In vitro dose–response effects of poly(amidoamine) dendrimers [amino-terminated and surface-modified with N-(2-hydroxydodecyl) groups] and quantitative determination by a liquid chromatography–hybrid quadrupole/time-of-flight mass spectrometry based method

Emerging innate biological properties of nano-drug delivery systems: A focus on PAMAM dendrimers and their clinical potential

Drug delivery systems or vectors are usually needed to improve the bioavailability and effectiveness of a drug through improving its pharmacokinetics/pharmacodynamics at an organ, tissue or cellular level. However, emerging technologies with sensitive readouts as well as a greater understanding of physiological/biological systems have revealed that polymeric drug delivery systems are not biologically inert but can have innate or intrinsic biological actions. In this article, we review the emerging multiple innate biological/toxicological properties of naked polyamidoamine (PAMAM) dendrimer delivery systems in the absence of any drug cargo and discuss their correlation with the defined physicochemical properties of PAMAMs in terms of molecular size (generation), architecture, surface charge and chemistry. Further, we assess whether any of the reported intrinsic biological actions of PAMAMs such as their antimicrobial activity or their ability to sequester glucose and modulate key protein interactions or cell signaling pathways, can be exploited clinically such as in the treatment of diabetes and its complications.

Cytotoxicity of Dendrimers

Drug delivery systems are molecular platforms in which an active compound is packed into or loaded on a biocompatible nanoparticle. Such a solution improves the activity of the applied drug or decreases its side effects. Dendrimers are promising molecular platforms for drug delivery due to their unique properties. These macromolecules are known for their defined size, shape, and molecular weight, as well as their monodispersity, the presence of the void space, tailorable structure, internalization by cells, selectivity toward cells and intracellular components, protection of guest molecules, and controllable release of the cargo. Dendrimers were tested as carriers of various molecules and, simultaneously, their toxicity was examined using different cell lines. It was discovered that, in general, dendrimer cytotoxicity depended on the generation, the number of surface groups, and the nature of terminal moieties (anionic, neutral, or cationic). Higher cytotoxicity occurred for higher-generation dendrimers and for dendrimers with positive charges on the surface. In order to decrease the cytotoxicity of dendrimers, scientists started to introduce different chemical modifications on the periphery of the nanomolecule. Dendrimers grafted with polyethylene glycol (PEG), acetyl groups, carbohydrates, and other moieties did not affect cell viability, or did so only slightly, while still maintaining other advantageous properties. Dendrimers clearly have great potential for wide utilization as drug and gene carriers. Moreover, some dendrimers have biological properties per se, being anti-fungal, anti-bacterial, or toxic to cancer cells without affecting normal cells. Therefore, intrinsic cytotoxicity is a comprehensive problem and should be considered individually depending on the potential destination of the nanoparticle.

Effects of PAMAM dendrimers with various surface functional groups and multiple generations on cytotoxicity and neuronal differentiation using human neural progenitor cells

Polyamidoamine (PAMAM) dendrimers have potential for biological applications as delivery systems for genes, drugs, and imaging agents into the brain, but their developmental neurotoxicity remains unknown. We investigated the effects of PAMAM dendrimers with various surface functional groups and multiple generations on neuronal differentiation using human neural progenitor cells at an equal mass concentration. Only PAMAM dendrimers containing amine (NH2) surface groups at concentrations of 10 μg/mL significantly reduced cell viability and neuronal differentiation, compared with non-amine-terminated dendrimers. PAMAM-NH2 with generation (G)3, G4, G5 G6, and G7 significantly decreased cell viability and inhibited neuronal differentiation from a concentration of 5 μg/mL, but G0, G1, and G2 dendrimers did not have any effect at this concentration. Cytotoxicity indices of PAMAM-NH2 dendrimers at 10 μg/mL correlated well with the zeta potentials of the particles. Surface group density and particle number in unit volume is more important characteristic than particle size to influence cytotoxicity for positive changed dendrimers. PAMAM-50% C12 at 1 μg/mL altered the expression level of the oxidative stress-related genes, ROR1, CYP26A1, and TGFB1, which is a DNA damage response gene. Our results indicate that PAMAM dendrimer exposure may have a surface charge-dependent adverse effect on neuronal differentiation, and that the effect may be associated with oxidative stress and DNA damage during development of neural cells.

Gd-Chelated poly(propylene imine) dendrimers with densely organized maltose shells for enhanced MR imaging applications

Gd-Chelated fourth generation poly(propylene imine) dendrimers with densely organized maltose shells can be designed for enhanced MR imaging applications.

