Effect of artificial aging on optical properties and crystalline structure of high-translucency zirconia

PURPOSE

To investigate the effect of different in vitro aging protocols on the optical properties and crystalline structure of high-translucency (HT) zirconia.

MATERIALS AND METHODS

Thirty-six specimens of HT and extra-high translucency (XT) zirconia were divided into three groups: control (CO)-no treatment; hydrothermal aging (HA)-autoclave aging for 12.5 h at 134°C, 2 bar; clinically related aging (CRA)-aging in the chewing simulator for 1.2 million cycles, followed by 50,000 thermocycles (5-55°C) and immersion in HCl (pH 1.2) for 15 h. Optical properties, crystalline structure, and surface roughness were analyzed and compared using analysis of variance (5% significance level).

RESULTS

There was no statistically significant effect of aging on translucency (p = 0.10), but CRA promoted the development of a high contrast ratio (p = 0.03). Aging did not cause significant color changes for HT (p = 0.65) or XT (p = 0.36). The proportion of monoclinic crystals increased to 40% for HT-zirconia after HA and 5% after CRA. No monoclinic crystals were detected for XT groups. There was no effect of aging on surface roughness (p = 0.77).

CONCLUSIONS

Although hydrothermal aging has been widely used to verify zirconia crystalline stability, it did not generate an effect similar to clinically related aging on the optical properties and crystalline structure of zirconia. HA affected the crystalline structure of HT-zirconia, and CRA compromised the optical properties of XT zirconia.

Development of a facile method to compute collagen network pathological anisotropy using AFM imaging

Type I collagen, a fundamental extracellular matrix (ECM) component, is pivotal in maintaining tissue integrity and strength. It is also the most prevalent fibrous biopolymer within the ECM, ubiquitous in mammalian organisms. This structural protein provides essential mechanical stability and resilience to various tissues, including tendons, ligaments, skin, bone, and dentin. Collagen has been structurally investigated for several decades, and variation to its ultrastructure by histology has been associated with several pathological conditions. The current study addresses a critical challenge in the field of collagen research by providing a novel method for studying collagen fibril morphology at the nanoscale. It offers a computational approach to quantifying collagen properties, enabling a deeper understanding of how collagen type I can be affected by pathological conditions. The application of Fast Fourier Transform (FFT) coupled with Atomic Force Microscope (AFM) imaging distinguishes not only healthy and diseased skin but also holds potential for automated diagnosis of connective tissue disorders (CTDs), contributing to both clinical diagnostics and fundamental research in this area. Here we studied the changes in the structural parameters of collagen fibrils in Ehlers Danlos Syndrome (EDS). We have used skin extracted from genetically mutant mice that exhibit EDS phenotype as our model system (Col1a1Jrt/+ mice). The collagen fibrils were analyzed by AFM based descriptive-structural parameters, coupled with a 2D Fast Fourier Transform(2D-FFT) approach that automated the analysis of AFM images. In addition, each sample was characterized based on its FFT and power spectral density. Our qualitative data showed morphological differences in collagen fibril clarity (clearness of the collagen fibril edge with their neighbouring fibri), D-banding, orientation, and linearity. We have also demonstrated that FFT could be a new tool for distinguishing healthy from tissues with CTDs by measuring the disorganization of fibrils in the matrix. We have also employed FFT to reveal the orientations of the collagen fibrils, providing clinically relevant phenotypic information on their organization and anisotropy. The result of this study can be used to develop a new automated tool for better diagnosis of CTDs.

Quantitative nanohistology of aging dermal collagen

The skin is the largest organ in the body and is essential for protecting us from environmental stressors such as UV radiation, pollution, and pathogens. As we age, our skin undergoes complex changes that can affect its function, appearance, and health. These changes result from intrinsic (chronological) and extrinsic (environmental) factors that can cause damage to the skin's cells and extracellular matrix. As higher-resolution microscopical techniques, such as Atomic Force Microscopy (AFM), are being deployed to support histology, it is possible to explore the biophysical properties of the dermal scaffold's constituents, such as the collagen network. In this study, we demonstrate the use of our AFM-based quantitative nanohistology, performed directly on unfixed cryosections of 30 donors (female, Caucasian), to differentiate between dermal collagen from different age groups and anatomical sites. The initial 420 (10 × 10 μm²) Atomic Force Microscopy images were segmented into 42,000 (1 × 1 μm²) images before being classified according to four pre-defined empirical collagen structural biomarkers to quantify the structural heterogeneity of the dermal collagen. These markers include interfibrillar gap formation, undefined collagen structure, and registered or unregistered dense collagen fibrillar network with evident D-banding. The structural analysis was also complemented by extensive nanoindentation (∼1,000 curves) performed on individual fibrils from each section, yielding 30,000 indentation curves for this study. Principal Component Analysis was used to reduce the complexity of high-dimensional datasets. The % prevalence of the empirical collagen structural biomarkers between the papillary and reticular dermis for each section proves determinant in differentiating between the donors as a function of their age or the anatomical site (cheek or breast). A case of abnormal biological aging validated our markers and nanohistology approach. This case also highlighted the difference between chronological and biological aging regarding dermal collagen phenotyping. However, quantifying the impact of chronic and pathological conditions on the structure and function of collagen at the sub-micron level remains challenging and lengthy. By employing tools such as the Atomic Force Microscope as presented here, it is possible to start evaluating the complexity of the dermal matrix at the nanoscale and start identifying relevant collagen morphology which could be used toward histopathology standards.

Correction: Enhanced detoxification of Cr6+ by Shewanella oneidensis via adsorption on spherical and flower-like manganese ferrite nanostructures

[This corrects the article DOI: 10.1039/D2NA00691J.].

Enhanced detoxification of Cr6+ by Shewanella oneidensis via adsorption on spherical and flower-like manganese ferrite nanostructures

Maximizing the safe removal of hexavalent chromium (Cr6+) from waste streams is an increasing demand due to the environmental, economic and health benefits. The integrated adsorption and bio-reduction method can be applied for the elimination of the highly toxic Cr6+ and its detoxification. This work describes a synthetic method for achieving the best chemical composition of spherical and flower-like manganese ferrite (MnxFe3-xO4) nanostructures (NS) for Cr6+ adsorption. We selected NS with the highest adsorption performance to study its efficiency in the extracellular reduction of Cr6+ into a trivalent state (Cr3+) by Shewanella oneidensis (S. oneidensis) MR-1. MnxFe3-xO4 NS were prepared by a polyol solvothermal synthesis process. They were characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), dynamic light scattering (DLS) and Fourier transform-infrared (FTIR) spectroscopy. The elemental composition of MnxFe3-xO4 was evaluated by inductively coupled plasma atomic emission spectroscopy. Our results reveal that the oxidation state of the manganese precursor significantly affects the Cr6+ adsorption efficiency of MnxFe3-xO4 NS. The best adsorption capacity for Cr6+ is 16.8 ± 1.6 mg Cr6+/g by the spherical Mn0.22+Fe2.83+O4 nanoparticles at pH 7, which is 1.4 times higher than that of Mn0.8Fe2.2O4 nanoflowers. This was attributed to the relative excess of divalent manganese in Mn0.22+Fe2.83+O4 based on our XPS analysis. The lethal concentration of Cr6+ for S. oneidensis MR-1 was 60 mg L-1 (determined by flow cytometry). The addition of Mn0.22+Fe2.83+O4 nanoparticles to S. oneidensis MR-1 enhanced the bio-reduction of Cr6+ 2.66 times compared to the presence of the bacteria alone. This work provides a cost-effective method for the removal of Cr6+ with a minimum amount of sludge production.

