Characterization of magnetic guar gum-grafted carbon nanotubes and the adsorption of the dyes

The hydrophobicity of carbon nanotubes (CNTs) limits their extensive application. The hydrophilicity and biocompatibility of CNTs can be improved by modifying them with biopolymers. As a natural biopolymer, guar gum (GG) was covalently grafted on the surfaces of multiwall carbon nanotube (MWCNT) to obtain GG-MWCNT composite. Then iron oxide nanoparticles were synthesized on the GG-MWCNT to prepare the magnetic GG-MWCNT-Fe₃O₄. The obtained nanocomposites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, ultraviolet-visible (UV-vis) spectroscopy and X-ray diffraction. GG-MWCNT was composed of about 21.6 wt% GG components, which enhanced the dispersion of GG-MWCNT in aqueous solution and also acted as a template for growth of iron oxide nanoparticles. GG-MWCNT-Fe₃O₄ exhibited superparamagnetic with a saturation magnetization (13.3 emu g⁻¹), and good adsorption on neutral red and methylene blue. GG-MWCNT-Fe₃O₄ could be easily separated from the aqueous solution in a magnetic field.     

Synthesized β-cyclodextrin modified graphene oxide (β-CD-GO) composite for adsorption of cadmium and their toxicity profile in cervical cancer (HeLa) cell lines

In the current study, a composite material was constructed using β-cyclodextrin/graphene oxide (β-CD-GO) and was then applied for the purpose of eliminating cadmium (Cd) from aqueous solution. The synthesized β-CD-GO composite material was then subjected to characterization using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The batch study was conducted for the purpose of removing Cd(II). The results of the study revealed that the β-CD-GO composite material demonstrated a high adsorption capacity of 196 mg/g of Cd(II) at pH 7.0. Further, the adsorption of Cd(II) on the β-CD-GO followed pseudo second-order kinetics and equilibrium adsorption data, which fitted well to the Langmuir isotherm model. The evaluation of the toxicity of the synthesized β-CD-GO composite material was done by the examination of the cervical cancer (HeLa) cell lines. Increasing concentration of β-CD-GO composite material (50 μg to 200 μg) leads to a decline in the percentage of cell viability as from 74 % to 25 %. This study has suggested that the β-CD-GO could play an efficient and beneficial source of the adsorbent for the purpose of eliminating Cd(II) from aqueous solution.     

The role of encapsulation by β-cyclodextrin in the interaction of raloxifene with macromolecular targets: a study by spectroscopy and molecular modeling

We report the binding of the drug raloxifene with Calf thymus DNA (ctDNA) and bovine serum albumin (BSA) in the presence and absence of β-cyclodextrin (β-CD) and explain the influence of β-cyclodextrin on the binding of the drug to macromolecules. UV-Vis absorption, fluorescence, proton nuclear magnetic resonance and two-dimensional rotating-frame nuclear overhauser effect spectroscopic techniques are used to study the stoichiometry and the binding strength of the complexes. Molecular modeling is used in combination with other techniques to propose the structure of the inclusion complex and the interaction with ctDNA. The Stern–Volmer quenching constants of the interaction of raloxifene with ctDNA in aqueous and in β-CD solution are compared. The competition for binding of ctDNA with raloxifene and Methylene Blue is studied. The apparent binding constant and the number of binding sites for the binding of raloxifene with BSA in aqueous solution are significantly different from those in the presence of β-CD. The influence of β-CD on the binding of the small molecules with biological macromolecules is discussed. We infer that the binding strengths between raloxifene and macromolecules, viz., ctDNA and BSA are influenced by the β-CD encapsulation. These results may suggest new ways to tune the drug binding to biomacromolecules by encapsulating specific moieties of drugs.     

