A novel quaternary ammonium chitosan hydrogel modified by poly（amidoamine）（PAMAM） dendrimer was prepared by using glutaraldehyde as a cross-linker. The hydrogel was characterized by Fourier transform infrared spec...A novel quaternary ammonium chitosan hydrogel modified by poly（amidoamine）（PAMAM） dendrimer was prepared by using glutaraldehyde as a cross-linker. The hydrogel was characterized by Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. The results confirmed its highly porous three-dimensional network structure. The swelling test of hydrogel proved that it had excellent swelling and p H-sensitive properties. The increasing PAMAM content or quaternization degree led to the increase in swelling properties. And the hydrogel with lower cross-linking agent concentration or quaternary ammonium chitosan concentration exhibited better swelling properties. The antibacterial results indicated that with the increase in the PAMAM content, quaternary ammonium chitosan concentration or cross-linking agent concentration, the hydrogels showed better antibacterial activities against both Staphylococcus aureus（S. aureus） and Escherichia coli（E. coli）. Thus, the hydrogel could serve as a promising antibacterial material in the future.展开更多
In order to control the size and shape of Ag nanoparticles obtained by using poly（amidoamine） （PA- MAM） dendrimer as template, the complexation between Ag^＋ ions and dendrimer studied extensively by UV-Vis spectr...In order to control the size and shape of Ag nanoparticles obtained by using poly（amidoamine） （PA- MAM） dendrimer as template, the complexation between Ag^＋ ions and dendrimer studied extensively by UV-Vis spectroscopy and FTIR. After the Ag＋/PAMAM demdrimer being reduced by direct chemical reduction, Ag （0） nanopartides was formed, whose structure and characterization were studied by UV-Vis spectroscopy, transmission electron microscopy （TEM） and electron diffraction （ED） respectively. The results reveal that Ag nanopartides is a kind of face center cubic crystal and its average size is 4.5 nm. The solubility and stability of the solution containing Ag nanopartides also indicate that dendrimer is a good kind of template, as well as a protective agent.展开更多
Tumor associated macrophages(TAMs)tend to exhibit tumor-promoting M2 phenotype and contribute to the development of immunosuppressive microenvironment of solid tumors.Reprograming TAMs from M2 into tumoricidal M1 phen...Tumor associated macrophages(TAMs)tend to exhibit tumor-promoting M2 phenotype and contribute to the development of immunosuppressive microenvironment of solid tumors.Reprograming TAMs from M2 into tumoricidal M1 phenotype is robust for stimulating tumor immunosuppressive microenvironment(TIME).In this study,we developed a poly(amidoamine)(PAMAM)derivative dendrimer(denoted as fourth generation-N,N-diethylaminoethyl(G4-DEEA))for efficient loading of Toll-like receptor 7 and 8(TLR7/8)agonist(R848)to remodel the TIME for potent cancer immunotherapy,G4-DEEA exhibited a high loading capacity of R848 up to 35.9 wt%by taking advantage of its dendritic structure.The resulting formulation(designated as G4-DEEA@R848)effectively polarized M2 macrophages into M1 phenotype in vitro,and improved the maturation and activation of antigen-presenting cells.In the 4T1 orthotopic breast cancer model,G4-DEEA@R848 showed a stronger tumor inhibitory effect than free drug.The mechanistic studies suggested that G4-DEEA@R848 could significantly stimulate the TIME by repolarizing TAMs into M1 phenotype,reducing the presence of immunosuppressive myeloid cells and increasing the infiltration of tumor cytotoxic T cells.This study provides a simple but effective dendrimer-based strategy to improve the formulation of R848 for improved cancer immunotherapy.展开更多
The interaction between amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) den-drimers and herring sperm DNA was investigated by various spectroscopic methods including UV spectroscopy, fluores-cence ...The interaction between amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) den-drimers and herring sperm DNA was investigated by various spectroscopic methods including UV spectroscopy, fluores-cence spectroscopy, microscopic FTIR- and circular dichro-ism (CD-) spectroscopy. Ethidium bromide (EB) is used as a nucleic acid probe for this study. Experimental results show that PAMAM dendrimers can form stable complexes with DNA and the dendrimers bind to DNA sufficiently strong which cannot be displaced by EB, and we also found that the formation of the complexes can cause the conformation change of the DNA secondary structure. According to the Scatchard analysis, the association constant of PAMAM to DNA is calculated to be 2.53 × 104 mol/L?1.展开更多
An inorganic-organic composite was prepared by poly（amidoamine） （PAMAM） dendrimer reacting with cobalt（Ⅱ）-monosubstituted polyoxometalates Na5Co^Ⅱ（H2O）PW11O39 （PW11CO） in an aqueous solution. The hybrid co...An inorganic-organic composite was prepared by poly（amidoamine） （PAMAM） dendrimer reacting with cobalt（Ⅱ）-monosubstituted polyoxometalates Na5Co^Ⅱ（H2O）PW11O39 （PW11CO） in an aqueous solution. The hybrid composite PW11Co/PAMAM was characterized by FT-IR, UV-Vis diffuse reflectance spectra （DR-UV-Vis）, XPS, XRD and TG/DTA, indicating that the PWI iCo was chemically anchored to PAMAM. The morphologies of the title composite were characterized by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The catalytic activity was evaluated by oxidation of isobutyraldehyde （IBA） to isobutyric acid （IBAc） in MeCN under mild conditions （20 ℃, ambient pressure）, showing that the title compound is a more effective and recoverable catalyst than corresponding PW11Co.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51303145,51273156,51373130)
文摘A novel quaternary ammonium chitosan hydrogel modified by poly（amidoamine）（PAMAM） dendrimer was prepared by using glutaraldehyde as a cross-linker. The hydrogel was characterized by Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. The results confirmed its highly porous three-dimensional network structure. The swelling test of hydrogel proved that it had excellent swelling and p H-sensitive properties. The increasing PAMAM content or quaternization degree led to the increase in swelling properties. And the hydrogel with lower cross-linking agent concentration or quaternary ammonium chitosan concentration exhibited better swelling properties. The antibacterial results indicated that with the increase in the PAMAM content, quaternary ammonium chitosan concentration or cross-linking agent concentration, the hydrogels showed better antibacterial activities against both Staphylococcus aureus（S. aureus） and Escherichia coli（E. coli）. Thus, the hydrogel could serve as a promising antibacterial material in the future.
