The collective self-organization of cells into three-dimensional structures can give rise to emergent physical properties such as fluid behavior. Here, we demonstrate that tissues growing on curved surfaces develop shapes with outer boundaries of constant mean curvature, similar to the energy minimizing forms of liquids wetting a surface. The amount of tissue formed depends on the shape of the substrate, with more tissue being deposited on highly concave surfaces, indicating a mechano-biological feedback mechanism. Inhibiting cell-contractility further revealed that active cellular forces are essential for generating sufficient surface stresses for the liquid-like behavior and growth of the tissue. This suggests that the mechanical signaling between cells and their physical environment, along with the continuous reorganization of cells and matrix is a key principle for the emergence of tissue shape.

Outbreaks of foodborne diseases are regularly reported worldwide. In particular, uncooked plant food is considered risky in terms of microbiological safety. Food is also the most important transmission route for resistant microorganisms from animals to humans. Photodynamic Decontamination (PDc) of foodstuff was recently introduced as a novel approach for increasing microbiological food safety. We investigated the efficiency of PDc on plant food with different geometries (flat, spherical and complex) using a two-dimensional LED array as a light source (435 nm, 33.8 J cm) and the cationic curcumin derivative SACUR-3 as a photosensitiser. A photoantibacterial effect (>3 log CFU reduction) was achieved on all flat substrates (slices of cucumber, tomato and lettuce) with 10 μM, 50 μM or 100 μM SACUR-3. The maximal photokilling with a relative inactivation of 5.6 log was measured on lettuce using 50 μM of the photoactive compound. Phototreatment of non-germinated fenugreek seeds and mung beans was successful if the spherical objects were rotated while under illumination (antibacterial effect at 100 μM SACUR-3). The decontamination of mung bean germlings with a more complex geometry using the PDc approach was ineffective with the two-dimensional light source. In conclusion, PDc based on the cationic curcumin derivative SACUR-3 is very effective at improving the microbiological safety of plant food with a flat or spherical geometry. More complex objects will require the development of novel illumination devices.

Surface curvature both emerges from, and influences the behavior of, living objects at length scales ranging from cell membranes to single cells to tissues and organs. The relevance of surface curvature in biology has been supported by numerous recent experimental and theoretical investigations in recent years. In this review, we first give a brief introduction to the key ideas of surface curvature in the context of biological systems and discuss the challenges that arise when measuring surface curvature. Giving an overview of the emergence of curvature in biological systems, its significance at different length scales becomes apparent. On the other hand, summarizing current findings also shows that both single cells and entire cell sheets, tissues or organisms respond to curvature by modulating their shape and their migration behavior. Finally, we address the interplay between the distribution of morphogens or micro-organisms and the emergence of curvature across length scales with examples demonstrating these key mechanistic principles of morphogenesis. Overall, this review highlights that curved interfaces are not merely a passive by-product of the chemical, biological and mechanical processes but that curvature acts also as a signal that co-determines these processes.

Fungal infections in humans, contamination of food and structural damage to buildings by fungi are associated with high costs for the general public. In addition, the increase in antifungal resistance towards conventional treatment raises the demand for new fungicidal methods. Here, we present the antifungal use of Photodynamic Inactivation (PDI) based on the natural photosensitizer curcumin and a water-soluble positively charged derivative thereof (SA-CUR 12a) against two different model organisms; Candida albicans grown in a liquid culture and photo treated with a 435 nm LED light followed by counting of the colony-forming units and photoinactivation of tissue-like hyphal spheres of Aspergillus niger (diameter ~5 mm) with subsequent monitoring of colony growth. Curcumin (50 µM, no incubation period, i.p.) supplemented with 10% or 0.5% DMSO as well as SA-CUR 12a (50 µM no i.p or 5 min i.p.) triggered a photoantifungal effect of >4 log units towards C. albicans. At 100 µM, SA-CUR 12a (0 min or 5 min i.p.) achieved a reduction of >6 log units. Colonies of A. niger shrunk significantly during PDI treatment. Photoinactivation with 50 µM or 100 µM curcumin (+0.5% DMSO) resulted in complete growth inhibition. PDI using 20, 50 or 100 µM SA-CUR 12a (with or without 10% DMSO) also showed a significant reduction in colony area compared to the control after 48 h, although less pronounced compared to curcumin. In summary, PDI using curcumin or SA-CUR 12a against C. albicans or A. niger is a promising alternative to currently used fungicides, with the advantage of being very unlikely to induce resistance.

Next generation electronic devices like single electron transistors (SETs) operating at room temperature (RT) demand for high-resolution patterning techniques and simultaneously cost-effective, high-throughput manufacturing. Thereby, field-emission scanning probe lithography (FE-SPL) is a direct writing method providing high-resolution and high-quality nanopatterns. SET devices prepared by FE-SPL and plasma etching at cryogenic substrate temperature were shown to operate at RT [C. Lenk et al., Microelectron. Eng. 192, 77 (2018); Z. Durrani, M. Jones, F. Abualnaja, C. Wang, I. W. Rangelow, M. Kaestner, S. Lenk, C. Lenk, and A. Andreev, J. Appl. Phys. 124, 144502 (2018); I. W. Rangelow et al., J. Vac. Sci. Technol. B 34, 06K202 (2016)]. Nevertheless, FE-SPL lacks in writing speed and large area manufacturing capability required for industrial device manufacturing. This can be overcome by combining FE-SPL with nanoimprint lithography (NIL), which enables the replication of high-resolution features on large areas and provides high throughput. In this work, the authors will review a high-throughput process chain for RT-SET fabrication based on reproducing FE-SPL prepared masters by NIL and etching.

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