Proof of pore formation and biophysical perturbations through a 2D amoxicillin-lipid membrane interaction approach

Abstract

Amoxicillin is a worldwide used antibiotic, and it is classified as a first-line drug against Helicobacter pylori gastric infections. However, the current treatment of these infections has several limitations, such as the side effects and the low therapeutic compliance. Amoxicillin has been associated with gastrointestinal and renal side effects, with higher toxicity when the pH is lower. By considering this association and the well-known pH gradient of the gastric mucosa, this work aims to evaluate the influence of pH on the toxicity of amoxicillin. For that purpose, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers were used since phosphatidylcholines are the most common phospholipid headgroup of biological membranes. To have insight of the effects of amoxicillin, different techniques were employed, namely, isotherm measurements, infrared reflection-absorption spectroscopy, grazing incident X-ray diffraction and Brewster angle microscopy. The monolayers of DPPC spread onto different buffer solutions (pH1.2, pH5 and pH7.4) showed different structural and packing properties. The interaction with amoxicillin also depended on the pH. At pH7.4, the highest effect was visualized at lower pressures, with partial restoration of the biophysical properties of the monolayer at 30 mN.m. A higher perturbation is shown at acidic pH, in which pores were visualized by Brewster angle microscopy. These perturbations may ultimately be related with amoxicillin toxicity.

Licofelone-DPPC Interactions: Putting Membrane Lipids on the Radar of Drug Development

“…The results are shown in Table 2, and the obtained values for the plain DPPC monolayer are in reasonable agreement with the literature [12,31,32].…”

“…Three Bragg peaks were measured in the diffraction patterns of plain DPPC at pH 7.4 and 30 mN m −1 (Figure 5a), as previously described [12]. Two out of the three Bragg peaks were in-plane (Figure 5b), indicating that DPPC domains with different structural arrangements coexist in the monolayer.…”

“…Lower packing may justify the increase of CO hydration (CO vibrational frequency decreased) upon licofelone addition. Indeed, the CO groups of DPPC have permanent electric dipoles [12], and dipole-dipole interactions with adjacent phospholipids may be disrupted with looser packing, enabling the occurrence of more H-bonds with the aqueous subphase. Despite lowering packing density, the licofelone intercalation also seems to induce a steric constraint on the DPPC acyl chains, which became more ordered (CH 2 vibrational frequencies decreased) with reduced trans-gauche isomerizations.…”

“…Thus, drug-induced alterations in membrane lipids may result in changes in membrane-proteins activity, as already described, for instance, for phospholipase A2 [10]. Finally, the toxicity mechanisms of drugs may also include drug-induced modifications in the structure of membrane lipids, as reported for commercial nonsteroidal anti-inflammatory drugs [7,11] and antibiotics [12].…”

<p>Delivering amoxicillin at the infection site &ndash; a rational design through lipid nanoparticles</p>

“…8 Our research group have already shown that, at acidic pHs, AMX can promote pore formation in a monolayer of phosphatidylcholines. 9 The low residence time of AMX in the stomach is also a drawback once H. pylori is located at the gastric mucosa. 3,10 Therefore, the treatment of H. pylori infections is not feasible in monotherapy.…”