Quorum quenching effect of cyclodextrins on the pyocyanin and pyoverdine production of Pseudomonas aeruginosa.

Various virulence determinants in Pseudomonas aeruginosa are regulated by the quorum sensing (QS) network producing and releasing signalling molecules. Two of these virulence determinants are the pyocyanin and pyoverdine, which interfere with multiple cellular functions during infection. The application of QS-inhibiting agents, such as cyclodextrins (CDs), appears to be a promising approach. Further to method development, this research tested in large-volume test systems the effect of α- and ß-CD (ACD, BCD) at 1, 5, and 10 mM concentrations on the production of pyocyanin in the P. aeruginosa model system. The concentration and time-dependent quorum quenching effect of native CDs and their derivatives on pyoverdine production was tested in a small-volume high-throughput system. In the large-volume system, both ACD and BCD significantly inhibited pyocyanin production, but ACD to a greater extent. 10 mM ACD resulted in 58% inhibition, while BCD only ~40%. Similarly, ACD was more effective in the inhibition of pyoverdine production; nevertheless, the results of RMANOVA demonstrated the significant efficiency of both ACD and BCD, as well as their derivatives. Both the contact time and the cyclodextrin treatments significantly influenced pyoverdine production. In this case, the inhibitory effect of ACD after 48 h at 12.5 mM was 57%, while the inhibitory effect of BCD and its derivatives was lower than 40%. The high-level significant inhibition of both pyocyanin and pyoverdine production by ACD was detectable. Consequently, the potential value of CDs as QS inhibitors and the antivirulence strategy should be considered. KEYPOINTS: • Applicability of a simplified method for quantification of pyocyanin production was demonstrated. • The cyclodextrins significantly affected the pyocyanin and pyoverdine production. • The native ACD exhibited the highest attenuation in pyoverdine production.

Long-Chain Alkylthio Cyclodextrin Derivatives for Modulation of Quorum-Sensing-Based Bioluminescence in Aliivibrio fischeri Model System.

Quorum sensing (QS) allows bacteria to coordinate their activities by producing and detecting low-molecular-weight signal molecules based on population density, thereby controlling the infectivity of bacteria through various virulence factors. Quorum-sensing inhibition is a promising approach to tackle bacterial communication. Cyclodextrins (CDs) are a class of cyclic oligosaccharides that reversibly encapsulate the acyl chain of the signal molecules, thereby preventing their binding to receptors and interrupting bacterial communication. This results in the inhibition of the expression of various properties, including different virulence factors. To examine the potential quorum-quenching (QQ) ability of newly prepared cyclodextrin derivatives, we conducted short-term tests using Aliivibrio fischeri, a heterotrophic marine bacterium capable of bioluminescence controlled by quorum sensing. α- and ß-cyclodextrins monosubstituted with alkylthio moieties and further derivatized with quaternary ammonium groups were used as the test agents. The effect of these cyclodextrins on the quorum-sensing system of A. fischeri was investigated by adding them to an exponential growth phase of the culture and then measuring bioluminescence intensity, population growth, and cell viability. Our results demonstrate that the tested cyclodextrins have an inhibitory effect on the quorum-sensing system of A. fischeri. The inhibitory effect varies based on the length of the alkyl chain, with alkylthio substitution enhancing it and the presence of quaternary ammonium groups decreasing it. Our findings suggest that cyclodextrins can be a promising therapeutic agent for the treatment of bacterial infections.

The Impact of Cyclodextrins on the Physiology of Candida boidinii: Exploring New Opportunities in the Cyclodextrin Application.

