In vitro and in vivo double-enhanced suicide gene therapy mediated by generation 5 polyamidoamine dendrimers for PC-3 cell line

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material.

Antiproliferative effect of double suicide gene delivery mediated by polyamidoamine dendrimers in human Tenon's capsule fibroblasts

The aim of the present study was to investigate the therapeutic potential of a double suicide gene, thymidine kinase (TK) combined with cytosine deaminase (CD), mediated by generation of 5-polyamidoamine dendrimers (G5-PAMAM-D) on human Tenon's capsule fibroblasts (HTFs) as an anti-scarring agent. The pAcGFP1-Hyg-TK-CD plasmid was transfected into HTFs, and reverse-transcription polymerase chain reaction (RT-PCR) was used to detect TK-CD expression. MTT cell proliferation assay was used to evaluate the cytotoxic effects of ganciclovir (GCV) and 5-flurocytosine (5-FC) on HTFs. The optimal concentration of GCV and 5-FC in TK-CD transfected HTFs (HTF-TK-CD) was selected by accessing the lowest and highest cytotoxicity caused, respectively. The morphological changes of transfected HTFs following treatment with GCV and 5-FC were observed by light and transmission electron microscopy. Results demonstrated that the double suicide gene TK-CD mediated by the G5-PAMAM-D delivery system was successfully expressed in HTFs as determined by RT-PCR. A concentration of 3 µg/ml GCV and 200 µg/ml 5-FC was identified as optimal for these prodrugs. The growth rate and number of HTF-TK-CD cells decreased following treatment with GCV and 5-FC as revealed by light microscopy. Additionally, the prodrugs GCV and 5-FC not only demonstrated toxicity on transfected HTFs but also exerted a 'bystander effect'. The present study illustrated that the double suicide gene TK-CD delivery mediated by G5-PAMAM-D was effective in reducing HTF proliferation and inducing cell apoptosis. Furthermore, TK-CD delivery mediated by G5-PAMAM-D may be used as an anti-scarring agent and provide a therapeutic potential for patients requiring glaucoma filtration surgery.

The influence of maltotriose-modified poly(propylene imine) dendrimers on the chronic lymphocytic leukemia cells in vitro: dense shell G4 PPI

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Europe and North America. For many years scientists and doctors have been working on introducing the most effective therapy into CLL as prognosis of survival time and the course of the disease differ among patients, which might pose a problem in treating. Nanotechnology is providing new insights into diagnosis and, compared with conventional treatments, more efficient treatments, which might improve patients' comfort by decreasing side effects. Among the various nanoparticles that are available, dendrimers are one of the most promising. The aim of this study was a preliminary assessment of the clinical value of treating CLL patients with fourth generation poly(propylene imine) (PPI) dendrimers-either unmodified (PPI-G4) or approximately 90% maltotriose-modified (PPI-G4-DS-Mal-III). PPI-G4-DS-Mal-III dendrimers have, in contrast to the cationic PPI-G4, a neutral surface charge and are characterized by low cyto-, geno-, and hematotoxicity in vitro and in vivo. For the in vitro study we used blood mononuclear cells collected from both untreated CLL patients and from healthy donors. Apoptosis was measured by an annexin-V (Ann-V)/propidium iodide (IP) assay, and mitochondrial membrane potential was estimated with use of Mito Tracker Red CMXRos. Presented results confirm the influence of dendrimers PPI-G4 and PPI-G4-DS-Mal-III on apoptosis and CLL lymphocytes viability in in vitro cultures. Both tested dendrimers demonstrated higher cytotoxicity to CLL cells than to healthy donors cells, whereas unmodified dendrimers were more hematotoxic. The surface modification clearly makes glycodendrimers much more suitable for biomedical applications than unmodified PPI-G4; therefore further biological evaluations of these nanoparticles are conducted in our laboratories.