Publications

The performance of single-chain polymeric nanoparticles (SCPNs) in biomedical applications highly depends on their conformational stability in cellular environments. Until now, such stability studies are limited to 2D cell culture models, which do not recapitulate the 3D tumor microenvironment well. Here, a microfluidic tumor-on-a-chip model is introduced that recreates the tumor milieu and allows in-depth insights into the diffusion, cellular uptake, and stability of SCPNs. The chip contains Matrigel/collagen-hyaluronic acid as extracellular matrix (ECM) models and is seeded with cancer cell MCF7 spheroids. With this 3D platform, it is assessed how the polymer's microstructure affects the SCPN's behavior when crossing the ECM, and evaluates SCPN internalization in 3D cancer cells. A library of SCPNs varying in microstructure is prepared. All SCPNs show efficient ECM penetration but their cellular uptake/stability behavior depends on the microstructure. Glucose-based nanoparticles display the highest spheroid uptake, followed by charged nanoparticles. Charged nanoparticles possess an open conformation while nanoparticles stabilized by internal hydrogen bonding retain a folded structure inside the tumor spheroids. The 3D microfluidic tumor-on-a-chip platform is an efficient tool to elucidate the interplay between polymer microstructure and SCPN's stability, a key factor for the rational design of nanoparticles for targeted biological applications.© 2024 The Authors. Small Methods published by Wiley-VCH GmbH.

JTD Keywords: 3d cancer cell uptake, Cancer cells, Cell culture, Cell uptake, Cellular uptake, Diseases, Ecm penetration, Extracellular matrices, Extracellular matrix penetration, Functional polymers, Hydrogen bonds, Medical applications, Microfluidics, Microstructure, Nanoparticles, Polymeric nanoparticles, Scpns, Single chains, Single-chain polymeric nanoparticle, Stability, Tumor-on-a-chip, Tumors

The intestine is a complex tissue with a characteristic three-dimensional (3D) crypt-villus architecture, which plays a key role in the intestinal function. This function is also regulated by the intestinal stroma that actively supports the intestinal epithelium, maintaining the homeostasis of the tissue. Efforts to account for the 3D complex structure of the intestinal tissue have been focused mainly in mimicking the epithelial barrier, while solutions to include the stromal compartment are scarce and unpractical to be used in routine experiments. Here we demonstrate that by employing an optimized bioink formulation and the suitable printing parameters it is possible to produce fibroblast-laden crypt-villus structures by means of digital light projection stereolithography (DLP-SLA). This process provides excellent cell viability, accurate spatial resolution, and high printing throughput, resulting in a robust biofabrication approach that yields functional gut mucosa tissues compatible with conventional testing techniques.Copyright © 2023 Elsevier B.V. All rights reserved.

JTD Keywords: 3d microstructure, barrier, cells, epithelial-stromal interactions, gelma-pegda soft hydrogels, growth, hydrogel, intestinal mucosa model, methacrylamide, microfabrication, proliferation, scaffold, stereolithography, 3d bioprinting, 3d microstructure, Epithelial-stromal interactions, Fibroblasts, Gelma-pegda soft hydrogels, Intestinal mucosa model

Actual polymeric wound closure devices are not optimal for load-bearing applications due to the low mechanical properties and the risk of inflammation and bacterial infection mainly produced by multifil-ament and braided configurations. Biodegradable metallic Zn alloys are promising materials candidates; however, mechanical performance, corrosion behaviour, and biological response should be controlled in order to inhibit the risk of inflammation and bacterial infection. To this end, a Zn-2Ag (2 wt% Ag) alloy was processed by ECAP to evaluate the concurrent combined effect of grain refinement and Ag alloying on biodegradation and antibacterial activity. Two ECAP cycles were successfully applied to a Zn-2Ag alloy obtaining a homogeneous ultra-fine-grained structure in which nanoindentation maps suggested isotro-pic mechanical properties. Lower UTS and YS with higher elongation was reported after ECAP with similar corrosion rates as before processing. ECAP processed samples showed a homogeneous Ag+ release below the minimum inhibitory concentration for S. Aureus and no antibacterial effect was observed by diffusion. As expected, the presence of Ag in Zn-Ag alloys reduced bacterial attachment. Nevertheless, ECAP processed Zn-2Ag provided an excellent antibacterial activity after 3 h probably caused by the uniformly degraded and thus, non- stable, surface observed after bacterial adhesion.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

