ABSTRACT
In this study, through severe reduced-scale braking tests, we investigate the wear and integrity of organic matrix brake pads against gray cast iron (GCI) discs. Two prototype pad materials are designed with the aim of representing a typical non-metal NAO and a low-steel (LS) formulation. The worn surfaces are observed with SEM. The toughness of the pad materials is tested at the raw state and after a heat treatment. During braking, the LS-GCI disc configuration produces heavy wear. The friction parts both keep their macroscopic integrity and wear appears to be homogeneous. The LS pad is mostly covered by a layer of solid oxidized steel. The NAO-GCI disc configuration wears dramatically and cannot reach the end of the test program. The NAO pad suffers many deep cracks. Compacted third body plateaus are scarce and the corresponding disc surface appears to be very heterogeneous. The pad materials both show similar strength at the raw state and similar weakening after heat treatment. However, the NAO material is much more brittle than the LS material in both states, which seems to favor the growth of cracks. The observations of crack faces suggest that long steel fibers in the LS material palliate the brittleness of the matrix, even after heat damage.
ABSTRACT
The first steps towards top-down morphology control in micellar self-assembly are introduced. Kinetically stable micelles are formed from block copolymers (BCPs) using continuous flow techniques by turbulent mixing of water with a THF solution of polymers. In this way, particle shape and size can be altered from spheres to ellipsoids solely via tuning of mixing parameters from a single BCP.
ABSTRACT
Although micelles are commonly used for drug delivery purposes, their long-term fate is often unknown due to photobleaching of the fluorescent labels or the use of toxic materials. Here, we present a metal-free, nontoxic, nonbleaching, fluorescent micelle that can address these shortcomings. A simple, yet versatile, profluorescent micellar system, built from amphiphilic poly(p-phenylenevinylene) (PPV) block copolymers, for use in drug delivery applications is introduced. Polymer micelles made from PPV show excellent stability for up to 1 year and are successfully loaded with anticancer drugs (curcumin or doxorubicin) without requiring introduction of physical or chemical cross-links. The micelles are taken up efficiently by the cells, which triggers disassembly, releasing the encapsulated material. Disassembly of the micelles and drug release is conveniently monitored as fluorescence of the single polymer chains appear, which enables not only to monitor the release of the payload, but in principle also the fate of the polymer over longer periods of time.
Subject(s)
Antineoplastic Agents/pharmacology , Drug Delivery Systems , Fluorescent Dyes/chemistry , Micelles , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/pathology , Polymers/chemistry , Polyvinyls/chemistry , Antineoplastic Agents/administration & dosage , Antineoplastic Agents/chemistry , Cell Survival/drug effects , Curcumin/administration & dosage , Curcumin/chemistry , Curcumin/pharmacology , Doxorubicin/administration & dosage , Doxorubicin/chemistry , Doxorubicin/pharmacology , Drug Carriers/chemistry , Humans , Molecular Imaging/methods , Tumor Cells, CulturedABSTRACT
Conjugated polymers have attracted significant interest in the bioimaging field due to their excellent optical properties and biocompatibility. Tailor-made poly(p-phenylenevinylene) (PPV) conjugated polymer nanoparticles (NPs) are in here described. Two different nanoparticle systems using poly[2-methoxy-5-(3',7'-dimethoxyoctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and a functional statistical copolymer 2-(5'-methoxycarbonylpentyloxy)-5-methoxy-1,4-phenylenevinylene (CPM-MDMO-PPV), containing ester groups on the alkoxy side chains, were synthesized by combining miniemulsion and solvent evaporation processes. The hydrolysis of ester groups into carboxylic acid groups on the CPM-MDMO-PPV NPs surface allows for biomolecule conjugation. The NPs exhibited excellent optical properties with a high fluorescent brightness and photostability. The NPs were in vitro tested as potential fluorescent nanoprobes for studying cell populations within the central nervous system. The cell studies demonstrated biocompatibility and surface charge dependent cellular uptake of the NPs. This study highlights that PPV-derivative based particles are a promising bioimaging probe and can cater potential applications in the field of nanomedicine.
Subject(s)
Astrocytes/metabolism , Cell Communication , Endothelium, Vascular/metabolism , Microglia/metabolism , Molecular Imaging/methods , Nanoparticles/chemistry , Polymers/chemistry , Astrocytes/cytology , Endothelium, Vascular/cytology , Fluorescent Dyes , Humans , Microglia/cytology , Nanopores , Surface PropertiesABSTRACT
In this contribution, we present the silica microencapsulation of hydrophilic compounds by templating Pickering emulsion droplets without contamination of the dispersed phase by either the catalyst or the silica precursor. This is accomplished by the use of an amphiphilic catalyst, which situates around the Pickering emulsion droplets and directs the reaction to the interface. Both the silica precursor and the amphiphilic catalyst are soluble in the oil phase and therefore initially do not reside in the hydrophilic microcapsule templates. The thickness of the capsules can be tuned by adjusting the amount of precursor. Thus, the permeability of the capsules can in principle be controlled. The possibility of tuning the permeability holds promise for a variety of applications of the microcapsules. Because of the straightforward synthesis method and minimized mixing of the core with contaminants, the technique is potentially suitable for the encapsulation of delicate matter including live organisms, drugs, enzymes or bacteria.