Cyclodextrins, commonly used as excipients in antifungal formulations to improve the physicochemical properties and availability of the host molecules, have not been systematically studied for their effects and bioactivity without a complex active substance. This paper evaluates the effects of various cyclodextrins on the physiology of the test organism Candida boidinii. The research examines their impact on yeast growth, viability, biofilm formation and morphological changes. Native ACD, BCD, randomly methylated α- and ß-CD and quaternary ammonium α-CD and ß-CD were investigated in the 0.5-12.5 mM concentration range in both static and dynamic systems. The study revealed that certain cyclodextrins exhibited notable antifungal effects (up to ~69%) in dynamic systems; however, the biofilm formation was enhanced in static systems. The magnitude of these effects was influenced by several variables, including the size of the internal cavity, the concentration and structure of the cyclodextrins, and the contact time. Furthermore, the study found that CDs exhibited distinct effects in both static and dynamic systems, potentially related to their tendency to form aggregates. The findings suggest that cyclodextrins may have the potential to act as antifungal agents or growth promoters, depending on their structure and surrounding environments.

Effect of Cyclodextrins on the Biofilm Formation Capacity of Pseudomonas aeruginosa PAO1.

Quorum sensing (QS) is a population-density-dependent communication process of microorganisms to coordinate their activities by producing and detecting low-molecular-weight signal molecules. In pathogenic bacteria, the property controlled by QS is often related to infectivity, e.g., biofilm formation. Molecular encapsulation of the QS signals is an innovative method to prevent the signals binding to the receptors and to attenuate QS. Cyclodextrins (CDs) may form an inclusion complex with the signals, thus reducing the communication (quorum quenching, QQ). A systematic study was performed with α-, ß-cyclodextrin, and their random methylated, quaternary amino and polymer derivatives to evaluate and compare their effects on the biofilm formation of Pseudomonas aeruginosa. To examine the concentration-, temperature- and time-dependency of the QQ effect, the CDs were applied at a 0.1-12.5 mM concentration range, and biofilm formation was studied after 6, 24, 48 and 72 h at 22 and 30 °C. According to the results, the QS mechanism was significantly inhibited; the size of the cavity, the structure of the substituents, as well as the monomeric or polymeric character together with the concentration of the CDs have been identified as key influencing factors of biofilm formation. Statistically determined effective concentration values demonstrated outstanding efficiency (higher than 80% inhibition) of α-CD and its random methylated and polymer derivatives both on the short and long term. In summary, the potential value of CDs as inhibitors of QS should be considered since the inhibition of biofilm formation could significantly impact human health and the environment.

Cellular Effects of Cyclodextrins: Studies on HeLa Cells.

Cyclodextrins are high molecular weight, hydrophilic, cyclic, non-reducing oligosaccharides, applied as excipients for the improvement of the solubility and permeability of insoluble active pharmaceutical ingredients. On the other hand, beta-cyclodextrins are used as cholesterol sequestering agents in life sciences. Recently, we demonstrated the cellular internalization and intracellular effects of cyclodextrins on Caco-2 cells. In this study, we aimed to further investigate the endocytosis of (2-hydroxylpropyl)-beta-(HPBCD) and random methylated-beta-cyclodextrin (RAMEB) to test their cytotoxicity, NF-kappa B pathway induction, autophagy, and lysosome formation on HeLa cells. These derivatives were able to enter the cells; however, major differences were revealed in the inhibition of their endocytosis compared to Caco-2 cells. NF-kappa B p65 translocation was not detected in the cell nuclei after HPBCD or RAMEB pre-treatment and cyclodextrin treatment did not enhance the formation of autophagosomes. These cyclodextrin derivates were partially localized in lysosomes after internalization.

A Three-Color Fluorescent Supramolecular Nanoassembly of Phototherapeutics Activable by Two-Photon Excitation with Near-Infrared Light.

A supramolecular nanoassembly, of about 30 nm in diameter, that consists of a green-fluorescent, ß-cyclodextrin-based, branched polymer co-encapsulating a red-emitting singlet oxygen (1 O2 ) photosensitizer and a nitric oxide (NO) photoreleaser, which comprises a blue fluorescent reporter, is here reported. The system exhibits "five-in-one" photofunctionalities. All components can be simultaneously excited in the phototherapeutic window with two-photons by using near-infrared light at 740 nm and despite their close proximity, behave as independent units. This allows for their in vitro visualization in carcinoma cancer cells, due to their distinct green, red, and blue fluorescence, and for the production of both cytotoxic 1 O2 and biofunctional NO.

