Interaction of cationic partial dendrimers with charged and neutral liposomes

Peptide Dendrimer-Based Antibacterial Agents: Synthesis and Applications

Pathogenic bacteria cause the deaths of millions of people every year. With the development of antibiotics, hundreds and thousands of people's lives have been saved. Nevertheless, bacteria can develop resistance to antibiotics, rendering them insensitive to antibiotics over time. Peptides containing specific amino acids can be used as antibacterial agents; however, they can be easily degraded by proteases in vivo. To address these issues, branched peptide dendrimers are now being considered as good antibacterial agents due to their high efficacy, resistance to protease degradation, and low cytotoxicity. The ease with which peptide dendrimers can be synthesized and modified makes them accessible for use in various biological and nonbiological fields. That is, peptide dendrimers hold a promising future as antibacterial agents with prolonged efficacy without bacterial resistance development. Their in vivo stability and multivalence allow them to effectively target multi-drug-resistant strains and prevent biofilm formation. Thus, it is interesting to have an overview of the development and applications of peptide dendrimers in antibacterial research, including the possibility of employing machine learning approaches for the design of AMPs and dendrimers. This review summarizes the synthesis and applications of peptide dendrimers as antibacterial agents. The challenges and perspectives of using peptide dendrimers as the antibacterial agents are also discussed.

Dendrimer-Mediated Delivery of Anticancer Drugs for Colon Cancer Treatment

The third most common cancer worldwide is colon cancer (CC). Every year, there more cases are reported, yet there are not enough effective treatments. This emphasizes the need for new drug delivery strategies to increase the success rate and reduce side effects. Recently, a lot of trials have been done for developing natural and synthetic medicines for CC, among which the nanoparticle-based approach is the most trending. Dendrimers are one of the most utilized nanomaterials that are accessible and offer several benefits in the chemotherapy-based treatment of CC by improving the stability, solubility, and bioavailability of drugs. They are highly branched polymers, making it simple to conjugate and encapsulate medicines. Dendrimers have nanoscale features that enable the differentiation of inherent metabolic disparities between cancer cells and healthy cells, enabling the passive targeting of CC. Moreover, dendrimer surfaces can be easily functionalized to improve the specificity and enable active targeting of colon cancer. Therefore, dendrimers can be explored as smart nanocarriers for CC chemotherapy.

Promising Nanomedicines of Shikonin for Cancer Therapy

Malignant tumor, the leading cause of death worldwide, poses a serious threat to human health. For decades, natural product has been proven to be an essential source for novel anticancer drug discovery. Shikonin (SHK), a natural molecule separated from the root of Lithospermum erythrorhizon, shows great potential in anticancer therapy. However, its further clinical application is significantly restricted by poor bioavailability, adverse effects, and non-selective toxicity. With the development of nanotechnology, nano drug delivery systems have emerged as promising strategies to improve bioavailability and enhance the therapeutic efficacy of drugs. To overcome the shortcoming of SHK, various nano drug delivery systems such as liposomes, polymeric micelles, nanoparticles, nanogels, and nanoemulsions, were developed to achieve efficient delivery for enhanced antitumor effects. Herein, this review summarizes the anticancer pharmacological activities and pharmacokinetics of SHK. Additionally, the latest progress of SHK nanomedicines in cancer therapy is outlined, focusing on long circulation, tumor targeting ability, tumor microenvironment responsive drug release, and nanosystem-mediated combination therapy. Finally, the challenges and prospects of SHK nanomedicines in the future clinical application are spotlighted.

Polyamidoamine Dendron-Bearing Lipids as Drug-Delivery Excipients

An amine-terminated polyamidoamine (PAMAM) dendron and two long alkyl groups were designed as a novel drug carrier that possesses an interior for the encapsulation of drugs and a biocompatible surface. We synthesized three dendron-bearing lipids, DL-G1, DL-G2, and DL-G3, which included first, second, and third generation polyamidoamine dendrons, respectively. The synthesized dendrimer encapsulating anticancer drug, 5-fluorouracil (5-FU), was prepared by extraction with chloroform from mixtures of the dendrimers and varying amounts of the drug. In vitro cytotoxicity of PAMAM conjugated di-n-dodecylamine micelles (G1, G2, G3) were analyzed on human gastric adenocarcinoma cells (AGS) by water-soluble tetrazolium-1 (WST-1) cell proliferation assay. Upon exposure to 5-FU loaded micelles, the viability of the cells decreased gradually in all generations. Cytotoxicity increased with increasing generation and reached its highest rate of 69.8 ± 3.2% upon 15 µM 5FU-loaded 25 µM PAMAM DL-3 micelle treatment. These results demonstrate that 5FU-loaded PAMAM conjugated di-n-dodecylamine treatment inhibits the proliferation of AGS cells in a generation-dependent manner.

