One‐Step Grafting of Al2O3 onto Acid‐Made Mesoporous Silica

We report a one‐step convenient chemical coating method of high alumina content onto mesoporous silicas. Aluminia‐coated mesoporous silica with high surface area (?900 m²/g), tuneable pore size (2.0–3.0 nm) and high hydrothermal stability (> 60 h) is obtained. The method may also be generalized for grafting other metal oxides onto mesoporous silica in future work.     

Highly Stable trans‐Cyclooctene Amino Acids for Live‐Cell Labeling

trans‐Cyclooctene groups incorporated into proteins via non‐canonical amino acids (ncAAs) are emerging as specific handles for bioorthogonal chemistry. Here, we present a highly improved synthetic access to the axially and the equatorially linked trans‐cyclooct‐2‐ene isomers ( 1 a , b ). We further show that the axially connected isomer has a half‐life about 10 times higher than the equatorial isomer and reacts with tetrazines much faster, as determined by stopped‐flow experiments. The improved properties resulted in different labeling performance of the insulin receptor on the surface of intact cells.     

Potential‐Responsive Surfaces for Manipulation of Cell Adhesion,Release, and Differentiation

In living systems, interfacial molecular interactions control many biological processes. New stimuli‐responsive strategies are desired to provide versatile model systems that can regulate cell behavior in vitro. Described here are potential‐responsive surfaces that control cell adhesion and release as well as stem cell differentiation. Cell adhesion can be modulated dynamically by applying negative and positive potentials to surfaces functionalized with tailored monolayers. This process alters cell morphology and ultimately controls behavior and the fate of the cells. Cells can be detached from the electrode surface as intact clusters with different geometries using electrochemical potentials. Importantly, morphological changes during adhesion guide stem cell differentiation. The higher accessibility of the peptide under a positive applied potential causes phenotypic changes in the cells that are hallmarks of osteogenesis, whereas lower accessibility of the peptide promoted by negative potentials leads to adipogenesis.     

Magnetic Mesoporous Silica Nanoparticles Cloaked by Red Blood Cell Membranes: Applications in Cancer Therapy

Targeted drug delivery is an emerging technological strategy that enables nanoparticle systems to be responsive for tumor therapy. Magnetic mesoporous silica nanoparticles (MMSNs) were cloaked with red blood cell membrane (RBC). This integrates long circulation, photosensitizer delivery, and magnetic targeting for cancer therapy. In vivo experiments demonstrate that RBC@MMSNs can avoid immune clearance and achieve magnetic field (MF)‐induced high accumulation in a tumor. When light irradiation is applied, singlet oxygen rapidly generates from hypocrellin B (HB)‐loaded RBC@MMSN and leads to the necrosis of tumor tissue. Such a RBC‐cloaked magnetic nanocarrier effectively integrates immunological adjuvant, photosensitizer delivery, MF‐assisted targeting photodynamic therapy, which provides an innovative strategy for cancer therapy.     

Facile One‐Step Synthesis of Monodisperse Micron‐Sized Latex Particles with Highly Carboxylated Surfaces

A facile method for the aqueous synthesis of monodisperse and micronmeter‐sized colloids with highly carboxylated surfaces is presented. The method is applied to three different monomers, styrene, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate, and illustrate tuning of the size and monodispersity in the reactions. High surface density of carboxylic acids of up to 10 COOH nm⁻² from potentiometric titrations, is achieved through copolymerization with itaconic acid. The versatility of this system is highlighted by creating highly fluorescent and monodisperse particles that can be index matched in aqueous solution and through surface modification via the carboxylic acid groups using standard amidation chemistry.

     

Photoswitched Cell Adhesion on Azobenzene‐Containing Self‐Assembled Films

Stimuli‐responsive surfaces that can regulate and control cell adhesion have attracted much attention for their great potential in diverse biomedical applications. Unlike for pH‐ and temperature‐responsive surfaces, the process of photoswitching requires no additional input of chemicals or thermal energy. In this work, two different photoresponsive azobenzene films are synthesized by chemisorption and electrostatic layer‐by‐layer (LbL) assembly techniques. The LbL film exhibits a relatively loose packing of azobenzene chromophores compared with the chemisorbed film. The changes in trans/cis isomer ratio of the azobenzene moiety and the corresponding wettability of the LbL films are larger than those of the chemisorbed films under UV light irradiation. The tendency for cell adhesion on the LbL films decreases markedly after UV light irradiation, whereas adhesion on the chemisorbed films decreases only slightly, because the azobenzene chromophores stay densely packed. Interestingly, the tendency for cell adhesion can be considerably increased on rough substrates, the roughness being introduced by use of photolithography and inductively coupled plasma deep etching techniques. For the chemisorbed films on rough substrates, the amount of cells that adhere also changes slightly after UV light irradiation, whereas, the amount of cells that adhere to LbL films on rough substrates decreases significantly.     

