HER2 targeted polyplexes: the effect of polyplex composition and conjugation chemistry on in vitro and in vivo characteristics

Surface functionalization allowing repetitive use of optical sensors for real-time detection of antibody-bacteria interaction

In this study, sensor surface functionalization allowing the repetitive use of a sensing device was evaluated for antibody-based detection of living bacteria using an optical planar Bragg grating sensor. To achieve regenerable immobilization of bacteria specific antibodies, the heterobifunctional cross-linker N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) was linked to an aminosilanized sensor surface and subsequently reduced to expose sulfhydryl groups enabling the covalent conjugation of SPDP-activated antibodies via disulfide bonds. The immobilization of a capture antibody specific for Staphylococcus aureus on the sensor surface as well as specific binding of S. aureus could be monitored, highlighting the applicability of optical sensors for the specific detection of large biological structures. Reusability of bacteria saturated sensors was successfully demonstrated by cleaving the antibody along with bound bacteria through reduction of disulfide bonds and subsequent re-functionalization with activated antibody, resulting in comparable sensitivity towards S. aureus.

Post-Transcriptional Regulation of the GASC1 Oncogene with Active Tumor-Targeted siRNA-Nanoparticles

Basal-like breast cancer (BLBC) accounts for the most aggressive types of breast cancer, marked by high rates of relapse and poor prognoses and with no effective clinical therapy yet. Therefore, investigation of new targets and treatment strategies is more than necessary. Here, we identified a receptor that can be targeted in BLBC for efficient and specific siRNA mediated gene knockdown of therapeutically relevant genes such as the histone demethylase GASC1, which is involved in multiple signaling pathways leading to tumorigenesis. Breast cancer and healthy breast cell lines were compared regarding transferrin receptor (TfR) expression via flow cytometry and transferrin binding assays. Nanobioconjugates made of low molecular weight polyethylenimine (LMW-PEI) and transferrin (Tf) were synthesized to contain a bioreducible disulfide bond. siRNA complexation was characterized by condensation assays and dynamic light scattering. Cytotoxicity, transfection efficiency, and the targeting specificity of the conjugates were investigated in TfR positive and negative healthy breast and breast cancer cell lines by flow cytometry, confocal microscopy, RT-PCR, and Western blot. Breast cancer cell lines revealed a significantly higher TfR expression than healthy breast cells. The conjugates efficiently condensed siRNA into particles with 45 nm size at low polymer concentrations, showed no apparent toxicity on different breast cancer cell lines, and had significantly greater transfection and gene knockdown activity on mRNA and protein levels than PEI/siRNA leading to targeted and therapeutic growth inhibition post GASC1 knockdown. The synthesized nanobioconjugates improved the efficiency of gene transfer and targeting specificity in transferrin receptor positive cells but not in cells with basal receptor expression. Therefore, these materials in combination with our newly identified siRNA sequences are promising candidates for therapeutic targeting of hard-to-treat BLBC and are currently further investigated regarding in vivo targeting efficacy and biocompatibility.

Synthesis of macromolecular systems via lipase catalyzed biocatalytic reactions: applications and future perspectives

This review highlights the application of lipases in the synthesis of pharmaceutically important small molecules and polymers for diverse applications.

Trends in polymeric delivery of nucleic acids to tumors

Delivery of nucleic acids to tumors has received extensive attention in the past few decades since these molecules are capable of treating disease by modulating the source of abnormalities. Although high efficiency and low toxicity of numerous delivery systems for nucleic acids have been approved frequently with in vitro assays, contradictions have been observed in many cases between these results and what has occurred in the dynamic in vivo situation. Filling this gap seems to be crucial for further preclinical development of such systems. In this paper, we discuss various barriers which polymeric DNA or siRNA nanoparticles encounter upon systemic administration with an aim to assist in designing more relevant in vitro assays. Furthermore, individual considerations concerning delivery of DNA and siRNA have been addressed.

Self-assembled supramolecular nano vesicles for safe and highly efficient gene delivery to solid tumors

The main obstacles for cationic polyplexes in gene delivery are in vivo instability and low solid-tumor accumulation. Safe vectors with high transfection efficiency and in vivo tumor accumulation are therefore highly desirable. In this study, the amphiphilic block copolymer poly(n-butyl methacrylate)-b-poly(N-acryloylmorpholine) was synthesized by reversible addition–fragmentation chain-transfer (RAFT) radical polymerization. The corresponding well-defined vesicles with narrow size distribution were tailored by finely regulating the packing parameter (β) of copolymer (1/2 < β < 1). Compared with traditional “gold-standard” polycation (polyethylenimine, 25 kDa), plasmid DNA condensing efficiency, DNase I degradation protection, and cellular uptake were improved by the supramolecular nano vesicles. In addition, the plasmid DNA transferring efficiency in 10% fetal bovine serum medium was enlarged five times to that of polyethylenimine in renal tubular epithelial and human hepatocellular carcinoma cell lines. This improved in vitro transfection was mainly attributed to the densely packed bilayer. This stealth polyplex showed high serum stability via entropic repulsion, which further protected the polyplex from being destroyed during sterilization. As indicated by the IVIS^® Lumina II Imaging System (Caliper Life Sciences, Hopkinton, MA) 24 hours post-intravenous administration, intra-tumor accumulation of the stealth polyplex was clearly promoted. This study successfully circumvented the traditional dilemma of efficient gene transfection at a high nitrogen-from-polyethylenimine to phosphate-from-DNA ratio that is accompanied with site cytotoxicity and low stability. As such, these simply tailored noncytotoxic nano vesicles show significant potential for use in practical gene therapy.