Immobilization of Polyethyleneimine (PEI) on Flat Surfaces and Nanoparticles Affects Its Ability to Disrupt Bacterial Membranes

Interactions between a widely used polycationic polymer, polyethyleneimine (PEI), and a Gram-negative bacteria, E. coli, are investigated using atomic force microscopy (AFM) quantitative imaging. The effect of PEI, a known membrane permeabilizer, is characterized by probing both the structure and elasticity of the bacterial cell envelope. At low concentrations, PEI induced nanoscale membrane perturbations all over the bacterial surface. Despite these structural changes, no change in cellular mechanics (Young’s modulus) was detected and the growth of E. coli is barely affected. However, at high PEI concentrations, dramatic changes in both structure and cell mechanics are observed. When immobilized on a flat surface, the ability of PEI to alter the membrane structure and reduce bacterial elasticity is diminished. We further probe this immobilization-induced effect by covalently attaching the polymer to the surface of polydopamine nanoparticles (PDNP). The nanoparticle-immobilized PEI (PDNP-PEI), though not able to induce major structural changes on the outer membrane of E. coli (in contrast to the flat surface), was able to bind to and reduce the Young’s modulus of the bacteria. Taken together, our data demonstrate that the state of polycationic polymers, whether bound or free—which greatly dictates their overall configuration—plays a major role on how they interact with and disrupt bacterial membranes.

Designer Peptide and Protein Dendrimers: A Cross-Sectional Analysis

Dendrimers have attracted immense interest in science and technology due to their unique chemical structure that offers a myriad of opportunities for researchers. Dendritic design allows us to present peptides in a branched three-dimensional fashion that eventually leads to a globular shape, thus mimicking globular proteins. Peptide dendrimers, unlike other classes of dendrimers, have immense applications in biomedical research due to their biological origin. The diversity of potential building blocks and innumerable possibilities for design, along with the fact that the area is relatively underexplored, make peptide dendrimers sought-after candidates for various applications. This review summarizes the stepwise evolution of peptidic dendrimers along with their multifaceted applications in various fields. Further, the introduction of biomacromolecules such as proteins to a dendritic scaffold, resulting in complex macromolecules with discrete molecular weights, is an altogether new addition to the area of organic chemistry. The synthesis of highly complex and fully folded biomacromolecules on a dendritic scaffold requires expertise in synthetic organic chemistry and biology. Presently, there are only a handful of examples of protein dendrimers; we believe that these limited examples will fuel further research in this area.

Polyamidoamine (PAMAM) dendrimers as potential release modulators and oral bioavailability enhancers of vardenafil hydrochloride

Vardenafil hydrochloride (VAR) is an erectile dysfunction treating drug. VAR has a short elimination half-life (4-5 h) and suffers low oral bioavailability (15%). This work aimed to explore the dual potential of VAR-dendrimer complexes as drug release modulators and oral bioavailability enhancers. VAR-dendrimer complexes were prepared by solvent evaporation technique using four dendrimer generations (G4.5, G5, G5.5 and G6) at three concentrations (190 nM, 380 nM and 950 nM). The systems were evaluated for intermolecular interactions, particle size, zeta potential, drug entrapment efficiency percentages (EE%) and drug released percentages after 2 h (Q_2h) and 24 h (Q_24h). The results were statistically analyzed, and the system showing the highest desirability was selected for further pharmacokinetic studies in rabbits, in comparison to Levitra^® tablets. The highest desirability (0.82) was achieved with D10 system comprising VAR (10 mg) and G6 (190 nM). It possessed small particle size (113.85 nm), low PDI (0.19), positive zeta potential (+21.53), high EE% (75.24%), promising Q_2 h (41.45%) and Q_24 h (74.05%). Compared to Levitra^® tablets, the significantly (p < 0.01) delayed T_max, prolonged MRT_(0-∞) and higher relative bioavailability (3.7-fold) could clarify the dual potential of D10 as a sustained release system capable of enhancing VAR oral bioavailability.