Homo- and hetero-difunctionalized ß-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry.

The regioselective difunctionalization of cyclodextrins (CDs) leading to derivatives amenable to further transformations is a daunting task due to challenging purification and unambiguous characterization of the obtained regioisomers with similar physicochemical properties. The primary-side homo-difunctionalization of ß-CD can lead to three regioisomers, while the hetero-difunctionalization can generate three pairs of pseudoenantiomers. Previously, approaches with several synthetic steps, expensive reagents, high purification demands and low yields of the products have been employed. Herein we present direct, short and efficient primary-side difunctionalization strategies featuring reproducibility, ease of product purification, scalability of the reactions and versatility of the substituents introduced. Specifically, the prepared ditosylated ß-CDs were separated using preparative reversed-phase column chromatography and their structures were elucidated by NMR experiments. Azidation led to the corresponding pure diazido regioisomers. Direct monotosylation of 6-monoazido-ß-CD or monoazidation of the single regioisomers 6A,6X-ditosyl-ß-CDs afforded hetero-difunctionalized 6A-monoazido-6X-tosyl-ß-CDs in significant yields. Overall, the single regioisomers, 6A,6X-ditosyl-, 6A,6X-diazido- and 6A-monoazido-6X-monotosyl-ß-CD were prepared in one or two steps and purified in multigram scale thus opening the way towards further selective and orthogonal functionalizations of ß-CD hosts.

Widening the Therapeutic Perspectives of Clofazimine by Its Loading in Sulfobutylether ß-Cyclodextrin Nanocarriers: Nanomolar IC50 Values against MDR S. epidermidis.

Clofazimine (CLZ) is an antibiotic with a promising behavior against Gram-positive bacteria; however, the drug is completely insoluble in water and accumulates in fat tissues. We explored nanocarriers, labeled and not labeled with rhodamine, consisting of negatively charged sulfobutylether-ß-cyclodextrins for CLZ loading. A new oligomeric carrier was obtained cross-linking ßCyD with epichlorohydrin followed by sulfonation in a strongly alkaline aqueous medium. The oligomeric carrier has a MW of 53 kDa and forms small nanoparticles of a few tens of nm. With aqueous solutions containing a 25 mg/mL oligomeric carrier, we loaded up to 0.5 mg/mL of drug. The oligomers exhibited a 10-fold better loading capacity compared to monomers and formed nanoparticles with a size in the 20-60 nm range after drug loading. Circular dichroism confirmed encapsulation of the CLZ in the nanocarriers. All carriers with or without CLZ are not cytotoxic up to 1 µM, while CLZ alone is highly cytotoxic at the same concentration. The drug has IC50 values below 100 nM against S. epidermidis. The same holds true also for clinical isolates of S. epidermidis, some displaying MDR. So, the selectivity index significantly increased for CLZ/carrier systems compared to the drug alone. Taken all together, our results open new avenues for the clinical application of this antibiotic.

Cyclodextrin-Enabled Polymer Composites for Packaging †.

Cyclodextrin complexes of fragrances, antimicrobial agents, dyes, insecticides, UV-filters can be incorporated into polymers (packaging films, trays, containers) either to ensure the slow release or a homogeneous distribution of the complexed substances. This way the propagation of microorganisms on surface of enwrapped products is decelerated, or the product is made more attractive by slowly released fragrances, protected against UV-light-induced deterioration, oxidation, etc. Incorporating empty cyclodextrins into the packaging material an aroma barrier packaging is produced, which decelerates the loss of the aroma from the packaged food, prevents the penetration of undesired volatile pollutants from the environment, like components of exhaust gases, cigarette smoke, and reduces the migration of plasticizers, residual solvents and monomers, etc. Applying cyclodextrins in active packaging allows to preserve the quality of food and ensures a longer shelf-life for the packaged items.

