Synthesis and controlled curcumin supramolecular complex release from pH-sensitive modified gum-arabic-based hydrogelsGerola, Adriana P.; Silva, Danielle C.; Jesus, Sandra; Carvalho, Rui A.; Rubira, Adley F.; Muniz, Edvani C.; Borges, Olga; Valente, Artur J. M.
doi: 10.1039/c5ra14331dpmid: N/A
Curcumin (CUR) is a polyphenolic compound including a beta-diketone moiety, which is associated with numerous pharmacological activities, but applications are limited due to its low water solubility. Thus, in this work some inclusion complexes of CUR with alpha-cyclodextrin (α-CD) and beta-cyclodextrin (β-CD) were prepared using different host : guest proportions to improve drug solubilization in biological fluids. The formation of these complexes was confirmed by 1H NMR and thermogravimetric analysis. The stoichiometries of the CUR/α-CD and CUR/β-CD complexes were 1 : 1 and 1 : 2 and the association constants were 344 mol−1 L and 7.2 × 107 mol−2 L2 for α-CD and β-CD, respectively. The major stability of the CUR/β-CD complex is justified by an inclusion of the aromatic ring inside the CD cavity, whilst in the case of α-CD-complexes the interactions occur via H-bridges, showing the latter complexes’ slow exchange on the NMR time-scale. Even so, the solubility of curcumin complexes is clearly controlled by the solubility of CDs, showing the highest solubility for CUR/α-CD complexes. Hydrogels of modified gum arabic containing CUR/α-CD (1 : 4) were obtained and used for controlled release of CUR in simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The kinetics of release was pH-responsive and the percentage of CUR released was ca. 97% in SIF and 6.7% in SGF. For the toxicity studies on undifferentiated Caco-2 cells, IC50s of 63.4 ± 14.4 μg mL−1 and 85.2 ± 14.9 μg mL−1 for CUR and CUR/α-CD (1 : 4), respectively, were obtained. The toxicity of these samples on differentiated Caco-2 cells was lower than on undifferentiated cells. Additionally, the CUR incorporated into hydrogels showed no toxic effects on differentiated and undifferentiated Caco-2 cells, indicating the pharmaceutical potential of three-dimensional matrices of GAm for controlled release of CUR complexed with cyclodextrin.
Preparation and microwave absorption properties of multi-walled carbon nanotubes decorated with Ni-doped SnO2 nanocrystalsLin, Ling; Xing, Honglong; Shu, Ruiwen; Wang, Lei; Ji, Xiaoli; Tan, Dexin; Gan, Ying
doi: 10.1039/c5ra17303epmid: N/A
In this work, Ni-doped SnO2@MWCNTs composites were synthesized by a facile one-step hydrothermal method. The morphology and structure of the as-prepared composites were characterized by XRD, SEM, TEM, XPS, FT-IR and Raman. It was found that the SnO2 nanoparticles were successfully anchored on the MWCNTs with a diameter of 3–5 nm and Ni2+ was successfully doped into the SnO2@MWCNTs. Moreover, the effect of the doped Ni molar percentage on the electromagnetic parameters and microwave absorbing properties of the Ni-doped SnO2@MWCNTs composites was studied in the 2–18 GHz frequency range. The results showed that the composites with 28.2% doped Ni content exhibited the best microwave absorbing properties. The maximum RL reached −39.2 dB at 8.2 GHz with a thickness of 2.5 mm, and the bandwidth of RL lower than −10 dB was 3.6 GHz (from 12.6 to 16.2 GHz) with a thickness of 1.5 mm. The excellent microwave absorbing properties could be attributed to the good impedance match, Debye relaxation, interfacial polarization and high conductivity of the MWCNTs component. It was believed that the Ni-doped SnO2@MWCNTs composites could be used as a new type of microwave absorbing materials against electromagnetic pollution.
