Nanometer Surface Features Research Articles

Nanoparticle deposition from nanofluid droplets during Leidenfrost phenomenon and consequent rise in transition temperature

Termination of film boiling at an elevated Leidenfrost temperature can have important implications in applications which require rapid cooling. Here we report the Leidenfrost phenomenon of nanofluid (nano-TiO2 dispersed in water) droplets exposed to a substrate heated to 300 °C and evaporation lifetime of water droplets dispensed over a copper substrate heated to 300 °C as a benchmark for comparison. Unlike water or sparsely dispersed nanofluid droplets, the abundantly dispersed nanofluid droplets exhibit deposition and boiling at 300 °C accompanied by violent agitation and fragmentation followed by continuous ejection of small droplets. As a result, the Leidenfrost phenomenon ceases to occur and the droplet evaporation lifetime is reduced by an order of magnitude in comparison to water. We anticipate that the vapor generated beneath the droplet for a higher concentration of nanoparticles is unable to levitate the droplet (mass) as deposition of a nano-particles generating a random pattern on the hot substrate disrupts the Leidenfrost state. We confirm the evidence of nanostructured porous coating from microscopy and topography analysis which reveals micro-pits and protuberances as high as several micrometers formed by clustered nanoparticles. In the presence of such random nanometric surface features, the interplay between the capillary pressure and vapor pressure dictates the existence of Leidenfrost condition. At a substrate temperature of 300 °C, the capillary pressure dominates the vapor pressure for the highly concentrated nanofluid droplets thereby, causing deposition of nanoparticles and ejection of small droplets. However, the same droplets exhibit levitation over the vapor layer when the substrate temperature is 400 °C. Thus, we conclude that the rise in Leidenfrost temperature for nanofluid droplets is governed by the concentration of dispersed nanoparticles, whose deposition generates a unique porous structure on the substrate and causes capillary wicking.

Effects of atomic geometry and electronic structure of platinum surfaces on molecular adsorbates studied by gap-mode SERS.

Surface enhanced Raman scattering (SERS) spectra of organic monolayers were measured on various types of polycrystalline and single crystalline Pt substrates with nanometric or atomic surface features, including heteroepitaxial Pt monolayers, using sphere-plane type nanogap structures. Although atomic geometry and electronic structures of a metal surface significantly influence metal-molecule interactions, such effects are often hindered in conventional SERS measured on a roughened surface because of the spectral information averaging at various adsorption sites. In this study, the use of atomically defined Pt surfaces revealed detailed surface effects; the observed preferential adsorption geometry on each surface was well explained by atomic surface arrangements. The peak shift of the intramolecular vibration in the anchor group was in good agreement with the variation of the d-band center of Pt substrates. Moreover, in electrochemical SERS study the Stark shift of an extramolecular vibrational mode at around 400 cm(-1), which is not accessible in infrared absorption spectroscopy, was monitored on an atomically defined heteroepitaxial Pt monolayer electrode.

SERS Study of Molecular Adsorbates on Catalytic Metal Surfaces with Various Atomic Arrangements

