Spatial Control of Gene Expression by Nanocarriers Using Heparin Masking and Ultrasound-Targeted Microbubble Destruction

We developed a method to spatially control gene expression following nonviral delivery of DNA. This method includes surface-modifying DNA nanocarriers with heparin to inhibit passive gene transfer in both the target and the off-target tissues and using ultrasound-targeted microbubble destruction (UTMD) to selectively activate heparin-inhibited gene transfer at the target site. We observed that the engraftment of heparin onto the surface of cationic liposomes reduced off-target gene expression in the liver, a major site of nanoplex accumulation, by more than 700-fold compared to the nonheparinized PEGylated liposomes. We further observed that tumor-directed UTMD increased gene transfer with heparin-modified nanoplexes by more than 10-fold. This method augmented tumor-to-liver selectivity of gene expression by 4000-fold compared to controls. We conclude that heparinization of DNA nanocarriers in conjunction with localized activation of gene transfer by UTMD may enable greater spatial control over genetic therapy

sj-pdf-1-ems-10.1177_14690667221139419 - Supplemental material for Mass spectrometric detection of ion pairs containing rigid copper clusters and weakly coordinating counter ions using liquid injection field desorption/ionisation

Supplemental material, sj-pdf-1-ems-10.1177_14690667221139419 for Mass spectrometric detection of ion pairs containing rigid copper clusters and weakly coordinating counter ions using liquid injection field desorption/ionisation by Julia Taubert, Matthias Vogt and Robert Langer in European Journal of Mass Spectrometry</p

Metal–Ligand Cooperation in H₂ Activation with Iron Complexes Bearing Hemilabile Bis(diphenylphosphino)amine Ligands

The octahedral transition-metal complex [(dppa)­Fe­(Ph₂P–N–PPh₂)₂] (<b>1</b>) [dppa = bis­(diphenylphosphino)­amine] with homofunctional bidentate ligands is described. The ligand exhibits hemilability due to its small bite angle and the steric repulsion of the coordinated donor groups. As the {Ph₂P–N–PPh₂}⁻ ligand can act as an internal base, heterolytic cleavage of dihydrogen by complex <b>1</b> leads to the formation of the hydride complex [(dppa)­(Ph₂P–N–PPh₂)­Fe­(H)­(κ¹-Ph₂P–NH–PPh₂)₂] (<b>2</b>), representing an example of cooperative bond activation with a homofunctional hemilabile ligand. This study demonstrates that hemilability of homofunctionalized ligands can be affected by careful adjustment of geometric parameters

A Novel Mechanism Is Involved in Cationic Lipid-Mediated Functional siRNA Delivery

A key challenge for therapeutic application of RNA interference is to efficiently deliver synthetic small interfering RNAs (siRNAs) into target cells that will lead to the knockdown of the target transcript (functional siRNA delivery). To facilitate rational development of nonviral carriers, we have investigated by imaging, pharmacological and genetic approaches the mechanisms by which a cationic lipid carrier mediates siRNA delivery into mammalian cells. We show that ∼95% of siRNA lipoplexes enter the cells through endocytosis and persist in endolysosomes for a prolonged period of time. However, inhibition of clathrin-, caveolin-, or lipid-raft-mediated endocytosis or macropinocytosis fails to inhibit the knockdown of the target transcript. In contrast, depletion of cholesterol from the plasma membrane has little effect on the cellular uptake of siRNA lipoplexes, but it abolishes the target transcript knockdown. Furthermore, functional siRNA delivery occurs within a few hours and is gradually inhibited by lowering temperatures. These results demonstrate that although endocytosis is responsible for the majority of cellular uptake of siRNA lipoplexes, a minor pathway, probably mediated by fusion between siRNA lipoplexes and the plasma membrane, is responsible for the functional siRNA delivery. Our findings suggest possible directions for improving functional siRNA delivery by cationic lipids

The biocompatibility of mesoporous silicates

Micro- and nano-mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes similar to 150 nm, similar to 800 nm and similar to 4 mu m and pore sizes of 3 nm, 7 nm and 16 nm, respectively, is examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over 3 months, with good biocompatibility on histology at all time points. In contrast, intra-peritoneal and intra-venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicated that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity might be mitigated by modification of the materials. (C) 2008 Elsevier Ltd. All rights reserved

The biocompatibility of mesoporous silicates

Micro- and nano-mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes similar to 150 nm, similar to 800 nm and similar to 4 mu m and pore sizes of 3 nm, 7 nm and 16 nm, respectively, is examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over 3 months, with good biocompatibility on histology at all time points. In contrast, intra-peritoneal and intra-venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicated that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity might be mitigated by modification of the materials. (C) 2008 Elsevier Ltd. All rights reserved

Manganese(I) Tricarbonyl Complexes with Bidentate Pyridine-Based Actor Ligands: Reversible Binding of CO₂ and Benzaldehyde via Cooperative C–C and Mn–O Bond Formation at Ambient Temperature

