targeting molecules the binding of the antibodyconjugated dendrimers to antigenexpressing cells was evaluated by flow cytometry and confocal microscopy allegra allergy alert the conjugates specifically bound to the antigenexpressing cells in a time and dosedependent fashion, with affinity similar to that of the allegra allergy alert free antibody fig, confocal microscopic analysis suggested at least some cellular internalization of the dendrimer conjugate dendrimerantibody conjugates are, therefore, a suitable platform for targeted molecule delivery into antigenexpressing cells monolayers formed by generation ����� dendrimers on a gold surface were functionalized with biotin and produced a biomolecular interface that was m ll id � fig confocal microscopic analysis of hl cells, which allegra allergy alert were incubated h at �c with nm g ����� carrying fluorescence dye and bca antibody on the surface the cells were allegra allergy alert rinsed and confocal images were taken the left and right panels represent the ftc fluorescence and light images taken in the allegra allergy alert same cell the arrow indicates the binding of the conjugate on the cell surface at �c reproduced with permission from allegra allergy alert ref copyright american chemical society capable of binding high levels of avidin avidin binding as high as coverage of the surface allegra allergy alert was observed despite conditions that should cause serious steric hindrance these dendritic monolayers were utilized as a model to study protein allegra allergy alert ligand interactions penicillins the surfaces of ����� dendrimers, generations to , were decorated with ben zylpenicillin in an attempt to develop a allegra allergy alert new in vitro test to quantify ige antibodies to specific lactam conjugates, with the goal of improving the existing methods for allegra allergy alert diagnosing allergy to this type of antibiotic the monodispersity of dendrimers is advantageous over conventional peptide carrier conjugates such as human allegra allergy alert serum albumin nonprecise density of haptens in their structure and polyllysine mixture of heterogeneous molecular weight peptides preliminary radioallergosorbent tests rast, allegra allergy alert using sera from patients allergic to penicillin, have confirmed the usefulness of penicilloylated dendrimers penicillin v was used as a model allegra allergy alert drug containing a carboxylic group and attached to the surface of ����� dendrimers generations and , both containing surface functionalities the allegra allergy alert drug was complexed to the dendrimers via amide or ester bonds it was found in tests using a singlestrain bacterium, staphylococcus allegra allergy alert aureus, that the bioavailability of the penicillin was unaltered after the drug was released from the complex through ester bond hydrolysis allegra allergy alert dendrimers as nanodrugs dendrimers have been studied as antitumor, antiviral and antibacterial drugs the most prominent and advanced example is the allegra allergy alert use of polylysine dendrimers, modified with sulfonated naphthyl groups, as antiviral drugs against the herpes simplex virus such a conjugate based allegra allergy alert on dendritic polylysine scaffolding is vivagel, a topical agent currently under development by starpharma ltd, melbourne, australia, that can potentially preventreduce transmission of hiv and other sexually transmitted diseases stds vivagel spl is being offered as a waterbased gel, with the purpose to prevent hiv from binding to cells in the body the gel differs from physical barriers to stds such as condoms, by exhibiting inhibitory activity against hiv and other stds in july , following submission of an investigational new drug ind application, starpharma gained clearance under us fda regulations to proceed with a phase i clinical study to assess the safety of vivagel in healthy human subjects this phase study, representing for the first time a dendrimer pharmaceutical tested in humans, compared women who allegra allergy alert received either various intravaginal doses of vivagel or a placebo gel daily for one week the trial was double blinded so allegra allergy alert that the volunteers, principal investigator and starpharma did not know who was receiving placebo or vivagel study participants were assessed for allegra allergy alert possible irritant effects of the gel additionally, the women were assessed for any possible effect upon vaginal microflora natural microorganisms in the vagina or absorption into the blood of the active ingredient of vivagel a thorough review of the complete data revealed allegra allergy alert no evidence of irritation or inflammation preclinical development studies had demonstrated that vivagel was effective at preventing infection of primates allegra allergy alert exposed to a humanized strain of simian immunodeficiency virus shiv in earlier studies, it was found that ����� dendrimers covalently modified allegra allergy alert with naphthyl sulfonate residues on the surface, also exhibited antiviral activity against hiv this dendrimerbased nanodrug inhibited early stage viruscell adsorption allegra allergy alert and later stage viral replication, by interfering with reverse transcriptase andor integrase enzyme activities the general mode of action of antibacterial