A dynamic study of the structural change in the binary network in response to guest inclusion.

In the present work flexible binary networks of 1,3,5-benzenetricarboxylic acid (TMA) with 4,4'-bipyridine (Bpy) or 1,3,5-tris(4-pyridyl)-2,4,6-triazine(TPTZ) molecules at the liquid-solid interface were constructed. When coronene (COR) molecules are introduced into these systems, the binary networks collapse and at the same time, new COR/TMA host-guest structures are formed. Both experiments and calculations unambiguously indicate that the COR/TMA host-guest complex structure has stronger adsorption energy, resulting in the deconstruction-reconstruction phenomenon.

Beta structure motifs of islet amyloid polypeptides identified through surface-mediated assemblies.

We report here the identification of the key sites for the beta structure motifs of the islet amyloid polypeptide (IAPP) analogs by using scanning tunneling microscopy (STM). Duplex folding structures in human IAPP(8-37) (hIAPP(8-37)) assembly were observed featuring a hairpin structure. The multiplicity in rIAPP assembly structures indicates the polydispersity of the rat IAPP(8-37) (rIAPP(8-37)) beta-like motifs. The bimodal length distribution of beta structure motifs for rIAPP(8-37) R18H indicates the multiple beta segments linked by turns. The IAPP(8-37) analogs share common structure motifs of IAPP(8-17) and IAPP(26-37) with the most probable key sites at positions around Ser(19)/Ser(20) and Gly(24). These observations reveal the similar amyloid formation tendency in the C and N terminus segments because of the sequence similarity, while the differences in specific amino acids at each key site manifest the effect of sequence variations. The results could be beneficial for studying structural polymorphism of amyloidal peptides with multiple beta structure motifs.

Recent advances in lipid nanovesicles for targeted treatment of spinal cord injury.

The effective regeneration and functional restoration of damaged spinal cord tissue have been a long-standing concern in regenerative medicine. Treatment of spinal cord injury (SCI) is challenging due to the obstruction of the blood-spinal cord barrier (BSCB), the lack of targeting of drugs, and the complex pathophysiology of injury sites. Lipid nanovesicles, including cell-derived nanovesicles and synthetic lipid nanovesicles, are highly biocompatible and can penetrate BSCB, and are therefore effective delivery systems for targeted treatment of SCI. We summarize the progress of lipid nanovesicles for the targeted treatment of SCI, discuss their advantages and challenges, and provide a perspective on the application of lipid nanovesicles for SCI treatment. Although most of the lipid nanovesicle-based therapy of SCI is still in preclinical studies, this low immunogenicity, low toxicity, and highly engineerable nanovesicles will hold great promise for future spinal cord injury treatments.

Nanoscale electrowetting effects observed by using friction force microscopy.

We report the study of electrowetting (EW) effects under strong electric field on poly(methyl methacrylate) (PMMA) surface by using friction force microscopy (FFM). The friction force dependence on the electric field at nanometer scale can be closely related to electrowetting process based on the fact that at this scale frictional behavior is highly affected by capillary phenomena. By measuring the frictional signal between a conductive atomic force microscopy (AFM) tip and the PMMA surface, the ideal EW region (Young-Lippmann equation) and the EW saturation were identified. The change in the interfacial contact between the tip and the PMMA surface with the electric field strength is closely associated with the transition from the ideal EW region to the EW saturation. In addition, a reduction of the friction coefficient was observed when increasing the applied electric field in the ideal EW region.

BCAR1 plays critical roles in the formation and immunoevasion of invasive circulating tumor cells in lung adenocarcinoma.

