Block polyelectrolyte micelles/protein mixed nanostructures in aqueous media

The interactions between a globular protein, hen egg white lysozyme (HEWL), and star-like block polyelectrolyte micelles formed by the self-assembly of a poly(tertbutylstyrene)-b-poly(sodium(sulfamate-carboxylate)isoprene) (PtBS-SCPI) amphiphilic diblock copolymer were studied in aqueous solutions. Due to the opposite charges present in HEWL (positive charges) and on the SCPI polyelectrolyte coronas of the block copolymer micelles (negative charges), nanostructured hierarchical complexes are formed at neutral pH and low ionic strength. Structure and properties of the complexes were investigated by means of dynamic, static and electrophoretic light scattering, as well as atomic force microscopy. The solution behaviour, structure and effective charge of the formed nanoscale complexes proved to be dependent on the ratio of the two components. Presumably block polyelectrolyte micelles with a PtBS core and a SCPI corona decorated with HEWL molecules are initially formed. Moreover, the degree of charge neutralization caused by complexation determines the conformation and solubility of the complexes. Complexation of the macromolecular components at higher solution ionic strengths led to complexes of lower mass and nearly constant size. Such behavior may be correlated to the polyelectrolyte nature of the components. The structural investigation of the complexed protein by fluorescence and infrared spectroscopy revealed no signs of HEWL denaturation upon complexation

Amphiphilic block copolymers by a combination of anionic polymerization and selective post-polymerization functionalization

AbstractAnionic polymerization is the oldest known living/controlled polymerization methodology that leads to well defined macromolecules. It has been also used, with considerable success, for the synthesis of amphiphilic block copolymers (AmBC), a class of functional copolymers having interesting self-assembling properties and high potential for applications in various technological fields. The use of mild and effective post-polymerization functionalization/chemical modification reactions on block copolymers has substantially increased the synthetic capabilities of anionic polymerization methodologies, toward the creation of a variety of AmBC. In this feature article we review work done on these directions in the last ten years. Some perspectives and future work on this particular field of polymer science are also discussed

Photocatalytic applications with CdS•block copolymer/exfoliated graphene nanoensembles: Hydrogen generation and degradation of Rhodamine B

Amphiphilic block copolymer poly (isoprene-b-acrylic acid) (PI-b-PAA) stabilized exfoliated graphene in water and allowed the immobilization of semiconductor CdS nanoparticles forming CdS•PI-b-PAA/graphene. Characterization with HR-TEM and EDX justified the success of preparation and revealed the presence of spherical CdS. Moreover, UV-Vis and photoluminescence assays suggested that electronic interactions within CdS•PI-b-PAA/graphene exist as evidenced by the significant quenching of the characteristic emission of CdS by exfoliated graphene. Photoillumination of CdS•PI-b-PAA/graphene, in the presence of ammonium formate as quencher for the photogenerated holes, resulted on the generation of hydrogen by water splitting, monitored by the reduction of 4-nitroaniline to benzene-1,4-diamine (> 80±4% at 20 min; 100% at 24 min), much faster and efficient as compared when reference CdS•PI-b-PAA was used as photocatalyst (< 30±3% at 20 min; 100% at 240 min). Moreover, Rhodamine B was photocatalytically degraded by CdS•PI-b-PAA/graphene, with fast kinetics under visible light illumination in the presence of air. The enhancement of both photocatalytic processes by CdS•PI-b-PAA/graphene was rationalized in terms of effective separation of holes–electrons, contrary to reference CdS•PI-b-PAA, in which rapid recombination of the hole–electron pair is inevitable due to the absence of exfoliated graphene as suitable electron acceptor

Advanced nanocarriers for an antitumor peptide

In this work, tigapotide (PCK3145) was incorporated into novel nanocarriers based on polymeric, lipidic and dendrimeric components, in order to maximize the advantages of the drug delivery process and possibly its biological properties. PCK3145 was incorporated into lipidic nanocarriers composed of Eggphosphatidylcholine (EggPC) and dipalmytoylphosphatidylcholine (DPPC) (EggPC:PCK3145 and DPPC:PCK3145, 9:0.2 molar ratio), into cationic liposomes composed of EggPC:SA:PCK3145 and DPPC:SA:PCK3145 (9:1:0.2 molar ratio) into complexes with the block polyelectrolyte (quaternized poly[3,5bis(dimethylaminomethylene)hydroxystyrene]-b-poly(ethylene oxide) (QNPHOSEO) and finally into dendrimeric structures (i.e. PAMAM G4) . Light scattering techniques are used in order to examine the size, the size distribution and the z-potential of the nanocarriers in aqueous and biological media. Fluorescence spectroscopy was utilized in an attempt to extract information on the internal nanostructure and microenvironment of polyelectrolyte/PCK3145 aggregates. Therefore, these studies could be a rational roadmap for producing various effective nanocarriers in order to ameliorate the pharmacokinetic behavior and safety issues of antitumor and anticancer biomolecules

Complexation of cationic-neutral block polyelectrolyte with insulin and in vitro release studies

Insulin (INS) was incorporated into complexes with the block polyelectrolyte quaternized poly[3,5-bis(dimethylaminomethylene)hydroxystyrene]-b-poly(ethyleneoxide) (QNPHOSEO), which is a cationic-neutral block polyelectrolyte. Light scattering techniques are used in order to examine the size, the size distribution and the ζ-potential of the nanocarriers in aqueous and biological media, which are found to depend on the ratio of the components and the physicochemical parameters during and after complex preparation. Circular dichroism and infrared spectroscopy, employed to investigate the structure of the complexed INS, show no alteration of protein structure after complexation. In vitro release profiles of the entrapped protein are found to depend on the ratio of the components and the solution conditions used during preparation of the complexes

Amphiphilic diblock copolymer based multi-agent photonic sensing scheme

Efficient functionalization of polymer optical fibers’ (POF) surface by a novel block copolymer material towards the development of low cost multi-agent sensors is presented. The employed poly(styrene sulfonate-b-tert-butylstyrene) diblock copolymer (SPS-b-PtBS) possesses two blocks of distinctively different polarity and charge, the hydrophilic SPS which is sensitive to polar substances and the hydrophobic PtBS which is sensitive to organic solvents. The coexistence of two different blocks allows for the detection of a wide variety of agents, ranging from ammonia, and organic solvents, to biomolecules like lysozyme, at room temperature as opposed to alternative usually more complicated techniques, all with the sole use of one sensing medium. Copolymers' high glass transition temperature enables the formation of stable and environmentally robust overlayers. The sensing performance of the material is evaluated experimentally on the customizable platform of polymer optical fibers, demonstrating fast response, high operational reversibility and also reusability in successively different testing agents

Assessment of block and random copolymer overlayers on polymer optical fibers towards protein detection through electrostatic interaction

A simple fiber optic based scheme for the selective detection of proteins, based on surface electrostatic interactions, is presented. The implementation of this method is conducted by using a modified polymer optical fiber's (POF) surface and thin overlayers of properly designed sensitive copolymer materials with predesigned molecular characteristics. Block poly(styrene-b-2vinylpyridine) (PS-b-P2VP) and random poly(styrene-r-2vinylpyridine) (PS-r-P2VP) copolymers of the same monomers and similar molecular weights, were modified and used as sensing materials. This configuration proved to be efficient concerning the fast detection of charged proteins, and also the efficient discrimination of differently charged proteins such as lysozyme (LYS) and bovine serum albumin (BSA). Results on the sensing performance of block and random copolymers are also discussed drawing conclusion on their efficiency given their considerable different fabrication cost