A non-covalent "click chemistry" strategy to efficiently coat highly porous MOF nanoparticles with a stable polymeric shell.

BACKGROUND: Metal-organic framework nanoparticles (nanoMOFs) are biodegradable highly porous materials with a remarkable ability to load therapeutic agents with a wide range of physico-chemical properties. Engineering the nanoMOFs surface may provide nanoparticles with higher stability, controlled release, and targeting abilities. Designing postsynthetic, non-covalent self-assembling shells for nanoMOFs is especially appealing due to their simplicity, versatility, absence of toxic byproducts and minimum impact on the original host-guest ability. METHODS: In this study, several ß-cyclodextrin-based monomers and polymers appended with mannose or rhodamine were randomly phosphorylated, and tested as self-assembling coating building blocks for iron trimesate MIL-100(Fe) nanoMOFs. The shell formation and stability were studied by isothermal titration calorimetry (ITC), spectrofluorometry and confocal imaging. The effect of the coating on tritium-labeled AZT-PT drug release was estimated by scintillation counting. RESULTS: Shell formation was conveniently achieved by soaking the nanoparticles in self-assembling agent aqueous solutions. The grafted phosphate moieties enabled a firm anchorage of the coating to the nanoMOFs. Coating stability was directly related to the density of grafted phosphate groups, and did not alter nanoMOFs morphology or drug release kinetics. CONCLUSION: An easy, fast and reproducible non-covalent functionalization of MIL-100(Fe) nanoMOFs surface based on the interaction between phosphate groups appended to ß-cyclodextrin derivatives and iron(III) atoms is presented. GENERAL SIGNIFICANCE: This study proved that discrete and polymeric phosphate ß-cyclodextrin derivatives can conform non-covalent shells on iron(III)-based nanoMOFs. The flexibility of the ß-cyclodextrin to be decorated with different motifs open the way towards nanoMOFs modifications for drug delivery, catalysis, separation, imaging and sensing. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editors: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Novel ß-cyclodextrin-eosin conjugates.

Eosin B (EoB) and eosin Y (EoY), two xanthene dye derivatives with photosensitizing ability were prepared in high purity through an improved synthetic route. The dyes were grafted to a 6-monoamino-ß-cyclodextrin scaffold under mild reaction conditions through a stable amide linkage using the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride. The molecular conjugates, well soluble in aqueous medium, were extensively characterized by 1D and 2D NMR spectroscopy and mass spectrometry. Preliminary spectroscopic investigations showed that the ß-cyclodextrin-EoY conjugate retains both the fluorescence properties and the capability to photogenerate singlet oxygen of the unbound chromophore. In contrast, the corresponding ß-cyclodextrin-EoB conjugate did not show either relevant emission or photosensitizing activity probably due to aggregation in aqueous medium, which precludes any response to light excitation.

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants.

Advanced oxidation processes (AOPs) are considered highly competitive water treatment technologies for the removal of organic pollutants. Among AOP techniques, photocatalysis has recently been the most widely studied. Our aims were to investigate how the dispersion of nanosized titanium dioxide (nanoTiO2) applied in photodegradation-based procedures can be stabilized with cyclodextrins in order to obtain a new, more efficient photocatalyst for the purification of waters polluted by xenobiotics applying UV irradiation. During our work, on the one hand, we studied the behavior and stability of nanoTiO2 in cyclodextrin solutions. On the other hand, we used various monomer and polymer cyclodextrin derivatives, and assessed the options for nanoTiO2 stabilization in the presence of various salts and tap water on the basis of turbidity tests. The physical stability of nanoTiO2 dispersions is diminished in the presence of the salts found in tap water (and occurring also in surface waters and ground water) and they are precipitated immediately. This colloidal instability can be improved by cyclodextrin derivatives. Based on the results of our studies we have selected carboxymethyl ß-cyclodextrin polymer (CMBCD-P) for stabilization of nanoTiO2 dispersions. The photocatalytic degradation of methylene blue and ibuprofen as model organic pollutants in various media (distilled water, NaCl solution and tap water) has been studied using nanoTiO2 as catalyst stabilized by CMBCD-P. CMBCD-P itself showed a catalytic effect on the UV degradation of methylene blue. In addition to enhancing the colloid stability of nanoTiO2 CMBCD-P showed also synergistic effects in catalyzing the photodecomposition process of the dye. On the other hand, ibuprofen as a model pharmaceutical, a pollutant of emerging concern (EP), was protected by CMBCD-P against the photocatalytic degradation showing that inclusion complex formation can result in opposite effects depending on the structure of the host-guest complex.