Background: We investigated the roles of breast cancer anti-estrogen resistance 1 (BCAR1/p130Cas) in the formation and immunoevasion of invasive circulating tumor cells (CTCs) in lung adenocarcinoma (LUAD). Methods: Biomarkers of CTCs including BCAR1 and CD274, were evaluated by the CanPatrol method. Proteomics analysis of LUAD cells and exosomes after BCAR1 overexpression (BCAR1-OE) was performed by mass spectrometry. Cell functions and relevant signaling pathways were investigated after BCAR1 knockdown (BCAR1-KO) or BCAR1-OE in LUAD cells. Lastly, in vitro and in vivo experiments were performed to confirm the roles of BCAR1 in the formation and immunoevasion of CTCs. Results: High expression of BCAR1 by CTCs correlated with CD274 expression and epithelial-to-mesenchymal transition (EMT). RAC1, together with BCAR1, was found to play an important role in the carcinogenesis of LUAD. RAC1 functioned with BCAR1 to induce EMT and to enhance cell proliferation, colony formation, cell invasion and migration, and anoikis resistance in LUAD cells. BCAR1 up-regulated CD274 expression probably by shuttling the short isoform of BRD4 (BRD4-S) into the nucleus. CTCs, as well as tumor formation, were prohibited in nude mice xenografted with BCAR1-KO cells. The co-expression of BCAR1/RAC1 and BCAR1/CD274 was confirmed in LUAD. BCAR1 expression in LUAD is an indicator of poor prognosis, and it associates with immunoevasion. Conclusion: BCAR1, as a new target for the treatment of LUAD, plays roles in the formation and immunoevasion of invasive CTCs. The mechanism includes triggering EMT via RAC1 signaling and up-regulating CD274 expression by shuttling BRD4-S into the nucleus.

Patterning of 293T fibroblasts on a mica surface.

Controllable cell growth on the defined areas of surfaces is important for potential applications in biosensor fabrication and tissue engineering. In this study, controllable cell growth was achieved by culturing 293 T fibroblast cells on a mica surface which had been patterned with collagen strips by a microcontact printing (microCP) technique. The collagen area was designed to support cell adhesion and the native mica surface was designed to repel cell adhesion. Consequently, the resulting cell patterns should follow the micro-patterns of the collagen. X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurement, atomic-force microscope (AFM) observation, and force-curve measurement were used to monitor property changes before and after the collagen adsorption process. Further data showed that the patterned cells were of good viability and able to perform a gene-transfection experiment in vitro. This technique should be of potential applications in the fields of biosensor fabrication and tissue engineering.

Identification of a peripheral substitution symmetry effect in self-assembled architectures.

Two complementary classes of molecules based on a triphenylene core are synthesized. The two-dimensional (2D) assemblies of these molecules deposited on a highly oriented pyrolytic graphite (HOPG) surface are identified with scanning tunneling microscopy (STM). Structures with large cavities are formed by symmetric molecules, while uniform and closely packed stripe-assembled structures are obtained for asymmetric molecules. X-ray diffraction (XRD) results support the observation of an ordered hexagonal columnar mesophase for symmetric molecules and a rectangular columnar mesophase for asymmetric molecules. The study demonstrates that the substitution symmetry has significant effects on the assembly characteristics of molecular architectures and also on the three-dimensional (3D) macroscopic properties of the molecular materials.

Identification of high independent prognostic value of nanotechnology based circulating tumor cell enumeration in first-line chemotherapy for metastatic breast cancer patients.

Enumeration of circulating tumor cells (CTCs) is a promising tool in the management of metastatic breast cancer (MBC). This study investigated the capturing efficiency and prognostic value of our previously reported peptide-based nanomagnetic CTC isolation system (Pep@MNPs). We counted CTCs in blood samples taken at baseline (n = 102) and later at patients' first clinical evaluation after starting firstline chemotherapy (n = 72) in a cohort of women treated for MBC. Their median follow-up was 16.3 months (range: 9.0-31.0 months). The CTC detection rate was 69.6 % for the baseline samples. Patients with ≤2 CTC/2 ml at baseline had longer median progression-free survival (PFS) than did those with >2 CTC/2 ml (17.0 months vs. 8.0 months; P = 0.002). Patients with ≤2 CTC/2 ml both at baseline and first clinical evaluation had longest PFS (18.2 months) among all patient groups (P = 0.004). Particularly, among patients with stable disease (SD; per imaging evaluation) our assay could identify those with longer PFS (P < 0.001). Patients with >2 CTC/2 ml at baseline were also significantly more likely to suffer liver metastasis (P = 0.010). This study confirmed the prognostic value of Pep@MNPs assays for MBC patients who undergo firstline chemotherapy, and offered extra stratification regarding PFS for patients with SD, and a possible indicator for patients at risk for liver metastasis.

