<i>In Vivo</i> Evaluation of pH-Sensitive Polymer-Based Immunoliposomes Targeting the CD33 Antigen

The purpose of this study was to evaluate in vivo a targeted pH-sensitive liposomal formulation tailored to promote the efficient intracellular delivery of 1-β-d-arabinofuranosylcytosine (ara-C) to human myeloid leukemia cells. Specifically, pH-sensitive immunoliposomes were obtained by anchoring a copolymer of dioctadecyl, N-isopropylacrylamide and methacrylic acid in bilayers of PEGylated liposomes (LP) and by coupling the whole anti-CD33 monoclonal antibody (mAb) or its Fab′ fragments. Their pharmacokinetic and biodistribution profiles were assessed in Balb/c and leukemic HL60-bearing immunodepressed (SCID) mice. In naive mice, nontargeted and pH-sensitive Fab′-LP had longer circulation times than LP with whole mAb. In SCID/HL60 (CD33+) mice, the pharmacokinetic and biodistribution profiles of LP and encapsulated ara-C were comparable between nontargeted and pH-sensitive Fab′-LP. In leukemic mice, only pH-insensitive, ara-C-loaded Fab′ induced prolonged survival times. The apparent absence of pH-sensitive Fab′-LP effect could be related to lower exposure to ara-C in SCID mice

Thiol-Functionalized Poly(ethylene glycol)-<i>b</i>-polyesters: Synthesis and Characterization

This paper describes a novel synthetic strategy for the preparation of thiol end-functionalized poly(ethylene glycol) (PEG)-b-polyesters. Block copolymers containing an internal disulfide bond were prepared through the ring-opening polymerization of dl-lactide (LA) and ε-caprolactone (CL) employing a PEG disulfide [(PEG-S)2] as the macroinitiator. This initiator was synthesized from α-tert-butanethio-ω-hydroxy-PEG (tBu-S-PEG) through the deprotection of tBu and the subsequent formation of a disulfide. The disulfide bond of the block copolymers was cleaved by reduction using tributylphosphine to generate block copolymers bearing a thiol at the PEG chain end. Thiolated PEG-b-PLA and PEG-b-PCL with number-average molecular weights (Mn) in the range of 3300−5800 and 3600−4600, respectively, were thereby obtained. The PLA and PCL contents could be varied according to the feed ratio and ranged between 20−47 and 15−30 mol %, respectively. Aqueous solutions of the disulfide block copolymers formed degradable gels at high concentration and underwent a gel−sol transition upon an increase in temperature. The gels were liquefied by treating with dithiothreitol, indicating that the triblock configuration is essential for the gelation

Transmembrane pH-Gradient Liposomes To Treat Cardiovascular Drug Intoxication

Injectable scavenging nanocarriers have been proposed as detoxifying agents when there are no specific antidotes to treat pharmacological overdoses. They act by capturing the drug in situ, thereby restricting distribution in tissues. In the clinic, the only systems used for that purpose are parenteral lipid emulsions, which are relatively inefficient in terms of uptake capacity. In this study, we investigated long-circulating liposomes with a transmembrane pH gradient as treatment for diltiazem intoxication. The unique ion-trapping properties of the vesicles toward ionizable compounds were exploited to sequester the drug in the bloodstream and limit its pharmacological effect. After in vitro optimization of the formulation, the in vivo scavenging properties of the liposomes were demonstrated by examining the drug’s pharmacokinetics. The reduced volume of distribution and increased area under the plasma concentration versus time curve in animals treated with liposomes indicated limited tissue distribution. The vesicles exerted a similar but more pronounced effect on deacetyl-diltiazem, the principal active metabolite of the drug. This in vivo uptake of both drug and metabolite altered the overall pharmacological outcome. In rats receiving an intravenous bolus of diltiazem, the liposomes tempered the hypotensive decline and maintained higher average blood pressure for 1 h. The detoxifying action of liposomes was even stronger when the rats received higher doses of the drug via perfusion. In conclusion, the present work provided clear evidence that liposomes with a transmembrane pH gradient are able to change the pharmacokinetics and pharmacodynamics of diltiazem and its metabolite and confirmed their potential as efficient detoxifying nanocarriers

pH-Responsive Molecular Tweezers

pH-Responsive Molecular Tweezer

pH-Responsive Molecular Tweezers

pH-Responsive Molecular Tweezer

A Chiral Phosphoramidite Reagent for the Synthesis of Inositol Phosphates

There is a paucity of chiral phosphoramidite reagents or chiral catalysis methods for the synthesis of biologically relevant inositol phosphates. A new <i>C</i>₂-symmetrical chiral phosphoramidite has been developed and successfully applied to the synthesis of a set of chiral inositol bisphosphates. The reagent allowed bis-phosphorylation and chiral resolution, resulting in a concise synthetic route, thus expanding the toolbox available for the preparation of biologically relevant inositol phosphates in high optical purity

