Cell Adhesion Studies Research Articles

Contactless Laser-Assisted Patterning of Surfaces for Bio-Adhesive Microarrays

Micropatterned surfaces with cell adhesive areas, delimited by protein repellent microstructures, are in high demand for its potential use as relevant biological assays. This is not only because such surfaces allow directing cell growth in a spatially localized and restricted manner, but also because they can be used to elucidate basic cell growth and orientation mechanisms. Here, it is presented a laser-assisted micropatterning technique to fabricate large area microstructures of poly (ethylene glycol) hydrogel onto a cell adhesive surface: a biofunctional maleic anhydride copolymer. By varying photoinitiator, laser intensity, copolymer as well as the hydrogel layer thickness, the optimum conditions to produce high quality features were found. The suitability of these micropatterned substrates for bioassay applications was proved by cell adhesion studies. The introduced procedure could be used to prepare a broad range of microarrays for certain bioanalytical approaches and to create different types of biofunctional surfaces.

Abstract 276: Tissue Engineering a Small Diameter Vascular Graft

Introduction The patency rate of synthetic small diameter grafts for coronary and peripheral arterial bypass remains poor. The aim of this study was to engineer an acellular, biocompatible conduit with biomechanical properties similar to native artery and investigate the regenerative capacity of the conduit using ovine vascular cells. Methods Porcine carotid arteries were harvested and decellularized using an established protocol. In short, arteries were treated sequentially with EDTA, hypotonic buffer, 0.1% (w/v) sodium dodecyl sulphate (SDS), DNase and RNase, hypertonic buffer and sterilised using 0.1% (v/v) peracetic acid. In order to determine the biomechanical properties of the acellular arteries, suture retention strength, ultimate tensile strength and burst pressure measurements were performed in comparison to native tissue. Ovine endothelial cells were harvested from the femoral arteries of sheep following digestion with collagenase. Ovine smooth muscle cells were isolated from ovine arterial explant cultures. The phenotype of the cells was confirmed using antibodies to ovine vascular cell markers (myosin, α-actin, VWF, CD62) by indirect immunofluorescence.. Biocompatability of the scaffolds was assessed using contact and extract cytotoxicity tests with two cell lines (BHK and 3T3) and primary ovine vascular cells (endothelial and smooth muscle cells). The capacity of the acellular arteries to support vascular cell adhesion was determined by seeding cells onto the scaffolds and evaluation using scanning electron microscopy (SEM).. Results Histiological characterization and DNA quantification confirmed successful decellularization of porcine carotid arteries. Decellularized vessels were shown to retain the biomechanical strength and properties of native vessels. Decellularized arteries displayed no evidence of cytotoxicity to cell lines or primary vascular cells. Initial cell adhesion studies confirmed successful adherence of ovine vascular cells to decellularized arteries. Conclusion The study resulted in an acellular, biocompatible scaffold that retained the biomechanical properties of the native artery. Initial re-cellularization studies with ovine vascular cells was successful.

Anti-VEGFR2-conjugated PLGA microspheres as an x-ray phase contrast agent for assessing the VEGFR2 expression

The primary goal of this study was to evaluate the feasibility of using anti-vascular endothelial growth factor receptor 2 (VEGFR2)-conjugated poly(lactic-co-glycolic acid) (PLGA) microspheres as an x-ray phase contrast agent to assess the VEGFR2 expression in cell cultures. The cell lines, mouse LLC (Lewis lung carcinoma) and HUVEC (human umbilical vein endothelial cell), were selected for cell adhesion studies. The bound PLGA microspheres were found to better adhere to LLC cells or HUVECs than unbound ones. Absorption and phase contrast images of PLGA microspheres were acquired and compared in vitro. Phase contrast imaging (PCI) greatly improves the detection of the microspheres as compared to absorption contrast imaging. The cells incubated with PLGA microspheres were imaged by PCI, which provided clear 3D visualization of the beads, indicating the feasibility of using PLGA microspheres as a contrast agent for phase contrast CT. In addition, the microspheres could be clearly distinguished from the wall of the vessel on phase contrast CT images. Therefore, the approach holds promise for assessing the VEGFR2 expression on endothelial cells of tumor-associated vessels. We conclude that PLGA microsphere-based PCI of the VEGFR2 expression might be a novel, promising biomarker for future studies of tumor angiogenesis.

