Host–Guest Chemistry of Dendrimer–Cyclodextrin Conjugates: Selective Encapsulations of Guests within Dendrimer or Cyclodextrin Cavities Revealed by NOE NMR Techniques

Abstract

In this study, G5 PAMAM dendrimer and α-, β-, γ-cyclodextrin (CD) conjugates were synthesized. Host-guest behaviors of the conjugates toward five guest molecules including sodium methotrexate (MTX), amantadine hydrochloride (ADH), sulfamethoxazole (SMZ), sodium deoxycholate (SDC), and sodium dodecyl sulfate (SDS) were analyzed by NOE NMR techniques. Among the five guest molecules, ADH only binds with β-CD in G5-β-CD, SDC shows higher priority to localize within the cavity of γ-CD in G5-γ-CD, while MTX exhibits selective encapsulation within the cavities of G5 dendrimer in G5-α-CD. SDS has high binding affinity with α-CD in G5-α-CD but forms a precipitate in the complex solution. SMZ shows simultaneous encapsulation within CDs (α-, β-, and γ-CD) or G5 in the presence of the three conjugates. The host behavior of G5-CD conjugates depends on CD cavity size, guest size, and hydrophobicity. The results obtained in this study are helpful in the optimization of dendrimer-CD conjugate-based drug delivery systems.

Preparation of Cyclodextrin–Iron Species in Water by Laser Ablation: Secondary Ion Mass Spectrometry

“…[14] These supramolecular host-guest complexes have been characterized by phase solubility,h ighperformance liquid chromatography,c ircular dichroism, nuclear magnetic resonance, X-ray powder diffraction,d ifferentials canning calorimetry,t hermogravimetric analysis, UV/Vis spectroscopy and Fourier transform infrared spectroscopy. [15,16] As uitable techniquef or studyingm etallic speciesi ss econdary ion mass spectrometry (SIMS), [17][18][19][20][21] and here this method is used for the first time to study supramolecular complexes between CD and variousiron species. As the CD, we used b-cyclodextrin (C 42 H 70 O 35 )a nd the iron speciesw ere prepared by pulsed-laser ablation of bulk iron in water.T he ablation process generates iron species that causec olouration of the solution, owing to ac ollective oscillation of the electrons in the conduction band, which is knowna ss urfacep lasmon oscillation.…”

β‐Cyclodextrin PAMAM Dendrimer: How to Overcome the Tumbling Process for Getting Fully Available Host Cavities

“…The presence of 4 peripheral β‐CD units confers to this compound a high potential of guest accommodation. The PAMAM core was chosen because it could contribute to great solubility in water for Tetra ‐ CD , without being a competitive encapsulating site contrarily to what was observed with higher generations of PAMAM . We used 2D ROESY NMR experiments to fully characterize the pristine platform and its inclusion complexes formed with adamantane sodium carboxylate ( AdCOONa ) and the poorly water‐soluble adamantane carboxylic acid ( AdCOOH ).…”

pH-Responsive Host–Guest Complexation in Pillar[6]arene-Containing Polyelectrolyte Multilayer Films

“…A variety of host-guest inclusion complexes, supramolecular polymers, and self-assembled nanostructures based on the stimuli-responsive properties of host molecules as the key recognition component were developed [1][2][3][4]. In continuation of a series of well-established hosts such as cyclodextrins [4][5][6][7][8][9] or cucurbiturils [10][11][12][13][14][15], pillar[n]arenes (P[n]) are rather novel representatives as they were only recently reported by Ogoshi et al in 2008 [16-19]. The Lewis-acid catalyzed condensation of 1,4-dimethoxybenzene or hydroquinone units, respectively, yielded pillar [5]arene derivatives bridged by methylene groups in their 2-and 5-positions, therefore revealing a macrocyclic structure with a highly symmetrical shape.…”

“…In continuation of a series of well-established hosts such as cyclodextrins [4][5][6][7][8][9] or cucurbiturils [10][11][12][13][14][15], pillar[n]arenes (P[n]) are rather novel representatives as they were only recently reported by Ogoshi et al in 2008 [16-19]. The Lewis-acid catalyzed condensation of 1,4-dimethoxybenzene or hydroquinone units, respectively, yielded pillar [5]arene derivatives bridged by methylene groups in their 2-and 5-positions, therefore revealing a macrocyclic structure with a highly symmetrical shape. Since then, this novel type of host has attracted great attention on account of the ease of chemical modification, resulting from the reactive substituents located at the upper and lower rim, respectively.…”

“…The π-electron-rich cavity combined with the opportunity of structure-tailoring motivated scientists to investigate the potential of P[n]s in the field of host-guest chemistry. The molecular recognition of P[n = 5,6] towards a series of guest molecules has been reported, showing that cooperative host-guest-interactions such as electrostatics, hydrophobic interactions, charge transfer interactions, hydrogen bonding, and π-π-stacking are responsible for driving the complexation [22,23]. In addition, the introduction of stimuli-responsiveness on either the guest or the host enabled the fabrication of P[n]-guest based complexes, receptors, and drug delivery systems whose assembly could reversibly be switched by tuning either a single or multiple stimuli such as pH, light irradiation, or redox conditions [24][25][26][27][28][29][30][31].…”