The effect of silica nanoparticulate coatings on cellular response

Nanoparticle-Cell Interaction: A Cell Mechanics Perspective

Progress in the field of nanoparticles has enabled the rapid development of multiple products and technologies; however, some nanoparticles can pose both a threat to the environment and human health. To enable their safe implementation, a comprehensive knowledge of nanoparticles and their biological interactions is needed. In vitro and in vivo toxicity tests have been considered the gold standard to evaluate nanoparticle safety, but it is becoming necessary to understand the impact of nanosystems on cell mechanics. Here, the interaction between particles and cells, from the point of view of cell mechanics (i.e., bionanomechanics), is highlighted and put in perspective. Specifically, the ability of intracellular and extracellular nanoparticles to impair cell adhesion, cytoskeletal organization, stiffness, and migration are discussed. Furthermore, the development of cutting-edge, nanotechnology-driven tools based on the use of particles allowing the determination of cell mechanics is emphasized. These include traction force microscopy, colloidal probe atomic force microscopy, optical tweezers, magnetic manipulation, and particle tracking microrheology.

The Interplay between Surface Nanotopography and Chemistry Modulates Collagen I and III Deposition by Human Dermal Fibroblasts

The events within the foreign body response are similar to, but ultimately different than, the wound healing cascade. Collagen production by fibroblasts is known to play a vital role in wound healing and device fibrous encapsulation. However, the influence of surface nanotopography on collagen deposition by these cells has not been reported so far. To address this gap, we have developed model substrata having surface nanotopography of controlled height of 16, 38, and 68 nm and tailored outermost surface chemistry of amines, carboxyl acid, and pure hydrocarbon. Fibroblast adhesion was reduced on nanotopographically modified surfaces compared to the smooth control. Furthermore, amine and acid functionalized surfaces showed increased cell proliferation over hydrophobic hydrocarbon surfaces. Collagen III production increased from day 3 to day 8 and then decreased from day 8 to day 16 on all surfaces, while collagen I deposition increased throughout the duration of 16 days. Our data show that the initial collagen I and III deposition can be modulated by selecting desired combinations of surface nanotopography and chemistry. This study provides useful knowledge that could help in tuning fibrous capsule formation and in turn govern the fate of implantable biomaterial devices.

Cell Growth on ("Janus") Density Gradients of Bifunctional Zeolite L Crystals

Nanoparticle density gradients on surfaces have attracted interest as two-dimensional material surfaces that can mimic the complex nano-/microstructure of the native extracellular matrix, including its chemical and physical gradients, and can therefore be used to systematically study cell-material interactions. In this respect, we report the preparation of density gradients made of bifunctional zeolite L crystals on glass surfaces and the effects of the density gradient and biopolymer functionalization of zeolite L crystals on cell adhesion. We also describe how we created "Janus" density gradient surfaces by gradually depositing two different types of zeolite L crystals that were functionalized and loaded with different chemical groups and guest molecules onto the two distinct sides of the same glass substrate. Our results show that more cells adhered on the density gradient of biopolymer-coated zeolites than on uncoated ones. The number of adhered cells increased up to a certain surface coverage of the glass by the zeolite L crystals, but then it decreased beyond the zeolite density at which a higher surface coverage decreased fibroblast cell adhesion and spreading. Additionally, cell experiments showed that cells gradually internalized the guest-molecule-loaded zeolite L crystals from the underlying density gradient containing bifunctional zeolite L crystals.

