Improved syntheses and applicability of different DOTA building blocks for multiply derivatized scaffolds

A robust collagen-targeting MRI peptide contrast agent for in vivo imaging of hepatic fibrosis

We herein report the construction of a robust MRI peptide contrast agent Gd-ICTP with superior selectivity for type I collagen, enabling the accurate and non-invasive detection of hepatic fibrosis in vivo.

DOTA-Based Plectin-1 Targeted Contrast Agent Enables Detection of Pancreatic Cancer in Human Tissue

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and lethal malignancy with extremely poor patient survival rates. A key reason for the poor prognosis is the lack of effective diagnostic tools to detect the disease at curable, premetastatic stages. Tumor surgical resection is PDAC's first-line treatment, however distinguishing between cancerous and healthy tissue with current imaging tools remains a challenge. In this work, we report a DOTA-based fluorescent probe targeting plectin-1 for imaging PDAC with high specificity. To enable heterogeneous functionalization of the DOTA-core with multiple targeting peptide units and the fluorophore, a novel, fully clickable synthetic route that proceeds in one pot was developed. Extensive validation of the probe set the stage for PDAC detection in mice and human tissue. Altogether, these findings may pave the way for improved clinical understanding and early detection of PDAC progression as well as more accurate resection criteria.

A robust collagen-targeting MRI peptide contrast agent for in vivo imaging of hepatic fibrosis

We herein report the construction of a robust MRI peptide contrast agent Gd-ICTP with superior selectivity for type I collagen, enabling the accurate and non-invasive detection of hepatic fibrosis in vivo.

Facile transmetallation of [SbIII(DOTA)]- renders it unsuitable for medical applications

The antimony(iii) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) has been prepared and its exceptionally low stability observed. The Sb(iii) ion in Na[Sb(DOTA)]·4H2O shows an approximately square antiprismatic coordination geometry that is close to superimposable to the Bi(iii) geometry in [Bi(DOTA)]- in two phases containing this anion, Na[Bi(DOTA)]·4H2O, [H3O][Bi(DOTA)]·H2O for which structures are also described. Interestingly, DOTA itself in [(H6DOTA)]Cl2·4H2O·DMSO shows the same orientation of the N4O4 metal binding cavity reflecting the limited flexibility of DOTA in an octadentate coordination mode. In 8-coordinate complexes it can however accommodate M(iii) ions with r ion spanning a relatively wide range from 87 pm (Sc(iii)) to 117 pm (Bi(iii)). The larger Bi3+ ion appears to be the best metal-ligand size match since [Bi(DOTA)]- is associated with greater complex stability. In the solution state, [Sb(DOTA)]- is extremely susceptible to transmetallation by trivalent ions (Sc(iii), Y(iii), Bi(iii)) and, significantly, even by biologically important divalent metal ions (Mg(ii), Ca(ii), Zn(ii)). In all cases just one equivalent is enough to displace most of the Sb(iii). [Sb(DOTA)]- is resistant to hydrolysis; however, since biologically more abundant metal ions easily substitute the antimony, DOTA complexes will not be suitable for deployment for the delivery of the, so far unexploited, theranostic isotope pair 119Sb and 117Sb.

Integrin αvβ3 receptor targeting PET/MRI dual-modal imaging probe based on the 64Cu labeled manganese ferrite nanoparticles

With the advent of positron emission tomography/magnetic resonance imaging (PET/MRI) scanner, PET/MRI dual-modal imaging will play more and more important role in the diagnosis of cancers and other diseases. Until now, there is no an approved PET/MRI dual-modal imaging probe. The goal of this work is to design and synthesize potential PET/MRI dual-modal imaging probe based on superparamagnetic manganese ferrite nanoparticles. We have developed superparamagnetic nanoparticles that have uniform size with 5 nm and can be further functionalized through surface coating with dopamine and polyethylene glycol derivatives, which provide functional groups for conjugating tumor-targeting biomolecules and bifunctional chelators. The nanoparticles conjugated with integrin α_vβ₃ over-expressed targeting cyclic arginine-glycine-aspartic acid (RGD)-peptide and labeled with positron radionuclide copper-64 were intravenously injected into glioblastoma xenograft nude mice. In vivo MRI and PET imaging of mice implied that the PET/MRI dual-modal imaging probe can precisely locate the tumor site with α_vβ₃ over expression.