Cancer drug delivery in the nano era: An overview and perspectives (Review)

Nanomaterials are increasingly used as drug carriers for cancer therapy. Nanomaterials also appeal to researchers in the areas of cancer diagnosis and biomarker discovery. Several antitumor nanodrugs are currently being tested in preclinical and clinical trials and show promise in therapeutic and other settings. We review the development of nanomaterial drug carriers, including liposomes, polymer nanoparticles, dendritic polymers, and nanomicelles, for the diagnosis and treatment of various cancers. The prospects of nanomaterials as drug carriers for future clinical applications are also discussed.

Dendrimer nanohybrid carrier systems: an expanding horizon for targeted drug and gene delivery

Highly controllable dendritic structural design means dendrimers are a leading carrier in drug delivery applications. Dendrimer- and other nanocarrier-based hybrid systems are an emerging platform in the field of drug delivery. This review is a compilation of increasing reports of dendrimer interactions, such as dendrimer-liposome, dendrimer-carbon-nanotube, among others, known as hybrid carriers. This should prompt entirely new research with promising results for these hybrid carriers. It is assumed that such emerging hybrid nanosystems - from combining two already-established drug delivery platforms - could lead the way for the development of newer delivery systems with multiple applicability for latent theranostic applications in the future.

The intriguing journey of gH625-dendrimers

The knowledge of the mechanism used by vectors to gain access to cell interiors is key to the development of effective drug delivery tools for different pathologies.

Microbial biosensors to monitor the encapsulation effectiveness of Doxorubicin in chimeric advanced Drug Delivery Nano Systems: A calorimetric approach

The release of the anticancer drug doxorubicin (DOX) incorporated in a new drug carrier, namely a chimeric nanosystem formed by liposomes and dendrimers, was studied following the influence of the drug on the growth kinetics of the Lactobacillus helveticus bacterium, that would mimic the intestinal microflora. The bacterial growth was followed at 37°C by means of Isothermal Titration Calorimetry (ITC) and the method was assessed to monitor the overall effect of the delivered drug obtaining simple objective parameters to define the encapsulation effectiveness of the system, discriminating dose effects even in cases of very low release. Traditional microbiological investigations and in vitro release tests were also performed in parallel for validation. The achieved results suggest that L. helveticus is an excellent candidate as biosensor to assess the sealing effectiveness of these DOX drug carriers through ITC investigations. This approach can be extended for quantitative comparison of drug delivery systems with the same drug inserted in other supramolecular bodies for quantitative comparison. The peculiar results for the DOX drug carrier system investigated, indicate also that, the use of hydrophilic dendrimers in this case, produce a high sealing effect that seems promising in terms of the intestinal flora protection.

Elucidation of the interaction mechanism with liposomes of gH625-peptide functionalized dendrimers

We have demonstrated that amide-based dendrimers functionalized with the membrane-interacting peptide gH625 derived from the herpes simplex virus type 1 (HSV-1) envelope glycoprotein H enter cells mainly through a non-active translocation mechanism. Herein, we investigate the interaction between the peptide-functionalized dendrimer and liposomes composed of PC/Chol using fluorescence spectroscopy, isothermal titration calorimetry, and surface plasmon resonance to get insights into the mechanism of internalization. The affinity for the membrane bilayer is very high and the interaction between the peptide-dendrimer and liposomes took place without evidence of pore formation. These results suggest that the presented peptidodendrimeric scaffold may be a promising material for efficient drug delivery.