Binding Interactions of Naringenin and Naringin with Calf Thymus DNA and the Role of β-Cyclodextrin in the Binding

The interaction of naringenin (Nar) and its neohesperidoside, naringin (Narn), with calf thymus deoxyribonucleic acid (ctDNA) in the absence and the presence of β-cyclodextrin (β-CD) was investigated. The interaction of Nar and Narn with β-CD/ctDNA was analyzed by using absorption, fluorescence, and molecular modeling techniques. Docking studies showed the existence of hydrogen bonding, electrostatic and phobic interaction of Nar and Narn with β-CD/DNA. 1:2 stoichiometric inclusion complexes were observed for Nar and Narn with β-CD. With the addition of ctDNA, Nar and Narn resulted into the fluorescence quenching phenomenon in the aqueous solution and β-CD solution. The binding constant K _b and the number of binding sites were found to be different for Nar and Narn bindings with DNA in aqueous and β-CD solution. The difference is attributed to the structural difference between Nar and Narn with neohesperidoside moiety present in Narn.     

Glycol chitosan/heparin immobilized iron oxide nanoparticles with a tumor-targeting characteristic for magnetic resonance imaging

We described the preparation of the glycol chitosan/heparin immobilized iron oxide nanoparticles (composite NPs) as a magnetic resonance imaging agent with a tumor-targeting characteristic. The iron oxide nanoseeds used clinically as a magnetic resonance imaging agent were immobilized into the glycol chitosan/heparin network to form the composite NPs. To induce the ionic interaction between the iron oxide nanoseeds and glycol chitosan, gold was deposited on the surface of iron oxide nanoseeds. After the immobilization of gold-deposited iron oxide NPs into the glycol chitosan network, the NPs were stabilized with heparin based on the ionic interaction between cationic glycol chitosan and anionic heparin. FE-SEM (field emission-scanning electron microscopy) and a particle size analyzer were used to observe the formation of the stabilized composite NPs, and a Jobin-Yvon Ultima-C inductively coupled plasma-atomic emission spectrometer (ICP-AES) was used to measure the contents (%) of formed iron oxide nanoseeds as a function of reaction temperature and formed gold deposited on the iron oxide nanoparticles. We also evaluated the time-dependent excretion profile, in vivo biodistribution, circulation time, and tumor-targeting ability of the composite NPs using a noninvasive NIR fluorescence imaging technology. To observe the MRI contrast characteristic, the composite NPs were injected into the tail veins of tumor-bearing mice to demonstrate their selective tumoral distribution. The MR images were collected with conventional T(2)-weighted spin echo acquisition parameters.     

Molecular recognition and enhancement of aqueous solubility and bioactivity of CD437 by β-cyclodextrin

CD437 (6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid) is a novel synthetic retinoic acid derivative that has been shown to selectively induce apoptosis in human lung cancer cells. This compound, however, is limited in its application due to its low solubility in aqueous solutions. One technique for increasing the solubility and bioavailability of a cytotoxic agent is the formation of inclusion complexes with cyclodextrins. Herein, we report the formation and characterization of a 2:1 complex between β-cyclodextrin (β-CD) and CD437. It is shown that CD437 is a tight binder of β-CD with an overall association constant of 2.6 ± 0.6 × 10⁷ M⁻². In addition, we demonstrate (a) that β-CD-derived complexation enhances the aqueous solubility of CD437, and (b) that a significant increase in the toxicity of CD437 against a human lung adenocarcinoma cell line can be achieved by co-treatment with β-CD.     

Fast separation of bromelain by polyacrylic acid-bound iron oxide magnetic nanoparticles

The adsorption of bromelain from an aqueous solution by polyacrylic acid (PAA)-bound iron oxide magnetic nanoparticles was studied. The magnetic composite nanoparticles were shown to be efficient for the separation of bromelain. Except at pH <3, the adsorption of bromelain increased with the decrease in solution pH and reached almost 100% at pH 3–5. The adsorbed bromelain could be desorbed by the addition of KCl and complete desorption was achieved at pH 7 when [KCl]>0.6 M. The adsorption behaviour followed the Langmuir isotherm with a maximum adsorption amount of 0.476 mg/mg and a Langmuir adsorption equilibrium constant of 58.4 ml/mg at pH 4 and 0.1 M phosphate. In addition, it was notable that both the adsorption and desorption of bromelain were quite fast and could be completed in about 1 min due to the absence of internal diffusion resistance. Bromelain retained 87.4% activity after adsorption/desorption.     

