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Abstract: Magnetotactic bacteria, such as Magnetospirillum gryphiswaldense MSR-1, naturally produce magnetosomes—intracellular magnetic nanoparticles that enable navigation within geomagnetic fields. Magnetosomes hold significant potential for biomedical and biotechnological applications; however, key aspects of their biomineralization remain poorly understood. This study investigates how oxidative stress, induced by hydrogen peroxide and iron, influences magnetosome formation and bacterial physiology under aerobic and microaerobic conditions. Single-cell advanced microscopy and high-throughput techniques revealed that microaerobic conditions supported robust magnetosome production and larger magnetite crystals while maintaining low oxidative stress levels. In contrast, aerobic conditions suppressed magnetosome formation, reduced intracellular iron content, and increased reactive oxygen species (ROS) levels. High extracellular iron enhanced the formation of longer magnetosome chains in microaerobic cultures without causing toxicity but reduced cell viability under aerobic conditions. Hydrogen peroxide exposure caused mild damage and a 25% viability drop in magnetosome-producing cells but led to severe damage and an 80% viability drop in non-magnetosome-producing cells, along with chain fragmentation and smaller magnetite crystals. These results suggest that magnetosome-producing cells exhibit greater resilience to oxidative stress, potentially due to ROS scavenging properties of magnetosomes, and highlight the intricate interplay between oxidative stress, iron regulation, and magnetosome biomineralization. Single-cell analysis revealed heterogeneity in physiological responses, further demonstrating the complexity of these processes. These findings underscore the importance of monitoring physiological changes during production processes to enhance the efficiency and robustness of magnetosome synthesis. The insights gained provide a foundation for improving bioprocesses for large-scale production of high-quality magnetosomes, advancing their applications in biomedicine and biotechnology.

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Abstract: Peptide-based nanogels (NGs) represent a cutting-edge class of nanoscale drug delivery systems. Due to their structural properties, NGs platforms can encapsulate and protect therapeutic agents (e.g. peptides, proteins, and nucleic acids), while allowing for controlled and stimuli-responsive release. These pharmacokinetic and pharmacodynamic features can be specifically tuned by including peptide functional elements as NG components. This study explores the formulation, decoration strategies, and structural properties of NGs derived from mixed hydrogel (HG) matrices of Fmoc-diphenylalanine (Fmoc-FF) with cationic amphiphilic peptides (CAPs). CAPs, composed by cationic hexapeptide (GK)3 sequence decorated at its N-terminus with alkyl chain, were found able to confer a net positive charge to Fmoc-FF NGs. Fmoc-FF/C16-(GK)3 and Fmoc-FF/C18-(GK)3 NGs were obtained using polysorbate 80 (TWEEN 80) and sorbitane monooleate 80 (SPAN 80) as colloidal stabilizing surfactants and characterized in terms of size, secondary structure, superficial charge and shelf stability by Dynamic Light Scattering (DLS), Circular Dichroism (CD), Fourier Transform Infrared (FT-IR) and Small-Angle X-ray Scattering (SAXS) technique. Different formulative routes were used and mutually compared to encapsulate or adsorb AlexaFluor 430 (succinimidyl ester), used as model of an anionic, pharmaceutical agent. In vitro experiments demonstrated good cytocompatibility of these systems and the release of AlexaFluor 430 was also evaluated.

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Abstract: Pharmacological activation of STING holds promise in cancer treatment. A recent trend is the development of tumour-specific or conditionally activated STING agonists for enhanced safety and efficacy. Here we explore an unconventional prodrug activation strategy for on-tumour synthesis of a potent agonist. Leveraging the unique mechanism of MSA2, a small-molecule agonist that dimerizes non-covalently before binding to STING, we showed that its analogues bearing reactive functional groups readily and selectively form covalent dimers under mild conditions and in complex environments. We identified a reacting pair that led to a thioether-linked dimer with submicromolar potency in cell-based assays. Caging one of the reactants with a self-immolative β-glucuronide moiety resulted in a two-component prodrug system that near-exclusively formed the active compounds in tumours overexpressing β-glucuronidase. These results exemplify the use of small-molecule recognition for on-site generation of active compounds from benign precursors.