Immobilization of Gelatin onto Poly(Glycidyl Methacrylate)-Grafted Polycaprolactone Substrates for Improved Cell–Material Interactions

To enhance the cytocompatibility of polycaprolactone (PCL), cell-adhesive gelatin is covalently immobilized onto the PCL film surface via two surface-modified approaches: a conventional chemical immobilization process and a surface-initiated atom transfer radical polymerization (ATRP) process. Kinetics studies reveal that the polymer chain growth from the PCL film using the ATRP process is formed in a controlled manner, and that the amount of immobilized gelatin increases with an increasing concentration of epoxide groups on the grafted P(GMA) brushes. In vitro cell adhesion and proliferation studies demonstrate that cell affinity and growth are significantly improved by the immobilization of gelatin on PCL film surfaces, and that this improvement is positively correlated to the amount of covalently immobilized gelatin. With the versatility of the ATRP process and tunable grafting efficacy of gelatin, this study offers a suitable methodology for the functionalization of biodegradable polyesters scaffolds to improve cell-material interactions.

Functionalized Poly(γ‐Glutamic Acid) Fibrous Scaffolds for Tissue Engineering

Poly(γ-glutamic acid) (γ-PGA) is a biocompatible, enzymatically-degradable, natural polymer with a higher resistance to hydrolysis than polyesters commonly used for tissue engineering scaffolds such as poly(L-lactide) (PLLA). Notably, γ-PGA's free carboxyl side groups allow for simple chemical functionalization, making it a versatile candidate for producing scaffolds. Here, a series of water-resistant fibrous scaffolds were engineered from ethyl (Et), propyl (Pr) and benzyl (Bn) esterifications of γ-PGA. All scaffolds were non-cytotoxic and γ-PGA-Bn showed an increase in cell adhesion of hMSCs compared to γ-PGA-Et and γ-PGA-Pr. Moreover, cells on γ-PGA-Bn showed three-fold higher viability at day 14 and significantly higher adhesion when compared with PLLA scaffolds, despite having a similar hydrophobicity. Cell attachment decreased by 40% when the polymer was only partially modified with benzyl groups (γ-PGA-Bn-77%), but was restored when integrin-binding RGD peptide was conjugated to the remaining free carboxylic groups, indicating the peptide was accessible and able to bind integrins. The mechanism behind the cell-material interactions on γ-PGA-Bn scaffolds was further investigated through protein adsorption and fibronectin conformation experiments. These results, in addition to the cell-adhesion studies, suggest an inherent effect of the benzyl modification in the mechanism of cell attachment to γ-PGA-Bn scaffolds. Finally, γ-PGA-Bn scaffolds cultured in osteogenic media were also efficient in supporting hMSCs differentiation towards an osteogenic lineage as determined by alkaline phosphatase and Runx2 gene expression. Taken together these data suggest that esterified γ-PGA polymer scaffolds are new and versatile candidates for tissue engineering applications and that, intriguingly, aromatic functionality plays a key role in the cell-scaffold interaction.

Investigating the morphological, mechanical and degradation properties of scaffolds comprising collagen, gelatin and elastin for use in soft tissue engineering