Nanoscale Dynamics of Streptococcal Adhesion to AGE-Modified Collagen

The adhesion of initial colonizers such as Streptococcus mutans to collagen is critical for dentinal and root caries progression. One of the most described pathological and aging-associated changes in collagen-including dentinal collagen-is the generation of advanced glycation end-products (AGEs) such as methylglyoxal (MGO)-derived AGEs. Despite previous reports suggesting that AGEs alter bacterial adhesion to collagen, the biophysics driving oral streptococcal attachment to MGO-modified collagen remains largely understudied. Thus, the aim of this work was to unravel the dynamics of the initial adhesion of S. mutans to type I collagen in the presence and absence of MGO-derived AGEs by employing bacterial cell force spectroscopy with atomic force microscopy (AFM). Type I collagen gels were treated with 10 mM MGO to induce AGE formation, which was characterized with microscopy and enzyme-linked immunosorbent assay. Subsequently, AFM cantilevers were functionalized with living S. mutans UA 159 or Streptococcus sanguinis SK 36 cells and probed against collagen surfaces to obtain force curves displaying bacterial attachment in real time, from which the adhesion force, number of events, Poisson analysis, and contour and rupture lengths for each individual detachment event were computed. Furthermore, in silico computer simulation docking studies between the relevant S. mutans UA 159 collagen-binding protein SpaP and collagen were computed, in the presence and absence of MGO. Overall, results showed that MGO modification increased both the number and adhesion force of single-unbinding events between S. mutans and collagen, without altering the contour or rupture lengths. Both experimental and in silico simulations suggest that this effect is due to increased specific and nonspecific forces and interactions between S. mutans UA 159 and MGO-modified collagen substrates. In summary, these results suggest that collagen alterations due to aging and glycation may play a role in early bacterial adherence to oral tissues, associated with conditions such as aging or chronic hyperglycemia, among others.

Modulation of the biophysical and biochemical properties of collagen by glycation for tissue engineering applications

The structural and functional properties of collagen are modulated by the presence of intramolecular and intermolecular crosslinks. Advanced Glycation End-products (AGEs) can produce intermolecular crosslinks by bonding the free amino groups of neighbouring proteins. In this research, the following hypothesis is explored: The accumulation of AGEs in collagen decreases its proteolytic degradation rates while increasing its stiffness. Fluorescence Lifetime Imaging (FLIM) and Fourier-transform infrared spectroscopy (FTIR) detect biochemical changes in collagen scaffolds during the glycation process. The accumulation of AGEs increases exponentially in the collagen scaffolds as a function of Methylglyoxal (MGO) concentration by performing autofluorescence measurement and competitive ELISA. Glycated scaffolds absorb water at a much higher rate confirming the direct affinity between AGEs and interstitial water within collagen fibrils. In addition, the topology of collagen fibrils as observed by Atomic Force Microscopy (AFM) is a lot more defined following glycation. The elastic modulus of collagen fibrils decreases as a function of glycation, whereas the elastic modulus of collagen scaffolds increases. Finally, the enzymatic degradation of collagen by bacterial collagenase shows a sigmoidal pattern with a much slower degradation rate in the glycated scaffolds. This study identifies unique variations in the properties of collagen following the accumulation of AGEs. STATEMENT OF SIGNIFICANCE: In humans, Advanced Glycation End-products (AGEs) are naturally produced as a result of aging process. There is an evident lack of knowledge in the basic science literature explaining the biomechanical impact of AGE-mediated crosslinks on the functional and structural properties of collagen at both the nanoscale (single fibrils) and mesoscale (bundles of fibrils). This research, demonstrates how it is possible to harness this natural phenomenon in vitro to enhance the properties of engineered collagen fibrils and scaffolds. This study identifies unique variations in the properties of collagen at nanoscale and mesoscale following accumulation of AGEs. In their approach, they investigate the unique properties conferred to collagen, namely enhanced water sorption, differential elastic modulus, and finally sigmoidal proteolytic degradation behavior.

Violin Varnishes: Microstructure and Nanomechanical Analysis

The aim of the current work is twofold: to demonstrate the application of in situ non-invasive imaging by portable atomic force microscopy (AFM) on the surfaces of a violin and to integrate compositional and mechanical analysis at the nano scale level on model samples of varnished wood. These samples were prepared according to traditional recipes by an Italian lute-maker family well practised in the art. Samples of oil and spirit-based varnishes on maple wood, naturally and accelerated light aged, were studied. AFM was used to measure the nanomechanical properties of the model samples and established that the spirit-based varnish was stiffer than the oil-based. Synchrotron radiation micro- Fourier Transform Infra-red analysis of the layer structure revealed that stiffer spirit-based varnish showed less penetration into the wood than the oil-based. Further PeakForce Quantitative Nanomechanical Mapping (QNM) demonstrated a difference in adhesion values between the oil- and spirit-based samples.

Insights From the NANOforArt Project: Application of Calcium-Based Nanoparticle Dispersions for Improved Preservation of Parchment Documents

Following pilot testing of the effects of alkaline-based nanoparticles on modern parchment, the treatment was extended to historical parchment. This paper describes the application and impact of calcium hydroxide and calcium carbonate nanoparticles dispersed in (i) propan-2-ol and (ii) cyclohexane on a parchment book cover dated 1570. The cover showed signs of damage resulting from contact with iron gall inks and low pH values (∼4–5). Protocols for the damage assessment of collagen in parchment as developed in the IDAP project (Improved Damage Assessment of Parchment) were used to evaluate the impact of the conservation treatments on parchment. Preliminary results have shown that the application of calcium-based nanoparticles did not produce any adverse effects on the state of preservation of collagen. In addition, positive outcomes emerged: the pH was re-adjusted to a neutral value, a strengthening and consolidation effect was observed, and the nanoparticles exhibited a protective action upon artificial ageing of the treated parchment.

Protocol for a Case Control Study to Evaluate Oral Health as a Biomarker of Child Exposure to Adverse Psychosocial Experiences

Background: The early identification of children who have experienced adversity is critical for the timely delivery of interventions to improve coping and reduce negative consequences. Self-report is the usual practice for identifying children with exposure to adversity. However, physiological characteristics that signal the presence of disease or other exposures may provide a more objective identification strategy. This protocol describes a case–control study that assesses whether exposure to adversity is more common in children with tooth enamel anomalies compared to children without such anomalies. Methods: For 150 mother–child pairs from a pediatric dental clinic in Toronto, Canada, maternal interviews will assess the child’s adverse and resilience-building experiences. Per child, one (exfoliated or extracted) tooth will be assessed for suspected enamel anomalies. If anomalies are present, the child is a case, and if absent, the child is a control. Tooth assessment modalities will include usual practice for dental exams (visual assessment) and modalities with greater sensitivity to identify anomalies. Conclusion: If structural changes in children’s teeth are associated with exposure to adversity, routine dental exams could provide an opportunity to screen children for experiences of adversity. Affected children could be referred for follow-up.