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Abstract: We report on the lyotropic phase behaviour of fully-hydrated mixtures of α-tocopherol (α-toc) with the unsaturated phospholipid dioleoyl phosphatidylcholine (DOPC), as studied by synchrotron small-angle x-ray diffraction. Increasing amounts of α-toc progressively swell the layer spacing of the fluid lamellar Lα phase of DOPC, and then induce a transition to an inverse hexagonal HII phase. Low-resolution electron density profiles show that this increase is largely due to an increased thickness of the bilayer, with little change in the water layer thickness. In the range 30 – 50 mol% α-toc, additional weak low-angle peaks were observed, whose characteristic ratios are in agreement with the presence of swollen inverse bicontinuous cubic phases of spacegroups Im3m / Pn3m. This research has applications both in the biological field and for industrial product development. We show that the effect of α-toc addition in DOPC membranes has some similarities to that of cholesterol by stabilizing inverse curvature structures, which play crucial roles in cell division, membrane trafficking and endocytosis. Concerning industrial applications, the stabilization of inverted hexagonal (HII) and swollen bicontinuous cubic phases offers the opportunity to develop new delivery systems.

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Abstract: Adequate drug solubility in the gastrointestinal tract is essential for systemic therapy of orally administered medications. In order to measure the solubility of poorly soluble drugs in vitro, simulated intestinal fluid (SIF) is often used in place of human intestinal fluid (HIF). A suite of fasted state SIF, based on variability observed in a range of fasted state HIF samples was designed and used to study the relationship between the solubility of eight poorly soluble biopharmaceutics classification system class II drugs and the particle size of the colloidal structures formed by the drugs in the fluid. The drugs of interest included three acidic drugs (naproxen, indomethacin and phenytoin), three neutral drugs (felodipine, fenofibrate, griseofulvin) and two basic drugs (carvedilol and tadalafil). The overall aim of this research is to work towards a better understanding of the colloidal structures formed in SIF. Solubility was measured using high performance liquid chromatography and results indicated that the solubility was typically greater in the acidic drugs than in the neutrals or bases and that the solubility tended to increase with increasing media point (pH × [TAC]). Particle size was determined using both dynamic light scattering and nanoparticle tracking analysis. Dynamic light scattering data confirmed the polydispersity of size distribution within the samples analysed. Typically, as the concentration of amphiphiles (total amphiphile concentration ([TAC])) is increased, the particle size of the structures measured decreases. A comparison with the solubility data revealed that the general trend indicated that while solubility is to some extent affected by pH and [TAC] or (pH × [TAC]), the relationship between solubility and particle size is linked with [TAC]. Small angle X-ray scattering (SAXS) analysis was carried out at the Diamond Light Source national facility, using the laboratory SAXS (labSAXS) beamline on drug and drug free SIF samples and the data was processed at the University of Strathclyde. Unfortunately, there was no significant scattering measured in the sample fluids which is thought to be a result of samples that are too weakly scattering to be detected by a labSAXS instrument. The data obtained serves as excellent preliminary data for a future beamtime application using a synchrotron beamline. The final work explores a model, using simple mathematics, to estimate the number of drug molecules per colloid or mixed micelle structure in a series of SIF. The experimental data, collected in earlier chapters, was applied in both this calculation and a calculation to estimate the solubility enhancement provided in the SIF media. Analysis of the data and results indicates that there is a direct relationship between particle size of the colloidal structures and the number of estimated drug molecules per structure. As expected, as the particle size decreases, as does the estimated number of drug molecules per micelle. The larger structures can accommodate a greater number of drug molecules per micelle. Solubility enhancement was also calculated, with the acidic drugs, naproxen and indomethacin proving to be most solubility enhanced in the suite of simulated intestinal fluid.