Supramolecular structures based on regioisomers of cinnamyl-α-cyclodextrins - new media for capillary separation techniques.

This work focuses on the preparation and application of supramolecular structures based on mono-cinnamyl-α-cyclodextrins (Cin-α-CD). Pure regioisomers of Cin-α-CD having the cinnamyl moiety at the 2-O- or at the 3-O-position, respectively, were prepared, characterized and applied in capillary electrophoresis as additives to the background electrolyte. These new monomer units with a potential to self-organize into supramolecular structures were synthesized via a straightforward one-step synthetic procedure and purified using preparative reversed-phase chromatography allowing a large scale separation of the regioisomers. The ability of the monomers to self-assemble was proved by various methods including NMR spectroscopy and dynamic light scattering (DLS). The light scattering experiments showed that the monomer units have distinguishable ability to form supramolecular structures in different solvents and the size distribution of the aggregates in water can be easily modulated using different external stimuli, such as temperature or competitive guest molecules. The obtained results indicated that the two regioisomers of Cin-α-CD formed different supramolecular assemblies highlighting the fact that the position of the cinnamyl group plays an important role in the intermolecular complex formation.

Evaluation of the Cytotoxicity of α-Cyclodextrin Derivatives on the Caco-2 Cell Line and Human Erythrocytes.

Cyclodextrins, even the 6-membered α-cyclodextrin, are approved in the various pharmacopoeias as pharmaceutical excipients for solubilizing and stabilizing drugs as well as for controlling drug release. Recently α-cyclodextrin has also been marketed as health food with beneficial effects on blood lipid profiles. However, the concentration of α-cyclodextrin used may be very high in these cases, and its toxic attributes have to be seriously considered. The objective of this study was to investigate the cytotoxicity of various, differently substituted α-cyclodextrin derivatives and determine relationship between the structures and cytotoxicity. Three different methods were used, viability tests (MTT assay and Real Time Cell Electronic Sensing on Caco-2 cells) as well as hemolysis test on human red blood cells. The effect of α-cyclodextrin derivatives resulted in concentration-dependent cytotoxicity, so the IC50 values have been determined. Based on our evaluation, the Real Time Cell Electronic Sensing method is the most accurate for describing the time and concentration dependency of the observed toxic effects. Regarding the cytotoxicity on Caco-2 cells, phosphatidylcholine extraction may play a main role in the mechanism. Our results should provide help in selecting those α-cyclodextrin derivatives which have the potential of being used safely in medical formulations.

Effects of RAMEA-complexed polyunsaturated fatty acids on the response of human dendritic cells to inflammatory signals.

