Sterically stabilized liposomes (SSLs) (PEGylated liposomes) are applied as effective drug delivery vehicles. Understanding the interactions between hydrophobic compounds and PEGylated membranes is therefore important to determine the effectiveness of PEGylated liposomes for delivery of drugs or other bioactive substances. In this study, we have combined fluorescence quenching analysis (FQA) experiments and all-atom molecular dynamics (MD) simulations to study the effect of membrane PEGylation on the location and orientation of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) that has been used in our study as a model hydrophobic compound. First, we consider the properties of p-THPP in the presence of different fluid phosphatidylcholine bilayers that we use as model systems for protein-free cell membranes. Next, we studied the interaction between PEGylated membranes and p-THPP. Our MD simulation results indicated that the arrangement of p-THPP within zwitterionic membranes is dependent on their free volume, and p-THPP solubilized in PEGylated liposomes is localized in two preferred positions: deep within the membrane (close to the center of the bilayer) and in the outer PEG corona (p-THPP molecules being wrapped with the polymer chains). Fluorescence quenching methods confirmed the results of atomistic MD simulations and showed two populations of p-THPP molecules as in MD simulations. Our results provide both an explanation for the experimental observation that PEGylation improves the drug-loading efficiency of membranes and also a more detailed molecular-level description of the interactions between porphyrins and lipid membranes.
Photodynamic therapy (PDT) is a clinically approved method for treatment of cancer, microbial infections, and some other diseases. PDT has proved effective in the treatment of malignancies of various organs, including lung, bladder, gastrointestinal tract, and skin, and in the therapy of bacterial infection of skin wounds and carious lesions. It employs a combination of light and a drug (photosensitizer, PS) to induce phototoxicity against cancerous cells or bacteria. The efficiency of currently used PSs is limited due to their hydrophobic nature, which causes aggregation of the PS in aqueous media and low tumor selectivity (a low value of the tumor-to-normal tissue ratio). The purpose of this review is to present some aspects of the current state of knowledge on nanostructural carriers for the PS delivery. In this paper we reviewed studies on the development of nanostructural materials for PDT, especially those based on the polymeric and liposomal formulation of PS. We focused mainly on the nanostructural PSs obtained by the covalent attachment of hydrophilic polymer chain to the low-molecular-weight PS, the incorporation of PS into polymeric nanostructures such as micelles, and the solubilization of PS in liposome carriers.
Poly(ε-caprolactone) microparticles containing embelin (PCLE) are prepared by electrohydrodynamic atomization (EHDA) and emulsion-solvent evaporation techniques. Microparticles are characterized in terms of drug state, drug-loading capacity, encapsulation efficiency, morphology and in vitro release in different mediums.Physicochemical, morphological, and thermal characterization is presented. Kinetic analysis is performed. EHDA microparticles present higher size, surface area, and encapsulation efficiency. The release profiles combine a high initial release, followed by a slow-controlled release stage. Electrosprayed PCLE presented characteristics such as size (3.14 ± 0.05 μm), zeta potential (−49.22 ± 2.88 mV) and release profiles that could be attractive for the development of microcarriers for pulmonary administration of embelin. K E Y W O R D Selectrospraying, embelin, emulsion, microparticles, poly(ε-caprolactone), release profiles How to cite this article: Cortez Tornello PR, Feresin GE, Tapia A, Dzieciuch M, Cuadrado TR, Abraham GA. Effect of processing techniques on new poly (ε-caprolactone)-embelin microparticles of biomedical interest.
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