Material Substrate Physical Properties Control Pseudomonas aeruginosa Biofilm Architecture.

In the wild, bacteria are most frequently found in the form of multicellular structures called biofilms. Biofilms grow at the surface of abiotic and living materials with wide-ranging mechanical properties. The opportunistic pathogen Pseudomonas aeruginosa forms biofilms on indwelling medical devices and on soft tissues, including burn wounds and the airway mucosa. Despite the critical role of substrates in the foundation of biofilms, we still lack a clear understanding of how material mechanics regulate their architecture and the physiology of resident bacteria. Here, we demonstrate that physical properties of hydrogel material substrates define P. aeruginosa biofilm architecture. We show that hydrogel mesh size regulates twitching motility, a surface exploration mechanism priming biofilms, ultimately controlling the organization of single cells in the multicellular community. The resulting architectural transitions increase P. aeruginosa's tolerance to colistin, a last-resort antibiotic. In addition, mechanical regulation of twitching motility affects P. aeruginosa clonal lineages, so that biofilms are more mixed on relatively denser materials. Our results thereby establish material properties as a factor that dramatically affects biofilm architecture, antibiotic efficacy, and evolution of the resident population. IMPORTANCE The biofilm lifestyle is the most widespread survival strategy in the bacterial world. Pseudomonas aeruginosa biofilms cause chronic infections and are highly recalcitrant to antimicrobials. The genetic requirements allowing P. aeruginosa to grow into biofilms are known, but not the physical stimuli that regulate their formation. Despite colonizing biological tissues, investigations of biofilms on soft materials are limited. In this work, we show that biofilms take unexpected forms when growing on soft substrates. The physical properties of the material shape P. aeruginosa biofilms by regulating surface-specific twitching motility. Physical control of biofilm morphogenesis ultimately influences the resilience of biofilms to antimicrobials, linking physical environment with tolerance to treatment. Altogether, our work established that the physical properties of a surface are a critical environmental regulator of biofilm biogenesis and evolution.

Plant-Based Diets Improve Maternal-Fetal Outcomes in CKD Pregnancies.

Reducing protein intake in patients with chronic kidney disease (CKD) limits glomerular stress induced by hyperfiltration and can prevent the progression of kidney disease; data in pregnancy are limited. The aim of this study is to analyze the results obtained in CKD patients who followed a plant-based moderately protein-restricted diet during pregnancy in comparison with a propensity-score-matched cohort of CKD pregnancies on unrestricted diets. A total of 52 CKD pregnancies followed up with a protein-restricted plant-based diet (Torino, Italy) were matched with a propensity score based on kidney function and proteinuria with CKD pregnancies with unrestricted protein intake (Cagliari Italy). Outcomes included preterm (<37 weeks) and very preterm (<34 weeks) delivery and giving birth to a small-for-gestational-age baby. The median age in our cohort was 34 years, 63.46% of women were primiparous, and the median body mass index (BMI) was 23.15 kg/m2 with 13.46% of obese subjects. No statistical differences were found between women on a plant-based diet and women who were not in terms of age, parity, BMI, obesity, CKD stage, timing of referral, or cause of CKD. No differences were found between the two groups regarding the week of delivery. However, the combined negative outcome (birth before 37 completed gestational weeks or birth-weight centile <10) occurred less frequently in women following the diet than in women in the control group (61.54% versus 80.77%; p = 0.03). The lower risk was confirmed in a multivariable analysis adjusted for renal function and proteinuria (OR: 0.260 [Q1:0.093-Q3:0.724]; p = 0.010), in which the increase in proteinuria from the first to the last check-up before delivery was lower in patients on plant-based diets (median from 0.80 to 1.87 g/24 h; p: ns) than in controls (0.63 to 2.39 g/24 h p <0.0001). Plant-based, moderately protein-restricted diets in pregnancy in patients with CKD are associated with a lower risk of preterm delivery and small-for-gestational-age babies; the effect may be mediated by better stabilization of proteinuria.

Monodisperse Selectively Permeable Hydrogel Capsules Made from Single Emulsion Drops.

Capsules are often used to protect chemical and biological entities from the environment, to control the timing and location of their release, or to facilitate the collection of waste. Their performance depends on the thickness and composition of their shells, which can be closely controlled if capsules are made from double emulsion drops that are produced with microfluidics. However, the fabrication of such double emulsions is delicate, limiting throughput and increasing costs. Here, a fast, scalable method to produce monodisperse microcapsules possessing mechanically robust, thin, semipermeable hydrogel shells from single emulsion drops is introduced. This is achieved by selectively polymerizing reagents in close proximity to the drop surface to form a biocompatible 1.6 µm-thick hydrogel shell that encompasses a liquid core. The size-selective permeability of the shell enables the growth of living yeast and bacteria in their cores. Moreover, if capsules are loaded with adsorbents, they can repetitively remove waste products from water. The simplicity and robustness of the capsule fabrication makes the process scalable and cost effective. It has thus the potential to extend the use of calibrated capsules possessing well-defined dimensions to cost sensitive fields, including food, waste water treatment, or oil recovery.

