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Abstract: Hyperbranched poly(amido amine)s containing vinyl and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with equal molar ratio in feed. 1H, 13C and HSQC NMR techniques were used to clarify the structure of hyperbranched polymers and polymerization mechanism. The Michael addition reaction of hyperbranched poly(1TT-1APD)s with primary amine-terminated poly(ε-benzyloxycarbonyl-l-lysine)s [PLys(Z)] yielded a star-like hyperbranched polymers with poly(1TT-1APD) core and Plys(Z) shell. The Z groups in PLys(Z) were removed under acidolysis, and thus star-like hyperbranched polymers with hydroxyl groups inside and primary amine groups outside were obtained successfully. [Copyright &y& Elsevier]

Abstract: This paper reports on the design, synthesis and spectral characteristics of a novel PAMAM dendron (7), core and peripherally functionalized with 1,8-naphthalimide fluorophores. The novel compound 7 was configured as light harvesting antenna where the system surface is functionalized with “donor” dyes (blue emitting 1,8-naphthalimides) that are capable of absorbing light and efficiently transferring the energy to a single “acceptor” dye (yellow-green emitting 1,8-naphthalimide) in the focal point of the dendron. The overlap between the emission of the donor and the absorbance of the acceptor was more than 95%. As a result of the energy transfer, the blue emission intensity of the periphery in the donor–acceptor system was decreased with 93%, while the yellow-green core fluorescence enhancement (λ ex =360nm) of the system was more than 26 times with respect to the fluorescence intensity of the comparative yellow-green emitting 1,8-naphthalimide. This indicates efficient energy transfer between the donor and acceptor dye fragments and that the novel compound 7 would be able to act as a highly efficient light harvesting antenna. [Copyright &y& Elsevier]

PAMAM dendrimers can permeate across intestinal epithelial barriers suggesting their potential as oral drug carriers. In the present study, we have developed a drug–PAMAM complex for oral administration. The loading of a model drug, doxorubicin into PAMAM, the cellular uptake and Pharmacokinetics of the doxorubicin–PAMAM complex were studied. As the results, the cellular uptake of doxorubicin in Caco-2 cells treated with the doxorubicin–PAMAM complex was increased significantly with an increase in concentration and time, as compared to that treated with free doxorubicin. And the transport efficiency of the doxorubicin–PAMAM complex from the mucosal side to the serosal side was 4–7 times higher than that of free doxorubicin in different segments of small intestines of rat. The doxorubicin–PAMAM complex led to the bioavailability that was more than 200-fold higher than that of free doxorubicin after oral administration. These results indicate that PAMAM dendrimer is a promising novel carrier to enhance the oral bioavailability of drug, especially for the P-glycoprotein (P-gp) substrates. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2208–2216, 2008 [ABSTRACT FROM AUTHOR]

Abstract: 1′-(Diphenylphosphino)-1-(N-butylcarbamoyl)ferrocene (P1) and the analogous higher amides P2–4 related to the first-generation PAMAM dendrimers bearing up to four 1′-(diphenylphosphino)ferrocen-1-yl terminal groups were synthesized by amidation of the respective (poly)amines with 1′-(diphenylphosphino)ferrocenecarboxylic acid (Hdpf). Testing of amides P1–4 as ligands for palladium-catalyzed Suzuki and Heck coupling reactions has shown that these amidophosphines preserve the activity of the single phosphinoferrocenyl unit, giving rise to active catalysts in both C–C forming reactions. Even for such relatively small systems, a positive influence of the dendritic assembly was notable as the compounds bearing a higher number of the phosphinoferrocenyl termini afforded faster reacting catalytic systems at the same palladium loading and P-to-Pd ratio. [Copyright &y& Elsevier]

Abstract: Electrodeposition of silver nanostructures on a polyamidoamine (PAMAM) dendrimers-modified surface has been reported. The assembled PAMAM monolayer film was used as a substrate for electrodeposition. We found that the PAMAM dendrimers obviously affected nucleation growth and silver nanostructures (spherical, dendritic and “fish bone” shapes) were obtained, which were different from those deposited on unmodified surfaces. It was attributed to the unique structures and properties of PAMAM dendrimers compared with linear polymers. Field-emitted scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy were used to characterize the deposited nanostructures. The effects of electrodeposition potential and time, Ag+ concentration, and the electrolyte were carefully investigated and studied. These results showed that PAMAM dendrimers could be used as “controllers” for modulation of deposited silver nanostructures. [Copyright &y& Elsevier]

A simple, accurate and rapid colorimetric method using ninhydrin reagent was developed for the determination of polyamidoamine (PAMAM) dendrimers (G4, G5, and G6) and their derivates in aqueous medium. This method was based on the interaction of the primary amino group of PAMAM dendrimers with ninhydrin reagent to form a blue-colored product with λmax at 570 nm. Beer's law was obeyed in the concentration range of 25-200 µg/ml of all the three investigated PAMAM dendrimers. The effects of experimental parameters such as reagent concentration and reaction time were studied to optimize the colorimetric method. Accuracy and precision of the colorimetric method were assessed by statistical analysis. Acetylated G5 PAMAM dendrimers with various acetylated rates were simultaneously measured by the described ninhydrin assay and NMR studies and the data obtained by the two methods approximately accorded with each other. Results showed that the suggested procedures were suitable for the determination of PAMAM dendrimers and their derivates in aqueous solutions with satisfactory accuracy and precision. [ABSTRACT FROM AUTHOR]

