Biology subjects

Bozec, L.

Publications and source records attributed to Bozec, L..

7 recordsLinked to original sources

bioRxiv2026

Multimodal non-ionizing quantitative characterization of enamel hypomineralization

Enamel hypomineralization is clinically graded but difficult to quantify with visual and radiographic assessment. We evaluated whether optical coherence tomography (OCT) and lock-in thermography imaging (LITI) provide non-ionizing, quantitative lesion localization and phenotyping, using clinical mDDE classification as a practical benchmark and micro-CT ({micro}CT) mineral density as an in vitro reference in a subset. Twenty-five extracted first permanent molars were classified as control, hypomineralized (Type 1 white-cream; Type 2 yellow-brown), or other enamel defects. Co-localized OCT A-scan decay slopes and LITI lock-in phase-contrast were measured in predefined ROIs; six teeth underwent {micro}CT with hydroxyapatite calibration. Clinical scoring showed substantial agreement (inter-rater {kappa}=0.61; intra-rater {kappa}=0.70). OCT decay slopes differed across clinical groups (Kruskal-Wallis p=0.00028), separating controls from defect groups, while separation between hypomineralization and other defects was limited. LITI detected thermophotonic "hot spots" at many clinically identified sites (sensitivity 80%) but showed low specificity (20%) at a single modulation frequency, consistent with high anomaly sensitivity but limited etiologic discrimination. In the {micro}CT subset, hypomineralized ROIs showed reduced mineral density relative to adjacent enamel and spatial concordance with OCT and LITI contrast. Together, OCT+LITI support objective lesion mapping and motivate multi-frequency thermophotonics and expanded reference sampling to improve specificity for chairside translation.

biophysics↗

bioRxiv2026

Conditioning dentinal collagen by glycation improves long-term bond strength

ObjectivesThis study examined methylglyoxal (MGO) as a collagen crosslinker to reinforce demineralized dentin, enhance its enzymatic resistance, and improve long-term durability of the resin-dentin bond. MethodsDemineralized dentinal collagen films were treated with 0.5, 1, or 3 M MGO and subsequently exposed to collagenase to assess their resistance to enzymatic degradation. MGO-induced crosslink formation was monitored using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) spectroscopy by tracking the carbohydrate-associated band at 1180 cm-{superscript 1}. The apparent elastic modulus of the treated specimens was measured using a three-point bending test. For bond strength evaluation, resin-dentin beams were prepared and tested using microtensile bond strength (TBS) to assess the influence of MGO pretreatment on interfacial adhesion. ResultsThe ATR-FTIR spectra demonstrated increased intensity in the carbohydrate double bands (1000-1180 cm-{superscript 1}) in glycated samples compared to the control. Glycation with 3 M MGO exhibited the highest resistance to enzymatic degradation, persisting for up to 60 hours with a 78-fold increase in resistance factor compared to the control group (p < 0.05). Furthermore, glycation with 3 M MGO resulted in a 4-fold increase in elastic modulus compared with the control group. Notably, the functionalized dentin retained its improved mechanical properties even after collagenase exposure, whereas the control group experienced a significant 68.2% reduction in elastic modulus (p = 0.002). While MGO pretreatment did not influence resin infiltration or initial TBS ({approx}30-35 MPa), it maintained its original bond strength after one month of collagenase challenge. In contrast, the control group exhibited a significant reduction, decreasing to 17 {+/-} 5.5 MPa compared with its initial value (p < 0.01). ConclusionMGO demonstrated efficacy in enhancing the mechanical properties and enzymatic stability of collagen as well as improving the resistance of the bonded interface to enzymatic degradation. SignificanceMGO pretreatment maintains the long-term stability of the resin-dentin interface by protecting dentinal collagen from enzymatic degradation, without compromising initial bonding performance. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/701305v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@54ae32org.highwire.dtl.DTLVardef@1787fdforg.highwire.dtl.DTLVardef@130b40org.highwire.dtl.DTLVardef@47c5f9_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Quantitative Nanohistology of aging dermal collagen

While the external signs of skin aging have been well-defined throughout history, much less is known about aging within the ultrastructure of our skin. Our skin, the largest organ in our body, is structured by collagen through fibrils or large sheets. With the increased use of nanometrology tools in histology, it is now possible to explore how the aging process affects collagen at its most fundamental level, the collagen fibril. Here, we show how atomic force microscopy-based quantitative nanohistology can differentiate skin from different age groups and anatomical sites. Following the definition of specific collagen biomarkers at the nanoscale, we used a segmentation approach to quantify the prevalence of 4 structural biomarkers over a dataset of 42,000 images (30 donors) complemented by extensive nanomechanical analyses (30,000 indentation curves) on histological sections. Our results demonstrate that specific age-related collagen fingerprints could be found when comparing the % prevalence of each marker between the papillary and reticular dermis. A case of abnormal biological aging validated our markers and nanohistology approach. This first extensive study focusing on defining signs of dermal aging at the nanoscale proves we are all unique to our dermal collagen ultrastructure.

biophysics↗

bioRxiv2022

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 10mM MGO to induce AGE formation, which was characterized with microscopy and ELISA. Subsequently, AFM cantilevers were functionalized with living S. mutans UA 159 or S. 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 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 non-specific forces and interactions between S. mutans UA 159 and MGO-modified collagen substrates. In summary, these results suggest that collagen alterations due to glycation and AGE formation may play a role in early bacterial adherence to oral tissues, associated with conditions such as aging or chronic hyperglycemia, amongst others.

microbiology↗

bioRxiv2022

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 neighboring 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 accumulation of AGEs.

bioengineering↗

bioRxiv2020

ILC1-derived TGFβ1 drives intestinal remodelling

Organoids can shed light on the dynamic interplay between complex tissues and rare cell types within a controlled microenvironment. Here, we developed gut organoid co-cultures with type-1 innate lymphoid cells (ILC1) to dissect the impact of their accumulation in inflamed intestines. We demonstrate for the first time that murine and human ILC1 secrete TGF{beta}1, 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.

immunology↗

bioRxiv2019

Investigating the biochemical properties of Streptococcal polysaccharide capsules using atomic force microscopy

In common with many bacterial pathogens, Streptococcus pneumoniae has a polysaccharide capsule, which facilitates immune evasion and is a key virulence determinant. However, recent data has shown that the closely related Streptococcus mitis can also express polysaccharide capsules including those with an identical chemical structure to S. pneumoniae capsular serotypes. We have used 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 their differences in virulence potential. When comparing S. mitis and S. pneumoniae strains with identical capsule serotypes S. mitis strains were more susceptible to neutrophil killing and imaging using electron microscopy and AFM demonstrated significant morphological differences. Force-volume mapping using AFM showed distinct force-curve profiles for the centre and edge areas of encapsulated S. pneumoniae and S. mitis strains. This \"edge effect\" was not observed in the unencapsulated streptococcal strains and in an unencapsulated Staphylococcus aureus strain, 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 also similar biomechanical characteristics. This would infer a potential relationship between capsule biochemistry and nanomechanics, independent of the bacterial strains. Overall, AFM was an effective tool to explore the biophysical properties of bacterial capsules of living bacteria by reproducibly quantifying the elastic and adhesive properties of bacterial cell surfaces. Using AFM to investigate capsule differences over a wider range of strains and capsular serotypes of streptococci and correlate the data with phenotypic differences will elucidate how the biophysical properties of the capsule can influence its biological role during infection.

microbiology↗