Knowledge-Based Design of 5-Fluororacil Prodrug Liposomal Formulation: Molecular Packing and Interaction Revealed by Interfacial Isotherms and X-ray Scattering Techniques.

Prodrugs and nanoformulations are two effective strategies for sustained drug release and targeting drug delivery. In this study, we combined the two strategies to judiciously design the liposome formulation incorporating an amphiphilic prodrug of 5-fouroracil (5-FU), named 5-FCPal, for sustained drug release and enhanced bioavailability. 5-FCPal is an analogue of capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine, Xeloda) by substituting the pentyl group at the N4 position with the palmityl. The amphiphilic molecule of 5-FCPal can self-assemble with the phospholipids to form stable vesicle structures with high drug loading. Although lipid vesicles have been widely studied and commercially used for clinical applications, because of the enormous options of the lipids and the equitable balance of hydrophobicity and bioavailability, it is essential to fundamentally understand the molecular interactions when designing and optimizing the liposomal prodrug formulations. We report the study of using X-ray liquid surface scattering techniques integrated with a Langmuir trough to explicitly reveal the interfacial behavior of the monolayer membrane of 5-FCPal with various saturated and unsaturated lipids with positively charged, neutral, and negatively charged head groups. More specifically, interfacial packing of the molecules was quantified using interfacial isotherms, X-ray reflectivity (XR), and grazing-incidence diffraction (GIXD). The results indicate that the interactions between the prodrug and the cationic lipids are most favorable. The highest drug loading is quantified by increasing the molar ratio of the prodrug until stable monolayer structures were disrupted by the multiple-layer domain of prodrug aggregates. Stable liposomes of 100 nm with 50% drug loading of 5-FCPal were generated based on the findings from the X-ray studies.

High-loading Gα13-binding EXE peptide nanoparticles prevent thrombosis and protect mice from cardiac ischemia/reperfusion injury.

Inefficient delivery is a major obstacle to the development of peptide-based drugs targeting the intracellular compartment. We recently showed that selectively inhibiting integrin outside-in signaling using a peptide (mP6) derived from the Gα13-binding ExE motif within the integrin ß3 cytoplasmic domain had antithrombotic effects. Here, we engineered lipid-stabilized, high-loading peptide nanoparticles (HLPN), in which a redesigned ExE peptide (M3mP6) constituted up to 70% of the total nanoparticle molarity, allowing efficient in vivo delivery. We observed that M3mP6 HLPN inhibited occlusive thrombosis more potently than a clopidogrel/aspirin combination without adverse effects on hemostasis in rodents. Furthermore, M3mP6 HLPN synergized with P2Y12 receptor inhibitors or the clopidogrel/aspirin combination in preventing thrombosis, without exacerbating hemorrhage. M3mP6 HLPN also inhibited intravascular coagulation more potently than the P2Y12 inhibitor cangrelor. Postischemia injection of M3mP6 HLPN protected the heart from myocardial ischemia-reperfusion injury in a mouse model. This study demonstrates an efficient in vivo peptide delivery strategy for a therapeutic that not only efficaciously prevented thrombosis with minimal bleeding risk but also protected from myocardial ischemia-reperfusion injury in mice.

Spontaneous collapse of palmitic acid films on an alkaline buffer containing calcium ions.

Understanding the interaction of ions with fatty acids is important to identify their roles in various bioprocesses and to build novel biomimetic systems. In this study, the molecular organization of palmitic acid (PA) films on alkaline buffer solutions (pH 7.4) with and without divalent Ca2+ was measured at a constant surface area using Langmuir troughs coupled with microscopy and X-ray interfacial techniques. Without Ca2+, PA molecules remained a monolayer organization; however, with Ca2+, formation of the inverted bilayers of PA-Ca2+ superstructures caused a spontaneous 2D to 3D transformation under no compression due to the strong interaction between PA and the divalent cation. Self-assembly of this highly-organized inverted bilayer superstructure involved a two-step process of nucleation and nuclei growth. During nucleation, densely packed PA and Ca2+ monolayer firstly corrugated and some of PA and Ca2+ molecules ejected out from the monolayer; the ejected molecules then reorganized and formed the inverted bilayer nuclei. Nucleation was followed by nuclei growth, during which PA and Ca2+ in the monolayer kept integrating into the inverted bilayer structure through molecule migration and PA rotation around Ca2+.