Optimizing HAPEX topography influences osteoblast response

Regulation of cell locomotion by nanosecond-laser-induced hydroxyapatite patterning

Hydroxyapatite, an essential mineral in human bones composed mainly of calcium and phosphorus, is widely used to coat bone graft and implant surfaces for enhanced biocompatibility and bone formation. For a strong implant-bone bond, the bone-forming cells must not only adhere to the implant surface but also move to the surface requiring bone formation. However, strong adhesion tends to inhibit cell migration on the surface of hydroxyapatite. Herein, a cell migration highway pattern that can promote cell migration was prepared using a nanosecond laser on hydroxyapatite coating. The developed surface promoted bone-forming cell movement compared with the unpatterned hydroxyapatite surface, and the cell adhesion and movement speed could be controlled by adjusting the pattern width. Live-cell microscopy, cell tracking, and serum protein analysis revealed the fundamental principle of this phenomenon. These findings are applicable to hydroxyapatite-coated biomaterials and can be implemented easily by laser patterning without complicated processes. The cell migration highway can promote and control cell movement while maintaining the existing advantages of hydroxyapatite coatings. Furthermore, it can be applied to the surface treatment of not only implant materials directly bonded to bone but also various implanted biomaterials implanted that require cell movement control.

Evaluation of Preosteoblast MC3T3-E1 Cells Cultured on a Microporous Titanium Membrane Fabricated Using a Precise Mechanical Punching Process

The surface topography of Titanium (Ti) combined toughness and biocompatibility affects the attachment and migration of cells. Limited information of morphological characteristics, formed by precise machining in micron order, is currently available on the Ti that could promote osteoconduction. In the present study, a pure Ti membrane was pierced with precise 25 μm square holes at 75 μm intervals and appear burrs at the edge of aperture. We defined the surface without burrs as the “Head side” and that with burrs as the “Tail side”. The effects of the machining microtopography on the proliferation and differentiation of the preosteoblasts (MC3T3-E1 cells) were investigated. The cells were more likely to migrate to, and accumulate in, the aperture of holes on the head side, but grew uniformly regardless of holes on the tail side. The topography on the both surfaces increased osteopontin gene expression levels. Osteocalcin expression levels were higher on the head side than one on the blank scaffold and tail side (p < 0.05). The osteocalcin protein expression levels were higher on the tail side than on the head side after 21 days of cultivation, and were comparable to the proportion of the calcified area (p < 0.05). These results demonstrate the capacity of a novel microporous Ti membrane fabricated using a precise mechanical punching process to promote cell proliferation and activity.

Biocompatibility of polyamide 12 intramedullary rod after humeral consolidation in white Plymouth Rock birds

ABSTRACT: Technological and tissue engineering have enabled available, biologically inert, and low cost materials to be considered as viable alternatives in the surgical treatment of long bone fractures in birds. The aim of this study was to microscopically analyse osteotomized humerus of birds following the insertion of solid laser-sintered polyamide 12 rods in order to detect foreign body reaction and, thus, verify the bioinert property of the material in the bone fracture environment. Polyamide 12 intramedullary rods were inserted into the osteotomized humerus of 10 birds (white Plymouth Rock) and blocked using 2mm diameter cortical screws of varying lengths. The birds were operated at 60 days of age and monitored post-operatively for three months. Animals were euthanized at 150 days old and samples of the operated humerus collected for immunohistochemistry, light and scanning electron microscopy analysis. Results show bone consolidation without rejection of the implant and absence of inflammatory cells. Vascular Endothelial Growth Factor (VEGF) was expressed in the endothelial cells of the blood vessels at the site of the newly formed bone surrounding the implant, indicative of local angiogenesis. There was no bone growth on the surface of the rod; however, the implant did not interfere with the circumjacent bone repair. Thus, the findings of this study corroborate with the literature in characterizing polyamide as a bioinert material and, under the studied conditions, it can be concluded that polyamide 12 intramedullary rod is biocompatible and provides adequate bone consolidation in humeral fractures with no signs of rejection.

Advances in small joint arthroplasty of the hand

Substantial effort has been directed at the development of small joint prostheses for the hand. Despite advances in prosthetic joint design, outcomes have been relatively unchanged over the past 60 years. Pain relief and range of motion achieved after surgery have yet to mirror the success of large joint arthroplasty. Innovations in biotechnology and stem cell applications for damaged joint surfaces may someday make prostheses obsolete. The purpose of this review is to describe the current status, ongoing advances, and future of small joint arthroplasty of the hand.

