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