Interactions of Non-steroidal Anti-inflammatory Drugs and Their Bismuth Analogues (BiNSAIDs) with Biological Membrane Mimics at Physiological pH

Neutron reflectometry as a powerful tool to elucidate membrane interactions of drug delivery systems

The last couple of decades have seen an explosion of novel colloidal drug delivery systems, which have been demonstrated to increase drug efficacy, reduce side-effects, and provide various other advantages for both small-molecule and biomacromolecular drugs. The interactions of delivery systems with biomembranes are increasingly recognized to play a key role for efficient eradication of pathogens and cancer cells, as well as for intracellular delivery of protein and nucleic acid drugs. In parallel, there has been a broadening of methodologies for investigating such systems. For example, advanced microscopy, mass-spectroscopic "omic"-techniques, as well as small-angle X-ray and neutron scattering techniques, which only a few years ago were largely restricted to rather specialized areas within basic research, are currently seeing increased interest from researchers within wide application fields. In the present discussion, focus is placed on the use of neutron reflectometry to investigate membrane interactions of colloidal drug delivery systems. Although the technique is still less extensively employed for investigations of drug delivery systems than, e.g., X-ray scattering, such studies may provide key mechanistic information regarding membrane binding, re-modelling, translocation, and permeation, of key importance for efficacy and toxicity of antimicrobial, cancer, and other therapeutics. In the following, examples of this are discussed and gaps/opportunities in the research field identified.

Bioactive Bismuth Compounds: Is Their Toxicity a Barrier to Therapeutic Use?

Bismuth compounds are considered relatively non-toxic, with their low solubility in aqueous solutions (e.g., biological fluids) being the major contributing factor to this property. Bismuth derivatives are widely used for the treatment of peptic ulcers, functional dyspepsia, and chronic gastritis. Moreover, the properties of bismuth compounds have also been extensively explored in two main fields of action: antimicrobial and anticancer. Despite the clinical interest of bismuth-based drugs, several side effects have also been reported. In fact, excessive acute ingestion of bismuth, or abuse for an extended period of time, can lead to toxicity. However, evidence has demonstrated that the discontinuation of these compounds usually reverses their toxic effects. Notwithstanding, the continuously growing use of bismuth products suggests that it is indeed part of our environment and our daily lives, which urges a more in-depth review and investigation into its possible undesired activities. Therefore, this review aims to update the pharmaco-toxicological properties of bismuth compounds. A special focus will be given to in vitro, in vivo, and clinical studies exploring their toxicity.

Biomacromolecular Characterizations Using State-of-the-Art Quartz Crystal Microbalance with Dissipation

Biomolecular characterization is essential in fields such as drug discovery, glycomics, and cell biology. This feature article focuses on the experimental use of quartz crystal microbalance with dissipation (QCM-D) as a powerful analytical technique to probe biological events ranging from biomacromolecular interactions and conformational changes of biomacromolecules to surface immobilization of biomacromolecules and cell morphological changes.

Biological Activities of Bismuth Compounds: An Overview of the New Findings and the Old Challenges Not Yet Overcome

Bismuth-based drugs have been used primarily to treat ulcers caused by Helicobacter pylori and other gastrointestinal ailments. Combined with antibiotics, these drugs also possess synergistic activity, making them ideal for multiple therapy regimens and overcoming bacterial resistance. Compounds based on bismuth have a low cost, are safe for human use, and some of them are also effective against tumoral cells, leishmaniasis, fungi, and viruses. However, these compounds have limited bioavailability in physiological environments. As a result, there is a growing interest in developing new bismuth compounds and approaches to overcome this challenge. Considering the beneficial properties of bismuth and the importance of discovering new drugs, this review focused on the last decade's updates involving bismuth compounds, especially those with potent activity and low toxicity, desirable characteristics for developing new drugs. In addition, bismuth-based compounds with dual activity were also highlighted, as well as their modes of action and structure-activity relationship, among other relevant discoveries. In this way, we hope this review provides a fertile ground for rationalizing new bismuth-based drugs.

Propranolol induces large-scale remodeling of lipid bilayers: tubules, patches, and holes

Herein, we report fluorescence microscopy analysis of the interaction between propranolol (PPN), a beta-adrenergic blocking agent, and planar supported lipid bilayers (SLBs), as model membranes. The results indicate that PPN can remarkably promote largescale remodeling in SLBs with various lipid compositions. It was found that PPN insertion induces the formation of long microtubules that can retract into hemispherical caps on the surface of the bilayer. These transformations are dynamic, partially reversible, and dependent upon the drug concentration. Quantitative analysis revealed a three-step model for PPN-lipid bilayer interaction, with the first step involving interfacial electrostatic adsorption, the second step centered on hydrophobic insertion, and the third step associated with membrane disruption and hole formation. By introducing cholesterol, phosphoethanolamine, phosphatidylglycerol, and phosphatidylserine lipids into the phosphocholine SLBs, it was illustrated that both the chemistry of the lipid headgroups and the packing of lipid acyl chains can substantially affect the particular steps in the interactions between PPN and lipid bilayers. Our findings may help to elucidate the possible mechanisms of PPN interaction with lipid membranes, the toxic behavior and overdosage scenarios of beta-blockers, and provide valuable information for drug development and modification.

Effect of naproxen on the model lipid membrane formed on the water-chitosan subphase

Non steroidal anti-inflammatory drugs (NSAIDs) are those of the most common over the counter (OTC) medications widely used by millions of people every day. Unfortunately, despite their popularity those drugs can cause serious side effects in the digestive system (ulcers, bleeding, and pain). These inconveniences are caused by the changes in the structures of the outer phospholipid layers of gastric mucus and mucosa. As a result the H⁺ ions from the stomach acid can pass easily through these natural protective barriers and damage the epithelial cells which causes ulcers and bleeding. Chitosan as a polysaccharide known for its unique biocompatibility, drug delivery possibilities and wound healing effect has been chosen to examine if it can induce the reduction of undesirable effects of naproxen. This paper focuses on the interactions of the naproxen with a model biological membrane with and without the presence of chitosan. Applying the Langmuir technique coupled with the surface potential measurements and the Brewster angle microscope imaging allowed to characterize successfully examined systems in terms of the monolayer compressibility, thickness, stability, electric properties and morphology. The results proved that the presence of naproxen alters the mechanical and electrical properties of the model membrane depending on its surface pressure. Moreover, the addition of chitosan to the lipid-drug system causes significant changes in the properties of the layer, i.e. a reduction of its compressibility, thickness and morphology modification. Nevertheless, chitosan suppresses some changes induced by naproxen such as alteration of the apparent dipole moment and film stability.

Using refnx to Model Neutron Reflectometry Data from Phospholipid Bilayers

Neutron reflectometry has emerged as a powerful method for studying the structure of thin films in contact with solution at sub-molecular spatial resolution (Penfold and Thomas, J Phys Condens Matter 2:1369-1412, 1990). This type of experiment is undertaken at large international central facilities and experience in data analysis and interpretation is not always available "locally". Here, we describe the application of the refnx software suite (Nelson and Prescott, J Appl Crystallogr 52:193-200, 2019) to the analysis of a single phospholipid bilayer deposited at a silicon/buffer interface. The data is modeled such that the fitted parameters are readily interpretable by researchers working with lipid bilayers.