Micro chromosomal deletions at the NYS7 locus and autosomal dominant nystagmus.

Nystagmus is an ocular condition characterized by bilateral involuntary ocular oscillation which can severely affect vision. When not associated with other ocular or systemic diseases, it is referred to as idiopathic or congenital motor nystagmus (CMN). Genome-wide linkage studies have previously identified several loci associated with CMN, however the genes responsible for some of these loci have yet to be identified. We have examined a large, five-generation family with autosomal dominant CMN. Our purpose was to characterize the clinical manifestations and reveal the molecular basis of the disease in this family. In addition to full ophthalmic examination and imaging, molecular analysis included copy number variation analysis, linkage studies, and Sanger sequencing. Expression analyses of candidate genes was done by real-time PCR. Of the 68 family members, 27 subjects in five-generations had CMN, in line with an autosomal dominant inheritance pattern. Molecular analysis was performed on 27 members, 15 of them affected by CMN. Copy number variation analysis using array comparative genomic hybridization (aCGH) revealed a novel deletion located on 1q32 (NYS7) among affected individuals. Linkage analysis using polymorphic markers demonstrated full segregation with a heterozygous haplotype in all affected patients, with a LOD score of >5. Sanger sequencing of affected subjects revealed a novel deletion of 732,526 bp in the linkage interval. No protein-coding genes exist within the deleted region; however, the deletion disrupts topologically associated domains encompassing the gene NR5A2 and the non-protein coding MIR181A. Both are strongly associated with other genes expressed in the retina such as PROX1, which in turn is also associated with genes related to nystagmus such as PAX6. We therefore hypothesized that the deletion might affect NR5A2 and MIR181A expression, causing CMN. Expression analysis by real-time PCR showed significantly lower expression of NR5A2, and significantly higher expression of PROX1 among patients compared with controls. To conclude, among a large five-generation family with autosomal dominant CMN, a large deletion in the interval of NYS7 was linked with the disease. No protein-coding genes exist inside the deleted region, and so the exact mechanism in which CMN is caused is uncertain. Based on topological association and expression analyses we suggest a possible mechanism for the pathogenesis.

PSMA-targeted stably linked "dendrimer-glutamate urea-methotrexate" as a prostate cancer therapeutic.

One of the important criteria for achieving efficient nanoparticle-based targeted drug delivery is that the drug is not prematurely released at off-target sites. Here we report the preclinical evaluation of a serum-stable dendrimer-based drug conjugate capable of actively targeting into prostate cancer (PC) cells, delivered through the prostate-specific membrane antigen (PSMA). Multiple molecules of PSMA-binding small molecule glutamate urea (GLA; targeting agent) and the drug methotrexate (MTX) were conjugated to generation 5 PAMAM dendrimer (G5) through Cu-free "click" chemistry. The GLA was conjugated through a stable amide bond, and the MTX was conjugated either through ester (Es)- or amide (Am)-coupling, to generate G5-GLA(m)-(Es)MTX(n) and G5-GLA(m)-(Am)MTX(n), respectively. In serum-containing medium, free MTX was slowly released from "G5-GLA(m)-(Es)MTX(n)", with ~8% MTX released from the dendrimer in 72 h, whereas the MTX on G5-GLA(m)-(Am)MTX(n) was completely stable. The G5-GLA(m)-(Am)MTX(n) bound and internalized into PSMA-expressing LNCaP cells, but not into PSMA-negative PC3 cells. The conjugate-inhibited recombinant dihydrofolate reductase and induced potent cytotoxicity in the LNCaP cells, but not in the PC3 cells. Similar to the action of free GLA, stable amide-linked dendrimer-GLA was capable of inhibiting the enzyme N-acetylated α-linked acidic dipeptidase (NAALADase) activity of PSMA. The G5-GLA(m)-MTX(n) may serve as a serum-stable nanoparticle conjugate to specifically and effectively target and treat PSMA-overexpressing prostate tumors.

Sustained analgesia achieved through esterase-activated morphine prodrugs complexed with PAMAM dendrimer.

