Comparative sensitivity of microvascular endothelial cells, fibroblasts and tumor cells after in vitro photodynamic therapy with meso-tetra-hydroxyphenyl-chlorin

The phototoxic effect of meso-tetra-hydroxyphenyl-chlorin (mTHPC)-mediated photodynamic therapy (PDT) on human microvascular endothelial cells (hMVEC) was compared with that on human fibroblasts (BCT-27) and two human tumor cell lines (HMESO-1 and HNXOE). To examine the relationship between intrinsic phototoxicity and intracellular mTHPC content, we expressed cell survival as a function of cellular fluorescence. On the basis of total cell fluorescence, HNXOE tumor cells were the most sensitive and BCT-27 fibroblasts the most resistant, but these differences disappeared after correcting for cell volume. Endothelial cells were not intrinsically more sensitive to mTHPC-PDT than tumor cells or fibroblasts. Uptake of mTHPC in hMVEC increased linearly to at least 48 h, whereas drug uptake in the other cell lines reached a maximum by 24 h. No difference in drug uptake was seen between the cell lines during the first 24 h, but by 48 h hMVEC had a 1.8- to 2.8-fold higher uptake than other cell lines. Endothelial cells showed a rapid apoptotic response after mTHPC-mediated PDT, whereas similar protocols gave a delayed apoptotic or necrotic like response in HNXOE. We conclude that endothelial cells are not intrinsically more sensitive than other cell types to mTHPC-mediated PDT but that continued drug uptake beyond 24 h may lead to higher intracellular drug levels and increased photosensitivity under certain conditions.     

Biocompatible polystyrenes containing pendant tetra(ethylene glycol) and phosphorylcholine groups

The synthesis and characterization of styrene‐based polymers and copolymers containing pendant tetra(ethylene glycol) and phosphorylcholine groups is reported. These polymers are obtained via radical polymerization reactions using α,α′‐azobis(isobutyronitrile) as the initiator, and are developed as protective biocompatible coatings for implantable biosensors. Cell morphology studies show that none of the synthesized polymers and copolymers are toxic, and that the rate of cell growth can be tuned by changing the monomer composition. The presence of tetra(ethylene glycol) groups in the coatings lowers the protein adsorption, thereby influencing the rate of cell growth. An equally profound effect is observed when a low percentage of phosphorylcholine groups is present in the polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 468–474, 2001     

Comparison of agent-based scheduling to look-ahead heuristics for real-time transportation problems

We consider the real-time scheduling of full truckload transportation orders with time windows that arrive during schedule execution. Because a fast scheduling method is required, look-ahead heuristics are traditionally used to solve these kinds of problems. As an alternative, we introduce an agent-based approach where intelligent vehicle agents schedule their own routes. They interact with job agents, who strive for minimum transportation costs, using a Vickrey auction for each incoming order. This approach offers several advantages: it is fast, requires relatively little information and facilitates easy schedule adjustments in reaction to information updates. We compare the agent-based approach to more traditional hierarchical heuristics in an extensive simulation experiment. We find that a properly designed multi-agent approach performs as good as or even better than traditional methods. Particularly, the multi-agent approach yields less empty miles and a more stable service level.     

Twin-hollow-core optical fibres

Twin-hollow-core microstructured optical fibres have been fabricated and characterised for the first time. The fibre cladding structure results in guidance by the inhibited coupling mechanism, in which there is a low overlap between the core modes and surrounding structure. This results in minimal interaction between the modes of each core in the transmission bands of the fibre and hence minimal coupling between the cores. It is shown that light is able to couple between the cores via coupling to cladding struts in the high loss wavelength bands.     

Chalcogenide glass photonic crystals

All-optical switching devices are based on a material possessing a nonlinear optical response, enabling light to control light, and are enjoying renewed interest. Photonic crystals are a promising platform for realizing compact all-optical switches operating at very low power and integrated on an optical integrated circuit. In this review, we show that by making photonic crystals from a highly nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the fabrication and testing of two-dimensional Ge₃₃As₁₂ Se₅₅ chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to post-tune the devices using the material photosensitivity. In one proposal we hope to introduce a double-heterostructure microcavity using the photosensitivity alone.     

A New Paramagnetic Pd(dmit)2 Salt: Tris(2,2′-Bipyridine)Nickel(II) Bis(1,3-Dithiole-2-Thione-4,5-Dithiolato)Palladate(II) Mono-Acetonitrile; [Ni(bpy)3][Pd(dmit)2]·CH3CN

Combination of the [Ni(bpy)₃]²⁺ cation complex and the [Pd(dmit)₂]⁻ anion (dmit=C₃S₅²⁻=1,3-dithiole-2thione-4,5-dithiolate) has resulted in the paramagnetic [Ni(bpy)₃][Pd(dmit)₂]·CH₃CN compound, a suitable precursor for a molecular magnetic conductor. Its crystal structure consists of a Pd(dmit)₂ anion arrangement that is quite different from segregated stack layers often found for M(dmit)₂−based compounds. The reduction of the [Pd(dmit)₂]^- to the 2− charged anion in the title compound most probably is the result of a charge disproportionation between Pd(dmit)₂ anions.     

Hydrogen Bonding Directed Supramolecular Polymerisation of Oligo(Phenylene‐Ethynylene)s: Cooperative Mechanism,Core Symmetry Effect and Chiral Amplification

The design of supramolecular motifs with tuneable stability and adjustable supramolecular polymerisation mechanisms is of crucial importance to precisely control the properties of supramolecular assemblies. This report focuses on constructing π‐conjugated oligo(phenylene ethynylene) (OPE)‐based one‐dimensional helical supramolecular polymers that show a cooperative growth mechanism. Thus, a novel set of discotic molecules comprising a rigid OPE core, three amide groups, and peripheral solubilising wedge groups featuring C₃ and C₂ core symmetry was designed and synthesised. All of the discotic molecules are crystalline compounds and lack a columnar mesophase in the solid state. In dilute methylcyclohexane solution, one‐dimensional supramolecular polymers are formed stabilised by threefold intermolecular hydrogen bonding and π–π interactions, as evidenced by ¹H NMR measurements. Small‐angle X‐ray and light scattering measurements reveal significant size differences between the columnar aggregates of C₃‐ and C₂‐symmetrical discotics, that is, the core symmetry strongly influences the nature of the supramolecular polymerisation process. Temperature‐dependent CD measurements show a highly cooperative polymerisation process for the C₃‐symmetrical discotics. In contrast, the self‐assembly of C₂‐symmetrical discotics shows a smaller enthalpy release upon aggregation and decreased cooperativity. In all cases, the peripheral stereogenic centres induce a preferred handedness in the columnar helical aggregates. Moreover, one stereogenic centre suffices to fully bias the helicity in the C₂‐symmetrical discotics. Finally, chiral amplification studies with the C₃‐symmetrical discotics were performed by mixing chiral and achiral discotics (sergeants‐and‐soldiers experiment) and discotics of opposite chirality (majority‐rules experiment). The results demonstrate a very strong sergeants‐and‐soldiers effect and a rather weak majority‐rules effect.