Abstract: Electrodeposition of novel Au/Pd bimetallic nanostructures with dendrimer films as matrices has been reported. The dendrimers exhibited highly open structures arising from protonation of amines and this made them have good penetrability for solvent molecules. The unique properties of dendrimers obviously affected the morphologies and compositions of deposited bimetallic nanostructures compared with those from unmodified surfaces. Field-emitted scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and UV–vis spectroscopy were used to characterize these nanostructures. The results showed that these bimetallic nanostructures were consisted of many small nanoparticles. Effects of ratios of KAuCl4 and K2PdCl6, electrodeposition time and layer number of assembled dendrimers were thoroughly investigated. At last, electrochemical properties of the bimetallic nanostructures were also studied. [Copyright &y& Elsevier]

Dendrimers have successfully proved themselves as useful additives in different routes of drug administration because they can render drugs greater water-solubility, bioavailability, and biocompatibility. This review demonstrated the potential of dendrimers to be applied in these detailed routes with particular reference to intravenous, oral, transdermal, and ocular delivery systems. As a necessary introduction, the structures, synthesis, and properties of dendrimers were presented. Furthermore, the interaction mechanisms between dendrimers and drug molecules, including simple encapsulation, electrostatic interaction, and covalent conjugation, were elaborated. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:123–143, 2008 [ABSTRACT FROM AUTHOR]

Abstract: Cd1−x Zn x S solid solution was prepared by coprecipitation method with PAMAM as a template, calcined at 573K under N2 atmosphere and characterized by BET, XRD, UV–vis, HRTEM and XRF. The size of Cd1−x Zn x S solid solution particles was about 5nm and the bandgap was estimated to be 2.09–3.12eV. The photocatalytic activities of Cd1−x Zn x S solid solutions on degradation of rhodamine B were evaluated under visible-light irradiation. The results indicated that Cd0.59Zn0.22S solid solution exhibited the highest photocatalytic activity among all the as-prepared samples. The mechanism of photocatalysis under visible-light irradiation was also discussed. [Copyright &y& Elsevier]

Abstract: A new 4-bromo-1,8-naphthalimide-labelled polyamidoamine (PAMAM) dendrimer from zero generation has been synthesised and characterised. Its functional characteristics, determined in acetonitrile solvent are discussed. The ability of the dendrimer to detect metal cations has been evaluated in acetonitrile by monitoring the quenching of the fluorescence intensity. Different metal cations have been tested Co2+, Ni2+, Cu2+ and Fe3+ for the purpose. The results have shown clearly that only Fe3+ could be efficiently detected using the dendrimer. [Copyright &y& Elsevier]

The protonation mechanisms of the poly(amidoamine) (PAMAM) andpoly(propyleneimine) (PPI) dendrimers are clarified and related to their molecular structure. The overall proton binding isotherms can be interpreted in terms of a site binding model, which involves a limited number of parameters, and can be used to gain detailed insight in both macroscopic and microscopic protonation mechanisms. The protonation of the PAMAM dendrimers is dominated by the chemical environment of the amine sites, and the sites protonate almost independently leading to protonation mechanism with a characteristic intermediate core-shell structure. In the case of PPI, the protonation is dominated by the electrostatic nearest-neighbor repulsions between the protonated sites, and leads to an intermediate »onion-like« structure where all the odd shells are protonated. [ABSTRACT FROM AUTHOR]

Dendrimers are three dimensional nanosized synthetic molecules that have internal cavities and numerous surface groups. In recent times they have received increased attention in sensing applications. For dendrimers to be used as sensors, they most commonly require functionalization at their surface. This is because the surface is generally the first point of contact between the dendrimer and the outside world, hence surface functionalization serves to selectively home in on the target analyte. Further, sensor signals may be transmitted through surface functionalities e.g. fluorochromic molecules. It is therefore important to document surface functionalization approaches. Dendrimers with amine surface groups have the advantage of being able to be conjugated to other molecules via an amide linkage, which is one of the most fundamental and widespread chemical bonds in nature. In this paper we demonstrate the properties of dendrimers that make them so applicable to sensing. We review several methods for functionalizing dendrimers via an amide linkage, as well as present a review of surface functionalized polyamidoamine, polyamine, and polypeptide dendrimers that have been employed for biological, chemical and molecular sensing. [ABSTRACT FROM AUTHOR]

Abstract: A nanofiltration method has been developed in a microfluidic format for the continuous-flow pressure-driven purification of half-generation poly(amidoamine) (PAMAM) dendrimers, a family of macromolecules characterized by highly branching structures radiating from a central core, without additional solvents or buffers. An organic solvent resistant nanofiltration membrane, STARMEM 122, has been fully integrated into a hard polymer microfluidic module by transmission laser welding. The membrane was initially characterized in a bench-top test fixture to determine the solvent permeance and percent rejection of a surrogate molecule, Rhodamine B, at lower than typical operating pressures (P <7bar). The microfluidic module then underwent similar testing at 1.4bar with the surrogate and with the generation-0.5 PAMAM dendrimer. This approach to nanofiltration will readily interface to upstream microreactors. [Copyright &y& Elsevier]

