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DNA-based vaccines hold promise to outperform conventional antigen-based vaccines by virtue of many unique features. However, DNA vaccines have thus far fallen short of expectations, due in part to poor targeting of professional antigen-presenting cells (APC) and low immunogenicity. In this study, we describe a new platform for effective and selective delivery of DNA to APCs in vivo that offers intrinsic immune-enhancing characteristics. This platform is based on conjugation of fifth generation polyamidoamine (G5-PAMAM) dendrimers, a DNA-loading surface, with MHC class II–targeting peptides that can selectively deliver these dendrimers to APCs under conditions that enhance their immune stimulatory potency. DNA conjugated with this platform efficiently transfected murine and human APCs in vitro. Subcutaneous administration of DNA-peptide-dendrimer complexes in vivo preferentially transfected dendritic cells (DC) in the draining lymph nodes, promoted generation of high affinity T cells, and elicited rejection of established tumors. Taken together, our findings show how PAMAM dendrimer complexes can be used for high transfection efficiency and effective targeting of APCs in vivo, conferring properties essential to generate effective DNA vaccines. Cancer Res; 71(24); 7452–62. ©2011 AACR.

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Although bioluminescent molecular beacons designed around resonance quenchers have shown higher signal-to-noise ratios and increased sensitivity compared with fluorescent beacon systems, bioluminescence quenching is still comparatively inefficient. A more elegant solution to inefficient quenching can be realized by designing a competitive inhibitor that is structurally very similar to the native substrate, resulting in essentially complete substrate exclusion. In this work, we designed a conjugated anti-interferon-γ (IFN-γ) molecular aptamer beacon (MAB) attached to a bioluminescent protein, Gaussia luciferase (GLuc), and an inhibitor molecule with a similar structure to the native substrate coelenterazine. To prove that a MAB can be more sensitive and have a better signal-to-noise ratio, a bioluminescence-based assay was developed against IFN-γ and provided an optimized, physiologically relevant detection limit of 1.0 nM. We believe that this inhibitor approach may provide a simple alternative strategy to standard resonance quenching in the development of high-performance molecular beacon-based biosensing systems.

Four bidentate, dicationic ligands (L12+-L42+) were prepared and investigated as guests for binding by the cucurbit[7]uril (CB[7]) host and structural components for metal (Pd and Pt)-coordinated self-assembly into metallacycles. In aqueous solutions, all the ligands were found to form stable complexes of variable stoichiometries with CB[7], and only one (L22+) failed to self-assemble, induced by the presence of suitable Pd or Pt complexes, into metallacycles. Exposure of the Pd-based metallacycles to CB[7] led to their disassembly at room temperature, while the Pt-based metallacycles remained stable under these conditions. However, heating of the Pt metallacycles in the presence of CB[7] also led to their disassembly. This interplay between the interactions in aqueous media of the L12+, L32+, and L42+ ligands with the CB[7] host and Pd (or Pt) complexes suggests the possibility of using these or related systems for controlled drug delivery applications.

Partial oxidation of the pillar[5]arene macrocycle with Fe(III) leads to the isolation of a fibrous purple solid with high porosity. Experimental and computational data indicate that the solid material is primarily composed of macrocycles in which two of the hydroquinone units have been oxidized to benzoquinone units. Self-assembly takes place through the formation of multiple quinhydrone charge-transfer complexes between hydroquinone and benzoquinone units on adjacent macrocycles, providing a rare example of self-assembly based on a pentagonal molecular symmetry.

A series of bis(pyridinium)-xylylene derivatives bearing carboxylate terminal groups were investigated as guests for the cucurbit[7]uril host in aqueous solution. While the presence of the terminal carboxylates has a modest effect on the thermodynamic stability of the complexes, the kinetics of complex association/dissociation is strongly affected. The relative position ( meta, para) of the carboxylate group in relation to the pyridinium nitrogen also exerts a considerable effect on the binding kinetics.