PURPOSE: Design and evaluate the in vitro and in vivo efficacy of two extended release morphine formulations developed for IV administration by complexing esterase activated morphine prodrugs to surface-modified, generation 5 (G5) poly(amidoamine) (PAMAM) dendrimer. METHODS: Prodrugs were synthesized, complexed with PAMAM dendrimer, characterized via ultra performance liquid chromatography (UPLC), nuclear magnatic resonance (NMR), and tested in vitro using rat plasma vs. saline control and in an in vivo rat and guinea pig pain model (modified Randall and Selitto test). RESULTS: We demonstrated that complexation with dendrimer allowed the solubilization of the prodrugs for in vivo applications without the need for salt, and that the structural design of the morphine prodrugs allowed the controlled release of morphine which extended the action of morphine-induced analgesia in an animal pain model from 2 h (control) to 6 h (Morphine Prodrug A). CONCLUSION: The concept of complexing/solubilizing appropriately designed esterase-sensitive prodrugs with dendrimer to enhance the sustained release of these drugs may be a useful pharmacokinetic strategy for a range of therapeutics.

Variants in the WDR45 Gene Within the OPA-2 Locus Associate With Isolated X-Linked Optic Atrophy.

Purpose: To describe clinical and molecular findings of two families with X-linked optic atrophy and present two new pathogenic variants in the WDR45 gene. Methods: Case series and molecular analysis of two families of Jewish Ashkenazi descent with early onset bilateral optic atrophy. Whole-exome sequencing (WES) and bioinformatic analysis were performed, followed by Sanger sequencing and segregation analysis. Results: In both families, male siblings (three in family 1, two in family 2) had early-onset isolated bilateral optic atrophy. The sibling's healthy mother (and in the second family also one healthy sister) had a mild presentation, suggesting a carrier state and an X-linked inheritance pattern. All participants were otherwise healthy, apart from mild learning disabilities and autism spectrum disorder in two siblings of the second family. Variants in known optic atrophy genes were excluded. Analysis revealed a point variant in the WDR45 gene-a missense variant in the first family, NM_001029896.2:c.107C>A; NP_001025067.1:p.Pro36His (variant ID: 1704205), and a splice site variant in the second family, NM_001029896.2:c.236-1G>T; NP_009006.2:p.Val80Leu (variant ID: 1704204), located on Xp11.23 (OPA2 locus). Both variants are novel and predicted as pathogenic. In both families, the variant was seen with full segregation with the disease, occurring in all affected male participants and in one allele of the carrier females, as well as none of the healthy participants. Conclusions: Among two families with isolated X-linked optic atrophy, molecular analysis revealed novel variants in the WDR45 gene in full segregation with the disease. This gene resides within the OPA2 locus, previously described to associate with X-linked optic atrophy. Taken together, these findings suggest that certain pathogenic variants in the WDR45 gene are associated with isolated X-linked optic atrophy.

Optical fiber-based in vivo quantification of growth factor receptors.

BACKGROUND: Growth factor receptors such as epidermal growth factor receptor 1 and human epidermal growth receptor 2 (HER2) are overexpressed in certain cancer cells. Antibodies against these receptors (eg. cetuximab and transtuzumab [Herceptin]) have shown therapeutic value in cancer treatment. The existing methods for the quantification of these receptors in tumors involve immunohistochemistry or DNA quantification, both in extracted tissue samples. The goal of the study was to evaluate whether an optical fiber-based technique can be used to quantify the expression of multiple growth factor receptors simultaneously. METHODS: The authors examined HER2 expression using the monoclonal antibody trastuzumab as a targeting ligand to test their system. They conjugated trastuzumab to 2 different Alexa Fluor dyes with different excitation and emission wavelengths. Two of the dye conjugates were subsequently injected intravenously into mice bearing HER2-expressing subcutaneous tumors. An optical fiber was then inserted into the tumor through a 30-gauge needle, and using a single laser beam as the excitation source, the fluorescence emitted by the 2 conjugates was identified and quantified by 2-photon optical fiber fluorescence. RESULTS: The 2 conjugates bound to the HER2-expressing tumor competitively in a receptor-specific fashion, but they failed to bind to a similar cell tumor that did not express HER2. The concentration of the conjugate present in the tumor as determined by 2-photon optical fiber fluorescence was shown to serve as an index of the HER2 expression levels. CONCLUSIONS: These studies offer a minimally invasive technique for the quantification of tumor receptors simultaneously.

Polyvalent dendrimer-methotrexate as a folate receptor-targeted cancer therapeutic.