Surface enhanced Raman scattering (SERS) spectroscopy is normally conducted at a roughened surface of coinage metals. Although the nanometric surface roughness is needed for the signal enhancement, the use of the roughness often prevents deeper understanding of metal-molecule interactions at a specific surface site. Moreover, very limited surface enhancement is available on platinum group metals (PGMs) because of their localized d-electrons. In the field of electrocatalysis, it is essentially important to study molecular adsorbates on an atomically defined catalytic metal surface under electrochemical conditions. Therefore, these disadvantages limit application of SERS technique despite the potential of this technique for in-situ observation. Recently, there are several reports on SERS observations on single crystalline metal surfaces including non-SERS-active PGMs, in which the signal enhancement is induced by using sphere-plane type nanogap structures.1-6 In the present work, we observe SERS spectra of arylisocyanides adsorbed on catalytic metal substrates of various surface features at nanometric and atomic scale. Single crystal beads of gold, platinum, and palladium were obtained using the Clavilier method. The (111) facets of these beads were utilized for SERS observation. Pd-modified Au(111) was electrochemically prepared using the underpotential deposition (UPD). Pt-modified Au(111) was obtained by galvanic replacement of Cu-UPD monolayers on Au(111) with Pt2+ions. As a model Raman scatterer, 4-chlorophenylisocyanide (CPI) was utilized to form self-assembled monolayers (SAMs) on these metal surfaces. SERS measurements were conducted using a home-built Raman microscope with a 632.8-nm He-Ne laser light source after Au nanoparticles (Au-NPs) were physisorbed on top of the SAMs. Electrochemically roughened metal surfaces were also utilized for conventional SERS measurements. Figure 1 shows AFM images of electrochemically roughened polycrystalline Pt, mirror finished polycrystalline Pt, and single crystalline Pt(111) facet. One can see that the height of the surface features is around several 10 nm for the roughened Pt, a few nm for the smooth Pt, and monoatomic height for Pt(111). Among these surfaces, SERS effect is available only on the roughened Pt in the conventional method. Figure 2 shows conventional SERS spectrum measured on the roughened Pt and gap-mode SERS spectrum on smooth Pt. These spectra were very similar except for the signal intensity, indicating that the nanometric surface features do not affect molecular adsorption geometry. In addition, the chemical contribution of the adsorbed Au-NPs to the molecules is also negligible in the present case. On the other hand, the atomic surface feature significantly affected the molecular adsorption. As shown in Fig. 3, gap-mode SERS spectrum on Pt(111) was very different from that on the smooth polycrystalline Pt, suggesting three-hold hollow configuration. Moreover, when the Pt lattice was expanded by the monolayer formation on Au(111), the preferential configuration was changed to atop. We will also present SERS observations on other crystal orientations, the controbution of step-terrace structures, and electrochemical behavior of the adsorbates on these surfaces.

Reducing Infections Using Nanotechnology

ABSTRACTVentilator associated pneumonia (VAP) is a serious and costly clinical problem. Specifically, receiving mechanical ventilation for over 24 hours increases the risk of VAP and is associated with high morbidity, mortality and medical costs. Cost effective endotracheal tubes (ETTs) that are resistant to bacterial infection could help prevent this problem. The objective of this study was to determine differences in the growth ofStaphylococcus aureus(S. aureus) on nanomodified and unmodified polyvinyl chloride (PVC) ETTs under dynamic airway conditions. PVC ETTs were modified to have nanometer surface features by soaking them inRhizopus arrhisus,a fungal lipase. Twenty-four hour experiments (supported by computational models) showed that air flow conditions within the ETT influenced both the location and concentration of bacterial growth on the ETTs especially within areas of tube curvature. More importantly, experiments revealed a 1.5 log reduction in the total number ofS. aureuson the novel nanomodified ETTs compared to the conventional ETTs after 24 hours of air flow. This dynamic study showed that lipase etching can create nano-rough surface features on PVC ETTs that suppressS. aureusgrowth and, thus, may provide clinicians with an effective and inexpensive tool to combat VAP.

Decreased Staphylococcus aureus biofilm formation on nanomodified endotracheal tubes: a dynamic airway model

Ventilator-associated pneumonia (VAP) is a serious and costly clinical problem. Specifically, receiving mechanical ventilation for over 24 hours increases the risk of VAP and is associated with high morbidity, mortality, and medical costs. Cost-effective endotracheal tubes (ETTs) that are resistant to bacterial infections could help prevent this problem. The objective of this study was to determine differences in the growth of Staphylococcus aureus on nanomodified and unmodified polyvinyl chloride (PVC) ETTs under dynamic airway conditions simulating a ventilated patient. PVC ETTs were modified to have nanometer surface features by soaking them in Rhizopus arrhisus, a fungal lipase. Twenty-four-hour experiments (supported by computational models) showed that airflow conditions within the ETT influenced both the location and the concentration of bacterial growth on the ETTs, especially within areas of tube curvature. More importantly, experiments revealed a 1.5 log reduction in the total number of S. aureus on the novel nanomodified ETTs compared with the conventional ETTs after 24 hours of airflow. This dynamic study showed that lipase etching can create nanorough surface features on PVC ETTs that suppress S. aureus growth, and thus may provide clinicians with an effective and inexpensive tool to combat VAP.