Reprogramming bone progenitor identity and potency through control of collagen density and oxygen tension

The biophysical microenvironment of the cell is being increasingly used to control cell signaling and to direct cell function. Herein, engineered 3D tuneable biomimetic scaffolds are used to control the cell microenvironment of Adipose-derived Mesenchymal Stromal Cells (AMSC), which exhibit a collagen density-specific profile for early and late stage bone cell lineage status. Cell potency was enhanced when AMSCs were cultured within low collagen density environments in hypoxic conditions. A transitional culture containing varied collagen densities in hypoxic conditions directed differential cell fate responses. The early skeletal progenitor identity (PDPN⁺CD146⁻CD73⁺CD164⁺) was rescued in the cells which migrated into low collagen density gels, with cells continuously exposed to the high collagen density gels displaying a transitioned bone-cartilage-stromal phenotype (PDPN⁺CD146⁺CD73⁻CD164^-). This study uncovers the significant contributions of the physical and physiological cell environment and highlights a chemically independent methodology for reprogramming and isolating skeletal progenitor cells from an adipose-derived cell population.

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Fabrication of a 3D transitional culture to control adipose-derived MSC (AMSC) fate

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AMSC potency is enhanced in low collagen density gels under hypoxic conditions

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Early skeletal progenitor identity of AMSCs is enriched in a low collagen density gel

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Bone-cartilage-stromal identity of AMSCs is enriched in a high collagen density gel

Nanomechanical and Molecular Characterization of Aging in Dentinal Collagen

Methylglyoxal (MGO) is an important molecule derived from glucose metabolism with the capacity of attaching to collagen and generating advanced glycation end products (AGEs), which accumulate in tissues over time and are associated with aging and diseases. However, the accumulation of MGO-derived AGEs in dentin and their effect on the nanomechanical properties of dentinal collagen remain unknown. Thus, the aim of the present study was to quantify MGO-based AGEs in the organic matrix of human dentin as a function of age and associate these changes with alterations in the nanomechanical and ultrastructural properties of dentinal collagen. For this, 12 healthy teeth from <26-y-old and >50-y-old patients were collected and prepared to obtain crown and root dentin discs. Following demineralization, MGO-derived AGEs were quantified with a competitive ELISA. In addition, atomic force microscopy nanoindentation was utilized to measure changes in elastic modulus in peritubular and intertubular collagen fibrils. Finally, principal component analysis was carried out to determine aging profiles for crown and root dentin. Results showed an increased presence of MGO AGEs in the organic matrix of dentin in the >50-y-old specimens as compared with the <26-y-old specimens in crown and root. Furthermore, an increase in peritubular and intertubular collagen elasticity was observed in the >50-y-old group associated with ultrastructural changes in the organic matrix as determined by atomic force microscopy analysis. Furthermore, principal component analysis loading plots suggested different "aging profiles" in crown and root dentin, which could have important therapeutic implications in restorative and adhesive dentistry approaches. Overall, these results demonstrate that the organic matrix of human dentin undergoes aging-related changes due to MGO-derived AGEs with important changes in the nanomechanical behavior of collagen that may affect diagnostic and restorative procedures in older people.

Dependency of hydration and growth conditions on the mechanical properties of oral biofilms

Within the oral cavity, dental biofilms experience dynamic environments, in part due to changes in dietary content, frequency of intake and health conditions. This can impact bacterial diversity and morpho-mechanical properties. While phenotypic properties of oral biofilms are closely related to their composition, these can readily change according to dynamic variations in the growth environment and nutrient availability. Understanding the interlink between phenotypic properties, variable growth conditions, and community characterization is an essential requirement to develop structure–property relationships in oral-biofilms. In this study, the impact of two distinct growth media types with increasing richness on the properties of oral biofilms was assessed through a new combination of in-vitro time-lapse biophysical methods with microbiological assays. Oral biofilms grown in the enriched media composition presented a decrease in their pH, an increase in soluble EPS production, and a severe reduction in bacterial diversity. Additionally, enriched media conditions presented an increase in biofilm volumetric changes (upon hydration) as well as a reduction in elastic modulus upon indentation. With hydration time considered a major factor contributing to changes in biofilm mechanical properties, we have shown that it is less associated than media richness. Future investigations can now use this time-lapse approach, with a clearer focus on the extracellular matrix of oral biofilms dictating their morpho-mechanical properties.

Measuring the elastic modulus of soft culture surfaces and three-dimensional hydrogels using atomic force microscopy

Growing interest in exploring mechanically mediated biological phenomena has resulted in cell culture substrates and 3D matrices with variable stiffnesses becoming standard tools in biology labs. However, correlating stiffness with biological outcomes and comparing results between research groups is hampered by variability in the methods used to determine Young's (elastic) modulus, E, and by the inaccessibility of relevant mechanical engineering protocols to most biology labs. Here, we describe a protocol for measuring E of soft 2D surfaces and 3D hydrogels using atomic force microscopy (AFM) force spectroscopy. We provide instructions for preparing hydrogels with and without encapsulated live cells, and provide a method for mounting samples within the AFM. We also provide details on how to calibrate the instrument, and give step-by-step instructions for collecting force-displacement curves in both manual and automatic modes (stiffness mapping). We then provide details on how to apply either the Hertz or the Oliver-Pharr model to calculate E, and give additional instructions to aid the user in plotting data distributions and carrying out statistical analyses. We also provide instructions for inferring differential matrix remodeling activity in hydrogels containing encapsulated single cells or organoids. Our protocol is suitable for probing a range of synthetic and naturally derived polymeric hydrogels such as polyethylene glycol, polyacrylamide, hyaluronic acid, collagen, or Matrigel. Although sample preparation timings will vary, a user with introductory training to AFM will be able to use this protocol to characterize the mechanical properties of two to six soft surfaces or 3D hydrogels in a single day.

Controlled Environment Neutron Radiography of Moisture Sorption/Desorption in Nanocellulose-Treated Cotton Painting Canvases

Nanocellulose-based materials have recently been used to consolidate degraded cotton painting canvases. Canvas-supported paintings consist of materials that are sensitive to moisture and especially susceptible to environmental fluctuations in temperature and relative humidity (RH). These environmental fluctuations occur in uncontrolled environments found in historic houses and palaces and can lead to hydrolytic degradation and mechanical damage to canvases. To simulate this situation in an experimental setting, canvas samples were mounted in a custom-made closed-cell and subjected to programmed cycles of RH at a controlled temperature while exposed to the neutron beam. Results are presented for both untreated samples and those treated with a polar consolidant, cellulose nanofibrils (CNF(aq)) in water, and an apolar consolidant, a composite of persilylated methyl cellulose with surface silylated cellulose nanocrystals (MC+CNC(h)) in heptane. They were then compared with changes in ionic conductivities as measured by dielectric analysis (DEA) with the same cyclic RH program and temperature. Although the samples were exposed to the same experimental conditions, they presented treatment-specific responses. CNF-treated canvas showed higher hygroscopicity than the untreated sample and facilitated moisture diffusion across the sample to areas not exposed to the environment. A sample treated with MC+CNC(h) retarded moisture diffusion during the increase in RH and could, therefore, afford protection to moisture absorption in uncontrolled environments. Thus, the experimental setup and resulting data provide a pilot study demonstrating the potential of neutron radiography in following and comparing real-time moisture diffusion dynamics in untreated and nanocellulose-consolidated cotton canvases and assisting in validating the overall benefit of the treatment.