Determining an energy threshold for optimal volume reduction of benign thyroid nodules treated by radiofrequency ablation.

OBJECTIVES: Radiofrequency ablation (RFA) is effective in reducing the volume of benign thyroid nodules. However, what parameters can influence the response to RFA is still unclear. The present study aimed to (1) investigate which ultrasound and technical parameters are potential determinants of the volumetric reduction; (2) develop a dose-response model, and (3) analyze the effects of RFA on ultrasound features. METHODS: In this retrospective study, three institutions treated patients with benign thyroid nodules according to the same protocol. The technical parameters were power and energy. The 1-year volume reduction ratio (VRR) was the reference standard of the response. The correlations of different parameters with VRR were analyzed and the association between several parameters and a VRR above 50% studied by uni- and multivariate analyses. The probit regression estimated the probability to achieve an effective response. RESULTS: One hundred fifteen patients were enrolled. The median power was 50 W and median total delivered energy 27,531 J. At 1-year follow-up, the median VRR was 64.0% and 87 (75.7%) nodules showed a VRR above 50%. Among all parameters, only baseline volume, total energy, and energy per volume were independently associated to a VRR > 50% (p = 0.001, p = 0.0178, p < 0.001 respectively). The probit regression analysis demonstrated that delivering 756 J/ml and 2670 J/ml gave a probability of VRR > 50% in 50% and 99% of patients, respectively. CONCLUSIONS: Considering the baseline nodular volume and delivering the adequate energy per volume allow optimizing technical and clinical success. KEY POINTS: • The effectiveness of radiofrequency ablation in treating benign thyroid nodules is negatively correlated to the volume of the nodule and positively correlated to the energy delivered per volume. • When planning the treatment, the total energy to deliver can be calculated by using a simple formula: nodular volume × 2670 J.

Biofilms deform soft surfaces and disrupt epithelia.

During chronic infections and in microbiota, bacteria predominantly colonize their hosts as multicellular structures called biofilms. A common assumption is that biofilms exclusively interact with their hosts biochemically. However, the contributions of mechanics, while being central to the process of biofilm formation, have been overlooked as a factor influencing host physiology. Specifically, how biofilms form on soft, tissue-like materials remains unknown. Here, we show that biofilms of the pathogens Vibrio cholerae and Pseudomonas aeruginosa can induce large deformations of soft synthetic hydrogels. Biofilms buildup internal mechanical stress as single cells grow within the elastic matrix. By combining mechanical measurements and mutations in matrix components, we found that biofilms deform by buckling, and that adhesion transmits these forces to their substrates. Finally, we demonstrate that V. cholerae biofilms can generate sufficient mechanical stress to deform and even disrupt soft epithelial cell monolayers, suggesting a mechanical mode of infection.

Complete inclusion of bioactive molecules and particles in polydimethylsiloxane: a straightforward process under mild conditions.

By applying a slow curing process, we show that biomolecules can be incorporated via a simple process as liquid stable phases inside a polydimethylsiloxane (PDMS) matrix. The process is carried out under mild conditions with regards to temperature, pH and relative humidity, and is thus suitable for application to biological entities. Fluorescence and enzymatic activity measurements show that the biochemical properties of the proteins and enzyme tested are preserved, without loss due to adsorption at the liquid-polymer interface. Protected from external stimuli by the PDMS matrix, these soft liquid composite materials are new tools of interest for robotics, microfluidics, diagnostics and chemical microreactors.

Fabrication of Hexagonal-Prismatic Granular Hydrogel Sheets.

Natural soft materials are often composed of proteins that self-assemble into well-defined structures and display mechanical properties that cannot be matched by manmade materials. These materials are frequently mimicked with hydrogels whose mechanical properties depend on their composition and the type and density of cross-links. Protocols to tune these parameters are well established and routinely used. The mechanical properties of hydrogels also depend on their structure; this parameter is more difficult to control. In this paper, we present a method to produce hexagonal-prismatic granular hydrogel sheets with well-defined structures and heterogeneous cross-link densities. The hydrogel sheets are made of self-assembled covalently cross-linked 40-120 µm diameter hexagonal-prismatic hydrogel particles that display a narrow size distribution. The structure and microscale surface roughness of the hydrogels sheets can be tuned with the polymerization conditions, their chemical composition with that of the individual hydrogel particles, and their mechanical properties with the cross-link density. Remarkably, the hydrogels composed of hexagonal-prismatic microparticles are significantly stiffer than unstructured counterparts. These results demonstrate that the stiffness of hydrogels can be tuned by controlling their micrometer-scale structure without altering their composition. Thereby, they open up new possibilities to design soft materials whose performance more closely resembles that of natural ones.