JTD Keywords: Behavior, Binary alloys, Biodegradable zinc-alloys, Biomaterials, Equal channel angular pressing, Grain-refinement, In-vitro degradation, Mg, Microstructure, Nanoindentation, Progress, Staphylococcus-aureus, Temperature superplasticity, Ultrafine-grained materials, Zinc alloys, Zn alloys

In the recent decades, zinc (Zn) and its alloys have been drawing attention as promising candidates for bioresorbable cardiovascular stents due to its degradation rate more suitable than magnesium (Mg) and iron (Fe) alloys. However, its mechanical properties need to be improved in order to meet the criteria for vascular stents. This work investigates the mechanical properties, biodegradability and biocompatibility of Zn-Mg and Zn-Cu alloys in order to determine a proper alloy composition for optimal stent performance. Nanoindentation measurements are performed to characterize the mechanical properties at the nanoscale as a function of the Zn microstructure variations induced by alloying. The biodegradation mechanisms are discussed and correlated to microstructure, mechanical performance and bacterial/cell response. Addition of Mg or Cu alloying elements refined the microstructure of Zn and enhanced yield strength (YS) and ultimate tensile strength (UTS) proportional to the volume fraction of secondary phases. Zn-1Mg showed the higher YS and UTS and better performance in terms of degradation stability in Hanks’ solution. Zn-Cu alloys presented an antibacterial effect for S. aureus controlled by diffusion mechanisms and by contact. Biocompatibility was dependent on the degradation rate and the nature of the corrosion products.

JTD Keywords: behavior, biocompatibility, biodegradable metals, bioresorbable metals, bioresorbable scaffold, copper, corrosion properties, elastic-modulus, galvanic corrosion, microstructure, nanoindentation, redox homeostasis, zinc, Biocompatibility, Bioresorbable metals, Galvanic corrosion, Nanoindentation, Room-temperature superplasticity, Zinc alloys

© 2020 Hydrolytic degradation of poly(4-hydroxybutyrate) (P4HB) films has been studied considering media of different pH values (i.e., 3, 7 and 10) and temperatures (i.e., 37 and 55 °C). Enzymatic degradation has also been evaluated at physiological conditions using two different lipases: Pseudomonas cepacia and Rhizopus oryzae. Different bulk and surface erosion mechanisms with random chain scissions and successive removal of monomer units have been supported through weight loss measurements, molecular weight determinations by GPC and NMR spectroscopy and changes on thermal properties by DSC. Thermal annealing during exposure to different media and even degradation influenced on the melting temperature and crystallinity of samples, as well as on the lamellar geometrical parameters as evaluated by SAXS. Enzymatic degradation was ideal to selectively eliminate the amorphous regions and highlight the spherulitic morphology. Presence of ringed textures were therefore evident in bright field optical micrographs in addition to SEM images, namely observations under polarized light was not necessary to distinguish the presence of banded spherulites. Rhizopus oryzae was revealed to be the most suitable enzyme to crop out the P4HB spherulites that form part of the initial smooth surfaces of solvent casting films. After determining the appropriate activity and exposure time, the presence of rings constituted by cooperative C-shaped edge-on lamellae and flat-on lamellae was highlighted.

JTD Keywords: biodegradable polymers, enzymatic degradation, films, hydrolytic degradation, microstructure, thermal properties, Biodegradable polymers, Enzymatic degradation, Films, Hydrolytic degradation, Microstructure, Poly(4-hydroxybutyrate), Thermal properties

A comprehensive study of progressively ground/polished 3Y-TZP was performed with the aim of better understanding the mechanisms driving the microstructural modifications observed after such procedures, and identifying the processing parameters leading to optimal microstructures (i.e. ageing-protective and damage-free). Gradually ground/polished surfaces were produced, yielding four different topographies of increasing roughness (grades 1–4) and two different textures (unidirectionally, U, and multidirectionally, M). Phase transformation, microstructure and residual stresses were investigated by means of advanced characterization techniques. It was found that low-roughness mildly ground/polished specimens (i.e. 2-M/U) presented a nanometric layer with the ageing-related protective features generally associated with coarsely ground specimens. A lower limit for grain refinement in terms of surface abrasion was also found, in which partial recrystallization took place (i.e. 1-M/U). A mathematical relation was established between average surface roughness (Sa), monoclinic volume fraction (Vm) and surface compressive residual stresses, demonstrating that if the processing parameters are controlled, both Vm and residual stresses can be predicted by the measurement of Sa.