Nanomodified Endotracheal Tubes: Spatial Analysis of Reduced Bacterial Colonization in a Bench Top Airway Model

ABSTRACTVentilator associated pneumonia (VAP) is a serious and costly clinical problem. Specifically, receiving mechanical ventilation for over 24 hours increases the risk of VAP and is associated with high morbidity, mortality and medical costs. Cost effective endotracheal tubes (ETTs) that are resistant to bacterial infection could help prevent this problem. The objective of this study was to determine differences in the growth ofStaphylococcus aureus(S. aureus) on nanomodified and unmodified polyvinyl chloride (PVC) ETTs under dynamic airway conditions. PVC ETTs were modified to have nanometer surface features by soaking them inRhizopus arrhisus,a fungal lipase. Twenty-four hour experiments (supported by computational models) showed that air flow conditions within the ETT influenced both the location and concentration of bacterial growth on the ETTs especially within areas of tube curvature. More importantly, experiments revealed a 1.5 log reduction in the total number ofS. aureuson the novel nanomodified ETTs compared to the conventional ETTs after 24 hours of air flow. This dynamic study showed that lipase etching can create nano-rough surface features on PVC ETTs that suppressS. aureusgrowth and, thus, may provide clinicians with an effective and inexpensive tool to combat VAP.

Effects of PLGA Nano Patterns on the Responses of Healthy Osteoblasts

ABSTRACTPoly(lactic-co-glycolic acid) (PLGA) films with flat surfaces and with 27nm, 190nm, 300nm, 400nm, and 520nm surface features were synthesized using a template method with polydimethylsiloxane (PDMS) molds. The nano patterns were transferred from the self-assembled polystyrene beads to the PLGA films through PDMS molds. After synthesis, the nano patterns were confirmed by AFM height scans. In order to investigate the influence of the materials on bone cells, healthy human osteoblasts were cultured on the PLGA films. The 27nm PLGA surface showed the maximum osteoblast adhesion density and a significant increase compared with the other surface features. For these reasons, and since previous studies have highlighted that similar nanometer surface features on PLGA decreased functions of other cancer cells, this study suggests that PLGA with 27nm surface features should be further studied for bone cancer applications where healthy bone cell functions need to be promoted and cancerous bone cell functions inhibited.

Decreased lung carcinoma cell functions on select polymer nanometer surface features

Biomaterial nanotopographies have been proposed as a means to significantly influence cell functions (including osteoblasts, fibroblasts, endothelial cells, chondrocytes, immune cells, and bacteria). In this study, lung epithelial carcinoma cell functions including adhesion (up to 4 h), proliferation (up to 3 days), apoptosis (up to 5 days), and vascular endothelial growth factor (VEGF) synthesis (up to 5 days) on poly-lactic-co-glycolic (PLGA) films with various nanotopographies were systematically investigated. Importantly, this study created PLGA films with various nanotopographies (specifically, nano-smooth, 23, 300, and 400 nm hemispherical surface features) but similar surface chemistry in order to focus only on the effect of PLGA topography on cancer cell functions. Simple and effective cast-molding and solvent evaporation methods were used to accomplish this. Atomic force microscopy, electron spectroscopy for chemical analysis, and water contact angle measurements verified similar surface chemistry and energy but varied topographies for all of the PLGA films prepared in this study. Lung epithelial carcinoma cell adhesion, proliferation, and morphology results indicated less cell growth and spreading on nano-smooth and 400 nm surface-featured PLGA compared to any other samples. However, results also demonstrated decreased lung epithelial carcinoma cell VEGF (a key growth factor secreted for the vascularization of tumors) synthesis on the 23 nm surface-featured PLGA compared to the nano-smooth substrates for up to 5 days. In summary, these results provided the first insights into understanding the role that PLGA nanotography may play in mediating lung carcinoma cell functions for a wide range of applications in regenerative medicine.

