Targeting cancer cells with biotin-dendrimer conjugates

Dendrimer pharmacokinetics: the effect of size, structure and surface characteristics on ADME properties

Dendrimers show increasing promise as drug-delivery vectors and can be generated with a wide range of scaffold structures, sizes and surface functionalities. To this point, the majority of studies of dendrimer-based drug-delivery systems have detailed pharmacodynamic outcomes, or have followed the pharmacokinetics of a solubilized or conjugated drug. By contrast, detailed commentary on the in vivo fate of the dendrimer carrier is less evident, even though the pharmacokinetics of the carrier will likely dictate both pharmacodynamic and toxicokinetic outcomes. In the current article, the influence of size, structure and surface functionality on the absorption, distribution, metabolism and elimination (ADME) properties of dendrimers have been examined and the implications of these findings for delivery system design are discussed.

The in vivo antitumor activity of LHRH targeted methotrexate-human serum albumin nanoparticles in 4T1 tumor-bearing Balb/c mice

The use of targeted drug delivery systems is a growing trend in cancer treatment to decrease the adverse effect of anti-cancer drugs. In this study, we sought to conjugate methotrexate-human serum albumin nanoparticles (MTX-HSA NPs) with luteinizing-hormone releasing hormone (LHRH). The LHRH was intended to target LHRH receptors overexpressed on the several types of tumors. The expression of LHRH receptors on the 4T1 breast cancer cells was confirmed by FITC conjugated LHRH receptor antibody using fluorescence microscopy. Female Balb/c mice bearing 4T1 breast cancer tumor were treated with a single i.v. injection of free MTX, non-targeted MTX-HSA NPs and LHRH targeted MTX-HSA NPs. LHRH targeted MTX-HSA nanoparticles showed stronger anti-tumor activity in vivo. By 7 days after treatment, average tumor volume in the LHRH targeted MTX-HSA NPs treated group decreased to 8.67% of the initial tumor volume when the number of attached LHRH molecules on MTX-HSA NPs was the highest, while the average tumor volume in non-targeted MTX-HSA NPs treated mice grew rapidly and reached 250.7% of the initial tumor volume 7 days after the treatment. LHRH targeted MTX-HSA NPs could significantly extend the survival time of tumor bearing mice compared with the non-targeted MTX-HSA NPs and free MTX formulations.

Synthesis of new troglitazone derivatives: anti-proliferative activity in breast cancer cell lines and preliminary toxicological study

Breast cancer is the most prevalent cancer in women. The development of resistances to therapeutic agents and the absence of targeted therapy for triple negative breast cancer motivate the search for alternative treatments. With this aim in mind, we synthesised new derivatives of troglitazone, a compound which was formerly used as an anti-diabetic agent and which exhibits anti-proliferative activity on various cancer cell lines. Among the compounds prepared, some displayed micromolar activity against hormone-dependent and hormone-independent breast cancer cells. Furthermore, the influence of the compounds on the viability of primary cultures of human hepatocytes was evaluated. This enabled us to obtain for the first time interesting structure-toxicity relationships in this family of compounds, resulting in 6b and 8b, which show good anti-proliferative activities and poor toxicity towards hepatocytes, compared to troglitazone.

A novel improved therapy strategy for diabetic nephropathy: targeting AGEs

Diabetic nephropathy (DN), is a disorder that causes significant morbidity and mortality. Studies on the pathological mechanisms of DN reveal that advanced glycation end products (AGEs) play an important role in the pathogenesis of DN through interacting with receptors for advanced glycation end products (RAGE), which activate a series of intracellular signaling pathways. AGEs and RAGE have therefore been considered to be two potential key targets. Although multiple studies have been made for anti-DN therapy against AGEs or RAGE, the results have been disappointing due to poor effectiveness or to side effects in clinical practice. In this hypothesis article, we propose a novel treatment based on a dual-target approach. A kind of multi-functional intelligent nanoparticle is constructed, which has a core-shell nanoparticle structure to load the dual-target drugs (AGEs inhibitors and RAGE inhibitors), and has a functional "RAGE analog" to be used as "bait" to catch AGEs and target them to the kidney. Owing to its advantages of having a dual-target, synergistic effect and high efficiency, the proposition may have potential applications in DN therapy.