A new heterocyclic skeleton with highly tunable absorption/emission wavelength via H-bondingTomashenko, Olesya A.; Khlebnikov, Alexander F.; Mosiagin, Ivan P.; Novikov, Mikhail S.; Grachova, Elena V.; Shakirova, Julia R.; Tunik, Sergey P.
doi: 10.1039/c5ra17755cpmid: N/A
A new heterocyclic system, pyrido[2,1-a]pyrrolo[3,2-c]isoquinoline, was synthesized via Pd-catalyzed intramolecular cyclization of 1-[1-benzyl-2-(2-bromophenyl)-1H-pyrrol-3-yl]pyridin-1-ium bromides. The heterocycles obtained display stimuli responsive fluorescence in solution depending on the nature of the solvent. The strongest blue shift of the emission maxima and growth in luminescence intensity was observed in protic solvents and upon addition of proton donors to solutions of compounds in aprotic solvents. The effect of proton donors on emission characteristics was explained by DFT calculations in terms of H-complex formation with the nucleophilic centres of the molecular skeleton.
An elegant synthesis of chitosan grafted hydrotalcite nano-bio composite material and its effective catalysis for solvent-free synthesis of jasminaldehydeAdwani, Jacky H.; Khan, Noor-ul H.; Shukla, Ram S.
doi: 10.1039/c5ra16927epmid: N/A
A novel nano-bio composite of chitosan and a layered double hydroxide was elegantly synthesized by a co-precipitation method. The nano-bio composite material (CMA) was thoroughly characterized by FTIR, TGA, XRD, SEM and TEM. The composite material CMA showed efficient catalytic activity for selective synthesis of jasminaldehyde under solvent free conditions by condensation of benzaldehyde and 1-heptanal. In typical employed conditions, 39.5 mmol benzaldehyde, 7.9 mmol 1-heptanal, 100 mg catalyst, 160 °C and 700 rpm, a maximum selectivity of 89% with 99% conversion was obtained. The investigations were performed in detail as a function of the amount of catalyst, temperature and molar ratio of 1-heptanal to benzaldehyde to observe the effect of these reaction parameters on the conversion, selectivity and rate of the formation of the condensation products. All these parameters were found to influence the performance of the catalyst. The initial rate of formation of jasminaldehyde was found to be ∼20% more than the rates with individual chitosan and hydrotalcite. The rate of formation of 2-pentyl-2-nonenal with CMA was found to be lower in comparison with individual catalysts, chitosan and hydrotalcite. The determined activation energy was 16.3 kJ mol−1. The catalyst was elegantly separated, washed and dried, and found to be effectively recycled six times without any substantial loss in its activity.
Application of aziridinium ring opening for preparation of optically active diamine and triamine analogues: highly efficient synthesis and evaluation of DTPA-based MRI contrast enhancement agentsSun, Xiang; Chen, Yunwei; Wu, Ningjie; Kang, Chi Soo; Song, Hyun A.; Jin, Shengnan; Fu, Yao; Bryant, Henry; Frank, Joseph A.; Chong, Hyun-Soon
doi: 10.1039/c5ra11306gpmid: 26989478
Ring opening of aziridinium ions with nitrogen nucleophiles was applied to the highly efficient synthesis of optically active vicinal diamines and diethylene triamine pentaacetic acid (DTPA) analogues as potential magnetic resonance imaging (MRI) contrast enhancement agents. The synthetic method features a column-free isolation of the regiospecific and stereospecific nucleophilic substitution products of enantiomerically enriched aziridinium ions in excellent yield.
