A negatively charged poly(para-phenyleneethynylene) (PPE) forms electrostatic complexes with four positively charged antimicrobial peptides (AMP). The AMPs partially quench the fluorescence of the PPE and discriminate fourteen different bacteria in water and in human urine by pattern-based fluorescence recognition; the AMP-PPE complexes bind differentially to the components of bacterial surfaces. The bacterial species and strains form clusters according to staining properties (Gram-positive and Gram-negative) or genetic similarity (genus, species, and strain). The identification and data treatment is performed by pattern evaluation with linear discriminant analysis (LDA) of the collected fluorescence intensity data.
We describe poly(aryleneethynylene)s (PAE) as powerful sensor cores. We discuss concepts (super quenching, molecular wire effect, multivalency) that were developed using PAEs and also the relationship that connects side chain structure (polar, polyelectrolyte, etc., number of ionic groups per repeat, position) and optical properties such as quantum yields. In the second part of the review we discuss applications of PAEs in their interaction with sensor targets; metal cations, fluoride and other anions, explosives, proteins and whole cells being the target for PAEs, while cationic PAEs have been used for the transfection of eukaryotic cells with RNA.
We apply two three-element arrays consisting either of different GFPs or of charged fluorescent poly(p-aryleneethynylene)s as a successful, hypothesis-free tongue that discriminates more than 30 whiskies according to their country of origin, brand, blend status, and taste. The underlying mechanism is the modulation of the fluorescence intensity of the elements of the sensor array by the different whiskies. Age, country of origin, blend status, and elements of taste were discriminated by the two very different tongues.
We present a simple array composed of an anionic and a cationic poly(para-phenyleneethynylene) (PPE), together with an electrostatic complex between the two of them. The individual PPEs and the PPE complex were employed in the sensing of white wines at pH 13; the complex was also successfully employed as a sensor element at pH 3. The sensing mechanism is fluorescence quenching. Thirteen different wines were differentiated by this chemical tongue, which consists of four elements. The fluorescence quenching is not induced by the major components of the wines. Compounds such as acids, sugars, and alcohols alone do not quench the fluorescence, but rather the colored tannins and other polyphenols contained in wine are the main quenchers. However, the major constituents of wine significantly modulate the quenching of the PPEs by the tannins.
Porous conjugated polymers are synthesized by metal-catalyzed coupling reactions. The progress for porous polymers when planar or tetrahedral building blocks are connected by alkyne units into novel materials is highlighted. The most prominent reaction for the buildup of the microporous alkyne-bridged polymers is the Sonogashira reaction, connecting alkynes to aromatic iodides or bromides. The availability of the building blocks and the potency of the Sonogashira reaction allow preparing a large variety of intrinsically porous polymeric materials, in which rigid struts connect multipronged centers. The microporous polymers are used as catalysts and as storage materials for gases and sensors. Postfunctionalization schemes, understanding of structure-property relationships, and the quest for high porosity are pertinent.
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