Collagen-based scaffolds can be used to mimic the extracellular matrix (ECM) of soft tissues and provide support during tissue regeneration. To better match the native ECM composition and mechanical properties as well as tailor the degradation resistance and available cell binding motifs, other proteins or different collagen types may be added. The present study has explored the use of components such as gelatin or elastin and investigated their effect on the bulk physical properties of the resulting scaffolds compared to those made from pure collagen type I. The effect of altering the composition and crosslinking was evaluated in terms of the scaffold structure, mechanical properties, swelling, degradation and cell attachment. Results demonstrate that scaffolds based on gelatin had reduced tensile stiffness and degradation time compared with collagen. The addition of elastin reduced the overall strength and stiffness of the scaffolds, with electron microscopy results suggesting that insoluble elastin interacts best with collagen and soluble elastin interacts best with gelatin. Carbodiimide crosslinking was essential for structural stability, strength and degradation resistance for scaffolds of all compositions. In addition, preliminary cell adhesion studies showed these highly porous structures (pore size 130–160 μm) to be able to support HT1080 cell infiltration and growth. Therefore, this study suggests that the use of gelatin in place of collagen, with additions of elastin, can tailor the physical properties of scaffolds and could be a design strategy for reducing the overall material costs.

Hybrid Carbon-Based Scaffolds for Applications in Soft Tissue Reconstruction

Current biomedical scaffolds utilized in surgery to repair soft tissues commonly fail to meet the optimal combination of biomechanical and tissue regenerative properties. Carbon is a scaffold alternative that potentially optimizes the balance between mechanical strength, durability, and function as a cell and biologics delivery vehicle that is necessary to restore tissue function while promoting tissue repair. The goals of this study were to investigate the feasibility of fabricating hybrid fibrous carbon scaffolds modified with biopolymer, polycaprolactone and to analyze their mechanical properties and ability to support cell growth and proliferation. Environmental scanning electron microscopy, micro-computed tomography, and cell adhesion and cell proliferation studies were utilized to test scaffold suitability as a cell delivery vehicle. Mechanical properties were tested to examine load failure and elastic modulus. Results were compared to an acellular dermal matrix scaffold control (GraftJacket(®) [GJ] Matrix), selected for its common use in surgery for the repair of soft tissues. Results indicated that carbon scaffolds exhibited similar mechanical maximums and capacity to support fibroblast adhesion and proliferation in comparison with GJ. Fibroblast adhesion and proliferation was collinear with carbon fiber orientation in regions of sparsely distributed fibers and occurred in clusters in regions of higher fiber density and low porosity. Overall, fibroblast adhesion and proliferation was greatest in lower porosity carbon scaffolds with highly aligned fibers. Stepwise multivariate regression showed that the variability in maximum load of carbon scaffolds and controls were dependent on unique and separate sets of parameters. These finding suggested that there were significant differences in the functional implications of scaffold design and material properties between carbon and dermis derived scaffolds that affect scaffold utility as a tissue replacement construct.

Biocompatible and Antibacterial Nanofibrous Poly(ϵ-caprolactone)-Nanosilver Composite Scaffolds for Tissue Engineering Applications

Biodegradable polymers have been developed for medical applications such as surgical sutures, drug delivery devices, tissue supports and implants for interior bone fixation. However, implants are highly susceptible to microbial adhesion, which can ultimately lead to the formation of bio-films. The goal of the current study was to fabricate a biocompatible and antibacterial nanofibrous poly(ϵ-caprolactone) (PCL) scaffold for tissue engineering applications. To develop such a scaffold, silver nanoparticles synthesized by a novel in situ reduction route were incorporated into the PCL matrix during the process of electrospinning. The electrospun PCL and composite PCL/nanosilver fiber mats were characterized for their physico-chemical parameters using UV-VIS, SEM, XRD, FTIR and EDAX. Antibacterial activity of the composite scaffold was tested against Staphylococcus aureus using disc diffusion method and cytotoxicity evaluated using alamar blue assay. Cell adhesion studies carried out using human Mesenchymal Stem Cells (hMSCs) seeded on the scaffold containing the lowest concentration of silver nanoparticles (0.2 mM) revealed that Ag nanoparticles can be effectively used as a growth inhibitor of microorganisms, without compromising on the cell adhesion. Thus, nanosilver incorporated PCL fibrous scaffold can be a potential candidate for tissue engineering applications, possessing multifunctional properties.