The n-3 fatty acids are not produced by mammals, although they are essential for hormone synthesis and maintenance of cell membrane structure and integrity. They have recently been shown to inhibit inflammatory reactions and also emerged as potential treatment options for inflammatory diseases, such as rheumatoid arthritis, asthma and inflammatory bowel diseases. Dendritic cells (DC) play a central role in the regulation of both innate and adaptive immunity and upon inflammatory signals they produce various soluble factors among them cytokines and chemokines that act as inflammatory or regulatory mediators. In this study we monitored the effects of α-linoleic acid, eicosapentaenoic acid and docosahexaenoic acid solubilized in a dimethyl sulfoxide (DMSO)/ethanol 1:1 mixture or as complexed by randomly methylated α-cyclodextrin (RAMEA) on the inflammatory response of human monocyte-derived dendritic cells (moDC). The use of RAMEA for enhancing aqueous solubility of n-3 fatty acids has the unambiguous advantage over applying RAMEB (the ß-cyclodextrin analog), since there is no interaction with cell membrane cholesterol. In vitro differentiated moDC were left untreated or were stimulated by bacterial lipopolysaccharide and polyinosinic:polycytidylic acid, mimicking bacterial and viral infections, respectively. The response of unstimulated and activated moDC to n-3 fatty acid treatment was tested by measuring the cell surface expression of CD1a used as a phenotypic and CD83 as an activation marker of inflammatory moDC differentiation and activation by using flow cytometry. Monocyte-derived DC activation was also monitored by the secretion level of the pro- and anti-inflammatory cytokines IL-1ß, TNF-α, IL-6, IL-10 and IL-12, respectively. We found that RAMEA-complexed n-3 fatty acids reduced the expression of CD1a protein in both LPS and Poly(I:C) stimulated moDC significantly, but most efficiently by eicosapentaenic acid, while no significant change in the expression of CD83 protein was observed. The production of IL-6 by LPS-activated moDC was also reduced significantly when eicosapentaenic acid was added as a RAMEA complex as compared to its DMSO-solubilized form or to the other two n-3 fatty acids either complexed or not. Based on these results n-3 fatty acids solubilized by RAMEA provide with a new tool for optimizing the anti-inflammatory effects of n-3 fatty acids exerted on human moDC and mediated through the GP120 receptor without interfering with the cell membrane structure.

Synthesis of modified cyclic and acyclic dextrins and comparison of their complexation ability.

We compared the complex forming ability of α-, ß- and γ-cyclodextrins (α-CD, ß-CD and γ-CD) with their open ring analogs. In addition to the native cyclodextrins also modified cyclodextrins and the corresponding maltooligomers, functionalized with neutral 2-hydroxypropyl moieties, were synthesized. A new synthetic route was worked out via bromination, benzylation, deacetylation and debenzylation to obtain the 2-hydroxypropyl maltooligomer counterparts. The complexation properties of non-modified and modified cyclic and acyclic dextrins were studied and compared by photon correlation spectroscopy (PCS) and capillary electrophoresis (CE) using model guest compounds. In some cases cyclodextrins and their open-ring analogs (acyclodextrins) show similar complexation abilities, while with other guests considerably different behavior was observed depending on the molecular dimensions and chemical characteristics of the guests. This was explained by the enhanced flexibility of the non-closed rings. Even the signs of enantiorecognition were observed for the chloropheniramine/hydroxypropyl maltohexaose system. Further studies are planned to help the deeper understanding of the interactions.

Synthetic strategies for the fluorescent labeling of epichlorohydrin-branched cyclodextrin polymers.

The fluorescent tagging of cyclodextrin derivatives enlarges their spectroscopic properties thus generating chemosensors, biological tools for visualization and sophisticated photoresponsive devices. Cyclodextrin polymers, due to the cooperative interactions, exhibit additional properties compared to their monomeric counterpart. These macromolecules can be prepared either in well water-soluble form or as gels of high swelling. Two versatile synthetic strategies for introducing a fluorescent tag (rhodamine, fluorescein, nitrobenzofuran or coumarin) into the water-soluble epichlorohydrin branched cyclodextrin polymers were worked out and compared. The fluorescent labeling was realized in three steps: 1) building in azido moieties, 2) transforming the azido groups into amino groups and 3) coupling the proper fluorescent compound to the amino groups. The other strategy started by functionalization of the monomer prior to the branching. Either the fluorescent-labeled monomer or the intermediate azido derivative of the monomer was branched. Further tuning of the properties of the polymer was achieved via branching of the methylated cyclodextrin derivative. The key intermediates and the fluorescent final products were characterized by various spectroscopic techniques and capillary electrophoresis. The applied synthetic routes were evaluated based on the molecular weight, cyclodextrin content of the products and the efficiency of labeling.

