Biology subjects

Mota, C.

Publications and source records attributed to Mota, C..

18 recordsLinked to original sources

bioRxiv2026

Engineering a hybrid 3D construct for bone regeneration to promote simultaneous pre-vascularization and osteogenic differentiation in vitro

Critical-sized bone defects represent a challenge in bone tissue engineering, due to insufficient vascularization that results in implant failure. Scaffold pre-vascularization is a promising strategy to create a functional microvascular network that integrates with host vasculature. In this study, we present a hybrid 3D construct comprising a hyaluronic acid-based hydrogel and a 3D printed polycaprolactone/{beta}-tricalcium phosphate scaffold, to support vascular network formation and osteogenic differentiation. Peptide-functionalized (i.e. RGD, YIGSR, IKVAV, QK) hydrogels were obtained via thiol-ene chemistry, using two crosslinkers (PEG-diSH or MMP-diSH). Preliminary biological experiments assessed human mesenchymal stromal cells (hMSCs), endothelial cells (hUVECs), and their co-culture, on different gel formulations. All cell conditions displayed enhanced spreading and metabolic activity on gel formulations comprising RGD; thus these (i.e. RGD only and a combination of RGD/YIGSR) were selected for further studies. Cells were then mixed with the hydrogel precursor solutions, which were injected to embed the scaffolds and crosslinked using a UV lamp. After 7 days, tubule formation was observed only in co-culture conditions, highlighting the importance of cellular crosstalk for the formation of a vascular network. Significant differences were found across the tested formulations. In the RGD-PEG constructs, hUVECs formed tubule-like structures, surrounded by hMSCs, exhibiting pericyte-like behavior, supported by the upregulation of SMA gene. Conversely, in the RGD/YIGSR-MMP conditions, hMSCs were mostly located on the scaffold fibers, and showed the highest expression of early osteogenic markers (RUNX2 and ALP). Overall, we demonstrated that the hybrid system with tailored hydrogel chemistry can support simultaneous microvascular organization and osteogenic commitment, offering a promising platform for bone tissue engineering applications. However, further studies involving longer culture periods will aim at clarifying the complex interplay between material composition, cell crosstalk and spatial organization and their influence on the maturation and stability of the vascular network.

bioengineering↗

bioRxiv2026

Microfluidic bioprinting of a physiologically relevant thyroid three-dimensional in vitro model

Endocrine disruptors (EDs) are an exogenous group of compounds associated with thyroid malfunctioning in the human body. Nonetheless, there are currently no adequate in vivo or in vitro models for the preclinical testing of these compounds since both animal and two-dimensional (2D) cell-based models are not able to mimic thyroid physiological conditions from both functional and three-dimensional (3D) organization perspective. Recently, bioprinting technologies emerged as an innovative tool in the field of regenerative medicine and advanced 3D in vitro models that allow the creation of 3D well-organized structures able to mirror physiologically relevant tissue and organ architectures. In this study, we evaluated microfluidic bioprinting as a biofabrication technology to develop a 3D in vitro model of the thyroid gland. We studied the fundamental parameters to obtain a fine control over the bioprinted fibres for different biomaterials. Then, we assessed the possibility to bioprint single thyroid cells, thyroid spheroids and finally mouse embryonic stem cell-derived thyroid follicles. The different cell types maintained high viability and metabolic activity. The bioprinted thyroid model showed high expression of different early and late functional markers and to be responsive to ED exposure. These bioprinted thyroid constructs could provide a new set of advanced 3D in vitro models to test potential EDs and possible adverse outcomes that may be associated with their administration or exposure.

bioengineering↗

bioRxiv2026

Structure of human aldehyde oxidase under tris(2-carboxyethyl)phosphine-reducing conditions

