Adsorption behaviour of local anaesthetics in synthetic lipid membranes coated on a quartz-crystal microbalance and correlations with their anaesthetic potencies

Abstract

The partition coefficients in a lipid matrix of seven local anaesthetics in clinical use were obtained using quartz-crystal microbalance (QCM) coated with a synthetic lipid multibilayer film; the resonance frequency of the QCM changes linearly with the amount adsorbed by the lipid matrix. A good correlation was observed between the partition coefficients so determined and the intrinsic local anaesthetic potencies of the same compounds obtained from biological experiments: anaesthetics that induce strong local anaesthesia showed greatest partition into the lipid matrix. The partition coefficients depended on the phase transition of the lipid matrix on the QCM and the ambient p H in the aqueous phase. The uncharged form of amino-type local anaesthetics is strongly adsorbed by the lipid membrane and penetrates deeply into the lipid matrix, especially in the fluid liquid-crystalline state above the phase-transition temperature ( T J , compared with the cationic anaesthetic species present in acidic aqueous solutions.

Gas-Phase Selective Adsorption on Functional Monolayers Immobilized on a Highly Sensitive Quartz-Crystal Microbalance

“…The following equation has been established for an AT-cut shear mode QCM 12 where Δ F is the measured frequency shift (Hz), F 0 is the parent frequency of the QCM (9 × 10 6 Hz), Δ m is the mass change (g), A is the electrode area (0.16 cm 2 ), N is the overtone number (seventh), ρ q is the density of quartz (2.65 g cm -3 ), and m q is the shear modulus of quartz (2.95 × 10 11 dyn cm -2 ). Calibration of the QCM used in our experiments by a polymer-coating method and an LB film transfer method gave the following equation: ,, It is close to the theoretical equation calculated from eq 1 (Δ m = (−7.35 × 10 -9 )Δ F ). Thus, when the 9 MHz QCM was vibrated in the seventh overtone, the sensitivity for the mass change was increased about eight times, in comparison with the standard vibration mode of the 9 MHz QCM [Δ m = (−(1.05 ± 0.01) × 10 -9 )Δ F ].…”

“…Similar intermolecular recognition based on hydrogen bonds is also reported in the adsorption onto a monolayer from the gas phase by using FT-IR spectra and thermal desorption spectra . Molecular recognition in the gas phase is the most simple and fundamental system devoid of solvent effects. , A quartz-crystal microbalance (QCM) is one of several useful techniques for detecting molecular adsorption onto a substrate by measuring in situ mass changes both in gas ,, and solution systems. 2l,− …”

“…We have used the commercially available AT-cut, 9 MHz QCM, in which the frequency linearly decreases by 1 Hz with the increase of ca . 1 ng of mass when the QCM is vibrated at its fundamental frequency. , We recently introduced a highly sensitive QCM, in which the 9 MHz QCM is vibrated at seven times the overtone (63 MHz) of the fundamental frequency, in order to detect the adsorption of small molecules of acetic acid as a monolayer adsorption. The 63 MHz overtone QCM can detect ca .…”

A Highly Sensitive 27 MHz Quartz-Crystal Microbalance as a Device for Kinetic Measurements of Molecular Recognition on DNA Strands

“…A QCM is known to provide very sensitive mass measuring devices in gas phase [6][7][8][9][10][11] and in aqueous solution. [15][16][17][18][19][20][21][22][23] Its resonance frequency decreases linearly upon the increase of mass on the QCM electrode at the nanogram level.…”

Gas Phase Molecular Recognition on Nucleobase Monolayers Immobilized on a Highly Sensitive Quartz-Crystal Microbalance1

“…The observed selectivity of base pair formation, however, was less than that predicted due to the formation of positively charged species during measurements. In addition, it is difficult to determine quantitatively the kinetics of base pair formation by using RETOF-MS. We and other groups have demonstrated that a quartz-crystal microbalance (QCM) is one useful technique to study quantitative kinetics of molecular adsorption onto host membranes by measuring in situ resonance frequency change corresponding to mass changes both in the gas phase 4e,7 and in solution . QCMs are also called a thickness-shear mode resonator.…”