Developments in stem cells: implications for future joint replacements

Will stem cell research reverse the projected sevenfold increase in primary and revision knee replacements expected in the United States between 2005 and 2030? A focus on prevention and treatment of osteoarthritis may end the need for primary joint replacements. A more likely scenario can be described as slow and incremental changes in the prevention and treatment of osteoarthritis, accompanied by the continuing development of implant technology. Since the discovery of stem cells in the 1950s, research has increased exponentially. Expanded autologous chondrocytes, and more recently ex vivo expanded skeletal stem cells, are currently injected into osteochondral defects in the hope of regenerating cartilage and halting progression towards osteoarthritis. In addition, mesenchymal stem cells are being injected into human joints as a treatment for osteoarthritis despite a lack of quantitative research. Concurrently, stem cell research continues to contribute to chemical and topographical advancements in implant design. Advances in co-culture techniques mean it is possible that biologic articular replacements will develop prior to the cessation of the need for arthroplasty and radically change the nature of joint replacements. Whether it is through implant design or a potential cure for the pain attributable to osteoarthritis, as we hope to show in this 'forward look article', it is our opinion that stem cells will certainly impact future joint replacement.

Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization

Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities.

Understanding the nano-topography changes and cellular influences resulting from the surface adsorption of human hair keratins

Recent interest in the use of human hair keratins as a biomaterial has grown, fuelled by improvements in keratin extraction methods and better understanding of keratin bioactivity. The use of keratins as a bioactive coating for in vitro cell culture studies is an attractive proposition. In this light, the surface adsorption of human hair keratins onto tissue culture polystyrene surfaces has been investigated. Keratin density, nano-topography and hydrophobicity of keratin coated surfaces were characterized. To understand the cellular influence of these coated surfaces, murine L929 fibroblasts were cultured on them and evaluated for cytotoxicity, proliferation, metabolic activity and detachment behaviors compared to collagen type 1 coated surfaces. Keratins were deposited up to a density of 650 ng/cm(2) when a coating concentration of 80 μg/ml or higher was used. The surface features formed by adsorbed keratins also changed in a coating concentration dependent manner. These surfaces improved L929 mouse fibroblast adhesion and proliferation in comparison to uncoated and collagen type 1 coated tissue culture polystyrene. Furthermore, the expression of fibronectin was accelerated on surfaces coated with solutions of higher keratin concentrations. These results suggest that human hair keratins can be used as a viable surface coating material to enhance substrate compliance for culturing cells.

The involvement of integrin β1 signaling in the migration and myofibroblastic differentiation of skin fibroblasts on anisotropic collagen-containing nanofibers

Utilization of nanofibrous matrices for skin wound repair holds great promise due to their morphological and dimensional similarity to native extracellular matrix (ECM). It becomes highly desired to understand how various nanofibrous matrices regulate skin cell behaviors and intracellular signaling pathways, important to tuning the functionality of tissue-engineered skin grafts and affecting the wound healing process. In this study, the phenotypic expressions of normal human dermal fibroblasts (NHDFs) on collagen-containing nanofibrous matrices with either isotropic (i.e., fibers collected randomly with no alignment) or anisotropic (i.e., fibers collected with alignment) fiber organizations were studied by immunostaining, migration assay and molecular analyses. Results showed that both nanofibrous matrices supported the attachment and growth of NHDFs similarly, while showing different cell morphology with distinct variation in focal adhesion formation and distribution. Anisotropic nanofibers significantly triggered the integrin β1 signaling pathway in NHDFs as evidenced by an increase of active integrin β1 (130 kD mature form) and phosphorylation of focal adhesion kinase (FAK) at Tyr-397. Anisotropic matrices also promoted the migration of NHDFs along the fibers, while neutralization of the integrin β1 activity abolished this promotion. Moreover, the fibroblast-to-myofibroblast differentiation was greatly enhanced for the NHDFs cultured on anisotropic nanofibrous matrices over a period of 48 h. Inhibition of cellular integrin β1 activity by neutralizing antibody eliminated this enhancement. These findings suggest the important role of integrin β1 signaling pathway in regulating the nanofiber-induced fibroblast phenotypic alteration and providing insightful understanding of the possible application of collagen-containing nanofibrous matrices for skin regeneration.

