Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers.

Cyclodextrin nanosponges (CD-NS) are nanostructured crosslinked polymers made up of cyclodextrins. The reactive hydroxy groups of CDs allow them to act as multifunctional monomers capable of crosslinking to bi- or multifunctional chemicals. The most common NS synthetic pathway consists in dissolving the chosen CD and an appropriate crosslinker in organic polar aprotic liquids (e.g., N,N-dimethylformamide or dimethyl sulfoxide), which affect the final result, especially for potential biomedical applications. This article describes a new, green synthetic pathway through mechanochemistry, in particular via ball milling and using 1,1-carbonyldiimidazole as the crosslinker. The polymer obtained exhibited the same characteristics as a CD-based carbonate NS synthesized in a solvent. Moreover, after the synthesis, the polymer was easily functionalized through the reaction of the nucleophilic carboxylic group with three different organic dyes (fluorescein, methyl red, and rhodamine B) and the still reactive imidazoyl carbonyl group of the NS.

Cyclodextrin nanosponge for the GSH-mediated delivery of Resveratrol in human cancer cells.

Smart drug delivery systems are required for the site-specific drug targeting to enhance the therapeutic efficiency of a drug. Resveratrol (RV) is a polyphenolic compound with anti-cancer activity. However, its poor aqueous solubility and non-selectivity are the major challenges for its employment in cancer therapy. In this work, we present the synthesis of RV-loaded glutathione responsive cyclodextrin nanosponges (RV-GSH-NSs) to improve the therapeutic efficiency and selective delivery of RV. The drug loading and encapsulation efficiency were 16.12% and 80.64%, respectively. The in vitro release profile confirmed that RV release was enhanced in response to external glutathione (GSH). Nude NSs were not toxic per se to human fibroblasts when administered for up to 72 h at the highest dose. Cell internalization studies confirmed that RV-GSH-NSs were preferentially up-taken by tumor cells compared to non-tumorigenic cells. Accordingly, RV showed selective toxicity to cancer cells compared to normal cells. GSH depletion by buthionine sulfoximine, a potent inhibitor of its synthesis, reflected in a significant decrease of the NSs accumulation, and consequently resulted in a drastic reduction of RV-mediated toxic effects in cancer cells. These findings demonstrate that GSH- responsive NSs represent an effective delivery system for targeting cancer cells by harnessing the differential tumor characteristics in terms of redox status in parallel with the limitation of side effects toward normal cells.

A physicochemical, thermodynamical, structural and computational evaluation of kynurenic acid/cyclodextrin complexes.

In this work, the interaction between Kynurenic acid (KYNA) and several natural and modified cyclodextrins (CDs) is carried out. Among all the CD tested, HPß-CD showed the strongest complexation constant (KF), with a value of 270.94 ± 29.80 M-1. Between natural (α- and ß-) CDs, the complex of KYNA with ß-CD was the most efficient. The inclusion complex of KYNA with CDs showed a strong influence of pH and temperature. The KF value decreased at high pH values, when the pKa was passed. Moreover, an increase of the temperature caused a decrease in the KF values. The thermodynamic parameters of the complexation (ΔH°, ΔS° and ΔG°) were studied with negative entropy, enthalpy and spontaneity of the process at 25 °C. Moreover, the inclusion complex was also characterized using FTIR and TGA. Finally, molecular docking calculations provided different interactions and their influence in the complexation constant.

Study of oxyresveratrol complexes with insoluble cyclodextrin based nanosponges: Developing a novel way to obtain their complexation constants and application in an anticancer study.

The complexation of the bioactive compound oxyresveratrol (OXY) with a polymer called cyclodextrin-based nanosponge (CD-NS) and its application was studied.A new methodology is used to calculate, an apparent inclusion complex constant (KFapp) between a ligand and CD-NSs. Moreover, the KFapp of resveratrol was also evaluated and compared. The complex of OXY with the nanosponge ß-CDI 1:4, was studied in vitro using DSC, TGA and FTIR techniques and its drug loading and release behavior were studied. An in vitro digestion showed higher protection of OXY complexed than free OXY. The bioactivity enhancing capacity of OXY was also studied against prostate (PC-3) and colon (HT-29 and HCT-116) cancer cell lines, where it showed stronger cell viability inhibition than the free drug. The findings as a whole represent a new opportunity for studying the complexation of drugs in CD-NSs and the use of oxyresveratrol as an ingredient in nutraceutical products.

Eco-Friendly ß-cyclodextrin and Linecaps Polymers for the Removal of Heavy Metals.