Effect of Cyclodextrin Complexation on the Aqueous Solubility and Solubility/Dose Ratio of Praziquantel

Praziquantel (PZQ), the primary drug of choice in the treatment of schistosomiasis, is a highly lipophilic drug that possesses high permeability and low aqueous solubility and is, therefore, classified as a Class II drug according to the Biopharmaceutics Classification System (BCS). In this work, β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) were used in order to determine whether increasing the aqueous solubility of a drug by complexation with CDs, a BCS-Class II compound like PZQ could behave as BCS-Class I (highly soluble/highly permeable) drug. Phase solubility and the kneading and lyophilization techniques were used for inclusion complex preparation; solubility was determined by UV spectroscopy. The ability of the water soluble polymer polyvinylpyrolidone (PVP) to increase the complexation and solubilization efficiency of β-CD and HP-β-CD for PZQ was examined. Results showed significant improvement of PZQ solubility in the presence of both cyclodextrins but no additional effect in the presence of PVP. The solubility/dose ratios values of PZQ-cyclodextrin complexes calculated considering the low (150 mg) and the high dose (600 mg) of PZQ, used in practice, indicate that PZQ complexation with CDs may result in drug dosage forms that would behave as a BCS-Class I depending on the administered dose.     

Facile synthesis of metal-chelating magnetic nanoparticles by exploiting organophosphorus coupling

A new method is described for facile synthesis of metal-chelating magnetic nanoparticles by simply mixing iron oxide nanoparticles with a bifunctional organophosphorus compound, N-(phosphonomethyl)iminodiacetic acid (PM–IDA), in aqueous solution. On charging with nickel ions, the PM–IDA functionalized iron oxide nanoparticles exhibited high His-tag protein binding capacity (0.21 and 0.58 mg/mg for His-tagged green fluorescent protein and chloramphenicol acetyltransferase, respectively) and were successfully used to purify these proteins from bacterial cell extracts to high purity in a single step. Although other synthetic schemes for metal-chelating magnetic nanoparticles have been reported, the method described here is markedly simpler and involves only low-cost reagents.     

Synthesis and characterization of magnetic β-cyclodextrin-chitosan nanoparticles as nano-adsorbents for removal of methyl blue

A novel nano-adsorbent, β-cyclodextrin-chitosan (CDC) modified Fe(3)O(4) nanoparticles (CDCM) is fabricated for removal of methyl blue (MB) from aqueous solution by grafting CDC onto the magnetite surface. The characteristics results of FTIR, SEM and XRD show that CDC is grafted onto Fe(3)O(4) nanoparticles. The grafted CDC on the Fe(3)O(4) nanoparticles contributes to an enhancement of the adsorption capacity because of the strong abilities of CDCM, which includes the multiple hydroxyl, carboxyl groups, amino groups and the formation of an inclusion complex due to the β-CD molecules through host-guest interactions, to adsorb MB. The adsorption of MB onto CDCM is found to be dependent on pH and temperature. Adsorption equilibrium is achieved in 50 min and the adsorption kinetics of MB is found to follow a pseudo-second-order kinetic model. Equilibrium data for MB adsorption are fitted well by Langmuir isotherm model. The maximum adsorption capacity for MB is estimated to be 2.78 g/g at 30°C. The CDCM was stable and easily recovered. Moreover the adsorption capacity was about 90% of the initial saturation adsorption capacity after being used four times.     