Preparation of Gradient Surfaces by Using a Simple Chemical Reaction and Investigation of Cell Adhesion on a Two‐Component Gradient

This article describes a simple method for the generation of multicomponent gradient surfaces on self‐assembled monolayers (SAMs) on gold in a precise and predictable manner, by harnessing a chemical reaction on the monolayer, and their applications. A quinone derivative on a monolayer was converted to an amine through spontaneous intramolecular cyclization following first‐order reaction kinetics. An amine gradient on the surface on a scale of centimeters was realized by modulating the exposure time of the quinone‐presenting monolayer to the chemical reagent. The resulting amine was used as a chemical handle to attach various molecules to the monolayer with formation of multicomponent gradient surfaces. The effectiveness of this strategy was verified by cyclic voltammetry (CV), matrix assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry (MS), MS imaging, and contact‐angle measurements. As a practical application, cell adhesion was investigated on RGD/PHSRN peptide/peptide gradient surfaces. Peptide PHSRN was found to synergistically enhance cell adhesion at the position where these two ligands are presented in equal amounts, while these peptide ligands were competitively involved in cell adhesion at other positions. This strategy of generating a gradient may be further expandable to the development of functional gradient surfaces of various molecules and materials, such as DNA, proteins, growth factors, and nanoparticles, and could therefore be useful in many fields of research and practical applications.     

纳米二氧化硅影响人肺癌细胞的定量糖蛋白质组学研究

纳米二氧化硅(纳米SiO₂)是一种正在规模化生产的纳米材料, 无定型纳米SiO₂因其吸入和口服对生命体不会造成直接的危害被认为是生物安全的纳米材料, 已被广泛用于疾病诊断、生物分析和成像、药物载体等的研究中, 导致其进入人体的方式日益增多, 因此它对人体健康影响的研究对于其作为生物材料真正实现广泛应用尤为重要. 本文采用肼化学方法为基础的定量蛋白质组学对无定型纳米SiO₂进入人肺癌细胞后产生的影响进行了分析, 结果表明其进入细胞后, 导致细胞内的平衡状态发生变化, 从而影响了细胞内许多重要的蛋白质的表达水平. 部分跨膜蛋白质表达的变化对纳米SiO₂进入细胞的途径的阐明有一定的指导意义.     

Selective High‐Resolution Detection of Membrane Protein–Ligand Interaction in Native Membranes Using Trityl–Nitroxide PELDOR

The orchestrated interaction of transmembrane proteins with other molecules mediates several crucial biological processes. Detergent solubilization may significantly alter or even abolish such hetero‐oligomeric interactions, which makes observing them at high resolution in their native environment technically challenging. Dipolar electron paramagnetic resonance (EPR) techniques such as pulsed electro–electron double resonance (PELDOR) can provide very precise distances within biomolecules. To concurrently determine the inter‐subunit interaction and the intra‐subunit conformational changes in hetero‐oligomeric complexes, a combination of different spin labels is required. Orthogonal spin labeling using a triarylmethyl (TAM) label in combination with a nitroxide label is used to detect protein–ligand interactions in native lipid bilayers. This approach provides a higher sensitivity and total selectivity and will greatly facilitate the investigation of multimeric transmembrane complexes employing different spin labels in the native lipid environment.     

Artificial Formation and Tuning of Glycoprotein Networks on Live Cell Membranes: A Single‐Molecule Tracking Study

We present a method to artificially induce network formation of membrane glycoproteins and show the precise tuning of their interconnection on living cells. For this, membrane glycans are first metabolically labeled with azido sugars and then tagged with biotin by copper‐free click chemistry. Finally, these biotin‐tagged membrane proteins are interconnected with streptavidin (SA) to form an artificial protein network in analogy to a lectin‐induced lattice. The degree of network formation can be controlled by the concentration of SA, its valency, and the concentration of biotin on membrane proteins. This was verified by investigation of the spatiotemporal dynamics of the SA‐protein networks employing single‐molecule tracking. It was also proven that this network formation strongly influences the biologically relevant process of endocytosis as it is known from natural lattices on the cell surface.     

