Molecular Design of Highly Efficient Heavy-Atom-Free Triplet BODIPY Derivatives for Photodynamic Therapy and Bioimaging.

Novel BODIPY photosensitizers were developed for imaging-guided photodynamic therapy. The introduction of a strong electron donor to the BODIPY core through a phenyl linker combined with the twisted arrangement between the donor and the BODIPY acceptor is essential for reducing the energy gap between the lowest singlet excited state and the lowest triplet state (ΔEST ), leading to a significant enhancement in the intersystem crossing (ISC) of the BODIPYs. Remarkably, the BDP-5 with the smallest ΔEST (ca. 0.44 eV) exhibited excellent singlet oxygen generation capabilities in both organic and aqueous solutions. BDP-5 also displayed bright emission in the far-red/near-infrared region in the condensed states. More importantly, both in vitro and in vivo studies demonstrated that BDP-5 NPs displayed a high potential for photodynamic cancer therapy and bioimaging.

Colorimetric Detection of Thiophenol Based on a Phenolphthalein Derivative and Its Application as a Molecular Logic Gate.

A phenolphthalein-based colorimetric probe bearing a dinitrobenzene group is reported as a thiophenol (PhSH)-selective chemodosimeter. PhSH can react with chemodosimeter 1 to afford phenolphthalein. The addition of PhSH to the aqueous solution of 1 followed by a change in pH of the resulting solution to basic induces a selective color change from colorless to pink. Furthermore, using PhSH and base as inputs and color change of 1 by naked eye as an output, leads to the construction of an AND logic gate.

Recent Progress in Fluorescent Imaging Probes.

Due to the simplicity and low detection limit, especially the bioimaging ability for cells, fluorescence probes serve as unique detection methods. With the aid of molecular recognition and specific organic reactions, research on fluorescent imaging probes has blossomed during the last decade. Especially, reaction based fluorescent probes have been proven to be highly selective for specific analytes. This review highlights our recent progress on fluorescent imaging probes for biologically important species, such as biothiols, reactive oxygen species, reactive nitrogen species, metal ions including Zn(2+), Hg(2+), Cu(2+) and Au(3+), and anions including cyanide and adenosine triphosphate (ATP).

Rhodamine-thiourea Linked Naphthalimide Derivative to Image ATP in Mitochondria using Two Channels.

Adenosine 5'-triphosphate (ATP), synthesized in mitochondria, is an energy molecule in all living things. ATP not only serves as an energy source for protein synthesis and muscle contraction, but also as an important indicator for various diseases, such as Parkinson's disease, cardiovascular disease, and others. Accordingly, detection and sensing of ATP, especially in mitochondria, are important. In this study, a unique ring-opening process of rhodamine was coupled to recognition of ATP via introduction of a thiourea moiety, which was further linked to a naphthalimide group. A strong fluorescent emission at ∼580 nm was accompanied by a color change from colorless to pink upon addition of ATP at pH 7.4. Fluorescent probe 1 successfully imaged mitochondrial ATP with a Pearson's coefficient of 0.8. In addition, green emission from the naphthalimide moiety at ∼530 nm was observed without any change upon addition of ATP. This emission can be considered equivalent to an internal standard to utilize probe 1 as a dual-channel probe for ATP. Furthermore, probe 1 showed negligible cytotoxicity based on MTT assays.

A coumarin-based reversible two-photon fluorescence probe for imaging glutathione near N-methyl-D-aspartate (NMDA) receptors.

Glutathione (GSH) is known to play a key role in the modulation of the redox environment in N-methyl-d-aspartate (NMDA) receptors. Coumarin derivative 1 bearing cyanoacrylamide and ifenprodil moieties was synthesized and reported to monitor GSH near NMDA receptors. The cyanoacrylamide moiety allows probe 1 to monitor GSH reversibly at pH 7.4 and the ifenprodil group acts as a directing group for NMDA receptors. Two-photon fluorescence microscopy allows probe 1 to successfully sense endogenous GSH in neuronal cells and hippocampal tissues with excitation at 750 nm. Furthermore, the addition of H2O2 and GSH induced a decrease and an increase in fluorescence emission. Probe 1 can serve as a potential practical imaging tool to get important information on GSH in the brain.