Interaction of cationic carbosilane dendrimers and their complexes with siRNA with erythrocytes and red blood cell ghosts

We have investigated the interactions between cationic NN16 and BDBR0011 carbosilane dendrimers with red blood cells or their cell membranes. The carbosilane dendrimers used possess 16 cationic functional groups. Both the dendrimers are made of water-stable carbon-silicon bonds, but NN16 possesses some oxygen-silicon bonds that are unstable in water. The nucleic acid used in the experiments was targeted against GAG-1 gene from the human immunodeficiency virus, HIV-1. By binding to the outer leaflet of the membrane, carbosilane dendrimers decreased the fluidity of the hydrophilic part of the membrane but increased the fluidity of the hydrophobic interior. They induced hemolysis, but did not change the morphology of the cells. Increasing concentrations of dendrimers induced erythrocyte aggregation. Binding of short interfering ribonucleic acid (siRNA) to a dendrimer molecule decreased the availability of cationic groups and diminished their cytotoxicity. siRNA-dendrimer complexes changed neither the fluidity of biological membranes nor caused cell hemolysis. Addition of dendriplexes to red blood cell suspension induced echinocyte formation.

Effect of physiological media on the stability of surface-adsorbed DNA-dendron-gold nanoparticles

Plasmid DNA was adsorbed onto 87-nm gold nanoparticles to which were adsorbed a layer of novel cationic dendrons. The behaviour of this DNA-dendron-gold system in cell culture media has been described. Adsorption onto the gold nanoparticles of lipophilic cationic dendrons, with either 8 [(C12)3Lys7(NH2)8] or 16 [(C12)3Lys15(NH2)16] free amino groups on their outer surfaces and incorporating a nuclear localization signal peptide (NLS), resulted in positively charged nanoparticles with a corresponding small increase in particle size. Evidence suggested that the interaction between the gold nanoparticles and the dendron was mediated by hydrophobic forces. With an increase in ionic strength, the apparent particle size of the dendron-stabilized-gold particles increased, but at higher salt concentrations than plain gold sols. Addition of plasmid DNA did not markedly reduce the surface potential of the dendron-gold complex but resulted in an approximately 10–20% increase in hydro-dynamic diameter. Increasing ionic strength increased the apparent size of the DNA-dendron-gold particles, up to a maximum diameter of approximately 900 nm. Importantly, in cell culture media the size of the DNA-dendron-gold nanoparticles increased markedly, as surface potential was reduced. The presence of serum components partially ameliorated these effects, possibly due to steric stabilization of the particles. Release of the DNA from the complex was compromised in cell culture media (compared with water). This, coupled with the flocculation of the carrier, demonstrated the importance of testing delivery systems in the presence of relevant physiologically based fluids before cell culture or in-vivo studies.

An intrinsically fluorescent dendrimer as a nanoprobe of cell transport

Dendrimers, spherical or quasi-spherical synthetic polymers in the nano-size range, have found useful applications as prospective carriers in drug and gene delivery. The investigation of dendrimer uptake by cells has been previously achieved by the incorporation of a fluorescent dye to the dendrimer either by chemical conjugation or by physical interaction. Here we describe the synthesis of two intrinsically fluorescent lysine based cationic dendrimers which lack a fluorophore, but which has sufficient fluorescence intensity to be detected at low concentrations. The nomenclature used to describe our compounds results in, for example the 6th generation dendrimer being notated as Gly-Lys(63) (NH2)(64); Gly denotes that the compound has a glycine in the core coupled to 63 lysine branching units (Lys(63)) and that the surface has 64 free amino groups (NH2)(64). The use of these dendrimers in probing transport avoids the need for fluorescent tagging with its attendant problems. The uptake of Gly-Lys(63) (NH2)(64) into Caco-2 cells was followed using confocal microscopy. Being cationic, it first adsorbs to the cell surface, enters the cytoplasm and reaches the nucleus within 35-45 min. Estimates of the diffusion coefficient of the dendrimer within the cell cytoplasm leads to a value of 6.27 ( +/- 0.49) x 10(-11) cm(2) s(-1), which is up to 1000 times lower than the diffusion coefficient of the dendrimer in water. Intrinsically fluorescent dendrimers of different size and charge are useful probes of transport in cells.