Fate and transformation products of amine-terminated PAMAM dendrimers under ozonation and irradiation

This article deals with the degradation of a third-generation (G3) poly(amidoamine) (PAMAM) dendrimer under ozonation and irradiation. The identification and quantification of G3 PAMAM dendrimer and its transformation products has been performed by liquid chromatography-electrospray ionization-hybrid quadrupole time-of-flight-mass spectrometry. The dendrimer was completely depleted by ozone in less than 1 min. The effect of ultraviolet irradiation was attributed to hydroxyl-mediated oxidation. The transformation products were attributed to the oxidation of amines, which resulted in highly oxidized structures with abundance of carboxylic acids, which started from the formation of amine oxide and the scission of the CN bond of the amide group. We studied the toxicity of treated mixtures for six different organisms: the acute toxicity for the bacterium Vibrio fischeri and the microcrustacean Daphnia magna, the multigenerational growth inhibition of the alga Pseudokirchneriella subcapitata, and the seed germination phytotoxicity of Licopersicon esculentum, Lactuca sativa and Lolium perenne. Ozonation and irradiation originated transformation products are more toxic than the parent dendrimer. The toxicity of the dendrimer for the green alga was linked to a strong increase of intracellular reactive oxygen species with intense lipid peroxidation.

Quantitative determination of poly(amidoamine) dendrimers in urine by liquid chromatography/electrospray ionization hybrid quadrupole linear ion trap mass spectrometry

RATIONALE

Dendrimer nanocarriers have become of increasing interest in the field of biomedicine for their drug delivery potential. Surface modifications and optimized nanosize control are the strategies being followed to enhance drug delivery efficacy and renal clearance, especially for dendrimers of a lower generation number. The aim of this study was the development and performance evaluation of an analytical method for the quantitative determination of polyamidoamine (PAMAM) dendrimers in urine.

METHODS

PAMAM dendrimers (generations G0 to G3) were analyzed using liquid chromatography/electrospray ionization hybrid quadrupole linear ion trap mass spectrometry (LC/ESI-QqLIT-MS). Quantitative analysis was performed in selected reaction monitoring (SRM) mode. To confer a higher degree of confidence on the identification of PAMAM dendrimers, an SRM scan and collision-induced dissociation (CID), as a dependent scan, were performed in one single run using the information-dependent acquisition (IDA) mode.

RESULTS

The LC/ESI-QqLIT-MS method, in SRM mode, allowed quantitative determination in urine matrix with good repeatability and reproducibility (relative standard deviation (R.S.D.) from 2 to 15%), linearity (R >0.99) over the concentration range (6∙10^-4 to 5∙10^-2  mmol.L^-1 ), and sensitivity within the micromolar range. The detection limit values were above 1∙10^-4  mmol.L^-1 in both solvent and urine, for the generations studied.

CONCLUSIONS

The developed method has demonstrated a capability for the identification and quantification of PAMAM dendrimer nanoparticles in a complex liquid matrix. The use of an LC/ESI-QqLIT-MS system, of modest m/z range and unit resolution, offers an alternative in the analysis of lower generation PAMAM dendrimers between mass analyzers of higher resolution and the conventional LC-UV method that is commonly applied for dendrimer quantification, but which lacks sufficient identification capacity. Copyright © 2013 John Wiley & Sons, Ltd.

Identification and quantification of poly(amidoamine) PAMAM dendrimers of generations 0 to 3 by liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry in aqueous medium

RATIONALE

Poly(amidoamine) PAMAM dendrimers are highly water soluble and are used as flexible scaffolding or nanocontainers to conjugate, complex or encapsulate therapeutic drugs to overcome intrinsically weak characteristics such as solubilization in aqueous medium. To provide a reliable method for the quantitation of PAMAM dendrimers in aqueous medium, we report here a validation study which was developed in a complex wastewater matrix to evaluate the matrix effect in the electrospray ionization (ESI) source.

METHODS

PAMAM dendrimers (generations G0 to G3) were identified and quantitated in aqueous medium using liquid chromatography interfaced to a hybrid quadrupole/time-of-flight mass analyzer. This approach used the high resolving power of isotopic clusters and mass accuracy of the instrument, with especial attention to the tandem mass spectrometric (MS/MS) capabilities. The formation of multiply charged ions of PAMAM dendrimers in the ESI source and their later fragmentation allowed fragmentation paths to be determined and structural assignments to be made.

RESULTS

The analytical strategy allowed dendrimer identification with a high degree of confidence obtained by accurate mass and high resolution with mass errors below 5 ppm and 10 ppm in MS and MS/MS modes. The parameters of validation in spiked matrix were: limits of quantification in the range of 0.12 to 1.25 μM depending on the generation, linearity (R >0.996), repeatability (R.S.D. <6.7%) and reproducibility (R.S.D. <10.8%).

CONCLUSIONS

Accurate mass measurement, elemental composition, and charge state assignment through the resolution of isotopic clusters of product and precursor ions, confers enhanced confidence on PAMAM dendrimer characterization. This selectivity provided high discriminating capacity of PAMAM dendrimers against matrix interferences. Because of the reliable and reproducible quantitation by LC/ESI-QTOF-MS, analysis of PAMAM dendrimers in an aqueous matrix is feasible.