While oxidized pillar[5]arenes with 1-5 benzoquinone units are known, very few examples of oxidized pillar[6]arenes have been reported. We describe here the synthesis, characterization and electrochemical behavior of a series of macrocyclic hosts prepared by the stepwise oxidation of 1,4-diethoxypillar[6]arene, resulting in high-yield and high-purity isolation of two constitutional isomers for each macrocycle, in which two, three or four 1,4-diethoxybenzene units are replaced by benzoquinone residues. A careful structural comparison with their counterparts in the pillar[5]arene framework indicates that the geometries of the macrocycles are better described as non-Euclidean hyperbolic hexagons and elliptic pentagons, respectively. A comprehensive computational study to determine anisotropic induced current density (ACID) allows us to visualize and quantify through-space and through-bond communication pathways along the macrocyclic belt. Experimental and simulated voltammetric data, as well as UV-vis spectra, of the new macrocycles afford insights into the various electronic communication pathways in these compounds. Partially oxidised pillar[n]arenes exhibit interesting redox behaviour, but the pillar[6]arenes are poorly characterised in this context. Here stepwise oxidation of 1,4-diethoxypillar[6]arene allows detailed study of the structural and electrochemical properties of molecules with 2, 3, and 4 oxidised units.

The host-guest binding interactions between a series of zwitterionic, symmetric viologens, and the cucurbit[7]uril host were investigated using NMR and UV-vis spectroscopic techniques. The nature of the viologen side arms had strong effects on the kinetics of association and dissociation and weaker, more uniform influence on the thermodynamic stability of the final 1:1 inclusion complexes, which can also be characterized as pseudorotaxanes.

We present a simple, direct method to prepare monohydroxylated cucurbit[7]uril (CB7-OH) through the direct oxidation of its precursor host, cucurbit[7]uril (CB7). Although the conversion takes place in low yield (14%), the isolation of CB7-OH from the reaction mixture is straightforward, and the unreacted CB7 can be easily recovered. ITC measurements with several selected guests confirmed that CB7-OH binds all of them in aqueous solution with similar, albeit slightly lower, binding affinities than those observed with the unmodified CB7 host. ESI mass spectrometric competition experiments are consistent with the ITC measurements. A variety of spectroscopic and voltammetric measurements also verify that the CB7-OH complexes exhibit properties essentially identical to those of the CB7 complexes. DFT computational data also confirm the similar thermodynamic stabilities and structures of the CB7-OH and CB7 inclusion complexes. Finally, the high thermodynamic stability of the CB7-OH complexes was used to improve on the extraction efficiency of stir bar sorptive extraction methods after suitable modification of the active coating with CB7-OH.

In aqueous media the host cucurbit[7]uril (CB7) forms inclusion complexes of high thermodynamic stability with ferrocenyl-containing guests. These complexes are characterized by the inclusion of the ferrocenyl group inside the CB7 cavity, primarily driven by hydrophobic forces. This mini-review provides a summary of the properties of these inclusion complexes, with emphasis on their electrochemical properties and, particularly, on the CB7-induced shift in the half-wave potential for one-electron oxidation of the ferrocenyl residues.

Bambusurils are a family of receptor molecules related to the cucurbit[n]urils and appreciated for their high affinities to inorganic anions. Here we show that a bambusuril macrocycle bearing carboxylate functional groups on its portals can form external complexes with bipyridinium cationic guests in aqueous solution. The apparent binding affinities of the complex can be modulated by the addition of potassium cations, which compete with the guests for the carboxylate portals of the macrocycle. We further illustrate that the binding mode of these host-guest systems varies depending on the choice of bipyridinium guests.

The electrochemical reduction of five partially oxidized pillar[5]arenes containing variable numbers (1-5) of quinone units was investigated in acetonitrile and dichloromethane solutions. The cathodic voltammetric behavior of all the macrocyclic compounds containing two or more quinone units indicates the existence of detectable levels of electronic communication between them. We have also investigated these compounds and their reduced forms using DFT computations. Our computational results indicate the presence of through-space communication between quinone units.

This chapter focuses on non-covalent complexes formed by cucurbituril hosts with redox active guests, defined as molecules containing a residue capable of reversible electron transfer at accessible potentials. Primarily, we will be concerned with cobaltocenium, ferrocene and viologen derivatives as guests, and cucurbit[7]uril (CB[7]) and cucurbit[8]uril (CB[8]) as the hosts. In general terms, all the resulting complexes are quite stable, with binding affinities from micromolar to femtomolar levels. The elevated thermodynamic stability of these complexes makes it hard to develop redox switchable supramolecular systems based on these complexation phenomena, but we have designed and characterized several systems in which effective redox switching is possible, either on its own or coupled to proton transfer. Considerable attention will be paid to the complexation-induced changes in electrochemical potentials and kinetics in these supramolecular systems.

