A multi-channel bioluminescent bacterial biosensor for the on-line detection of metals and toxicity. Part II: technical development and proof of concept of the biosensor

This research study deals with the on-line detection of heavy metals and toxicity within the context of environmental pollution monitoring. It describes the construction and the proof of concept of a multi-channel bioluminescent bacterial biosensor in immobilized phase: Lumisens3. This new versatile device, designed for the non-stop analysis of water pollution, enables the insertion of any bioluminescent strains (inducible or constitutive), immobilized in a multi-well removable card. The technical design of Lumisens3 has benefited from both a classical and a robust approach and includes four main parts: (1) a dedicated removable card contains 64 wells, 3 mm in depth, arranged in eight grooves within which bacteria are immobilized, (2) this card is incubated on a Pelletier block with a CCD cooled camera on top for bioluminescence monitoring, (3) a fluidic network feeds the card with the sample to be analyzed and finally (4) a dedicated computer interface, BIOLUX 1.0, controls all the elements of the biosensor, allowing it to operate autonomously. The proof of concept of this biosensor was performed using a set of four bioluminescent bacteria (Escherichia coli DH1 pBzntlux, pBarslux, pBcoplux, and E. coli XL1 pBfiluxCDABE) in the on-line detection of CdCl₂ 0.5 μM and As₂O₃ 5 μM from an influent. When considering metals individually, the “fingerprints” from the biosensor were as expected. However, when metals were mixed together, cross reaction and synergistic effects were detected. This biosensor allowed us to demonstrate the simultaneous on-line cross detection of one or several heavy metals as well as the measurement of the overall toxicity of the sample.     

Modification of RAFT‐polymers via thiol‐ene reactions: A general route to functional polymers and new architectures

An investigation into the aminolysis of ω‐end groups of RAFT‐polymers and simultaneous thiol‐ene reactions with ene‐bearing compounds is described. Three different polymers, P(MMA), P(HPMA), and P(NIPAAm), with low PDIs were synthesized using dithiobenzoate and trithiocarbonate RAFT agents. P(NIPAAm) synthesized with trithiocarbonate RAFT agent and P(HPMA) synthesized with dithiobenzoate RAFT agent were both functionalized with a methacrylate‐modified mannose and a maleimide‐modified biotin via one‐pot simultaneous aminolysis and thiol‐ene reactions with product yields above 85%. The presence of ene‐compounds during aminolysis was shown to prevent the formation of disulfide interchain crosslinking. Using the same approach, P(MMA), P(HPMA), and P(NIPAAm) were converted to (meth)acrylate macromonomers with high yields (>80%). In the case of P(MMA), the simultaneous aminolysis and thiol‐ene addition prevented any intrachain side reactions, i.e., thiolactone formation. New architectures such as graft and block copolymers were successfully generated from the macromonomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3773–3794, 2009     

Biosynthetic studies on the azinomycins: the pathway to the naphthoate fragment

Isotopically labelled intermediates in a proposed biosynthesis of the naphthoate fragment of azinomycin B have been made and successfully incorporated by the azinomycin producing organism.     

Non‐Aqueous Sol–Gel Synthesis of Ultra Small Persistent Luminescence Nanoparticles for Near‐Infrared In Vivo Imaging

Ultra‐small ZnGa₂O₄:Cr³⁺ nanoparticles (6 nm) that exhibit near‐infrared (NIR) persistent luminescence properties are synthesized by using a non‐aqueous sol–gel method assisted by microwave irradiation. The nanoparticles are pegylated, leading to highly stable dispersions under physiological conditions. Preliminary in vivo studies show the high potential for these ultra‐small ZnGa₂O₄:Cr³⁺ nanoparticles to be used as in vivo optical nanotools as they emit without the need for in situ excitation and, thus, avoid the autofluorescence of tissues.     