Starch and its Derived Products: Biotechnological and Biomedical Applications

Starches are one of the most abundant renewable natural resources available to us, however their potential as a biomass feedstock for the production of a vast range of commercially viable chemicals/components for application in many areas of industrial, food and biomedical sciences is currently under-exploited. This review begins by presenting an overview of starch sources, composition and structure, and physicochemical characteristics. Specific topics discussed include amylose and amylopectin structure, their location in the amorphous and crystalline regions of starch granules, granule morphology, gelatinisation and pasting characteristics. The remainder of the review then focuses upon the biotechnological production of starch hydrolysis products, such as maltodextrins, glucose and fructose syrups, and cyclodextrins, and the chemical modification of starch, namely, oxidation, stabilisation (esterification and etherification), and cross-linking. Finally some specific examples of the development of starch-derived biomaterials for application in areas such as orthopaedics, bone cements, tissue engineering, and hydrogels are presented.

Biocomposites and hybrid biomaterials based on calcium orthophosphates

The state-of-the-art of biocomposites and hybrid biomaterials based on calcium orthophosphates that are suitable for biomedical applications is presented in this review. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through successful combinations of the desired properties of matrix materials with those of fillers (in such systems, calcium orthophosphates might play either role), innovative bone graft biomaterials can be designed. Various types of biocomposites and hybrid biomaterials based on calcium orthophosphates, either those already in use or being investigated for biomedical applications, are extensively discussed. Many different formulations, in terms of the material constituents, fabrication technologies, structural and bioactive properties as well as both in vitro and in vivo characteristics, have already been proposed. Among the others, the nanostructurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using biocomposites and hybrid biomaterials based on calcium orthophosphates in the selected applications are highlighted. As the way from the laboratory to the hospital is a long one, and the prospective biomedical candidates have to meet many different necessities, this review also examines the critical issues and scientific challenges that require further research and development.

Bioactive ceramic-reinforced composites for bone augmentation

Biomaterials have been used to repair the human body for millennia, but it is only since the 1970s that man-made composites have been used. Hydroxyapatite (HA)-reinforced polyethylene (PE) is the first of the 'second-generation' biomaterials that have been developed to be bioactive rather than bioinert. The mechanical properties have been characterized using quasi-static, fatigue, creep and fracture toughness testing, and these studies have allowed optimization of the production method. The in vitro and in vivo biological properties have been investigated with a range of filler content and have shown that the presence of sufficient bioactive filler leads to a bioactive composite. Finally, the material has been applied clinically, initially in the orbital floor and later in the middle ear. From this initial combination of HA in PE other bioactive ceramic polymer composites have been developed.

Bioglass-derived glass-ceramic scaffolds: study of cell proliferation and scaffold degradation in vitro

Cell support function as well as cell proliferation on highly porous Bioglass(R)-derived glass-ceramic scaffolds (designed for bone tissue engineering) have been assessed in vitro using osteoblast-like cells (MG 63) cultured for up to 6 days. The biodegradation and mechanical stability of the scaffolds in the cell-culture medium have also been investigated. It was found that the scaffolds had excellent cell supporting ability, with cells effectively infiltrating into and surviving at the center of the scaffolds. A quantitative study using the AlamarBlue assay revealed that the proliferation of cells on the glass-ceramic materials was comparable to that on the noncrystallized Bioglass. While the crystalline phase in the glass-ceramic scaffolds transformed into a biodegradable amorphous calcium phosphate phase during cell culture, the mechanical strength of the scaffolds was maintained when compared with that of scaffolds incubated in simulated body fluid or immersed in cell-free culture medium. It is believed that the attached cells and collagen secreted by cells could fill the micropores and microcracks on the surface of the foam struts, thus contributing to the mechanical stability of the degrading scaffolds. In summary, the developed glass-ceramic scaffolds possess the most essential features of a scaffold for bone tissue engineering: they are capable to support and foster relevant cells, able to provide temporary mechanical function, and biodegradable.