Physicochemical and biological evaluation of siRNA polyplexes based on PEGylated Poly(amido amine)s

PURPOSE

Use of RNA interference as novel therapeutic strategy is hampered by inefficient delivery of its mediator, siRNA, to target cells. Cationic polymers have been thoroughly investigated for this purpose but often display unfavorable characteristics for systemic administration, such as interactions with serum and/or toxicity.

METHODS

We report the synthesis of a new PEGylated polymer based on biodegradable poly(amido amine)s with disulfide linkages in the backbone. Various amounts of PEGylated polymers were mixed with their unPEGylated counterparts prior to polyplex formation to alter PEG content in the final complex.

RESULTS

PEGylation effectively decreased polyplex surface charge, salt- or serum-induced aggregation and interaction with erythrocytes. Increasing amount of PEG in formulation also reduced its stability against heparin displacement, cellular uptake and subsequent silencing efficiency. Yet, for polyplexes with high PEG content, significant gene silencing efficacy was found, which was combined with almost no toxicity.

CONCLUSIONS

PEGylated poly(amido amine)s are promising carriers for systemic siRNA delivery in vivo.

Triazine dendrimers as nonviral gene delivery systems: effects of molecular structure on biological activity

A family of generation 1, 2, and 3 triazine dendrimers differing in their core flexibility was prepared and evaluated for their ability to accomplish gene transfection. Dendrimers and dendriplexes were analyzed by their physicochemical and biological properties such as condensation of DNA, size, surface charge, morphology of dendriplexes, toxic and hemolytic effects, and ultimately transfection efficiency in L929 and MeWo cells. Flexibility of the backbone was found to play an important role with generation 2 dendrimer displaying higher transfection efficiencies than 25 kDa poly(ethylene imine) or SuperFect at a lower cytotoxicity level. This result is surprising, as PAMAM dendrimers require generations 4 or 5 to become effective transfection reagents. The ability to delineate effects of molecular structure and generation of triazine dendrimers with biological properties provides valuable clues for further modifying this promising class of nonviral delivery system.

Stability of siRNA polyplexes from poly(ethylenimine) and poly(ethylenimine)-g-poly(ethylene glycol) under in vivo conditions: effects on pharmacokinetics and biodistribution measured by Fluorescence Fluctuation Spectroscopy and Single Photon Emission Computed Tomography (SPECT) imaging

In search of optimizing siRNA delivery systems for systemic application, one critical parameter remains their stability in blood circulation. In this study, we have traced pharmacokinetics and biodistribution of each component of siRNA polyplexes formed with polyethylenimine 25 kDa (PEI) or PEGylated PEIs by in vivo real-time gamma camera recording, SPECT imaging, and scintillation counting of blood samples and dissected organs. In vivo behavior of siRNA and polymers were compared and interpreted in the context of in vivo stability of the polyplexes which had been measured by fluorescence fluctuation spectroscopy (FFS). Both pharmacokinetics and biodistribution of polymer-complexed siRNA were dominated by the polymer. PEGylated polymers and their siRNA polyplexes showed significantly less uptake into liver (13.6-19.7% ID of PEGylated polymer and 9.5-10.2% ID of siRNA) and spleen compared to PEI 25 kDa (liver deposition: 36.2% ID of polymer and 14.6% ID of siRNA). With non-invasive imaging methods we were able to predict both kinetics and deposition in living animals allowing the investigation of organ distribution in real time and at different time points. FFS measurements proved stability of the applied polyplexes under in vivo conditions which explained the different behavior of complexed from free siRNA. Despite their stability in circulation, we observed that polyplexes dissociated upon liver passage. Therefore, siRNA/(PEG-)PEI delivery systems are not suitable for systemic administration, but instead may be useful when the first-pass effect is circumvented, which is the case in local application.

Evaluation of pharmacokinetics of bioreducible gene delivery vectors by real-time PCR

PURPOSE

To investigate pharmacokinetics of reversibly stabilized DNA nanoparticles (rSDN) using a single-step lysis RT-PCR.

METHODS

rSDN were prepared by coating bioreducible polycation/DNA polyplexes with multivalent N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers. Targeted polyplexes were formulated by linking cyclic RGD ligand (c(RGDyK)) to the HPMA surface layer of rSDN. The pharmacokinetic parameters in tumor-bearing mice were analyzed by PKAnalyst.

RESULTS

The pharmacokinetics of naked plasmid DNA, simple DNA polyplexes, rSDN, and RGD-targeted rSDN exhibited two-compartment model characteristics with area under the blood concentration-time curve (AUC) increasing from 1,102 ng x ml(-1) x min(-1) for DNA to 3,501 ng x ml(-1) x min(-1) for rSDN. Non-compartment model analysis revealed increase in mean retention time (MRT) from 4.5 min for naked DNA to 22.9 min for rSDN.

CONCLUSIONS

RT-PCR is a sensitive and convenient method suitable for analyzing pharmacokinetics and biodistribution of DNA polyplexes. Surface stabilization of DNA polyplexes can significantly extend their MRT and AUC compared to naked DNA. DNA degradation in rSDN in blood circulation, due to a combined effect of disulfide reduction and competitive reactions with charged molecules in the blood, contributes to DNA elimination.