An Alternative Approach to Quantify Partition Processes in Confined Environments: The Electrochemical Behavior of PRODAN in Unilamellar Vesicles

Abstract

Herein, we investigate the behavior of the electroactive molecular probe 6-propionyl-2-dimethyl amino naphthalene (PRODAN) in large unilamellar vesicles (LUV) formed with the phospholipid 1,2-di-oleoyl-sn-glycero-3-phosphatidylcholine (DOPC) by using cyclic voltammetry (CV). The CV studies in pure water confirm our previous spectroscopic results that PRODAN self-aggregates due to its low water solubility. Moreover, the electrochemical results also reveal that the PRODAN aggregated species are non-electroactive within the studied electrochemical potential region. In DOPC LUV media, the redox behavior of PRODAN shows how the LUV bilayer interacts with PRODAN aggregated species to form PRODAN monomer species. Moreover, the electrochemical response of PRODAN allows us to propose a model for explaining the electrochemical experimental results and--in conjunction with our measurements--for calculating the value of the partition constant (K(p)) of PRODAN between the water and LUV bilayer pseudophases. This value coincides with that obtained through an independent technique. Moreover, our electrochemical model allows us to calculate the diffusion coefficient (D) for the DOPC LUV, which coincides with the D value obtained through dynamic light scattering (DLS). Thus, our data clearly show that electrochemical measurements could be a powerful alternative approach to investigate the behavior of nonionic electroactive molecules embed in a confined environment such as the LUV bilayer. Moreover, we believe that this approach can be used to investigate the behavior of non-optical molecular drugs embedded in bilayer media.

Solvatochromic Pyrene Analogues of Prodan Exhibiting Extremely High Fluorescence Quantum Yields in Apolar and Polar Solvents

“…[30,31] Here, we mainly focused on this hydrogen bonding effect of protic solvents. [30,31] Here, we mainly focused on this hydrogen bonding effect of protic solvents.…”

“…Positions of the emission maxima of Prodan, PA, and PK versus the polarity E T(30). The slopes of the linear fits (solid lines) are 220, 157, and 152 cm À1 , respectively.…”

“…Previously, the relationships between the QYs of solvatochromic dyes including Prodan and matrix solvents have been evaluated and discussed with a combination of experimental and theoretical approaches, [30][31][32]38] and some factors that increase the nonradiative path leading to the observed low QYs of solvatochromic dyes have been proposed (described later). Here, through comparison of PA and PK with Prodan and well-known dyes previously reported, we propose the reasons why PA and PK achieve high QYs in both apolar and polar solvents.…”

Square Wave Voltammetry: An Alternative Technique to Determinate Piroxicam Release Profiles from Nanostructured Lipid Carriers

“…Therefore, SWV presents an attractive technique for quantifying the concentration of electroactive drugs in different delivery systems. There are a few reports that have used SWV to investigate organized systems, such as micelles and liposomes …”

“…There are af ew reports that have used SWV to investigate organized systems, such as micelles and liposomes. [21][22][23][24] Nonsteroidala nti-inflammatory drugs (NSAIDs) are widely used in therapeutics because of their anti-inflammatory and analgesic properties. However,t here are severals econdary effects relatedt ot he use of NSAIDs, with gastric irritation being the most common.…”