The immuno-reactivity of polypseudorotaxane functionalized magnetic CDMNP-PEG-CD nanoparticles

pH-magnetic dual-responsive nanocomposites have been widely used in drug delivery and gene therapy. Recently, a polypseudorotaxane functionalized magnetic nanoparticle (MNP) was developed by synthesizing the magnetic nanoparticles with cyclodextrin (CD) molecules (CDMNP) via polyethylene glycol (PEG) (CDMNP-PEG-CD). The purpose of this study was to explore the antigenicity and immunogenicity of the nanoparticles in vivo prior to their further application explorations. Here, nanoparticles were assessed in vivo for retention, bio-distribution and immuno-reactivity. The results showed that, once administered intravenously, CDMNP-PEG-CD induced a temporary blood monocyte response and was cleared effectively from the body through the urine system in mice. The introduction of β-CD and PEG/β-CD polypseudorotaxane on SiO₂ magnetic nanoparticles (SOMNP) limited particle intramuscular dispersion after being injected into mouse gastrocnemius muscle (GN), which led to the prolonged local inflammation and muscle toxicity by CDMNP and CDMNP-PEG-CD. In addition, T cells were found to be more susceptible for β-CD–modified CDMNP; however, polypseudorotaxane modification partially attenuated β-CD–induced T cell response in the implanted muscle. Our results suggested that CDMNP-PEG-CD nanoparticles or the decomposition components have potential to prime antigen-presenting cells and to break the muscle autoimmune tolerance.     

Ultrasmall mixed ferrite colloids as multidimensional magnetic resonance imaging, cell labeling, and cell sorting agents

One area that has been overlooked in the evolution of magnetic nanoparticle technology is the possibility of introducing informational atoms into the iron oxide core of the coated colloid. Introduction of suitable atoms into the iron oxide core offers an opportunity to produce a quantifiable probe, thereby adding one or more dimensions to the magnetic colloid's informational status. Lanthanide-doped iron oxide nanoparticles have been synthesized to introduce informational atoms through the formation of colloidal mixed ferrites. These colloids are designated ultrasmall mixed ferrite iron oxides (USMIOs). USMIOs containing 5 mol % europium exhibit superparamagnetic behavior with an induced magnetization of 56 emu/g Fe at 1.5 T, a powder X-ray diffraction pattern congruent with magnetite, and R1 and R2 relaxivity values of 15.4 (mM s) (-1) and 33.9 (mM s) (-1), respectively, in aqueous solution at 37 degrees C and 0.47 T. USMIO can be detected by five physical methods, combining the magnetic resonance imaging (MRI) qualities of iron with the sensitive and quantitative detection of lanthanide metals by neutron activation analysis (NA), time-resolved fluorescence (TRF), X-ray fluorescence, along with detection by electron microscopy (EM). In addition to quantitative detection using neutron activation analysis, the presence of lanthanides in the iron oxide matrix confers attractive optical properties for long-term multilabeling studies with europium and terbium. These USMIOs offer high photostability, a narrow emission band, and a broad absorption band combining the high sensitivity of time-resolved fluorescence with the high spatial resolution of MRI. USMIO nanoparticles are prepared through modifications of traditional magnetite-based iron oxide colloid synthetic methods. A 5 mol % substitution of ferric iron with trivalent europium yielded a colloid with nearly identical magnetic, physical, and chemical characteristics to its magnetite colloid parent.     

Preparation and Physicochemical Properties of Catechin/β-cyclodextrin Inclusion Complex Nanoparticles