A Versatile 3D and 4D Printing System through Photocontrolled RAFT Polymerization

Reversible addition‐fragmentation chain‐transfer (RAFT) polymerization is a valuable tool for synthesizing macromolecules with controlled topologies and diverse chemical functionalities. However, the application of RAFT polymerization to additive‐manufacturing processes has been prevented due to the slow polymerization rates of typical systems. In this work, we developed and optimized a rapid visible (green) light mediated RAFT polymerization process and applied it to an open‐air 3D printing system. The reaction components are non‐toxic, metal free and environmentally friendly, which tailors these systems toward biomaterial fabrication. The inclusion of RAFT agent in the photosensitive resin provided control over the mechanical properties of 3D printed materials and allowed these materials to be post‐functionalized after 3D printing. Additionally, photoinduced spatiotemporal control of the network structure provided a one‐pass approach to 4D printed materials. This RAFT‐mediated 3D and 4D printing process should provide access to a range of new functional and stimuli‐responsive materials.     

Reorganization energy and pre-exponential factor from temperature-dependent experiments in electron transfer reactions. A typical example: the reduction of tert-nitrobutane

The electrochemical one-electron reduction of tert-nitrobutane in N,N'-dimethylformamide is a typical reaction, which has been shown to follow the quadratic model of outersphere electron transfer. The variation of the standard rate constant with temperature allows a separate determination of the reorganization energy and of the pre-exponential factor. The value found for the former is in agreement with independent estimates of the solvent and intramolecular reorganization energies. The value of the latter, significantly larger than the collision frequency, implies that the reaction starts to take place before close contact with the electrode surface.     

Impact of crystallinity of poly(lactide) on helium and oxygen barrier properties

The helium and oxygen gas barrier properties of poly(lactide) were investigated as a function of stereochemistry and crystallinity degree. Poly(l-lactide) and poly(d,l-lactide) films were obtained by extrusion and thermally cold crystallized in either α′- or α-crystalline form with increasing crystallinity degree. Annealing of the films at low temperatures yielded to α′-crystals as well as the creation of a rigid amorphous fraction in the amorphous phase. Unexpectedly, the quantity of the rigid amorphous fraction was highest in poly(l-lactide) crystallized under α′-form. Unexpectedly, the gas permeability increased with increasing quantity of α′-crystals in poly(l-lactide) and remained constant with increasing quantity of α′-crystals in poly(d,l-lactide). A gain in gas barrier properties was obtained upon crystallization at higher temperatures yielding α-crystals. The analysis of the oxygen transport parameters, in particular the diffusion and the solubility coefficient showed that the diffusion was accelerated upon crystallization, while the solubility coefficient decreased in an expected manner which led to conclude that it remained constant in the amorphous phase. The acceleration of the diffusion seems to be correlated to the occurrence of the rigid amorphous fraction, which holds larger free volume. To conclude, for optimization of poly(lactide) gas barrier properties by focussing on the decrease of the diffusion coefficient it can be suggested to work with poly(d,l-lactide) and to aim a crystallization in α-form avoiding the formation of a rigid amorphous fraction.     

From thiourea to bicyclic structures: an original route to imidazo[2,1-b]thiazoles, 5H-thiazolo[3,2-a]pyrimidines, 7H-imidazo[2,1-b][1,3]thiazines,and 2H,6H-pyrimido[2,1-b][1,3]thiazines

We report an example of an efficient regioselective synthesis of biheterocyclic compounds using thiourea as starting material. In fact, N,N'-bis(dimethylaminomethylene)thiourea (1), easily prepared by double condensation of N,N-dimethylformamide dimethyl acetal with thiourea, can be reacted with haloketones or acrylic dienophiles to give thiazolic (2) and thiazinic (3) diazadienes, respectively, themselves undergoing cyclization reactions to yield imidazo[2,1-b]thiazoles, 5H-thiazolo[3,2-a]pyrimidines, 7H-imidazo[2,1-b][1,3]thiazines, and 2H,6H-pyrimido[2,1-b][1,3]thiazines without any regioisomeric ambiguity. This straightforward route represents an original and unambiguously regioselective pathway to these valuable heterocycles.