Simultaneous cancer control and diagnosis with magnetic nanohybrid materials

Coated magnetite nanoparticles were linked to (68)Ga complexes used in the positron emission tomography (PET) for a new technical approach to detect cancer tissue with radiopharmaceuticals. By substitution of the Ga isotope with an alpha emitter the same compound could be used for cancer treatment. Furthermore the nanoparticles were connected to pH-sensitive complexes, enabling a pH-controlled assembly/disassembly and therefore the spreading of the particles in the tissue. With this novel method of combining detection and treatment simultaneously, the amount of medical exposure could be minimized for the patient. The results demonstrate that magnetite nanoparticles can effectively be functionalized with PET isotopes and pH sensitive complexes in order to use them as a new type of radiopharmaceuticals.

Quantitative assessment of binding affinities for nanoparticles targeted to vulnerable plaque

Recent successes in targeted immune and cell-based therapies have driven new directions for pharmaceutical research. With the rise of these new therapies there is an unfilled need for companion diagnostics to assess patients' potential for therapeutic response. Targeted nanomaterials have been widely investigated to fill this niche; however, in contrast to small molecule or peptide-based targeted agents, binding affinities are not reported for nanomaterials, and to date there has been no standard, quantitative measure for the interaction of targeted nanoparticle agents with their targets. Without a standard measure, accurate comparisons between systems and optimization of targeting behavior are challenging. Here, we demonstrate a method for quantitative assessment of the binding affinity for targeted nanoparticles to cell surface receptors in living systems and apply it to optimize the development of a novel targeted nanoprobe for imaging vulnerable atherosclerotic plaques. In this work, we developed sulfated dextran-coated iron oxide nanoparticles with specific targeting to macrophages, a cell type whose density strongly correlates with plaque vulnerability. Detailed quantitative, in vitro characterizations of (111)In(3+) radiolabeled probes show high-affinity binding to the macrophage scavenger receptor A (SR-A). Cell uptake studies illustrate that higher surface sulfation levels result in much higher uptake efficiency by macrophages. We use a modified Scatchard analysis to quantitatively describe nanoparticle binding to targeted receptors. This characterization represents a potential new standard metric for targeted nanomaterials.

Comparative Assessment of Complex Stabilities of Radiocopper Chelating Agents by a Combination of Complex Challenge and in vivo Experiments

For (64) Cu radiolabeling of biomolecules to be used as in vivo positron emission tomography (PET) imaging agents, various chelators are commonly applied. It has not yet been determined which of the most potent chelators--NODA-GA ((1,4,7-triazacyclononane-4,7-diyl)diacetic acid-1-glutaric acid), CB-TE2A (2,2'-(1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4,11-diyl)diacetic acid), or CB-TE1A-GA (1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4,11-diyl-8-acetic acid-1-glutaric acid)--forms the most stable complexes resulting in PET images of highest quality. We determined the (64) Cu complex stabilities for these three chelators by a combination of complex challenge and an in vivo approach. For this purpose, bioconjugates of the chelating agents with the gastrin-releasing peptide receptor (GRPR)-affine peptide PESIN and an integrin αv β3 -affine c(RGDfC) tetramer were synthesized and radiolabeled with (64) Cu in excellent yields and specific activities. The (64) Cu-labeled biomolecules were evaluated for their complex stabilities in vitro by conducting a challenge experiment with the respective other chelators as challengers. The in vivo stabilities of the complexes were also determined, showing the highest stability for the (64) Cu-CB-TE1A-GA complex in both experimental setups. Therefore, CB-TE1A-GA is the most appropriate chelating agent for *Cu-labeled radiotracers and in vivo imaging applications.