Nano-size catechin/β-cyclodextrin inclusion complex (CA/β-CD IC) with 1:1 molar ratio was obtained by cooling precipitation at 4 °C. Physicochemical properties of the CA/β-CD IC nanoparticles were characterized. Results of dynamic light scattering and SEM observation showed that CA/β-CD IC molecules underwent a process of assembling and shaping nano-size particles. In the range of 10–14 mM, the higher the concentration of β-CD aqueous solution, the faster the CA/β-CD IC nanoparticles form and the larger the size of the nanoparticles (195.2–438.6 nm). The total recovery, inclusion ratio and loading capacity of the CA/β-CD IC nanoparticles were determined. Results of FT-IR and DSC indicated that stability of CA was enhanced after it was embedded into β-CD cavity. XRD results showed that the strongest three diffraction peaks (located at 2θ = 10.6°, 12.4° and 19.6°) of the CA/β-CD IC nanoparticles was different from that (located at 2θ = 6.6°, 11.7° and 17.7°) of micro-size CA/β-CD IC and the nanoparticles obtained from higher concentration solution possessed higher crystallinity.

     

Intermolecular transglycosylating reaction of cyclodextrin glucanotransferase immobilized on capillary membrane

The intermolecular transglycosylating reaction of cyclodextrin glucanotransferase ([EC 2.4.1.19]; CGTase) immobilized on a capillary membrane was investigated using low molecular weight substrates such as cyclodextrin (CD), maltooligosaccharide (MOS), and a CD-MOS mixture. The immobilized CGTase catalyzed the conversion reaction of α-CD to β-CD and MOS or β-CD to α-CD and MOS within a short residence time. The conversion ratio increased as the amount of immobilized CGTase increased. The addition of glucose, maltose, and sucrose as acceptors in the substrate solution containing CD resulted in the acceleration of CD degradation compared with only CD substrate. Furthermore, the MOS substrate (degree of polymerization =2–6) was disproportionated with a conversion ratio exceeding 70% by the immobilized CGTase. These data demonstrate that immobilized CGTase can catalyze intermolecular transglycosylation between low molecular substrates in a few minutes by regulating the amount of immobilized enzyme and the residence time. This might contribute to our comprehension of CGTase-immobilized bioreactors for CD production as well as to the development of new glycosides through its excellent transglycosylation ability.     

Cultured human thymocytes lacking CD2 and CD11a/CD18 antigens are functional and adhere to endothelial cells via CD56 or CDw49d molecules.

The preferential growth of CD3-CD2-CD11a/CD18- thymocytes was obtained by stimulation of CD2-CD3- thymic cells with low doses of PMA (0.5 ng/ml) and subsequent culture in the presence of recombinant interleukin-2 (100 U/ml). After 2-3 weeks, CD3-CD2-CD11a/CD18- thymocytes represented 40-60% of the total proliferating cells. Highly purified CD3-CD2-CD11a/CD18- cell populations were obtained by depletion of the CD11a/CD18+ thymocytes by immunomagnetic beads. Moreover, these populations proliferated for 2-5 weeks and did not change their surface phenotype. It is of note that these cells, despite the lack of CD2 and CD11a/CD18 adhesion molecules, could bind to umbilical vein endothelial cells as efficiently as did CD3+CD2+CD11a/CD18+ thymocytes. Furthermore we demonstrate that (a) CD56 molecule is involved in the adhesion of CD3-CD2-CD11a/CD18- thymic cells, but not of peripheral CD3-CD56+ lymphocytes, to untreated or IFN-gamma- and/or TNF-alpha-treated endothelium, (b) anti-CDw49d mAb could inhibit the adhesion of this thymus-derived population to either IFN-gamma- or TNF-alpha-treated endothelial cells but not to untreated endothelium, and (c) CD56 antigen expressed by these cultured thymocytes has a sialic acid content different from that of peripheral lymphocytes. Indeed, isoelectrofocusing analysis showed that CD56 molecule expressed on CD3-CD2-CD11a/CD18- thymocytes displayed an isoelectric point (pI 5.0) different from that of CD56 antigen expressed by peripheral NK cells (pI 4.7 and 5.4). Further, we noted that CD56 antigen showed the same pI 5.8 after desialylation obtained using neuraminidase treatment. Finally, CD3-CD2-CD11a/CD18- thymocytes mobilized Ca2+ and released TNF-alpha and IFN-gamma after treatment with lectins.     

