Ionic interactions determine the morphology of dried alkali/liposome suspension droplets

Fluidized or not fluidized? Biophysical characterization of biohybrid lipid/protein/polymer liposomes and their interaction with tetracaine

BACKGROUND

Nanomedicine and the pharmaceutical industry demand the investigation of new biomaterials to improve drug therapies. Combinations of lipids, proteins, and polymers represent innovative platforms for drug delivery. However, little is known about the interactions between such compounds and this knowledge is key to prepare successful drug delivery systems.

METHODS

Biophysical properties of biohybrid vesicles (BhVs) composed of phospholipids, proteins, and amphiphilic block copolymers, assembled without using organic solvents, were investigated by differential scanning calorimetry and dynamic light scattering. We studied four biohybrid systems; two of them included the effect of incorporating tetracaine. Thermal changes of phospholipids and proteins when interacting with the amphiphilic block copolymers and tetracaine were analyzed.

RESULTS

Lysozyme and the copolymers adsorb onto the lipid bilayer modifying the phase transition temperature, enthalpy change, and cooperativity. Dynamic light scattering investigations revealed relevant changes in the size and zeta potential of the BhVs. Interestingly, tetracaine, a membrane-active drug, can fluidize or rigidize BhVs.

CONCLUSIONS

We conclude that positively charged regions of lysozyme are necessary to incorporate the block copolymer chains into the lipid membrane, turning the bilayer into a more rigid system. Electrostatic properties and the hydrophilic-lipophilic balance are determinant for the stability of biohybrid membranes.

GENERAL SIGNIFICANCE

This investigation provides fundamental information associated with the performance of biohybrid drug delivery systems and can be of practical significance for designing more efficient drug nanocarriers.

Texture Analysis of Dried Droplets for the Quality Control of Medicines

The quality control of medicines guarantees the effectiveness of treatments for diseases. We explore the use of texture analysis of patterns in dried droplets as a tool to readily detect both impurities and changes in drug concentration. Four types of medicines associated with different routes of administration were analyzed: Methotrexate, Ciprofloxacin, Clonazepam, and Budesonide. We use NaCl and a hot substrate at 63 ∘C to promote aggregate formation and to reduce droplet drying time. Depending on the medicine, optical microscopy reveals different complex aggregates such as circular to oval splatters, fern-like islands, crown shapes, crown needle-like and bump-like patterns as well as dendritic branched and star-like crystals. We use some physical features of the stains (as the stain diameter and superficial area) and gray level co-occurrence matrix (GLCM) to characterize patterns of dried droplets. Finally, we show that structural analysis of stains can achieve 95% accuracy in identifying medicines with 30% water dilution, while it achieves 99% accuracy in detecting drugs with 10% other substances.

Thermal behavior of a lipid-protein membrane model and the effects produced by anesthetics and neurotransmitters

Despite decades of intense research to understand the phenomenon of anesthesia and its membrane-related changes in neural transmission, where lipids and proteins have been proposed as primary targets of anesthetics, the involved action mechanisms remain unclear. Based on the overall agreement that anesthetics and neurotransmitters induce particular modifications in the plasma membrane of neurons, triggering specific responses and changes in their energetic states, we present here a thermal study to investigate membrane effects in a lipid-protein model made of 1,2-dimyristoyl-sn-glycero-3-phosphocholine and albumin from chicken egg white under the influence of neurotransmitters and anesthetics. First, we observe how ovalbumin, ovotransferrin, and lysozyme (main albumin constituents from chicken egg white) interact with the lipid membrane enhancing their lipophilic character while exposing their hydrophobic domains. This produces a lipid separation and a more ordered hybrid lipid-protein assembly. Second, we measured the thermotropic changes of this assembly induced by acetylcholine, γ-aminobutiric acid, tetracaine, and pentobarbital. Although the protein in our study is not a receptor, our results are striking, for they give evidence of the great importance of non-specific interactions in the anesthesia mechanism.