The importance of human aldehyde oxidase (hAOX1) has increased over the last decades due to its involvement in drug metabolism. Inhibition studies concerning hAOX1 are extensive and a common reducing agent, dithiothreitol (DTT), was recently found to inactivate the enzyme. However, in previous crystallographic studies of hAOX1, DTT was found to be essential for crystallization. To surpass this concern another reducing agent used in crystallization trials. Using tris(2-carboxyethyl)phosphine (TCEP), a sulphur-free reducing agent, it was possible to obtain well-ordered crystals from hAOX1 wild type and variant, hAOX1_6A, which diffracted beyond 2.3 [A]. Instead of the typical star-shaped crystals of hAOX1, at pH 4.7, plates are obtained in the orthorhombic space group (P22121) with two molecules in the asymmetric unit. Activity assays with the enzyme incubated with both reducing agents show that contrary to DTT, TCEP does not lead to irreversible inactivation of the enzyme. The replacement of DTT with TCEP in crystallization of hAOX1 provides a strategy to circumvent enzyme inactivation during crystallographic studies, allowing future applications of new assays, such as time-resolved crystallography.

biochemistry↗

bioRxiv2025

Packed for Ossification: High-Density Bioprinting of hPDC Spheroids in HAMA for Endochondral Ossification

Long bone fractures are primarily repaired through endochondral ossification, a process in which a soft cartilage template forms at the injury site and is gradually replaced by bone. While bone has an innate self-healing capacity, this process can be disrupted in cases of large or complex defects, where regeneration fails, and clinical intervention is required. This study aimed at the development of a tissue engineering approach using human periosteum-derived cell (hPDC) spheroids encapsulated or bioprinted at high density within hyaluronic acid methacrylate (HAMA) hydrogels to support hypertrophic cartilage formation as a template for endochondral bone regeneration. We first compared different encapsulation time points (days 1, 7, and 14), finding that early encapsulation (day 1) enhanced spheroid fusion, increased DNA content, and promoted hypertrophic cartilage formation, as indicated by greater glycosaminoglycan (GAG) and collagen deposition along with lacunae formation. Next, HAMA-encapsulated spheroids were compared to spheroids formed using a standardized microwell platform, demonstrating that encapsulation promoted a more mature cartilage-like matrix with thicker collagen fibers and enhanced hypertrophic differentiation. Gene expression and immunostaining confirmed progression toward hypertrophic and osteogenic phenotypes. Finally, extrusion-based bioprinting of HAMA bioinks comprising a high-density of hPDC spheroids demonstrated scalability, improved spheroid alignment, and maintained robust cell viability and hypertrophic differentiation. HAs bioactivity and regulatory advantages support clinical translation, although achieving spatial control remains an area for further optimization. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/674866v2_ufig1.gif" ALT="Figure 1"> View larger version (67K): org.highwire.dtl.DTLVardef@40b55eorg.highwire.dtl.DTLVardef@434b2corg.highwire.dtl.DTLVardef@1fc4640org.highwire.dtl.DTLVardef@168252e_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Dimethyl sulfoxide primes induced pluripotent stem cells for more efficient nephron progenitor and kidney organoid differentiation

The field of human induced pluripotent stem cells (hiPSCs) has seen significant progress since the discovery of reprogramming somatic cells using the transcription factors Oct4, Sox2, Klf4, and c-Myc. hiPSCs are similar to embryonic stem cells in a primed state of pluripotency and has the potential to differentiate into any adult human cell type, offering a versatile tool for research and potential therapeutic applications. However, the efficiency of differentiation protocols for generating complex structures with multiple cell types, like kidney organoids, remains a challenge. This study investigates the impact of treating hiPSCs with a low-dose dimethyl sulfoxide to enhance kidney organoid differentiation using a well-established protocol from literature. We found that treating hiPSCs with 1-2% DMSO affects gene expression of pluripotent transcription factors, hiPSC colony morphology, and enhances the expression of key metanephric mesenchyme nephron progenitor marker, SIX2 after 9 days of kidney organoid differentiation. Our findings also suggest that DMSO treatment helps improve hiPSC differentiation protocol efficiency toward the development of tubular kidney organoids. Further research is needed to elucidate the mechanisms underlying these effects and to refine the differentiation process for potential in vitro research applications in biomedical research and drug development.