Abstract: Quinolones, an expanding class of clinically established potent antibiotics, is not freely soluble in water which prevents the design of liquid dosage forms and restricts their use in topical applications. In the present study we investigated the potential of polyamidoamine (PAMAM) dendrimers as drug carriers of quinolones (nadifloxacin and prulifloxacin) by aqueous solubility and antibacterial activity studies. Results showed that the aqueous solubility of nadifloxacin and prulifloxacin was significantly increased by PAMAM dendrimers. Microbiology studies showed that nadifloxacin and prulifloxacin still exhibit their strong antimicrobial activities in the presence of dendrimers. These studies indicated that PAMAM dendrimers might be considered as biocompatible carriers of quinolones under suitable conditions. [Copyright &y& Elsevier]

Abstract: Patterning of silicon substrates with poly(amidoamine) generation 5 (PAMAM-G5) dendrimers using soft lithographic microcontact printing (μCP) is presented. μCP is shown to yield monolayers of dendrimers patterned with high level of definition over μm2 to mm2 areas. The patterns are stable over a period of weeks, which is attributed to the suppressed diffusion of partially charged G5 PAMAM on oxidized silicon. However, the dendrimers studied were shown to be relatively weakly bound to the substrate when subjected to lateral stresses. In aqueous conditions most of the dendrimers desorbed from the substrate. [Copyright &y& Elsevier]

The blood-brain barrier (BBB) poses great difficulties for gene delivery to the brain. To circumvent the BBB, we investigated a novel brain-targeting gene vector based on the nanoscopic high-branching dendrimer, polyamidoamine (PAMAM), in vitro and in vivo. Transferrin (Tf) was selected as a brain-targeting ligand conjugated to PAMAM via bifunctional polyethyleneglycol (PEG), yielding PAMAM-PEG-Tf. UV and nuclear magnetic resonance (NMR) spectroscopy were used to evaluate the synthesis of vectors. The characteristics and biodistribution of gene vectors were evaluated by fluorescent microscopy, flow cytometry, and a radiolabeling method. The transfection efficiency of vector/DNA complexes in brain capillary endothelial cells (BCECs) was evaluated by fluorescent microscopy and determination of luciferase activity. The potency of vector/DNA complexes was evaluated by using frozen sections and measuring tissue luciferase activity in Balb/c mice after i.v. administration. UV and NMR results demonstrated the successful synthesis of PAMAM-PEG-Tf. This vector showed a concentration-dependent manner in cellular uptake study and a 2.25-fold brain uptake compared with PAMAM and PAMAM-PEG in vivo. Transfection efficiency of PAMAM-PEG-Tf/DNA complex was much higher than PAMAM/DNA and PAMAM-PEG/DNA complexes in BCECs. Results of tissue expression experiments indicated the widespread expression of an exogenous gene in mouse brain after i.v. administration. With a PAMAM/DNA weight ratio of 10:1, the brain gene expression of the PAMAM-PEG-Tf/DNA complex was ∼2-fold higher than that of the PAMAM/DNA and PAMAM-PEG/ DNA complexes. These results suggested that PAMAM-PEG-Tf can be exploited as a potential nonviral gene vector targeting to brain via noninvasive administration. [ABSTRACT FROM AUTHOR]

Hyperbranched poly(amido amine) (h-PAMAM) was synthesized from different feed ratios of diethylene triamine and methyl acrylate by the simple one-pot and commercial synthesis method. Reaction procedures and products were intensively studied by FTIR, inherent viscosity and fluorescence techniques. The ill-structured h-PAMAM shared similar chemical and physical properties with well defined poly(amido amine) (PAMAM) dendrimers in generation 2 or 3. Its strong fluorescence properties were influenced by pH values, solvents, concentrations, terminal groups and other factors. [ABSTRACT FROM AUTHOR]

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most frequently used drugs in the world, primarily for symptoms associated with osteoarthritis and other chronic musculoskeletal conditions. However, adverse effects caused by oral administration, such as local or systemic disturbance in the gastrointestinal tract, have limited the clinical applications of these drugs. In the present study we have assessed the ability of polyamidoamine (PAMAM) dendrimers to facilitate transdermal delivery of NSAIDs, using Ketoprofen and Diflunisal as model drugs. In vitro permeation studies with excised rat skins indicated that PAMAM dendrimers significantly enhanced the accumulative permeated amount of both drugs after 24 h, as compared to drug suspensions without PAMAM dendrimers. Similarly, anti-nociceptive studies using the acetic acid-induced writhing model in mice showed a prolonged pharmacodynamic profile for the NSAIDs–PAMAM dendrimer complex after transdermal administration. In addition, blood drug level studies revealed that the bioavailability was 2.73 times higher for the Ketoprofen–PAMAM dendrimer complex and 2.48 times higher for the Diflunisal–PAMAM dendrimer complex, respectively, than the pure drug suspensions. These results demonstrated that PAMAM dendrimers can effectively facilitate skin penetration of NSAIDs and may have the potential applications for the development of new transdermal formulations. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci [ABSTRACT FROM AUTHOR]

Abstract: Sulfamethoxazole (SMZ), a sulfonamide with well-known anti-bacterial properties, is not freely soluble in water and causes problems in its clinical applications. In the present study we investigated the potential of ethylenediamine (EDA) core polyamidoamine (PAMAM) dendrimers as drug carriers of SMZ by aqueous solubility, in vitro release as well as anti-bacterial activity studies. Results showed that the aqueous solubility of SMZ was approximately proportional to dendrimer concentration (a 40-fold increase in solubility in 10mg/ml G3 PAMAM dendrimer solutions compared with that in double-distilled water at 37°C). The in vitro release of SMZ in the presence of PAMAM dendrimers was significantly slower compared to pure SMZ dissolved in ethanol. Microbiology studies showed that PAMAM dendrimers could increase the anti-bacterial activity of SMZ (a 4- or 8-fold increase in the anti-bacterial activity of SMZ in dendrimer solution compared to pure SMZ dissolved in dimethylsulfoxide (DMSO) or 0.01M NaOH solution). The in vitro release behavior and anti-bacterial activity studies indicated that PAMAM dendrimers might be considered as potential drug carriers of sulfonamides with a sustained release behavior under suitable conditions. [Copyright &y& Elsevier]

