31P and 13C NMR Investigations of a Tert Butylcalix[4]Arene-Diphosphate

Abstract

The lanthanide induced ³¹P and ¹³C shifts for calix[4]arenediphosphate 1 are studied. From these investigations an exact assignment of all the 48 C atoms was possible.     

Bio‐Orthogonal Polymer Coatings for Co‐Presentation of Biomolecules

Controlled presentation of biomolecules on synthetic substrates is an important aspect for biomaterials development. If the immobilization of multiple biomolecules is required, highly efficient orthogonal surface chemistries are needed to ensure the precision of the immobilization. In this communication, chemical vapor deposition (CVD) copolymerization is used to fabricate polymer coatings with controlled ratio of alkyne and pentafluorophenyl ester (Pfp‐ester) groups. Cyclic argine‐glycine‐aspartic acid (cRGD) adhesion peptide and epidermal growth factor (EGF) are immobilized through alkyne–azide cycloaddtion (“click” chemistry) and active ester–amine reaction, respectively. Cell studies with human umbilical vein endothelial cells (HUVEC) and A431 cell lines demonstrate the biological activity of the coimmobilized biomolecules.     

Compartmentalized Photoreactions within Compositionally Anisotropic Janus Microstructures

We demonstrate spatially controlled photoreactions within bicompartmental microparticles and microfibers. Selective photoreactions are achieved by anisotropic incorporation of photocrosslinkable poly(vinyl cinnamate) in one compartment of either colloids or microfibers. Prior to photoreaction, bicompartmental particles, and fibers were prepared by EHD co‐jetting of two compositionally distinct polymer solutions. Physical and chemical anisotropy was confirmed by confocal laser scanning microscopy, Fourier‐transformed infrared spectroscopy, and scanning electron microscopy. The data indicate adjustment of polymer concentrations of the jetting solutions to be the determining factors for particle and fiber structures. Subsequent exposure of poly(vinyl cinnamate)‐based particles and fibers to UV light at 254 nm resulted in spatially controlled crosslinking. Treatment of the crosslinked bicompartmental colloids with chloroform produced half‐moon shaped objects. These hemishells exhibited a distinct porous morphology with pore sizes in the range of 70 nm. Based on this novel synthetic approach, Janus‐type particles and fibers can be prepared by EHD co‐jetting and can be selectively photocrosslinked without the need for masks or selective laser writing.

     

Synthesis of polyester nanoparticles in miniemulsion obtained by radical ring-opening of BMDO and their potential as biodegradable drug carriers

5,6-Benzo-2-methylene-1,3-dioxepane (BMDO) is used to obtain degradable polymeric nanoparticles via a statistical free-radical copolymerization with MMA and styrene in direct miniemulsion. The nanoparticles are analyzed by means of IR, NMR, DLS, SEM, and TEM. They show excellent cellular uptake and drug delivery properties. The cellular uptake into HeLa cells of particles resulting from copolymerization of BMDO with styrene is drastically enhanced compared to pure polystyrene. As a model drug system, paclitaxel is incorporated in PBMDO particles and its release and the effect on HeLa cells is studied and compared to commercial drug formulations. It is found that a drug delivery system based on PBMDO shows an excellent pharmacological effect.     

Synthesis and characterisation of highly fluorescent core–shell nanoparticles based on Alexa dyes

Current and future developments in the emerging field of nanobiotechnology are closely linked to the rational design of novel fluorescent nanomaterials, e.g. for biosensing and imaging applications. Here, the synthesis of bright near infrared (NIR)-emissive nanoparticles based on the grafting of silica nanoparticles (SNPs) with 3-aminopropyl triethoxysilane (APTES) followed by covalent attachment of Alexa dyes and their subsequent shielding by an additional silica shell are presented. These nanoparticles were investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM) and fluorescence spectroscopy. TEM studies revealed the monodispersity of the initially prepared and fluorophore-labelled silica particles and the subsequent formation of raspberry-like structures after addition of a silica precursor. Measurements of absolute fluorescence quantum yields of these scattering particle suspensions with an integrating sphere setup demonstrated the influence of dye labelling density-dependent fluorophore aggregation on the signaling behaviour of such nanoparticles.     

Electronic properties of Si surfaces and side reactions during electrochemical grafting of phenyl layers

The electrochemical grafting process of 4-nitrobenzene and 4-methoxybenzene (anisole) from diazonium salt solutions has been investigated in situ by monitoring the current density, the band bending, and the nonradiative surface recombination during grafting at different potentials and different concentrations of the diazonium salt in the solution. Ex situ infrared spectroscopic ellipsometry has been used to inspect the Si surface species before and after the grafting process. The band bending decreases with either increasing concentration of diazonium salt or when the redox potential of the diazonium compound (anisole) is nearer to the competing H+/H2 couple. The surface recombination increases at more cathodic potentials if an electron donor group is present at the phenyl ring (nitrobenzene) and vice versa for the electron acceptor group (anisole). The influence of side reactions can be reduced by use of moderate concentration and moderate or strong cathodic potential, depending on the redox potential of the diazonium compound.     

Chemical analysis in the submillimetre spectral region with a compact solid state system

A new analytical system that uses the rotational signatures of gas phase molecules is described and demonstrated. It uses a solid state source to probe molecular systems in the millimetre and submillimetre wave range, the only region of the electromagnetic spectrum not yet used extensively for analytical purposes. It employs the FAst Scan Submillimetre Spectroscopy Technique (FASSST), which leads to an especially simple system architecture. Among the attributes of the system are generality, sensitivity, 'absolute' specificity, small size, simplicity, and the potential for very low cost. Applications to problems of analytical interest are also discussed.     

In memoriam Heinz Hopf

Ohne Zusammenfassung     

Nanoparticle-encapsulated vis- and NIR-emissive fluorophores with different fluorescence decay kinetics for lifetime multiplexing

Bioanalytical, clinical, and security applications increasingly require simple, efficient, and versatile strategies to measure an ever increasing number of analytes or events in parallel in a broad variety of detection formats as well as in conjunction with chromatographic separation techniques or flow cytometry. An attractive alternative to common optical multiplexing and encoding methods utilizing spectral multiplexing/color encoding and intensity encoding is lifetime multiplexing, which relies on the discrimination between different fluorescent reporters based on their fluorescence decay kinetics. Here, we propose a platform of surface-functionalizable polymeric nanoparticles stained with fluorophores differing in their fluorescence lifetimes as a new multiplexing and encoding approach. Proof-of-concept measurements with different sets of lifetime-encoded polystyrene nanoparticles are presented, obtained via staining of preformed particles with visible (vis)- and near-infrared (NIR)-emissive organic dyes, which display very similar absorption and emission spectra to enable excitation and detection at the same wavelengths, yet sufficiently different fluorescence decay kinetics in suspension, thereby minimizing instrumentation costs. Data analysis was performed with a linear combination approach in the lifetime domain. Our results and first cell experiments with these reporter sets underline the suitability of our multiplexing strategy for the discrimination between and the quantification of different labels. This simple and versatile concept can be extended to all types of fluorophores, thereby expanding the accessible time scale, and can be used, e.g., for the design of labels and targeted probes for fluorescence assays and molecular imaging, cellular imaging studies, and barcoding applications, also in conjunction with spectral and intensity encoding.