Inclusion complexes of isoflavones with two commercially available dendrimers: Solubility, stability, structures, release behaviors, cytotoxicity, and anti-oxidant activities

We prepared and characterized the inclusion complexes of daidzein with poly(amidoamine) (PAMAM) and poly(propylene imine) (PPI) dendrimers. Aqueous solubility of daidzein was significantly enhanced by both PAMAM and PPI (186- and 650-fold at 0.36mM, respectively). Daidzein in G3 PAMAM solution is more stable than that in G4 PPI. NMR studies reveal the encapsulation of daidzein within the interior cavities of PPI through hydrophobic interactions. Daidzein exhibits a slower release behavior from PPI than that from PAMAM. PPI/daidzein complex is much more toxic than PAMAM/daidzein complex on several cell lines. PAMAM/daidzein complexes showed similar protective effect on oxidative stress-induced cytotoxicity as compared to free daidzein. These results suggest that the inclusion of daidzein with dendrimer can effectively improve the solubility, prolong the delivery, and maintain the anti-oxidant activity of daidzein. This research provides new insights into dendrimer-based drug delivery systems and will be helpful for the design of novel dendrimer/drug formulations.

Advances in lymphatic imaging and drug delivery

Cancer remains the second leading cause of death after heart disease in the US. While metastasized cancers such as breast, prostate, and colon are incurable, before their distant spread, these diseases have invaded the lymphatic system as a first step in their progression. Hence, proper evaluation of the disease state of the lymphatics which drain a tumor site is crucial to staging and the formation of a treatment plan. Current lymphatic imaging modalities with visible dyes and radionucleotide tracers offer limited sensitivity and poor resolution; however, newer tools using nanocarriers, quantum dots, and magnetic resonance imaging promise to vastly improve the staging of lymphatic spread without needless biopsies. Concurrent with the improvement of lymphatic imaging agents, has been the development of drug carriers that can localize chemotherapy to the lymphatic system, thus improving the treatment of localized disease while minimizing the exposure of healthy organs to cytotoxic drugs. This review will focus on the use of various nanoparticulate and polymeric systems that have been developed for imaging and drug delivery to the lymph system, how these new devices improve upon current technologies, and where further improvement is needed.

Use of biotin targeted methotrexate-human serum albumin conjugated nanoparticles to enhance methotrexate antitumor efficacy

Biotin molecules could be used as suitable targeting moieties in targeted drug delivery systems against tumors. To develop a biotin targeted drug delivery system, we employed human serum albumin (HSA) as a carrier. Methotrexate (MTX) molecules were conjugated to HSA. MTX-HSA nanoparticles (MTX-HSA NPs) were prepared from these conjugates by cross-linking the HSA molecules. Biotin molecules were then conjugated on the surface of MTX-HSA NPs. The anticancer efficacy of biotin targeted MTX-HSA NPs was evaluated in mice bearing 4T1 breast carcinoma. A single dose of biotin targeted MTX-HSA NPs showed stronger in vivo antitumor activity than non-targeted MTX-HSA NPs and free MTX. By 7 days after treatment, average tumor volume in the biotin targeted MTX-HSA NPs-treated group decreased to 17.6% of the initial tumor volume when the number of attached biotin molecules on MTX-HSA-NPs was the highest. Average tumor volume in non-targeted MTX-HSA NPs-treated mice grew rapidly and reached 250.7% of the initial tumor volume. Biotin targeted MTX-HSA NPs increased the survival of tumor-bearing mice to 47.5 ± 0.71 days and increased their life span up to 216.7%. Mice treated with biotin targeted MTX-HSA NPs showed slight body weight loss (8%) 21 days after treatment, whereas non-targeted MTX-HSA NPs treatment at the same dose caused a body weight loss of 27.05% ± 3.1%.