Deletion of tenascin-C gene exacerbates atherosclerosis and induces intraplaque hemorrhage in Apo-E-deficient mice

Tenascin-C (TNC), a matricellular protein, is up-regulated in atherosclerotic plaques. We investigated whether the deletion of TNC gene affects the development of atherosclerosis in a murine model. TNC-/-/apo E-/- mice were generated and used for atherosclerosis studies. We compared these results to those observed in control groups of apo E-/- mice. The en face analysis of aortic area showed that the mean aortic lesion area of the double knockout (KO) mice was significantly higher than that of control mice at different times after feeding of atherogenic diet; the accumulation of lesional macrophages and lipids was significantly higher. Analysis of cell adhesion molecules revealed that vascular cell adhesion molecule-1 (VCAM-1), but not intercellular adhesion molecule-1, was up-regulated 1 week after feeding of atherogenic diet in the double KO mouse as compared to apo E-/- mouse. Cell culture studies revealed that the expression of VCAM-1 in endothelial cells isolated from the double KO mouse is more sensitive to the tumor necrosis factor α stimulation than the cells isolated from apo E-/- mice. Cell adhesion studies showed that the adherence of RAW monocytic cells to the endothelial cells was significantly enhanced in the cultured endothelial cells from the TNC gene-deleted cells. Following the prolonged feeding of an atherogenic diet (28-30 weeks), the aortic and carotid atherosclerotic lesions frequently demonstrated large grossly visible areas of intraplaque hemorrhage in the double KO mice compared to control. These data unveil a protective role for TNC in atherosclerosis and suggest that TNC signaling may have the potential to reduce atherosclerosis, in part by modulating VCAM-1 expression.

Poly (l-lactide-co-Є caprolactone) microspheres laden with bioactive glass-ceramic and alendronate sodium as bone regenerative scaffolds

Microspheric scaffolds of poly-(lactide-co-caprolactone) loaded with alendronate sodium, a family precursor of bisphosphonate drug and bioactive glass-ceramic (BGS) were prepared for the treatment of osteoporosis like bone defects with the rationale of getting a combined effect/concurrent advantage of osteoclast apoptosis as well as the augmentation of bone regeneration. The porous microspheres were generated by oil in water/solvent evaporation technique. The distribution of bioactive glass-ceramic was evidenced by the microcomputed tomography (μ-CT) and scanning electron microscopy analyses. The microspheres were evaluated for their in vitro cytocompatibility using L929 cell line and were found to be noncytotoxic. The osteoinductivity of the scaffold was assessed by its response in simulated body fluid and observed an excellent hydroxy carbonate apatite (HCA) layer formation on the surface which revealed the bone bonding and bone regeneration capability of the scaffold. The cell adhesion studies was performed with L-929 cell line and a marking cell growth on the surface as well as in the pores of the bioactive glass-ceramic as well as bioactive glass-ceramic cum drug incorporated microspheres was evidenced by the Confocal laser scanning microscopy (CLSM) investigation. No cell adhesion was observed onto the surface of the bare microspheres prepared by the copolymer alone where as the bioactive glass-ceramic and drug cum bioactive glass-ceramic loaded microspheres were found to promote the cell adhesion. The viability of the adhered cells on the microspheres was checked by flourescein diacetate (FDA) staining and it was observed that the adhered cells were viable and metabolically active. The release of the drug, alendronate sodium, directly into the problem site makes the presently prepared microsphere superior to the oral variety of drug available which is associated with oral discomfort and low bioavailability.

The Influence of Silkworm Species on Cellular Interactions with Novel PVA/Silk Sericin Hydrogels

Sericin peptides and PVA are chemically modified with methacrylate groups to produce a covalent PVA/sericin hydrogel. Preservation of the sericin bioactivity following methacrylation is confirmed, and PVA/sericin hydrogels are fabricated for both B. mori and A. mylitta sericin. Cell adhesion studies confirm the preservation of sericin bioactivity post incorporation in PVA gels. PVA/A. mylitta gels are observed to facilitate cell adhesion to a significantly greater degree than PVA/B. mori gels. Overall, the incorporation of sericin does not alter the physical properties of the PVA hydrogels but does result in significantly improved cellular interaction, particularly from A. mylitta gels.