dendrimers is to adhere to and damage the anionic bacterial membrane, causing bacterial lysis ppi dendrimers with tertiary alkyl ammonium groups allegra allergy alert attached to the surface have been shown to be potent antibacterial biocides against gram positive and gram negative bacteria the nature of the counterion is important, as tetraalkylammonium bromides were found to be more potent antibacterials over the corresponding chlorides polylysine dendrimers allegra allergy alert with mannosyl surface groups are effective inhibitors of the adhesion of e coli to horse blood cells in a haemagglutination assay, allegra allergy alert making these structures promising antibacterial agents chitosandendrimer hybrids have been found to be useful as antibacterial agents, carriers in drug allegra allergy alert delivery systems, and in other biomedical applications their behavior have been reviewed very recently triazinebased antibiotics were loaded into dendrimer beads allegra allergy alert at high yields the release of the antibiotic compounds from a single bead was sufficient to give a clear inhibition effect allegra allergy alert in many cases, dendritic constructs were more potent than analogous systems based on hyperbranched polymers the antiprion activity of cationic phosphoruscontaining dendrimers with tertiary amine surface groups has been evaluated clarinex syrup while pregnant these molecules had a strong anti prion activity at nontoxic doses they allegra allergy alert have been found to decrease the amount of effexor prescribed for pain preexisting prpsc from several prion starins, including the bse strain in addition, these allegra allergy alert dendrimers were able to reduce prpsc accumulation in the spleen by more than routes of application most commonly, dendrimers are applied as parenteral injections, either directly into the tumor tissue or intravenous for systemic delivery however, recent oral drug delivery studies using the human colon adenocarcinoma cell line, caco, have indicated that low generation ����� dendrimers cross cell membranes, presumably through a allegra allergy alert combination of two processes, ie paracellular transport and adsorptive endocytosis the pglycoprotein pgp efflux transporter does not effect dendrimers, and therefore, drugdendrimer complexes are able to bypass the efflux transporter furthermore, recent work has shown that ����� dendrimers enhanced the bioavailability of indomethacin in transdermal delivery applications similarly, the drug tamsulosin was used as a model to study transdermal delivery utilizing ����� dendrimers the dendrimers were found to be weak penetration enhancers however, no dendrimerdriven effect was observed for the drugs keto profen and allegra allergy alert clonidine as an explanation, dendrimertriggered drug crystallization within the transdermal delivery matrix was discussed, allowing the formation of drug polymorphs that allegra allergy alert can or cannot facilitate transdermal delivery several ����� dendrimers generations , and with amine, car boxylate and hydroxyl surface groups were studied allegra allergy alert for controlled ocular drug delivery the duration of residence time was evaluated after solubilization of these dendrimers in buffered phosphate allegra allergy alert solutions containing parts per thousand wv of fluorescein the new zealand albino rabbit was used as an in vivo model for allegra allergy alert qualitative and quantitative assessment of ocular tolerance and retention time, after a single application of il of dendrimer solution to the allegra allergy alert eye the same model was also used to determine the prolonged miotic or mydriatic activities of dendrimer solutions, some containing pilocarpine allegra allergy alert nitrate and some tropicamide, respectively residence time was longer for the solutions containing dendrimers with carboxylic and hydroxyl surface groups no allegra allergy alert prolongation of remanence time was observed when dendrimer concentration increased the remanence time of ����� dendrimer solutions on the cornea showed allegra allergy alert size and molecular weight dependency this study allowed novel macromolecular carriers to be designed with prolonged drug residence time for the allegra allergy alert ophthalmic route biocompatibility of dendrimers dendrimers have to exhibit low toxicity and be nonimmunogenic in order to be widely used in allegra allergy alert biomedical applications to date, the cytotoxicity of dendrimers has been primarily studied in vitro, however, a few in vivo studies allegra allergy alert have been published as observed for other cationic macromolecules, including liposomes and micelles, dendrimers with positively charged surface groups are prone allegra allergy alert to destabilize cell membranes and cause cell lysis for example, in vitro cytotoxicity ic measurements ie the concentration where of cell allegra allergy alert lysis is observed for amino terminated ����� dendrimers revealed significant cytotoxicity on human intestinal adenocarcinoma caco cells, furthermore, the cytotoxicity was allegra allergy alert found to be generationdependent, with higher generation dendrimers being the most toxic a similar generation dependence of aminoterminated ����� dendrimers was observed for the haemolytic effect, studied on a solution of