In this study, the distribution of labeled dendrimers in native and aneurysmal rat aortic tissue was examined. Adult male rats underwent infrarenal aorta perfusion with generation 5 (G5) acetylated Alexa Fluor 488-conjugated dendrimers for varying lengths of time. In a second set of experiments, rats underwent aortic elastase perfusion followed by aortic dendrimer perfusion 7 days later. Aortic diameters were measured prior to and postelastase perfusion, and again on the day of harvest. Aortas were harvested 0, 12, or 24 h postperfusion, fixed, and mounted. Native aortas were harvested and viewed as negative controls. Aortic cross-sections were viewed and imaged using confocal microscopy. Dendrimers were quantified (counts/high-powered field). Results were evaluated by repeated measures ANOVA and Student's t-test. We found that in native aortas, dendrimers penetrated the aortic wall in all groups. For all perfusion times, fewer dendrimers were present as time between dendrimer perfusion and aortic harvest increased. Longer perfusion times resulted in increased diffusion of dendrimers throughout the aortic wall. By 24 h, the majority of the dendrimers were through the wall. Dendrimers in aneurysmal aortas, on day 0 postdendrimer perfusion, diffused farther into the aortic wall than controls. In conclusion, this study documents labeled dendrimers delivered intra-arterially to native rat aortas in vivo, and the temporal diffusion of these molecules within the aortic wall. Increasing perfusion time and length of time prior to harvest resulted in continued dendrimer diffusion into the aortic wall. These preliminary data provide a novel mechanism whereby local inhibitory therapy may be delivered locally to aortic tissue. [ABSTRACT FROM AUTHOR]

Abstract: The narrow-dispersed dendrimer-encapsulated gold nanoparticles without agglomeration were prepared from the grafted-dendrimers on the surface of the silica microspheres, successively by complexation of the gold chloride anion with the nitrogen atom of the dendrimer and the reduction with sodium borohydride as reductant. The hollow capsule-stabilized gold nanoparticles were prepared through the encapsulation of dendrimer successively by LBL self-assembly process of polyelectrolytes with modified-silica as template and removal of the silica core by hydrofluoric acid. The size of gold nanoparticles was . The catalytic activity of the capsule-stabilized gold nanoparticles was investigated in the reduction reaction of 4-nitrophenol to 4-aminophenol with sodium borohydride as reductant. [Copyright &y& Elsevier]

Abstract: Synthesis of hydroxyapatite (HAP; Ca10(PO4)6(OH)2) nanoparticles with ellipsoid-like morphology and different size was achieved by hydrothermal crystallization at 150°C and pH 9 through a mixture solution of Ca(NO3)2 and (NH4)2HPO4 in the presence of the PAMAM with amido groups at the external surface. As the generation number of the PAMAM dendrimer with amido groups at the external surface increased from G1.0 to G4.0, the particle sizes of hydroxyapatite were decreased from 82, 77, 48 to 38nm, respectively, and while the shape of hydroxyapatite also were changed from rod- to ellipsoid-like. With further increase in the generation number to G5.0, the particle size was not changed. The relationship between concentration of the dendrimer and the particle size in G4.0 of the PAMAM dendrimer with amido groups was also studied under the same condition. As concentration increased from 5.0 to 40gl−1, the particle sizes of ellipsoid-like were reduced from 55 to 25nm. [Copyright &y& Elsevier]

Abstract: The interaction between PAMAM (polyamidoamine) dendrimer generation 4 (G4) and 3,5 (G3,5) with model lipid membranes composed of dipalmytoylphosphatidylcholine (DPPC) has been investigated. Differential scanning calorimetry (DSC) and Raman spectroscopy were applied to assess the thermodynamic changes caused by PAMAM G4 and G3,5 and to specify the exact location of these dendrimers into the DPPC lipid bilayer. DSC thermograms indicated that the maximum percentages of PAMAM G4 and of G3,5 that can be incorporated in the DPPC membrane without deranging its integrity were 5% and 3%, respectively. The Raman intensity ratios I 2935/2880, I 2844/2880 and I 1090/1130 cm−1 showed the degree of the fluidity of the lipid bilayer, while the absorption at 715cm−1 showed a strong interaction of PAMAM G4 and G3,5 with the polar head group of phospholipid. The results showed that the incorporation of the PAMAM G4 and G3,5 dendrimers in DPPC bilayers causes a concentration dependent increase of the membrane fluidity and that the bilayers interact strongly with both the lipophilic part and the polar head group of the phospholipids. Due to the current weak knowledge relating to the mechanism(s) under which dendrimers interact with lipidic membranes and transport through cells, these results may justify the tendency of dendrimers to disrupt biological membranes. The findings from this study could also prove helpful to rationally design new liposomal drug carriers for bioactive molecules by combining dendrimeric and liposomal technologies. [Copyright &y& Elsevier]