Catechol polymers for pH-responsive, targeted drug delivery to cancer cells

A novel cell-targeting, pH-sensitive polymeric carrier was employed in this study for delivery of the anticancer drug bortezomib (BTZ) to cancer cells. Our strategy is based on facile conjugation of BTZ to catechol-containing polymeric carriers that are designed to be taken up selectively by cancer cells through cell surface receptor-mediated mechanisms. The polymer used as a building block in this study was poly(ethylene glycol), which was chosen for its ability to reduce nonspecific interactions with proteins and cells. The catechol moiety was exploited for its ability to bind and release borate-containing therapeutics such as BTZ in a pH-dependent manner. In acidic environments, such as in cancer tissue or the subcellular endosome, BTZ dissociates from the polymer-bound catechol groups to liberate the free drug, which inhibits proteasome function. A cancer-cell-targeting ligand, biotin, was presented on the polymer carriers to facilitate targeted entry of drug-loaded polymer carriers into cancer cells. Our study demonstrated that the cancer-targeting drug-polymer conjugates dramatically enhanced cellular uptake, proteasome inhibition, and cytotoxicity toward breast carcinoma cells in comparison with nontargeting drug-polymer conjugates. The pH-sensitive catechol-boronate binding mechanism provides a chemoselective approach for controlling the release of BTZ in targeted cancer cells, establishing a concept that may be applied in the future toward other boronic acid-containing therapeutics to treat a broad range of diseases.

Prodrugs for improving tumor targetability and efficiency

As the mainstay in the treatment of various cancers for several decades, chemotherapy is successful but still faces challenges including non-selectivity and high toxicity. Improving the selectivity is therefore a critical step to improve the therapeutic efficacy of chemotherapy. Prodrug is one of the most promising approaches to increase the selectivity and efficacy of a chemotherapy drug. The classical prodrug approach is to improve the pharmaceutical properties (solubility, stability, permeability, irritation, distribution, etc.) via a simple chemical modification. This review will focus on various targeted prodrug designs that have been developed to increase the selectivity of chemotherapy drugs. Various tumor-targeting ligands, transporter-associated ligands, and polymers can be incorporated in a prodrug to enhance the tumor uptake. Prodrugs can also be activated by enzymes that are specifically expressed at a higher level in tumors, leading to a selective anti-tumor effect. This can be achieved by conjugating the enzyme to a tumor-specific antibody, or delivering a vector expressing the enzyme into tumor cells.

Polylactide-co-glycolide nanoparticles for controlled delivery of anticancer agents

The effectiveness of anticancer agents may be hindered by low solubility in water, poor permeability, and high efflux from cells. Nanomaterials have been used to enable drug delivery with lower toxicity to healthy cells and enhanced drug delivery to tumor cells. Different nanoparticles have been developed using different polymers with or without surface modification to target tumor cells both passively and/or actively. Polylactide-co-glycolide (PLGA), a biodegradable polyester approved for human use, has been used extensively. Here we report on recent developments concerning PLGA nanoparticles prepared for cancer treatment. We review the methods used for the preparation and characterization of PLGA nanoparticles and their applications in the delivery of a number of active agents. Increasing experience in the field of preparation, characterization, and in vivo application of PLGA nanoparticles has provided the necessary momentum for promising future use of these agents in cancer treatment, with higher efficacy and fewer side effects.

Effects of a cationic PAMAM dendrimer on photosynthesis and ROS production of Chlamydomonas reinhardtii

Poly(amidoamine) (PAMAM) dendrimers hold great promises for biomedicine. This study sought to examine the toxicity of generation 4 (G4) cationic PAMAM dendrimer to the green microalga, Chlamydomonas reinhardtii, using physiological and molecular biomarkers. Results revealed that the G4 dendrimer at 15 and 25 nM stimulated the photosynthetic process and the production of reactive oxygen species (ROS) in algae. However, the over-production of ROS did not induce the expression of antioxidant enzyme genes, catalase and glutathione peroxidase. In addition, genes encoding light-harvesting proteins (lhca and lhcb), a ferredoxin (fdx) and an oxygen-evolving enhancer protein (psb) involved in photosynthesis were repressed after treatment. Nevertheless, the expression of the lhcbm9 gene, encoding a major light harvesting polypeptide, was increased. These results suggest that the strong modulation of photosynthesis induced by the dendrimer could lead to elevated ROS levels in microalgae.