This chapter focuses on the proficiency of cucurbit[7]uril and cucurbit[8]uril (CB[7,8]) as appropriate hosts for the complexation of aromatic stimuli-responsive guests, which translates into a wide variety of switchable assemblies. These CB[7,8]-based responsive aggregates will be analysed throughout the text both on the basis of the source of external stimulation, as well as the type of structural modification produced on the complex. Hence, whilst the structural features of CB[7] would serve as a starting point for the discussion of binary host–guest switches, the ability of CB[8] to complex two identical or complementary guests would allow us to study more intricate CB[8]-based homo- and heteroternary stimuli-responsive assemblies. Great attention has been paid not only to the analysis of simplified models, but also to the implementation of these into functional chemical systems.

This chapter summarizes research work showing that electrostatic interactions may have considerable effects on the stability of complexes formed by the cucurbit[n]uril hosts. Focusing primarily on work carried out by the author's research group with the cucurbit[7]uril (CB[7]) molecular receptor, this review highlights the role played by electrostatic interactions involving the host cavity portals, in which considerable negative charge density accumulates due to the carbonyl oxygens lacing the portal rims. Electrostatics are responsible for diminished binding affinities between CB[7] and a number of anionic guests containing one or more carboxylate groups. These electrostatic interactions can be used effectively to control the average location of CB[7] along axle-type guests having terminal –COOH groups as a function of their state of protonation, leading to switchable pseudorotaxane systems. They can also be utilized to advantage to develop favorable lateral interactions between CB[7] and other molecular receptors, which results in systems showing cooperative self-assembly.

The ability of diferrocenylsilanediol, Fc2Si(OH)2 (5), and 1,1,3,3-tetraferrocenyldisiloxane-1,3-diol, Fc2(HO)Si–O–Si(OH)Fc2 (6), to act as new electroactive anion receptors for either acetate or chloride anions has been investigated in solution, in the solid state, and in the gas phase. 1H NMR spectroscopic titrations with anions reveal that the binding interaction causes chemical-shift perturbations not only in the Si–OH hydrogen-bonding donor motif but also in the ferrocenyl protons of receptors 5 and 6. Square-wave voltammetric studies evidence that multiferrocenyl silanols 5 and 6 exhibit higher ability for electrochemical sensing of acetate than chloride, since the corresponding half-wave potentials (E1/2) for the successive ferrocene oxidations display a higher cathodic shift in the presence of such an anion. Furthermore, single-crystal X-ray diffraction analyses of the tetrabutylammonium salts of complexes [Fc2Si(OH)2·CH3COO]− (8), [Fc2Si(OH)2·Cl]− (9), [Fc2(HO)Si–O–Si(OH)Fc2·CH3COO]− (10), [{Fc2(...

The use of cucurbit[8]uril as a molecular host has emerged in the chemical literature as a reliable strategy for the creation of dynamic chemical systems, owing to its ability to form homo- and heteroternary complexes in aqueous media with appropriate molecular switches as guests. In this manner, CB[8]-based supramolecular switches can be designed in a predictable and modular fashion, through the selection of appropriate guests able to condition the redox, photochemical, or pH-triggered behavior of tailored multicomponent systems. Furthermore, CB[8] allows the implementation of dual/triple and linear/orthogonal stimuli-dependent properties into these molecular devices by a careful selection of the guests. This versatility in their design gives these supramolecular switches great potential for the rational development of new materials, in which their function is not only determined by the custom-made stimuli-responsiveness, but also by the transient aggregation/disaggregation of homo- or heteromeric building blocks.