Our previous studies have demonstrated that a generation 5 dendrimer (G5) conjugated with both folic acid (FA) and methotrexate (MTX) has a higher chemotherapeutic index than MTX alone. Despite this, batch-to-batch inconsistencies in the number of FA and MTX molecules linked to each dendrimer led to conjugate batches with varying biological activity, especially when scaleup synthesis was attempted. Since the MTX is conjugated through an ester linkage, there were concerns that biological inconsistency could also result from serum esterase activity and differential bioavailability of the targeted conjugate. In order to resolve these problems, we undertook a novel approach to synthesize a polyvalent G5-MTX(n) conjugate through click chemistry, attaching the MTX to the dendrimer through an esterase-stable amide linkage. Surface plasmon resonance binding studies show that a G5-MTX(10) conjugate synthesized in this manner binds to the FA receptor (FR) through polyvalent interaction showing 4300-fold higher affinity than free MTX. The conjugate inhibits dihydrofolate reductase, and induces cytotoxicity in FR-expressing KB cells through FR-specific cellular internalization. Thus, the polyvalent MTX on the dendrimer serves the dual role as a targeting molecule as well as a chemotherapeutic drug. The newly synthesized G5-MTX(n) conjugate may serve as a FR-targeted chemotherapeutic with potential for cancer therapy.

Bifunctional PAMAM dendrimer conjugates of folic acid and methotrexate with defined ratio.

Our group previously developed a multifunctional, targeted cancer therapeutic based on Generation 5 (G5) polyamidoamine (PAMAM) dendrimers. In those studies we conjugated the targeting molecule folic acid (FA) and the chemotherapeutic drug methotrexate (MTX) sequentially. This complex macromolecule was shown to selectively bind and kill KB tumor cells that overexpress folate receptor (FR) in vitro and in vivo. However, the multistep conjugation strategy employed in the synthesis of the molecule resulted in heterogeneous populations having differing numbers and ratios of the functionally antagonistic FA and MTX. This led to inconsistent and sometimes biologically inactive batches of molecules, especially during large-scale synthesis. We here resolved this issue by using a novel triazine scaffold approach that reduces the number of dendrimer conjugation steps required and allows for the synthesis of G5 conjugates with defined ratios of FA and MTX. Although an unoccupied γ-glutamyl carboxylate of FA has been previously suggested to be nonessential for FR binding, the functional requirement of an open α-carboxylate still remains unclear. In an attempt to also address this question, we have synthesized isomeric FA dendrimer conjugates (α-carboxyl or γ-carboxyl linked). Competitive binding studies revealed that both linkages have virtually identical affinity toward FR on KB cells. Our studies show that a novel bifunctional triazine-based conjugate G5-Triazine-γMTX-αFA with identical numbers of FA and MTX binds to FR through a polyvalent interaction and induces cytotoxicity in KB cells through FR-mediated cellular internalization, inducing higher toxicity as compared to conjugates synthesized by the multistep strategy. This work serves as a proof of concept for the development of bifunctional dendrimer conjugates that require a defined ratio of two functional molecules.

Photochemical release of methotrexate from folate receptor-targeting PAMAM dendrimer nanoconjugate.

Nanoparticle (NP)-based targeted drug delivery involves cell-specific targeting followed by a subsequent therapeutic action from the therapeutic carried by the NP system. NPs conjugated with methotrexate (MTX), a potent inhibitor of dihydrofolate reductase (DHFR) localized in cytosol, have been under investigation as a delivery system to target cancer cells to enhance the therapeutic index of methotrexate, which is otherwise non-selectively cytotoxic. Despite improved therapeutic activity from MTX-conjugated NPs in vitro and in vivo, the therapeutic action of these conjugates following cellular entry is poorly understood; in particular it is unclear whether the therapeutic activity requires release of the MTX. This study investigates whether MTX must be released from a nanoparticle in order to achieve the therapeutic activity. We report herein light-controlled release of methotrexate from a dendrimer-based conjugate and provide evidence suggesting that MTX still attached to the nanoconjugate system is fully able to inhibit the activity of its enzyme target and the growth of cancer cells.

Folate-targeted nanoparticles show efficacy in the treatment of inflammatory arthritis.