rat blood cells however, some recent studies have shown that aminoterminated allegra allergy alert ����� dendrimers exhibit lower toxicity than more flexible aminofunctionalized linear polymers perhaps due to lower adherence of the rigid globular dendrimers to cellular surfaces the degree of substitution, as well as the type of amine functionality, is important, with primary amines being allegra allergy alert more toxic than secondary or tertiary amines aminoterminated ppi and ����� dendrimers behave similarly with regard to cytotoxicity and haemolytic allegra allergy alert effects, including the generationdependent increase of both comparative toxicity studies on anionic carboxylateterminated and cationic aminoterminated ����� dendrimers using caco cells allegra allergy alert have shown a significantly lower cytotoxicity of the anionic compounds in fact, lower generation ����� dendrimers possessing carboxylate surface groups show neither haema totoxicity nor cytotoxicity at concentrations up to mgml the biocompatability of dendrimers is not solely determined by the surface allegra allergy alert groups dendrimers containing an aromatic polyether core and anionic carboxylate surface groups have shown to be haemolytic on a solution of allegra allergy alert rat blood cells after hrs it is suggested that the aromatic interior of the dendrimer may cause haemolysis through hydrophobic membrane allegra allergy alert contact one way to reduce the cytotoxicity of cationic dendrimers may reside in partial surface derivatization with chemically inert functionalities such allegra allergy alert as peg or fatty acids the cytotoxicity towards caco cells can be reduced significantly from ic mm to lmm after allegra allergy alert such a modification this observation can be explained by the reduced overall positive charge of these surfacemodified dendrimers apartial derivatization with as few as six lipid chains or four peg chains on a gpamam, respectively, was sufficient to lower the cytotoxicity substantially allegra allergy alert in studies conducted at dendritic nano technologies, inc using caco and two other cell lines, it was found that besides partial allegra allergy alert pegylation of the surface, surface modification with pyrrolidone, another biocompatible compound, can significantly reduce cytotoxicity to levels far better than those allegra allergy alert of currently available products in some cases, the cytotoxicity of ����� dendrimers could be reduced by additives such as fetal calf allegra allergy alert serum only a few systematic studies on the in vivo toxicity of dendrimers have been reported so far upon injection into allegra allergy alert mice, doses of mgkg of ����� dendrimers up to g = , displaying either unmodified or modified aminoterminated surfaces, did not appear allegra allergy alert to be toxic hydroxy or methoxyterminated dendrimers based on a polyester dendrimer scaffold have been shown to be of low allegra allergy alert toxicity both in vitro and in vivo at very high concentrations mgml, these polyester dendrimers induced some inhibition of cell growth allegra allergy alert in vitro, but no increase in cell death was observed upon injection into mice, no acute or longterm toxicity problems were allegra allergy alert observed the nontoxic properties make these new dendritic motifs very promising candidates for drug delivery devices initial immunogenicity studies performed on allegra allergy alert unmodified aminoterminated ����� dendrimers showed no or weak immunogenicity of the gg dendrimers however, later studies indicated some immunogenicity of these allegra allergy alert dendrimers, which could be reduced by surfacemodification utilizing peg chains conclusions the high level of control over the architecture of dendrimers, their size, shape, branching length and density, and their surface functionality, makes these compounds ideal carriers in drug delivery applications the allegra allergy alert bioactive agents may either be encapsulated into the interior of the dendrimers or they may be chemically attached or physically adsorbed allegra allergy alert onto the dendrimer surface, with the option to tailor the properties of the carrier to the specific needs of the allegra allergy alert active material and its therapeutic applications furthermore, the high density of surface groups allows attachment of targeting groups as well as groups that modify the solution behavior or toxicity of dendrimers surfacemodified dendrimers themselves may act as nanodrugs against tumors, bacteria and allegra allergy alert viruses this review of drug delivery applications of dendrimers clearly illustrates the potential of this new fourth architectural class of polymers allegra allergy alert and substantiates the high optimism for the future of dendrimers in this important field acknowledgments the authors wish to thank all allegra allergy alert contributors to this fascinating field of research, as well as the funding agents that have supported this work over the years allegra allergy alert in particular, dnt would like to acknowledge current funding by the us army research laboratory arl contract # wnf references svenson s controlling surfactant selfassembly curr opin coll interf sci svenson s selfassembly and selforganization important processes � but can we predict them?