We report manganese(I) tricarbonyl complexes decorated with imino- and amino-pyridine ligands [Mn(impy)(CO)3Br] and [Mn(ampy)(CO)3Br], respectively. Both compounds can be transformed either via two-electron reduction for the former or double deprotonation for the latter into anionic species with a disturbed (“dearomatized”) π-electron system of the pyridine ring M[Mn(amidopy*)(CO)3] (M = alkali metal). The newly formed five-coordinated complex is anionic and encompasses a nucleophilic carbon center within its metalla cycle. This leads to noteworthy reactivity: [Mn(amidopy*)(CO)3]− readily reacts with CO double bonds. Specifically, CO2 and benzaldehyde can bind to the complex via a metal–ligand cooperative [1,3]-addition under C–C and Mn–O bond formation and concomitant rearomatization of the pyridine ring. Remarkably, we found that this addition is reversible. Exchange reactions using isotopically labeled 13CO2 indicate reversible C–C and Mn–O bond formation at ambient temperature. Likewise, bonded benzaldehyde is exchanged from the complex under a CO2 atmosphere. Density functional theory calculations suggest a significant role for the cationic counter ion in the bond activation reactions that can make this bond activation feasible

Manganese(I) Tricarbonyl Complexes with Bidentate Pyridine-Based Actor Ligands: Reversible Binding of CO₂ and Benzaldehyde via Cooperative C–C and Mn–O Bond Formation at Ambient Temperature

We report manganese(I) tricarbonyl complexes decorated with imino- and amino-pyridine ligands [Mn(impy)(CO)3Br] and [Mn(ampy)(CO)3Br], respectively. Both compounds can be transformed either via two-electron reduction for the former or double deprotonation for the latter into anionic species with a disturbed (“dearomatized”) π-electron system of the pyridine ring M[Mn(amidopy*)(CO)3] (M = alkali metal). The newly formed five-coordinated complex is anionic and encompasses a nucleophilic carbon center within its metalla cycle. This leads to noteworthy reactivity: [Mn(amidopy*)(CO)3]− readily reacts with CO double bonds. Specifically, CO2 and benzaldehyde can bind to the complex via a metal–ligand cooperative [1,3]-addition under C–C and Mn–O bond formation and concomitant rearomatization of the pyridine ring. Remarkably, we found that this addition is reversible. Exchange reactions using isotopically labeled 13CO2 indicate reversible C–C and Mn–O bond formation at ambient temperature. Likewise, bonded benzaldehyde is exchanged from the complex under a CO2 atmosphere. Density functional theory calculations suggest a significant role for the cationic counter ion in the bond activation reactions that can make this bond activation feasible

Synthesis of Poly(β-amino ester)s Optimized for Highly Effective Gene Delivery

Several families of synthetic polymers, including degradable poly(β-amino ester)s, have been previously shown to effectively mediate gene transfer. However, the combined impact of potentially significant factorssuch as polymer molecular weight, polymer chain end-group, and polymer/DNA ratioon different gene transfer properties has yet to be systematically investigated. The elucidation of these relationships may aid in the design of nonviral vectors with greatly enhanced transfection properties. To examine these factors, two distinct poly(β-amino ester) structures, Poly-1 and Poly-2, were generated by adding 1,4-butanediol diacrylate and 1,6-hexanediol diacrylate, respectively, to 1-aminobutanol. Twelve unique versions of each structure were synthesized by varying amine/diacrylate stoichiometric ratios, resulting in polymers with either amine or acrylate end-groups and with molecular weights ranging from 3350 to 18 000. Using high throughput methods, all polymers were tested in quadruplicate at nine different polymer/DNA ratios ranging from 10:1 w/w to 150:1 w/w. Through the optimization of molecular weight, polymer chain end-group, and polymer/DNA ratio, these polymers successfully mediated gene transfer at levels that surpassed both PEI and Lipofectamine 2000 in vitro

Injectable in situ cross-linking hydrogels for local antifungal therapy

Invasive fungal infections can be devastating, particularly in immunocompromised patients, and difficult to treat with systemic drugs. Furthermore, systemic administration of those medications can have severe side effects. We have developed an injectable local antifungal treatment for direct administration into existing or potential sites of fungal infection. Amphotericin B (AmB), a hydrophobic, potent, and broad-spectrum antifungal agent, was rendered water-soluble by conjugation to a dextran-aldehyde polymer. The dextranaldehyde-AmB conjugate retained antifungal efficacy against Candida albicans. Mixing carboxymethylcellulose-hydrazide with dextran-aldehyde formed a gel that cross-linked in situ by formation of hydrazone bonds. The gel provided in vitro release of antifungal activity for 11 days. and contact with the gel killed Candida for three weeks. There was no apparent tissue toxicity in the murine peritoneum and the gel caused no adhesions. Gels produced by entrapment of a suspension of AmB in CMC-dextran without conjugation of drug to polymers did not release fungicidal activity, but did kill on contact Injectable systems of these types, containing soluble or insoluble drug formulations, could be useful for treatment of local antifungal infections, with or without concurrent systemic therapy. (C) 2009 Elsevier Ltd. All rights reserved