ILC1 drive intestinal epithelial and matrix remodelling

Organoids can shed light on the dynamic interplay between complex tissues and rare cell types within a controlled microenvironment. Here, we develop gut organoid cocultures with type-1 innate lymphoid cells (ILC1) to dissect the impact of their accumulation in inflamed intestines. We demonstrate that murine and human ILC1 secrete transforming growth factor β1, driving expansion of CD44v6+ epithelial crypts. ILC1 additionally express MMP9 and drive gene signatures indicative of extracellular matrix remodelling. We therefore encapsulated human epithelial-mesenchymal intestinal organoids in MMP-sensitive, synthetic hydrogels designed to form efficient networks at low polymer concentrations. Harnessing this defined system, we demonstrate that ILC1 drive matrix softening and stiffening, which we suggest occurs through balanced matrix degradation and deposition. Our platform enabled us to elucidate previously undescribed interactions between ILC1 and their microenvironment, which suggest that they may exacerbate fibrosis and tumour growth when enriched in inflamed patient tissues.

Microporous Biodegradable Films Promote Therapeutic Angiogenesis

Peripheral arterial disease and critical limb ischemia are common symptoms of cardiovascular disease. Vascular surgery is used to create a bypass around occluded blood vessels to improve blood flow to ischemic muscle, thus avoiding the need for amputation. Attempts to vascularize tissues by therapeutic angiogenesis using delivery of exogenous angiogenic agents are underwhelming. A material-based approach that provides an endogenous stimulus capable of promoting angiogenesis and increased tissue perfusion would provide a paradigm shift in treatment options available. It is reported here that microporous biodegradable films produced using thermally induced phase separation provide a localized biophysical stimulus of proangiogenic genes in vivo that is associated with increased blood vessel density and restoration of blood flow to ischemic tissue. These findings show, for the first time, that acellular, nonfunctionalized biodegradable biomaterials can provide an innovative, material-based approach for therapeutic angiogenesis to enhance tissue reperfusion in vivo.

Modulatory Effect of Glycated Collagen on Oral Streptococcal Nanoadhesion

Biofilm-mediated oral diseases such as dental caries and periodontal disease remain highly prevalent in populations worldwide. Biofilm formation initiates with the attachment of primary colonizers onto surfaces, and in the context of caries, the adhesion of oral streptococci to dentinal collagen is crucial for biofilm progression. It is known that dentinal collagen suffers from glucose-associated crosslinking as a function of aging or disease; however, the effect of collagen crosslinking on the early adhesion and subsequent biofilm formation of relevant oral streptococci remains unknown. Therefore, the aim of this work was to determine the impact of collagen glycation on the initial adhesion of primary colonizers such as Streptococcus mutans UA159 and Streptococcus sanguinis SK 36, as well as its effect on the early stages of streptococcal biofilm formation in vitro. Type I collagen matrices were crosslinked with either glucose or methylglyoxal. Atomic force microscopy nanocharacterization revealed morphologic and mechanical changes within the collagen matrix as a function of crosslinking, such as a significantly increased elastic modulus in crosslinked fibrils. Increased nanoadhesion forces were observed for S. mutans on crosslinked collagen surfaces as compared with the control, and retraction curves obtained for both streptococcal strains demonstrated nanoscale unbinding behavior consistent with bacterial adhesin-substrate coupling. Overall, glucose-crosslinked substrates specifically promoted the initial adhesion, biofilm formation, and insoluble extracellular polysaccharide production of S. mutans, while methylglyoxal treatment reduced biofilm formation for both strains. Changes in the adhesion behavior and biofilm formation of oral streptococci as a function of collagen glycation could help explain the biofilm dysbiosis seen in older people and patients with diabetes. Further studies are necessary to determine the influence of collagen crosslinking on the balance between acidogenic and nonacidogenic streptococci to aid in the development of novel preventive and therapeutic treatment against dental caries in these patients.

A Synergistic Relationship between Polycaprolactone and Natural Polymers Enhances the Physical Properties and Biological Activity of Scaffolds

Biomaterials for tissue engineering include natural and synthetic polymers, but their clinical application is still limited due to various disadvantages associated with the use of these polymers. This uncertainty of the polymeric approach in tissue engineering launches an opportunity to address a key question: can we eliminate the disadvantages of both natural and synthetic polymers by combining them to form a synergistic relationship? To answer this question, we fabricated scaffolds from elastin, collagen, fibrin, and electrospun polycaprolactone (PCL) with different ratios. The material characterization of these scaffolds investigated degradation, water contact angle, angiogenesis by an ex ovo chorion allantoic membrane (CAM) assay, and mechanical and structural properties. Biological activity and specific differentiation pathways (MSC, adipogenic, osteogenic, myogenic, and chondrogenic) were studied by using human adipose-derived stem cells. Results indicated that all composite polymers degraded at a different rate, thus affecting their mechanical integrity. Cell-based assays demonstrated continual proliferative and viable properties of the cells on all seeded scaffolds with the particular initiation of a differentiation pathway among which the PCL/collagen/fibrin composite was the most angiogenic material with maximum vasculature. We were able to tailor the physical and biological properties of PCL-based composites to form a synergistic relationship for various tissue regeneration applications.

In Vivo Relationship between the Nano-Biomechanical Properties of Streptococcal Polysaccharide Capsules and Virulence Phenotype

In common with many bacterial pathogens, Streptococcus pneumoniae has a polysaccharide capsule which facilitates immune evasion and determines virulence. Recent data have shown that the closely related Streptococcus mitis also expresses polysaccharide capsules including those with an identical chemical structure to S. pneumoniae capsular serotypes. We utilized atomic force microscopy (AFM) techniques to investigate the biophysical properties of S. mitis and S. pneumoniae strains expressing the same capsular serotypes that might relate to differences in virulence potential. When comparing S. mitis and S. pneumoniae strains with identical capsule serotypes, S. mitis strains were susceptible to neutrophil killing, and electron microscopy and AFM demonstrated significant morphological differences. Force-volume mapping using AFM showed distinct force-curve profiles for the center and edge areas of encapsulated streptococcal strains. This "edge effect" was not observed in unencapsulated bacteria and therefore was a direct representation of the mechanical properties of the bacterial capsule. When two strains of S. mitis and S. pneumoniae expressed an identical capsular serotype, they presented similar biomechanical characteristics. This infers a potential relationship between capsule biochemistry and nanomechanics, independent of bacterial strain. Overall, this study demonstrates that it is possible to investigate reproducibly the mechanistic, structural, and mechanical properties of both the capsule and the body of individual living bacterial cells and relate the data to virulence phenotypes. We have demonstrated that using nanomechanics to investigate individual bacterial cells we can now begin to identify the surface properties bacterial pathogens require to avoid host-mediated immunity.

A phase II of gemcitabine combined with pazopanib followed by pazopanib maintenance, as second-line treatment in patients with advanced leiomyosarcomas: A unicancer French Sarcoma Group study (LMS03 study)

BACKGROUND

Options in second-line therapy after doxorubicin-based chemotherapy for metastatic/advanced leiomyosarcoma include gemcitabine (G), trabectedin and pazopanib (P) monotherapy. Currently, no combination therapy is better than monotherapy. LMS03 is an open-label multicentre single-group phase II study designed to assess the efficacy and tolerance of G + P in the second-line setting.