OBJECTIVE: To investigate the uptake of a poly(amidoamine) dendrimer (generation 5 [G5]) nanoparticle covalently conjugated to polyvalent folic acid (FA) as the targeting ligand into macrophages, and to investigate the activity of an FA- and methotrexate (MTX)-conjugated dendrimer (G5-FA-MTX) as a therapeutic for the inflammatory disease of arthritis. METHODS: In vitro studies were performed in macrophage cell lines and in isolated mouse macrophages to check the cellular uptake of fluorescence-tagged G5-FA nanoparticles, using flow cytometry and confocal microscopy. In vivo studies were conducted in a rat model of collagen-induced arthritis to evaluate the therapeutic potential of G5-FA-MTX. RESULTS: Folate-targeted dendrimer bound and internalized in a receptor-specific manner into both folate receptor ß-expressing macrophage cell lines and primary mouse macrophages. The conjugate G5-FA-MTX acted as a potent antiinflammatory agent and reduced arthritis-induced parameters of inflammation such as ankle swelling, paw volume, cartilage damage, bone resorption, and body weight decrease. CONCLUSION: The use of folate-targeted nanoparticles to specifically target MTX into macrophages may provide an effective clinical approach for antiinflammatory therapy in rheumatoid arthritis.

Design, synthesis, and biological functionality of a dendrimer-based modular drug delivery platform.

A modular dendrimer-based drug delivery platform was designed to improve upon existing limitations in single dendrimer systems. Using this modular strategy, a biologically active platform containing receptor mediated targeting and fluorescence imaging modules was synthesized by coupling a folic acid (FA) conjugated dendrimer with a fluorescein isothiocyanate (FITC) conjugated dendrimer. The two different dendrimer modules were coupled via the 1,3-dipolar cycloaddition reaction ("click" chemistry) between an alkyne moiety on the surface of the first dendrimer and an azide moiety on the second dendrimer. Two simplified model systems were also synthesized to develop appropriate "click" reaction conditions and aid in spectroscopic assignments. Conjugates were characterized by (1)H NMR spectroscopy and NOESY. The FA-FITC modular platform was evaluated in vitro with a human epithelial cancer cell line (KB) and found to specifically target the overexpressed folic acid receptor.

Polyvalent saccharide-functionalized generation 3 poly(amidoamine) dendrimer-methotrexate conjugate as a potential anticancer agent.

A saccharide-terminated generation 3 (G3) polyamidoamine (PAMAM) dendrimer was synthesized as a drug carrier. Utilizing this dendritic platform, we have successfully synthesized polyvalent conjugates (G3-MTX) containing the drug methotrexate (MTX). Surface Plasmon Resonance (SPR) results showed that G3-MTX presented three orders of magnitude enhancement in binding avidity to folate-binding protein (FBP) as compared to the free folic acid (FA). Flow cytometric and confocal microscopic analysis showed that conjugate (G3-MTX-FI) containing imaging agent fluorescein-5(6)-carboxamidohexanoic acid (FI) was internalized into folate receptor (FR)-expressing KB cells in dose-dependent and receptor-mediated fashion. The G3-MTX induced a dose-dependent cytotoxicity in the KB cells. Therefore, the polyvalent G3-MTX may have potential as an anticancer nanodevice for the specific targeting and killing of FR-expressing tumor cells.

Association of Variants in TMEM45A With Keratoglobus.

IMPORTANCE: Keratoglobus is a rare corneal disorder characterized by generalized thinning and globular protrusion of the cornea. Affected individuals typically have significantly decreased vision and are at risk of corneal perforation. The genetic basis and inheritance pattern of isolated congenital keratoglobus are currently unknown. OBJECTIVE: To identify the genetic basis of isolated congenital keratoglobus. DESIGN, SETTING, AND PARTICIPANTS: This case series and molecular analysis studied 3 unrelated nonconsanguineous families with keratoglobus at a medical center in Israel. Data were collected from June 2019 to March 2021 and analyzed during the same period. EXPOSURES: Whole-exome sequencing and direct Sanger sequencing, expression analysis by real-time polymerase chain reaction, splice-site variant analysis, immunohistochemical staining, and histological evaluation of a knockout mouse model. MAIN OUTCOMES AND MEASURE: Molecular characteristics associated with keratoglobus. RESULTS: Four pediatric patients (3 male individuals) from 3 families had clinical findings consistent with keratoglobus. These included globular protrusion, corneal thinning more prominent at the periphery, and high astigmatism. Truncating and splice site variants were identified in the TMEM45A gene, which fully segregate with the disorder. All affected individuals were homozygous or compound heterozygous for variants in the TMEM45A gene, while unaffected family members were heterozygous carriers. Expression analysis in healthy controls showed that TMEM45A was expressed 23 times higher in the human cornea compared with peripheral blood. Immunohistochemical staining of the TMEM45A protein in normal corneas confirmed its expression in the corneal stroma and epithelium. A TMEM45A knockout mouse model showed structural features consistent with keratoglobus. CONCLUSIONS AND RELEVANCE: Expression of TMEM45A has been previously shown to result in upregulation of extracellular matrix components and fibrosis. These results suggest that isolated congenital keratoglobus is an autosomal recessively inherited disorder associated with variants in the TMEM45A gene.