New functional degradable and bio-compatible nanoparticles based on poly(malic acid) derivatives for site-specific anti-cancer drug delivery

Design of an efficient site-specific drug delivery system based on degradable functional polymers still remains challenging. In this work, we synthesized and characterized three degradable functional polyesters belonging to the poly(malic acid) family: the poly(benzyl malate) (PMLABe), the poly(ethylene glycol)-b-poly(benzyl malate) (PEG(42)-b-PMLABe), the biotin-poly(ethylene glycol)-b-poly(benzyl malate) (Biot-PEG(62)-PMLABe). Starting from these building blocks, we were able to prepare the corresponding well-defined degradable functional nanoparticles whose toxicity was evaluated in vitro on normal and cancer cell lines. Results have evidenced that the prepared nanoparticles did not show any significant cytotoxicity even at high concentrations. A model anti-cancer drug (doxorubicin, Dox) or a fluorescent probe (1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine, DiD oil) has been encapsulated into PMLABe, PEG(42)-PMLABe or Biot-PEG(62)-PMLABe based nanoparticles in order to evaluate, respectively, the in vitro cytotoxicity of Dox-loaded nanoparticles on normal and cancer cell lines and the ligand (biotin) effect on cellular uptake in vitro using mmt 060562 cell line. Dox-loaded PMLABe, PEG(42)-PMLABe or Biot-PEG(62)-PMLABe nanoparticles showed an in vitro cytotoxicity similar to that of free Dox. Moreover, the DiD oil loaded Biot-PEG(62)-PMLABe based nanoparticles showed a better in vitro cellular uptake than ligand-free DiD oil loaded nanoparticles. Both results evidence the great potential of such degradable functional poly(malic acid) derivatives for the design of highly efficient site-specific anti-cancer nanovectors.

Design of biocompatible dendrimers for cancer diagnosis and therapy: current status and future perspectives

In the past decade, nanomedicine with its promise of improved therapy and diagnostics has revolutionized conventional health care and medical technology. Dendrimers and dendrimer-based therapeutics are outstanding candidates in this exciting field as more and more biological systems have benefited from these starburst molecules. Anticancer agents can be either encapsulated in or conjugated to dendrimer and be delivered to the tumour via enhanced permeability and retention (EPR) effect of the nanoparticle and/or with the help of a targeting moiety such as antibody, peptides, vitamins, and hormones. Imaging agents including MRI contrast agents, radionuclide probes, computed tomography contrast agents, and fluorescent dyes are combined with the multifunctional nanomedicine for targeted therapy with simultaneous cancer diagnosis. However, an important question reported with dendrimer-based therapeutics as well as other nanomedicines to date is the long-term viability and biocompatibility of the nanotherapeutics. This critical review focuses on the design of biocompatible dendrimers for cancer diagnosis and therapy. The biocompatibility aspects of dendrimers such as nanotoxicity, long-term circulation, and degradation are discussed. The construction of novel dendrimers with biocompatible components, and the surface modification of commercially available dendrimers by PEGylation, acetylation, glycosylation, and amino acid functionalization have been proposed as available strategies to solve the safety problem of dendrimer-based nanotherapeutics. Also, exciting opportunities and challenges on the development of dendrimer-based nanoplatforms for targeted cancer diagnosis and therapy are reviewed (404 references).

Controlled drug release through a plasma polymerized tetramethylcyclo-tetrasiloxane coating barrier

A plasma polymerized tetramethylcyclo-tetrasiloxane (TMCTS) coating was deposited onto a metallic biomaterial, 316 stainless steel, to control the release rate of drugs, including daunomycin, rapamycin and NPC-15199 (N-(9-fluorenylmethoxy-carbonyl)-leucine), from the substrate surface. The plasma-state polymerized TMCTS thin film was deposited in a vacuum plasma reactor operated at a radio-frequency of 13.56 MHz, and was highly adhesive to the stainless steel, providing a smooth and hard coating layer for drugs coated on the substrate. To investigate the influence of plasma coating thickness on the drug diffusion profile, coatings were deposited at various time lengths from 20 s to 6 min, depending on the type of drug. Atomic force spectroscopy (AFM) was utilized to characterize coating thickness. Drug elution was measured using a spectrophotometer or high-performance liquid chromatography (HPLC) system. The experimental results indicate that plasma polymerized TMCTS can be used as an over-coating to control drug elution at the desired release rate. The drug-release rate was also found to be dependent on the molecular weight of the drug with plasma coating barrier on top of it. The in vitro cytotoxicity test result suggested that the TMCTS plasma coatings did not produce a cytotoxic response to mammalian cells. The non-cytotoxicity of TMCTS coating plus its high thrombo-resistance and biocompatibility are very beneficial to drug-eluting devices that contact blood.

