ABSTRACT
In this work, functionalized carbon nanotubes (CNTs) using two polyamine polymers, polyethyleneimine (PEI) and polyamidoamine dendrimer (PAMAM), were investigated by thermal analysis in order to address preparation strategies to obtain low cytotoxic compounds with the ability to conjugate micro-RNAs and, at the same time, to transfect efficiently endothelial cells. Thermogravimetric analysis (TGA) was coupled to chemometrics as a novel analytical strategy to characterize functionalized CNTs from different preparation conditions. In particular, two starting materials were considered:very small CNTs and carboxylated CNTs (CNT-COOH) in order to examine the affinity with polymers. Chemometrics permitted to compare results from TGA and to investigate the effect of a number of factors affecting the synthesis of coated nanotubes including a different amount of involved polymer and the time required for the suspension for a satisfactory and reproducible preparation procedure. The results demonstrated the effectiveness of TGA as a tool able to address synthesis of coated CNTs to be employed as efficient drug delivery vectors in biomedical applications.
ABSTRACT
This study demonstrates efficacy of a novel polyamidoamine dendrimers (PAMAM dendrimers) with pentaerythritol derivatives as the core (G5 PD dendrimer) in deliver of the cytosine deaminase (CD) gene and EGFP gene fusion plasmid into different tumor cell lines to induce apoptosis. The physical and chemical properties of G5 PD dendrimers in terms of DNA complexation, particulate properties and transfection efficiencies were investigated and compared with commercial gene vectors PEI 25 kDa. The optimum ratio of G5 PD dendrimer complexed with plasmid DNA was 0.2:1, and the particle size of the complex was (100±5) nm. Compared with the commercial gene carriers PEI, G5 PD dendrimer exhibited a higher transfection efficiency at the weight ratio of 1:1 in three different cell lines, given the fact that PEI are different from PAMAM dendrimers in terms of molecular structure. Furthermore, the cytotoxicity assays of the cell lines transfected with G5 PD dendrimer/pCD-EGFP-N1 followed by exposure to various concentrations of 5-fluorocytosine (5-FC) also showed that the transfected cell lines could generate a very low amount of 5-FC to 5-fluorouracil (5-FU) in a short period of time, which indicating the high expression level of CD gene in the cell line. These results indicate that the CD/5FC system of G5 PD dendrimer has an excellent efficacy in gene delivery.
ABSTRACT
Objective:To evaluate the sealing ability of the 3.0th generation of polyamidoamine dendrimer(3.0 PAMAM)on hu-man dentinal tubules.Methods:1 6 extracted premolars were cut into 2 mm thick dentin slices to establish sensitive dentin model in vitro.Then 2 samples without any treatment were selected randomly into demineralized dentin group,and the remain 1 4 dentine pills were divided into 2 groups by the random number table(n=7).Samples in the experimental group were treated with 3.0 PAMAM, those in the control group were treated with deionized water.After having immersed in the artificial saliva for 2 and 4 weeks respec-tively,the dentin slices were examined by scanning electron microscope(SEM)and X-ray energy dispersive spectroscopy(EDS). Results:SEM showed that the minerals on the surfaces of the dentine disks in experimental group were formed gradually with the time,the dentinal tubules were blocked 4 weeks after treatment.The minerals on the sample surface in control group were less and the dentinal tubules remained open.EDS results showed that Ca/P(1 .49 ±0.1 6)of mineral deposition in the experimental group was higher than that in the control group (1 .1 8 ±0.20)(P<0.05).Conclusion:The 3.0th generation of PAMAMhas the occlu-ding ability by inducing remineralization on the dentine surface and it may be used in the treatment of dentin hypersensitivity.
ABSTRACT
Objective:To use polyamidoamine(PAMAM)dendrimer as gene delivery system for survivin gene anti- sense oligodeoxynucleotide(asODN)transfection for inhibition of HepG2 cancer cell growth.Methods:The first to the fifth generation of PAMAM and asODN were used to prepare a complex:PAMAM-asODN.The morphology of PAMAM- asODN was observed using agrose electrophoresis and atomic force microscope(AFM).PAMAM-asODN was then used to transfect HepG2 cells and cells transfected with asODN served as control.The transfection efficacy of PAMAM-asODN into HepG2 cells was observed under confocol microscope,the surviving mRNA expression was analyzed by RT-PCR,and the inhibition of HepG2 cell growth was determined by MTT assay.Results:Agrose electrophoresis showed strong complexing action between PAMAM and asODN and they formed a complex with a diameter of 25 nm.Confocol microscope showed the transfection efficacy of PAMAM-asODN was higher than that of asODN.RT-PCR showed a decreased expression of sur- vivin mRNA in PAMAM-asODN transfected cells.MTF results demonstrated that the growth of HepG2 cell was obviously inhibited after transfection of PAMAM-asODN and the inhibition rate increased with culture time,concentration of com- plex,the generation of PAMAM.PAMAM-asODN at 6.0?mol/L G4.0 resulted in a 55% inhibition of HepG2 cells 96 h after culture.Conclusion:PAMAM dendrimers can efficiently mediate the entry of survivin asODN into HepG2 cells,re- sulting in inhibition of HepG2 cells.PAMAM might be a promising gene carrier for potential molecular therapy of cancer.