Circular, nanostructured and biofunctionalized hydrogel microchannels for dynamic cell adhesion studies

We report on a method to fabricate biofunctionalized polyethylene glycol hydrogel microchannels with adjustable circular cross-sections. The inner channel surfaces are decorated with Au-nanoparticle arrays of tunable density. These Au-nanoparticles are functionalized with biomolecules whereas the hydrogel material provides an inert and biocompatible background. This technology provides control over flow conditions, channel curvature and biomolecule density on the channel surface. It can be applied for biophysical studies of cell-surface interactions mimicking, for example, leukocyte interactions with the endothelial lining in small vessels.

Cell behavior on a CCN1 functionalized elastin-mimetic protein polymer

We report the design of an elastin-mimetic triblock copolymer with the ability to guide endothelial cell adhesion, spreading, and migration while maintaining the elastomeric properties of the protein polymer. The V2 ligand sequence from matricellular protein CCN1 (cysteine-rich 61, CYR61) was multimerized and cloned into elastin polymer LysB10, creating LysB10.V2. Cell adhesion studies demonstrated that a LysB10.V2 surface density of at least 40 pmol/cm 2 was required to elicit cell attachment. Peptide blocking studies confirmed V2 specific engagement with integrin receptor α vβ 3 ( P < 0.05) and we observed the formation of actin stress fiber networks and vinculin clustering, characteristic of focal adhesion assembly. Haptotatic migration assays demonstrated the ability of LysB10.V2 surfaces to stimulate migration of endothelial cells ( P < 0.05). Significantly, we illustrated the ability of LysB10.V2 to support a quiescent endothelium. The CCN1 molecule functions to support many key biological processes necessary for tissue repair and thus presents a promising target for bioengineering applications. Collectively, our results demonstrate the potential to harness CCN1 specific function in the design of new scaffold materials for applications in regenerative medicine.

Electrochemical “Switching” of Si(100) Modular Assemblies

We report on a modular approach for producing well-defined and electrochemically switchable surfaces on Si(100). The switching of these surfaces is shown to change a Si(100) surface from resistant to cell adsorption to promoting cell adhesion. The electrochemical conversion of the modified electrode surface is demonstrated by X-ray photoelectron spectroscopy, X-ray reflectometry, contact angle and cell adhesion studies.

Biomimetic surface modification of titanium surfaces for early cell capture by advanced electrospinning

The time required for osseointegration with a metal implant having a smooth surface ranges from three to six months. We hypothesized that biomimetic coating surfaces with poly(lactic-co-glycolic acid) (PLGA)/collagen fibers and nano-hydroxyapatite (n-HA) on the implant would enhance the adhesion of mesenchymal stem cells. Therefore, this surface modification of dental and bone implants might enhance the process of osseointegration. In this study, we coated PLGA or PLGA/collagen (50:50 w/w ratio) fiber on Ti disks by modified electrospinning for 5 s to 2 min; after that, we further deposited n-HA on the fibers. PLGA fibers of fiber diameter 0.957 ± 0.357 µm had a contact angle of 9.9 ± 0.3° and PLGA/collagen fibers of fiber diameter 0.378 ± 0.068 µm had a contact angle of 0°. Upon n-HA incorporation, all the fibers had a contact angle of 0° owing to the hydrophilic nature of n-HA biomolecule. The cell attachment efficiency was tested on all the scaffolds for different intervals of time (10, 20, 30 and 60 min). The alkaline phosphatase activity, cell proliferation and mineralization were analyzed on all the implant surfaces on days 7, 14 and 21. Results of the cell adhesion study indicated that the cell adhesion was maximum on the implant surface coated with PLGA/collagen fibers deposited with n-HA compared to the other scaffolds. Within a short span of 60 min, 75% of the cells adhered onto the mineralized PLGA/collagen fibers. Similarly by day 21, the rate of cell proliferation was significantly higher (p ⩽ 0.05) on the mineralized PLGA/collagen fibers owing to enhanced cell adhesion on these fibers. This enhanced initial cell adhesion favored higher cell proliferation, differentiation and mineralization on the implant surface coated with mineralized PLGA/collagen fibers.

