Mei Mei Peng

Low-cost and eco-friendly green synthesis of silver nanoparticles using Prunus japonica (Rosaceae) leaf extract and their antibacterial, antioxidant properties

Abstract Low cost and eco-friendly green synthesis of silver nanoparticles (AgNPs) from silver nitrate (AgNO3) using Prunus japonica leaves extract as reducing agent by a simple method at room temperature. The biosynthesized nanoparticles (NPs) were characterized by UV-Vis, tunneling electron microscopy (HR-TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectrophotometer (EDAX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). In UV-Vis spectroscopy results, the λmax was observed at 441 nm. The AgNPs synthesized were spherical, hexagonal, and irregular in shapes. The EDAX and XRD spectrum confirmed the presence of silver ions and crystalline nature of synthesized AgNPs. FTIR showed the functional groups such as C = O, N–H and C–N groups involved in the reduction of Ag+ to Ag. 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was performed and it showed the percentage inhibition in concentration-dependent manner. The synthesized AgNPs showed antibacterial activity against Escherichia coli, Proteus vulgaris, Staphylococcus aureus and Bacillus cereus to different extents and the higher activity was observed in Proteus vulgaris.

Novel microporous hypercross-linked conjugated quinonoid chromophores with broad light absorption and CO2 sorption characteristics

We have discovered formation of hypercross-linked conjugated quinonoid chromophores (polymers) with broad light absorption characteristics during cross-linking of aromatic monomers, such as benzene, naphthalene, anthracene, phenanthrene and 1,3,5-trimethyl benzene with 1,3,5-trioxane in the presence of an FeCl3 catalyst. The para or ortho –CH2 groups that bridge aromatic monomers were dehydrogenated during polymerization to form the quinonoids. The quinonoid chromophores were confirmed by their DRS-UV Vis and FTIR spectra. We have also discovered similar such quinonoid chromophores in the hypercross-linked polymers of aromatic monomers, reported from 1970 onwards by different research groups. The polymers were synthesized by similar experiments with an FeCl3 catalyst, and brown colored. As all the polymers bear low band gaps, they strongly absorb light covering the wavelength range of 1000 to 200 nm. Most of the hypercross-linked polymer matrices carry microporous spheres of about 1 to 5 μm diameter and showed 6–7% CO2 sorption. The polymers with their low band gaps will inspire research on semiconductors, solar cell devices, UV stabilizers/absorbers and infrared absorbers/detectors, molecular sensors and academic study.

Chitosan cocrystals embedded alginate beads for enhancing the solubility and bioavailability of aceclofenac.

Enhanced oral bioavailability of aceclofenac has been achieved using chitosan cocrystals of aceclofenac and its entrapment into alginate matrix a super saturated drug delivery system (SDDS). Prepared SDDS were evaluated by various physiochemical and pharmacological methods. The result revealed that the primary cocrystals enhanced the solubility of the drug and the thick gelled polymer matrix that formed from swelling of calcium alginate beads makes it to release the drug in continuous and sustained manner by supersaturated drug diffusion. The Cmax, Tmax and relative bioavailability for aceclofenac cocrystal and aceclofenac SDDS were 2.06±0.42 μg/ml, 1 h, 159.72±10.84 and 2.01 μg/ml, 1 h, 352.76±12.91, respectively. Anti-inflammatory activity of aceclofenac was significantly improved with the SDDS. With respect to the results, it revealed that the SDDS described herein might be a promising tool for the oral sustained release of aceclofenac and likely for that of various other poorly soluble drugs.