Abstract: Ketoprofen, a non-steroidal anti-inflammatory drug with well-known anti-inflammatory, antipyretic and analgesic properties, has low solubility in water and causes local or systemic disturbance in the gastrointestinal tract. In the present study we investigated the potential of polyamidoamine (PAMAM) dendrimers as drug carriers of ketoprofen by in vitro and in vivo studies. The in vitro release of ketoprofen from the drug–dendrimer complex is significantly slower compared to pure ketoprofen. Anti-nociceptive studies using the acetic acid-induced writhing model in mice showed a prolonged pharmacodynamic behavior for the ketoprofen–PAMAM dendrimer complex. Also, the blood level studies were investigated. We concluded that PAMAM dendrimers might be considered as a potential drug carrier of ketoprofen with a sustained release behavior under suitable conditions. [Copyright &y& Elsevier]

Abstract: Two recently synthesized poly(amidoamine) dendrimers from zero and second generation whose periphery comprises fluorescent 4-piperidino-1,8-naphthalimide units have been investigated as potential sensors of metal cations and protons. The photophysical characteristics of the dendrimers have been determined by fluorescence and absorption spectroscopy. Experiments have been performed in the presence of Zn2+, Ni2+, Ce3+, Cu2+, Co2+ and Ag+ cations. The increase in the fluorescence intensity of the dendrimers in the presence of protons indicates their sensitivity to the protons. The response of the dendrimers ligands depends on the nature of the added metal cations. The best performance is accomplished for detecting Cu2+ and Co2+ cations. The results obtained reveal the capacities of these systems to act as reliable detectors of environment pollution by metal cations and protons. [Copyright &y& Elsevier]

Abstract: The design, synthesis and characterization of a series of zero generation (G0) PAMAM dendrimer-based prodrugs for the potential enhancement of drug solubility and bioavailability are described. Naproxen, a poorly water-soluble drug, was conjugated to dendrimers either directly by an amide bond or by ester bonds using either l-lactic acid or diethylene glycol as a linker. All of the prodrugs were more hydrophilic than the parent drug, as evaluated by drug partitioning between 1-octanol and phosphate buffer (pH 7.4). Hydrolysis of the conjugates was measured at 37°C in hydrochloric acid buffer (pH 1.2), phosphate buffer (pH 7.4), borate buffer (pH 8.5) and in 80% human plasma. The amide conjugate and both ester conjugates were chemically stable at all pHs over 48h of incubation. Naproxen was enzymatically released from both ester conjugates in plasma; the lactic ester conjugate hydrolyzed slowly with only 25% of naproxen released after 24h, the diethylene glycol ester conjugate cleaved rapidly following pseudo first order kinetics (t 1/2 =51min). G0 PAMAM dendrimer prodrugs with an appropriate linker (diethylene glycol) show good potential as carriers for oral delivery. [Copyright &y& Elsevier]

Abstract: Interaction between cationic gold nanoparticles ligated with 3-mercaptopropyltrimethylammonium chloride (MPTAC) and anionic poly(amidoamine) (PAMAM) dendrimers with carboxylate terminals (Generation 3.5 and 5.5-COONa) has been investigated in aqueous solution and on carbon film by UV–vis, TEM, DLS and zeta potential measurements. In the absence of PAMAM dendrimers, the MPTAC–Au nanoparticles in water exhibited a surface plasmon resonance (SPR) band at 520nm. The gold particles of 4.2nm in mean diameter were homogeneously dispersed on the carbon grids. Addition of PAMAM brought about an increase in the absorbance and redshift of the SPR band, which was attributed to aggregation of the gold nanoparticles by adsorption of the dendrimer to the MPTAC ligand layers owing to electrostatic attraction. In particular, chainlike aggregates were formed at low concentrations of the dendrimer (r =[PAMAM]/[MPTAC]≤1). While a further increase in the dendrimer concentration (r =2) led to a remarkable decrease in the size of aggregates, and λ max of the SPR band returned to approximately the same wavelength as that for r =0.5. [Copyright &y& Elsevier]

Abstract: A novel nanofiltration membrane (PEK-C NF membrane) prepared with poly(amidoamine) (PAMAM) dendrimer and trimesoyl chloride (TMC) by in situ interfacial polymerization on phenolphthalein poly(ether ether ketone) (PEK-C) ultrafiltration membrane was investigated. FTIR–ATR, XPS, SEM and contact angle of the water were employed to characterize the chemical and physical changes of resulting membranes. The flux and rejection of resulting membranes increased with increasing concentrations of PAMAM and/or generation numbers of PAMAM for NaCl concentration. Both rejection and flux decrease with an increase of MgSO4 concentration. The salts rejections order of resulting membrane is MgCl2 >MgSO4 >NaCl>Na2SO4, which shows that resulting membranes were all positively charged NF membrane. Influences of operating temperature on flux and rejection of different solutes show that resulting membrane is thermostable at higher temperature (e.g. 80°C). The PEK-C NF membrane is especially suitable for separating cationic solutes from others by increasing operating temperature. The pH in the feed increase from 2 to 9 resulted in over two-fold increase in the flux for NaCl solution. Therefore the PEK-C NF membrane is also particularly suitable for treating acidic feed. The studied membrane possesses maximum operating pressure lower than 2.0MPa and excellent stability during 1080h (1.5 months) of continuous filtration at 30°C. [Copyright &y& Elsevier]