Environment-friendly nanosponges, having a high content of carboxyl groups, were synthesized by crosslinking ß-cyclodextrin and linecaps, a highly soluble pea starch derivative, with citric acid in water. Additionally, pyromellitic nanosponges were prepared by reacting ß-cyclodextrin and linecaps with pyromellitic dianhydride in dimethyl sulfoxide and used in comparison with the citric nanosponges. After ion-exchange of the carboxyl groups H+ with sodium ions, the ability of the nanosponges to sequester heavy metal cations was investigated. At a metal concentration of 500 ppm, the pyromellitate nanosponges exhibited a higher retention capacity than the citrate nanosponges. At lower metal concentrations (≤50 ppm) both the citrate and the pyromellitate nanosponges showed high retention capacities (up to 94% of the total amount of metal), while, in the presence of interfering sea water salts, the citrate nanosponges were able to selectively adsorb a significantly higher amount of heavy metals than the pyromellitate nanosponges, almost double in the case of Cu2+.

Evaluation of solubility enhancement, antioxidant activity, and cytotoxicity studies of kynurenic acid loaded cyclodextrin nanosponge.

Kynurenic acid demonstrates antioxidant, neuroprotective and free radical scavenging properties. However, low aqueous solubility of kynurenic acid limits its therapeutic activity. In the present study, cyclodextrin nanosponges were used to improve the solubility and therapeutic activity of kynurenic acid. The formation of kynurenic acid loaded nanosponge was confirmed by different characterization techniques. The solubility of kynurenic acid was significantly increased with nanosponge (111.1 µg/ml) compared to free kynurenic acid (16.4 µg/ml) and ß-cyclodextrin (28.6 µg/ml). High drug loading (19.06%) and encapsulation efficiency (95.31%) were achieved with NS. The particle size and zeta potential of kynurenic acid loaded nanosponge was around 255.8 nm and -23 mV respectively. Moreover, higher solubilization of kynurenic acid loaded nanosponge produced better antioxidant activity compared to free kynurenic acid. The kynurenic acid loaded nanosponge and blank nanosponge were found nontoxic in the cytotoxicity assay. Thus, these studies demonstrated that nanosponges can be used as a carrier for the delivery of kynurenic acid.

Comparative Evaluation of Solubility, Cytotoxicity and Photostability Studies of Resveratrol and Oxyresveratrol Loaded Nanosponges.

Resveratrol and oxyresveratrol are natural polyphenolic stilbenes with several important pharmacological activities. However, low solubility and aqueous instability are the major limitations in their drug delivery applications. In the present work, we demonstrated the encapsulation of resveratrol and oxyresveratrol with nanosponge to improve solubility and stability. Several characterization techniques were used to confirm the encapsulation of both drug molecules within the nanosponges. The high encapsulation efficiency of resveratrol (77.73%) and oxyresveratrol (80.33%) was achieved within the nanosponges. Transmission electron microscopy suggested uniform spherical size particles of resveratrol and oxyresveratrol loaded nanosponges. Compared to free drugs, better protection against UV degradation was observed for resveratrol-loaded nanosponge (2-fold) and oxyresveratrol-loaded nanosponge (3-fold). Moreover, a higher solubilization of resveratrol- and oxyresveratrol-loaded nanosponges lead to a better antioxidant activity compared to drug molecules alone. Cytotoxicity studies against DU-145 prostate cancer cell lines further suggested improved activity of both resveratrol and oxyresveratrol-loaded nanosponges without any significant toxicity of blank nanosponges.

α-Cyclodextrin and α-Cyclodextrin Polymers as Oxygen Nanocarriers to Limit Hypoxia/Reoxygenation Injury: Implications from an In Vitro Model.

The incidence of heart failure (HF) is increasing worldwide and myocardial infarction (MI), which follows ischemia and reperfusion (I/R), is often at the basis of HF development. Nanocarriers are interesting particles for their potential application in cardiovascular disease. Impaired drug delivery in ischemic disease is challenging. Cyclodextrin nanosponges (NS) can be considered innovative tools for improving oxygen delivery in a controlled manner. This study has developed new α-cyclodextrin-based formulations as oxygen nanocarriers such as native α-cyclodextrin (α-CD), branched α-cyclodextrin polymer (α-CD POLY), and α-cyclodextrin nanosponges (α-CD NS). The three different α-CD-based formulations were tested at 0.2, 2, and 20 µg/mL to ascertain their capability to reduce cell mortality during hypoxia and reoxygenation (H/R) in vitro protocols. H9c2, a cardiomyoblast cell line, was exposed to normoxia (20% oxygen) or hypoxia (5% CO2 and 95% N2). The different formulations, applied before hypoxia, induced a significant reduction in cell mortality (in a range of 15% to 30%) when compared to samples devoid of oxygen. Moreover, their application at the beginning of reoxygenation induced a considerable reduction in cell death (12% to 20%). α-CD NS showed a marked efficacy in controlled oxygenation, which suggests an interesting potential for future medical application of polymer systems for MI treatment.