Biomolecular modification of carbon nanotubes for studies of cell adhesion and migration

We report a strategy for tailoring and patterning carbon nanotubes (CNTs) for biospecificcell studies. We synthesized a new electroactive hydroquinone terminated pyrene moleculeto tailor CNTs. These modified CNTs can be oxidized and chemoselectively reactedwith oxyamine tethered ligands to generate various ligand tethered CNTs. Acell adhesive Arg–Gly–Asp peptide (RGD) is immobilized to the CNTs and anew microfluidic patterning method is employed to generate multiplex patternedsurfaces for biospecific cell adhesion and migration studies. This work demonstratesthe integration of a new functionalization strategy to immobilize a variety ofligands to CNTs for a range of potential drug delivery, tissue imaging and cellularbehavior studies and a microfluidic patterning strategy for generating complexhigh-throughput surfaces for biotechnological and cell based assay applications.

The Integrin α2 Dimorphism E534K Modulates Platelet Binding to Decorin but Not Collagen I,

Abstract 3256 Background.Integrin a2b1-mediated adhesion to collagens supports cellular attachment, while decorin binding by a2b1 often attenuates adhesion. Collagen I binds to the a2 I-domain via the triple-helical sequence GFOGER, but the decorin binding site is not within the a2 I-domain and has not yet been identified. A single nucleotide polymorphism in the a2 gene ITGA2 (rs1801106) (G1600A) resulting in the amino acid substitution glutamate-534 to lysine-534 (E534K) is the basis for one of the most important human platelet alloantigen (HPA) systems, HPA-5, yet HPA-5 alleles do not influence the binding of a2b1 to collagen I, and the effect of HPA-5 on platelet function, if any, has not been determined. We sought to determine whether the minor allele HPA-5b (534K) might influence the a2b1-mediated adhesion of platelets to a physiologically relevant ligand other than collagen I. One such alternative ligand is decorin, an extracellular matrix small leucine (Leu)-rich proteoglycan (SLRP). Methods/Results. Two groups of normal subjects were compared. The first group (GG) consisted of ten donors homozygous for the major allele rs1801106G. The second group (GA+AA) included one donor homozygous for the minor allele rs1801106A and nine donors heterozygous for these alleles. Aside from this, there were no significant differences between the two groups with respect to platelet count, mean platelet volume, surface expression of four selected platelet receptors, GPIba, GPVI, aIIbb3 or a2b1, or the allelic distribution of five receptor genes, ITGA2B rs5911, ITGB3 rs5918, GP1BA rs6065, GP6 rs1613662 and P2RY1 rs1065776. In direct platelet adhesion assays, we determined that platelets from GG donors bound more strongly to decorin than those from GA+AA donors (p < 0.01), while platelets from either group bound equally well to collagen I (p = 0.73). Using platelets from donors homozygous for the major allele rs1801106G, adhesion to decorin was significantly inhibited by human alloantibodies specific for HPA-5a but not by GFOGER or an a2-specific monoclonal antibody 6F1 known to inhibit cell adhesion to collagen I. Conversely, GFOGER and 6F1 inhibited adhesion to collagen I but not decorin. Conclusions. The simplest explanation of our findings is that 534E, located in the a2 b-propeller domain, is necessary for maximal binding of a2b1 to decorin but not collagen I. These results suggest that 534E contributes to the decorin binding site and that this amino acid represents a potential target for interventions that can modify cell adhesion to decorin and perhaps other proteoglycans. This also represents the first instance of a functional difference attributable to the HPA-5 alleles. These results expand our understanding of the decorin and collagen I interactions described in murine and human studies of cell adhesion and cancer biology, where decorin and collagen I often have opposite effects that are both mediated by a2b1. Decorin knockout (Dcn(−/−)) murine embryonic fibroblasts exhibit greater adhesion to collagen and greater migration on collagen substrates, while decorin attenuates the aggressiveness and metastasis of tumor cells with diverse histologic backgrounds. Further studies of the relationship between the collagen I and decorin binding sites on integrin a2 are warranted, particularly regarding its influence on thrombosis and hemostasis. Disclosures:No relevant conflicts of interest to declare.