Radiosynthesis, biodistribution and micro-SPECT imaging study of dendrimer-avidin conjugate

Partially acetylated generation five polyamidoamine (PAMAM) dendrimer (G5-Ac) was reacted with biotin and 2-(p-isothiocyanatobenzyl)-6-methyl-diethylenetria minepentaacetic acid (1B4M-DTPA), respectively to form the complex Bt-G5-Ac-1B4M which was further conjugated with avidin to give the conjugate Av-G5-Ac-1B4M. Then both of the conjugates were radiolabeled with technetium-99m ((99m)Tc), respectively. Their in vitro cellular uptake study shows that the conjugate of Av-G5-Ac-1B4M-(99m)Tc exhibits much higher cellular uptake in HeLa cells than that of Bt-G5-Ac-1B4M-(99m)Tc. Accordingly the following evaluation such as in vitro/in vivo stability, biodistribution and micro-SPECT imaging was observed only for the conjugate of Av-G5-Ac-1B4M-(99m)Tc.

Prodrug-based intracellular delivery of anticancer agents

There are numerous anticancer agents based on a prodrug approach. However, no attempt has been made to review the ample available literature with a specific focus on the altered cell uptake pathways enabled by the conjugation and on the intracellular drug-release mechanisms. This article focuses on the cellular interactions of a broad selection of parenterally administered anticancer prodrugs based on synthetic polymers, proteins or lipids. The report also aims to highlight the prodrug design issues, which are key points to obtain an efficient intracellular drug delivery. The chemical basis of these molecular concepts is put into perspective with the uptake and intracellular activation mechanisms, the in vitro and in vivo proofs of concepts and the clinical results. Several active targeting strategies and stimuli-responsive architectures are discussed throughout the article.

Novel peptide-dendrimer conjugates as drug carriers for targeting nonsmall cell lung cancer

Phage display technology has been demonstrated to be a powerful tool for screening useful ligands that are capable of specifically binding to biomarkers on the surface of tumor cells. The ligands found by this technique, such as peptides, have been successfully applied in the fields of early cancer diagnostics and chemotherapy. In this study, a novel nonsmall cell lung cancer-targeting peptide (LCTP, sequence RCPLSHSLICY) was screened in vivo using a Ph.D.-C7C(™) phage display library. In order to develop a universal tumor-targeting drug carrier, the LCTP and fluorescence-labeled molecule (FITC) were conjugated to an acetylated polyamidoamine (PAMAM) dendrimer of generation 4 (G4) to form a PAMAM-Ac-FITC-LCTP conjugate. The performance of the conjugate was first tested in vitro. In vitro results of cell experiments analyzed by flow cytometry and inverted fluorescence microscopy indicated that PAMAM-Ac-FITC-LCTP was enriched more in NCI-H460 cells than in 293T cells, and cellular uptake was both time- and dose-dependent. The tissue distribution of the conjugate in athymic mice with lung cancer xenografts was also investigated to test the targeting efficiency of PAMAM-Ac-FITC-LCTP in vivo. The results showed that LCTP can effectively facilitate the targeting of PAMAM-Ac-FITC-LCTP to nonsmall cell lung cancer cells and tumors. These results suggest that the LCTP-conjugated PAMAM dendrimer might be a promising drug carrier for targeted cancer diagnosis and treatment.

Self-assembled terplexes for targeted gene delivery with improved transfection

To improve transfection efficiency and to incorporate target ligands to the gene delivery systems, heparin and heparin-biotin were introduced to complexes of polyamidoamine dendrimer and DNA (PAMAM/DNA) via electrostatic interactions to form self-assembled PAMAM/DNA/heparin and PAMAM/DNA/heparin-biotin terplexes, respectively. The self-assembled terplexes were characterized by agarose gel electrophoresis and particle size analysis. The MTT assay indicated that, after incorporation of heparin and heparin-biotin, the terplexes exhibited decreased cytotoxicity. In addition, as compared with PAMAM/DNA and PAMAM/DNA/heparin complexes, the PAMAM/DNA/heparin-biotin complexes exhibited much higher cellular uptake into HeLa cells due to the specific interactions between biotin and biotin receptors on HeLa cells, which led to the enhanced transfection activity. The PAMAM/DNA/heparin-biotin complexes would be a promising targeting gene delivery system.

