Szymon Mikolaj Szostak

• Cezar, Henrique Musseli; Berton, Giacomo; Lorenzetto, Tommaso; Zorzi, Sandro; Foumthuim, Cedrix J. Dongmo & Szostak, Szymon Mikolaj [Show all 15 contributors for this article] (2026). Self-Assembly of Unconventional Triphenylene-Based Frustrated Amphiphile in Solution. Langmuir. ISSN 0743-7463. 42(6), p. 4507–4517. doi: 10.1021/acs.langmuir.5c05203. Full text in Research Archive Show summary

  Unconventional amphiphilic molecules having a rigid hydrophobic central unit and flexible or semiflexible hydrophilic chains on the rim have proven valuable in several technological applications, for example, host–guest chemistry. The further presence of alternating hydrophobic and hydrophilic tails complicates the definition of clear core and shell regions, resulting in complex segregation and frustrated self-assembly. In this study, we investigate symmetric triphenylene-based amphiphilic derivatives with alternating benzyl and alkylsulfonate groups. We characterize their self-assembly in water and different solutions using several experimental techniques, including NMR, atomic force microscopy, dynamic light scattering, and small-angle X-ray and neutron scattering, alongside extensive molecular dynamics simulations, including both atomistic and coarse-grained integrative modeling with metainference. In aqueous solutions, these amphiphiles form stacked assemblies, adopting alternate up–down conformations driven by π-stacking of up to six molecules. The introduction of NaCl salt screens unfavorable electrostatic interactions, thus promoting further π-stacking and leading to the formation of larger elongated aggregates.

• Lauretis, Angela de; Agger, Anne Eriksson; Pal, Antara; Pedersen, Jan Skov; Szostak, Szymon Mikolaj & Lund, Reidar [Show all 10 contributors for this article] (2025). Balancing sterilization and functional properties in Poloxamer 407 hydrogels: comparing heat and radiation techniques. Regenerative Biomaterials. 12. doi: 10.1093/rb/rbaf005. Full text in Research Archive Show summary

  Poloxamer 407, also known as Pluronic® F127, is gaining interest in the cosmetic, biomedical, and pharmaceutical fields for its biocompatibility, safety, and thermosensitive properties. Ensuring sterility is critical in clinical applications, and sterilization is often preferred over aseptic processing. However, sterilization can impact the hydrogel's functional properties. In this study, we investigate the effects of steam heat (121°C, 20 min), dry heat (160°C, 1 h), gamma irradiation (25 kGy), and electron beam (e-beam) irradiation (15 kGy and 25 kGy) on a 30%w/v Poloxamer 407 hydrogel formulation. Our analysis encompasses gelling properties, pH, Fourier-transform infrared (FTIR) spectroscopy, Gel Permeation Chromatography (GPC), Small-angle X-ray scattering (SAXS), rheology, swelling, degradation by-products, and lactate dehydrogenase (LDH) release of the sterilised hydrogels, comparing them to a non-sterile counterpart. We demonstrated that heat sterilisation alters the hydrogel’s gelling and structural properties due to water evaporation and oxidation under harsh temperature conditions, especially when applying the dry heat method. Gamma irradiation proved unsuitable, resulting in an acidic and cytotoxic hydrogel due to oxidative degradation. In contrast, e-beam irradiation preserves the hydrogel's elasticity, gelling, and structural properties while enhancing mechanical resilience and moderating swelling. Therefore, e-beam irradiation within the 15 – 25 kGy range appears to be the most suitable method for sterilizing a 30%w/v Poloxamer 407 hydrogel.

• Szostak, Szymon Mikolaj; König, Nico; Willner, Lutz & Lund, Reidar (2025). Modulating melting points in micellar cores: influence of the corona chain length on the core confinement in binary mixed block copolymer micelles. Soft Matter. ISSN 1744-683X. 21(10), p. 1895–1906. doi: 10.1039/d4sm01303d. Full text in Research Archive Show summary

  Self-assembly of polymers with crystallizable blocks may lead to micelles with ordered, gel-like or crystalline cores. Here we investigate binary mixtures of n-alkyl-poly(ethylene oxide), Cn-PEOx (n = 28, x = 3–20 kDa) and study their self-assembly to gain insight into the effect of confinement on the core-crystallization and micellar structure. By employing identical core block length but varying corona block lengths, the size of the core can be tuned by variation of the block ratios. The micelles were characterized by small-angle X-ray scattering (SAXS) to gain insight into the overall and internal structure, including aggregation number, core size, and density distribution of the corona. SAXS curves from examined samples showed a characteristic pattern of spherical core–shell micelles but with broader corona distribution in the binary mixtures as compared to the neat samples. The structural parameters of the micelles were extracted from the SAXS data by employing a spherical core–shell model with dual density profiles in the core. We found that the aggregation number decreases as PEO length increases following a power law predicted in the literature. Furthermore, the melting point and melting enthalpy of crystalline alkyl cores were closely inspected by densitometry and differential scanning calorimetry (DSC). Correlating the core radius obtained from SAXS, we found that the melting point depression caused by the self-confinement in the micellar core can be described by the Gibbs–Thomson equation. These results show that the micellar structure and phase transition of the semicrystalline core can be easily tuned through blending diblock copolymers with different corona block lengths.

• Vogelaar, Thomas Daniel; Szostak, Szymon Mikolaj & Lund, Reidar (2024). Coacervation in Slow Motion: Kinetics of Complex Micelle Formation Induced by the Hydrolysis of an Antibiotic Prodrug. Molecular Pharmaceutics. ISSN 1543-8384. doi: 10.1021/acs.molpharmaceut.4c00579. Full text in Research Archive Show summary

  Colistin methanesulfonate (CMS) is the less-toxic prodrug of highly nephrotoxic colistin. To develop and understand highly necessary new antibiotic formulations, the hydrolysis of CMS to colistin must be better understood. Herein, with the addition of poly(ethylene oxide)-b-poly(methacrylic acid) (PEO-b-PMAA) to CMS, we show that we can follow the hydrolysis kinetics, employing small-angle X-ray scattering (SAXS) through complex coacervation. During this hydrolysis, hydroxy methanesulfonate (HMS) groups from CMS are cleaved, while the newly formed cationic amino groups complex with the anionic charge from the PMAA block. As the hydrolysis of HMS groups is slow, we can follow the complex coacervation process by the gradual formation of complex micelles containing activated antibiotics. Combining mass spectrometry (MS) with SAXS, we quantify the hydrolysis as a function of pH. Upon modeling the kinetic pathways, we found that complexation only happens after complete hydrolysis into colistin and that the process is accelerated under acidic conditions. At pH = 5.0, effective charge switching was identified as the slowest step in the CMS conversion, constituting the rate-limiting step in colistin formation.

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