Interaction of polycationic polymers with supported lipid bilayers and cells: nanoscale hole formation and enhanced membrane permeability

Interactions of polycationic polymers with supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers and live cell membranes (KB and Rat2) have been investigated using atomic force microscopy (AFM), cytosolic enzyme assays, confocal laser scanning microscopy (CLSM), and a fluorescence-activated cell sorter (FACS). Polycationic polymers poly-L-lysine (PLL), polyethylenimine (PEI), and diethylaminoethyl-dextran (DEAE-DEX) and sphere-like poly(amidoamine) (PAMAM) dendrimers are employed because of their importance for gene and drug delivery. AFM studies indicate that all the polycationic polymers cause the formation and/or expansion of preexisting defects in supported DMPC bilayers in the concentration range of 1-3 microg/mL. By way of contrast, hydroxyl-containing neutral linear poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA) do not induce hole formation or expand the size of preexisting defects in the same concentration range. All polymers tested are not toxic to KB or Rat2 cells up to a 12 microg/mL concentration (XTT assay). In the concentration range of 6-12 microg/mL, however, significant amounts of the cytosolic enzymes lactate dehydrogenase (LDH) and luciferase (LUC) are released. PEI, which possesses the greatest density of charged groups on its chain, shows the most dramatic increase in membrane permeability. In addition, treatment with polycationic polymers allows the small dye molecules propidium idodide (PI) and fluorescein (FITC) to diffuse in and out of the cells. CLSM images also show internalization of PLL labeled with FITC dye. In contrast, controls of membrane permeability using the neutral linear polymers PEG and PVA show dramatically less LDH and LUC leakage and no enhanced dye diffusion. Taken together, these data are consistent with the hypothesis that polycationic polymers induce the formation of transient, nanoscale holes in living cells and that these holes allow a greatly enhanced exchange of materials across the cell membrane.

Growth of multi-amine terminated poly(amidoamine) dendrimers on the surface of carbon nanotubes

An in situ repetitive divergent polymerization strategy was employed to grow multi-amine poly(amidoamine) dendritic macromolecules on the surfaces of multiwalled carbon nanotubes (MWNTs), affording novel three-dimensional (3D) molecular nanocomposites. The crude MWNTs were oxidized using H(2)SO(4)/HNO(3) = 3:1 (v/v) and then reacted with thionyl chloride, resulting in MWNTs functionalized with chlorocarbonyl groups (MWNT-COCl). MWNT-COCl, when reacted with an excess of ethylenediamine, produced amine-functionalized MWNT supported initiators (MWNT-NH(2)). Using the MWNT-NH(2) as the growth supporter and methylacrylate/ethylenediamine as building blocks, multi-amine dendritic poly(amidoamine) macromolecules were covalently grafted onto the sidewalls and ends of MWNTs via Michael addition reaction and amidation. Thermal gravimetric analysis (TGA) measurements showed that the weight ratio of the as-grown dendritic polymers on the MWNT surfaces lay in the 10%-50% range. The products were also characterized by Fourier transform infrared (FTIR), Raman, nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM) analysis. The results indicate that the dendrimers are grafted onto the surface of MWNTs. The as-prepared nanocomposites exhibit excellent dispersibility in water.

Monovalent and polyvalent carbohydrate inhibitors of ricin binding to a model of the cell-surface receptor

A selection of galactose and lactose analogues was evaluated for their potency in inhibiting the binding of ricin to immobilised asialofetuin, which is a model of the cell-surface receptor for ricin. The aim was to identify compounds that could be used as antagonists of ricin toxicity in vivo, and as more selective, and therefore safer, antitoxins. Although one of these analogues had been identified by molecular modelling in a previous study as a potentially potent inhibitor, it and the other carbohydrates studied were less effective than galactose and lactose themselves (I(50) = 1.39 and 0.74 mM, respectively). In an attempt to increase the potency of carbohydrate-based inhibitors, galactose was coupled to the surface of dendrimers. No synergistic interactions were observed from this multivalent approach. Encouraging results, however, were obtained with a self-assembled lyotropic mesophase gel containing novel synthetic galactose-based surfactants, which was able to sequester ricin from aqueous solution in a 2-phase system.

The breakdown of bilayer lipid membranes by dendrimers

The BLM-system for studying the electrophysical properties of bilayer lipid membranes (BLM) was applied to investigate interactions between polyamidoamine (PAMAM) dendrimers and lipid bilayers. The cationic PAMAM G5 dendrimer effectively disrupted planar phosphatidylcholine membranes, while the hydroxyl PAMAM-OH G5 and carboxyl PAMAM G4.5 dendrimers had no significant effect on them.