A Chiral Phosphoramidite Reagent for the Synthesis of Inositol Phosphates

There is a paucity of chiral phosphoramidite reagents or chiral catalysis methods for the synthesis of biologically relevant inositol phosphates. A new <i>C</i>₂-symmetrical chiral phosphoramidite has been developed and successfully applied to the synthesis of a set of chiral inositol bisphosphates. The reagent allowed bis-phosphorylation and chiral resolution, resulting in a concise synthetic route, thus expanding the toolbox available for the preparation of biologically relevant inositol phosphates in high optical purity

Effect of Poly(<i>N</i>-vinyl-pyrrolidone)-<i>block</i>-poly(d,l-lactide) as Coating Agent on the Opsonization, Phagocytosis, and Pharmacokinetics of Biodegradable Nanoparticles

The effect of the coating polymer poly(N-vinyl-pyrrolidone) (PVP) on the protein adsorption, phagocytosis, and pharmacokinetics of poly(D,L-lactide)-based nanoparticles was evaluated in vitro and in vivo. Control poly(ethylene glycol) (PEG)-coated nanoparticles were included for comparison. While no difference between PEG- and PVP-decorated nanoparticles in terms of amount of adsorbed protein was evident upon incubation in single protein solutions (BSA, IgG), incubation in serum revealed a protein adsorption pattern both quantitatively and qualitatively distinct. Larger amounts of complement components and immunoglobulins were found to adhere to PVP-coated particles, whereas PEG particles showed preferential adsorption of apolipoproteins. Furthermore, preopsonization in fresh rather than heat-inactivated serum enhanced uptake of both types of particles by murine RAW 264.7 macrophages. However, when isolated rat Kupffer cells were employed, activation of the complement system significantly enhanced the uptake of PVP-coated nanoparticles compared to PEG particles. Ultimately, PVP-coated nanoparticles exhibited considerably shorter circulation times compared to their PEG counterparts when administered intravenously to rats

Activatable Cell Penetrating Peptide–Peptide Nucleic Acid Conjugate via Reduction of Azobenzene PEG Chains

The use of stimuli-responsive bioactive molecules is an attractive strategy to circumvent selectivity issues <i>in vivo</i>. Here, we report an activatable cell penetrating peptide (CPP) strategy ultimately aimed at delivering nucleic acid drugs to the colon mucosa using bacterial azoreductase as the local reconversion trigger. Through screening of a panel of CPPs, we identified a sequence (M918) capable of carrying a nucleic acid analogue payload. A modified M918 peptide conjugated to a peptide nucleic acid (PNA) was shown to silence luciferase in colon adenocarcinoma cells (HT-29-luc). Reversible functionalization of the conjugate’s lysine residues via an azobenzene self-immolative linkage abolished transfection activity, and the free CPP-PNA was recovered after reduction of the azobenzene bond. This activatable CPP conjugate platform could find applications in the selective delivery of nucleic acid drugs to the colon mucosa, opening therapeutic avenues in colon diseases

PEG Nanocages as Non-sheddable Stabilizers for Drug Nanocrystals

Many potent drugs are difficult to administer intravenously due to poor aqueous solubility. One validated approach for addressing this issue is to process them into colloidal dispersions known as “nanocrystals” (NCs). However, NCs possess high-energy surfaces that must be stabilized with surfactants to prevent aggregation. In addition, the stabilizer provides a means of anchoring targeting moieties to the NCs for achieving deposition or uptake at specified locations. Nevertheless, a critical challenge is that the surfactant (and consequently the targeting agents) can be shed upon high dilution. This work demonstrates successful cross-linking by click chemistry of stabilizers around paclitaxel NCs to form polymeric “nanocages”. Cross-linking does not cause aggregation, as evidenced by transmission electron microscopy, and the nanocages retained the particulate drug through a combination of physical entrapment and physisorption. Size measurements by dynamic light scattering showed that nanocages act as sterically stabilizing barriers to particle–particle interactions and aggregation. The nanocages were shown to be less shed from the NCs than comparable non-cross-linked stabilizers. This contribution provides crucial general tools for preparing poorly sheddable stabilizing coatings to NCs and potentially other classes of nanoparticles for which covalent attachment of the stabilizer to the particle is undesirable (<i>e.g.</i>, a drug) or impossible (chemically inert). The presented approach also offers the possibility of more stably attaching targeting moieties to the latter by use of heterotelechelic PEG derivatives, which may favor active targeting and internalization by cells