Reinforced Portland cement porous scaffolds for load-bearing bone tissue engineering applications

Modified Portland cement porous scaffolds with suitable characteristics for load-bearing bone tissue engineering applications were manufactured by combining the particulate leaching and foaming methods. Non-crosslinked polydimethylsiloxane was evaluated as a potential reinforcing material. The scaffolds presented average porosities between 70 and 80% with mean pore sizes ranging from 300 μm up to 5.0 mm. Non-reinforced scaffolds presented compressive strengths and elastic modulus values of 2.6 and 245 MPa, respectively, whereas reinforced scaffolds exhibited 4.2 and 443 MPa, respectively, an increase of ∼62 and 80%. Portland cement scaffolds supported human osteoblast-like cell adhesion, spreading, and propagation (t = 1-28 days). Cell metabolism and alkaline phosphatase activity were found to be enhanced at longer culture intervals (t ≥ 14 days). These results suggest the possibility of obtaining strong and biocompatible scaffolds for bone repair applications from inexpensive, yet technologically advanced materials such as Portland cement.

Isotropic micropatterned silica coatings on zirconia induce guided cell growth for dental implants

Titanium implants are the gold standard in dentistry; however, problems such as gingival tarnishing and peri-implantitis have been reported. For zirconia to become a competitive alternative dental implant material, surface modification techniques that induce guided tissue growth must be developed.

OBJECTIVES

To develop alternative surface modification techniques to promote guided tissue regeneration on zirconia materials, for applications in dental implantology.

METHODS

A methodology that combined soft lithography and sol-gel chemistry was used to obtain isotropic micropatterned silica coatings on yttria-stabilized zirconia substrates. The materials were characterized via chemical, structural, surface morphology approaches. In vitro biological behavior was evaluated in terms of early adhesion and viability/metabolic activity of human osteoblast-like cells. Statistical analysis was conducted using one-way ANOVA/Tukey HSD post hoc test.

RESULTS

Isotropic micropatterned silica coatings on yttria-stabilized zirconia substrates were obtained using a combined approach based on sol-gel technology and soft lithography. Micropatterned silica surfaces exhibited a biocompatible behavior, and modulated cell responses (i.e. inducing early alignment of osteoblast-like cells). After 7d of culture, the cells fully covered the top surfaces of pillar microstructured silica films.

SIGNIFICANCE

The micropatterned silica films on zirconia showed a biocompatible response, and were capable of inducing guided osteoblastic cell adhesion, spreading and propagation. The results herein presented suggest that surface-modified ceramic implants via soft lithography and sol-gel chemistry could potentially be used to guide periodontal tissue regeneration, thus promoting tight tissue apposition, and avoiding gingival retraction and peri-implantitis.

Early spreading and propagation of human bone marrow stem cells on isotropic and anisotropic topographies of silica thin films produced via microstamping

While there has been rapid development of microfabrication techniques to produce high-resolution surface modifications on a variety of materials in the last decade, there is still a strong need to produce novel alternatives to induce guided tissue regeneration on dental implants. High-resolution microscopy provides qualitative and quantitative techniques to study cellular guidance in the first stages of cell-material interactions. The purposes of this work were (1) to produce and characterize the surface topography of isotropic and anisotropic microfabricated silica thin films obtained by sol-gel processing, and (2) to compare the in vitro biological behavior of human bone marrow stem cells on these surfaces at early stages of adhesion and propagation. The results confirmed that a microstamping technique can be used to produce isotropic and anisotropic micropatterned silica coatings. Atomic force microscopy analysis was an adequate methodology to study in the same specimen the sintering derived contraction of the microfabricated coatings, using images obtained before and after thermal cycle. Hard micropatterned coatings induced a modulation in the early and late adhesion stages of cell-material and cell-cell interactions in a geometry-dependent manner (i.e., isotropic versus anisotropic), as it was clearly determined, using scanning electron and fluorescence microscopies.

Versatile methods for the fabrication of polyvinylidene fluoride microstructures

Polyvinylidene fluoride (PVDF) microstructures are of interest for a number of BioMEMS applications both for their piezoelectric and biocompatible properties. In this work, simple soft lithography-based techniques were developed to fabricate PVDF microstructures with diverse geometries, including microarrays of pillars, lines, and wells. Four different microstructure configurations were created: freestanding, stamped discontinuous, stamped continuous and imprinted patterns. Features with lateral dimensions down to 1 μm were consistently reproduced on 2.5 cm diameter areas. Atomic force microscopy (AFM) measurements of poled PVDF microstructures confirmed a marked inverse piezoelectric behavior. The techniques presented here have a number of advantages over previously demonstrated PVDF micropatterning approaches.

Vacuum-assisted cell seeding in a microwell cell culture system

We present a simple method to actively pattern individual cells and groups of cells in a polymer-based microdevice using vacuum-assisted cell seeding. Soft lithography is used to mold polymer microwells with various geometries on top of commercially available porous membranes. Cell suspensions are placed in a vacuum filtration setup to pull culture medium through the microdevice, trapping the cells in the microwells. The process is evaluated by determining the number of cells per microwell for a given cell seeding density and microwell geometry. This method is tested with adherent and nonadherent cells (NIH 3T3 fibroblasts, PANC-1 pancreatic ductal epithelial-like cells, and THP-1 monocytic leukemia cells). These devices could find applications in high-throughput cell screening, cell transport studies, guided formation of cell clusters, and tissue engineering.

High throughput assembly of spatially controlled 3D cell clusters on a micro/nanoplatform

Guided assembly of microscale tissue subunits (i.e. 3D cell clusters/aggregates) has found applications in cell therapy/tissue engineering, cell and developmental biology, and drug discovery. As cluster size and geometry are known to influence cellular responses, the ability to spatially control cluster formation in a high throughput manner could be advantageous for many biomedical applications. In this work, a micro- and nanofabricated platform was developed for this purpose, consisting of a soft-lithographically fabricated array of through-thickness microwells structurally bonded to a sheet of electrospun fibers. The microwells and fibers were manufactured from several polymers of biomedical interest. Human hepatocytes were used as model cells to demonstrate the ability of the platform to allow controlled cluster formation. In addition, the ability of the device to support studies on semi-controlled heterotypic interactions was demonstrated by co-culturing hepatocytes and fibroblasts. Preliminary experiments with other cells of interest (pancreatic cells, embryonic stem cells, and cardiomyocytes) were also conducted. Our platform possesses several advantages over previously developed microwell arrays: a more in vivo-like topographical stimulation of cells; better nutrient/waste exchange through the underlying nanofiber mat; and easy integration into standard two-chamber cell culture well systems.