One‐Step Electrochemical Immunoassay for Carcinoembryonic Antigen in Human via Back‐Filling Immobilization of Gold Nanoparticles on DNA‐Modified Gold Electrodes

A new amperometric immunobiosensor for carcinoembryonic antigen (CEA) determination in human serum was developed via encapsulation of horseradish peroxidase‐labeled carcinoembryonic antibody (HRP‐anti‐CEA) in a gold nanoparticles/DNA composite architecture. The presences of gold nanoparticles provided a congenial microenvironment for the immobilized biomolecules and decreased the electron transfer impedance, leading to a direct electrochemical behavior of the immobilized HRP. The formation of the antibody–antigen complex by a simple one‐step immunoreaction between the immobilized HRP‐anti‐CEA and CEA in sample solution introduced a barrier of direct electrical communication between the immobilized HRP and the gold electrode surface. Under optimal conditions, the current change obtained from the labeled HRP relative to H₂O₂ system was proportional to the CEA concentration in two linear ranges from 0.5 to 15 ng/mL and 15 to 300 ng/mL with a detection limit of 0.1 ng/mL (at 3δ). The precision and reproducibility are acceptable with the intraassay CV of 6.3% and 4.7% at 8 and 60 ng/mL CEA, respectively. The storage stability of the proposed immunosensor is acceptable in a pH 7.0 PBS at 4 °C for 9 days. Moreover, the proposed immunosensors were used to analyze CEA in human serum specimens. Analytical results of clinical samples show the developed immunoassay has a promising alternative approach for detecting CEA in the clinical diagnosis.     

Control of Three‐Dimensional Cell Adhesion by the Chirality of Nanofibers in Hydrogels

In the three‐dimensional (3D) extracellular matrix (ECM), the influence of nanofiber chirality on cell behavior is very important; the helical nanofibrous structure is closely related to the relevant biological events. Herein, we describe the use of the two enantiomers of a 1,4‐benzenedicarboxamide phenylalanine derivative as supramolecular gelators to investigate the influence of the chirality of nanofibers on cell adhesion and proliferation in three dimensions. It was found that left‐handed helical nanofibers can increase cell adhesion and proliferation, whereas right‐handed nanofibers have the opposite effect. These effects are ascribed to the mediation of the stereospecific interaction between chiral nanofibers and fibronectin. The results stress the crucial role of the chirality of nanofibers on cell‐adhesion and cell‐proliferation behavior in 3D environments.     

Mass Spectrometry Assisted Lithography for the Patterning of Cell Adhesion Ligands on Self‐Assembled Monolayers

Pattern of events : A simple and flexible method has been developed for patterning cell adhesion ligands. Locally erasing self‐assembled monolayers with tri(ethyleneglycol) groups on a gold substrate by using a MALDI‐TOF MS nitrogen laser and filling the exposed gold surface with an alkanethiol presenting carboxylic acid groups enables subsequent immobilization of maleimide and a cell adhesion peptide, which can then recognize cells (see scheme).

     

High‐Throughput,Label‐Free Isolation of Cancer Stem Cells on the Basis of Cell Adhesion Capacity

Herein we report a microfluidics method that enriches cancer stem cells (CSCs) or tumor‐initiating cells on the basis of cell adhesion properties. In our on‐chip enrichment system, cancer cells were driven by hydrodynamic forces to flow through microchannels coated with basement membrane extract. Highly adhesive cells were captured by the functionalized microchannels, and less adhesive cells were collected from the outlets. Two heterogeneous breast cancer cell lines (SUM‐149 and SUM‐159) were successfully separated into enriched subpopulations according to their adhesive capacity, and the enrichment of the cancer stem cells was confirmed by flow cytometry biomarker analysis and tumor‐formation assays. Our findings show that the less adhesive phenotype is associated with a higher percentage of CSCs, higher cancer‐cell motility, and higher resistance to chemotherapeutic drugs.     

Adhesion of Human U937 Monocytes to Nitrogen‐Rich Organic Thin Films: Novel Insights into the Mechanism of Cellular Adhesion

We present a two‐fold study designed to elucidate the adhesion mechanism of human U937 monocytes on novel N‐rich thin films deposited by plasma‐ and VUV photo‐polymerisation, so‐called “PVP:N” materials. It is shown that there exist sharply‐defined (“critical”) surface‐chemical conditions that are necessary to induce cell adhesion. By comparing the film chemistries at the “critical” conditions, we demonstrate the dominant role of primary amines in the cell adhesion mechanism. Quantitative real‐time RT‐PCR experiments using U937 cells that had adhered to PVP:N materials for up to 24 h are presented. The adhesion induces a transient expression of cytokines, markers of macrophage activation, as well as a more sustained expression of PPARγ and ICAM‐I.