Biomedical subjects

Mathis O Riehle

Publications and source records attributed to Mathis O Riehle.

16 recordsLinked to original sources

PubMed2006

Air-trapping on biocompatible nanopatterns.

The occurrence of air-trapping inside poly-eta-caprolactone nanopits was investigated by measuring the contact angles of water droplets on a set of defined nanotopographies. It is shown that the advancing angles follow the Cassie-Baxter theory, thus revealing the presence of air bubbles inside the biodegradable nanopatterns. The importance of these observations for the definition of hydrophilicity/hydrophobicity and in the context of in vitro cell behavior is discussed.

Absorption↗

PubMed2006

Fluorescent aromatic platforms for cell patterning.

This paper describes a simple experimental method of patterning fluorescent organic dyes, fluorescein, and rhodamine on gold substrates by microcontact printing techniques. The development of this step-by-step protocol has allowed us to prepare striped and squared micropatterns with poly(ethylene glycol) (PEG) linkers terminated by these fluorophores using a fast, easy, and inexpensive technique. Although the rest of the surface was covered with aliphatic molecules (methyl terminated), human fibroblasts demonstrated an unexpected response, aligning themselves according to the aromatic patterns, despite the presence of PEG, which is a cell resistant molecule, in the fluorescent regions.

Cell Adhesion↗

PubMed2006

Nanoparticle targeting at cells.

Gold nanoparticles have been used for analytical and biomedical purposes for many years. In fact, the labeling of targeting molecules with nanoparticles has revolutionized the visualization of cellular or tissue components by electron microscopy. We report in this study the derivatization of tiopronin-protected nanoparticles with ethylenediamine and poly(ethylene glycol) bis(3-aminopropyl) terminated and their functionalization with the GRGDSP peptide sequence by a straightforward and economical methodology. The particles were subsequently tested in vitro with a human fibroblast cell line to determine the biocompatibility, and the cell-particle interactions, using fluorescence and scanning electron microscopies. The results indicate that tiopronin gold nanoparticles aggregate due to culture medium proteins, whereas the tiopronin gold nanoparticles derivatized with ethylenediamine induce endocytosis, and the same nanoparticles derivatized with poly(ethylene glycol) derivative promote particle-cell adhesion.

Cell Adhesion↗

PubMed2006

Chondrocyte aggregation on micrometric surface topography: a time-lapse study.

Cellular aggregation or mesenchymal "condensation" is a prerequisite in the process of chondrogenesis. It has been observed that during in vitro engineering of cartilage, chondrocytes form aggregates in the initial cell seeding process of polymer scaffolds. However, the exact mechanism behind this aggregation has yet to be elucidated, although cell collision has been implicated. As all polymers have a surface topography, we hypothesized that topography may play a role in chondrocyte aggregation. 1(st) and 2(nd) passage chondrocytes were seeded on micrometric topography ranging from 0.75 to 8 microm in depth and 5 to 12.5 microm in width. Both 1(st) and 2(nd) passage cells formed aggregates as cells collided, and larger aggregates formed as aggregates collided with each other on the grooves. Furthermore, aggregates migrated parallel to the direction of the groove long axis. F-actin organization was altered only in the cellular layer in direct contact with the surface; stress fibers oriented in the direction of the groove long axis. Chondrocytes maintained type II collagen expression on all groove depths. This study shows that micrometric grooves could be an effective means for studying chondrocyte aggregation, and could additionally be utilized in the regeneration of cartilage.

Animals↗

PubMed2005

Human fibroblast reactions to standard and electropolished titanium and Ti-6Al-7Nb, and electropolished stainless steel.

Stainless steel (SS), titanium (cpTi), and Ti-6Al-7Nb (TAN) are frequently used metals in orthopedic internal fracture fixation. Although reactivity to SS and cpTi are noted in reference, the soft tissue compatibility of TAN has not been comprehensively studied. This study focuses on the in vitro soft tissue compatibility of TAN in comparison to SS and cpTi using a human fibroblast model. The industrial standard surface finishes of these three materials vary considerably in view of their use in similar applications. To distinguish between material parameters of topography and chemistry, we have included electropolished (e.p) counterparts of the standard preparations of cpTi and TAN in the study (standard SS is e.p). All materials were characterized using atomic force microscopy, profilometry, and scanning electron microscopy. Our findings demonstrate that cell morphology and growth rate was similar for SS, and e.p. cpTi and TAN, with cells well spread and forming a confluent monolayer by 10 days. Cell growth on standard cpTi was similar to the electropolished samples; however, they showed a less spread morphology with more filopodia and surface ruffling present. Cell morphology on standard TAN was rounded or elongated and proliferation was inhibited at all time points, with possible cell necrosis by day 10. We found evidence of endocytosis of beta-phase particles originating from the standard TAN surface. We believe that the particle uptake coupled with the characteristic surface topography contribute to the noncytocompatibility of fibroblasts on standard TAN.

Biocompatible Materials↗

PubMed2005

The plastidic DNA replication enzyme complex of Plasmodium falciparum.