Understanding osteoblast responses to stiff nanotopographies through experiments and computational simulations

An increasing number of studies have demonstrated the positive role nanotopographies can have toward promoting various cell functions. However, the relevant mechanism(s) behind this improvement in biological interactions at the cell-material interface is not well understood. For this reason, here, osteoblast (bone forming cell) functions (including adhesion, proliferation, and differentiation) on two carefully-fabricated diamond films with dramatically-different topographies were tested and modeled. The results over all the time periods tested revealed greater cell responses on nanocrystalline diamond (NCD, grain sizes <100 nm) compared to submicron crystalline diamond (SMCD, grain sizes 200-1000 nm). To understand this positive impact of cell responses per stiff nanotopographies, cell filopodia extension and cell spreading were studied through computational simulations and the results suggested that increasing the lateral dimensions or height of nanometer surface features could inhibit cell filopodia extension and, ultimately, decrease cell spreading. The computational simulation results were further verified by live cell imaging (LCI) experiments. This study, thus, describes a possible new approach to investigate (through experiments and computational simulation) the mechanisms behind nanotopography-enhanced cell functions.

On the role of RhoA/ROCK signaling in contact guidance of bone-forming cells on anisotropic Ti6Al4V surfaces

Patterned surfaces direct cell spatial dynamics, yielding cells oriented along the surface geometry, in a process known as contact guidance. The Rho family of GTPases controls the assembly of focal adhesions and cytoskeleton dynamics, but its role in modulating bone-cell alignment on patterned surfaces remains unknown. This article describes the interactions of two human cell types involved in osseointegration, specifically mesenchymal stem cells and osteoblasts, with submicron- or nano-scale Ti6Al4V grooved surfaces generated by mechanical abrasion. The surface chemistry of the alloy was not affected by grinding, ensuring that the differences found in cellular responses were exclusively due to changes in topography. Patterned surfaces supported cell growth and stimulated mesenchymal stem cell viability. Anisotropic surfaces promoted cell orientation and elongation along the grates. Both cell types oriented on nanometric surfaces with grooves of 150nm depth and 2μm width. The number of aligned cells increased by approximately 30% on submicrometric grooves with sizes of about 1μm depth and 10μm width. Cells were treated with drugs that attenuate the activities of the GTPase RhoA and one of its downstream effectors, Rho-associated kinase (ROCK), and contact guidance of treated cells on the grooved surfaces was investigated. The data indicate that the RhoA/ROCK pathway is a key modulator of both mesenchymal stem cell and osteoblast orientation on nanometric surface features. RhoA and its effector participate in the alignment of mesenchymal stem cells on submicrometric grooves, but not of osteoblasts. These findings show that RhoA/ROCK signaling is involved in contact guidance of bone-related cells on metallic substrates, although to a varying extent depending on the specific cell type and the dimensions of the pattern.

The influence of nanoscale topographical cues on initial osteoblast morphology and migration

The natural environment of a living cell is not only organized on a micrometer, but also on a nanometer scale. Mimicking such a nanoscale topography in implantable biomaterials is critical to guide cellular behavior. Also, a correct positioning of cells on biomaterials is supposed to be very important for promoting wound healing and tissue regeneration. The exact mechanism by which nanotextures can control cellular behavior are thus far not well understood and it is thus far unknown how cells recognize and respond to certain surface patterns, whereas a directed response appears to be absent on other pattern types. Focal adhesions (FAs) are known to be involved in the process of specific pattern recognition and subsequent response by cells. In this study, we used a high throughput screening "Biochip" containing 40 different nanopatterns to evaluate the influence of several nanotopographical cues like depth, width, (an)isotropy and spacing (ridge-groove ratio) on osteoblast behavior. Microscopical analysis and time lapse imaging revealed that an isotropic topography did not alter cell morphology, but it highly induced cell motility. Cells cultured on anisotropic topographies on the other hand, were highly elongated and aligned. Time-lapse imaging revealed that cell motility is highly dependent on the ridge-groove ratio of anisotropic patterns. The highest motility was observed on grooves with a ratio of 1:3, whereas the lowest motility was observed on ratios of 1:1 and 3:1. FA measurements demonstrated that FA-length decreased with increasing motility. From the study it can be concluded that osteoblast behavior is tightly controlled by nanometer surface features.