cell biology↗

bioRxiv2024

Evolutionary unique N-glycan-dependent protein quality control system plays pivotal roles in cellular fitness and extracellular vesicle transport in Cryptococcus neoformans

A conserved N-glycan-dependent endoplasmic reticulum protein quality control (ERQC) system has evolved in eukaryotes to ensure accuracy during glycoprotein folding. The human pathogen Cryptococcus neoformans possesses a unique N-glycosylation pathway that affects microbial physiology and interactions with the infected host. To investigate the molecular features and functions of the ERQC system in C. neoformans, we characterized a set of mutants with deletion of genes coding for the ERQC sensor UDP-glucose:glycoprotein glucosyltransferase (UGG1) and putative 1,2-mannose-trimming enzymes (MNS1, MNS101, MNL1, and MNL2). The ugg1{Delta}, mns1{Delta}, mns101{Delta}, and mns1{Delta}101{Delta} mutants showed alterations in N-glycan profiles, defective cell surface organization, decreased survival in host cells, and varying degrees of reduced in vivo virulence. The ugg1{Delta} strain exhibited severely impaired extracellular secretion of capsular polysaccharides and virulence-related enzymes. Comparative transcriptome analysis showed the upregulation of protein folding, proteolysis, and cell wall remodeling genes, indicative of induced ER stress. However, no apparent changes were observed in the expression of genes involved in protein secretion or capsule biosynthesis. Additionally, extracellular vesicle (EV) analysis combined with proteomic analysis showed significant alterations in the number, size distribution, and cargo composition of EVs in ugg1{Delta}. These findings highlight the essential role of the functional ERQC system for cellular fitness under adverse conditions and proper EV-mediated transport of virulence factors, which are crucial for the full fungal pathogenicity of C. neoformans.

microbiology↗

bioRxiv2024

Embedding bioprinting of low viscous, photopolymerizable blood-based bioinks in a self-healing transparent supporting bath

Protein-based hydrogels have great potential to be used as bioinks for biofabrication-driven tissue regeneration strategies due to their innate bioactivity. Nevertheless, their use as bioinks in conventional 3D bioprinting is impaired due to their intrinsic low viscosity. Using embedding bioprinting, a liquid bioink is printed whithin a support that physically holds the patterned filament. Inspired by the recognized microencapsulation technique complex coacervation, we introduce crystal self-healing embedding bioprinting (CLADDING) based on a highly transparent crystal supporting bath. The suitability of distinct classes of gelatins was evaluated (i.e., molecular weight distribution, isoelectric point and ionic content), as well as the formation of gelatin-gum arabic microparticles as a function of pH, temperature, solvent and mass ratios. Characterizing and controlling this parametric window resulted in high yields of support bath with ideal self-healing properties for interaction with protein-based bioinks during bioprinting. This support bath achieved transparency, which boosted light permeation within the bath. CLADDING bioprinted constructs fully composed of platelet lysates encapsulating a co-culture of human mesenchymal stem cells and endothelial cells were obtained, demonstrating high-dense cellular network with excellent cell viability and stability over a month. CLADDING broadens the spectrum of photocrosslinkable materials with extremely low viscosity that can now be bioprinted with sensitive cells using embedding bioprinting without any additional support.

bioengineering↗

bioRxiv2024

Metal ion activation and DNA recognition by the Deinococcus radiodurans manganese sensor DR2539

The accumulation of manganese ions is crucial for scavenging reactive oxygen species (ROS) and protecting the proteome of Deinococcus radiodurans (Dr). However, metal homeostasis still needs to be tightly regulated to avoid toxicity. DR2539, a dimeric transcription regulator, plays a key role in Dr manganese homeostasis. Despite comprising three well-conserved domains: a DNA binding domain, a dimerization domain, and an ancillary domain, both the metal ion activation mechanism and the DNA recognition mechanism remain elusive. In this study, we present biophysical analyses and the structure of the dimerization and DNA binding domains of DR2539 in its holo form and in complex with the 21 bp pseudo-palindromic repeat of the dr1709 promotor region. These findings shed light into the activation and recognition mechanisms. The dimer presents eight manganese binding sites that induce structural conformations essential for DNA binding. The analysis of the protein-DNA interfaces elucidates the significance of Tyr59 and helix H3 sequence in the interaction with the DNA. Finally, the structure in solution as determined by small angle X-ray scattering experiments and supported by AlphaFold modelling provides a model illustrating the conformational changes induced upon metal binding.