Abstract: This article summarizes our efforts to evaluate the potential of poly (amidoamine) (PAMAM) dendrimers as carriers for oral drug delivery. Specifically, the permeability of a series of cationic PAMAM–NH2 (G0–G4) dendrimers across Caco-2 cell monolayers was evaluated as a function of dendrimer generation, concentration, and incubation time. The influence of dendrimer surface charge on the integrity, paracellular permeability, and viability of Caco-2 cell monolayers was monitored by measuring the transepithelial electrical resistance (TEER), 14C-mannitol permeability, and leakage of lactate dehydrogenase (LDH) enzyme, respectively. Microvascular extravasation of PAMAM–NH2 dendrimers in relation to their size, molecular weight, and molecular geometry is also discussed. Results of these studies show that transepithelial transport and microvascular extravasation of PAMAM dendrimers are dependent on their structural features including molecular size, molecular geometry, and surface chemistry. These results suggest that by optimizing the size and surface charge of PAMAM dendrimers, it is possible to develop oral delivery systems based on these carriers for targeted drug delivery. [Copyright &y& Elsevier]

Abstract: The formation of particulate systems with well-defined sizes and shapes is of eminent interest in certain medical applications such as drug delivery, gene transfection, and imaging. The high level of control possible over the architectural design of dendrimers; their size, shape, branching length/density, and their surface functionality, clearly distinguishes these structures as unique and optimum carriers in those applications. The bioactive agents may be encapsulated into the interior of the dendrimers or chemically attached/physically adsorbed onto the dendrimer surface, with the option of tailoring the carrier to the specific needs of the active material and its therapeutic applications. In this regard, the high density of exo-presented surface groups allows attachment of targeting groups or functionality that may modify the solution behavior or toxicity of dendrimers. Quite remarkably, modified dendrimers have been shown to act as nano-drugs against tumors, bacteria, and viruses. Recent successes in simplifying and optimizing the synthesis of dendrimers such as the ‘lego’ and ‘click’ approaches, provide a large variety of structures while at the same time reducing the cost of their production. The reflections on biomedical applications of dendrimers given in this review clearly demonstrate the potential of this new fourth major class of polymer architecture and indeed substantiate the high hopes for the future of dendrimers. [Copyright &y& Elsevier]

The article focuses on the findings of a study that used an LKB-2277 Bioactivity Monitor to determine the effect of Poly (amido amine) (PAMAM) dendrimers on the thermogenic curves of the growth metabolism of Escherichia coli. It explores the stimulatory effect of PAMAM G4 dendrimer. It concludes that small changes in same macromolecules could produce significant different effects on microbial growth.

Abstract: Preparation of Pt nanoclusters on the poly(amidoamine) (PAMAM) modified surface by electrodeposition was firstly reported. The presence of PAMAM could affect the growth of Pt nanostructures. Field-emitted scanning microscopy images showed that these nanoclusters were not common nanoparticles but were consisted of many small nanoparticles. The size of them could be controlled and the deposition mechanism was also discussed. This method would give a route of preparing novel nanostructures by electrodeposition. [Copyright &y& Elsevier]

Abstract: Ketoprofen is a non-steroidal anti-inflammatory drug which is not freely soluble in water and creates gastrointestinal problems. In the present study we investigated the potential of polyamidoamine (PAMAM) dendrimers to increase the solubility of ketoprofen. The effect of variables, such as pH condition, concentration and generation of dendrimer, has been investigated. The experimental results showed that the solubility of ketoprofen in the dendrimer solutions was proportional to dendrimer concentration. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of ketoprofen. [Copyright &y& Elsevier]

Abstract: In the present study we investigated the effect of ethylenediamine (EDA) core polyamidoamine (PAMAM) dendrimers on the aqueous solubility of nicotinic acid. The aqueous solubility of nicotinic acid was measured in the presence of dendrimers at room temperature in distilled water. The effect of variables, such as pH condition, concentration, surface functional group and generation (molecule size) of dendrimer, has been investigated. Results showed that the solubility of nicotinic acid in the dendrimer solutions was proportional to dendrimer concentration, both amine and ester-terminated dendrimers caused the higher increase in nicotinic acid solubility at higher pH conditions. The order in which the dendrimers increased the solubility at a constant pH condition was G4>G3>G2>G1. In addition, at each pH, the solubility of nicotinic acid was greater in the presence of amine-terminated dendrimers compared to the amine ester-terminated dendrimers possessing the same number of surface functional groups. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of nicotinic acid. [Copyright &y& Elsevier]

Abstract: Dendrimers attract much attention as potential drug and gene carriers for intracellular delivery. From this point of view, it is crucial to extend our knowledge about their interactions with membranes. The influence of polyamidoamine (PAMAM) dendrimers on the thermotropic behavior of DPPC multilamellar vesicles and DMPC small unilamellar vesicles was examined by differential scanning calorimetry. We used three types of PAMAM dendrimers to determine how a dendrimer structure determines interactions with liposomes. We show that the strength of interactions depends on both the dendrimers’ structure and degree of hydrophobicity. A model for the interaction of each type of dendrimer with liposomes was proposed. [Copyright &y& Elsevier]

Polyamidoamine (PAMAM) is a type of macromolecule having a definite chemical structure and a large number of terminal functional groups. The synthetic approach of the adsorbent with high adsorption capacity involved arching of PAMAM onto cellulose beads by reaction with epichlorohydrin. The product thus prepared had a large number of amino groups of 2.94 mmol/g derived from 0.23 mmol/g epoxy groups on cellulose heads. This method presents an effective method for the preparation of high-loading adsorbents. [ABSTRACT FROM AUTHOR]

