Biomedical subjects

David K Mills

Publications and source records attributed to David K Mills.

7 recordsLinked to original sources

PubMed2006

Stem cell attachment to layer-by-layer assembled TiO2 nanoparticle thin films.

Surface topography is one of the most important factors influencing the attachment and spreading of cells. In the present study, layer-by-layer assembled titanium dioxide (TiO2) nanoparticle thin films were chosen for attachment, proliferation and spreading studies on mouse mesenchymal stem cells (MSC). Increasing surface roughness was observed with increasing number of layer-by-layer assembled TiO2 thin films. Four layer TiO2 thin film showed higher number of attached cells than a one layer thin film and control surfaces. MSCs experienced no cytotoxic effects after culture on the TiO2 coated substrates as observed from the cytotoxicity tests. Cell spreading, visualized with scanning electron microscopy, showed a faster rate of spreading on a rougher surface. Cells on a four-layer substrate, at 12 h showed complete spreading, where as most of the cells on a control surface and a one-layer surface, at 24 h, retained a rounded morphology. In conclusion, TiO2 nanoparticle thin films were successfully assembled in alternation with polyelectrolytes and in-vitro studies with MSC showed an increase in the attachment and faster spreading of cells on rougher surfaces.

Cell Adhesion↗

PubMed2005

Influence of channel width on alignment of smooth muscle cells by high-aspect-ratio microfabricated elastomeric cell culture scaffolds.

Engineered smooth muscle tissue requires ordered configurations of cells to reproduce native function, and microtechnology offers possibilities for physically and chemically controlling cell organization with high spatial resolution. In this work, poly(dimethylsiloxane) microchannel scaffolds, modified by layer-by-layer self-assembly of polyelectrolytes to promote cell adhesion, were evaluated for use as substrates for the culture of aligned smooth muscle cells. The hypothesis that narrower channels would result in better alignment was tested using channel width dimensions of 20, 30, 40, 50, and 60 microm, in addition to flat (control) surfaces. Alignment of cells was assessed by two different methods, each sensitive to a different aspect of cell alignment from fluorescence micrographs. Two-dimensional fast Fourier transform analysis was performed to analyze the orientation distribution of actin filaments in cells. This was complemented by connectivity analysis of stained nuclei to obtain nuclear orientation distributions. Both methods produced consistent data that support the hypothesis that narrow microchannels promote a highly aligned culture of smooth muscle cells, and the degree of alignment is dependent on the microchannel width. Precise replication of in vivo cell alignment in engineered tissue, with the ability to tailor specific surface chemistries of the scaffold to the desired application, will potentially allow the production of artificial tissue that more closely duplicates the structure and function of native tissue.

Actins↗

PubMed2005

Cellular response to gelatin- and fibronectin-coated multilayer polyelectrolyte nanofilms.

Surface engineering is a critical effort in defining substrates for cell culture and tissue engineering. In this context, multilayer self-assembly is an attractive method for creating novel composites with specialized chemical and physical properties that is currently drawing attention for potential application in this area. In this work, effects of thickness, surface roughness, and surface material of multilayer polymer nanofilms on the growth of rat aortic smooth muscle cells were studied. Polyelectrolyte multilayers (PEMs) electrostatically constructed from poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) (PSS) with gelatin, fibronectin, and PSS surface coatings were evaluated for interactions with smooth muscle cells (SMCs) in an in vitro environment. The results prove that PEMs terminated with cell-adhesive proteins promote the attachment and further growth of SMCs, and that this property is dependent upon the number of layers in the underlying multilayer film architecture. Cell roundness and number of pseudopodia were also influenced by the number of layers in the nanofilms. These findings are significant in that they demonstrate that both surface coatings and underlying architecture of nanofilms affect the morphology and growth of SMCs, which means additional degrees of freedom are available for design of biomaterials. This work supports the excellent potential of nanoassembled ultrathin films for biosurface engineering, and points to a novel perspective for controlling cell-material interaction that can lead to an elegant system for defining the extracellular in vitro environment.

Animals↗

PubMed2005

Layer-by-Layer assembly of TiO2 nanoparticles for stable hydrophilic biocompatible coatings.

Stable, super-hydrophilic (water contact angle approximately equal to 0 degrees) titanium dioxide nanoparticle thin films have been obtained on substrates with different initial wettability such as glass, poly(methyl methacrylate) and poly(dimethyl siloxane) using layer-by-layer nano-assembly method. Titanium dioxide nanoparticles were alternated with poly(styrene sulfonate) to form films of thickness ranging from 11 nm to 220 nm. The hydrophilicity of these thin films increases with increasing number of deposited PSS/TiO2 bilayers. It was found that 2, 5 and 20 layers were needed to form super-hydrophilic TiO2 coating on glass, PMMA and PDMS respectively. Oxygen plasma treatment of substrate surfaces enhanced the formation of homogeneous TiO2 films and accelerated the formation of hydrophilic layers. Super-hydrophilicity has been shown to be unique to PSS/TiO2 films as compared with other polyelectrolyte/nanoparticle layers, and UV irradiation may restore hydrophilicity even after months of storing of the samples. Biocompatibility of TiO2 nanoparticle films has been demonstrated by the successful cell culture of human dermal fibroblast.