Dendrimer-based tumor cell targeting of fibroblast growth factor-1.

Fibroblast Growth Factor Receptor (FGFR) is overexpressed in a wide variety of tumors, and therefore is an attractive target for drug delivery. Recombinant FGF-1 was purified and attached to a fifth-generation (G5) polyamidoamine dendrimer. The specific binding and internalization of this conjugate labeled with FITC was demonstrated by flow cytometry as well as by confocal microscopic analysis in cell lines expressing FGFR. The binding and uptake of FGF-conjugated dendrimers was completely blocked by excess nonconjugated FGF-1. Confocal microscopic analysis showed cytosolic as well as nuclear localization. Multivalent G5-FGF nanoparticles may serve as a platform for cytosolic as well as nuclear drug delivery in tumor cells, and as an FGF delivery agent for angiogenesis and wound healing. Our study shows for the first time the applicability of a dendrimer nanodevice for tumor cell targeting through FGFR.

Design of riboflavin-presenting PAMAM dendrimers as a new nanoplatform for cancer-targeted delivery.

This communication describes the synthesis and in vitro biological evaluation of novel generation 5 PAMAM dendrimers conjugated with riboflavin as a targeting ligand. Cell-based experiments demonstrated that a dendrimer conjugated with riboflavin is able to undergo cellular binding and uptake in KB cells, and when the dendrimer is also conjugated with methotrexate, the riboflavin dendrimer conjugate can potently inhibit cell growth.

Plasma-mediated release of morphine from synthesized prodrugs.

Two morphine prodrugs ('PDA' and 'PDB') were synthesized and the kinetics of esterase-mediated morphine release from these prodrugs were determined when incubated with plasma from different animal species. Morphine was rapidly released from PDA by all species plasma with the maximum reached within 5-10min; the released morphine was biologically active as determined by an in vitro cAMP assay. The morphine was released from PDB at a slower and species-dependent rate (mouse>rat>guinea pig>human). Morphine's release from PDB appeared to be mediated by carboxyl esterases as the release was inhibited by the carboxyl esterase inhibitor benzil. PDA nor PDB induce cytotoxicity in the neuronal cell lines SK-NSH and SH-SY5Y. The carboxyl and amino functional moieties present on the linker portions of PDA and PDB, respectively, may facilitate their conjugation to nanoparticles to tailor morphine pharmacokinetics and specific targeting. These studies suggest the potential clinical utility of these prodrugs for morphine release at desired rates by administration of their mixture at selected ratios.

Cationic poly(amidoamine) dendrimer induces lysosomal apoptotic pathway at therapeutically relevant concentrations.

Poly(amidoamine) (PAMAM) dendrimers carrying different amounts of surface amino groups were synthesized and tested for their effects on cellular cytotoxicity, lysosomal pH, and mitochondria-dependent apoptosis. In KB cells, the PAMAM dendrimers were taken up into the lysosomal compartment, and they increased the lysosomal pH and cytotoxicity as a function of the number of surface amino groups on the dendrimer. PAMAM dendrimers that were surface-neutralized by acetylation of >80% of the surface amino groups failed to show any cytotoxicity. The positively charged, amine-terminated PAMAM dendrimer induced cellular apoptosis, as demonstrated by mitochondrial membrane potential changes and caspase activity measurements. These results suggest that PAMAM dendrimers are endocytosed into the KB cells through a lysosomal pathway, leading to lysosomal alkalinization and induction of mitochondria-mediated apoptosis.

Human plasma-mediated hypoxic activation of indolequinone-based naloxone pro-drugs.

