02240nas a2200121   4500008004100000022001400041245011300055210006900168300001100237490000700248520179100255856007202046       2026                        eng d  a2468-233000aMicro-compression analysis of biopolymer-producing bacteria using Cupriavidus necator as the model bacterium0 aMicrocompression analysis of biopolymerproducing bacteria using   a1001710 v153 a<p>With the development of highly sensitive experimental techniques, the mechanical properties of bacterial cells have become an important research topic. However, existing models used to fit experimental data from micro-compression tests often lack accuracy. The aim of this study was to address this limitation by developing a new curve-fitting mathematical model for evaluating the mechanical properties of rod-shaped bacterial cells. The proposed model is based on a thin-shell approach and is specifically designed for the interpretation of single-cell micro-compression experiments. To verify the applicability of the model, single-cell micro-compression tests were performed using a flat-punch nanoindenter tip larger than the bacterial cells. Atomic force microscopy (AFM) was used to obtain detailed morphological information, including precise cell dimensions required for curve fitting. As a model organism, the polyhydroxyalkanoate-producing bacterium Cupriavidus necator H16 was selected due to its ability to accumulate intracellular polyhydroxybutyrate (PHB) granules. For comparison, a mutant strain, C. necator PHB−4, which lacks PHB production, was also analyzed. The results showed that C. necator H16 cells, with an average PHB content of 72% of dry cell weight, exhibited a Young's modulus approximately 16× higher than that of the PHB−4 mutant, indicating a substantial contribution of intracellular PHB granules to cell stiffness. AFM analysis further revealed that PHB-producing cells were, on average, larger in volume than the non-producing mutant. The combination of AFM and micro-compression testing enabled comprehensive characterization of bacterial cell mechanics and demonstrated a clear correlation between PHB content and mechanical behaviour.</p>  uhttps://www.sciencedirect.com/science/article/pii/S246823302600004601902nas a2200121   4500008004100000022001400041245010000055210006900155300001100224490000800235520146500243856007201708       2025                        eng d  a0141-813000aMultiscale analysis of mechanical and structural properties of agarose–silk fibroin hydrogels0 aMultiscale analysis of mechanical and structural properties of a  a1481330 v3303 a<p>This study provides a comprehensive characterization of the agarose–silk fibroin hydrogels, using atomic force microscopy and scanning transmission electron microscopy to analyse their structure and assess the effect of composition on mechanical properties via nanoindentation and rheological analysis. These measurements enabled determination of mechanical properties, including the elastic and viscoelastic moduli at both the micro- and macroscale. The hydrogels exhibited a wide range of moduli depending on different degrees of network crosslinking, influenced by varying concentrations of agarose (1 or 2&nbsp;wt%) and the percentage of fibroin fibres (0–4.5&nbsp;wt%) as an interpenetrating component. The viscoelastic modulus (G') and the elastic modulus determined using a relaxation model (E), were 5–57&nbsp;kPa and 1.2–110&nbsp;kPa, respectively. The adhesion energy of these hydrogels was determined from nanoindentation curves and analysed using the JKR model, with values ranging from 0.031 to 0.066&nbsp;J&nbsp;m−2. These results provide insight into how the hydrogels' microstructure influences their mechanical and transport properties. Incorporating fibroin into these gels modifies biological and biochemical characteristics of the gels, suggesting that such composite hydrogels could be further explored for potential applications in controlled release systems, extracellular matrix models, or tissue engineering scaffolds.</p>  uhttps://www.sciencedirect.com/science/article/pii/S0141813025086908