Structured multistimuli‐responsive functional polymer surfaces obtained by interfacial diffusion of amphiphilic block copolymers

Herein, we report the preparation of structured multistimuli‐responsive surfaces able to change reversibly both their chemical composition depending on the environment and their surface behavior by varying either/both the pH or/and the temperature. For that purpose, we took advantage of the surface segregation in homopolymer/diblock copolymer blends, composed of either polystyrene‐block‐poly(N,N′‐dimethylaminoethylmethacrylate) (PS‐b‐PDMAEMA) or polystyrene‐block‐poly (N,N′‐diethylaminoethylmethacrylate) (PS‐b‐PDEAEMA) and high molecular weight polystyrene used as a matrix. The variations of the surface composition as a function of the environment of exposure (air or water vapor) was investigated were investigated by XPS and contact angle measurements. The water‐annealed surfaces contain PDMAEMA or PDEAEMA at the surface and are additionally able to respond both to pH and temperature as demonstrated by the Wilhelmy technique. Both PDMAEMA and PDEAEMA can switch from a hydrophilic state to a collapsed hydrophobic state increasing the temperature above the LCST. More interestingly, as a result of the microphase separation of the block copolymers at the interface, the surfaces of the blends exhibit structuration. Thus, either micellar structures or “donut‐like” morphologies were obtained by using THF or toluene, respectively, as solvent. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1952–1961, 2010     

Synthesis of comb polymers via grafting‐onto macromolecules bearing pendant diene groups via the hetero‐Diels‐Alder‐RAFT click concept

Comb polymers were synthesized by the “grafting‐onto” method via a combination of Reversible Addition‐Fragmentation Chain Transfer (RAFT) polymerization and the hetero‐Diels‐Alder (HDA) cycloaddition. The HDA reactive monomer trans, trans‐hexa‐2,4‐dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Crosslinking was minimized by decreasing the monomer concentration—whilst keeping monomer to polymer conversions low—resulting in reactive backbones with on average one reactive pendant diene groups for 10 styrene units. The HDA cycloaddition was performed between the diene functions of the copolymer and a poly(n‐butyl acrylate) (PnBA) prepared via RAFT polymerization with pyridin‐2‐yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 °C and the grafting yield varies from 75% to 100%, depending on the number average molecular weight of the PnBA (3500 g mol^?1 < M_n < 13,000 g mol^?1) grafted chain and the reaction stoichiometry. The molecular weights of the grafted block copolymers range from 19,000 g mol^?1 to 58,000 g mol^?1 with polydispersities close to 1.25. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1773–1781, 2010     

pH responsive surfaces with nanoscale topography

We report the preparation of nanostructured adaptive polymer surfaces by diffusion of an amphihilic block copolymer toward the interface. The surface segregation of a diblock copolymer, polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA), occurred when blended with high molecular weight polystyrene employed as a matrix. On annealing, the polymer surfaces changed both the chemical composition and the hydrophilicity depending on the environment and pH, respectively. By exposure to either water vapor or air, the surface wettability varied between hydrophilic and hydrophobic. In addition, surface enrichment on diblock copolymer by water vapor annealing led to self‐assembly occurring at the interface. Hence, nanostructured domains can be observed by AFM in liquid media. Moreover, the PAA segments placed at the interface respond to pH and can switch from an extended hydrophilic state at basic pH values to a collapsed hydrophobic state in acidic media. Accordingly, the surface morphology changed from swelled micelles to nanometer size holes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2982–2990, 2010     

Synthesis and Immunostimulating Activity of A Thioglycolipopeptide Glycomimetic As A Potential Anticancer Vaccine Derived From Tn Antigen

ABSTRACT

The Tn epitope is one of the tumor associated O-linked cell surface glycopeptides. It is expressed in over 70% of human epithelial cancers such as lung, colon, stomach and breast carcinomas. The glycosidic linkage of the Tn antigen, between N-acetylgalactosamine and serine or threonine, can be cleaved either chemically or enzymatically in the presence of glycosidases. The latter case is particularly a problem in vivo. Therefore, it would be of great interest to obtain a metabolically stable analogue of the Tn antigen that maintains or improves the immunogenic activity of the latter. The purpose of this work was to synthesize a totally synthetic vaccine using a chemically and metabolically stable glycomimetic of the Tn antigen in which the interglycosidic oxygen was replaced by a sulphur atom (S-Tn). The S-Tn thioglycopeptide was linked to the P₃CS immunoadjuvant to obtain the potential S-Tn vaccine. Moreover, we synthesized the natural Tn antigen and derivatized it similarly to obtain the Tn vaccine. Last, we evaluated the immunostimulating activity of the two synthetic potential vaccines in vitro using cultured mouse splenocytes. The S-Tn construct showed immunostimulating activity comparable, in terms of maximal response, to the Tn analogue. Moreover, due to its higher stability the S-Tn construct reached its maximal effect at lower doses compared to the Tn analogue.     

