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

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

Insulin/Poly(ethylene glycol)-block-poly(L-lysine) Complexes: Physicochemical Properties and Protein Encapsulation

Insulin (INS) was encapsulated into complexes with poly(ethylene glycol)-block poly(L-lysine) (PEG-b-PLys), which is a polypeptide-based block copolymer (a neutral-cationic block polyelectrolyte). These macromolecules can encapsulate INS molecules in aqueous conditions via electrostatic interactions. Light scattering techniques are used in order to examine the complexation process of the hybrid nanoparticles in a gamut of buffers, as a function of protein concnetration. The physicochemical and structural characteristics of the complexes depend on the ionic strength of the aqueous medium, while the concentration of PEG-b-PLys was constant through the series of solutions. As INS concentration increased each polyelectrolyte chain interacts with an increasing number of INS molecules, the degree of charge neutralization becomes higher and the size distribution of the complexes decreased also, especially at the highest ionic strength. The size/structure of complexes diluted in biological medium indicated that the copolymer imparts stealth properties and colloidal and biological stability to the complexes, which could in turn affect the clearance properties in vivo. Therefore, these studies could be a rational roadmap for designing the optimum complexes/effective nanocarriers for proteins and peptides

Complexation of Lysozyme with Adsorbed PtBS-b-SCPI Block Polyelectrolyte Micelles on Silver Surface

We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene)-bsodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the surface of silver. The adsorption kinetics are monitored by surface plasmon resonance and the surface morphology by atomic force microscopy. The micellar adsorption kinetics is dictated by two processes and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein binding and low resistance in loading. When the micellar adsorbed amount is high the situation is inversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface

One-step covalent hydrophobic/hydrophilic functionalization of chemically exfoliated molybdenum disulfide nanosheets with RAFT derived polymers

The covalent functionalization of chemically exfoliated molybdenum disulfide (ce-MoS2) with hydrophobic poly(methyl methacrylate) and hydrophilic poly(acrylic acid) polymers, in a single-step without additives, is presented. The nature of chemical modification and the impact on the structure of ce-MoS2 were spectroscopically investigated. Complexation of Eu3+ was accomplished on grafted polycarboxylate chains on MoS2