Fibrinogen adsorption and platelet adhesion to silica surfaces with stochastic nanotopography

In this study, the effect of surface nanoscale roughness on fibrinogen adsorption and platelet adhesion was investigated. Nanorough silica surfaces with a low level of surface roughness (10 nm Rrms) were found to support the same level of fibrinogen adsorption as the planar silica surfaces, while nanorough silica surfaces with higher levels of surface roughness (15 nm Rrms) were found to support significantly less fibrinogen adsorption. All surfaces analyzed were found to support the same level of platelet adhesion; however, platelets were rounded in morphology on the nanorough silica surfaces while platelets were spread with a well-developed actin cytoskeleton on the planar silica. Unique quartz crystal microbalance with dissipation monitoring (QCM-D) responses was observed for the interactions between platelets and each of the surfaces. The QCM-D data indicated that platelets were more weakly attached to the nanorough silica surfaces compared with the planar silica. These data support the role of surface nanotopography in directing platelet-surface interactions even when the adsorbed fibrinogen layer is able to support the same level of platelet adhesion.

Addition of nanoscaled bioinspired surface features: A revolution for bone related implants and scaffolds?

Our expanding ability to handle the "literally invisible" building blocks of our world has started to provoke a seismic shift on the technology, environment and health sectors of our society. During the last two decades, it has become increasingly evident that the "nano-sized" subunits composing many materials—living, natural and synthetic—are becoming more and more accessible for predefined manipulations at the nanosize scale. The use of equally nanoscale sized or functionalised tools may, therefore, grant us unprecedented prospects to achieve many therapeutic aims. In the past decade it became clear that nano-scale surface topography significantly influences cell behaviour and may, potentially, be utilised as a powerful tool to enhance the bioactivity and/ or integration of implanted devices. In this review, we briefly outline the state of the art and some of the current approaches and concepts for the future utilisation of nanotechnology to create biomimetic implantable medical devices and scaffolds for in vivo and in vitro tissue engineering,with a focus on bone. Based on current knowledge it must be concluded that not the materials and surfaces themselves but the systematic biological evaluation of these new material concepts represent the bottleneck for new biomedical product development based on nanotechnological principles.

Engineering a biocompatible scaffold with either micrometre or nanometre scale surface topography for promoting protein adsorption and cellular response

Surface topographical features on biomaterials, both at the submicrometre and nanometre scales, are known to influence the physicochemical interactions between biological processes involving proteins and cells. The nanometre-structured surface features tend to resemble the extracellular matrix, the natural environment in which cells live, communicate, and work together. It is believed that by engineering a well-defined nanometre scale surface topography, it should be possible to induce appropriate surface signals that can be used to manipulate cell function in a similar manner to the extracellular matrix. Therefore, there is a need to investigate, understand, and ultimately have the ability to produce tailor-made nanometre scale surface topographies with suitable surface chemistry to promote favourable biological interactions similar to those of the extracellular matrix. Recent advances in nanoscience and nanotechnology have produced many new nanomaterials and numerous manufacturing techniques that have the potential to significantly improve several fields such as biological sensing, cell culture technology, surgical implants, and medical devices. For these fields to progress, there is a definite need to develop a detailed understanding of the interaction between biological systems and fabricated surface structures at both the micrometre and nanometre scales.

The nanosilica hazard: another variable entity

Silica nanoparticles (SNPs) are produced on an industrial scale and are an addition to a growing number of commercial products. SNPs also have great potential for a variety of diagnostic and therapeutic applications in medicine. Contrary to the well-studied crystalline micron-sized silica, relatively little information exists on the toxicity of its amorphous and nano-size forms. Because nanoparticles possess novel properties, kinetics and unusual bioactivity, their potential biological effects may differ greatly from those of micron-size bulk materials. In this review, we summarize the physico-chemical properties of the different nano-sized silica materials that can affect their interaction with biological systems, with a specific emphasis on inhalation exposure. We discuss recent in vitro and in vivo investigations into the toxicity of nanosilica, both crystalline and amorphous. Most of the in vitro studies of SNPs report results of cellular uptake, size- and dose-dependent cytotoxicity, increased reactive oxygen species levels and pro-inflammatory stimulation. Evidence from a limited number of in vivo studies demonstrates largely reversible lung inflammation, granuloma formation and focal emphysema, with no progressive lung fibrosis. Clearly, more research with standardized materials is needed to enable comparison of experimental data for the different forms of nanosilicas and to establish which physico-chemical properties are responsible for the observed toxicity of SNPs.