Synthesis and DNA-Binding Studies of a Dinuclear Gadolinium(III)–Platinum(II) Complex

The synthesis and characterisation of a new dinuclear GdIII–PtII complex (1·PF6) containing a functionalised macrocyclic 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid derivative linked to a PtII-terpy (terpy = 2,2′ : 6′,2″-terpyridine) unit by means of a short thiolato linker are reported. The complex was synthesised in six steps from cyclen by means of a modular synthetic strategy. A preliminary DNA-binding study with calf-thymus DNA (ct-DNA) was performed on 1·PF6 by means of linear dichroism (LD). The observed changes in the DNA LD signal in the presence of the metal complex are fully consistent with an intercalative binding mode. Furthermore, an induced negative LD signal in the ultraviolet absorption region of the complex provides strong evidence of a strong DNA-binding interaction. The in vitro cytotoxicity of 1·PF6 towards a human glioblastoma cell line (T98G) was also determined.

Optimized Solid Phase-Assisted Synthesis of Dendrons Applicable as Scaffolds for Radiolabeled Bioactive Multivalent Compounds Intended for Molecular Imaging

Dendritic structures, being highly homogeneous and symmetric, represent ideal scaffolds for the multimerization of bioactive molecules and thus enable the synthesis of compounds of high valency which are e.g., applicable in radiolabeled form as multivalent radiotracers for in vivo imaging. As the commonly applied solution phase synthesis of dendritic scaffolds is cumbersome and time-consuming, a synthesis strategy was developed that allows for the efficient assembly of acid amide bond-based highly modular dendrons on solid support via standard Fmoc solid phase peptide synthesis protocols. The obtained dendritic structures comprised up to 16 maleimide functionalities and were derivatized on solid support with the chelating agent DOTA. The functionalized dendrons furthermore could be efficiently reacted with structurally variable model thiol-bearing bioactive molecules via click chemistry and finally radiolabeled with ⁶⁸Ga. Thus, this solid phase-assisted dendron synthesis approach enables the fast and straightforward assembly of bioactive multivalent constructs for example applicable as radiotracers for in vivo imaging with Positron Emission Tomography (PET).

Non-covalent self assembly controls the relaxivity of magnetically active guests

The relaxivity of a magnetically responsive Gd complex can be controlled by non-covalent molecular recognition with a water-soluble deep cavitand. Lowered relaxivity is conferred by a self-assembled micellar "off state", and the contrast can be regenerated by addition of a superior guest.

IMPROVED SYNTHESIS OF 10-(2-ALKYLAMINO-2-OXOETHYL)-1,4,7,10-TETRAAZACYCLODODECANE-1,4,7-TRIACETIC ACID DERIVATIVES BEARING ACID-SENSITIVE LINKERS

Alkylation of the hydrobromide salts of 1,4,7-tris(methoxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane and 1,4,7-tris(ethoxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane with appropriate α-bromoacetamides, followed by hydrolysis, provides convenient access to 10-(2-alkylamino-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid derivatives that contain acid-sensitive functional groups. The utility of the method is demonstrated by improved syntheses of two known DOTA monoamides bearing acid-sensitive ω-tritylthio alkyl chains in much higher yields based on cyclen as the starting material.

Synthesis of a versatile building block combining cyclen-derivative DO3A with a polyamine via a rigid spacer

The five-step synthesis of a polydentate building block combining a cyclen-based macrocycle (DO3A) with N-(2-aminoethyl)propane-1,3-diamine, which are linked through the xylylen moiety as a rigid C-spacer is described. These two molecular parts were coupled by subsequent bromine atom substitution in 1,4-bis(bromomethyl)benzene. First, N-(2-aminoethyl)propane-1,3-diamine was protected by phthaloyl moieties and then it was reacted with 1,4-bis(bromomethyl)benzene to form (2-phthalimidoethyl)(3-phthalimido-prop-1-yl)(4-bromomethylbenzyl)amine (2). This compound underwent a substitution reaction with DO3A in the form of its tert-butyl esters leading to the intermediate 1-{4-[(2-phthalimidoethyl)(3-phthalimidoprop-1-yl)aminomethyl]phenylmethyl}-4,7,10-tris(t-butoxy-carbonylmethyl)-1,4,7,10-tetraazacyclododecane (3). The phthaloyl as well as the t-butyl protecting groups were removed in the next two reaction steps to form the final product 1-{4-[(2-aminoethyl)(3-aminoprop-1-yl)aminomethyl]phenylmethyl}-4,7,10-tris(carboxy-methyl)-1,4,7,10-tetraazacyclododecane (5). The intermediates 1–4 as well as the final product 5 were characterized by elemental analysis, mass spectrometry, and multinuclear (¹H and ¹³C) and two-dimensional NMR spectroscopy. The final product 5 could serve as a potential building block in subsequent syntheses of binuclear complexes of lanthanides and/or transition metals.