[Atomic force microscopic observation of the neurons membrane in primary culture after treatment with N-Methyl-D-Asph].

OBJECTIVE: To observe the changes in three-dimensional morphology of the membrane of the cortex neurons in primary culture in response to treatment with N-Methyl-D-Asp (NMDA) and MK-801 using atomic force microscope (AFM). METHODS: Following NMDA treatment, the changes in the membrane of the neurons fixed by glutaraldehyhyde were examined, and the protective effect of MK-801 on the neurons was also observed using an ATM at the resolution of 0.01-0.1 nm. RESULTS: Normal neurons presented smooth membrane surface with regular undulation and densely but well arrayed protein granules. In response to NMDA treatment, the neurons were disrupted, falling into small pieces, and their membrane appeared discontinuous. MK-801 treatment increased the folds of the membrane that showed rough edges, with membrane undulation only secondary to normal condition. CONCLUSION: AFM, with the merits of high resolution and easy sample preparation, can finely display the three-dimensional morphology of the surface of the neurons, which, after NMDA treatment, becomes disintegrated with increased bulk of the protein granules, deepened caving of the lipids, and rougher membrane surface.

Large electric field-enhanced-hardness effect in a SiO2 film.

Silicon dioxide films are extensively used in nano and micro-electromechanical systems. Here we studied the influence of an external electric field on the mechanical properties of a SiO2 film by using nanoindentation technique of atomic force microscopy (AFM) and friction force microscopy (FFM). A giant augmentation of the relative elastic modulus was observed by increasing the localized electric field. A slight decrease in friction coefficients was also clearly observed by using FFM with the increase of applied tip voltage. The reduction of the friction coefficients is consistent with the great enhancement of sample hardness by considering the indentation-induced deformation during the friction measurements.

Nanomaterials for reducing amyloid cytotoxicity.

This review is intended to reflect the recent progress on therapeutic applications of nanomaterials in amyloid diseases. The progress on anti-amyloid functions of various nanomaterials including inorganic nanoparticles, polymeric nanoparticles, carbon nanomaterials and biomolecular aggregates, is reviewed and discussed. The main functionalization strategies for general nanoparticle modifications are reviewed for potential applications of targeted therapeutics. The interaction mechanisms between amyloid peptides and nanomaterials are discussed from the perspectives of dominant interactions and kinetics. The encapsulation of anti-amyloid drugs, targeted drug delivery, controlled drug release and drug delivery crossing blood brain barrier by application of nanomaterials would also improve the therapeutics of amyloid diseases.

Determination of the surface charge density and temperature dependence of purple membrane by electric force microscopy.

We report here the measurement of the temperature-dependent surface charge density of purple membrane (PM) by using electrostatic force microscopy (EFM). The surface charge density was measured to be 3.4 × 10(5) e/cm(2) at room temperature and reaches the minimum at around 52 °C. The initial decrease of the surface charge density could be attributed to the reduced dipole alignment because of the thermally induced protein mobility in PM. The increase of charge density at higher temperature could be ascribed to the weakened interaction between proteins and the lipids, which leads to the exposure of the charged amino acids. This work could be a benefit to the direct assessment of the structural stability and electric properties of biological membranes at the nanoscale.

Polymeric effects on DNA condensation by cationic polymers observed by atomic force microscopy.

Compaction of DNA by condensing agents can provide insights into DNA assembly processes, which is keenly related to the essence of gene transfection and gene therapy in vivo. In this paper, the morphology of different cationic polymer/DNA complexes was studied by using atomic force microscopy (AFM), which is keen to the mechanism of DNA condensation induced by amine-based cationic block copolymers with poly(poly(ethylene glycol) methyl ether methacrylate). It is found that the structures and dimensions of condensing agent/DNA complexes are sensitively dependent on the condensing agents. The size of DNA aggregates can be affected appreciably by polymers rather than monomers. The amount of nitrogen elements per polymer unit, rather than the molecular weights of polymers, appears to be more effective on the dimension of the condensates. The impact of the copolymer chain structures on the DNA aggregates indicates an effective venue for regulating the dimensions and structures of the DNA condensates, which is beneficial for optimizing delivery systems for gene transfection.

