Electrochemistry of polyamidoamine dendrimers ester gel electrolytes

This paper described the first example of polyamidoamine dendrimers ester(PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as aplasticizer. The polymer films are solid and sticky. Background cyclic voltammetry (CV) shows apotential window between +0.7 and -0.7 V vs. Ag/AgCl. The voltammetry of ferrocene and7,7,8,8-tetracyanoquinodimethane (TCNQ) indicates that diffusion coefficients are in the range of10^(-8) -10^(-9) cm^2/s. Ionic conductivities are approximately 10^(-6) S/cm. Similar films usingdimethyl sulfoxide (DMSO) as a plasticizer instead of MPEG-400 have demonstrated ionicconductivities of 10^(-4) S/cm and reversible voltammetry. However, UV spectropho-tometry shows that70% of the DMSO is lost under vacuum, indicating the difficulty in quantifying the DMSO contentwhen exposed to vacuum.

Low generational polyamidoamine dendrimers to enhance the solubility of folic acid:A‘‘dendritic effect’’investigation

Low generational（G0–G2,G for generation） polyamidoamine（PAMAM） dendrimers were investigated as enhancers to improve the aqueous solubility of folic acid at pH 11 and pH 5.In these two cases,the solubility of folic acid increases with both the dendrimer concentration and generation.However,the solubilization mechanism is different.The electrostatic interaction between the primary amines of dendrimers and the ionized carboxylic groups of folic acid dominates the dissolution process at pH 11 while the increase of the solubility of folic acid at pH 5 is attributed to the hydrophobic encapsulation inside the dendrimer molecules.In addition,for comparison ethylenediamine was used as a small molecule control to examine the ‘‘dendritic effect＇＇ in the dendrimer-related solubilization process.Interestingly,PAMAM dendrimers exhibit,at pH 5,a significant superiority over ethylenediamine in enhancing solubility,whereas this ‘‘dendritic effect＇＇ cannot be observed under the basic condition.

A new strategy of enhancing absorptivity and safety for evodiamine: polyamidoamine derivatives modified by polyethylene glycol chain

Background:Traditional Chinese medicine involves complex ingredients and mixtures of ingredients that often exhibit low bioavailability,and excipients are often lacking to increase the absorption-enhancing effects.This study modified the generation 4 polyamidoamine dendrimer with polyethylene glycol of different molecular weights(5000,2000,1000)to form a series of polyamidoamine-co-polyethylene glycol(PAMAM-co-PEG)as a novel class of oral absorption enhancers.Evodiamine,the major alkaloid found in the traditional Chinese medicine Wu Zhu Yu(Fructus Evodiae),was used as a model drug to verify the absorption-enhancing effects and the safety of this alkaloid.Methods:This study utilized the solubility determination method documented in the Pharmacopoeia of the People’s Republic of China(2015 edition)and the D0 values recommended in the US FDA guidelines to comprehensively evaluate the solubility of evodiamine.The permeability of evodiamine was assessed using the apparent permeability coefficient in experiments based on in vitro cell models.Multiple aspects of the biological safety of PAMAM-co-PEG were explored using the MTT assay,LDH assay,and total protein release of the rat intestinal tract.Moreover,the absorption-enhancing effects of PAMAM-co-PEG at different molecular weights on evodiamine were verified via the use of in vitro cell models and in vivo intestinal loop circulation experiments with rats.Results:Evodiamine exhibited low solubility and permeability and was classified into class IV compounds using the biopharmaceutical classification system.PAMAM-co-PEG 2000 demonstrated improvement in the biosafety and absorption-enhancement effect of evodiamine at a specific concentration.This study showed that 0.05%(w/v)of PAMAM-co-PEG 2000 increased the cumulative penetration of evodiamine via cell transport by 1.32 times,and 0.10%(w/v)of PAMAM-co-PEG 2000 increased the area under curve value of evodiamine by 1.31 times.Conclusion:Evodiamine possesses low solubility and permeability and leads to poor oral bioavailability and a certain degree of cytotoxicity.PAMAM-co-PEG 2000 was found to be a potentially safe and efficient oral absorption enhancer.The results of this study might create a foundation for the development of novel excipients suitable for the complex active ingredients of traditional Chinese medicine.

Design of Dendrimer Modified Carbon Nanotubes for Gene Delivery

To investigate the efficiency of polyamidoamine dendrimer grafted carbon nanotube （dendrimer-CNT） mediated entrance of anti-survivin oligonucleotide into MCF-7 cells, and its effects on the growth of MCF-7 cells. Methods： Antisense survivin oligonucleotide was anchored onto polyamidoamine dendrimer grafted carbon nanotubes to form dendrimer-CNT-asODN complex and the complex was characterized by Zeta potential, AFM, TEM, and 1% agarose gel electrophoresis analysis. Dendrimer-CNT-asODN complexes were added into the medium and incubated with MCF-7 cells. MTT method was used to detect the effects of asODN and dendrimer-CNT-asODN on the growth of MCF-7 cells. TEM was used to observe the distribution of dendrimer-CNT-asODN complex within MCF-7 cells. Results： Successful synthesis of dendrimer-CNT-asODN complexes was proved by TEM, AFM and agarose gel electrophoresis. TEM showed that the complexes were located in the cytoplasm, endosome, and lysosome within MCF-7 cells. When dendrimer-CNT-asODN （1.0 μmol/L） and asODN （1.0 μmol/L） were used for 120 h incubation, the inhibitory rates of MCF-7 cells were （28.22±3.5）% for dendrimer-CNT-asODN complex group, （9.23±0.56）% for only asODN group, and （3.44±0.25）% for dendrimer-CNT group. Dendrimer-CNT-asODN complex at 3.0 μmol/L inhibited MCF-7 cells by （30.30±10.62）%, and the inhibitory effects were in a time- and concentration-dependent manner. Conclusion： Dendrimer-CNT nanoparticles may serve as a gene delivery vector with high efficiency, which can bring foreign gene into cancer cells, inhibiting cancer cell proliferation and markedly enhancing the cancer therapy effects.

TGA/Chemometrics addressing innovative preparation strategies for functionalized carbon nanotubes

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.

Polymer nanoparticles with dendrimer-Ag shell and its application in catalysis

Polymer nanoparticles with dendrimer-Ag shell were prepared and their application in catalytic reduction of 4-nitrophenol （4-NP） was investigated. Cross-linked polystyrene （PS） microspheres were prepared through dispersion copolymerization of styrene, acrylic acid and crosslinking monomer 1, 2- divinylbenzene. PS microspheres with average size of 450 nm and narrow size distribution were used as support for the immobilization of dendrimer-Ag shell, The polyamidoamine （PAMAM） dendrimer shell was successively grafted onto the surface ofPS microspheres through repetitive Michael addition reaction of methyl acrylate （MA） and amidation of the obtained esters with large excess of ethylenediamine （EDA）. Silver nanoparticles were formed directly inside the PAMAM shell through reduction with NaBH4. The resulting PS@PAMAM-Ag nanopartides were packed in a stainless steel column and used successfully for catalytic reduction of 4-NP. This technique for packing catalytic polymer particles in a column could imnrove the efficiency of using the metal catalyst and the tedious seuaration in catalytic reaction.