Formulation, In Vitro and In Vivo Pharmacokinetics of Anti-HIV Vaginal Bioadhesive Gel

Inexpensive and female-controlled pre-exposure prophylaxis strategies to prevent mucosal transmission of the virus, is urgently needed with the rising prevalence of human immunodeficiency virus (HIV-1 and HIV2) infections in women. Zidovudine-loaded bioadhesive vaginal gel may become one of the very useful strategies, as it can be used not only for controlled release but also for enhancing bioavailability. Drug delivery through vaginal gel is a promising area for continued research with the aim of achieving controlled release with enhanced bioavailability over longer periods of time. The aim of the study was to develop a newer prolong releasing Zidovudine (AZT) bioadhesive vaginal gel to treat HIV infections with increased patient convenience. AZT-loaded bioadhesive vaginal gel was prepared successfully by using cold mechanical method. F3 formulation containing carbopol-HPMC (1:3) was selected and evaluated in order to achieve objectives of this study. In vitro drug release study of F3 showed in 24 h drug released following case I Fickian (n ≤ 0.5) transport mechanism, and in vivo drug release was found much better (T(max)), (C(max)), and bioavailability (F) comparison with oral pour drug solution. It was also showed good extrudability, spreadability, and bioadhesive strength. A generalized protocol, for the further research, in this area will surely expected to yield significant outcome with improved drug delivery system.

Absorption spectra of 7, 7, 8, 8-tetracyanoquinodimethane in micellar solutions

The absorption spectra of 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) with nonionic surfactant. Triton X-100, anionic surfactant, SLS and cationic surfactant, CTAB in aqueous and nonaqueous media have been studied. The spectral studies show that TCNQ forms 1:1 charge-transfer (CT) complex with Triton X-100 in both media. The aqueous solution of TCNQ shows an absorption maxima at 610 nm, which is unperturbed in the presence of SLS but is shifted to 650 nm in the presence of CTAB, indicating the interaction of TCNQ with the cationic surfactant and not with the anionic surfactant. In addition to this, the stability of TCNQ-Triton X-100 complex has been determined and the probable site of CT interaction has been pointed out.

Photophysics of thionine dye in aqueous and liposome media in presence of different reducing agents

The photoelectrochemical and spectral (both absorption and fluorescence) studies of thionine, a cationic phenothiazine dye, have been carried out in aqueous and phosphatidylcholine liposome media in the presence of different reducing agents, such as I(-), Br(-), Cl(-) and Fe(2+). The results show that the photovoltage generation from photoelectrochemical studies and Stern-Volmer quenching constant studied by fluorescence quenching support the photoinduced electron transfer from the reducing agent to the singlet excited thionine dye. Moreover, a good correlation between photovoltages/Stern-Volmer quenching constants vs. reduction potentials of the reducing agents also confirms the above electron transfer in the photoexcited state.

Dispersed Molecular Aggregates

Colloidal dispersions of tungstic acid (H(2)WO(4)) have been prepared in water/(TX-100+alkanol)/n-heptane water-in-oil microemulsion media by reacting Na(2)WO(4) with HCl. The effects of alkanol chain length, TX-100/alkanol mass ratio, temperature, and dilution at different [water]/[TX-100] mole ratios (omega) have been studied by the dynamic light scattering technique. The formation of H(2)WO(4) in the microwater pool has been established by FT-IR measurements. The particle sizes and shapes in microemulsion media and in isolated states have been measured by TEM and SEM techniques. The enthalpy of formation of H(2)WO(4) in the water pool of the microemulsions has also been determined microcalorimetrically. Copyright 2001 Academic Press.

Photophysical studies of 3,3' dioctadecyloxacarbocyanine dye in model biological membranes and different solvents

The absorption and fluorescence spectra of 3,3'-dioctadecyloxacarbocyanine [DiOC18(3)], a cationic oxacarbocyanine dye have been studied in aqueous and nonaqueous media containing egg phosphatidylcholine (PC) as well as in different solvents of diverse nature. The results show the evidence of complex formation of the dye in the ground and in the excited states with PC. The excited state interaction of the dye with PC suggests the electron transfer from PC to dye and this is supported by photovoltage generation in a photoelectrochemical cell consisting of dye and PC in aqueous medium. An attempt has been made to determine the polarity of the microenvironment of the dye in PC liposome or PC reverse micelle from the spectral studies of the dye in different solvents of known polarity.

Photo-effect in phospholipid liposome containing riboflavin

The photovoltage developed in a photoelectrochemical cell consisting of riboflavin (RFN), a neutral dye and phospholipid (PL) liposome in aqueous solution has been found to correlate with the Stern-Volmer constant (KSV) or quenching-rate constant (Kq) of RFN-PL studied by fluorescence spectra. A possible mechanisms of photovoltage generation suggests the photo-induced electron transfer from PL to RFN in liposome through the excited state molecular interaction.

Photoelectrochemistry of dyes in phospholipid liposome

The systems consisting of phenosafranin or thionine dye in the presence of phospholipid liposome in aqueous solution generate photovoltage when studied in a photoelectrochemical cell. A possible mechanism of photovoltage generation suggests the photoinduced electron transfer from phospholipid to dye in liposome through charge-transfer (CT) interaction. In these dye-phospholipid systems, a good correlation between the photovoltage (Voc) determined by photoelectrochemical studies and the equilibrium constant (Kc) determined by spectrophotometric studies, confirms the mechanism.

Photoinduced interaction of thionine with phospholipid and cholesterol in artificial membranes

The photoinduced interaction of thionine dye with phosphatidylcholine (PC) (and its components, e.g. lysoPC, phosphorylcholine and choline) and oxidized cholesterol was studied in artificial membranes using spectrophotometric and photoelectrochemical methods. The results show that the dye (electron acceptor) in its singlet excited state forms 1:1 electron donor-acceptor (EDA) complexes with the lipids (electron donor). The electrode kinetics of the photoinduced redox reactions in the cell were also studied to confirm the mechanism of photoinduced interaction between the dye and the lipid.

Microviscosity in lecithin liposomes: effect of nicotinic acid

We have studied the effect of nicotinic acid, a drug commonly used as a vasodilatory agent and also for the treatment of hypercholesterolemia, on the fluidity profile of liposomes of egg lecithin and dipalmitoyl lecithin, using a fluorescent polarization probe. In both cases the drug decreases the membrane fluidity and for cholesterol-probed liposomes, it disrupts the "intermediate fluid condition" induced by cholesterol. The drug also affects the activation energy for diffusion in the hydrophobic region of the liposomes.

Liposome formation of egg lecithin and its interaction with iodine

The sonicated dispersion of egg lecithin (phosphatidylcholine) in water forms 1:1 molecular complex with iodine, when its concentration is above 1.6 X 10(-5) M. The thermodynamic and spectrophotometric properties of this complex have been determined. The thermodynamic values are: K (25 degrees C) = 1.6 X 10(3) 1 X mol-1, delta G degrees = -18.4 KJ X mol-1, delta H degrees = -27.4 KJ X mol-1 and delta S degrees = -30.0 J X mol-1 X deg-1. The complex shows two absorption bands: one at 293 nm, which is the charge transfer band and the other at 370 nm, which is the blue shifted visible iodine band at 460 nm in water.