Biological evaluation of partially stabilized zirconia added HA/HDPE composites with osteoblast and fibroblast cell lines

In the present study, the biocompatibility of partially stabilized zirconia (PSZ) added hydroxyapatite (HA)--high density polyethylene (HDPE) composites was evaluated by proliferation and cell attachment assays on two osteoblast cell lines (G-292, Saos-2) and a type of fibroblast cell isolated from bone tissue namely HBF in different time intervals. Cell-material interactions on the surface of the composites were observed by scanning electron microscopy (SEM). The effect of composites on the behavior of osteoblast and fibroblast cells was compared with those of HDPE and Tissue Culture Poly Styrene (TPS) (as negative control) samples. Results showed that the composite samples supported a higher proliferation rate of osteoblast cells in the presence of composite samples as compared to the HDPE and TPS samples after 3, 7 and 14 days of incubation period. It was showed that an equal or in some cases an even higher proliferation rate of G-292 and Saos-2 osteoblast cells on composite samples in compare to negative controls in culture period (P < 0.05). The number of adhered cells on the composite samples was equal and in some cases higher than the number adhered on the HDPE and TPS samples after the above mentioned incubation periods (P < 0.05). Adhered cells presented a normal morphology by SEM and many of the cells were seen to be undergoing cell division.

The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder

A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.

Fabrication of nanostructured hydroxyapatite and analysis of human osteoblastic cellular response

Nano-sized hydroxyapatite (HA) powders were produced by a hydrothermal method and a precipitation method. Spark plasma sintering (SPS) was used to fabricate nanostructured HA (NHA) using nano-sized HA powders as a precursor. Conventional sintering was employed to produce microstructured HA (MHA). Characteristics of HA powders and HA bulk ceramics after sintering were investigated by XRD, FTIR, SEM, TEM, particle size distribution, and AFM. Dense compacts consisting of equiaxed grains with an average grain size of approximately 100 nm were obtained by SPS. Human osteoblasts were cultured on both NHA and MHA and cell attachment, proliferation, and mineralization were evaluated. After 90 min incubation, the cell density on NHA surface was significantly higher than that of MHA and glass control, whereas average cell area of a spread cell was significantly lower on NHA surface compared to MHA and glass control after 4 h incubation. Matrix mineralization was determined after 7 and 14 days incubation by using alizarin red assay combined with cetylpyridinium chloride extraction. NHA shows significant enhancement (p < 0.05) in mineralization compared to MHA. Results from this study suggest that NHA may be a much better candidate for clinical use in terms of bioactivity.

In vitro osteoblastic response to 30 vol% hydroxyapatite-polyethylene composite

Hydroxyapatite-reinforced high-density polyethylene (HA-HDPE) composite, as a bone replacement material, has successfully been used clinically as middle ear prostheses and orbital floor implants. The aim of this study was to examine its in vitro biocompatibility in order to develop a further application, that is, as skull reconstruction implants. Human osteoblast cells isolated from femoral heads and crania were used to determine the biological response of the composites. HA-HDPE composites (30 vol %) with two grades of HA filler that had different surface morphologies were selected for this in vitro assessment. The results showed that HA-HDPE composite was bioactive and supported osteoblast attachment, proliferation, and differentiation. The composite with rough-surfaced HA filler demonstrated slightly better cellular response than the composite with smooth-surfaced HA filler. Although osteoblastic cells derived from skull showed an overall slower response compared with those from femoral heads, these in vitro results show that HA-HDPE composite potentially could be used as a skull implant.

Cell instructive polymers

Polymeric materials used in tissue engineering were initially used solely as delivery vehicles for transplanting cells. However, these materials are currently designed to actively regulate the resultant tissue structure and function. This control is achieved through spatial and temporal regulation of various cues (e.g., adhesion ligands, growth factors) provided to interacting cells from the material. These polymeric materials that control cell function and tissue formation are termed cell instructive polymers, and recent trends in their design are outlined in this chapter.