PATIENTS AND METHODS

Patients (pts), ECOG ≤2, with metastatic leiomyosarcomas (LMS) after first-line doxorubicin chemotherapy failure were eligible. Pts were treated with G 1000 mg/m² on days 1 and 8 of each 21 days (maximum eight cycles), in combination with oral daily P (800 mg), until disease progression/toxicity. 9-month progression-free survival (PFS) rate was the primary endpoint. Inacceptable and promising 9-month PFS rates were defined, in the intent-to-treat population, as 32% and 44%.

RESULTS

106 pts were included with a mean age of 59.8 years and an ECOG 0 in 63.5%; the primary tumour site was uterus in 61%. Pts were treated with P + G for a median of 3.8 mo, and P for a median of 4.2 mo. The 9-month PFS rate was 32.1% (95% CI 23.1-41.1). After a median follow-up of 14.2 months, the PFS was 6.5 months (95% CI 5.6-8.2), and the overall survival was 22.4 months (95% CI 16.9-26.5). The best response was 23.8%. The most frequent reported grade 3-4 adverse events were haematological.

CONCLUSIONS

LMS03 failed to show that second-line therapy, with gemcitabine combined with pazopanib, followed by pazopanib alone, was beneficial for advanced LMS patients. Eudract N°2011-001308-36 and NCT01442662.

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

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.

Phenotypic Properties of Collagen in Dentinogenesis Imperfecta Associated with Osteogenesis Imperfecta

Introduction

Dentinogenesis imperfecta type 1 (OIDI) is considered a relatively rare genetic disorder (1:5000 to 1:45,000) associated with osteogenesis imperfecta. OIDI impacts the formation of collagen fibrils in dentin, leading to morphological and structural changes that affect the strength and appearance of teeth. However, there is still a lack of understanding regarding the nanoscale characterization of the disease, in terms of collagen ultrastructure and mechanical properties. Therefore, this research presents a qualitative and quantitative report into the phenotype and characterization of OIDI in dentin, by using a combination of imaging, nanomechanical approaches.

Methods

For this study, 8 primary molars from OIDI patients and 8 primary control molars were collected, embedded in acrylic resin and cut into longitudinal sections. Sections were then demineralized in 37% phosphoric acid using a protocol developed in-house. Initial experiments demonstrated the effectiveness of the demineralization protocol, as the ATR-FTIR spectral fingerprints showed an increase in the amide bands together with a decrease in phosphate content. Structural and mechanical analyses were performed directly on both the mineralized and demineralized samples using a combination of scanning electron microscopy, atomic force microscopy, and Wallace indentation.

Results

Mesoscale imaging showed alterations in dentinal tubule morphology in OIDI patients, with a reduced number of tubules and a decreased tubule diameter compared to healthy controls. Nanoscale collagen ultrastructure presented a similar D-banding periodicity between OIDI and controls. Reduced collagen fibrils diameter was also recorded for the OIDI group. The hardness of the (mineralized) control dentin was found to be significantly higher (p<0.05) than that of the OIDI (mineralized) dentine. Both the exposed peri- and intratubular dentinal collagen presented bimodal elastic behaviors (Young’s moduli). The control samples presented a stiffening of the intratubular collagen when compared to the peritubular collagen. In case of the OIDI, this stiffening in the collagen between peri- and intratubular dentinal collagen was not observed and the exposed collagen presented overall a lower elasticity than the control samples.

Conclusion

This study presents a systematic approach to the characterization of collagen structure and properties in OIDI as diagnosed in dentin. Structural markers for OIDI at the mesoscale and nanoscale were found and correlated with an observed lack of increased elastic moduli of the collagen fibrils in the intratubular OIDI dentin. These findings offer an explanation of how structural changes in the dentin could be responsible for the failure of some adhesive restorative materials as observed in patients affected by OIDI.

Engineering of a Functional Tendon Using Collagen As a Natural Polymer

Reconstruction of a tendon rupture is surgically challenging as each end of the tendon retracts, leaving a substantial gap and direct repair is often not feasible. A tendon graft is required to bridge this defect and restore function. Presently, these gaps are filled with auto-, allo-, or synthetic grafts, but they all have clinical limitations. To address this issue, we developed tissue-engineered grafts by a rapid process using compressed type I collagen, which is the most dominant protein in the tendon. However, biomechanical properties were found to be unsuitable to withstand complete load-bearing in vivo. Hence, a modified suture technique was previously developed to reduce the load on the engineered collagen graft to aid integration in vivo. Using this technique, we tested engineered collagen grafts in vivo on a lapine model in three groups up to 12 weeks without immobilization. Gross observation at 3 and 12 weeks showed the bridge integrated without adhesions with a significant increase in the mechanical, structural and histological properties as compared to 1 week. Insertion of a tissue-engineered collagen graft using a novel load-bearing suture technique which partially loads in vivo showed integration, greater mechanical strength and no adhesion formation in the time period tested. This collagen graft has inherent advantages as compared to the present-day tendon grafts.

Glucosepane is associated with changes to structural and physical properties of collagen fibrils

Collagen glycation, and in particular the formation of advanced glycation end-product (AGE) crosslinks, plays a central role in the ageing process and in many of the long-term complications of diabetes. Glucosepane, the most abundant and relevant AGE crosslink, has been suggested to increase the stiffness of tissue and reduce its solubility, although no evidence is available concerning the mechanisms. We have used a combination of computational and experimental techniques to study a collagen-rich tissue with a relatively simple organisation to further our understanding of the impact of glucosepane on the structural and physical properties of collagen fibrils. Our work shows that glucosepane levels increase dramatically in aged tendon tissue and are associated with the reduced density of collagen packing and increased porosity to water molecules. Our studies provide the basis to understand many of the tissue dysfunctions associated with ageing and diabetes across a range of different tissues types.

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Levels of the advanced glycation end-product glucosepane increase in human tendon with increasing chronological age.

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Glucosepane results in a less tightly held helical structure in the collagen molecule and increased porosity to water.

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Water content is higher in Achilles and anterior tibialis tendon tissue from older individuals compared to young people.

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The denaturation temperature of collagen increases in the older age group suggesting a more highly cross-linked structure.

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The enthalpy of collagen denaturation decreases in older donors suggesting molecules are less confined within the fibril.

Abstract P1-09-07: Breast cancer characteristics and outcomes in patients with TP53 germline mutation

Introduction

Li-Fraumeni syndrome (LFS) resulting from monoallelic germline TP53 gene mutation is a rare hereditary cancer predisposition. Breast cancer (BC) is the most common cancer among women with TP53 germline mutation with a risk ranging from 49% to 85% by the age of 60 years old. Most of these cancers are early onset. Few patients' cases have been reported so far in the literature. Our aim was to describe the medical history of a cohort of LFS women diagnosed with BC recruited from a single institution. The characteristics combined were genetic alteration diagnosis, tumor characteristics, treatment, outcome, and LFS associated cancers.

Methods

We retrospectively identified breast cancer patients with TP53 germline mutation from the Institut Curie (Paris, France) database and described their cancer characteristics and medical history.

