Probing the nanoadhesion of Streptococcus sanguinis to titanium implant surfaces by atomic force microscopy

The authors would kindly like to thank the BecasChile PhD Scholarship Programme for funding this research

The mechanobiology of tendon fibroblasts under static and uniaxial cyclic load in a 3D tissue engineered model mimicking native ECM

Tendon mechanobiology plays a vital role in tendon repair and regeneration; however, this mechanism is currently poorly understood. We tested the role of different mechanical loads on extracellular matrix (ECM) remodelling gene expression and the morphology of tendon fibroblasts in collagen hydrogels, designed to mimic native tissue. Hydrogels were subjected to precise static or uniaxial loading patterns of known magnitudes and sampled to analyse gene expression of known mechano‐responsive ECM‐associated genes (Collagen I, Collagen III, Tenomodulin, and TGF‐β). Tendon fibroblast cytomechanics was studied under load by using a tension culture force monitor, with immunofluorescence and immunohistological staining used to examine cell morphology. Tendon fibroblasts subjected to cyclic load showed that endogenous matrix tension was maintained, with significant concomitant upregulation of ECM remodelling genes, Collagen I, Collagen III, Tenomodulin, and TGF‐β when compared with static load and control samples. These data indicate that tendon fibroblasts acutely adapt to the mechanical forces placed upon them, transmitting forces across the ECM without losing mechanical dynamism. This model demonstrates cell‐material (ECM) interaction and remodelling in preclinical a platform, which can be used as a screening tool to understand tendon regeneration

Trophic signature of coral reef fish assemblages : towards a potential indicator of ecosystem disturbance

Face to the increasing anthropogenic disturbances that affect coral reef ecosystems, it becomes urgent to define appropriate ecological indicators for monitoring purposes. One useful approach is to search for a simplified description of the structure of biological communities that are highly diverse and complex on coral reefs. To this end, we propose to represent the trophic structure of coral reef fish assemblages by using fractional trophic levels assigned to each fish species. Fish abundance trophic spectra (i.e., the distributions of fish abundance per trophic level) were established for the fringing reefs of two bays located in the city of Noumea (New Caledonia). The comparison of these trophic spectra revealed a similar trophic structure in the two bays, in spite of contrasted levels of fish abundance due to habitat damages. The embayment degree was characterized by changes in the fish trophic structure, reflecting a decreasing influence of urban and industrial wastes discharged in the bottom of the bays. This case of study shows the interest of using fractional trophic levels for the description of highly diverse biological communities. The trophic level-based approach offers new prospects in the search for ecological indicators, by characterizing the structure of biological communities by trophic signatures which testify to the disturbance level affecting their environment

A Multi-scale Biophysical Approach to Develop Structure-Property Relationships in Oral Biofilms

Over the last 5-10 years, optical coherence tomography (OCT) and atomic force microscopy (AFM) have been individually applied to monitor the morphological and mechanical properties of various single-species biofilms respectively. This investigation looked to combine OCT and AFM as a multi-scale approach to understand the role sucrose concentration and age play in the morphological and mechanical properties of oral, microcosm biofilms, in-vitro. Biofilms with low (0.1% w/v) and high (5% w/v) sucrose concentrations were grown on hydroxyapatite (HAP) discs from pooled human saliva and incubated for 3 and 5 days. Distinct mesoscale features of biofilms such as regions of low and high extracellular polymeric substances (EPS) were identified through observations made by OCT. Mechanical analysis revealed increasing sucrose concentration decreased Young's modulus and increased cantilever adhesion (p < 0.0001), relative to the biofilm. Increasing age was found to decrease adhesion only (p < 0.0001). This was due to mechanical interactions between the indenter and the biofilm increasing as a function of increased EPS content, due to increasing sucrose. An expected decrease in EPS cantilever contact decreased adhesion due to bacteria proliferation with biofilm age. The application OCT and AFM revealed new structure-property relationships in oral biofilms, unattainable if the techniques were used independently

A simple and robust method for pre-wetting poly (lactic-co-glycolic) acid microspheres