The binding interactions between the cyclohexanocucurbit[6]uril (Cy6CB6) host and a series of dialkyl-4,4'-bipyridinium (viologen) dicationic guests were investigated in the solution phase, using (1)H NMR spectroscopy, and in the solid phase, using X-ray diffraction methods. In D2O solution, methyl viologen (MV(2+)) and ethyl viologen (EV(2+)) form 1:1 complexes in which the bipyridinium aromatic nucleus is partially included inside the Cy6CB6 cavity. Propyl viologen (PV(2+)), butyl viologen (BV(2+)), pentyl viologen (FV(2+)), and heptyl viologen (HV(2+)) form 2:1 complexes with Cy6CB6, in which each of the viologen aliphatic chains is included by a host molecule. In the solid state, EV(2+) forms a polypseudorotaxane via pseudorotaxane interdigitation of Cy6CB6 hosts. The PV(2+) guest forms a dumbbell-shaped structure with a Cy6CB6 host residing over each of the terminal propyl groups of the guest. In contrast to this, the BV(2+) guest and Cy6CB6 form a different polypseudorotaxane structure in which dumbbell-shaped structures, formed by two host molecules interacting with a single guest, are interconnected through metal-host coordination.

The cathodic voltammetric behavior of pillar[5]quinone was investigated in dichloromethane solution. Our data show that the symmetry of the macrocycle has a pronounced effect on the electron uptake sequence. The uptake of the first five electrons follows a 2-1-2 pattern, and only a total of eight electrons could be injected into the macrocycle under our experimental conditions.

Bioorthogonal conjugation eliminates the short-comings of classical conjugation methods. The conjugation of antibodies to reporter proteins, such as bioluminescent protein, can be controlled with orthogonal conjugation methods. Here we report a bioluminescent immunoassay for the sensitive detection of interferon-γ (IFN-γ) that utilizes orthogonal conjugation of bioluminescent protein, Gaussia luciferase to anti-IFN-γ antibody. The IFN-γ is produced by the immune system and the detection of the IFN-γ is pivotal for the detection of persistent viral and bacterial infections. A bioorthogonal conjugation approach is used to conjugate an anti-IFN-γ antibody with a GLuc mutant containing the N-terminal tyrosine using formylbenzene diazonium hexafluorophosphate reagent (FBDP) in hydrophilic mild pH environment yielding high conjugation efficiency (60%). This reagent is shown to be specific for tyrosine (Tyr) residues. Therefore, conjugation through Tyr was orthogonal and not detrimental to the bioluminescence activity of GLuc. The immunoassay described in this paper is a sandwich type assay and involves a capture and a detection antibody. The assay was validated for its robustness, precision, accuracy, limit of detection, and recovery.

Myeloid cells play a key role in tumor progression and metastasis by providing nourishment and immune protection, as well as facilitating cancer invasion and seeding to distal sites. Although advances have been made in understanding the biology of these tumor-educated myeloid cells (TEMCs), their intrinsic plasticity challenges our further understanding of their biology. Indeed, in vitro experiments only mimic the in vivo setting, and current gene-knockout technologies do not allow the simultaneous, temporally controlled, and cell-specific silencing of multiple genes or pathways. In this article, we describe the 4PD nanoplatform, which allows the in vivo preferential transfection and in vivo tracking of TEMCs with the desired RNAs. This platform is based on the conjugation of CD124/IL-4Rα–targeting peptide with G5 PAMAM dendrimers as the loading surface and can convey therapeutic or experimental RNAs of interest. When injected i.v. in mice bearing CT26 colon carcinoma or B16 melanoma, the 4PD nanoparticles predominantly accumulate at the tumor site, transfecting intratumoral myeloid cells. The use of 4PD to deliver a combination of STAT3- and C/EBPβ-specific short hairpin RNA or miR-142-3p confirmed the importance of these genes and microRNAs in TEMC biology and indicates that silencing of both genes is necessary to increase the efficacy of immune interventions. Thus, the 4PD nanoparticle can rapidly and cost effectively modulate and assess the in vivo function of microRNAs and mRNAs in TEMCs.

The cucurbit[7]uril (CB7) host forms rotaxane-type complexes with dumbbell-shaped, cationic guests bis(3,5-dimethoxybenzyl)-4,4'-bipyridinium (1(2+)) and bis(3,5-diethoxybenzyl)-4,4'-bipyridinium (2(2+)). The kinetics of complex formation is slower with the latter guest because of its bulkier end groups. Rotaxane formation was found to be thermodynamically more favorable and kinetically faster in D2O than in DMSO-d6 solution, which highlights the importance of hydrophobic interactions in the assembly of cucurbituril complexes.