JTD Keywords: Grinding, Microstructure, Phase transformation, Residual stresses, Zirconia

It is known that cells respond strongly to microtopography. However, cellular mechanisms of response are unclear. Here, we study wild-type fibroblasts responding to 25 μm2 posts and compare their response to that of FAK-/- fibroblasts and fibroblasts with PMA treatment to stimulate protein kinase C (PKC) and the small g-protein Rac. FAK knockout cells modulated adhesion number and size in a similar way to cells on topography; that is, they used more, smaller adhesions, but migration was almost completely stalled demonstrating the importance of FAK signaling in contact guidance and adhesion turnover. Little similarity, however, was observed to PKC stimulated cells and cells on the topography. Interestingly, with PKC stimulation the cell nuclei became highly deformable bringing focus on these surfaces to the study of metastasis. Surfaces that aid the study of cellular migration are important in developing understanding of mechanisms of wound healing and repair in aligned tissues such as ligament and tendon.

JTD Keywords: Adhesion, Cell migration, Cell morphology, Focal adhesion kinase, Microstructures

The present study reports a novel approach for the design and fabrication of polylactic acid (PLA) microparticle-based scaffolds with microstructural properties suitable for bone and cartilage regeneration. Macroporous PLA scaffolds with controlled shape were fabricated by means of a semicontinuous process involving (1) microfluidic emulsification of a PLA/ethyl lactate solution (5% w/v) in a span 80/paraffin oil solution (3% v/v) followed by (2) particles coagulation/assembly in an acetone/water solution for the development of a continuous matrix. Porous scaffolds prepared from particles with monomodal or bimodal size distribution, overall porosity ranges from 93 to 96%, interparticles porosity from 41 to 54%, and static compression moduli from 0.3 to 1.4 MPa were manufactured by means of flow rate modulation of of the continuous phase during emulsion. The biological response of the scaffolds was assessed in vitro by using bone marrow-derived rat mesenchymal stem cells (MSCs). The results demonstrated the ability of the scaffolds to support the extensive and uniform three-dimensional adhesion, colonization, and proliferation of MSCs within the entire construct.

JTD Keywords: Green solvent, Microfluidic, Microstructure, Stem cells, Scaffold

In natural tissues, the extracellular matrix composition, cell density and physiological properties are often non-homogeneous. Here we describe a model system, in which the distribution of cells throughout tissue engineering scaffolds after perfusion seeding can be influenced by the pore architecture of the scaffold. Two scaffold types, both with gyroid pore architectures, were designed and built by stereolithography: one with isotropic pore size (412 ± 13 [mu]m) and porosity (62 ± 1%), and another with a gradient in pore size (250-500 [mu]m) and porosity (35%-85%). Computational fluid flow modelling showed a uniform distribution of flow velocities and wall shear rates (15-24 s-1) for the isotropic architecture, and a gradient in the distribution of flow velocities and wall shear rates (12-38 s-1) for the other architecture. The distribution of cells throughout perfusion-seeded scaffolds was visualised by confocal microscopy. The highest densities of cells correlated with regions of the scaffolds where the pores were larger, and the fluid velocities and wall shear rates were the highest. Under the applied perfusion conditions, cell deposition is mainly determined by local wall shear stress, which, in turn, is strongly influenced by the architecture of the pore network of the scaffold.

JTD Keywords: Scaffolds, Microstructure, Cell adhesion, Confocal microscopy, Image analysis, Computational fluid dynamics

New fabrication technologies and, in particular, new nanotechnologies have provided biomaterial and biomedical scientists with enormous possibilities when designing customized supports and scaffolds with controlled nanoscale topography and chemistry. The main issue now is how to effectively design these components and choose the appropriate combination of structure and chemistry to tailor towards applications as challenging and complex as stem cell differentiation. Occasionally, an incomplete knowledge of the fundamentals of biological differentiation process has hampered this issue. However, the recent technological advances in creating controlled cellular microenvironments can be seen as a powerful tool for furthering fundamental biology studies. This article reviews the main strategies followed to achieve solutions to this challenge, particularly emphasizing the working hypothesis followed by the authors to elucidate the mechanisms behind the observed effects of structured surfaces on cell behavior.

