides and lipid membranes using small-angle scattering methods: The case of indolicidin. Soft Matter. ISSN 1744-683X. 14(43), p. 8750–8763. doi: 10.1039/c8sm01888j. Full text in Research Archive
Nielsen, Josefine Eilsø; Zhu, Kaizheng; Sande, Sverre Arne; Kováčik, Lubomír; Cmarko, Dusan & Knudsen, Kenneth [Show all 7 contributors for this article] (2017). Structural and Rheological Properties of Temperature-Responsive Amphiphilic Triblock Copolymers in Aqueous Media. Journal of Physical Chemistry B. ISSN 1520-6106. 121(18), p. 4885–4899. doi: 10.1021/acs.jpcb.7b01174. Full text in Research Archive

View all works in NVA

Nielsen, Josefine Eilsø; Lund, Reidar; Knudsen, Kenneth Dahl & Jensen, Håvard (2020). Examining the Molecular Mechanism of Antimicrobial Peptides using Neutron and X-ray Scattering Techniques. Universitetet i Oslo. Full text in Research Archive Show summary
Antimicrobial peptides (AMPs) are found in Nature as a part of the innate immune system in a wide range of species, including humans. Because of the emerging concern of widespread antibiotic resistance new antibiotics are of great importance. AMPs have attracted considerable interest, but the exact molecular mechanism of these compounds is still an object of debate. AMPs have been hypothesised to cause pore formation, membrane-solubilisation, or changes to the overall membrane structures. Here we combine small angle X-ray/neutron scattering techniques, and neutron reflectometry to systematically study the effect of a broad selection of AMPs on lipid membranes. Our results reveal a general peptide-induced acceleration of lipid transport processes, without changes to the overall membrane structure or creation of organised pores. Enhanced lipid transport can be linked with rapid scrambling of the lipid composition which may trigger lethal signalling processes, and enhance ion transport. The reported membrane effects provide a plausible canonical mechanism of AMP-membrane interaction and may reconcile previously observed effects of AMPs on bacterial membranes.