Evaluation of Substrata Effect on Cell Adhesion Properties Using Freestanding Poly(l-lactic acid) Nanosheets

Investigation of the interactions between cells and material surfaces is important not only for the understanding of cell biology but also for the development of smart biomaterials. In this study, we investigated the substrate-related effects on the interaction between cell and polymeric ultrathin film (nanosheet) by modulating the mechanical properties of the nanosheet with a metal substrate or mesh. A freestanding polymeric nanosheet with tens-of-nanometers thickness composed of poly(L-lactic acid) (PLLA nanosheet) was fabricated by combination of a spin-coating technique and a water-soluble sacrificial layer. The freestanding PLLA nanosheet was collected on a stainless steel mesh (PLLA-mesh) and subsequently used for cell adhesion studies, comparing the results to the ones on a control SiO(2) substrate coated with an ultrathin layer of PLLA (PLLA-substrate). The adhesion of rat cardiomyocytes (H9c2) was evaluated on both samples after 24 h of culture. The PLLA-mesh with the tens-of-nanometers thick nanosheets induced an anisotropic adhesion of H9c2, while H9c2 on the PLLA-substrate showed an isotropic adhesion independent from the nanosheet thickness. Interestingly, an increment in the nanosheet thickness in the PLLA-mesh samples reduced the cellular anisotropy and led to a similar morphology to the PLLA-substrate. Considering the huge discrepancy of Young's modulus between PLLA nanosheet (3.5-4.2 GPa) and metal substrate (hundreds of GPa), cell adhesion was mechanically regulated by the Young's modulus of the underlying substrate when the thickness of the PLLA nanosheet was tens of nanometers. Modulation of the stiffness of the polymeric nanosheet by utilizing a rigid underlying material will allow the constitution of a unique cell culture environment.

Imaging molecular dynamics in vivo – from cell biology to animal models

Advances in fluorescence microscopy have enabled the study of membrane diffusion, cell adhesion and signal transduction at the molecular level in living cells grown in culture. By contrast, imaging in living organisms has primarily been restricted to the localization and dynamics of cells in tissues. Now, imaging of molecular dynamics is on the cusp of progressing from cell culture to living tissue. This transition has been driven by the understanding that the microenvironment critically determines many developmental and pathological processes. Here, we review recent progress in fluorescent protein imaging in vivo by drawing primarily on cancer-related studies in mice. We emphasize the need for techniques that can be easily combined with genetic models and complement fluorescent protein imaging by providing contextual information about the cellular environment. In this Commentary we will consider differences between in vitro and in vivo experimental design and argue for an approach to in vivo imaging that is built upon the use of intermediate systems, such as 3-D and explant culture models, which offer flexibility and control that is not always available in vivo. Collectively, these methods present a paradigm shift towards the molecular-level investigation of disease and therapy in animal models of disease.

Biocompatibilty of starch-based films from starch of Andean crops for biomedical applications

In this communication we report the use of starch films as cell substrates. To the best of our knowledge it is the first time that films prepared from native Andean starches are studied as biomaterials. For the present study 3T3 fibroblast cells were seeded in seventeen novel starch based films from different Andean crops. In order to analyze the use of these types of starch as biomedical materials, biocompatibility, viability and cell adhesion studies were performed at the third day of incubation on supplemented DMEM medium. After cultured, films made from starch of “tunta”, “muro-huayro” potato and white carrot showed the highest level of living cells and cell viability. These results indicate that native starches from Andean crops can be used for biomedical applications.