Going beyond the borders: pyrrolo[3,2-b]pyrroles with deep red emission

A two-step route to strongly absorbing and efficiently orange to deep red fluorescent, doubly B/N-doped, ladder-type pyrrolo[3,2-b]pyrroles has been developed. We synthesize and study a series of derivatives of these four-coordinate boron-containing, nominally quadrupolar materials, which mostly exhibit one-photon absorption in the 500–600 nm range with the peak molar extinction coefficients reaching 150 000, and emission in the 520–670 nm range with the fluorescence quantum yields reaching 0.90. Within the family of these ultrastable dyes even small structural changes lead to significant variations of the photophysical properties, in some cases attributed to reversal of energy ordering of alternate-parity excited electronic states. Effective preservation of ground-state inversion symmetry was evidenced by very weak two-photon absorption (2PA) at excitation wavelengths corresponding to the lowest-energy, strongly one-photon allowed purely electronic transition. π-Expanded derivatives and those possessing electron-donating groups showed the most red-shifted absorption- and emission spectra, while displaying remarkably high peak 2PA cross-section (σ_2PA) values reaching ∼2400 GM at around 760 nm, corresponding to a two-photon allowed higher-energy excited state. At the same time, derivatives lacking π-expansion were found to have a relatively weak 2PA peak centered at ca. 800–900 nm with the maximum σ_2PA ∼50–250 GM. Our findings are augmented by theoretical calculations performed using TD-DFT method, which reproduce the main experimental trends, including the 2PA, in a nearly quantitative manner. Electrochemical studies revealed that the HOMO of the new dyes is located at ca. −5.35 eV making them relatively electron rich in spite of the presence of two B⁻–N⁺ dative bonds. These dyes undergo a fully reversible first oxidation, located on the diphenylpyrrolo[3,2-b]pyrrole core, directly to the di(radical cation) stage.

Ladder-type heterocycles encompassing two B⁻–N⁺ dative bonds possess intense green to red emission, large 2PA cross-sections and superb photostability.     

Time-Delay for Two-Compartment Models Used for Study of Enterohepatic Circulation of Drugs

A two-component model with time lag was proposed to describe pharmacokinetics of drugs subject to enterohepatic circulation. An analytic expansion of the amount of drug, at any time, in the central compartment after an intravenous bolus, or an oral intake, or a constant infusion, from a zero or nonzero equilibrium is given. By computer simulations, plasma level profiles are obtained and lead to rebounds and secondary peaks, according to experimental evidences.     

Performance of fully variable demand assignment SS/TDMA satellite systems

Fully variable demand assignment in a SS/TDMA satellite system requires frequent burst time plan changes with reconfiguration of the on-board switch matrix state sequence. The burst managment presented in this paper assumes that bursts are not reconfigurated into new bursts during such burst time plan changes but merely shifted in time. The performance of this burst management procedure as obtained from simulations over three different networks is reported in terms of throughput gains, required signalling capacity and time required to change burst time plan.     

Photocrosslinking of elastomer systems—III Ultraviolet light induced reactions in EPDM and EPR blended with or modified by grafting of derivatives of benzophenone

Photocrosslinking experiments were performed in elastomeric polymer films (EPR or EPDM) that either contained benzophenone or some of its derivatives, or had been previously modified (EPDM) by grafting of benzophenone. This latter modification was performed by a series of Friedel-Crafts reactions. The resulting materials were characterized by i.r. and u.v. spectroscopy in conjunction with physical property measurements. The results allowed relationships between the properties of the photosensitizers in their excited states and their efficiency in the crosslinking processes to be established. The results suggest that each coupled polymer-photoinitiator exhibits a particular behaviour. Thus it appeared that, in the presence of oxygen, the hexadiene branches of the terpolymer can undergo various types of reactions. Moreover, the grafting of the photosensitizer onto the elastomer backbone was shown to enhance considerably the crosslinking reaction. It is possible to conclude that oxygen plays a substantial role in the photocrosslinking. Indeed it always enhances crosslink formation. It can be assumed that the photooxidation of the polymer backbone yields alkoxy and hydroperoxy radicals which can act as crosslink sites.     

Automating proteome analysis: improvements in throughput, quality and accuracy of protein identification by peptide mass fingerprinting

The use of robots has major effects on maximizing the proteomic workflow required in an increasing number of high-throughput projects and on increasing the quality of the data. In peptide mass finger printing (PMF), automation of steps downstream of two-dimensional gel electrophoresis is essential. To achieve this goal, the workflow must be fluid. We have developed tools using macros written in Microsoft Excel and Word to complete the automation of our platform. Additionally, because sample preparation is crucial for identification of proteins by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, we optimized a sandwich method usable by any robot for spotting digests on a MALDI target. This procedure enables further efficient automated washing steps directly on the MALDI target. The success rate of PMF identification was evaluated for the automated sandwich method, and for the dried-droplet method implemented on the robot as recommended by the manufacturer. Of the two methods, the sandwich method achieved the highest identification success rate and sequence coverage of proteins.     

Hydroperoxides as intermediates responsible for wavelength effects in photooxidation reactions

A quantitative study of a model elastomer was performed to gain a deeper insight into photooxidation processes. Since the twofold role of hydroperoxides as excited sensitizer quenchers, and radical initiators has been amply demonstrated, we described the mechanism of energy transfer to repulsive excited states of these substances and quantitatively determined their distribution in the polymeric material, according to their reactivity. In addition, two irradiation wavelengths (λ = 254 nm and λ = 313 nm) were used to demonstrate that behavior of hydroperoxides depends on the nature and the concentration of excited chromophoric groups and accounts for the macroscopic wavelength effect usually observed in the photooxidation of polymers.