This work focuses on the effect of cucurbit[n]uril (CBn) hosts on the microenvironment of molecular subunits that are located adjacent to the CBn binding site in inclusion complexes. The set of data presented here includes previously reported electrochemical and electron paramagnetic resonance spectroscopic data, primarily obtained with ferrocene-containing guests, as well as new electrochemical data recorded with 4,4′-bipyridinium (viologen) derivatives. Most of the data were obtained with cucurbit[7]uril (CB7) complexes, and the rest were collected with cucurbit[8]uril (CB8) complexes. The experimental data compiled here clearly suggest that the microenvironment adjacent to the CBn portals in the complexes exhibits increased polarity compared with the bulk aqueous solution.

CONSPECTUS: The cucurbit[n]uril (CBn) host family consists of a group of rigid macrocyclic hosts with barrel-like shapes and limited solubility in aqueous media. These hosts are capable of reaching high binding affinities with positively charged hydrophobic guests. In optimum cases, equilibrium association constant (K) values as high as 10(17) M(-1) have been reported, exceeding the binding affinity of the avidin-biotin host-guest pair. The synthetic CBn receptors have shattered the notion that highly stable noncovalent complexes can form only when one of the partners is a molecule of biological origin. The work described in this Account is concerned with the development of methods geared toward the reversible modulation of the binding affinity of CBn inclusion complexes under mild conditions. A good fraction of the research work has dealt with redox active guests, such as 4,4'-bipyridinium (viologen), ferrocene, and cobaltocenium derivatives. Our experimental results show that the thermodynamics and kinetics of the electron transfer reactions of these compounds can be substantially altered by complexation with CBn hosts, and therefore, electron transfer reactions can be used to exert a measure of control on the overall binding affinity of the CBn complexes. We have also developed systems in which proton transfer reactions have a strong effect on the binding affinity. With more structurally elaborate guests containing more than one adjacent binding sites, proton transfer reactions may affect the average location of the CBn host within the complexes. A series of guest compounds containing paramagnetic 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) residues also exhibit interesting binding properties with CB7 and CB8. The latter host forms a very stable host-guest pair with TEMPO subunits, in which the nitroxide group resides inside the host cavity. Finally, with suitable ditopic guests, we have detected distinct microscopic complexes using experimental techniques with relatively slow time scales, such as NMR spectroscopy. These unusual findings are the result of the considerable thermodynamic and kinetic stability of CBn inclusion complexes.

The binding interactions between a novel ferrocenylguanidinium derivative (FcG+) and the macrocyclic hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated in aqueous solution. 1H NMR spectroscopic experiments indicated that both hosts form stable 1:1 inclusion complexes with FcG+, in which the ferrocenyl group is engulfed by the host cavity. The stoichiometry of the CB7·FcG+ complex was also confirmed by electrospray mass spectrometric (ESI MS) experiments. The association equilibrium constants (K) were determined from NMR competition experiments. The measured K values were 3.5 × 109 and 2.5 × 108 M–1 for CB7 and CB8, respectively, in 50 mM sodium acetate-d3 D2O solution (pD 4.7). DFT computational studies confirmed the 1:1 stoichiometry and the inclusion character of both complexes. Voltammetric experiments were carried out to measure the complexation-induced shifts on the half-wave potentials for the one-electron oxidation of the ferrocenyl moiety. Complexation by CB7 led to a 12 mV an...

The binding interactions between two cucurbit[n]uril hosts (n = 7, 8, CB7 and CB8) and the three new guests 1,1′-bis(cyclohexylammoniomethyl)ferrocene (1H22+), 1,1′-bis(cyclohexylmethylammoniomethyl)ferrocene (2H22+), and 1,1′-bis(cyclohexyldimethylammoniomethyl)ferrocene (32+) were investigated in aqueous solution using 1H NMR spectroscopy, voltammetry, and electrospray (ESI) mass spectrometry. The experimental data reveal that guests 1H22+ and 2H22+ behave similarly with both hosts, leading to the formation of pseudorotaxane complexes in which the host is located centrally around the ferrocenyl residue. A similar complex forms also between 32+ and CB7, but its formation is slower (k = 2.5 × 10–4 s–1) and can be monitored by NMR spectroscopy. Finally, 32+ and CB8 give rise to a ternary 2:1 complex, in which CB8 receptors are bound to the terminal cyclohexyl groups, when the concentration of the host exceeds that of the guest.