Rhodamine hydrazone derivatives as Hg2+ selective fluorescent and colorimetric chemosensors and their applications to bioimaging and microfluidic system.

In this paper, we report new rhodamine hydrazone derivatives bearing thiol and carboxylic acid groups as selective fluorescent and colorimetric chemosensors for Hg(2+). The ring-opening process of spirolactam enables the large fluorescent enhancement and colorimetric change upon the addition of Hg(2+). The sample containing Hg(2+) was mixed with one of the chemosensors in a microchannel where the sensor was examined using confocal laser scanning microscopy. A plot of the fluorescent intensities of both chemosensors versus the log concentration of Hg(2+) exhibited a linear response (r(2)=0.95) in the range of 1 nM-1 µM, and the detection limits were 1 nM and 4.2 nM, respectively. Both chemosensors also enable the visualization of Hg(2+) accumulated in the nematode Caenorhabditis elegans previously exposed to nanomolar concentrations of Hg(2+).

Manipulation of fluorescent and colorimetric changes of fluorescein derivatives and applications for sensing silver ions.

Three structurally similar compounds, , bearing a fluorescence chromophore to which are appended morpholine, thiomorpholine and methylpiperazine substituents, display opposite fluorescence responses to pH changes, in contrast to that observed for fluorescein; and have extremely high binding selectivity towards Ag(+) ions and show completely different fluorescent and colorimetric changes upon addition of Ag(+), and the differences are proposed to be associated with different binding modes of and to this metal ion.

Boronic acid-linked fluorescent and colorimetric probes for copper ions.

The first examples of boronic acid-linked fluorescent and colorimetric chemosensors for copper ions are reported; the monoboronic acid-conjugated rhodamine probe displays a highly selective fluorescent enhancement with Cu2+ among the various metal ions whereas the fluorescence of the bisboronic acid-conjugated fluorescein probe is selectively quenched by Cu2+, probably by way of a PET mechanism.

A naphthoimidazolium-cholesterol derivative as a ratiometric fluorescence based chemosensor for the chiral recognition of carboxylates.

Fluorescent chemosensors for sensing chiral molecules have been actively studied in recent years. In the current study, we report a naphthoimidazolium-cholesterol derivative (NI-chol 1) as a fluorescence based chemosensor for chiral recognition, in which the naphthoimidazolium serves not only as a fluorophore but also as a recognition moiety for anions via imidazolium (C-H)+-anion binding and the cholesterol unit acts as a chiral barrier. In particular, NI-chol 1 displayed unique and distinct ratiometric changes with Boc-d-Phe, on the other hand, Boc-l-Phe induced a negligible change. Furthermore, a distinct downfield shift (from 9.64 ppm to 9.96 ppm) of the imidazolium C-H peak was observed for Boc-d-Phe (5 eq.) with severe broadening, which indicates strong ionic hydrogen bonding between the C-H proton and the carboxylate.

Simple but effective way to sense pyrophosphate and inorganic phosphate by fluorescence changes.

A new fluorescent chemosensor based on the acridine-Zn(II) derivative effectively recognizes pyrophosphate and inorganic phosphate at pH 7.4. Acridine derivative 1 displayed a fluorescent quenching effect with pyrophosphate; on the other hand, a large fluorescent enhancement was observed with inorganic phosphate. [structure: see text].

Microwave-assisted polymer-supported combinatorial synthesis.

Lead identification and optimization is always a challenge to the medicinal chemists in drug discovery. Numbers of simple to complex and smaller to bigger organic compounds are prepared to meet the screening purpose of biological targets. Conventional solution phase synthetic methodologies are lacking the speed to run along with the need of medicinally interesting compounds due to their long reaction time, tedious work-up and purification problems. Alternatively opted polymer-supported synthesis of combinatorial libraries has been emerged as a promising tool in generating large numbers of structurally diverse molecules in a manner rapid and parallel. Microwave-assisted solid/liquid phase combinatorial synthetic techniques have been proved efficient in reducing the reaction time from days & hours to minutes & seconds and more promisingly to produce improved yields with high purities. This review briefs about the theory behind microwave chemical technology and glimpses of recent advancements in its application on polymer supported combinatorial synthesis.