biophysics↗

bioRxiv2024

Substrate-dependent oxidative inactivation of a W-dependent formate dehydrogenase involving selenocysteine displacement.

Metal-dependent formate dehydrogenases are very promising targets for enzyme optimization and design of bio-inspired catalysts for CO2 reduction, towards novel strategies for climate change mitigation. For effective application of these enzymes, the catalytic mechanism must be fully understood, and the molecular determinants clarified. Despite numerous studies, several doubts persist, namely regarding the role played by the possible dissociation of the SeCys ligand from the Mo/W active site. Additionally, the O2 sensitivity of these enzymes must also be understood as it poses an important obstacle for biotechnological applications. Here we present a combined biochemical, spectroscopic, and structural characterization of Desulfovibrio vulgaris FdhAB (DvFdhAB) when exposed to oxygen in the presence of a substrate (formate or CO2). This study reveals that O2 inactivation is promoted by the presence of either substrate and involves forming a new species in the active site, captured in the crystal structures, where the SeCys ligand is displaced from tungsten coordination and replaced by a dioxygen or peroxide molecule. This new form was reproducibly obtained and supports the conclusion that, although W-DvFdhAB can catalyze the oxidation of formate in the presence of oxygen for some minutes, it gets irreversibly inactivated after prolonged O2 exposure in the presence of either substrate. These results reveal that oxidative inactivation does not require reduction of the metal, as widely assumed, as it can also occur in the oxidized state in the presence of CO2.

biochemistry↗

bioRxiv2022

Hypotrochoidal scaffolds for cartilage regeneration

The main function of articular cartilage is to provide a low friction surface and protect the underlying subchondral bone. The extracellular matrix composition of articular cartilage mainly consists of glycosaminoglycans and collagen type II. Specifically the collagen type II organization has a characteristic organization in three distinct zones; (1) the superficial zone which has collagen fibers oriented parallel to the surface, (2) the intermediate zone where there is no predominant orientation, and (3) the deep zone which shows a high orientation with fibers perpendicular to the underlying bone. Collagen type II fibers in these 3 zones take an arch-like organization that can be mimicked with segments of a hypotrochoidal curve. In this study, a script was developed that allowed the fabrication of scaffolds with a hypotrochoidal design. This design was investigated and compared to a regular 0-90 woodpile design. The results showed that the hypotrochoidal design was successfully fabricated. Micro-CT analyses divided the areas of the scaffold in their distinct zones. In addition, the mechanical analyses revealed that the hypotrochoidal design had a lower component Youngs modulus while the toughness and strain at yield were higher compared to the woodpile design. Fatigue tests showed that the hypotrochoidal design lost more energy per cycle due to the damping effect of the unique microarchitecture. Finite element analyses revealed that the hypotrochoidal design had an improved stress distribution compared to the 0-90 woodpile design due to the lower component stiffness. In addition, data from cell culture under dynamic stimulation demonstrated that the collagen type II deposition was improved in the hypotrochoidal design. Finally, Alcian blue staining revealed that the areas where the stress was higher during the stimulation produced more glycosaminoglycans. Our results highlight a new and simple scaffold design based on hypotrochoidal curves that could be used for cartilage tissue engineering.

bioengineering↗

bioRxiv2021

Controlling fibroblast fibrinolytic activity allows for the bio-engineering of stable connective tissue equivalents