We prepared a new series of bisaminoferrocenyl triazine derivatives and investigated their anodic voltammetric behavior. The electronic nature of the third substituent on the triazine nucleus, that is, its electronic donor/acceptor character determines the level of interactions between the two ferrocenyl centers as measured by the separation between their two oxidation half-wave potentials.

Cucurbit[7]uril (CB7) is a macrocycle with the ability to form the most stable supramolecular complexes in water ever reported for an artificial receptor. Its use for the design of advanced functional materials is, however, very limited because there is no example of a fully reversible CB7 based supramolecular complex enabling repetitious dissociation/association controlled by external stimuli. We report the synthesis of a new ferrocene amino acid that forms with CB7 a 1:1 inclusion complex that is stable in submicromolar concentration at low pH but dissociates at high pH. This reversible process was used for the sequential uptake and release of bispyridinium and antraquinone guests by CB7, which is controlled by adjusting the pH of the solution.

The self-assembly in aqueous solution of the well-known cyclophane, cyclobis(paraquat-p-phenylene) (BB(4+) ), and two cucurbit[7]uril (CB7) hosts around a simple hydroquinol-based, diamine guest (GH2 (2+) ) was investigated by (1) H NMR and electronic absorption spectroscopies, electrospray mass spectrometry and DFT computations. The formation of a quaternary supramolecular assembly [GH2 (2+) ⋅BB(4+) ⋅ (CB7)2 ] was shown to be a very efficient process, which takes place not only because of the attractive forces between each of the hosts and the guest, but also because of the lateral interactions between the hosts in the final assembly. This complementary set of attractive interactions results in clear cooperative binding effects that help overcome the entropic barriers for multiple component assembly.

(Ferrocenylmethyl)methylammonium (1H(+)) is an excellent cationic guest for inclusion complexation by the cucurbit[7]uril host. However, deprotonation of the guest leads to a decrease of 14.8 kJ mol(-1) in the overall stability of its inclusion complex, and one-electron oxidation of the guest's ferrocene residue further diminishes the complex stability by another 12.3 kJ mol(-1). Overall, guest deprotonation followed by its oxidation constitutes an accessible method to lower the equilibrium association constant for the CB7·1H(+) complex by more than 4 orders of magnitude.

On the basis of the highly stable G2H (2 : 1) ternary complex formed by two methyl viologen cation radicals inside the cavity of cucurbit[8]uril, we prepared three monocationic 4-phenylpyridinium derivatives: 1-(hydroxyethyl)-4-phenyl-pyridinium (1+) bromide, 1-(octaethyleneglycol)-4-phenyl-pyridinium (2+) chloride, and 4-[4-(methoxymethoxy)phenyl]pyridinium (3+) iodide, as possible guests for 2 : 1 complexation inside cucurbit[8]uril. We also investigated a fourth monocationic guest (4+), in which a central vinylidene group is inserted to elongate the 4-phenyl-pyridinium residue. Using 1H NMR and UV–Vis spectroscopic data and mass spectrometric data, we obtained unequivocal evidence for the formation of G2H (2 : 1) ternary complexes in all cases. The stoichiometry of the complexes was further verified by continuous variation (Job) plots, and in some cases, high resolution ESI-MS spectrometric data. Diffusion coefficient measurements, using 1H NMR pulse gradient spin echo techniques, yielded values consistent with the formation and expected structures of the ternary complexes. Copyright © 2012 John Wiley & Sons, Ltd.