The aqueous solubility and thermal stability of α-lipoic acid are enhanced by cyclodextrin

We investigated the effects of various cyclodextrins (CDs) on the aqueous solubility and thermal stability of α-lipoic acid, a compound with low water solubility. α-CD, β-CD, and γ-CD had little effect on the aqueous solubility of α-lipoic acid. In contrast, 6-O-α-maltosyl-CDs increased it in a concentration-dependent manner, 6-O-α-maltosyl-β-CD enhancing solubility the most. The thermal stability of α-lipoic acid in the solid state was improved by the addition of G2-β-CD(?), a commercial product of 6-O-α-maltosyl-β-CD. The thermal stability of α-lipoic acid was also improved by the addition of β-CD. Analysis by differential scanning calorimetry showed that G2-β-CD(?), a mixture of maltosyl-β-CDs, and β-CD efficiently formed complexes with α-lipoic acid. These results suggest that the sizes and shapes of these β-CD compounds are compatible with complexation with α-lipoic acid. Moreover, both the formation of an aqueous complex with G2-β-CD(?) and an insoluble complex with β-CD increased the thermal stability of α-lipoic acid.     

Evaluation of the accessible inclusion sites in copolymer materials containing β-cyclodextrin

The accessible inclusion sites of insoluble copolymers containing β-cyclodextrin (β-CD) were studied in aqueous solutions by measuring the absorbance changes (decolourization) of phenolphthalein (phth) at pH 10.5. The various copolymers were reacted at different β-CD:crosslinker mole ratios with five individual types of crosslinker agents (epichlorohydrin (EP), sebacoyl chloride (SCL), terephthaloyl chloride (TCL), glutaraldehyde (GLU), and poly(acrylic) acid (PAA), respectively). The decolourization provided estimates of the 1:1 binding constants (K₁) for the β-CD monomer/phth complex. Comparable values of K₁ were measured for copolymer/phth complexes with highly accessible β-CD inclusion sites as compared with the 1:1 β-CD/phth complex. The surface accessibility of the β-CD inclusion binding sites for the polymers ranged from ∼10 to 72%. The observed variability of the inclusion sites was attributed to: (i) steric effects in the annular hydroxyl region of β-CD, (ii) the degree of crosslinking of the copolymer and (iii) the accessibility of the micropore sites within the copolymers. The Gibbs free energy (ΔG°) and site occupancy (θ) of phth adsorbed to the copolymer materials was estimated independently using the Sips isotherm model. The ΔG° values ranged between −27.6 and −30.9 kJ mol⁻¹ for the copolymers and are in close agreement with the value for the 1:1 β-CD/phth complexes (ΔG° = −27 kJ mol⁻¹) in aqueous solution.     

Mechanical grinding effect on thermodynamics and inclusion efficiency of loratadine-cyclodextrin inclusion complex formation

The interaction of poor water-soluble drug loratadine (LOR) with β-cyclodextrin (β-CD) or hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous or solid state was investigated. Mechanical grinding effect on the inclusion steps, thermodynamic kinetics and inclusion efficiency of inclusion complex formation of LOR with β-CD or HP-β-CD was quantitatively investigated by DSC and FT-IR microspectroscopy with curve-fitting analysis. The phase solubility profiles of LOR with β-CD and HP-β-CD were classified as A_L-type phase diagram. The grinding-induced reduction in LOR crystallinity in the presence of β-CD or HP-β-CD was found to be apparent zero-order kinetics. The inclusion efficiency of solid inclusion complex for LOR/β-CD or LOR/HP-β-CD was significantly correlated with the reduction in LOR crystallinity and the grinding time. The mechanism of inclusion complex formation for LOR/β-CD or LOR/HP-β-CD was proposed through the progressive reduction in LOR crystallinity, the promoted LOR amorphization, and molecular inclusion processes in the continuous energy input process of mechanical grinding.