In tissue engineering, cell origin is important to ensure outcome quality. However, the impact of the cell type chosen for seeding in a biocompatible matrix has been less investigated. Here, we investigated the capacity of primary and immortalized fibroblasts of distinct origins to degrade a gelatin/alginate/fibrin (GAF)-based biomaterial. We further established that fibrin was targeted by degradative fibroblasts through the secretion of fibrinolytic matrix-metalloproteinases (MMPs) and urokinase, two types of serine protease. Finally, we demonstrated that besides aprotinin, specific targeting of fibrinolytic MMPs and urokinase led to cell-laden GAF stability for at least several days. These results support the use of specific strategies to tune fibrin-based biomaterials degradation over time. It emphasizes the need to choose the right cell type and further bring targeted solutions to avoid the degradation of fibrin-containing hydrogels or bioinks.

bioengineering↗

bioRxiv2021

Effect of reduced graphene oxide (rGO) compaction degree and concentration on rGO-polymer composites printability and cell interactions

Graphene derivatives combined with polymers have attracted enormous attention for bone tissue engineering applications. Among others, reduced graphene oxide (rGO) is one of the preferred graphene-based fillers for the preparation of composites via melt compounding, and their further processing into 3D scaffolds, due to its established large-scale production method, thermal stability, and electrical conductivity. In this study, rGO (low bulk density 10g/L) was compacted by densification using a solvent (either acetone or water) prior to melt compounding, to simplify its handling and dosing into a twin-screw extrusion system. The effects of rGO bulk density (medium and high), densification solvent, and rGO concentration (3, 10 and 15% in weight) on rGO dispersion within the composite, electrical conductivity, printability and cell-material interactions were studied. High bulk density rGO (90 g/L) occupied a low volume fraction within polymer composites, offering poor electrical properties but a reproducible printability up to 15 wt% rGO. On the other hand, the volume fraction within the composites of medium bulk density rGO (50 g/L) was higher for a given concentration, enhancing rGO particle interactions and leading to enhanced electrical conductivity, but compromising the printability window. For a given bulk density (50 g/L), rGO densified in water was more compacted and offered poorer dispersability within the polymer than rGO densified in acetone, and resulted in scaffolds with poor layer bonding or even lack of printability at high rGO percentages. A balance in printability and electrical properties was obtained for composites with medium bulk density rGO densified in acetone. Here, increasing rGO concentration led to more hydrophilic composites with a noticeable increase in protein adsorption. Moreover, scaffolds prepared with such composites presented antimicrobial properties even at low rGO contents (3 wt%). In addition, the viability and proliferation of human mesenchymal stromal cells (hMSCs) was maintained on scaffolds with up to 15% rGO and with enhanced osteogenic differentiation on 3% rGO scaffolds.

bioengineering↗

bioRxiv2021

Additive manufactured scaffolds for bone tissue engineering: physical characterization of thermoplastic composites with functional fillers

Thermoplastic polymer - filler composites are excellent materials for bone tissue engineering (TE) scaffolds, combining the functionality of fillers with suitable load bearing ability, biodegradability, and additive manufacturing (AM) compatibility of the polymer. Two key determinants of their utility are their rheological behavior in the molten state, determining AM processability, and their mechanical load-bearing properties. We report here the characterization of both these physical properties for four bone TE relevant composite formulations with poly(ethylene oxide terephthalate) / poly(butylene terephthalate (PEOT/PBT) as a base polymer, which is often used to fabricate TE scaffolds. The fillers used were reduced graphene oxide (rGO), hydroxyapatite (HA), gentamycin intercalated in zirconium phosphate (ZrP-GTM) and ciprofloxacin intercalated in MgAl layered double hydroxide (MgAl-CFX). The rheological assessment showed that generally the viscous behavior dominated the elastic behavior (G > G) for the studied composites, at empirically determined extrusion temperatures. Coupled rheological-thermal characterization of ZrP-GTM and HA composites showed that the fillers increased the solidification temperatures of the polymer melts during cooling. Both these findings have implications for the required extrusion temperatures and bonding between layers. Mechanical tests showed that the fillers generally made the polymer stiffer but more brittle in proportion to the filler fractions. Furthermore, the elastic moduli of scaffolds did not directly correlate with the corresponding bulk material properties, implying composite-specific AM processing effects on the mechanical properties. Lastly, we show computational models to predict multi-material scaffold elastic moduli using measured single material scaffold and bulk moduli. The reported characterizations are essential for assessing the AM processability and ultimately the suitability of the manufactured scaffolds for the envisioned bone regeneration application.