Biocompatible Materials↗

PubMed2003

Biocompatibility of layer-by-layer self-assembled nanofilm on silicone rubber for neurons.

Electrostatic layer-by-layer (LbL) self-assembly, a novel method for ultrathin film coating has been applied to silicone rubber to encourage nerve cell adhesion. The surfaces studied consisted of precursor layers, with alternating cationic poly(ethyleneimine) (PEI) and anionic sodium poly(styrenesulfonate) (PSS) followed by alternating laminin and poly-D-lysine (PDL) layers or fibronectin and PDL layers. Film growth increased linearly with the number of layers. Every fibronectin/PDL and laminin/PDL bilayer was 4.4 and 3.5 nm thick, respectively. All layers were more hydrophilic than the unmodified silicone rubber surface, as determined from contact angle measurements. Of the coatings studied, a PDL layer was the most hydrophilic. A multilayer film with composition [PSS/PEI]3+[fibronectin/PDL]4 or [PSS/PEI]3+[laminin/PDL]4 was highly favorable for neuron adhesion, in contrast to bare silicone rubber substrate. The film coated on silicone rubber is biocompatible for cerebellar neurons with active viability, as shown by lactate dehydrogenase (LDH) assay and fluorescence cellular metabolism observations. These results demonstrate that LbL self-assembly provides an effective approach to apply films with nanometer thickness to silicone rubber. Such only few nanometer thick films are biocompatible with neurons, and may be used to coat devises for long-term implant in the central nervous system.

Animals↗

PubMed2003

Coating and selective deposition of nanofilm on silicone rubber for cell adhesion and growth.

A recently developed method for surface modification, layer-by-layer (LbL) assembly, has been applied to silicone, and its ability to encourage endothelial cell growth and control cell growth patterns has been examined. The surfaces studied consisted of a precursor, with alternating cationic polyethyleneimine (PEI) and anionic sodium polystyrene sulfonate (PSS) layers followed by alternating gelatin and poly-D-lysine (PDL) layers. Film growth increased linearly with the number of layers. Each PSS/PEI bilayer was 3 nm thick, and each gelatin/PDL bilayer was 5 nm thick. All layers were more hydrophilic than the unmodified silicone rubber surface, as determined from contact angle measurements. The contact angle was primarily dictated by the outermost layer. Of the coatings studied, gelatin was the most hydrophilic. A film of (PSS/PEI)4/(gelatin/PDL)4/ gelatin was highly favorable for cell adhesion and growth, in contrast to films of (PSS/PEI)8 or (PSS/PEI)8/PSS. Cell growth patterns were successfully controlled by selective deposition of microspheres on silicone rubber, using microcontact printing with a silicone stamp. Cell adhesion was confined to the region of microsphere deposition. These results demonstrate that the LbL self-assembly technique provides a general approach to coat and selectively deposit films with nanometer thickness on silicone rubber. Furthermore, they show that this method is a viable technique for controlling cellular adhesion and growth.

Animals↗

PubMed2002

Gelatin-glutaraldehyde cross-linking on silicone rubber to increase endothelial cell adhesion and growth.

Silicone is a biomaterial that is widely used in many areas because of its high optical clarity, its durability, and the ease with which it can be cast. However, these advantages are counterbalanced by strong hydrophobicity. Gelatin cross-linking has been used as a hydrophilic coating on many biomaterials but not on silicone rubber. In this study, two gelatin glutaraldehyde (GA) cross-linking methods were used to coat a hydrophilic membrane on silicone rubber. In method I, gelatin and GA were mixed in three different proportions (64:1, 128:1, and 256:1) before coating. In method II, a newly formed 5% gelatin membrane was cross-linked with a 2.5% GA solution. All coatings were hydrophilic, as determined from the measurement of contact angle for a drop of water on the surface. Bovine coronary arterial endothelial cells were shown to grow well on the surface modified by method II at 72 h. In method I, the cells grew well for gelatin-GA proportions of 64:1 and 128:1 at 72 h. No cell attachment on untreated silicone rubber was observed by the third d of seeding. The results indicated that both methods of gelatin-GA cross-linking provided a hydrophilic surface on silicone for endothelial cell adhesion and growth in vitro.

Animals↗