Results

From 1989 to 2015, 25 patients affected with BC (31 tumors) and TP53 germline mutation carrier were identified, with a median follow up of 6.5 years. Median age at BC diagnosis was 30.5 years. All patients were women. 33% had a previously identified TP53 mutation in their family. 70% of them had BC as their first cancer event. 60% of the patients presented with another LFS associated cancer or non-related cancers: osteosarcoma (22%), glioblastoma (18%), pulmonary carcinoma (13%), gastric linitis plastica (9%), malignant hemopathy (9%), soft tissue sarcoma (9%), adrenocortical carcinoma (4%), ovarian cystadenocarcinoma (4%), renal tumor (4%), choroid plexus carcinoma (4%).

92% of the breast tumors were ductal carcinoma (28% DCIS and 64% IDC), 7% were sarcoma (1 phyllodesarcoma, 1 pleiomorphic liposarcoma); there were no lobular carcinoma. Among the IDC, 50% were HER2 positive, 72% were hormone-receptor positive.

Most patients had a mastectomy (64%), and most of them received radiation (55%). However, when TP53 mutation had been identified prior to the treatment, none of the patients received radiotherapy (5 patients). Most patients received chemotherapy (70%) (37% in neoadjuvant setting, 33% in adjuvant setting, 25% for metastatic setting). 40% of the patients received hormone therapy (37% as adjuvant treatment, 7% for metastatic disease)

Most of the patients did not relapse from BC (75%). Overall, only 17% of the patients had metastatic BC. To date, 12 patients of our series have died (48%), 6 patients (24%) from other LFS-associated cancers and 4 patients from BC (16%).

Conclusion

To the best of our knowledge, this descriptive series is the largest study of tumor characteristics and medical history of LFS-women with BC, the most frequent cancer among women with TP53 germline mutation. It confirms the higher HER2 overexpression rate observed in LFS-patients BC, as suggested in the literature and showed a high rate of DCIS at initial presentation. Most of the patients developed other LFS-associated cancers. In depth molecular analysis of these BC will be performed in order to gain insight into their biological specificities and to adapt the therapeutic management of this poor prognosis syndrome.

Citation Format: Tran M, Loirat D, Colas C, Bozec L, Laurence V, Lerebours F, Cabel L, Bidard F-C, Stoppa-Lyonnet D, Vincent-Salomon A, Gauthier-Villars M, Lavigne M, De Pauw A. Breast cancer characteristics and outcomes in patients with TP53 germline mutation [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-09-07.

Impact of Carbamide Peroxide Whitening Agent on Dentinal Collagen

Carbamide peroxide (CP) is widely used as a tooth-whitening agent in self-administered tooth-bleaching products. In this study, the effects of 5% and 10% CP on dentinal collagen structure and chemical properties were evaluated in vitro. Thirty-five intact teeth were exposed to 2 whitening protocols (2 or 4 h daily) with either 5% or 10% CP gel for 1 wk. Shade changes before and after the whitening protocol were captured colorimetrically using a spectroshade. Collagen scaffold models and demineralized dentine disc samples were prepared and exposed to CP droplets (5% or 10%). Structural changes were investigated using electron microscopy. Finally, mineralized dentine disc samples were prepared postbleaching to assess chemical changes resulting from CP exposure in dentinal collagen using Raman spectroscopy. Results showed a difference in tooth shade when exposed to 5% and 10% CP whitening protocols, with a significantly ( P ≤ 0.01) greater change reported for the 10% CP/4-h group. Imaging of the collagen scaffold model following exposure to CP showed a gelatinization process indicating that the free radical by-products from CP are able to disrupt the quaternary structure of noncrosslinked collagen. The most significant damage on the collagen scaffold was seen for the 10% CP exposure for 4 h. Imaging of the demineralized discs displayed the same glassy amorphous layer appearance as found in the collagen scaffold. Raman spectra of the mineralized dentine discs showed a significant decrease ( P ≤ 0.01) in the integrated area of amide I and amide III values in the 4 test groups following CP application. Amide I was more affected as both the exposure time and concentration of CP increased. Despite the claimed safety of whitening agents, this in vitro study concludes that even low concentrations of CP result in a deleterious change in dentinal collagen.

An engineered, quantifiable in vitro model for analysing the effect of proteostasis-targeting drugs on tissue physical properties

Cellular function depends on the maintenance of protein homeostasis (proteostasis) by regulated protein degradation. Chronic dysregulation of proteostasis is associated with neurodegenerative and age-related diseases, and drugs targeting components of the protein degradation apparatus are increasingly used in cancer therapies. However, as chronic imbalances rather than loss of function mediate their pathogenesis, research models that allow for the study of the complex effects of drugs on tissue properties in proteostasis-associated diseases are almost completely lacking. Here, to determine the functional effects of impaired proteostatic fine-tuning, we applied a combination of materials science characterisation techniques to a cell-derived, in vitro model of bone-like tissue formation in which we pharmacologically perturbed protein degradation. We show that low-level inhibition of VCP/p97 and the proteasome, two major components of the degradation machinery, have remarkably different effects on the bone-like material that human bone-marrow derived mesenchymal stromal cells (hMSC) form in vitro. Specifically, whilst proteasome inhibition mildly enhances tissue formation, Raman spectroscopic, atomic force microscopy-based indentation, and electron microscopy imaging reveal that VCP/p97 inhibition induces the formation of bone-like tissue that is softer, contains less protein, appears to have more crystalline mineral, and may involve aberrant micro- and ultra-structural tissue organisation. These observations contrast with findings from conventional osteogenic assays that failed to identify any effect on mineralisation. Taken together, these data suggest that mild proteostatic impairment in hMSC alters the bone-like material they form in ways that could explain some pathologies associated with VCP/p97-related diseases. They also demonstrate the utility of quantitative materials science approaches for tackling long-standing questions in biology and medicine, and could form the basis for preclinical drug testing platforms to develop therapies for diseases stemming from perturbed proteostasis or for cancer therapies targeting protein degradation. Our findings may also have important implications for the field of tissue engineering, as the manufacture of cell-derived biomaterial scaffolds may need to consider proteostasis to effectively replicate native tissues.

Bi-directional cell-pericellular matrix interactions direct stem cell fate

Modifiable hydrogels have revealed tremendous insight into how physical characteristics of cells' 3D environment drive stem cell lineage specification. However, in native tissues, cells do not passively receive signals from their niche. Instead they actively probe and modify their pericellular space to suit their needs, yet the dynamics of cells' reciprocal interactions with their pericellular environment when encapsulated within hydrogels remains relatively unexplored. Here, we show that human bone marrow stromal cells (hMSC) encapsulated within hyaluronic acid-based hydrogels modify their surroundings by synthesizing, secreting and arranging proteins pericellularly or by degrading the hydrogel. hMSC's interactions with this local environment have a role in regulating hMSC fate, with a secreted proteinaceous pericellular matrix associated with adipogenesis, and degradation with osteogenesis. Our observations suggest that hMSC participate in a bi-directional interplay between the properties of their 3D milieu and their own secreted pericellular matrix, and that this combination of interactions drives fate.