bioengineering↗

bioRxiv2021

Effect of Highly Loaded Nanohydroxyapatite Composite Scaffolds Prepared via Melt Extrusion Additive Manufacturing on the Osteogenic Differentiation of Human Mesenchymal Stromal Cells

The field of bone tissue engineering seeks to mimic the bone extracellular matrix composition, balancing the organic and inorganic components. In this regard, additive manufacturing (AM) of highly loaded polymer-calcium phosphate (CaP) composites holds great promise towards the design of bioactive scaffolds. Yet, the biological performance of such scaffolds is still poorly characterized. In this study, melt extrusion AM (ME-AM) was used to fabricate poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT)-nanohydroxyapatite (nHA) scaffolds with up to 45 wt% nHA, which presented significantly enhanced compressive mechanical properties, to evaluate their in vitro osteogenic potential as a function of nHA content. While osteogenic gene upregulation and matrix mineralization were observed on all scaffold types when cultured in osteogenic media, human mesenchymal stromal cells did not present an explicitly clear osteogenic phenotype, within the evaluated timeframe, in basic media cultures (i.e. without osteogenic factors). Yet, due to the adsorption of calcium and inorganic phosphate ions from cell culture media and simulated body fluid, the formation of a CaP layer was observed on PEOT/PBT-nHA 45 wt% scaffolds, which is hypothesized to account for their osteoinductivity in the long term in vitro, and osteoconductivity in vivo.

bioengineering↗

bioRxiv2020

Mimicking the Human Tympanic Membrane: the Significance of Geometry

The human tympanic membrane (TM) captures sound waves reaching the outer ear from the environment and transforms them into mechanical motion. The successful transmission of these acoustic vibrations in varying frequency ranges is attributed to the structural architecture of the TM. However, a limited knowledge is available on the contribution of its discrete anatomical features, which is important to fabricate functional biomimetic TM replacements. This work synergizes theoretical and experimental approaches toward understanding the significance of geometry in tissue engineered TM scaffolds. Three test designs along with a plain control were chosen to decouple some of the dominant structural attributes, such as, the radial and circumferential alignment of the collagen fibrils. In silico models suggested a geometrical dependency of their mechanical and acoustical responses, where the presence of radially aligned fibers was observed to have a more prominent effect compared to their circumferential counterparts. Following which, a hybrid fabrication strategy combining electrospinning and additive manufacturing was optimized to manufacture hierarchical scaffolds within the dimensions of the native TM. The experimental characterizations conducted using macro-indentation and laser Doppler vibrometry were in line with the computational models. Finally, biological studies performed with human dermal fibroblasts and human mesenchymal stromal cells, revealed a favorable influence of scaffold hierarchy on cellular alignment and subsequent collagen deposition. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/383299v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@16b3653org.highwire.dtl.DTLVardef@1bbc47forg.highwire.dtl.DTLVardef@619ad8org.highwire.dtl.DTLVardef@1fd1071_HPS_FORMAT_FIGEXP M_FIG Graphical abstract. Schematic diagram illustrating the overall flowchart of the work. 3D: three-dimensional; ES: electrospinning; FDM: fused deposition modeling; TM: tympanic membrane. C_FIG

bioengineering↗

bioRxiv2020

A hybrid additive manufacturing platform to create bulk and surface composition gradients on scaffolds for tissue regeneration