Electrophoretic deposition of biomaterials

Electrophoretic deposition (EPD) is attracting increasing attention as an effective technique for the processing of biomaterials, specifically bioactive coatings and biomedical nanostructures. The well-known advantages of EPD for the production of a wide range of microstructures and nanostructures as well as unique and complex material combinations are being exploited, starting from well-dispersed suspensions of biomaterials in particulate form (microsized and nanoscale particles, nanotubes, nanoplatelets). EPD of biological entities such as enzymes, bacteria and cells is also being investigated. The review presents a comprehensive summary and discussion of relevant recent work on EPD describing the specific application of the technique in the processing of several biomaterials, focusing on (i) conventional bioactive (inorganic) coatings, e.g. hydroxyapatite or bioactive glass coatings on orthopaedic implants, and (ii) biomedical nanostructures, including biopolymer-ceramic nanocomposites, carbon nanotube coatings, tissue engineering scaffolds, deposition of proteins and other biological entities for sensors and advanced functional coatings. It is the intention to inform the reader on how EPD has become an important tool in advanced biomaterials processing, as a convenient alternative to conventional methods, and to present the potential of the technique to manipulate and control the deposition of a range of nanomaterials of interest in the biomedical and biotechnology fields.

Friction transfer of polytetrafluoroethylene (PTFE) to produce nanoscale features and influence cellular response in vitro

A large number of cell types are known to respond to chemical and topographical patterning of substrates. Friction transfer of polytetrafluoroethylene (PTFE) onto substrates has been shown to produce continuous, straight, parallel nanofibres. Ammonia plasma treatment can be used to defluorinate the PTFE, decreasing the dynamic contact angle. Fibroblast and epithelial cells were elongated and oriented with their long axis parallel to the fibres, both individually and in clusters. The fibres restricted cell migration. Cell alignment was slightly reduced on the plasma-treated fibres. These results indicated that although surface topography can affect cellular response, surface chemistry also mediates the extent of this response.

Free Bioverit ® II Implants Coated with a Nanoporous Silica Layer in a Mouse Ear Model — A Histological Study

The objective of this study is to evaluate the suitability of a mouse middle ear model for testing ossicular replacement materials. Twenty-four BALB/c mice are implanted with the bioglass-ceramic Bioverit® II which is coated with a silica-nanostructure or with plain Bioverit® II as a control. After 2, 6, and 12 weeks, 4 mice per group are sacrificed and both complete petrous bones are analyzed histologically. All implants revealed in situ an incipient growth of thin connective tissue layers over the surface, followed by a spreading of epithelial cells. The osseogenic response which is increasing with time is more intense in the coated Bioverit ® II specimens. The absence of inflammatory cells suggests an excellent biocompatibility of the silica nano structure. As the results are comparable to a study with the same materials in rabbits, the mouse model described is highly suitable for evaluation of new ossicular replacement materials. Additionally, by gene expression analysis a more detailed insight into cellular interactions of the middle ear is offered.

A comparison of different nanostructured biomaterials in subcutaneous tissue

The nanostructured surface of a material can improve its interaction with cells and its acceptance as an implant. We compared two novel biomaterials with different nanostructures: Bioverit II with a coating of nanoporous silica and chitosan-hydroxyapatite composite materials. Pure Bioverit II served as a control. Platelets of these materials were implanted for 28, 85 and 300 days in the subcutaneous tissue in the neck of 38 rabbits. After excising the specimens they were fixed, embedded in epoxy resin and analyzed histologically. All coated Bioverit II implants showed a thin capsule of connective tissue. After 300 days, these capsules tended to be thicker than in pure Bioverit II. No signs of inflammation were observed and the materials appeared unaltered by visual inspection. In case of chitosan-hydroxyapatite composites, massive capsules consisting of dense connective tissue were found, and the material showed signs of biodegradation in form of fissures and cavities. In conclusion, the nanoporous coating showed no obvious positive effect with regard to capsule formation; the chitosan-hydroxyapatite implants provoked a stronger interaction between cells and material. However, most Bioverit II implants showed no alterations optically, whereas chitosan-hydroxyapatite was partly degraded in all cases.