The replication and repair of organellar genomes in the malaria parasite Plasmodium falciparum is poorly understood. We have assessed the properties of an open reading frame Pfprex (formerly known as pom1) and confirm that it specifies a multi-domain polypeptide with DNA primase, DNA helicase, DNA polymerase and 3'-5' exonuclease activities. The sequence of the primase/helicase domain is phylogenetically related to the T7-bacteriophage gene 4 product and mammalian mitochondrial helicase, Twinkle. Despite that, the N-terminal sequence of this multi-domain polypeptide directs a green fluorescent protein reporter specifically to the P. falciparum apicoplast and not to the mitochondrion. Phylogenetic analysis placed the DNA polymerase sequence with the family A bacterial polymerases, most closely to those of the thermophilic Aquifex species. Notably, the malarial enzyme was optimally active at 75 degrees C. Pfprex is the first example of a gene encoding contiguous DNA polymerase, DNA primase and DNA helicase components. We propose it has a key role in replication of the malarial plastid genome, a validated drug target.

Animals↗

PubMed2005

Superhydrophobicity and superhydrophilicity of regular nanopatterns.

The hydrophilicity, hydrophobicity, and sliding behavior of water droplets on nanoasperities of controlled dimensions were investigated experimentally. We show that the "hemi-wicking" theory for hydrophilic SiO(2) samples successfully predicts the experimental advancing angles and that the same patterns, after silanization, become superhydrophobic in agreement with the Cassie-Baxter and Wenzel theories. Our model topographies have the same dimensional scale of some naturally occurring structures that exhibit similar wetting properties. Our results confirm that a forest of hydrophilic/hydrophobic slender pillars is the most effective superwettable/water-repellent configuration. It is shown that the shape and curvature of the edges of the asperities play an important role in determining the advancing angles.

Journal Article↗

PubMed2004

Fibroblast response to a controlled nanoenvironment produced by colloidal lithography.

It is thought that by understanding how cells respond to topography, that better tissue engineering may be achievable. An important consideration in the cellular environment is topography. The effects of microtopography have been well documented, but the effects of nanotopography are less well known. Previously, methods of nanofabrication have been costly and time-consuming, but research by engineers, physicists, and chemists is starting to allow the production of nanostructures using low-cost techniques. In this report, nanotopography is specifically considered. Controlled patterns of 160 nm high nanocolumns were produced for in vitro cell culture using colloidal lithography. By studying cell adhesion with time and cytoskeletal (actin, tubulin, and vimentin) maturity, insight has been gained as to how fibroblasts adhere to these nanofeatures.

Actins↗

PubMed2004

Attempted endocytosis of nano-environment produced by colloidal lithography by human fibroblasts.

Control of the cells' nanoenvironment is likely to be important in the future of cell and tissue engineering. Microtopography has been shown to provide cues to cells that elicit a large range of cell responses, including control of adhesion, morphology, apoptosis and gene regulations. Now, researchers are focusing on nanotopography as techniques such as colloidal and electron beam lithography and polymer demixing have become available. In this study, human fibroblast response to nanocolumns (160-nm high, 100-nm diameter, 230-nm centre-centre spacing) produced by colloidal lithography are considered. Using electron microscopy and immunofluorescence to image the cytoskeleton, clathrin and dynamin, it was observed that the cells try to endocytose the nanocolumns. It also appeared that a small population of the cells changed to unusual morphologies with macrophage-like processes and highly disrupted cytoskeleton. These observations could have implications for nanomaterials science in areas such as cell transfection and drug delivery.

Actins↗

PubMed2004

Investigating filopodia sensing using arrays of defined nano-pits down to 35 nm diameter in size.

In order for cells to react to topography, they must be able to sense shape. When considering nano-topography, these shapes are much smaller than the cell, but still strong responses to nano-topography have been seen. Filopodia, or microspikes, presented by cells at their leading edges are thought to be involved in gathering of special information. In order to investigate this, and to develop an understanding of what size of feature can be sensed by cells, morphological observation (electron and fluorescent microscopy) of fibroblasts reacting to nano-pits with 35, 75 and 120 nm diameters has been used in this study. The nano-pits are especially interesting because unlike many of the nanofeatures cited in the literature, they have no height for the cells to react to. The results showed that cell filopodia, and retraction fibres, interacted with all pit sizes, although direct interaction was hard to image on the 35 nm pits. This suggests that cells are extremely sensitive to their nanoevironment and that should be taken in to consideration when designing next-generation tissue engineering materials. We suggest that this may occur through nanocontact guidance as filopodia are moved over the pits.

Cells, Cultured↗

PubMed2004

Changes in fibroblast morphology in response to nano-columns produced by colloidal lithography.

In designing new biomaterials, specific chemical and topographical cues will be important in guiding cell response. Filopodia are actin-driven structures produced by cells and speculated to be involved in cell sensing of the three-dimensional environment. This report quantifies filopodia response to cylindrical nano-columns (100 nm diameter, 160 nm high) produced by colloidal lithography. Also observed were actin cytoskeleton morphology by fluorescence microscopy and filopodia morphology by electron microscopy (scanning and transmission). The results showed that the fibroblasts used produced more filopodia per microm of cell perimeter and that filopodia could often be seen to interact with the cells' nano-environment. By understanding as to which features evoke spatial reactions in cells, it may be possible to design better biomaterials.