Poly (lactic-co-glycolic) acid microspheres are amenable to a number of biomedical procedures that support delivery of cells, drugs, peptides or genes. Hydrophilisation or wetting of poly (lactic-co-glycolic) acid are an important pre-requisites for attachment of cells and can be achieved via exposure to plasma oxygen or nitrogen, surface hydrolysis with NaOH or chloric acid, immersion in ethanol and water, or prolonged incubation in phosphate buffered saline or cell culture medium. The aim of this study is to develop a simple method for wetting poly (lactic-co-glycolic) acid microspheres for cell delivery applications. A one-step ethanol immersion process that involved addition of serum-supplemented medium and ethanol to PLGA microspheres over 30 min–24 h is described in the present study. This protocol presents a more efficient methodology than conventional two-step wetting procedures. Attachment of human skeletal myoblasts to poly (lactic-co-glycolic) acid microspheres was dependent on extent of wetting, changes in surface topography mediated by ethanol pre-wetting and serum protein adsorption. Ethanol, at 70% (v/v) and 100%, facilitated similar levels of wetting. Wetting with 35% (v/v) ethanol was only achieved after 24 h. Pre-wetting (over 3 h) with 70% (v/v) ethanol allowed significantly greater (p ≤ 0.01) serum protein adsorption to microspheres than wetting with 35% (v/v) ethanol. On serum protein-loaded microspheres, greater numbers of myoblasts attached to constructs wetted with 70% ethanol than those partially wetted with 35% (v/v) ethanol. Microspheres treated with 70% (v/v) ethanol presented a more rugose surface than those treated with 35% (v/v) ethanol, indicating that more efficient myoblast adhesion to the former may be at least partially attributed to differences in surface structure. We conclude that our novel protocol for pre-wetting poly (lactic-co-glycolic) acid microspheres that incorporates biochemical and structural features into this biomaterial can facilitate myoblast delivery for use in clinical settings.This project was supported by grants from the UK Medical Research Council (MR/L002752/1) and Sir Halley Stewart Trust. The research was undertaken at UCL/UCLH which receives funding from the Department of Health’s NIHR as a Comprehensive Biomedical Research Centre.Published versio

Deuterium-Stabilized (R)-Pioglitazone, PXL065, for Treatment of X-Linked Adrenoleukodystrophy (ALD)

Background and aims: X-linked Adrenoleukodystrophy (ALD) is a rare neurometabolic disorder caused by ABCD1- gene mutations, leading to Very-Long-Chain Fatty Acids (VLCFA; in particular C26:0) accumulation, inflammation, mitochondrial impairment and demyelination. PXL065, a clinical-stage deuterium-stabilized(R)-stereoisomer of pioglitazone, retains pioglitazone non-genomic actions but lacks PPARγ activity. As pioglitazone exhibits beneficial effects in ALD models and PXL065 may avoid PPARγ- related side effects, we investigated PXL065 effects of in preclinical models. Methods: Patient-derived fibroblasts and lymphocytes and Abcd1-KO mouse glial cells were exposed to PXL065 (5-10μM) and pioglitazone (10μM) for 7 days. VLCFA content was measured by mass spectrometry, selected gene expression by RT-qPCR, and mitochondrial function using a Seahorse Analyzer (after 72hr). PXL065 or pioglitazone (15mg/kg QD) were administered to 6-8-week or 13-month old Abcd1-KO mice for 8 and 12 weeks, respectively. VLCFA content (mass spectrometry), sciatic nerve axonal morphology (electronic microscopy), and locomotor function (open field test) were measured. Results: In patient and mouse glial cells, PXL065 and pioglitazone corrected C26:0, improved mitochondrial function, increased compensatory Abcd2-3 transporter gene expression, and decreased inflammatory gene expression. In Abcd1-KO mice, C26:0 levels were normalized in plasma and decreased in spinal cord (-55%, p\u3c0.01) and brain (-49%, p\u3c0.0001). Pioglitazone had no effect in spinal cord. Following PXL065 and pioglitazone treatment, abnormal axonal morphology (stellate-shaped cells) was improved but only PXL065 showed significantly improved locomotor test results. Conclusion: Despite reduced PPARγ activity, PXL065 showed substantial signs of efficacy and superior therapeutic potential vs. pioglitazone (in vivo) supporting clinical development for ALD. A Phase 2a study is planned in 2022

Single-bacterium nanomechanics in biomedicine: unravelling the dynamics of bacterial cells.

The use of the atomic force microscope (AFM) in microbiology has progressed significantly throughout the years since its first application as a high-resolution imaging instrument. Modern AFM setups are capable of characterizing the nanomechanical behaviour of bacterial cells at both the cellular and molecular levels, where elastic properties and adhesion forces of single bacterium cells can be examined under different experimental conditions. Considering that bacterial and biofilm-mediated infections continue to challenge the biomedical field, it is important to understand the biophysical events leading towards bacterial adhesion and colonization on both biological and non-biological substrates. The purpose of this review is to present the latest findings concerning the field of single-bacterium nanomechanics, and discuss future trends and applications of nanoindentation and single-cell force spectroscopy techniques in biomedicine

Contrasted photochromic and luminescent properties in dinuclear Pt(II) complexes linked through a central dithienylethene unit

We disclose two unprecedented complexes built with a central dithienylethene photochrome connecting two cyclometalated Pt(ii) moieties either on the reactive carbon atoms or on the lateral non-reactive carbon atoms of the photochrome. The two systems show vastly different properties that are rationalised thanks to quantum-chemical calculations