Characterization of nano hydroxyapatite/collagen surfaces and cellular behaviors

Osseointegration at the bone-implant interface is a prerequisite for endosseous implants to succeed in achieving and maintaining their long-term stability in bone tissue. The achievement of osseointegration is significantly affected by surface nature of implants. To optimize osseointegration, this study presents the characterization of synthesized nanocrystalline hydroxyapatite (nano HA) and in vitro studies on nano HA, nano-HA/collagen, and titanium surfaces. Voids were found within the grain of nano HA, which consisted of the shell and the core. The finding assists the clarification of microstructures of nano HA. By low-temperature mixing nano-HA sol with collagen gel (nano-HA/collagen 80:20), nano HA, and nano-HA/collagen coated on pure titanium or porous anodic titanium oxides resulted in higher wettability and lower roughness. The in vitro studies showed that porous structures produced by anodic oxides on titanium served as positive anchorage sites for cell filopodia to connect, and nano HA decreased cell attachment of osteoblasts and induced well-developed long filopodia and broad lamellipodia, thereby enhancing cellular motility. Collagen involvement enhanced cell adhesion to nano HA. Cell reactions to nano HA, nano-HA/collagen, native, and porous titanium surfaces provide some guidance for an optimal osseointegration by their application in surface modifications for implants.

The effect of partially stabilized zirconia on the biological properties of HA/HDPE composites in vitro

The effect of partially stabilized zirconia (PSZ) on the biological properties of the hyroxyapatite - high density polyethylene (HA/HDPE) composites was studied by investigating the simultaneous effect of hydroxyapatite and PSZ volume fractions on the in vitro response of human osteoblast cells. The biocompatibility of composite samples with different volume fraction of HA and PSZ powders was assessed by proliferation, alkaline phosphatase (ALP) and cell attachment assays on the osteoblast cell line (G-292) in different time periods. The effect of composites on the behavior of G-292 cells was compared with those of HDPE and TPS (Tissue Culture Poly Styrene as negative control) samples. Results showed a higher proliferation rate of G-292 cells in the presence of composite samples as compared to the HDPE sample after 7 and 14 days of incubation period. ALP production rate in all composite samples was higher than HDPE and TPS samples. The number of adhered cells on the composite samples was higher than the number adhered on the HDPE and TPS samples after the above mentioned incubation periods. These findings indicates that the addition of PSZ does not have any adverse affect on the biocompatibility of HA/HDPE composites. In fact in some experiments PSZ added HA/HDPE composites performed better in proliferation, differentiation and attachment of osteoblastic cells.

Characterization of human primary osteoblast response on bioactive glass (BaG 13–93)- coated poly-L,DL-lactide (SR-PLA70) surfacein vitro

Bioabsorbable polylactide-based polymers are commonly used for bone reconstruction. Although these polymers have proven successful in many applications, they do not have the capacity to induce osteoconduction. Therefore, several strategies have been developed to manufacture osteoconductive polylactide-based composites. In this study, we have investigated in vitro response of human primary osteoblasts for self-reinforced poly-L,DL-lactide 70/30 (SR-PLA70) plates coated with spheres of bioactive glass 13-93 (SR-PLA70 + BaG). Osteoblasts were cultured on SR-PLA70 and SR-PLA70 + BaG plates for 2, 7, or 14 days. By day 7, both materials induced a reduction in total cell population. However, by day 14 the proliferative response of osteoblasts on SR-PLA70 + BaG surface was such that the cell population had regained similar levels as that of day 2 controls. Alkaline phosphatase activity was higher on SR-PLA70 at day 7 but declined to control levels by day 14. There were no significant time-dependent variations in alkaline phosphatase activity on SR-PLA70 + BaG. After in vitro hydrolysis for 7 days, the elemental analysis of SR-PLA70 + BaG surface showed the presence of mineral precipitates that were confirmed as crystalline hydroxyapatite. This was accompanied by osteoblast spreading, protrusions of microvilli adhered to BaG 19-39 surface, cuboidal phenotype and cell surface associated formation of hydroxyapatite microspheres. In conclusion, the SR-PLA70 + BaG composite is capable of inducing a proliferative response of human primary osteoblasts, and appears to support the development of mature osteoblast phenotype. Therefore, the SR-PLA70 + BaG composites appear as promising osteoconductive scaffold candidates for reconstruction and regeneration of bone matrix.

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.

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.

