Biology subjects

Xavier, M.

Publications and source records attributed to Xavier, M..

6 recordsLinked to original sources

bioRxiv2025

Single cell-derived spheroids for real-time growth and metabolomic studies in breast cancer

Breast cancer remains a leading cause of cancer-related mortality, with disease progression and metastasis posing significant challenges in treatment. Three-dimensional (3D) cancer models have emerged as valuable tools for studying cancer cell biology in a physiologically relevant microenvironment. Studying the tumour heterogeneity and metabolic adaptations at the single-cell level can be crucial to identify factors driving metastatic progression. Here, we present a novel approach to generate single cell-derived breast cancer spheroids using cell lines (MCF-7 and MCF-10A) within a decellularised adipose tissue extracellular matrix (adECM). Spheroid culture conditions were optimised with integrated plasmonic nanosensors (gold nanostars - GNSs), to enable real-time surface-enhanced Raman scattering (SERS)-based measurements. Our results demonstrated that spheroid growth kinetics and viability in adECM were comparable to commonly used animal-derived matrices, validating its use as a reproducible ECM hydrogel. We further show that the concentration of plasmonic nanosensors used was compatible with cell culture and enabled SERS detection of a model reporter, paving the way for label-free, non-destructive analysis of cancer cell metabolism. This platform offers a promising approach to study cancer progression, including metabolic adaptations, with potential applications in biomarker discovery and preclinical research.

cancer biology↗

bioRxiv2024

Engineered chitosan-derived nanocarrier for efficient siRNA delivery to peripheral and central neurons

Gene therapy using small interfering RNA (siRNA) holds promise for treating neurological disorders by silencing specific genes, such as the phosphatase and tensin homolog (PTEN) gene, which restricts axonal growth. Yet, delivering siRNA to neurons efficiently is challenging due to premature degradation and unspecific delivery. Chitosan-based delivery systems have shown great potential due to their well-established biocompatibility. However, their limited transfection efficiency and lack of neuronal tropism require further modification. Building on our previous successes with neuron-targeted DNA delivery using chitosan, a novel approach for siRNA delivery aimed at PTEN downregulation is proposed. This involves using thiolated trimethyl chitosan (TMCSH)-based siRNA nanoparticles functionalized with the neurotropic C-terminal fragment of the tetanus neurotoxin heavy chain (HC) for efficient delivery to both peripheral and central neurons. These polyplexes demonstrated suitable physicochemical properties, biocompatibility, and no adverse effects on neuronal electrophysiology. Diverse neuronal models, including 3D ex vivo cultures and microfluidics, confirmed polyplexes efficiency and neurospecificity. HC targeting significantly enhanced nanoparticle neuronal binding, and live cell imaging revealed five times faster retrograde transport along axons. Furthermore, siRNA delivery targeting PTEN promoted axonal outgrowth in embryonic cortical neurons. Thus, these polyplexes represent a promising platform for siRNA delivery, offering potential for clinical translation and therapeutic applications.

bioengineering↗

bioRxiv2024

Unveiling the potential of neuron-targeted dendriplexes for siRNA delivery using a PNS-CNS-on-Chip

Neurological disorders, a leading global cause of death, encompass conditions affecting the peripheral and central nervous systems (PNS and CNS, respectively). Limited axon regeneration is a significant challenge in these disorders, and it is linked to proteins like PTEN. RNA-based therapeutics, particularly siRNAs, hold potential for silencing these inhibitory pathways, but their clinical application is hindered by poor stability and cellular uptake. Our study addressed this challenge with the development of novel, fully biodegradable dendritic nanoparticles designed specifically for neuron targeting. These nanoparticles were functionalized with the neurotropic binding domain of tetanus toxin, enhancing selective neuronal targeting and cellular internalization. We demonstrated that these dendriplexes not only maintain biocompatibility and efficient siRNA delivery in neuronal cultures but also significantly enhance axonal growth, as shown in microfluidic models. In a groundbreaking PNS-CNS-on-Chip, dendriplexes exhibited effective migration from PNS to CNS neurons, highlighting their potential for targeted therapeutic delivery. This study pioneers the application of microfluidics to demonstrate the CNS targeting of dendriplexes, paving the way for innovative treatments in the field of nanomedicine.