Influence of conjugation chemistry and B epitope orientation on the immune response of branched peptide antigens

Multimeric presentation, a well-proven way of enhancing peptide immunogenicity, has found substantial application in synthetic vaccine design. We have reported that a combination of four copies of a B-cell epitope with one of a T-cell epitope in a single branched construct results in a peptide vaccine conferring total protection against foot-and-mouth disease virus in swine, a natural host (Cubillos et al. (2008) J. Virol. 82, 7223-7230). More recently, a downsized version of this prototype with only two copies of the B epitope has proven as effective as the tetravalent one in mice. Here we evaluate three approaches to bivalent platforms of this latter type, involving different chemistries for the conjugation of two B epitope peptides to a branching T epitope. Comparison of classical thioether, "reverse" thioether (Monsó et al. (2012) Org. Biomol. Chem. 10, 3116-3121) and thiol-ene conjugation chemistries in terms of synthetic efficiency clearly singles out the latter, maleimide-based strategy as most advantageous. We also examine how minor structural differences among the conjugates--including the N- or C-terminal attachment of the B epitope to the branching T epitope--bear on the immunogenicity of these vaccine candidates, with the maleimide-based conjugate again emerging as the most successful.

Incorporation of paramagnetic, fluorescent and PET/SPECT contrast agents into liposomes for multimodal imaging

A series of metal-chelating lipid conjugates has been designed and synthesized. Each member of the series bears a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) macrocycle attached to the lipid head group, using short n-ethylene glycol (n-EG) spacers of varying length. Liposomes incorporating these lipids, chelated to Gd(3+), (64)Cu(2+), or (111)In(3+), and also incorporating fluorescent lipids, have been prepared, and their application in optical, magnetic resonance (MR) and single-photon emission tomography (SPECT) imaging of cellular uptake and distribution investigated in vitro and in vivo. We have shown that these multimodal liposomes can be used as functional MR contrast agents as well as radionuclide tracers for SPECT, and that they can be optimized for each application. When shielded liposomes were formulated incorporating 50% of a lipid with a short n-EG spacer, to give nanoparticles with a shallow but even coverage of n-EG, they showed good cellular internalization in a range of tumour cells, compared to the limited cellular uptake of conventional shielded liposomes formulated with 7% 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[carboxy(polyethyleneglycol)(2000)] (DSPE-PEG2000). Moreover, by matching the depth of n-EG coverage to the length of the n-EG spacers of the DOTA lipids, we have shown that similar distributions and blood half lives to DSPE-PEG2000-stabilized liposomes can be achieved. The ability to tune the imaging properties and distribution of these liposomes allows for the future development of a flexible tri-modal imaging agent.

(111)In- and (203)Pb-Labeled Cyclic RGD Peptide Conjugate as an α(v)β(3) Integrin-Binding Radiotracer

Methodology for site-specific modification and chelate conjugation of a cyclic RGD (cRGD) peptide for the preparation of a radiotracer molecular imaging agent suitable for detecting α(v)β(3) integrin is described. The method involves functionalizing the peptide with an aldehyde moiety and conjugation to a 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid (DOTA) derivative that possesses an aldehyde reactive aminooxy group. The binding assay of the (111)In-labeled peptide conjugate with α(v)β(3) integrin showed 60% bound when four equivalents of the integrin was added, a reasonable binding affinity for a mono-valent modified RGD peptide.

