Characterization of the effects of drug addition on the structure of glyceryl monoolein/water gel systems using low frequency dielectric spectroscopy

Abstract

The influence of propantheline bromide incorporation on the phase structure of glyceryl monoolein/water systems has been investigated using low-frequency dielectric spectroscopy over a frequency range of 10(-2) to 10(6) Hz at 20 degrees C. The responses of glyceryl monoolein systems composed of 10% and 30% w/w were measured and the spectra modeled using an equivalent circuit based on the Maxwell-Wagner theory.1,2 Marked changes in the dielectric responses of the systems were noted on addition of the propantheline bromide at concentrations up to 10% w/w. For the lamellar (10% w/w water) glyceryl monoolein systems, an increase in the imaginary permitivity was seen, corresponding to an increase in conductivity due to the presence of additional ionic species within the system. Evidence was also obtained for the incorporation of the drug directly into the lipid bilayers, particularly at higher concentrations (10% drug) at which dielectric behavior corresponding to bilayer disruption was seen. Incorporation of 3% and 5% w/w drug into the cubic phase systems (30% w/w water) resulted in a change to the lamellar phase. However, circuit modeling indicated that the system formed structures which showed features of both the lamellar and cubic phases at 3% w/w drug loadings. The study has therefore demonstrated that dielectric analysis may provide a novel means of studying the effects of drug incorporation on the phase behavior of complex gel systems.

Rheological and Dielectric Characterization of Monoolein/Water Mesophases in the Presence of a Peptide Drug

“…11 A number of studies have indicated that the incorporation of drugs may alter the phase behavior of these systems. [12][13][14] Such studies have involved the inclusion of low molecular weight drugs such as lidocaine and propantheline bromide; however to date little is know regarding the effects of peptide or protein drugs on the structure of the mesophases, despite the clear potential of this material to incorporate such molecules and hence act as a corresponding delivery system. Perhaps also surprisingly, there is comparatively little rheological information available for monoolein systems (examples of previous rheological studies include 15,16 ).…”

“…12,17,18 Our previous work examined the use of dielectric analysis as a novel means of studying monoolein mesophases. 14,19,20 The aim of the present study is twofold. Firstly, we present a rheological study of the monoolein systems in conjunction with dielectric analysis as a means of further characterizing the properties and behavior of these gel systems, and secondly we examine the structural effect of adding a model peptide, cyclosporin A (Cyc A), to the monoolein gels.…”

Drug Molecules as Probes for Studying the Compatibility Between Gels and Mucous Tissue with Dielectric Spectroscopy

“…Pharmaceutical applications of this technique include the analysis of disperse systems such as liquid emulsions, [3][4][5][6] semisolid creams, 7,8 liposomes, 9-11 micellar systems, [12][13][14] and liquid crystalline structures. [15][16][17] Furthermore, a number of publications on the dielectric response of gels have appeared. [18][19][20][21][22][23][24] In these studies, the high frequency conductance through the gels (the bulk response) and a polymer barrier layer appearing at low frequencies have been analyzed, on the basis of the theory outlined by Hill & Pickup.…”

An investigation into the supramolecular structure of ternary gel systems using oscillatory rheometry, microscopy, and low frequency dielectric spectroscopy

“…19,24,25 The diagram which was found to yield the optimum fit is shown in Figure 8. The circuit corresponds to a modified Maxwell-Wagner response, 23 comprising a dispersive (frequency dependent) capacitor C s in series with a parallel RC circuit, these two main features corresponding to a barrier (electrode surface) and a bulk response, respectively.…”