Interaction Mechanism of Nano-silicon Dioxide Modified by Poly（amidoamine） Dendrimers

To gain insight into the attachment of =Si^＋ （SC） ion （regarded as guest） to the lowest generation, NH2-terminated poly（amidoamine） （PAMAM） dendrimers （regarded as host） in the liquid phase, density functional theory is used to investigate the structures and energetics of the host-guest complex. The effect of solvent on the structures and energetics is also investigated. Various initial configurations of the ion bound to PAMAM are tested, and two stable conformers are found, i.e, types A （=Si^＋ is bound to the amine site） and C （=Si^＋ is bound to the amide site）. Types A and C are the most stable due to the chemical bond formations of Si-N° （amine nitrogen atoms） and Si-O, respectively. The IR spectra for the lowest energy conformers are thoroughly analyzed and compared with the available experimental data.

Preparation and Properties of Poly(amidoamine) Dendrimer/Quaternary Ammonium Chitosan Hydrogels

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.

A polyamidoamine(PAMAM)derivative dendrimer with high loading capacity of TLR7/8 agonist for improved cancer immunotherapy

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.

A Novel Inorganic-Organic Composite Constructed from Cobalt（Ⅱ）-Monosubstituted Polyoxometalates and Poly（amidoamine）-NH2 Dendrimers

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.

Dendrimer Templates for the Formation of Silver Nanoparticles

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.

Synthesis of poly(amidoamine)-poly(ethyleneglycol)-poly(amidoamine) and preparation of its hydrogel solution containing doxorubicin

Many pH-and temperature-responsive polymers have been designed for preparing hydrogel.In the present study,in order to decrease the pH sensitivity of reported poly(amidoamine)-poly(ethyleneglycol)-poly(amidoamine)(PAA1580-PEG4600-PAA1580),we designed and synthesized poly(amidoamine)-poly(ethyleneglycol)-poly(amidoamine)(PAA-PEG-PAA)with shorter length of PAA chain by decreasing reaction temperature for preparing PAA-PEG-PAA hydrogel solution containing doxorubicin(DOX).The PAA-PEG-PAA was synthesized via the Michael-addition polymerization.The characteristic of PAA-PEG-PAA was evaluated.The PAA-PEG-PAA hydrogel solution was prepared and investigated.DOX-loaded PAA-PEG-PAA hydrogel solution was prepared,and its in vitro DOX release and in vitro anti-tumor activity were evaluated.Our results indicated that the viscosity of PAA-PEG-PAA hydrogel solution was concentration-and temperature-dependent.The sol-gel transition temperature of PAA-PEG-PAA hydrogel solution(12%,w/w)ranged from 35 to 29℃,and its pH ranged from 6.0 to 7.4.The released DOX from DOX-loaded PAA-PEG-PAA hydrogel showed sustained release characteristics.The in vitro anti-tumor activity of DOX-loaded PAA-PEG-PAA hydrogel was confirmed in B16 F10 cell line.Considering the acidic tumor microenvironment,this DOX-loaded PAA-PEG-PAA hydrogel solution would be easy in situ administration for intra-tumor injection or para-tumor injection forming hydrogel at body temperature.We suggested that this DOX-loaded PAA-PEG-PAAhydrogel solution,if containing photothermal conversion agents,would have a potential further use for photothermal therapy.

Investigation on Ligand Exchange Kinetics on CdSe/ZnS Quantum Dot Surface Utilizing Pyrene as Flourescent Probe

Direct ligand exchange kinetics between hydrophilic molecules and quantum dots（QDs） was investigated. Meanwhile, pyrene was exploited as probe to detect the efficiency of the ligand exchange reaction between octade- cylamine-coated QDs（ODA-QDs） and different ligands[ligand 1： NH2G3-OH, ligand 2： G4.5-PEG5-FA5, ligand 3： （COOH）2G3-OH or ligand 4： G4.5-PEG1-FAl]. It was indicated that water-soluble QDs exhibit the same fluores- cence and absorption spectra as ODA-QDs when they were dissolved in chloroform. Furthermore, the cellular expe- riments demonstrated that the folic acid（FA） targeting poly（amidoamine）（PAMAM） modified QD conjugates could be used as molecular targeting sensing systems for nanoparticle probes.

Quantum Chemical Studies of Host-guest Nanostructures of PAMAM Dendrimers in Drug Deliver

Using B3LYP and M06-2X functionals,eight noncovalent configurations for the adsorption of D-penicillamine drug(DPA)drug on poly(amidoamine)G0 generation dendrimer(PAMAMG0)carrier have been investigated.The quantum molecular descriptors and the binding and solvation energies were examined in aqueous solution and gas phase.The binding energies demonstrated the energetic stability of non-bonded species(PAMAMG0/DPA1-8).The solvation energies showed that solubility of DPA rises in the vicinity of PAMAMG0 carrier which is a fundamental factor for applicability of a carrier.Considering quantum molecular descriptors such as electrophilicity power and global hardness,the toxicity of DPA drug in the vicinity of PAMAMG0 carrier decreases and drug release is facilitated.The AIM analysis for all PAMAMG0/DPA1-8 structures indicated that the hydrogen and pseudo-hydrogen bonds play important roles in the functionalization of PAMAMG0 with DPA drug.The configuration in which DPA drug interacts simultaneously with two-NH2 functional groups of PAMAMG0 is the most stable configuration.

Synthesis and Characterization of Dendrimer-Encapsulated Bimetallic Core-Shell PdPt Nanoparticles

Using a successive method, PAMAM dendrimer-encapsulated bimetallic PdPt nanoparticles have been successfully prepared with core-shell structures （Pd@Pt DENs）. Evidenced by UV-vis spectra, high resolution trans- mission electron microscopy, and X-ray energy dispersive spectroscopy （EDS）, the obtained Pd@Pt DENs are monodispersed and located inside the cavity of dendrimers, and they show a different structure from monometallic Pt or Pd and alloy PdPt DENs. The core-shell structure of Pd@Pt DENs is further confirmed by infrared measure- ments with carbon monoxide （IR-CO） probe. In order to prepare Pd@Pt DENs, a required Pd/Pt ratio of 1 ： 2 is de- termined for the Pt shell to cover the Pd core completely. Finally, a mechanism for the formation of Pd@Pt DENs is proposed.