DNA-based vaccines hold promise to outperform conventional antigen-based vaccines by virtue of many unique features. However, DNA vaccines have thus far fallen short of expectations, due in part to poor targeting of professional antigen-presenting cells (APC) and low immunogenicity. In this study, we describe a new platform for effective and selective delivery of DNA to APCs in vivo that offers intrinsic immune-enhancing characteristics. This platform is based on conjugation of fifth generation polyamidoamine (G5-PAMAM) dendrimers, a DNA-loading surface, with MHC class II–targeting peptides that can selectively deliver these dendrimers to APCs under conditions that enhance their immune stimulatory potency. DNA conjugated with this platform efficiently transfected murine and human APCs in vitro. Subcutaneous administration of DNA-peptide-dendrimer complexes in vivo preferentially transfected dendritic cells (DC) in the draining lymph nodes, promoted generation of high affinity T cells, and elicited rejection of established tumors. Taken together, our findings show how PAMAM dendrimer complexes can be used for high transfection efficiency and effective targeting of APCs in vivo, conferring properties essential to generate effective DNA vaccines. Cancer Res; 71(24); 7452–62. ©2011 AACR.

The formation of highly stable inclusion complexes in aqueous solution between the organometallic cobaltocenium cation (Cob(+)) and the hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) was used to develop a simple method, based on UV-vis titrations, to assay the purity of samples of these two hosts. The equilibrium association constant (K) of the Cob(+)@CB7 complex had been previously reported by our group as 5.7 × 10(9) M(-1) at 25 °C in 50 mM sodium acetate medium. In this work, we determine a K value of 1.9 × 10(8) M(-1) at 25 °C in the same medium for the Cob(+)@CB8 complex. The high stability of these complexes and their decreased molar absorptivity coefficients (at 261 nm), compared to that for free Cob(+), lead to straightforward titration plots when graphing absorbance versus concentration of added CB7 (or CB8) host, at constant Cob(+) concentration.

Inclusion of guests inside molecular capsules may have pronounced effects on their chemical reactivity. This article provides a quick summary of research on the electrochemical reactivity of encapsulated redox-active guests. A brief account of the results obtained with simple hosts, such as cyclodextrins and cucurbiturils, starts the article. However, these hosts can only provide partial encapsulation. Most of the article is devoted to the results obtained by the authors’ group on the inclusion of ferrocene, cobaltocenium, and tetrathiafulvalene in molecular capsules formed by cavitand-type ligands, which give rise to supramolecular assemblies that provide full encapsulation. In general terms, trapping of redox-active centers inside molecular capsules leads to a substantial attenuation of their electrochemical kinetics, which results in electrochemically silent properties in extreme cases. However, the magnitude of this kinetic attenuation cannot be rationalized by simple criteria based on the overall size of the supramolecular assembly.

Research on the chemistry of cucurbit[n]uril (CBn) hosts has picked up and maintained an impressive pace in the last decade, primarily due to the isolation of hosts with relatively larger cavity sizes, such as CB7 and CB8. This review article summarizes our involvement in this research effort, with particular emphasis on the binding of redox active guests by the CB7 and CB8 hosts. The binding of 4,4′-bipyridinium (viologen) derivatives was the starting point of our CB research. While methylviologen is encapsulated by CB7, forming a highly symmetric inclusion complex, more hydrophobic viologens are bound by inclusion of one of the terminal N-substituents inside the host cavity. Cationic ferrocene derivatives reach extremely high binding affinities with CB7. Binding by CB8 offers additional possibilities, since this host may accommodate two aromatic units inside its cavity, which can be utilized to exert redox control on the assembly of suitably dendronized guests. From a purely electrochemical standpoint, CB7-included viologens maintain their voltammetric reversibility, but CB7-included ferrocene residues experience a pronounced attenuation of their electron transfer kinetics. We have also applied these binding and electrochemical properties to the design and preparation of switchable, CB-based pseudorotaxanes.

Narrow bandgap conjugated polymers in combination with fullerene acceptors are under intense investigation in the field of organic photovoltaics (OPVs). The open circuit voltage, and thereby the power conversion efficiency, of the devices is related to the offset of the frontier orbital energy levels of the donor and acceptor components, which are widely determined by cyclic voltammetry. Inconsistencies have appeared in the use of the ferrocenium/ferrocene (Fc + /Fc) redox couple, as well as the values used for the absolute potentials of standard electrodes, which can complicate the comparison of materials properties and determination of structure/property relationships.