Intracellular fate of bioresponsive poly(amidoamine)s in vitro and in vivo.

Linear poly(amidoamine)s (PAAs) have been designed to exhibit minimal non-specific toxicity, display pH-dependent membrane lysis and deliver genes and toxins in vitro. The aim of this study was to measure PAA cellular uptake using ISA1-OG (and as a reference ISA23-OG) in B16F10 cells in vitro and, by subcellular fractionation, quantitate intracellular trafficking of (125)I-labelled ISA1-tyr in liver cells after intravenous (i.v.) administration to rats. The effect of time after administration (0.5-3h) and ISA1 dose (0.04-100mg/kg) on trafficking, and vesicle permeabilisation (N-acetyl-b-D-glucosaminidase (NAG) release from an isolated vesicular fraction) were also studied. ISA1-OG displayed approximately 60-fold greater B16F10 cell uptake than ISA23-OG. Passage of ISA1 along the liver cell endocytic pathway caused a transient decrease in vesicle buoyant density (also visible by TEM). Increasing ISA1 dose from 10mg/kg to 100mg/kg increased both radioactivity and NAG levels in the cytosolic fraction (5-10 fold) at 1h. Moreover, internalised ISA1 provoked NAG release from an isolated vesicular fraction in a dose-dependent manner. These results provide direct evidence, for the first time, of PAA permeabilisation of endocytic vesicular membranes in vivo, and they have important implications for potential efficacy/toxicity of such polymeric vectors.

Quantitative comparison between microfluidic and microtiter plate formats for cell-based assays.

In this paper, we compare a quantitative cell-based assay measuring the intracellular Ca2+ response to the agonist uridine 5'-triphosphate in Chinese hamster ovary cells, in both microfluidic and microtiter formats. The study demonstrates that, under appropriate hydrodynamic conditions, there is an excellent agreement between traditional well-plate assays and those obtained on-chip for both suspended immobilized cells and cultured adherent cells. We also demonstrate that the on-chip assay, using adherent cells, provides the possibility of faster screening protocols with the potential for resolving subcellular information about local Ca2+ flux.

Influence of hydrodynamic conditions on quantitative cellular assays in microfluidic systems.

This study demonstrates the importance of the hydrodynamic environment in microfluidic systems in quantitative cellular assays using live cells. Commonly applied flow conditions used in microfluidics were evaluated using the quantitative intracellular Ca2+ analysis of Chinese hamster ovary (CHO) cells as a model system. Above certain thresholds of shear stress, hydrodynamically induced intracellular Ca2+ fluxes were observed which mimic the responses induced by chemical stimuli, such as the agonist uridine 5'-triphosphate tris salt (UTP). This effect is of significance given the increasing application of microfluidic devices in high-throughput cellular analysis for biophysical applications and pharmacological screening.

Effect of chain length on transfection properties of spermine-based gemini surfactants.

The synthesis and associated structure-activity relationships for gene transfection of a series of spermine-derived cationic gemini surfactants incorporating diamino acid headgroups and either identical (symmetrical) or different (unsymmetrical) lipophilic tailgroups is described. Transfection activity is found to depend critically upon the structural elements present.