Adhesive peptides conjugated PAMAM dendrimer as a coating polymeric material enhancing cell responses

This present work aims to functionalize poly（amidoamine） （PAMAM） dendrimers with various reported adhesive peptides, including Arg-Gly-Asp （RGD）, Tyr-lle-Gly-Ser-Arg （YIGSR）, and Ile-Lys-Val-Ala-Val （IKVAV） for enhancing cell responses. The RGD, YIGSR, or IKVAV functionalized PAMAM coated substrate could promote cell adhesion of bone marrow mesenchymal stem cells （BMSCs） within 1 h after incubation. The neurite differentiation and proliferation of pheochromocytoma （PC12） cells were also significantly enhanced after culturing on the peptide functionalized PAMAM dendrimers for two and foul days. This peptide functionalized PAMAM dendrimers are considered as the potential candidates for various tissue engineering applications.

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.

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.

基于树状PAMAM修饰的PDMS微流控芯片分离检测两种蛋白质

为提高聚二甲基硅氧烷(PDMS)微流体芯片的亲水性,抑制其对蛋白质的吸附,利用树状PAMAM通过物理涂覆的手段对其微通道的表面进行了修饰。对修饰后PDMS微流控芯片的亲水性和电渗流进行了考察,同时利用修饰后芯片对溶菌酶,核糖核酸酶A两种蛋白质进行了分离检测。结果表明,修饰后的PDMS微流控芯片微通道表面形成了一层均匀、稳定的亲水性涂层,有效抑制了对蛋白质的吸附,成功地对溶菌酶和核糖核酸酶A实现了分离,柱效分别达到6.93×10^(4) plates/m和7.92×10^(4) plates/m,同时修饰后的芯片具有良好的重现性和较长的使用寿命。

Preparation, Swelling and Antibacterial Behaviors of N-Succinyl Chitosan-g-Poly(Acrylic Acid-co-Acrylamide) Superabsorbent Hydrogels

Superabsorbent hydrogels were prepared successfully from N-succinyl chitosan grafted poly（acrylic acid-co-acrylamide）. The potassium persulfate（KPS）, N, N＇-methylenebisacrylamide（MBA） were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM） were used to confirm the porous network structure of superabsorbent hydrogel. The effects of reaction parameters on the swelling behaviors of the superabsorbent hydrogels were investigated. The results indicated that water absorbency increased first, and then decreased gradually with the increase in the contents of monomer（AA＋AM）, KPS, MBA or acrylamide. The product had excellent water absorbency of 1375 g/g in distilled water and 83 g/g in 0.9wt% NaCl solution. Simultaneously, the superabsorbent hydrogels were p H sensitive. The antibacterial activities of the hydrogels against Escherichia coli（E. coli） were improved effectively because of polyamidoamine（PAMAM） dendrimer absorbed in the hydrogels.

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.

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.

Magnetic polyamidoamine dendrimers for magnetic separation and sensitive determination of organochlorine pesticides from water samples by high-performance liquid chromatography

Organochlorine pesticides(OCPs)have received much attention due to their toxicity.Reliable methods to monitor their residues in the environment are needed.Here,magnetic polyamidoamine dendrimers were prepared by co-precipitation,Michael addition,and amidation.The magnetic polyamidoamine dendrimers demonstrated good adsorption ability for OCPs—this feature was utilized to construct a sensitive tool for monitoring OCPs in water samples.The proposed method provided remarkable linearity from 0.1 to 500μg/L and satisfactory limits of detection from 0.012 to 0.029μg/L.The spiked recoveries of the four target analytes were 91.8%-103.5%with relative standard deviations less than 4.5%.The magnetic materials had good reusability.The results indicated that the resulting method was an efficient,easy,rapid,economical,and eco-friendly tool for monitoring OCPs in aqueous samples.

Adsorption performance and mechanism of Schiff base functionalized polyamidoamine dendrimer/silica for aqueous Mn(Ⅱ) and Co(Ⅱ)

Schiff base functionalized polyamidoamine(PAMAM) dendrimer/silica were prepared for the adsorption of aqueous Mn(Ⅱ) and Co(Ⅱ).The effects that influence the adsorption were investigated systematically and the adsorption mechanism was illustrated by theoretical calculation.The optimum adsorption pH are 4 and 6 for Mn(II) and Co(Ⅱ).Adsorption kinetics follow pseudo-second-order model and the ratecontrolling step is film diffusion process.Adsorption isotherm shows that high initial metal ion concentration facilitates the uptake of metal ions.The adsorption capacity increases first and then decreases in the temperature range of 15-35℃.Density functional theory(DFT) calculation demonstrates that Schiff base functionalized PAMAM dendrimer tends to coordinate Mn(Ⅱ) and Co(Ⅱ) with the oxygen atoms of hydroxyl and carbonyl groups,nitrogen of tertiary amine and imino groups.The imino and tertiary amine groups mainly dominate the adsorption.The reproducibility of the adsorbents indicates they can be regenerated by 5% thiourea and 0.5 mol/L HNO_(3) solution efficiently.

Adsorption of aqueous Cu(Ⅱ) and Ag(Ⅰ) by silica anchored Schiff base decorated polyamidoamine dendrimers: Behavior and mechanism

A class of silica anchored Schiff base decorated polyamidoamine(PAMAM) dendrimers were synthesized for removing aqueous Cu(Ⅱ) and Ag(Ⅰ). The adsorption performance was investigated synthetically and the adsorption mechanism was revealed. Results indicate the adsorption capacity depends on dendrimer generation, solution p H, contact time, temperature and initial metal ion concentration.The optimum adsorption pH is 6 for both metal ion. Adsorption kinetic suggests the adsorption can achieve equilibrium at 180 and 150 min for Cu(Ⅱ) and Ag(Ⅰ). The kinetic process is found to be in good agreement with pseudo-second-order model and film diffusion is the rate-controlling step. The adsorption isotherm indicates the adsorption is proceeded by monolayer behavior with chemical mechanism. These adsorbents exhibit competitive adsorption capacity as compared with other reported adsorbents. Theoretical calculation demonstrates the participation of hydroxyl, carbonyl, and amide groups during the adsorption of Cu(Ⅱ), while hydroxyl and amide groups are mainly responsible for capturing Ag(Ⅰ).

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.