Host-guest chemistry of dendrimer-drug complexes. 4. An in-depth look into the binding/encapsulation of guanosine monophosphate by dendrimers

In the present study, we investigated the host-guest chemistry of dendrimer/guanosine monophosphate (GMP) and present an in-depth look into the binding/encapsulation of GMP by dendrimers using NMR studies. (1)H NMR spectra showed a significant downfield shift of methylene protons in the outmost layer of the G5 dendrimer, indicating the formation of ion pairs between cationic amine groups of dendrimer and anionic phosphate groups of GMP. Chemical shift titration results showed that the binding constant between G5 dendrimer and GMP is 17,400 M(-1) and each G5 dendrimer has 107 binding sites. The binding of GMP to dendrimers prevents its aggregation in aqueous solutions and thereby enhances its stability. Nuclear Overhauser effect measurements indicated that a GMP binding and encapsulation balance occurs on the surface and in the interior of dendrimer. The binding/encapsulation transitions can be easily tailored by altering the surface and interior charge densities of the dendrimer. All these findings provide a new insight into the host-guest chemistry of dendrimer/guest complexes and may play important roles in the study of dendrimer/DNA aggregates by a "bottom-up" strategy.

Protective effect of PEGylation against poly(amidoamine) dendrimer-induced hemolysis of human red blood cells

Poly(amidoamine) (PAMAM) dendrimers are widely used in medical applications. However, dendrimers bearing positively charged surface groups are prone to destabilize cell membrane and cause cell lysis. The lytic effect of dendrimers on red blood cells (RBCs) namely hemolysis is extremely dangerous when administered in vivo. To diminish the hematologic toxicity, we modified PAMAM dendrimers with poly(ethylene glycol) (PEG) of three molecular weights (2k, 5k, and 20k). The protective effect of PEGylation against PAMAM dendrimer-induced hemolysis was studied. RBCs morphology and surface structure were analyzed by optical microscopy (OM) and atomic force microscopy (AFM). The results indicated that PAMAM and PEG-2k modified dendrimers induced hemolysis at 0.1 and 0.5 mg/mL respectively, whereas PEG-5k and PEG-20k modified dendrimers showed no significant difference in hemolysis compared with control even at 5 mg/mL. OM and AFM investigation indicated PAMAM and PEG-2k modified dendrimers caused RBCs aggregation and lysis. However, no changes were observed in the overall shape of RBCs treated with PEG-5k and PEG-20k modified dendrimers. The surface roughness of RBCs treated with PEGylated dendrimers were far lower than that of RBCs treated with PAMAM dendrimers. This study demonstrated that hemocompatibility of PAMAM dendrimers could be greatly enhanced by PEGylation.

Synthesis, biodistribution, and microsingle photon emission computed tomography (SPECT) imaging study of technetium-99m labeled PEGylated dendrimer poly(amidoamine) (PAMAM)-folic acid conjugates

Three conjugates based on dendrimer PAMAM generation five were synthesized and radiolabeled successfully. To investigate their tumor targeting, the in vitro and in vivo stability, cell uptake, in vivo biodistribution, and micro-SPECT imaging were evaluated, respectively. The conjugate of (99m)Tc labeled PEGylated dendrimer PAMAM folic acid conjugate ((99m)Tc-G5-Ac-pegFA-DTPA) shows much higher uptake in KB cancer cells and accumulated more in the tumor area than that of the other two conjugates. The uptake in KB cells depends on the incubation time. The results of in vivo biodistribution agree with the data obtained from micro-SPECT imaging. These studies show that PEGylation of PAMAM dendrimer folic acid conjugate improves the tumor targeting. Folate-conjugated dendrimer maybe developed to be potential radiopharmaceuticals and targeted drug delivery systems.