Synthesis and in vitro evaluation of 68Ga-DOTA-4-FBn-TN14003, a novel tracer for the imaging of CXCR4 expression

The expression of the chemokine receptor CXCR4 in tumors is associated with tumor aggressiveness and poor prognosis for the patient and contributes to metastatic seeding. Therefore it is of high interest to find a specific PET tracer for the imaging of CXCR4 expression in tumors. The aim of this study was the synthesis, (68)Ga labeling and first evaluation of DOTA-4-FBn-TN14003 as a potential PET tracer for this purpose. DOTA-4-FBn-TN14003 was synthesized using solid phase peptide synthesis and radiolabeling of this versatile precursor was performed with (68)Ga, which was obtained from a (68)Ge/(68)Ga generator. (68)Ga-DOTA-4-FBn-TN14003 was reproducibly obtained in isolated radiochemical yields of 72.5±4.9% with an excellent radiochemical purity of >99.5%. Specific activities of up to 29.8±3.1 GBq/μmol were achieved. In competition binding assays with SDF-1α, human T cell lymphoma Jurkat cells expressed high levels of CXCR4 whereas human breast cancer MDA-MB-231 cells expressed significantly lower levels of this chemokine receptor. The inhibition constants (IC(50)) of Ga-DOTA-4-FBn-TN14003 and 4-FBn-TN14003 to CXCR4 were determined in a competition assay against (125)I-SDF-1α using Jurkat as well as MDA-MB-231 cells. The IC(50) values of Ga-DOTA-4-FBn-TN14003 (1.99±0.31 nM) and 4-FBn-TN14003 (4.07±1.00 nM) proved to be comparable, indicating negligible influence of the metal complex. These results suggest (68)Ga-DOTA-4-FBn-TN14003 as a promising agent for the imaging of CXCR4 expression in tumors and metastases.

Strategies for the preparation of bifunctional gadolinium(III) chelators

The development of gadolinium chelators that can be easily and readily linked to various substrates is of primary importance for the development high relaxation efficiency and/or targeted magnetic resonance imaging (MRI) contrast agents. Over the last 25 years a large number of bifunctional chelators have been prepared. For the most part, these compounds are based on ligands that are already used in clinically approved contrast agents. More recently, new bifunctional chelators have been reported based on complexes that show a more potent relaxation effect, faster complexation kinetics and in some cases simpler synthetic procedures. This review provides an overview of the synthetic strategies used for the preparation of bifunctional chelators for MRI applications.

LDL-based nanoparticles for contrast enhanced MRI of atheroplaques in mouse models

A LDL particle functionalized with a GdDO3A-monoamide chelate with a long alkenyl anchor (GdDO3A-OA) was prepared for in vivo detection of atheroplaques. The GdDO3A-OA, when successfully intercalated into the lipid layer of LDL particles, led to a significant enhancement of magnetic resonance imaging signal intensity of atheroplaques in atherosclerosis mouse models.

Nanomaterials: applications in cancer imaging and therapy

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics that are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multimodal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge, physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and to achieve active targeting. This is stimulating the development of a diverse range of nanometer-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

Multimerization of cRGD peptides by click chemistry: synthetic strategies, chemical limitations, and influence on biological properties

Integrin α(ν)β(3) is overexpressed on endothelial cells of growing vessels as well as on several tumor types, and so integrin-binding radiolabeled cyclic RGD pentapeptides have attracted increasing interest for in vivo imaging of α(ν)β(3) integrin expression by positron emission tomography (PET). Of the cRGD derivatives available for imaging applications, systems comprising multiple cRGD moieties have recently been shown to exhibit highly favorable properties in relation to monomers. To assess the synthetic limits of the cRGD-multimerization approach and thus the maximum multimer size achievable by using different efficient conjugation reactions, we prepared a variety of multimers that were further investigated in vitro with regard to their avidities to integrin α(ν)β(3.) The synthesized peptide multimers containing increasing numbers of cRGD moieties on PAMAM dendrimer scaffolds were prepared by different click chemistry coupling strategies. A cRGD hexadecimer was the largest construct that could be synthesized under optimized reaction conditions, thus identifying the current synthetic limitations for cRGD multimerization. The obtained multimeric systems were conjugated to a new DOTA-based chelator developed for the derivatization of sterically demanding structures and successfully labeled with (68)Ga for a potential in vivo application. The evaluated multimers showed very high avidities-increasing with the number of cRGD moieties-in in vitro studies on immobilized α(ν)β(3) integrin and U87MG cells, of up to 131- and 124-fold, respectively, relative to the underivatized monomer.

