Discrimination of Metalloproteins by a Mini Sensor Array Based on Bispyrene Fluorophore/Surfactant Aggregate Ensembles

Fluorescent sensor arrays with pattern recognition ability have been widely used to detect and identify multiple chemically similar analytes. In the present work, two particular bispyrene fluorophores containing hydrophilic oligo(oxyethylene) spacer, 6 and 4, were synthesized, but one is with and the other is without cholesterol unit. Their ensembles with cationic surfactant (CTAB) assemblies realize multiple fluorescence responses to different metalloproteins, including hemoglobin, myoglobin, ferritin, cytochrome c, and alcohol dehydrogenase. The combination of fluorescence variation at monomer and excimer emission of the two binary sensor ensembles enables the mini sensor array to provide a specific fingerprint pattern to each metalloprotein. Linear discriminant analysis shows that the two-ensemble-sensor-based array could well discriminate the five tested metalloproteins. The present work realizes using a mini sensor array to accomplish discrimination of complex analytes like proteins. They also display a very high sensitivity to the tested metalloproteins with detection limits in the range of picomolar concentration.

Aggregation induced emission enhancement and growth of naphthalimide nanoribbons via J-aggregation: insight into disaggregation induced unfolding and detection of ferritin at the nanomolar level

A core substituted naphthalimide AIEEgen displays unusual nanoribbon growth in aqueous media with ultra-sensitivity towards non-heme protein ferritin at physiological conditions.

Color Tuning of Core-Shell Fluorescent Microspheres by Controlling the Conjugation of Poly(p-phenylenevinylene) Backbone

A series of poly(p-phenylenevinylene) (PPV)-coated microspheres with varied fluorescent emission colors have been prepared by controlling the average length of the conjugated segments on the polymer backbone. A modified Wessling method was used for preparing PPV with different conjugation segments. The labile sulfonium groups of the initial polymer precursor of PPV (pre-PPV) were partly substituted by relatively stable methoxyl groups. A series of precursors with different degrees of substitution were prepared by controlling the time of reaction; these precursors were adsorbed onto the negatively charged substrate spheres. Subsequently, heterogeneous thermal treatment eliminated the sulfonium groups selectively to form the conjugated segments on the PPV backbone with varied average conjugation lengths. Under UV exposure, the as-prepared PPV-coated microspheres displayed emission colors ranging from blue to green; a 65 nm shift in the emission maximum was observed in the fluorescence spectra. The gradual color change in emission of spheres was also confirmed in a confocal microscopy study. Further characterizations indicated that these microspheres possessed clear core-shell structure, good monodispersity in size, smooth surfaces, uniform emission, and superior thermal and photo stability. Flow cytometry measurements indicated that these spheres have very different patterns of intensity combination from four-signal receiving channels. The simple method reported herein, which can effectively and efficiently tune the emission color of the fluorescent microspheres, is a promising approach for preparation of microspheres used as encoded signal carrier in flow cytometry and other high-throughput techniques.

Protein binding-induced surfactant aggregation variation: a new strategy of developing fluorescent aqueous sensor for proteins

Novel strategies of developing fluorescent sensors for proteins are highly demanded. In this work, we particularly synthesized a cholesterol-derivatized pyrene probe. Its fluorescence emission is effectively tuned by the aggregation state of a cationic surfactant dodecyltrimethylammonium bromide (DTAB). The used probe/DTAB assemblies exhibit highly sensitive ratiometric responses to pepsin and ovalbumin egg (o-egg) with detection limits of 4.8 and 18.9 nM, respectively. The fluorescence changes indicate the protein-surfactant interaction leads to further aggregation of DTAB assemblies. The results from Tyndall effect and dynamic light scattering verify this assumption. The responses to pepsin and o-egg are due to their strong electrostatic or hydrophobic interaction with DTAB assemblies at pH 7.4. The present noncovalent supramolecular sensor represents a novel and simple strategy for sensing proteins, which is based on the encapsulated fluorophore probing the aggregation variation of the surfactant assemblies.