Scaffolds with gradients of physico-chemical properties and controlled 3D architectures are crucial for engineering complex tissues. These can be produced using multi-material additive manufacturing (AM) techniques. However, they typically only achieve discrete gradients using separate printheads to vary compositions. Achieving continuous composition gradients, to better mimic tissues, requires material dosing and mixing controls. No such AM solution exists for most biomaterials. Existing AM techniques also cannot selectively modify scaffold surfaces to locally stimulate cell adhesion. We report a hybrid AM solution to cover these needs. On one platform, we combine a novel dosing- and mixing-enabled, dual-material printhead with an atmospheric pressure plasma jet to selectively activate/coat scaffold filaments during manufacturing. We fabricated continuous composition gradients in both 2D hydrogels and 3D thermoplastic scaffolds. We demonstrated an improvement in mechanical properties of continuous gradients compared to discrete gradients in the 3D scaffolds, and the ability to selectively enhance cell adhesion.Competing Interest StatementP.S. and A.P. own part of the plasma jet manufacturer Nadir s.r.l.. E.V.F. is also affiliated with Nadir. R.S., L.M. and C.M. have applied for a patent (EP18200211.3, submitted: 12 Oct. 2018, PCT/EP2019/077519, submitted: 10 Oct. 2019) on the developed printhead and aim to license it to interested printer companies. M.C.-T. has no financial interests to declare.View Full Text

bioengineering↗

bioRxiv2020

3D additive manufactured composite scaffolds with antibiotic-loaded lamellar fillers for bone infection prevention and tissue regeneration

Bone infections following open bone fracture or implant surgery remain a challenge in the orthopedics field. In order to avoid high doses of systemic drug administration, optimized local antibiotic release from scaffolds is required. 3D additive manufactured (AM) scaffolds made with biodegradable polymers are ideal to support bone healing in non-union scenarios and can be given antimicrobial properties by the incorporation of antibiotics. In this study, ciprofloxacin and gentamicin intercalated in the interlamellar spaces of magnesium aluminum layered double hydroxides (MgAl) and -zirconium phosphates (ZrP), respectively, are dispersed within a thermoplastic polymer by melt compounding and subsequently processed via high temperature melt extrusion AM ([~]190 {degrees}C) into 3D scaffolds. The inorganic fillers enable a sustained antibiotics release through the polymer matrix, controlled by antibiotics counterions exchange or pH conditions. Importantly, both antibiotics retain their functionality after the manufacturing process at high temperatures, as verified by their activity against both Gram + and Gram - bacterial strains. Moreover, scaffolds loaded with filler-antibiotic do not impair human mesenchymal stromal cells osteogenic differentiation, allowing matrix mineralization and the expression of relevant osteogenic markers. Overall, these results suggest the possibility of fabricating dual functionality 3D scaffolds via high temperature melt extrusion for bone regeneration and infection prevention.

bioengineering↗

bioRxiv2019

Improving cell distribution on 3D additive manufactured scaffolds through engineered seeding media density and viscosity

In order to ensure the long-term in vitro and in vivo functionality of cell-seeded 3D scaffolds, an effective and reliable method to control cell seeding efficiency and distribution is crucial. Static seeding on 3D additive manufactured scaffolds made of synthetic polymers still remains challenging, as it often results in poor cell attachment, high cell sedimentation and non-uniform cell distribution, due to gravity and to the intrinsic macroporosity and surface chemical properties of the scaffolds. In this study, the bio-inert macromolecules dextran and Ficoll were used for the first time as temporary supplements to alter the viscosity and density of the seeding media, respectively, and improve the static seeding output. The addition of these macromolecules drastically reduced the cell sedimentation velocities, allowing for homogeneous cell attachment to the scaffold filaments. Both dextran- and Ficoll-based seeding methods supported human mesenchymal stromal cells viability and osteogenic differentiation post-seeding. Interestingly, the improved cell distribution led to increased matrix production and mineralization compared to scaffolds seeded by conventional static method. These results suggest a simple and universal method for an efficient seeding of 3D additive manufactured scaffolds, independent of their material and geometrical properties, and applicable for bone and various other tissue regeneration.

bioengineering↗