Biocompatible Materials↗

PubMed2004

Use of nanotopography to study mechanotransduction in fibroblasts--methods and perspectives.

The environment around a cell during in vitro culture is unlikely to mimic those in vivo. Preliminary experiments with nanotopography have shown that nanoscale features can strongly influence cell morphology, adhesion, proliferation and gene regulation, but the mechanisms mediating this cell response remain unclear. In this perspective article, we attempt to illustrate that a possible mechanism is direct transmittal of forces encountered by cells during spreading to the nucleus via the cytoskeleton. We further try to illustrate that this 'self-induced' mechanotransduction may alter gene expression by changing interphase chromosome positioning. Whilst the observations described here to show how we think nanotopography can be developed as a tool to look at mechanotransduction are preliminary, we feel they indicate that topography may give cell biologists a non-invasive tool with which to investigate in vitro cellular mechanisms.

Animals↗

PubMed2003

Nucleus alignment and cell signaling in fibroblasts: response to a micro-grooved topography.

Cellular response to scaffold materials is of great importance in cellular and tissue engineering, and it is perhaps the initial cell contact with the scaffold that determines development of new tissue. Material surface morphology has strong effects on cell cytoskeleton and morphology, and it is thought that cells may react to the topography of collagen and surrounding cells during tissue embryology. A poorly understood area is, however, gene-level responses to topography. Thus, this paper used microarray to probe for consistent gene changes in response to lithographically produced topography (12.5 x 2-microm grooves) with time. The results showed many initial gene changes and also down-regulation of gene response with time. Cell and nucleus morphology were also considered, with nuclear deformation linked to cell signaling.

Cell Adhesion↗

PubMed2002

Increasing fibroblast response to materials using nanotopography: morphological and genetic measurements of cell response to 13-nm-high polymer demixed islands.

It is becoming clear that cells can respond not only to micometric scale topography, but may also to nanometric scale topography. The production of reproducibly sized nanometric features has relied heavily on expensive and time-consuming methods of manufacture, such as electron beam lithography. Polymer demixing of polystyrene and polybromostyrene has been found to produce nanoscale islands of reproducible height, and the islands have been previously shown to effect cell spreading compared to planar surfaces. This study observes morphological, cytoskeletal, and molecular changes in fibroblast reaction to 13-nm-high islands. The methods employed include scanning electron microscopy, fluorescent microscopy, and 1718 gene microarray. The results show that the cells respond to the islands by broad gene up-regulation, notably in the areas of cell signaling, proliferation, cytoskeleton, and production of extracellular matrix proteins. Microscopical results provide confirmation of the microarray findings.

Biocompatible Materials↗

PubMed2002

Fibroblast signaling events in response to nanotopography: a gene array study.

When considering the complicated nature of cell/tissue interactions with biomaterials, especially materials with nanometric surface features, observation of changes in one or two selected genes or proteins may not be sufficient. To get a fuller understanding of the scope of responses effected by nanotopography on cells, many genes need to be surveyed. Recent developments in molecular biology have lead to the commercial production of microarrays. Microarray presents a powerful tool by which many genes (up to many thousands) can be probed simultaneously. In this study, 1718 gene arrays have been used to measure human fibroblast response to 13-nm-high polymer demixed islands. The results have shown many changes in genes involved in signaling, cytoskeleton, extracellular matrix, gene transcription, and protein translation; these results have been used to build a more complete overview of fibroblast response to the islands. The use of microarray has expanded the range of observations possible using established microscopical and biochemical techniques.

Cell Culture Techniques↗

PubMed2002

Interactions of human blood and tissue cell types with 95-nm-high nanotopography.

Two of the major concerns for tissue engineering materials are inflammatory responses from blood cells and fibrous encapsulation by the body in order to shield the implant from blood reaction. A further hurdle is that of vascularization. In order to develop new tissues, or to repair parts of the vascular system, nutrients need to be carried to the basal cell layers. If a material promotes tissue formation, but not vascularization, necrosis will be observed as multilayered cells develop. In this paper, polymer demixed island topography with a 95-nm Z axis was tested using human mononuclear blood cells, platelets, fibroblasts, and endothelial cells. The results showed no difference in blood response between the islands and the flat controls, suggesting that in vivo there would be negligible immunological difference. Fibroblasts reacted by changing morphology into a rounded shape with thick processes and poorly developed cytoskeleton. Retardation of fibroblast growth may be an advantageous, as it is this cell type that forms the fibrous capsule, preventing growth of the required tissue type. Finally, endothelial cells were seen to form arcuate, or curved, morphologies in response to the islands. This is the normal, in vivo, morphology for vascular endothelium. This result suggests that the nano-features are promoting a more phenotypically correct morphology.

Cell Culture Techniques↗