PET Imaging and Biodistribution of Silicon Quantum Dots in Mice

Investigation of nanomaterial disposition and fate in the body is critical before such material can be translated into clinical application. Herein a new macrocyclic ligand-(64)Cu(2+) complex was synthesized and used to label dextran-coated silicon quantum dots (QD), with an average hydrodynamic diameter of 15.1 ± 7.6 nm. The chelate showed exceptional stability, demonstrated by no loss radiolabel under a ligand competition reaction with EDTA. The QDs' biodistribution in mice was quantitatively evaluated by in vivo positron emission tomography (PET) imaging and ex vivo gamma counting. Results showed that they were excreted via renal filtration shortly postinjection and also accumulated in the liver.

DOTA derivatives for site-specific biomolecule-modification via click chemistry: synthesis and comparison of reaction characteristics

Due to the high stability of its complexes with many M(2+) and M(3+)-ions, DOTA (1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid) is the most commonly used chelator for the derivatization and radiolabeling of bioactive molecules. Most of the currently used DOTA derivatives comprise amine-reactive functionalities, limiting their application to the derivatization of fully protected molecules or otherwise resulting in randomly distributed conjugation sites of undefined number. Click chemistry reactions are a valuable alternative to this unspecific conjugation as they proceed efficiently and chemoselectively under mild conditions allowing a site-specific derivatization of unprotected biomolecules. In this work, we describe straightforward syntheses of DOTA derivatives containing thiol, maleimide, aminooxy, aldehyde, alkyne, and azide functionalities, amenable to the currently most often used click chemistry reactions. Furthermore, the efficiency of the respective click reactions introducing DOTA into bioactive molecules was investigated. For each of the synthesized DOTA synthons, the site-specific and efficient conjugation to Tyr(3)-octreotate could be shown. Among these, the addition and oxime formation reactions proceeded fast and without side reactions, giving the products in high yields of 64-83% after purification. The copper-catalyzed triazole formation reactions produced some side-products, giving the desired products in lower, but still reasonable overall yields of 19-25%. All synthesized peptide-DOTA-conjugates were labeled with (68)Ga in high radiochemical yields of 96-99% and high specific activities providing compounds of high purity, demonstrating the applicability of all synthons for biomolecule modification and subsequent radiolabeling.

Mimicking PAMAM Dendrimers with Ampholytic, Hybrid Triazine Dendrimers: A Comparison of Dispersity and Stability

Two strategies are applied to mimic the ampholytic nature of the surfaces of half-generation PAMAM dendrimers and yet retain the very narrow dispersity inherent of triazine dendrimers. Both strategies start with a monodisperse, single-chemical entity, generation two triazine dendrimer presenting twelve surface amines that is available at the kilogram scale. The first method relies on reaction with methyl bromoacetate. Complete conversion of the surface primary amines to tertiary amines occurs to provide 24 surface esters. Extended reaction times lead to quarternization of the amines while other unidentified species are also present. The resulting polyester can be quantitatively hydrolyzed using 4M aqueous HCl to yield a dendrimer with 12 tertiary amines and 24 carboxylic acids about a hydrophobic triazine core. The second method utilizes Michael additions of methyl acrylate to yield 24 surface esters. This reaction proceeds more rapidly and more cleanly than the former strategy. Hydrolysis of this material proceeds quantitatively using 4M aqueous HCl to yield desired dendrimer. In both cases, MALDI-TOF mass spectrometry provides compelling evidence of reaction progress. Electrophoretic analysis confirms the ampholytic nature of these materials with the former targets having a pI value in the 1.8 < pI < 3.4 range, and the latter having a pI value in the 4.7 < pI < 5.9. These ranges bookend the pH range within which PAMAM dendrimers become zwitterionic, 3.4 < pI < 4.7. The strategy of using monodisperse amine-terminated dendrimer constructs as core offers significant advantage over PAMAM homopolymers including dispersity, ease of characterization and batch-to-batch reproducibility. These triazine dendrimers could ultimately be adopted into materials with applications wherein the demands of purity have hitherto remained unsatisfied.