Glycopeptide dendrimer colchicine conjugates targeting cancer cells

Screening of a 65,536-member one-bead-one-compound (OBOC) combinatorial library of glycopeptide dendrimers of structure ((betaGal)(n)(+1)X(8)X(7)X(6)X(5))(2)DapX(4)X(3)X(2)X(1)(beta-Gal)(m) (betaGal=beta-galactosyl-thiopropionic acid, X(8-1)=variable amino acids, Dap=l-2,3-diaminopropionic acid, n, m=0, or 1 if X(8)=Lys resp. X(1)=Lys) for binding of Jurkat cells to the library beads in cell culture, resynthesis and testing lead to the identification of dendrimer J1 (betaGal-Gly-Arg-His-Ala)(2)Dap-Thr-Arg-His-Asp-CysNH(2) and related analogues as delivery vehicles. Cell targeting is evidenced by FACS with fluorescein conjugates such as J1F. The colchicine conjugate J1C is cytotoxic with LD(50)=1.5 microM. The beta-galactoside groups are necessary for activity, as evidenced by the absence of cell-binding and cytotoxicity in the non-galactosylated, acetylated analogue AcJ1F and AcJ1C, respectively. The pentagalactosylated dendrimer J4 betaGal(4)(Lys-Arg-His-Leu)(2)Dap-Thr-Tyr-His-Lys(betaGal)-Cys) selectively labels Jurkat cell as the fluorescein derivative J4F, but its colchicine conjugate J4C lacks cytotoxicity. Tubulin binding assays show that the colchicine dendrimer conjugates do not bind to tubulin, implying intracellular degradation of the dendrimers releasing the active drug.

Size matters: influence of the size of nanoparticles on their interactions with ligands immobilized on the solid surface

The correlation between the size of biotinylated nanoparticles and their affinity in relation to interactions with the solid surface was investigated. The silica particles with a diameter of 50-200 nm containing amino groups on the surface were labeled with different quantities of biotin. The affinity properties of biotinylated nanoparticles were studied using a Biacore 3000 instrument equipped with a streptavidin-coated sensor chip (SA chip). It was shown that the increase in the particle size from 50 to 200 nm reduced the affinity (K(D)) of biotin-streptavidin interactions from 1.2 x 10(-12) to 1.2 x 10(-10) M. It was found that the particles with higher concentrations of immobilized biotin on particle surfaces demonstrated stronger binding with streptavidin.

New troglitazone derivatives devoid of PPARγ agonist activity display an increased antiproliferative effect in both hormone-dependent and hormone-independent breast cancer cell lines

Numerous recent studies indicate that most anticancer effects of PPARγ agonists like thiazolidinediones are the result of PPARγ-independent pathways. These conclusions were obtained by several approaches including the use of thiazolidinedione derivatives like Δ2-Troglitazone (Δ2-TGZ) that does not activate PPARγ. Since biotinylation has been proposed as a mechanism able to increase the specificity of drug delivery to cancer cells which could express a high level of vitamin receptor, a biotinylated derivative of Δ2-TGZ (bΔ2-TGZ) has been synthetized. In the present article, we have studied the in vitro effects of this molecule on both hormone-dependent (MCF-7) and hormone-independent (MDA-MB-231) breast cancer cells. In both cell lines, bΔ2-TGZ was more efficient than Δ2-TGZ to decrease cell viability. bΔ2-TGZ was also more potent than Δ2-TGZ to induce the proteasomal degradation of cyclin D1 in both cell lines and those of ERα in MCF-7 cells. However, in competition experiments, the presence of free biotin in the culture medium did not decrease the antiproliferative action of bΔ2-TGZ. Besides, other compounds that had no biotin but that were substituted at the same position of the phenolic group of the chromane moiety of Δ2-TGZ decreased cell viability similarly to bΔ2-TGZ. Hence, we concluded that the increased antiproliferative action of bΔ2-TGZ was not due to biotin itself but to the functionalization of the terminal hydroxyl group. This should be taken into account for the design of new thiazolidinedione derivatives able to affect not only hormone-dependent but also hormone-independent breast cancer cells in a PPARγ-independent pathway.

Multicharged and/or water-soluble fluorescent dendrimers: properties and uses

The fluorescence of water-soluble dendritic compounds can be due to the whole structure or to fluorophores used as core, as peripheral groups, or as branches. Highly sophisticated precisely defined structures with other functional groups usable for material or biological purposes have been synthesised, but many recent examples have shown that dendrimers can be used as versatile platforms for statistically linking various types of functional groups.