Evaluation of the Adhesion and Performance of Natural Consolidants for Cotton Canvas Conservation

Recent developments in paper and canvas conservation have seen the introduction of nanocellulose (NC) as a compatible treatment for the consolidation of historical cellulosic artifacts and manuscripts. However, as part of the assessment of these new materials for canvas consolidation, the adhesion of the consolidation treatment (which takes place between the applied material and the substrate) has not yet been evaluated, and as a result, it is poorly understood by both the scientific and conservation communities. After evaluating the potential of NC treatments for the consolidation of cotton painting canvas, we investigate a route to promote the interaction between the existing canvas and the nanocellulose treatment, which is in our case made of cellulose nanofibrils (CNF). This was carried out by introducing a cationic polymer, polyamidoamine-epichlorohydrin (PAAE), as an intermediate layer between the canvas and the CNF. The morphological, chemical, and mechanical evaluation of the canvas samples at different relative humidity (RH) levels demonstrated how the adhesion of the added PAAE layer is a dominant factor in the consolidation process. Improvement in the coating of canvas single fibers by the CNF, higher adhesion energy between the canvas fibers and the CNF treatment, and finally overall stronger canvas reinforcement were observed following the introduction of PAAE. However, an increase in mechanical response to moisture sorption and desorption was also observed for the PAAE-treated canvases. Overall, this study shows the complexity of such systems and, as such, the relevance of using a multiscale approach for their assessment.

Proof-of-concept study to establish an in situ method to determine the nature and depth of collagen changes in dentine using Fourier Transform Infra-Red spectroscopy after sodium hypochlorite irrigation

AIM

To establish a method using Fourier Transform Infra-Red spectroscopy (FTIR) to characterize the nature and depth of changes in dentinal collagen following exposure to sodium hypochlorite (NaOCl) during root canal irrigation in an ex vivo model.

METHODOLOGY

Fourier Transform Infra-Red spectroscopy was used to assess the changes in dentinal collagen when the root canal was exposed to NaOCl. The changes in dentinal collagen caused by NaOCl irrigation of root canals in transverse sections of roots, at 0.5 mm from the canal wall and 0.5 mm from the external root surface, were assessed by FTIR. The data were analysed using paired t-test with 5% significance level.

RESULTS

Fourier Transform Infra-Red spectroscopy confirmed that NaOCl exposure caused alterations in the chemistry and structure of collagen in dentine. FTIR spectra obtained from dentine surfaces and dentine adjacent to root canals exposed to NaOCl, all consistently showed degradation and conformational change of the collagen structure. FTIR data from the ex vivo model showed that the depth of effect of NaOCl extended to at least 0.5 mm from the canal wall.

CONCLUSION

In extracted human teeth, NaOCl caused changes in dentinal collagen that were measurable by FTIR. In an ex vivo model, the depth of effect into dentine extended at least 0.5 mm from the canal wall.

Degradation pattern of a porcine collagen membrane in an in vivo model of guided bone regeneration

BACKGROUND AND OBJECTIVE

Although collagen membranes have been clinically applied for guided tissue/bone regeneration for more than 30 years, their in vivo degradation pattern has never been fully clarified. A better understanding of the different stages of in vivo degradation of collagen membranes is extremely important, considering that the biology of bone regeneration requires the presence of a stable and cell/tissue-occlusive barrier during the healing stages in order to ensure a predictable result. Therefore, the aim of this study was to investigate the degradation pattern of a porcine non-cross-linked collagen membrane in an in vivo model of guided bone regeneration (GBR).

MATERIAL AND METHODS

Decalcified and paraffin-embedded specimens from calvarial defects of 18, 10-month-old Wistar rats were used. The defects were treated with a double layer of collagen membrane and a deproteinized bovine bone mineral particulate graft. At 7, 14 and 30 days of healing, qualitative evaluation with scanning electron microscopy and atomic force microscopy, and histomorphometric measurements were performed. Markers of collagenase activity and bone formation were investigated using an immunofluorescence technique.

RESULTS

A significant reduction of membrane thickness was observed from 7 to 30 days of healing, which was associated with progressive loss of collagen alignment, increased collagen remodeling and progressive invasion of woven bone inside the membranes. A limited inflammatory infiltrate was observed at all time points of healing.

CONCLUSION

The collagen membrane investigated was biocompatible and able to promote bone regeneration. However, pronounced signs of degradation were observed starting from day 30. Since successful regeneration is obtained only when cell occlusion and space maintenance exist for the healing time needed by the bone progenitor cells to repopulate the defect, the suitability of collagen membranes in cases where long-lasting barriers are needed needs to be further reviewed.

Early Adhesion of Candida albicans onto Dental Acrylic Surfaces

Denture-associated stomatitis is a common candidal infection that may give rise to painful oral symptoms, as well as be a reservoir for infection at other sites of the body. As poly (methyl methacrylate) (PMMA) remains the main material employed in the fabrication of dentures, the aim of this research was to evaluate the adhesion of Candida albicans cells onto PMMA surfaces by employing an atomic force microscopy (AFM) single-cell force spectroscopy (SCFS) technique. For experiments, tipless AFM cantilevers were functionalized with PMMA microspheres and probed against C. albicans cells immobilized onto biopolymer-coated substrates. Both a laboratory strain and a clinical isolate of C. albicans were used for SCFS experiments. Scanning electron microscopy (SEM) and AFM imaging of C. albicans confirmed the polymorphic behavior of both strains, which was dependent on growth culture conditions. AFM force-spectroscopy results showed that the adhesion of C. albicans to PMMA is morphology dependent, as hyphal tubes had increased adhesion compared with yeast cells ( P < 0.05). C. albicans budding mother cells were found to be nonadherent, which contrasts with the increased adhesion observed in the tube region. Comparison between strains demonstrated increased adhesion forces for a clinical isolate compared with the lab strain. The clinical isolate also had increased survival in blood and reduced sensitivity to complement opsonization, providing additional evidence of strain-dependent differences in Candida-host interactions that may affect virulence. In conclusion, PMMA-modified AFM probes have shown to be a reliable technique to characterize the adhesion of C. albicans to acrylic surfaces.

Combining nano-physical and computational investigations to understand the nature of "aging" in dermal collagen

The extracellular matrix of the dermis is a complex, dynamic system with the various dermal components undergoing individual physiologic changes as we age. Age-related changes in the physical properties of collagen were investigated in particular by measuring the effect of aging, most likely due to the accumulation of advanced glycation end product (AGE) cross-links, on the nanomechanical properties of the collagen fibril using atomic force microscope nano-indentation. An age-related decrease in the Young’s modulus of the transverse fibril was observed (from 8.11 to 4.19 GPa in young to old volunteers, respectively, P<0.001). It is proposed that this is due to a change in the fibril density caused by age-related differences in water retention within the fibrils. The new collagen–water interaction mechanism was verified by electronic structure calculations, showing it to be energetically feasible.

Quantitative nanohistological investigation of scleroderma: an atomic force microscopy-based approach to disease characterization

Scleroderma (or systemic sclerosis, SSc) is a disease caused by excess crosslinking of collagen. The skin stiffens and becomes painful, while internally, organ function can be compromised by the less elastic collagen. Diagnosis of SSc is often only possible in advanced cases by which treatment time is limited. A more detailed analysis of SSc may provide better future treatment options and information of disease progression. Recently, the histological stain picrosirius red showing collagen register has been combined with atomic force microscopy (AFM) to study SSc. Skin from healthy individuals and SSc patients was biopsied, stained and studied using AFM. By investigating the crosslinking of collagen at a smaller hierarchical stage, the effects of SSc were more pronounced. Changes in morphology and Young’s elastic modulus were observed and quantified; giving rise to a novel technique, we have termed “quantitative nanohistology”. An increase in nanoscale stiffness in the collagen for SSc compared with healthy individuals was seen by a significant increase in the Young’s modulus profile for the collagen. These markers of stiffer collagen in SSc are similar to the symptoms experienced by patients, giving additional hope that in the future, nanohistology using AFM can be readily applied as a clinical tool, providing detailed information of the state of collagen.