Abstract: Liposomes composed of HePC:EPC:SA 10:10:0.1 (molar ratio) (1) and EPC:SA 10:0.1 (molar ratio) (2) were prepared and were used for incorporating the doxorubicin–PAMAM complex (3:1 molar ratio) (3). The doxorubicin–PAMAM complex was attached to liposomes and the incorporation efficiency was 91 and 95% for 1 and 2, respectively. The incorporation efficiency for doxorubicin into PAMAM was almost 97% while doxorubicin to PAMAM molar ratio was 3.56±0.04. The release rate of doxorubicin as doxorubicin–PAMAM complex from liposomes 1 and 2 and from the complex 3, was studied using buffers and 50% RPMI cell culture medium at 37 and 25°C. The low release rate of doxorubicin as well as the high incorporation efficiency of doxorubicin–PAMAM complex into liposomes are considered as beneficial factors concerning the activity of doxorubicin. The cytotoxic activity of the liposomal formulation 1 incorporating doxorubicin–PAMAM complex, based on doxorubicin activity, was compared to that of 2 incorporating doxorubicin–PAMAM complex and to that of 3. The results showed that complex 1 was the most active formulation against all cancer cell lines compared to that of 2 and 3. Liposomal formulations composed of lipids and of a drug–dendrimer complex could be characterized as modulatory liposomal controlled release system (MLCRS), and could provide benefits to the delivery of drugs and modulate their release. [Copyright &y& Elsevier]

Abstract: Synthetic glycoconjugated dendrimers have emerged as important functional glycomimetics for studying multivalency effects in the cell–cell communications. We report herein, a synthetic route to functionalized glycodendrimers with scyllo-inositol as the scaffold, which have a directed geometry; one side of the dendrimers is designed for ready attachment to the AFM probe/solid matrix, and the other to have a varying number of a sugar. [Copyright &y& Elsevier]

Abstract: Silver nanocomposite multilayer films were prepared through the in situ method. Multilayer thin films, prepared through the sequential electrostatic deposition of a positively charged third-generation poly(amidoamine) dendrimer (PAMAM) and negatively charged poly(styrenesulfonate) (PSS) and poly(acrylic acid) (PAA), were utilized as nanoreactors for the formation of silver nanoparticles. The silver ions were preorganized in layer-by-layer (LBL) films composed of PAMAM dendrimers and subsequently reduced with hydrogen to prepare the silver nanoparticles. The UV–vis spectrum and profilometer were used to characterize the regular growth of bilayers. UV–vis absorption from plasmon resonance at 435 nm and TEM images indicated the formation of the silver nanoparticles in the multilayer films. The silver nanocomposite LBL films were also constructed on the indium tin oxide-glass and investigated using cyclic voltammetry. The silver nanoparticles in the multilayer films have a stronger negative redox potential. The silver nanocomposite LBL films may have a potential application in the catalysis of reduction of 4-nitrophenol with sodium borohydride. [Copyright &y& Elsevier]

Abstract: We investigated the interactions between dendrimer-coated magnetite nanoparticles (MNPs) and the protein serum albumin. The investigation was based on the fluorescence quenching of tryptophan residue of serum albumin after binding with the dendrimer-coated magnetite nanoparticles. The extent of the interactions between bovine serum albumin and dendrimer-coated MNPs strongly depends on their surface groups and pH value. [Copyright &y& Elsevier]

Abstract: Polyamidoamine dendrimer was synthesized on the surface of amino silane modified magnetite nanoparticles. After coating of streptavidin to these dendrimer-modified magnetite nanoparticles, an up to 3.4 times higher amount of streptavidin (SA) was measured compared to magnetite nanoparticles modified with only amino silane. The biotin-binding capacity of SA thus increased after dendrimer modification. [Copyright &y& Elsevier]

Abstract: This review is introduced by an examination of the historical roles that quantized building blocks, such as atoms and monomers have played in the development of small molecule and traditional polymer synthesis, respectively. The unique features of traditional macromolecular architectures (i.e. linear, crosslinked, branched), as well as controlled nanostructures in biology were used as frames of reference to anticipate potential new properties, phenomena and synthetic constructs that should be expected to emerge at the interface of the ‘dendritic architectural state’ with the nanotechnology revolution. Intrinsic new properties associated with the ‘dendritic architectural state’, such as the ability to control monodisperse nanoscale sizes, shapes and presentation of surface functionality are reviewed. Unique ‘dendritic effects’ related to de Gennes dense packing (i.e. unimolecular encapsulation, periodic nanocontainer properties), polyvalency (nanoscaffolding), as well as shape designing both within (i.e. cystamine core dendrimers) and beyond dendrimers (i.e. core–shell tecto(dendrimers)) to mimic biological proteins are described. The precise, quantized core–shell architectural properties and monomer shell filling features of dendrimers are compared to the electron shell filling patterns of elemental atoms by utilizing the Niels Bohr Periodic Table. This comparison has provided a rationale for explaining autoreactivity patterns observed at the sub-nanoscale (atoms), lower nanoscale (dendrimers) and higher nanoscale levels involving either unsaturated electron shells, monomer shells or dendrimer shells, respectively. Clearly, dendritic polymers, especially dendrons and dendrimers are expected to fulfill important roles as fundamental, reactive modules for nanoscale polymer syntheses. [Copyright &y& Elsevier]