Synthesis, micellization, and thermally-induced macroscopic micelle aggregation of poly(vinyl chloride)-g-poly(N-isopropylacrylamide) amphiphilic copolymerLiu, Keyong; Pan, Pengju; Bao, Yongzhong
doi: 10.1039/c5ra16726dpmid: N/A
A series of poly(vinyl chloride)-g-poly(N-isopropylacrylamide) (PVC-g-PNIPAM) amphiphilic copolymers with different graft lengths and densities were synthesized via the single electron transfer-living radical polymerization (SET-LRP) of NIPAM using poly(vinyl chloride-co-allyl α-bromoisobutyrate) as macroinitiator. The living nature of SET-LRP grafting copolymerization was verified by the kinetics study and narrow molecular weight distribution of PNIPAM grafts. The chemical structure, micellisation, and thermally-induced multistep aggregation of PVC-g-PNIPAMs were investigated. PVC-g-PNIPAMs form micelles comprised of a PVC core and PNIPAM corona in water at room temperature. These micelles are thermoresponsive and show a lower critical solution temperature (LCST). The micelle size and LCST of PVC-g-PNIPAM increase with increasing the graft density and length of PNIPAM. PVC-g-PNIPAM exhibits a very unique aggregation behavior above its LCST and forms a three-dimensional macroscopic aggregate with a well-defined and tunable shape at an extremely low concentration (∼0.1 wt%). The aggregate shrinks to a more compact structure with the further increase of temperature. Higher copolymer concentration, longer graft length, and lower graft density are favorable for the macroscopic micelle aggregation of PVC-g-PNIPAMs. A self-standing and superporous PVC-g-PNIPAM material having an extremely low density of ∼0.01 g cm−3 and a high porosity of >99% is attained after freeze-drying the micelle aggregate.
Electrochemical fabrication of gold nanoparticles decorated on activated fullerene C60: an enhanced sensing platform for trace level detection of toxic hydrazine in water samplesPalanisamy, Selvakumar; Thirumalraj, Balamurugan; Chen, Shen-Ming
doi: 10.1039/c5ra17197kpmid: N/A
A novel and highly sensitive amperometric hydrazine sensor was fabricated using gold nanoparticles (AuNPs) decorated on activated fullerene C60 (AC60) modified screen printed carbon electrode (SPCE). An electrochemical method was used for the fabrication of the AC60–AuNPs modified SPCE which was characterized by scanning electron microscopy and elemental analysis. The fabricated AC60–AuNPs modified SPCE showed an enhanced electrocatalytic activity towards hydrazine over that of other modified SPCEs. Furthermore, the detection potential of hydrazine was notably lower (0.161 V) at the AuNPs decorated AC60 modified SPCE than AuNPs decorated bare (0.208 V) and C60 (0.186 V) modified SPCEs. Under optimum conditions, the amperometric response of the sensor was linear over the hydrazine concentrations from 0.13 μM to 1.21 mM with a fast response time of 1.3 s. In addition, the proposed sensor showed the lowest limit of detection (LOD) of 0.039 μM, with a high sensitivity of 0.583 μA μM−1 cm−2. The sensor also holds its high selectivity in the presence of common metal ions and biologically active interfering species. In addition, the practicality of the fabricated sensor in tap water samples is comparable with those detected by the HPLC method.
Fulleropyrrolidines derived from dioxa- and trioxaalkyl-tethered diglycinesKop, Tatjana; Bjelaković, Mira; Đorđević, Jelena; Žekić, Andrijana; Milić, Dragana
doi: 10.1039/c5ra17392bpmid: N/A
Two different α,ω-diglicynes linked by linear polyoxaalkyl chains in the presence of formaldehyde underwent Prato reaction to the fullerene C60. The shorter linker templated formation of only cis-bisadducts, while the longer one afforded a mixture of four bisadducts (all cis and the equatorial) and difullerene dumbbell compound. Their structures were confirmed by the extensive analysis of the spectral data and molecular symmetry, as well. All compounds expressed an ability to arrange into hierarchically ordered supramolecular aggregates, the form of which depended both on the addition pattern and the spacer structure. The attenuated electron-accepting affinity, examined by cyclic voltammetry was in agreement with diminished delocalization of the π-electronic system. In addition, all compounds exerted a notable radical scavenging activity.