文摘In order to control the size and shape of Ag nanoparticles obtained by using poly（amidoamine） （PA- MAM） dendrimer as template, the complexation between Ag^＋ ions and dendrimer studied extensively by UV-Vis spectroscopy and FTIR. After the Ag＋/PAMAM demdrimer being reduced by direct chemical reduction, Ag （0） nanopartides was formed, whose structure and characterization were studied by UV-Vis spectroscopy, transmission electron microscopy （TEM） and electron diffraction （ED） respectively. The results reveal that Ag nanopartides is a kind of face center cubic crystal and its average size is 4.5 nm. The solubility and stability of the solution containing Ag nanopartides also indicate that dendrimer is a good kind of template, as well as a protective agent.
基金supported by National Key R&D Program of China(No.2017YFA0205600)Guangdong Natural Science Funds for Distinguished Young Scholar(No.2017A030306018)+2 种基金National Natural Science Foundation of China(Nos.51922043 and 31771091)Guangdong Provincial Programs(Nos.2017ZT07S054 and 2017GC010304)the Science and Technology Program of Guangzhou(No.201902020018),and Fundamental Research Funds for Central Universities.
文摘Tumor associated macrophages(TAMs)tend to exhibit tumor-promoting M2 phenotype and contribute to the development of immunosuppressive microenvironment of solid tumors.Reprograming TAMs from M2 into tumoricidal M1 phenotype is robust for stimulating tumor immunosuppressive microenvironment(TIME).In this study,we developed a poly(amidoamine)(PAMAM)derivative dendrimer(denoted as fourth generation-N,N-diethylaminoethyl(G4-DEEA))for efficient loading of Toll-like receptor 7 and 8(TLR7/8)agonist(R848)to remodel the TIME for potent cancer immunotherapy,G4-DEEA exhibited a high loading capacity of R848 up to 35.9 wt%by taking advantage of its dendritic structure.The resulting formulation(designated as G4-DEEA@R848)effectively polarized M2 macrophages into M1 phenotype in vitro,and improved the maturation and activation of antigen-presenting cells.In the 4T1 orthotopic breast cancer model,G4-DEEA@R848 showed a stronger tumor inhibitory effect than free drug.The mechanistic studies suggested that G4-DEEA@R848 could significantly stimulate the TIME by repolarizing TAMs into M1 phenotype,reducing the presence of immunosuppressive myeloid cells and increasing the infiltration of tumor cytotoxic T cells.This study provides a simple but effective dendrimer-based strategy to improve the formulation of R848 for improved cancer immunotherapy.
文摘The interaction between amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) den-drimers and herring sperm DNA was investigated by various spectroscopic methods including UV spectroscopy, fluores-cence spectroscopy, microscopic FTIR- and circular dichro-ism (CD-) spectroscopy. Ethidium bromide (EB) is used as a nucleic acid probe for this study. Experimental results show that PAMAM dendrimers can form stable complexes with DNA and the dendrimers bind to DNA sufficiently strong which cannot be displaced by EB, and we also found that the formation of the complexes can cause the conformation change of the DNA secondary structure. According to the Scatchard analysis, the association constant of PAMAM to DNA is calculated to be 2.53 × 104 mol/L?1.
基金Project supported by the Natural Science Foundation of Fujian Province （No. E0510012） and a key item of Education Department of Fujian Province （No. JA04167）.Acknowledgements The authors thank professor Luo Yunjun and Li Guoping, School of Chemical Engineering and Materials Science, Beijing Institute of Technology for the support of PAMAM dendrimer compound.
文摘An inorganic-organic composite was prepared by poly（amidoamine） （PAMAM） dendrimer reacting with cobalt（Ⅱ）-monosubstituted polyoxometalates Na5Co^Ⅱ（H2O）PW11O39 （PW11CO） in an aqueous solution. The hybrid composite PW11Co/PAMAM was characterized by FT-IR, UV-Vis diffuse reflectance spectra （DR-UV-Vis）, XPS, XRD and TG/DTA, indicating that the PWI iCo was chemically anchored to PAMAM. The morphologies of the title composite were characterized by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The catalytic activity was evaluated by oxidation of isobutyraldehyde （IBA） to isobutyric acid （IBAc） in MeCN under mild conditions （20 ℃, ambient pressure）, showing that the title compound is a more effective and recoverable catalyst than corresponding PW11Co.