Abstract: Poly(amidoamine) (PAMAM) dendrimers containing disulfide cores (i.e., cystamine) and possessing carboxylic acid or hydroxyl terminal groups were reduced with dithiothreitol (DTT) to yield single site, thiol core, functionalized PAMAM dendron reagents. These thiol functionalized dendron reagents were used to surface modify (dendronize) both gold nanoparticles, as well as CdSe/CdS (core–shell) quantum dots (QDs). Dendronization involved self-assembly of the focal point thiol functional dendrons at the metal interface of both gold and CdSe/CdS QDs by ligand exchange of protective surfactants used for their synthesis. The synthesis, characterization and preliminary luminescence studies of these new dendritic hybrids are reported. [Copyright &y& Elsevier]

Abstract: The fluorescence and aggregation behavior of poly(amidoamine) (PAMAM) dendrimers modified with phenyl groups at the periphery (PAMAM-P) were investigated. For comparison, the third generation (G3) PAMAM dendrimer with a shell of positive charge (PAMAM-PA) was also synthesized. PAMAM-P G3, G4 and G5 show dual fluorescence emission due to the fluorescence emission of phenyl ring and its excimer. By increasing the generation number from G2 to G4, the fluorescence intensity of phenyl ring decreases, and the fluorescence of phenyl excimer appears and becomes obvious. The three-dimensional geometry arrangement or dendrimer architecture was found to have a strong effect on their fluorescence behavior. This result is further supported by the solvent effect and model compound studies. The lower generations (PAMAM-P G0 to G3) were self-organized into spherical aggregates. However, no aggregation behavior was observed for the higher generations (>G3). The critical aggregation concentration (CAC) values measured by fluorescence spectroscopy were found to decrease gradually with increasing generation number from G0 to G3. [Copyright &y& Elsevier]

The conductivity, κ, and Krafft temperature, , of sodium dodecyl sulfate (SDS) with poly(amidoamine) dendrimers (PAMAM) of 0.0, 0.5, and 1.0 generations (G) have been determined at different surfactant as well as PAMAM concentrations. The critical micelle concentration of SDS increases with the increase in the amount of each generation and the additive effect of 0.5G is maximum. of SDS shows a systematic decrease with maximum reduction in the presence of 0.5G. Atomic force microscopy (AFM) captures a layered pattern of 1.0G in the form of nanorods and no AFM images are detected for 1.0G in the presence of SDS. All results demonstrate that SDS has favorable interactions with ester-terminated 0.5G PAMAM rather than amine-terminated 0.0G and 1.0G. [Copyright &y& Elsevier]

New fluorescent poly(amidoamine) (PAMAM) dendrimers, comprising 4-ethylamino-1,8-naphthalmide units on the periphery have been synthesized. Their photophysical properties in organic solvents of different polarity have been determined. The photodegradation of the dendrimers in organic solvents has been investigated. The effect of the coordination of the dendrimer with transition metal cations in N,N-dimethylformamide solution has been discussed. [Copyright &y& Elsevier]

The first surface vibrational sum frequency generation (SFG) spectroscopic studies of amine-terminated Starburst® PAMAM G0 and G1 and acylated PAMAM G0 dendrimers at the glass–, gold–, and air–dendrimer interface are presented. Amine-terminated PAMAM G0 and G1 dendrimers as compared to the acylated PAMAM G0 dendrimer reveal significantly different surface SFG spectroscopic signatures. Raman spectra from PAMAM G0 and G1 dendrimers are presented for comparison of the bulk vibrational spectra to that of the surface. The SFG data is suggestive of skewed methylene conformations in a distribution about the normal of the surface. [Copyright &y& Elsevier]

The study reports on the synthesis of four novel PAMAM dendrimers of generation 2, modified with 1,8-napthalimide. Their photophysical characteristics have been determined in organic solvents of different polarity (chloroform and N,N-dimethylformamide). The spectral assignments of the dendrimers are dependent on the nature of the substituent at C-4 position of the 1,8-naphthalimide structure. The low quantum yield of fluorescence of the novel materials reveals that a photo-induced electron transfer is proceeding from the core of the dendrimer molecule to the naphthalimide fluorophore located in its periphery. The PAMAM dendrimers thus modified exhibit good photo stability in N,N-dimethylformamide solution. [Copyright &y& Elsevier]

Highly branched, functionalized polymers have potential to act as efficient drug carrier systems. Dendrimers are ideal candidates among model hyperbranched polymers because of their well-defined structure and high density of functional groups. Using ibuprofen as a model drug, we studied the interaction between the drug and Polyamidoamine (PAMAM) dendrimers (generations 3 and 4 with &z.sbnd;NH2 functionality) and Perstrop Polyol (generation 5, hyperbranched polyester with &z.sbnd;OH functionality). FTIR and NMR studies suggest that ibuprofen predominantly forms a complex with PAMAM dendrimers because of the ionic interaction between the &z.sbnd;NH2 end groups and the carboxyl group of ibuprofen. On an average, up to 78 molecules of ibuprofen could be incorporated into one molecule of PAMAM-G4-NH2 with 64 end groups. This complex is stable in deionized water and methanol. The in vitro release of ibuprofen from drug–dendrimer complex is appreciably slower compared to pure ibuprofen. The complexed drug enters A549 cells much more rapidly than pure drug suggesting that dendrimers may be able to carry the complexed drug inside cells efficiently. Hyperbranched Polyol (with 128 &z.sbnd;OH end groups) appears to encapsulate approximately 24 drug molecules. Perhaps the lack of strong interactions between the &z.sbnd;OH end groups and the drugs prevents complex formation. [Copyright &y& Elsevier]