Greater endothelial cell responses on submicron and nanometer rough titanium surfaces

An in vitro competitive coculture system was designed in this study to investigate vascular cell functions on submicron (lateral feature sizes larger than 100 nm) and nanometer (lateral and vertical feature sizes smaller than 50 nm) rough titanium surface features created via e-beam evaporation with identical chemistry to that of control (unmodified) titanium. Rat aortic endothelial cells (RAEC) and rat aortic smooth muscle cells (RASMC) were individually cultured and cocultured on such substrates for 4 h as well as 1, 3, and 5 days. In addition, RAEC and RASMC intracellular collagen and elastin synthesis were determined for up to 14 days on the various substrates. Compared to control flat titanium surfaces, the results showed for the first time that submicron rough surface features on titanium enhanced RAEC proliferation (followed by nanometer surface features), while simultaneously inhibiting RASMC proliferation. In addition, protein synthesis assays demonstrated enhanced collagen and elastin production by RAEC cultured on submicron rough titanium substrates (followed by nano rough) compared to control flat titanium substrates. Surface characterization results showed that submicron rough featured titanium possessed the greatest hydrophilicity (followed by nanometer surface featured), which may have promoted select protein adsorption to increase RAEC over RASMC function. In contrast to RASMC, RAEC morphology was significantly altered by the underlying titanium surface features, which may also explain the altered vascular cell functions on the different substrates. Thus, this study suggested that submicron to nanometer rough surface features should be further studied for improving titanium for vascular stent applications.

Decreased lung carcinoma cell density on select polymer nanometer surface features for lung replacement therapies

Poly(lactic-co-glycolic) acid (PLGA) has been widely used as a biomaterial in regenerative medicine because of its biocompatibility and biodegradability properties. Previous studies have shown that cells (such as bladder smooth muscle cells, chondrocytes, and osteoblasts) respond differently to nanostructured PLGA surfaces compared with nanosmooth surfaces. The purpose of the present in vitro research was to prepare PLGA films with various nanometer surface features and determine whether lung cancer epithelial cells respond differently to such topographies. To create nanosurface features on PLGA, different sized (190 nm, 300 nm, 400 nm, and 530 nm diameter) polystyrene beads were used to cast polydimethylsiloxane (PDMS) molds which were used as templates to create nanofeatured PLGA films. Atomic force microscopy (AFM) images and root mean square roughness (RMS) values indicated that the intended spherical surface nanotopographies on PLGA with RMS values of 2.23, 5.03, 5.42, and 36.90 nm were formed by employing 190, 300, 400, and 530 nm beads. A solution evaporation method was also utilized to modify PLGA surface features by using 8 wt% (to obtain an AFM RMS value of 0.62 nm) and 4 wt% (to obtain an AFM RMS value of 2.23 nm) PLGA in chloroform solutions. Most importantly, lung cancer epithelial cells adhered less on the PLGA surfaces with RMS values of 0.62, 2.23, and 5.42 nm after four hours of culture compared with any other PLGA surface created here. After three days, PLGA surfaces with an RMS value of 0.62 nm had much lower cell density than any other sample. In this manner, PLGA with specific nanometer surface features may inhibit lung cancer cell density which may provide an important biomaterial for the treatment of lung cancer (from drug delivery to regenerative medicine).