Histological evaluation of novel ossicular chain replacement prostheses: an animal study in rabbits

CONCLUSION

The improved biocompatibility of Bioverit II coated with a nanostructured surface shows promising qualities for use in human reconstructive middle ear surgery. In the case of chitosan-hydroxyapatite composite prostheses, further investigations regarding composition of the material, degree of purity and design are necessary before clinical application.

OBJECTIVE

The selection of optimal materials for reconstructive middle ear surgery continues to be a problem. In the present study novel materials were tested as total ossicular replacement prostheses (TORPs) in an animal model.

MATERIALS AND METHODS

Bioverit II coated with a nanostructured surface and chitosan-hydroxyapatite composites were placed in the middle ear of 40 rabbits. Uncoated Bioverit II was used as control. After an implantation period of 28, 84 or 300 days petrous bones were extracted, embedded in epoxy resin and examined by light microscopy.

RESULTS

Uncoated and coated Bioverit prostheses revealed a mucosal coverage and a little osseogenic response after 28 days. The results of the coated Bioverit prostheses slightly surpassed those of the plain prostheses. Chitosan-hydroxyapatite composite prostheses were mostly found to be dislocated after 28 days. Formations of granulation tissue and fibrotic capsules were observed around these implants. This reaction could be caused by the instability of the composite material or may be due to impurities present in the chitosan.

Protein and cell micropatterning and its integration with micro/nanoparticles assembly

Micropatterning of proteins and cells has become very popular over the past decade due to its importance in the development of biosensors, microarrays, tissue engineering and cellular studies. This article reviews the techniques developed for protein and cell micropatterning and its biomedical applications. The prospect of integrating micro and nanoparticles with protein and cell micropatterning is discussed. The micro/nanoparticles are assembled into patterns and form the substrate for proteins and cell attachment. The assembled particles create a micro or nanotopography, depending on the size of the particles employed. The nonplanar structure can increase the surface area for biomolecules attachment and therefore enhance the sensitivity for detection in biosensors. Furthermore, a nanostructured substrate can influence the conformation and functionality of protein attached to it, while cellular response in terms of morphology, adhesion, proliferation, differentiation, etc. can be affected by a surface expressing micro or nanoscale structures. Proteins and cells tend to lose their normal functions upon attachment to substrate. By recognizing the types of topography that are favourable for preserving proteins and cell behaviour, and integrating it with micropattering will lead to the development of functional protein and cell patterns.

The effect of silica nanoparticulate coatings on serum protein adsorption and cellular response

Serum protein adsorption on colloidal silica surfaces was investigated using a quartz crystal microbalance with dissipation (QCM-D) monitoring. The amount of serum proteins adsorbed on colloidal silica-coated surfaces was not significantly different from the control silica surfaces, with the exception of 21nm colloidal silica which experienced significantly less (P<0.05) fibrinogen adsorption compared with control silica. The adhesion and proliferation of human endothelial cells (C11STH) on nano-scale colloidal silica surfaces were significantly reduced compared with control silica surfaces, suggesting that the conformation of adsorbed proteins on the colloidal silica surfaces plays a role in modulating the amount of cell binding. Fibronectin is one of the main extracellular matrix proteins involved in endothelial cell attachment to biomaterial surfaces. There was reduced binding of a monoclonal anti-fibronectin antibody, that reacted specifically with the cell-binding fragment, to fibronectin-coated colloidal silica surfaces compared with control silica surfaces. This suggests that the fibronectin adsorbed on the colloidal silica-coated surfaces was conformationally changed compared with control silica reducing the availability of the cell-binding domain of fibronectin.