Cyclodextrin derivatives decrease Transient Receptor Potential vanilloid 1 and Ankyrin 1 ion channel activation via altering the surrounding membrane microenvironment by cholesterol depletion.

Transient Receptor Potential Vanilloid 1 (TRPV1) and Ankyrin 1 (TRPA1) are nonselective cation channels expressed in primary sensory neurons and several other non-neuronal structures such as immune cells, keratinocytes, and vascular smooth muscle cells. They play important roles in nociception, pain processing and their chanellopathies are associated with the development of several pathological conditions. They are located in cholesterol- and sphingolipid-rich membrane lipid raft regions serving as platforms to modulate their activations. We demonstrated earlier that disruption of these lipid rafts leads to decreased TRP channel activation and exerts analgesic effects. Cyclodextrins are macrocyclic molecules able to form host-guest complexes with cholesterol and deplete it from the membrane lipid rafts. The aim of this study was to investigate 8 structurally different (methylated and non-methylated) CD derivatives on cell viability, mitochondrial membrane potential, membrane composition and activation abilities of the TRPV1 and TRPA1 channels. We showed that non-methylated derivatives have preferable safety profiles compared to methylated ones. Furthermore, methylated derivatives reduced mitochondrial membrane potential. However, all investigated derivatives influence the ordered cell membrane structure depleting membrane cholesterol and inhibit the TRPV1 agonist capsaicin- and the TRPA1 agonist allyl isothiocyanate-induced Ca2+-influx. This mechanism of action might provide novel perspectives for the development of peripherally acting analgesics via indirectly decreasing the generation and transmission of nociceptive signals.

Citric acid-γ-cyclodextrin crosslinked oligomers as carriers for doxorubicin delivery.

Two citric acid crosslinked γ-cyclodextrin oligomers (pγ-CyD) with a MW of 21-33 kDa and 10-15 γ-CyD units per molecule were prepared by following green chemistry methods and were fully characterized. The non-covalent association of doxorubicin (DOX) with these macromolecules was investigated in neutral aqueous medium by means of circular dichroism (CD), UV-vis absorption and fluorescence. Global analysis of multiwavelength spectroscopic CD and fluorescence titration data, taking into account the DOX monomer-dimer equilibrium, evidenced the formation of 1 : 1 and 1 : 2 pγ-CyD unit-DOX complexes. The binding constants are 1-2 orders of magnitude higher than those obtained for γ-CyD and depend on the characteristics of the oligomer batch used. The concentration profiles of the species in solution evidence the progressive monomerization of DOX with increasing oligomer concentration. Confocal fluorescence imaging and spectral imaging showed a similar drug distribution within the MCF-7 cell line incubated with either DOX complexed to pγ-CyD or free DOX. In both cases DOX is taken up into the cell nucleus without any degradation.

Cyclodextrin-enabled green environmental biotechnologies.

Most of the organic compounds contaminating the environment can form inclusion complexes with cyclodextrins resulting in enhanced solubility (a benefit in soil remediation) or just the opposite: reduced mobility by sorption (a benefit in wastewater treatment). Combining biotechnologies with cyclodextrin, a renewable and biodegradable material, green environmental technologies of high efficiency were developed. For instance, the cyclodextrin-enabled soil washing/flushing technologies combined with bioremediation have been demonstrated in full-scale field experiments. The efficiency of tertiary wastewater treatment by sorption of non-biodegradable xenobiotics, such as residual pharmaceutics, was proved. The biofilm formation in fouling processes can be prevented or reduced either by applying cyclodextrin-based coatings or by manipulation of quorum sensing (bacterial communication) via capturing signal molecules.