Synthesis and characterisation of cationically modified phospholipid polymers

Phospholipid-like copolymers based on 2-(methacryloyloxyethyl) phosphorylcholine were synthesised using monomer-starved free radical polymerisation methods and incorporating cationic charge in the form of the choline methacrylate monomer in amounts varying from 0 to 30 wt%, together with a 5 wt% silyl cross-linking agent in order to render them water-insoluble once thermally cured. Characterisation using a variety of techniques including nuclear magnetic resonance spectroscopy, high-pressure liquid chromatography and gel permeation chromatography showed the cationic monomer did not interfere with the polymerisation and that the desired amount of charge had been incorporated. Gravimetric and differential scanning calorimetry methods were used to evaluate the water contents of polymer membranes cured at 70 degrees C, which was seen to increase with increasing cation content, producing materials with water contents ranging from 50% to 98%. Surface plasmon resonance indicated that the coatings swelled rapidly in water, the rate and extent of swelling increasing with increasing cation level. Dynamic contact angle showed that coatings of all the polymers possessed a hydrophobic surface when dry in air, characteristic of the alkyl chains expressed at the surface (>100 degrees advancing angle). Rearrangement of the hydrophilic groups to the surface occurred once wet, to produce highly wettable surfaces with a decrease in advancing angle with increasing cation content. Atomic force microscopy showed all polymer films to be smooth with no features in topographical or phase imaging. Mechanical properties of the dry films were also unaffected by the increase in cation content.

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.

The effects of collagen type I topography on myoblasts in vitro

Cells respond to a variety of cues from their environment, which can include chemical, mechanical, and topographical signals. The differentiation of myoblasts requires a combination of signals. Myoblast fusion is strongly influenced by the chemical nature of the surrounding matrix and can be affected by mechanical stimulation. Studies also have shown that a large variety of cell types also are influenced by details of surface topography of a substrate as small as 44 nm. Cells grown on a collagen-coated surface differentiate more readily than those grown in the absence of the extracellular matrix protein. It is not known whether the effects of myoblast interaction with collagen are due solely to chemical interactions or if myoblasts also respond to the topography of collagen type I fibers. To determine the importance of collagen-generated topographical signals on myoblast development, cells were cultured and differentiated in vitro on surfaces that had been coated with either soluble collagen type I or fibrous collagen type I. Both surfaces present the same chemical interactions, but the additional topographical signals lead to differences in cell morphology, adhesion, spreading rates and, proliferation. Cells on the fibrous form of collagen are more stellate, form more adhesion plaques, spread faster, and proliferate at a faster, rate than cells on a surface of soluble collagen. Our data indicate that topographical signals play a role in early muscle development, but that other or additional signaling pathways regulate differentiation.

Cell response to nano-islands produced by polymer demixing: a brief review

This review looks at the present literature available regarding cell response to nano-islands produced by nanotopography. Polymer demixing is a chemical method of fabricating large areas of nanotopography quickly and cheaply, making it ideal for cell testing and thus allowing it to be one of the first well-researched methods in cell engineering. The review shows that cells respond strongly to the islands (cell types observed include endothelial cells, fibroblasts, osteoblasts, leucocytes and platelets). Such changes include differences in adhesion, growth, gene expression and morphology.

Osteoblast attachment and mineralized nodule formation on rough and smooth 45S5 bioactive glass monoliths

Human primary osteoblast responses to smooth and roughened bioactive glass of 45S5 (Bioglass trade mark ) composition (46.1% SiO(2), 26.9% CaO, 2.6% P(2)O(5), 24.4% Na(2)O) were analysed in vitro. The smooth and rough surfaces had R(a) values and peak to valley distances of 0.04, 4.397, 2.027, and 21.328 microm, respectively. Cell attachment and morphology was observed using phalloidin staining of the actin cytoskeleton and revealed significant differences between smooth and rough surfaces. Cells that were spiky in appearance on the rough compared to the smooth surface formed an organized actin matrix much later on the rough surface. Scanning electron microscopy revealed many cell filipodia extending from more rounded cell bodies on the rough surface. A significantly greater number of nodules on the rough surface was observed, and these were shown to mineralize when supplemented with beta-glycerophosphate and dexamethasone. Raman spectroscopy confirmed the presence of hydroxyapatite in the mineralized cultures showing a definite peak at 964 cm(-1). FTIR analysis showed hydroxyapatite formation occurred more rapidly on the rough surface. This study demonstrates that although initial cell morphology was less advanced on the roughened surface, the cells were able to form mineralized nodules in greater numbers. This may have implications to bone tissue engineering using bioactive glasses.

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.