Demineralization-remineralization dynamics in teeth and bone

Biomineralization is a dynamic, complex, lifelong process by which living organisms control precipitations of inorganic nanocrystals within organic matrices to form unique hybrid biological tissues, for example, enamel, dentin, cementum, and bone. Understanding the process of mineral deposition is important for the development of treatments for mineralization-related diseases and also for the innovation and development of scaffolds. This review provides a thorough overview of the up-to-date information on the theories describing the possible mechanisms and the factors implicated as agonists and antagonists of mineralization. Then, the role of calcium and phosphate ions in the maintenance of teeth and bone health is described. Throughout the life, teeth and bone are at risk of demineralization, with particular emphasis on teeth, due to their anatomical arrangement and location. Teeth are exposed to food, drink, and the microbiota of the mouth; therefore, they have developed a high resistance to localized demineralization that is unmatched by bone. The mechanisms by which demineralization-remineralization process occurs in both teeth and bone and the new therapies/technologies that reverse demineralization or boost remineralization are also scrupulously discussed. Technologies discussed include composites with nano- and micron-sized inorganic minerals that can mimic mechanical properties of the tooth and bone in addition to promoting more natural repair of surrounding tissues. Turning these new technologies to products and practices would improve health care worldwide.

Stage-two surgery using collagen soft tissue grafts: clinical cases and ultrastructural analysis

OBJECTIVE

To present the application of two different soft tissue grafts around dental implants during stage-two surgery. Furthermore, the ultrastructure of these materials is shown and discussed using scanning electron microscopy (SEM).

SUMMARY

Although soft tissue autografts may be currently regarded as the gold standard, harvesting of these grafts might lead to higher morbidity, longer chair time, and intra-/postoperative complications at the donor site. New developments in collagen scaff olds have provided an alternative to successfully replace autologous grafts in clinical practice. The SEM pictures clearly show the different composition of a bilayer scaff old (collagen matrix, CM) and a porcine acellular dermal matrix (ADM). These distinctive properties lead to different possible indications. Within the presented cases, ADM was used to augment the ridge contour and was placed into a buccal pouch to achieve complete coverage and an uneventful closed healing. On the other side, CM was left exposed to the oral cavity to successfully gain keratinized mucosa around and between two dental implants.

Regulation of post-Golgi LH3 trafficking is essential for collagen homeostasis

Post-translational modifications are necessary for collagen precursor molecules (procollagens) to acquire final shape and function. However, the mechanism and contribution of collagen modifications that occur outside the endoplasmic reticulum and Golgi are not understood. We discovered that VIPAR, with its partner proteins, regulate sorting of lysyl hydroxylase 3 (LH3, also known as PLOD3) into newly identified post-Golgi collagen IV carriers and that VIPAR-dependent sorting is essential for modification of lysines in multiple collagen types. Identification of structural and functional collagen abnormalities in cells and tissues from patients and murine models of the autosomal recessive multisystem disorder Arthrogryposis, Renal dysfunction and Cholestasis syndrome caused by VIPAR and VPS33B deficiencies confirmed our findings. Thus, regulation of post-Golgi LH3 trafficking is essential for collagen homeostasis and for the development and function of multiple organs and tissues.

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

As titanium (Ti) continues to be utilized in great extent for the fabrication of artificial implants, it is important to understand the crucial bacterium–Ti interaction occurring during the initial phases of biofilm formation. By employing a single-cell force spectroscopy technique, the nanoadhesive interactions between the early-colonizing Streptococcus sanguinis and a clinically analogous smooth Ti substrate were explored. Mean adhesion forces between S. sanguinis and Ti were found to be 0.32±0.00, 1.07±0.06, and 4.85±0.56 nN for 0, 1, and 60 seconds contact times, respectively; while adhesion work values were reported at 19.28±2.38, 104.60±7.02, and 1,317.26±197.69 aJ for 0, 1, and 60 seconds, respectively. At 60 seconds surface delays, minor-rupture events were modeled with the worm-like chain model yielding an average contour length of 668±12 nm. The mean force for S. sanguinis minor-detachment events was 1.84±0.64 nN, and Poisson analysis decoupled this value into a short-range force component of −1.60±0.34 nN and a long-range force component of −0.55±0.47 nN. Furthermore, a solution of 2 mg/mL chlorhexidine was found to increase adhesion between the bacterial probe and substrate. Overall, single-cell force spectroscopy of living S. sanguinis cells proved to be a reliable way to characterize early-bacterial adhesion onto machined Ti implant surfaces at the nanoscale.

Optical coherence tomography use in the diagnosis of enamel defects

Molar incisor hypomineralization (MIH) affects the permanent incisors and molars, whose undermineralized matrix is evidenced by lesions ranging from white to yellow/brown opacities to crumbling enamel lesions incapable of withstanding normal occlusal forces and function. Diagnosing the condition involves clinical and radiographic examination of these teeth, with known limitations in determining the depth extent of the enamel defects in particular. Optical coherence tomography (OCT) is an emerging hard and soft tissue imaging technique, which was investigated as a new potential diagnostic method in dentistry. A comparison between the diagnostic potential of the conventional methods and OCT was conducted. Compared to conventional imaging methods, OCT gave more information on the structure of the enamel defects as well as the depth extent of the defects into the enamel structure. Different types of enamel defects were compared, each type presenting a unique identifiable pattern when imaged using OCT. Additionally, advanced methods of OCT image analysis including backscattered light intensity profile analysis and enface reconstruction were performed. Both methods confirmed the potential of OCT in enamel defects diagnosis. In conclusion, OCT imaging enabled the identification of the type of enamel defect and the determination of the extent of the enamel defects in MIH with the advantage of being a radiation free diagnostic technique.

Influence of biomaterial nanotopography on the adhesive and elastic properties of Staphylococcus aureus cells

Despite the well-known beneficial effects of biomaterial nanopatterning on host tissue integration, the influence of controlled nanoscale topography on bacterial colonisation and infection remains unknown.

Nanotechnology in dentistry: prevention, diagnosis, and therapy

Nanotechnology has rapidly expanded into all areas of science; it offers significant alternative ways to solve scientific and medical questions and problems. In dentistry, nanotechnology has been exploited in the development of restorative materials with some significant success. This review discusses nanointerfaces that could compromise the longevity of dental restorations, and how nanotechnolgy has been employed to modify them for providing long-term successful restorations. It also focuses on some challenging areas in dentistry, eg, oral biofilm and cancers, and how nanotechnology overcomes these challenges. The recent advances in nanodentistry and innovations in oral health-related diagnostic, preventive, and therapeutic methods required to maintain and obtain perfect oral health, have been discussed. The recent advances in nanotechnology could hold promise in bringing a paradigm shift in dental field. Although there are numerous complex therapies being developed to treat many diseases, their clinical use requires careful consideration of the expense of synthesis and implementation.