Pyriproxyfen cyclodextrin inclusion compounds

Rational design of a dual-mode fluorescent probe for portable detection of pyriproxyfen in the environment and food

The development of a fluorescent probe for pyriproxyfen (PPF) is crucial due to its potential threat to human health. However, the chemical inertness and low solubility of PPF present significant challenges for the detection of PPF in aqueous solutions using fluorescent probes. Herein, we have originally proposed a complex based on 2-(4-(dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4 H-chromen-4-one (HOF) and serum albumin (SA) as a dual-mode fluorescent probe, HOF@SA. This probe utilizes an indicator displacement assay (IDA) to release the dye HOF from the probe at low PPF concentrations (< 10 µM) and embeds the free dye HOF into the micelle of PPF at high concentrations (> 10 µM). This results in dual-mode fluorescent response characteristics for PPF: a turn-off response at low concentrations and a ratiometric response at high concentrations. An investigation of sensing behavior of HOF@SA for PPF detection exhibits rapid response (< 60 s), high sensitivity (LOD ∼4.7 ppb), high selectivity, and excellent visual detection capability (from cyan to yellow). Moreover, with the aid of a portable device, this method enables to analyze PPF in environmental and food samples. These results promote the advancement of a fluorescent probe approach for PPF analysis in environment and food.

Delivery of pharmaceuticals and other active ingredients with their crystalline cyclodextrin inclusion compounds

In honor of Prof. Thorsteinn Loftsson's 70th birthday, we offer this personal review of our work using cyclodextrins (CDs) complexed with a variety of active ingredients, including pharmaceuticals, for the purpose of improving their delivery to polymer materials, e.g., fibers, films, hydrogels, etc. Using the affinity of CDs to host and form non-covalent inclusion complexes (ICs) with guest molecules, including a variety of high molecular weight polymers, it is possible to readily deliver these guest molecules into polymer materials via either melt or solution processing of their crystalline or soluble guest molecule-CD-ICs or -rotaxanes. This provides the following advantages: i. CDs are non-toxic, implantable, and biodegradable and have earned the GRAS rating from the FDA. ii. Guest molecules, even those that are neat liquids, can form solid crystalline CD-ICs that are thermally stable to ~ 200 °C and above. This approach permits facile melt-processing into polymer materials for delivery without migration, loss, or degradation of the active guest ingredient. iii. For guests harmful and toxic to their users and the environment, delivery in the form of crystalline CD-ICs can limit any contact with and release of the included toxic guests before they function and are used. iv. It has been demonstrated that, by simple precipitation methods, neat as-received CDs that adopt cage crystal structures can be readily transformed to their columnar crystal structures containing only water in their channels, which can be easily displaced by small molecule, as well as polymer guests. v. Guest-CD-rotaxanes are water soluble, they protect the threaded guest from sources of degradation, and the CD hydroxyl groups may be modified to direct the guest-CD-rotaxane to specific substrates. For these reasons, here we summarize our contributions to the study of CD inclusion and delivery of a variety of guest molecules, including antibacterials, spermicides, insecticides, flame retardants, and dyes, that can more usefully functionalize polymer materials.

Rational Design, Synthesis and Evaluation of γ-CD-Containing Cross-Linked Polyvinyl Alcohol Hydrogel as a Prednisone Delivery Platform

This study describes the in-silico rational design, synthesis and evaluation of cross-linked polyvinyl alcohol hydrogels containing γ-cyclodextrin (γ-CDHSAs) as platforms for the sustained release of prednisone (PDN). Through in-silico studies using semi-empirical quantum mechanical calculations, the effectiveness of 20 dicarboxylic acids to generate a specific cross-linked hydrogel capable of supporting different amounts of γ-cyclodextrin (γ-CD) was evaluated. According to the interaction energies calculated with the in-silico studies, the hydrogel made from PVA cross-linked with succinic acids (SA) was shown to be the best candidate for containing γ-CD. Later, molecular dynamics simulation studies were performed in order to evaluate the intermolecular interactions between PDN and three cross-linked hydrogel formulations with different proportions of γ-CD (2.44%, 4.76% and 9.1%). These three cross-linked hydrogels were synthesized and characterized. The loading and the subsequent release of PDN from the hydrogels were investigated. The in-silico and experimental results showed that the interaction between PDN and γ-CDHSA was mainly produced with the γ-CDs linked to the hydrogels. Thus, the unique structures and properties of γ-CDHSA demonstrated an interesting multiphasic profile that could be utilized as a promising drug carrier for controlled, sustained and localized release of PDN.

Molecular Encapsulation of Herbicide Terbuthylazine in Native and Modifiedβ-Cyclodextrin

The herbicide terbuthylazine (TBA) is widely used for preemergence or postemergence control of many grass and broadleaf weeds and has, besides other issues, a poor aqueous solubility profile that results in reduced bioavailability. Cyclodextrins and modified cyclodextrins were considered, among other substances, appropriate agents for improving pesticide water solubility. Therefore, the inclusion complex formation of terbuthylazine withβ-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was studied to attain its aqueous solubility enhancement. Their characterization was accomplished with different analytical techniques, namely, by UV-Vis, DSC, FTIR, and1H NMR. From the analysis of the complexation performance of the herbicide it was concluded that the interaction of terbuthylazine with CDs leads to the formation of inclusion complexes with a stoichiometry of 1 : 1. The association constants of the TBA/β-CD and TBA/HP-β-CD complexes were determined by UV. The mean values obtained for the stability constants are 460.4 ± 26.5 and 532.1 ± 27.6 to TBA/β-CD and TBA/HP-β-CD, respectively.1H NMR data corroborate the formation of the TBA/β-CD and TBA/HP-β-CD complexes synthesized by the kneading method. A formulation incorporating TBA cyclodextrin complexes might lead to an improvement in terbuthylazine bioavailability. The development of TBA-CD formulations may be interesting since it would enable, through their inclusion into the hydrophobic cavity of CDs, enhancement of solubility, bioavailability, and stability of the herbicide.

Factors Affecting the Formation of 2:1 Host:Guest Inclusion Complexes of 2-[(R-Phenyl)amine]-1,4-naphthalenediones (PAN) in β- and γ-Cyclodextrins

The molecular hosts cyclodextrins form inclusion complexes with a wide variety of guests, resulting in complexes with various host:guest stoichiometries. In the case of a series of 19 1,4-naphthoquinolines as guests with either β- or γ-cyclodextrin studied using electrospray mass spectroscopy, in most cases only 1:1 complexes were observed, with 2:1 host:guest complexes observed in just 6 out of 38 host:guest combinations. It is shown that these higher-order complexes were observed only in the case of small (or no) electronically withdrawing substituents, and were much less likely in the case of the larger γ-cyclodextrin host. The size and electronic properties of the substituents involved shows that both steric and electronic factors must be taken into account in predicting which cyclodextrin host:guest stoichiometries will be stable enough to form (or once formed, be robust enough to be observed in the ESI-MS experiments). It is clear that the prediction of host-guest stoichiometry for a specific host-guest pair is complicated, and involves a subtle interplay of both electronic and steric factors. However, there are definite trends, which can be used to help predict host:guest stoichiometry for a given host-guest pair.