The effect of biphasic electrical stimulation on osteoblast function at anodized nanotubular titanium surfaces

Over the past decade, nanotechnology (or the use of materials with dimensions less than 100 nm in at least one direction) has been proposed to improve the lifespan of many biomedical devices, including orthopedic implants. Specifically, to improve the cytocompatibility properties of currently used orthopedic implants, nanotechnology has been used to create nanometer surface features (through anodization) on titanium. In addition to this approach, another therapeutic method widely investigated to heal bone fractures is through electrical stimulation. Here, the coupling of such nanotechnology approaches and electrical stimulation were studied to maximize bone cell functions on titanium. Results showed that compared to unstimulated conventional titanium, bone forming cell (osteoblast) proliferation and long-term functions (alkaline phosphatase synthesis, collagen type I synthesis and calcium deposition) were improved upon both the creation of an anodized nanotubular titanium surface and biphasic electrical stimulation. Most importantly, when electrical stimulation was combined with anodized nanotubular titanium features, osteoblast long-term functions were improved the most. Therefore, coupling the positive effects of anodized nanotubular titanium topographies with currently used therapeutic electrical stimulation should be further studied to improve orthopedic implants.

Nanotextured titanium surfaces for enhancing skin growth on transcutaneous osseointegrated devices

A major problem with transcutaneous osseointegrated implants is infection, mainly due to improper closure of the implant–skin interface. Therefore, the design of transcutaneous osseointegrated devices that better promote skin growth around these exit sites needs to be examined and, if successful, would clearly limit infection. Due to the success already demonstrated for orthopedic implants, developing surfaces with biologically inspired nanometer features is a design criterion that needs to be investigated for transcutaneous devices. This study therefore examined the influence of nanotextured titanium (Ti) created through electron beam evaporation and anodization on keratinocyte (skin-forming cell) function. Electron beam evaporation created Ti surfaces with nanometer features while anodization created Ti surfaces with nanotubes. Conventional Ti surfaces were largely micron rough, with few nanometer surface features. Results revealed increased keratinocyte adhesion in addition to increased keratinocyte spreading and differences in keratinocyte filopodia extension on the nanotextured Ti surfaces prepared by either electron beam evaporation or anodization compared to their conventional, unmodified counterparts after 4 h. Results further revealed increased keratinocyte proliferation and cell spreading over 3 and 5 days only on the nanorough Ti surfaces prepared by electron beam evaporation compared to both the anodized nanotubular and unmodified Ti surfaces. Therefore, the results from this in vitro study provided the first evidence that nano-modification techniques should be further researched as a means to possibly improve skin growth, thereby improving transcutaneous osseointegrated orthopedic implant longevity.

Nanoscale Electron Beam Damage Studied by Atomic Force Microscopy

High-resoln. SEM (HRSEM) has recently been added to the arsenal of characterization tools for material scientists to observe nanoscale surface features on both conducting and insulating materials. It is now therefore crucial to understand whether the intense electron beam will damage the features of interest. The authors were able, for the 1st time, to measure and quantify this damage using a combination of HRSEM and at. force microscopy (AFM), and as a consequence, the bulk of the damage, expressed as a depression on the crystal surface, is confined primarily to a subsurface vol. Simulations demonstrate that the depth of the depression is proportional to the interaction vol. of impact electrons below the crystal surface. More importantly, the nanometer surface features are conserved, and there is negligible assocd. loss of the crit. information in nanoscopic surface topog. These results confirm the usefulness of HRSEM as a tool for surface anal. not only for scientists studying crystal growth but also for materials scientists analyzing any surface at the nanoscale.

Two-Photon Polymerization for Fabricating Structures Containing the Biopolymer Chitosan

Two-photon polymerization is a powerful tool for fabricating three-dimensional micro/nano structures for applications ranging from nanophotonics to biology. To tailor such structure for specific purposes it is often important to dope them. In this paper we report on the fabrication of structures, with nanometric surface features (resolution of approximately 700 nm), using two-photon polymerization of an acrylic resin doped with the biocompatible polymer chitosan using a guest-host scheme. The fluorescence background in the Raman spectrum indicates the presence of chitosan throughout the structure. Mechanical characterization reveals that chitosan does not affect the mechanical properties of the host acrylic resin and, consequently, the structures exhibit excellent integrity. The approach presented in this work can be used in the fabrication of micro- and nanostructures containing biopolymers for biomedical applications.