Hypoxia is known to occur in tissues in response to narcotic analgesic therapy using as a result of respiratory depression. The aim of this study was to synthesize a narcotic antagonist pro-drug that can be activated by tissue hypoxia to prevent the damage associated with respiratory depression. We synthesized three different pro-drugs of the narcotic antagonist naloxone utilizing indolequinone as the hypoxia-sensitive moiety. The indolequinone structure in the pro-drugs was designed to have an open reactive point at the N-1 position offering the possibility of further conjugation with macromolecules to modify the bio-availability of these pro-drugs in vivo. A pro-drug (labeled 1) where naloxone and the indolequinone moiety were linked through a carbonate bond was rapidly hydrolyzed in phosphate buffered saline. However, two additional pro-drugs (labeled 2 and 3) having carbamate linkers were stable in phosphate buffered saline for 24h. The reductive release of naloxone from the pro-drugs was achieved in the presence of the bio-reductive enzyme DT-Diaphorase, with about 80% release occurring from the two pro-drugs in 24h. More than 99% of naloxone was released from pro-drug 2 in 30% human plasma, however the release only occurred under hypoxic conditions. This system provides a potential means for feedback control to counter critical respiratory depression induced by narcotic analgesics.

Dendrimer-epidermal growth factor conjugate displays superagonist activity.

Binding of ligands on to epidermal growth factor receptor (EGFR) can stimulate cell growth; therefore, any application employing EGF as a targeting ligand for a "drug carrier" must evaluate the effect of the conjugate on cell growth. We report the synthesis and in vitro biological activity of EGF molecules coupled to a fluorescein-labeled polyamidoamine dendrimer. The conjugate bound and internalized into several EGFR-expressing cell lines in a receptor-specific fashion. The conjugate effectively induced EGFR phosphorylation and acted as a superagonist by stimulating cell growth to a greater degree than free EGF. Concomitant administration of the chemotherapeutic drug methotrexate completely inhibited cell growth to a degree similar to its effect in the absence of the conjugate. Thus, dendrimer-EGF conjugates serve as EGFR superagonists, but this activity can be overcome by chemotherapeutic drugs. The agonist activity of these materials must be taken into consideration when using EGF conjugates for imaging applications.

Investigation of tumor cell targeting of a dendrimer nanoparticle using a double-clad optical fiber probe.

Fluorescence quantification in tissues using conventional techniques can be difficult due to the absorption and scattering of light in tissues. Our previous studies have shown that a single-mode optical fiber (SMF)-based, two-photon optical fiber fluorescence (TPOFF) probe could be effective as a minimally invasive, real-time technique for quantifying fluorescence in solid tumors. We report improved results with this technique using a solid, double-clad optical fiber (DCF). The DCF can maintain a high excitation rate by propagating ultrashort laser pulses down an inner single-mode core, while demonstrating improved collection efficiency by using a high-numerical aperture multimode outer core confined with a second clad. We have compared the TPOFF detection efficiency of the DCF versus the SMF with standard solutions of the generation 5 poly(amidoamine) dendrimer (G5) nanoparticles G5-6TAMRA (G5-6T) and G5-6TAMRA-folic acid (G5-6T-FA). The DCF probe showed three- to five-fold increases in the detection efficiency of these conjugates, in comparison to the SMF. We also demonstrate the applicability of the DCF to quantify the targeted uptake of G5-6T-FA in mouse tumors expressing the FA receptor. These results indicate that the TPOFF technique using the DCF probe is an appropriate tool to quantify low nanomolar concentrations of targeted fluorescent probes from deep tissue.

Synthesis and functional evaluation of DNA-assembled polyamidoamine dendrimer clusters for cancer cell-specific targeting.

We sought to produce dendrimers conjugated to different biofunctional moieties (fluorescein [FITC] and folic acid [FA]), and then link them together using complementary DNA oligonucleotides to produce clustered molecules that target cancer cells that overexpress the high-affinity folate receptor. Amine-terminated, generation 5 polyamidoamine (G5 PAMAM) dendrimers are first partially acetylated and then conjugated with FITC or FA, followed by the covalent attachment of complementary, 5'-phosphate-modified 34-base-long oligonucleotides. Hybridization of these oligonucleotide conjugates led to the self-assembly of the FITC- and FA-conjugated dendrimers. In vitro studies of the DNA-linked dendrimer clusters indicated specific binding to KB cells expressing the folate receptor. Confocal microscopy also showed the internalization of the dendrimer cluster. These results demonstrate the ability to design and produce supramolecular arrays of dendrimers using oligonucleotide bridges. This will also allow for further development of DNA-linked dendrimer clusters as imaging agents and therapeutics.