A Fluorescence Study of the Interaction of Anticancer Drug Molecule Doxorubicin Hydrochloride in Pluronic P123 and F127 Micelles.

Drug delivery systems for the sustained and target delivery of doxorubicin to tumor cells are a topic of interest due to the efficacy of the doxorubicin in cancer treatment. The use of polymers such as Pluronic is being studied widely for the formulation of doxorubicin hydrochloride. However, the basic understanding of the physicochemical properties of pluronic micelles in presence of doxorubicin hydrochloride is a very essential topic of study. Doxorubicin hydrochloride is fluorescent; this helped us to study its sensitivity towards the Pluronic microenvironment using the fluorescence technique. In this work, the interaction and place of location of doxorubicin hydrochloride in Pluronic F127 and P123 micelles has been studied extensively using steady-state fluorescence intensity, dynamic fluorescence lifetime, quenching studies, dynamic light scattering, and zeta potential measurements, at different Pluronic concentrations. Using a fluorescence quenching experiment, doxorubicin hydrochloride was found to reside near the hydrophilic PEO corona region of the Pluronic micelles. For both the Pluronic, in the concentration range of study, the micellar size was found to be below 30 nm; this may have a greater advantage for various applications.

Direct observation of the rise of delayed fluorescence in dithienylbenzothiadiazole and its role in the excited state dynamics of a donor-acceptor-donor molecule.

Dithienylbenzothiadiazole (DTBT) is used as a building block in several molecules having application in organic light emitting devices (OLED) and organic photovoltaic (OPV) devices. Delayed fluorescence (DF) is the preferred design principle employed currently in OLED research. DTBT has excellent delayed fluorescence properties which makes this moiety a potentially viable OLED material. Here, the dynamics of intersystem crossing (ISC) and reverse intersystem crossing (RISC) have been explored using fluorescence, phosphorescence, fluorescence lifetime and transient absorption measurements. Experimentally it is demonstrated that singlet and triplet states of DTBT are close lying or degenerate and after a certain time the molecules can stay in the singlet or the triplet state forming an equilibrium between the two states which hinders the identification of these two states that could be characterized by routine steady state fluorescence and phosphorescence studies. Similarly in OPV material research, DTBT is coupled with strong donors to form push-pull molecules to produce a prolonged charge separated state. In this study DTBT appended with carbazole at both ends (CDTBT) was used to study the dynamics of DTBT within a donor-acceptor-donor system. The study reveals similar kinds of ISC and RISC in CDTBT along with a competitive deactivation pathway of the singlet state and it was concluded to be through the formation of a charge separated species in CDTBT.

Pyrene-Oxadiazoles for Organic Light-Emitting Diodes: Triplet to Singlet Energy Transfer and Role of Hole-Injection/Hole-Blocking Materials.

Three pyrene-oxadiazole derivatives were synthesized and characterized by optical, electrochemical, thermal, and theoretical investigations to obtain efficient multifunctional organic light emitting diode (OLED) materials. Synthesized molecules were used as emitters and electron transporters in three different device configurations, involving hole-injection/hole-blocking materials that showed good current and power efficiencies. To understand the underlying mechanisms involved in the application of these molecules as emitters and transporters, a detailed photophysical characterization of molecules 4-6 was carried out. The absorption, steady-state fluorescence, phosphorescence, fluorescence lifetime, and phosphorescence lifetime measurements were carried out. The high quantum yield and efficient reverse intersystem crossing leading to delayed fluorescence emission makes the molecule a good emitter, and the charge delocalization properties leading to excimer formation make them efficient electron transporters. Isoenergetic singlet and triplet states of the molecules make the reverse intersystem crossing feasible at room temperature even in the absence of thermal activation.

A fluorescence study on the interaction of telmisartan in triblock polymers pluronic P123 and F127.

Telmisartan is a poorly soluble drug used in treatment of hypertension. There is a recent interest to use pluronic for improving the solubility and bioavailability of these drugs. In this study the interaction of telmisartan with P123 and F127 has been carried out using steady state and time dependent fluorescence study. Quenching of telmisartan fluorescence by potassium iodide is controlled by interactions arising from collisions and complex formation. A comparison of the fluorescence of telmisartan in pluronics with the well understood fluorescence of 8-anilino-1-naphthalene-sulfonic acid, a known fluorescent molecular probe, indicates that telmisartan is generally present in a relatively polar microenvironment with restricted diffusive motion.