Doxorubicin–PAMAM dendrimer complex attached to liposomes: Cytotoxic studies against human cancer cell lines

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 degrees 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.

Dendrimer interactions with hydrophobic fluorescent probes and human serum albumin

The interactions between three types of polyamidoamine dendrimers (with anionic, cationic, and neutral charge on a surface) and fluorescent dye 1-anilinonaphthalene-8-sulfonate (ANS) were studied. Double fluorimetric titration method was employed to estimate a binding constant and the number of binding centers. As fluorescent probes can serve as models of toxin molecules, dendrimers, and human serum albumin (HSA) abilities to bind ANS were compared. In the presence of HSA and dendrimers, ANS located both in HSA and in dendrimers, but the interactions between ANS and HSA were stronger.

Interactions between liposomes and cations in aqueous solution

An investigation on the dependence of electrophoretic mobilities of unilamellar vesicles of phosphatidylcholine-cholesterol-phosphatidylinositol (PC-Chol-PI) on the concentration of several cations with variations in the relation charge/radius in the range Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, and La3+ has been realized. Plots of zeta potential against ion concentration exhibit a maximum for all the cations under study, the position of the maximum is greatly affected by the charge of the ion. From the feature of these plots two phenomenon were observed: an initial binding of cations into the slipping plane for ion concentration below the maximum and a phenomenon of vesicle association for concentration above the maximum. To confirm these observations measurements on dynamic light scattering were performed to obtain the corresponding size distribution of the liposomes at different ion concentrations. Finally the ability of the Stern isotherm to describe the adsorption of the cations to vesicles was tested by two methods. The two main parameters of the theory: the total number of adsorption sites per unit area, N1, and the equilibrium constant, K; (and consequently the free energy of adsorption, deltaG0ads) were calculated for the different ions, showing good agreement. The equilibrium constants of adsorption have been found to obey a linear relationship with ion radius the slope of which decreases with the ion charge.

A Novel Dendrimeric "Glue" for Adhesion of Phosphatidyl Choline-Based Liposomes

The interaction of phosphatidyl choline-cholesterol liposomes incorporating dihexadecyl phosphate as recognizable lipid with complementary guanidinylated diaminobutane poly(propylene imine) dendrimers of the fourth and fifth generation afforded liposome-dendrimer aggregates which were redispersed by the addition of an excess of a phosphate buffer. The higher generation dendrimeric derivative proved more effective when interacted with liposomes. This behavior was attributed to multivalent effects, which, as generally established, enhance the reactivity of multifunctional particles. Turbidimetry, atomic force microscopy (AFM) and optical microscopy were used for investigating the interaction of the complementary particles while the redispersion of the aggregates was studied by transmission electron microscopy (TEM). Liposomal membrane stability in the collapse and redispersion processes was assessed by the calcein fluorescence method, TEM, and AFM.

Peptide dendrimers: applications and synthesis

Peptide dendrimers are radial or wedge-like branched macromolecules consisting of a peptidyl branching core and/or covalently attached surface functional units. The multimeric nature of these constructs, the unambiguous composition and ease of production make this type of dendrimer well suited to various biotechnological and biochemical applications. Applications include use as biomedical diagnostic reagents, protein mimetics, anticancer and antiviral agents, vaccines and drug and gene delivery vehicles. This review focuses on the different types of peptide dendrimers currently in use and the synthetic methods commonly employed to generate peptide dendrimers ranging from stepwise solid-phase synthesis to chemoselective and orthogonal ligation.

Effect of dendrimer on entrapment and release of bioactive from liposomes

An active encapsulation method to obtain high entrapment in liposomes is described. The method harnesses the ability of dendrimer to interact with oppositely charged phospholipid and solubilize acidic drugs in their interior. The high drug entrapment in liposomes is due to the enhanced entrapment of dendrimer, which creates sink in the liposomal aqueous compartment where the methotrexate (MTX) molecules are fluxed in. The encapsulation increases with dendrimer generation. The release of bioactive was also decreased by this method. The method may be useful to entrap drugs with relatively high therapeutic dose.