The role of polymer nanosurface roughness and submicron pores in improving bladderurothelial cell density and inhibiting calcium oxalate stone formation

Synthetic polymers have been proposed for replacing resected cancerous bladder tissue.However, conventional (or nanosmooth) polymers used in such applications (such aspoly(ether) urethane (PU) and poly-lactic-co-glycolic acid (PLGA)) often fail clinically dueto poor bladder tissue regeneration, low cytocompatibility properties, and excessive calciumstone formation. For the successful reconstruction of bladder tissue, polymer surfacesshould be modified to combat these common problems. Along these lines, implementingnanoscale surface features that mimic the natural roughness of bladder tissue on polymersurfaces can promote appropriate cell growth, accelerate bladder tissue regeneration andinhibit bladder calcium stone formation. To test this hypothesis, in this study,the cytocompatibility properties of both a non-biodegradable polymer (PU) anda biodegradable polymer (PLGA) were investigated after etching in chemicals(HNO3 and NaOH, respectively) to create nanoscale surface features. After chemical etching, PUpossessed submicron sized pores and numerous nanometer surface features while PLGApossessed few pores and large amounts of nanometer surface roughness. Results from thisstudy strongly supported the assertion that nanometer scale surface roughness produced onPU and PLGA promoted the density of urothelial cells (cells that line the interior of thebladder), with the greatest urothelial cell densities observed on nanorough PLGA. Inaddition, compared to respective conventional polymers, the results providedevidence that nanorough PU and PLGA inhibited calcium oxalate stone formation;submicron pored nanorough PU inhibited calcium oxalate stone formation themost. Thus, results from the present study suggest the importance of nanometertopographical cues for designing better materials for bladder tissue engineeringapplications.

Reduced responses of macrophages on nanometer surface features of altered alumina crystalline phases

Extensive prolonged interactions of inflammatory cells (such as macrophages) at the host–implant interface may lead to implant failure. While previous studies have shown increased in vitro and in vivo bone cell adhesion, proliferation and mineralization on nanophase compared to currently implanted ceramics, few studies have been conducted to elucidate inflammatory cell responses on such nanophase ceramics. Controlling surface feature size and corresponding surface roughness on implants may clearly alter immune cell responses, which would be an extremely important consideration for the use of nanostructured materials as improved biomaterials. In this study, reduced macrophage density was observed on alumina (Al 2O 3) compacts with greater nanometer surface roughness accompanied by changes in crystallinity for up to 24 h in culture. Since alumina is a commonly used ceramic in orthopedic applications, this in vitro study continues to support the use of nanophase ceramics as improved orthopedic implants by demonstrating reduced macrophage responses.

Decreased lung carcinoma cell density on select polymer nanometer surface features for lung replacement therapies

AbstractPLGA (poly-lactic-co-glycolic acid) has been widely used as a biomaterial in regenerative medicine due to its biocompatibility and biodegradability properties. Previous studies have shown that cells (such as bladder smooth muscle cells, chondrocytes, osteoblasts, and vascular smooth muscle cells) respond differently to nano-structured PLGA surfaces (such as those with surface features less than 100 nm in at least one dimension) compared to nano-smooth surfaces. The purpose of the present in vitro research was to prepare PLGA films with various nanometer surface features and determine, for the first time, whether lung cancer epithelial cells respond differently to such topographies. Poly(dimethylsiloxane) (PDMS) molds prepared by placing PDMS onto various polystyrene monolayers and two solution evaporation methods were used to create nanometer surface features on PLGA. The intended spherical surface nano-topographies on PLGA with RMS values of 2.23, 5.03, 5.42 and 36.90 nm were formed, while PLGA surfaces with RMS values of 0.62 and 2.23 nm were obtained by different solution evaporation methods. Most importantly, lung cancer epithelial cells adhered less on the PLGA surfaces with an RMS value of 0.62, 2.23 and 5.42 nm after 4 hours of culture compared to any other PLGA surface created here. After three days, PLGA surfaces with an RMS value of 0.62 nm had much lower cell density than any other sample. In this manner, PLGA with specific nanometer surface features may inhibit lung cancer cell density which may provide for an important biomaterial for the treatment of lung cancer for a wide range of applications (from drug delivery to regenerative medicine).