Self-assembly of a novel alternant amphiphilic poly(OPE-alt-TEO) copolymer: from nanowires to twist fibrillar architectures with molecular dimensions.

A novel alternant amphiphilic polymer poly[1,4-bis(phenylethynyl)-2,5-bis(hexyloxy)benzene-alt-tetra(ethylene oxide)] was prepared. Atom force microscope (AFM) images showed that the molecular self-assembly morphologies changed from molecular nanowires to twist fibrillar architectures with the increase of the solution concentrations. Short and thin wires formed in dilute solution, while large bundles developed in relatively concentrated ones, shown by fluorescence microscope images. The photoluminescence (PL) spectra of the corresponding films indicate a self-assembly process of the polymers under slow solvents evaporation. Coplanar aggregation was confirmed through PL and photoluminescence excitation (PLE) spectra. Furthermore, the self-assembly process in polymer bulk was studied by wide-angle X-ray diffraction. To the best of our knowledge, it is the first time to reveal the change of the molecular morphologies with the altering concentration for the alternant amphiphilic conjugated polymers.

Electric driven molecular switching of asymmetric tris(phthalocyaninato) lutetium triple-decker complex at the liquid/solid interface.

Molecular structures are known to significantly impact the adsorption and assembling behavior of the adsorbates on surfaces. Precise control of the molecular orientation and ordering will enable us to tailor the physical and chemical properties of the molecular architectures. In this work, we present a strategy of attaching functional groups with dissimilar adsorption and assembling characteristics to the top and bottom phthalocyaninato moieties of a triple-decker complex, and orientational-dependent ordering of such molecules at the liquid/solid interface has been identified, which is attributed to the interaction of the intrinsic molecular dipole with the external electric field. In addition, isomerization of the noncentrosymmetric tris(phthalocyaninato) lutetium triple-decker complex has been revealed directly with STM and further confirmed by theoretical simulation. This approach provides a possible way for the preparation of organic films with switchable electronic and/or interface properties with external field.

Supramolecule-regulated photophysics of oligo(p-phenyleneethynylene)-based rod-coil block copolymers: effect of molecular architecture.

Three new topology-varied rod-coil block copolymers, comprising the same oligo(p-phenyleneethynylene) (OPE) rod components and the same coil components, were synthesized by atom-transfer radical polymerization. Their photophysical properties were systematically studied and compared in consideration of their solid-state structures and self-assembly abilities. These copolymers have similar intrinsic photophysical properties to the OPE rods, as reflected in dilute solution. However, their photophysical properties in the solid state are manipulated to be dissimilar by supramolecular organization. Wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) data demonstrate that these copolymers possess different self-assembly abilities due to the molecular-architecture-dependent pi-pi interactions of the rods. Hence, the aggregates in the solid state are formed with a different mechanism for these copolymers, bringing about the discrepancy in the solid-state luminescent properties.

Bioactive surface modification of mica and poly(dimethylsiloxane) with hydrophobins for protein immobilization.

Bioactive surfaces with appropriate hydrophilicity for protein immobilization can be achieved by hydrophobin II (HFBI) self-assembly on mica and polydimethylsiloxane (PDMS) surfaces. X-ray photoelectron spectroscopy and water contact angle measurements illustrated that the surface wettability can be changed from superhydrophobic (PDMS) or superhydrophilic (mica) to moderately hydrophilic, which is suitable for protein (chicken IgG) immobilization on both substrate surfaces. The results suggest that HFBI assembly, one kind of hydrophobin from Trichoderma reesei, may be a versatile and convenient method for the immobilization of biomolecules on diverse substrates, which may have potential applications in biosensors, immunoassays, and microfluidic networks.

Star-shaped oligofluorenes end-capped with carboxylic groups: syntheses and self-assembly at the liquid-solid interface.

A series of star-shaped oligofluorenes end-capped with carboxylic acid groups were synthesized. Different numbers of carboxyl groups that can form hydrogen bonds, and long alkane chains that have stabilizing effects, were intentionally introduced. The resulting molecular architectures of the so-prepared star-shaped oligofluorenes at the liquid-solid interface were investigated by scanning tunneling microscopy. It is found that the number of hydrogen-bonding groups and the symmetry of the target molecules have crucial influences on the structures of the ordered assemblies.