Advances in angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs).

Hypertension remains one of the most unmet medical needs of this century. While many drugs are available for treating hypertension, efforts are still insufficient to find potent therapeutic agents since cause for hypertension in all patients is not the same. Angiotensin-converting enzyme inhibitors (ACEIs) have emerged as an important class of drugs in the treatment of hypertension, congestive heart failure (CHF), protenuric renal disease, myocardial infarction and stroke. This class of drugs blocks the conversion of angiotensin I to angiotensin II and prevents bradykinin breakdown. However, the lack of specificity of ACEIs leads to the frequent side effects like cough and angio-oedema. Recently developed, specific non-peptide and orally active angiotensin receptor blockers (ARBs) have become the prime therapeutics as they alone or co-administration with ACE inhibitors can control the renin angiotensin disorders. This review explores recent developments in the design, synthesis, and structural modifications of ACE inhibitors as well as angiotensin receptor blockers.

Traceless liquid phase synthesis of piperazinediones.

Liquid phase combinatorial synthesis (LPCS) of piperazinediones by the use of soluble polymer support is explored to generate libraries. Proline anchored polyethylene glycol monomethyl ether (PEG) underwent dipeptide formation with different Fmoc-amino acids in the presence of dicyclohexyl carbodiimide (DCC). Deprotection of Fmoc accompanied with the cleavage from polymer support with cyclization of dipeptide to piperazinediones offers a facile and effective way to prepare diverse combinatorial libraries. Excellent yields and purities were achieved by simple wash and precipitation method.

Selective homocysteine turn-on fluorescent probes and their bioimaging applications.

The design and development of new pyrene-based fluorescent probes, P-Hcy-1 and P-Hcy-2, which display selective fluorescence enhancements in response to homocysteine (Hcy), are described. The distinctly different fluorescence responses of P-Hcy-1 and P-Hcy-2 to Hcy vs. Cys are explained by theoretical calculations. Finally, the results of cell experiments show that these probes can be used to selectively detect Hcy in mammalian cells.

Highly selective ratiometric fluorescent probe for Au3+ and its application to bioimaging.

The 4-propargylamino-1,8-naphthalimide based fluorescent probe 1 has been explored as a sensor for selective detection of Au(3+). 4-Amino-1,8-naphthalimides, that possess typical intramolecular charge transfer (ICT) electronic characteristics, have been widely used as versatile platforms for fluorescent probes. The newly designed probe 1 contains a propargylamine moiety at C-4 of the naphthalimide chromophore that reacts with Au(3+) to generate a product that has distinctly different electronic properties from 1. Specifically, the probe undergoes a remarkable change in its absorption spectrum upon addition of Au(3+) that is associated with a distinct color change from yellow to light pink. In addition, a blue shift of ca. 56 nm also takes place in the emission spectra of the probe. Consequently, 1 serves as a reaction-based sensor or so called chemodosimeter for Au(3+). Importantly, surfactants enhance the rate of reaction of 1 with Au(3+), thus, enhancing its use as a real time sensor. Finally, the results of studies probing its application to bioimaging of Au(3+) in live cells show that the probe 1 has a unique ability to sense Au(3+) in cells and, in particular, in lipid droplets within cells.

Pyrophosphate selective fluorescent chemosensors based on coumarin-DPA-Cu(II) complexes.

Two new coumarin derivatives displayed highly selective "Off-On" fluorescence changes with pyrophosphate between various anions including ATP, ADP, AMP and inorganic phosphate in 100% aqueous solution.

Highly selective fluorescent probe for Au3+ based on cyclization of propargylamide.

The first "Off-On" type fluorescent probe for Au3+ is reported, in which rhodamine-alkyne derivative displayed highly selective fluorescence enhancement and "naked-eye" detection upon the addition of Au3+ at pH 7.4.

A new fluorescein derivative bearing a boronic acid group as a fluorescent chemosensor for fluoride ion.

A new fluorescein derivative 1 bearing a boronic acid group was investigated as a fluorescent chemosensor for F-. An off-on type fluorescence enhancement was observed by the blocking of the photoinduced electron transfer mechanism, which was induced by the interaction between fluoride and boronic acid moiety.