JTD Keywords: Cell pattering, Differentiation, Microcontact printing, Micropatterning, Microstructure, Nanoimprinting, Nanostructure, Stem cells

Substrate topography, independently of substrate chemistry, has been reported to have significant effects on cell behaviour. Based on the use of fabrication techniques developed by the silicon microtechnology industry, numerous studies can now be found in the literature analyzing cell behaviour as to various micro- and nanofeatures such as lines, wells, holes and more. Most of these works have been found to relate the micro- and nano-sized topographical features with cell. orientation, migration, morphology and proliferation. In recent papers, even the influence of substrate nanotopography on cell gene expression and differentiation has been pointed out. However, despite the large number of papers published on this topic, significant general trends in cell behaviour are difficult to establish due to differences in cell type, substrate material, feature aspect-ratio, feature geometry and parameters measured. This paper intends to compile and review the relevant existing information on the behaviour of cells on micro- and nano-structured artificial substrates and analyze possible general behavioural trends.

JTD Keywords: Microstructure, Topography, Cell behaviour, Cell morphology, Cell orientation

Recent studies on 2D substrates have revealed the importance of surface properties in affecting cell behaviour. In particular, surface topography appears to influence and direct cell migration. The development of new technologies of hot embossing and micro-imprinting has made it possible to study cell interactions with controlled micro features and to determine how these features can affect cell behaviour. Several studies have been carried out on the effect of microstructures on cell adhesion, cell guidance and cell proliferation. However, there is still a lack of knowledge on how these features affect mesenchymal stem cell differentiation. This study was designed to evaluate whether highly controlled microstructures on PMMA could induce rMSC differentiation into an osteogenic lineage. Structured PMMA was seeded with rMSC and cell number; cell morphology and cell differentiation were evaluated. Results confirm that microstructures not only affect cell proliferation and alignment but also have a synergistic effect with osteogenic medium on rMSC differentiation into mature osteoblasts.

JTD Keywords: Mesenchymal stem cells, Osteoblasts, Topography, Microstructures

A technique for imparting micro- and nano-structured topography into the surface of freestanding thin sheets of chitosan is described. Both micro- and nanometric surface structures have been produced using soft lithography. The soft lithography method, based on solvent evaporation, has allowed structures similar to 60 nm tall and similar to 500 X 500 nm(2) to be produced on freestanding similar to 0.5 mm thick sheets of the polymer when cured at 293 K, and structures similar to 400 nm tall and 5 X 5 mu m(2) to be produced when cured at 283 K. Nonstructured chitosan thin sheets (similar to 200 mu m thick) show excellent optical transmission properties in the visible portion of the electromagnetic spectrum. The structured sheets can be used for applications where optical microscopic analysis is required, such as cell interaction experiments and tissue engineering.

JTD Keywords: Chitin/chitosan, Microstructure, Nanotopography, Polymerization, Soft lithography

Micro- and nanoscale protein patterns have been produced via a new contact printing method using a nanoimprint lithography apparatus. The main novelty of the technique is the use of poly(methyl methacrylate) (PMMA) instead of the commonly used poly(dimethylsiloxane) (PDMS) stamps. This avoids printing problems due to roof collapse, which limits the usable aspect ratio in microcontact printing to 10:1. The rigidity of the PMMA allows protein patterning using stamps with very high aspect ratios, up to 300 in this case. Conformal contact between the stamp and the substrate is achieved because of the homogeneous pressure applied via the nanoimprint lithography instrument, and it has allowed us to print lines of protein similar to 150 nm wide, at a 400 nm period. This technique, therefore, provides an excellent method for the direct printing of high-density sub-micrometer scale patterns, or, alternatively, micro-/nanopatterns spaced at large distances. The controlled production of these protein patterns is a key factor in biomedical applications such as cell-surface interaction experiments and tissue engineering.

JTD Keywords: Soft lithography, Cell-adhesion, Microstructures, Fabrication, Stability, Patterns

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JTD Keywords: Self-assembled monolayers, High-aspect-ratio, Dip-pen nanolithography, Langmuir-blodgett-films, Conducting polymer, Enzymes, Microstructures, Immunosensors, Fabrication, Stability