bioengineering↗

bioRxiv2024

Consistency of resting-state correlations between fMRI networks and EEG band-power

Several simultaneous EEG-fMRI studies have aimed to identify the relationship between EEG band power and fMRI resting state networks (RSNs) to elucidate their neurobiological significance. Although common patterns have emerged, inconsistent results have also been reported. This study examines the consistency of these correlations across subjects and to understand how factors such as the hemodynamic response delay and the use of different EEG data spaces (source/scalp) influence them. Using three distinct EEG-fMRI datasets, acquired independently on 1.5T, 3T and 7T MRI scanners (comprising 42 subjects in total), we evaluate the generalizability of our findings across different acquisition conditions. We found consistent correlations between fMRI RSN and EEG band-power time-series across subjects in the three datasets studied, with systematic variations with RSN, EEG frequency-band, and HRF delay, but not with EEG space. Qualitatively, the majority of these correlations were similar across the three datasets, despite important differences in field strength, number of subjects and resting-state conditions. Our findings support consistent correlations across specific fMRI RSNs and EEG bands and highlight the importance of methodological considerations in interpreting them that may explain conflicting reports in existing literature.

neuroscience↗

bioRxiv2024

A miniaturised semi-dynamic in-vitro model of human digestion

Reliable in-vitro digestion models that are able to successfully replicate the conditions found in the human gastrointestinal tract (GIT) are key to assess the fate and efficiency of new formulations aimed for oral consumption. However, current in-vitro models either lack the capability to replicate crucial dynamics of digestion or require large volumes of sample/reagents, which can be scarce when working with nanomaterials under development. Here, we propose a miniaturised digestion system, a digestion-chip, based on incubation chambers integrated on a polymethylmethacrylate (PMMA) device. The digestion-chip incorporates key dynamic features of human digestion, such as gradual acidification and gradual addition of enzymes and simulated fluids in the gastric phase, and controlled gastric emptying, while maintaining low complexity and using small volumes of sample and reagents. In addition, the new approach integrates real-time automated closed-loop control of two key parameters, pH and temperature, during the two main phases of digestion (gastric and intestinal) with an accuracy down to {+/-}0.1{degrees}C and {+/-}0.2 pH points. The experimental results demonstrate that the digestion-chip successfully replicates the gold standard static digestion INFOGEST protocol and that the semi-dynamic digestion kinetics can be reliably fitted to a first kinetic order model. These devices can be easily adapted to dynamic features in an automated, sensorised, and inexpensive platform and will enable reliable, low-cost and efficient assessment of the bioaccessibility of new and expensive drugs, bioactive ingredients or nano-engineered materials aimed for oral consumption, thereby avoiding unnecessary animal testing.

bioengineering↗

bioRxiv2019

Optimising DNA-Coated Gold Nanoparticles to Enrich Skeletal Stem Cells from Human Bone Marrow Samples

Human bone marrow (BM) derived stromal cells contain a population of skeletal stem cells (SSCs), with the capacity to differentiate along the osteogenic, adipogenic and chondrogenic lineages enabling their application to clinical therapies. However, current methods, to isolate and enrich SSCs from human tissues remain, at best, challenging in the absence of a specific SSC marker. Unfortunately, none of the current proposed markers, alone, can isolate a homogenous cell population with the ability to form bone, cartilage, and adipose tissue in humans. Here, we have designed DNA-gold nanoparticles able to identify and sort SSCs displaying specific mRNA signatures. The current approach demonstrates the significant enrichment attained in the isolation of SSCs, with potential therein to enhance our understanding of bone cell biology and translational applications. TABLE OF CONTENTS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/882563v3_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@48c5acorg.highwire.dtl.DTLVardef@1a9d096org.highwire.dtl.DTLVardef@1bd4da2org.highwire.dtl.DTLVardef@133dd1d_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