A 'turn-on' fluorescent probe for lysosomal phosphatase: a comparative study for labeling of cancer cells.

We have described the ability of a newly synthesized fluorescent probe (LP1) to detect phosphatase activity in lysosomes in cancer cells. Probe LP1 displayed a 33-fold fluorescence intensity enhancement at λem 532 nm in the presence of phosphatase in HEPES buffer (pH 4.5). The quantum yield of probe LP1 was increased by ∼21-fold upon exposure to phosphatase at acidic pH. The probe LP1 is highly chemoselective toward phosphatase (ALP/ACP) and is insensitive to interference by ubiquitous biological analytes. The high cell adhesion property and cell viability of LP1 indicate that LP1 is biocompatible and nontoxic; these two characteristic features make it a suitable candidate for phosphatase tracking in living cells. LP1 dose-dependent fluorescence images in living cells suggested that the expression of phosphatase in cancer cells (HeLa) is 2-fold higher as compared to the normal NIH-3T3 cells. The colocalization images confirmed that LP1 was exclusively localized in lysosomes. We envision that LP1 could be a potential tool in clinical diagnosis for discriminating cancer cells from normal cells depending on the expression of phosphatase in lysosomes.

Physicochemical perspective of cyclodextrin nano and microaggregates.

''Chemistry beyond the molecule'' is the nickname for supramolecular chemistry. This branch of study is based on molecular recognition that is host-guest chemistry. A number of potential hosts have been defined and applied in scores of studies. Among all potential hosts, cyclodextrins occupy a high position due to their characteristic solubilisation capability and biocompatibility. In the present article we are revisiting the host-guest aspects of cyclodextrins from a physicochemical perspective. We present details of formation and applications of cyclodextrin nanoaggregates induced by guest molecules, the concerned thermodynamics behind the process and also the effect of concentration of the guest molecules on the morphology of the aggregates. This article reviews the topic mainly from the spectroscopic point of view.

Orientation of a TICT probe trapped in the peripheral confined water created by ionic surfactant envelope around silver nanoparticles.

Ionic surfactants are known to aggregate around the surface of a nanoparticle as a single layer in premicellar and a double layer in micellar concentrations. This motif of arrangement indicates the development of a layer of confined water of lower polarity than bulk water around the surface of the nanoparticle. We have demonstrated the behavior of a twisted intramolecular charge transfer (TICT) probe, trans-2-[4-(dimethylamino)styryl]benzothiazole (DMASBT), in the confined aqueous layer developed at the surface of spherical silver nanoparticles (Ag NPs) at and above the critical micellar concentrations (CMC) of a cationic and an anionic surfactant, namely, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). It is observed that the presence of charged surfactant head groups affects DMASBT differentially in the ground and the excited states. In presence of CTAB, DMASBT turns over in the excited state and interacts with the Ag NP surface, whereas in SDS the probe remains in its original orientation during the interaction. Steady-state and time-resolved fluorescence spectral studies provide enough evidence for orientation of the TICT probe in the peripheral water of Ag NP created by the surfactants. The results were confirmed by steady-state anisotropy measurements. The data show the difference between the properties of the confined peripheral water and the bulk aqueous environment. The TICT probe, DMASBT, is proved to be an excellent marker for the phenomenon.

Effect of cyclodextrins on the photophysics of three indoloquinoline derivatives: an intriguing fluorometric study.

Effect of cyclodextrin encapsulation on the photophysics of three indoloquinoline derivatives, namely, 5-methyl-5H-indolo[3,2-c]quinoline (MIQ), 8-chloro-5-methyl-5H-indolo[3,2-c]quinoline (CMIQ), and 2,8-dichloro-5-methyl-5H-indolo[3,2-c]quinoline (DCMIQ), has been studied using steady state and time-resolved fluorescence spectroscopy. The three compounds, which are basically cryptosanguinolentines, exist mainly in their zwitterionic forms in the excited state. Appreciable emission from the π-π* state can be observed on excitation of the compounds at a specific wavelength. The existence of zwitterions in the excited state leads to mutual interaction to form dimers triggered by the presence of the hydrophobic nanocavities of cyclodextrins (CDs) through Coulombic interaction. This is evidenced by steady state fluorescence measurements and treating the fluorophores with CDs of different cavity space. The photophysical behavior of the compounds gets dramatically modulated when they are treated with α-, ß-, and γ-CD hosts. Presence of chloro substituent/s on the parent molecule and the extent of encapsulation by CDs of different dimensions exhibit enormous alterations in the fluorescence characteristics of the compounds. Solvation of the chromophoric moiety by water molecules deviates in character due to the guest-host interaction. Trapped water molecules inside the bigger cavity of γ-CD seem to play a vital role in quenching the fluorescence of the zwitterions of the molecules.

Opening of DNA double helix at room temperature: Application of alpha-cyclodextrin self-aggregates.

Self-aggregation of alpha-cyclodextrin (alpha-CD) can induce DNA opening at room temperature (25 degrees C) owing to the hydroxyl groups on the surface of the spherical aggregates of alpha-CD, which promote hydrogen bonding with the flipped-out bases in DNA duplex prohibiting them from reverting back.

Steady state fluorescence spectroscopic technique to reveal the thermodynamics of fragmentation of compound induced alpha-cyclodextrin nanotubular suprastructures.

Calorimetric titration technique using flow devices is generally used to understand the thermodynamics of nanotubular suprastructure formations, however high concentrations of the guest molecules used may disrupt the suprastructures. This report shows thermodynamic information can also be obtained by the implementation of fluorescence spectroscopy. Denaturants break nanotubular assembly created by the guest molecule leading to change in guest fluorescence on altering the denaturant concentration. This phenomenon can be monitored to get the relative change in enthalpy in the process of fragmentation of the nanotubular structures along with the change in the standard free energy. The fluorescence technique uses appropriate concentration of the guest molecules required to form nanotubular suprastructures.