Array-based sensing of normal, cancerous, and metastatic cells using conjugated fluorescent polymers.

A family of conjugated fluorescent polymers was used to create an array for cell sensing. Fluorescent conjugated polymers with pendant charged residues provided multivalent interactions with cell membranes, allowing the detection of subtle differences between different cell types on the basis of cell surface features. Highly reproducible characteristic patterns were obtained from different cell types as well as from isogenic cell lines, enabling the identification of the cell type as well differentiating between normal, cancerous, and metastatic isogenic cell types with high accuracy.

Detection and differentiation of normal, cancerous, and metastatic cells using nanoparticle-polymer sensor arrays.

Rapid and effective differentiation between normal and cancer cells is an important challenge for the diagnosis and treatment of tumors. Here, we describe an array-based system for identification of normal and cancer cells based on a "chemical nose/tongue" approach that exploits subtle changes in the physicochemical nature of different cell surfaces. Their differential interactions with functionalized nanoparticles are transduced through displacement of a multivalent polymer fluorophore that is quenched when bound to the particle and fluorescent after release.

Nano-conjugate fluorescence probe for the discrimination of phosphate and pyrophosphate.

We describe a pyrophosphate (PPi) probe that is based on a fluorescent dicarboxylate-substituted poly(para-phenyleneethynylene) (PPE) and 10 nm cobalt-iron spinel nanoparticles (NPs) in aqueous media. The spinel NPs efficiently quench the fluorescence of the PPE at a concentration of 20-30 pmol. Addition of phosphate anions to the PPE-NP construct displaces the quenched PPE to give rise to a fluorescent response; we found that PPi and phosphate (Pi) have significantly different binding affinities for the self-assembled materials.

Detection and identification of proteins using nanoparticle-fluorescent polymer 'chemical nose' sensors.

A sensor array containing six non-covalent gold nanoparticle-fluorescent polymer conjugates has been created to detect, identify and quantify protein targets. The polymer fluorescence is quenched by gold nanoparticles; the presence of proteins disrupts the nanoparticle-polymer interaction, producing distinct fluorescence response patterns. These patterns are highly repeatable and are characteristic for individual proteins at nanomolar concentrations, and can be quantitatively differentiated by linear discriminant analysis (LDA).

Molecular recognition based on low-affinity polyvalent interactions: selective binding of a carboxylated polymer to fibronectin fibrils of live fibroblast cells.

To explore molecular recognition of biomolecules in the complex environment of the extracellular matrix, we utilized two fluorescent poly(p-phenyleneethynylene)s bearing either cationic alkylammonium or negatively charged carboyxlate side chains. While incubation of live NIH 3T3 fibroblast cells with the cationic polymer yielded perinuclear punctate staining reminiscent of endocytotic vesicles, the carboxylated polymer revealed a characteristic filamentous staining pattern. Histochemical and immunofluorescence studies demonstrated that the anionic PPE selectively binds to fibronectin fibrils of the extracellular matrix.

Fluorescence self-quenching of a mannosylated poly(p-phenyleneethynylene) induced by concanavalin A.

We report that static quenching of a mannosylated conjugated polymer (sugar-PPE) by Concanavalin A is positively dependent upon sugar-PPE concentration, that is, the recorded Stern-Volmer constants increase with increasing sugar-PPE concentration. Comparison with data obtained from isothermal titration calorimetry (ITC) display the increased sensitivity of the quenching method when compared to ITC. The proposed mechanism suggests the interaction of two or more chains of PPE with one Con A molecule leading to a quenched sugar-PPE-Con A construct.

Use of a folate-PPE conjugate to image cancer cells in vitro.

We have demonstrated synthesis and application of a water-soluble, folate-substituted poly(p-phenyleneethynylene) (PPE) as a fluorescent contrast agent to image cancer cells. This fluorescent polymer targets and images KB cancer cells in vitro with high selectivity. To deliver PPE to the cells, folate ligands have been attached to an amine-functionalized PPE via an amide coupling agent.

Modulating the sensory response of a conjugated polymer by proteins: an agglutination assay for mercury ions in water.

The complexes of a carboxylate-substituted poly(para-phenyleneethynylene) (PPE) with histone, bovine serum albumin, and papain were investigated. At higher concentrations, the proteins have a significant effect on the emission characteristics of the PPE. The electrostatic complexes formed from the PPE, and the proteins are agglutinated by different metal cations.

Nonspecific interactions of a carboxylate-substituted PPE with proteins. A cautionary tale for biosensor applications.

Two carboxylate-substituted, fluorescent (Phi = 0.08), water-soluble poly(p-phenyleneethynylene)s (PPE) and a water-soluble model compound were exposed to a series of proteins and bovine serum. While the anionic PPEs do not have any specific binding sites, they form stable complexes with histone, lysozyme, myoglobin, and hemoglobin.

Mannose-substituted PPEs detect lectins: a model for Ricin sensing.

The interaction of a mannose-substituted poly(para phenyleneethynylene) (mPPE) with a lectin, Concanavalin A (ConA), is reported; the ConA causes fluorescence quenching of the mPPE with a K(SV) of 5.6 x 10(5).

Sugar-poly(para-phenylene ethynylene) conjugates as sensory materials: efficient quenching by Hg2+ and Pb2+ ions.

Three polar poly(para-phenylene ethynylene)s (PPE) were synthesized by utilizing the Heck-Sonogashira protocol. Two of the PPEs carry beta-glucopyranose substituents. Depending upon the linker used between the glycol units and the backbone, the fluorescence of these PPEs can be quenched by Hg2+ and Pb2+ to a varying degree.