Chitosan-HPMC-blended microspheres as a vaccine carrier for the delivery of tetanus toxoid

The purpose of this research was to develop a suitable and alternate adjuvant for the tetanus toxoid (TT) vaccine that induces long term immunity after a single-dose immunization. In our study, the preformulation studies were carried out by using different ratios (7/3, 8/2, and 9/1) of chitosan–hydroxypropyl methylcellulose (HPMC)-blended empty microspheres. Moreover, TT was stabilized with heparin (at heparin concentrations of 1%, 2%, 3%, and 4% w/v) and encapsulated in ideal chitosan – HPMC (CHBMS) microspheres, by the water-in-oil-in-water (W/O/W) multiple emulsion method. The vaccine entrapment and the in vitro release efficiency of the CHBMS was evaluated for a period of 90 days. The release of antigens from the microspheres was determined by ELISA. Antigen integrity was investigated by SDS-PAGE. From the optimization studies, it was found that a chitosan/HPMC ratio of 8/2 produced a good yield, with microspheres that were spherical, regular and uniformly-sized. In the CHBMS, a heparin concentration of 3% w/v resulted in well-sustained antigen delivery for a period of 90 days. It was found that the characteristics of initial release could be observed in 2 days, followed by a constant release, and an almost 100% complete release in 90 days. From the in vitro release characteristics, the ideal batch of CHBMS (3% w/v heparin) was evaluated for in vivo studies by the antibody induction method. The antibody levels were measured for different combinations for the period of 9 months, and finally, with a second booster dose after 1 year. In conclusion, it was observed that CHBMS (combination-1) resulted in the antibody level of 4.5 IU/mL of guinea pig serum, and the level was 3.5 IU/mL for the Central Research Institutes alum-adsorbed tetanus toxoid (CRITT) (combination 2), after 1 year, with a second booster dose. This novel approach of using CHBMS may have potential advantages for single-step immunization with vaccines.

A new strategy to synthesize hypercross-linked conjugated polystyrene and its application towards CO2 sorption

Polystyrene is cross-linked to generate micropores for sorption applications. Herein, we report, hypercross-linking of polystyrene in the presence of Friedel-Crafts catalyst, FeCl3 without a cross-linker. For comparison, polystyrene was also hypercross-linked with a cross-linker, dimethoxy methane with the same catalyst. The cross-linking and de-hydrogenation of cross-links to quinonoid formation were confirmed by FT-IR and 13C-NMR techniques. The hyper cross-linked polymers (HCPs) were also characterized by TGA, DRS-UV, SEM, Raman, BET and CO2 sorption techniques. All the HCPs showed a maximum of 5 weight % CO2 sorption at 25 oC and 1 atm. The same polymers could also be applied for the sorption of other air pollutants.

Microporous Hypercross-linked Conjugated Quinonoid Chromophores of Anthracene: Novel Polymers for CO 2 Adsorption

Microporous hypercross-linked conjugated quinonoid chromophores represent a novel class of amorphous polymers, synthesized by the reaction of anthracene with dimethoxy methane in the presence of FeCl3 catalyst. Their N2 adsorption isotherms confirm their microporous nature. Diffuse reflectance UV-Visible (DRS UV-Vis) spectroscopy confirms their matrix built with the conjugated quinonoids by their broad light absorption characteristics extending from 1000 nm to 200 nm with the absorbance maximum close to 400 nm. The catalyst cross-linked anthracene with -CH2- bridges and subsequently dehydrogenating them to form quinonoids. Their Fourier transform infrared (FTIR) spectra showed their characteristic quinonoid vibrations between 1600 and 1700 cm−1. The synthesis of polymers was carried out at 30, 40, 50, 60, 70 and 80 °C, but the quinonoid content of the polymer obtained at 80 °C was higher than that of the others. Their scanning electron microscopy (SEM) images showed microspheres of 1 to 5 μm size built with tiny particles. Their surfaces were not smooth. The polymer synthesized at 80 °C showed 5.1 wt% CO2 sorption at 25 °C and 0.1 MPa, but when it was recross-linked, the CO2 sorption increased to 8 wt%. Hence, hypercross-linked conjugated quinonoid chromophores of anthracene are good for sorption of CO2.

Drug Release Evaluation of Mesoporous TiO2: A Nano Carrier for Duloxetine

Mesoporous TiO2 was synthesized solvothermally, but its XRD pattern proved little randomly arranged mesopores. Its DRS-UV-Vis spectrum showed characteristic band gap excitation just below 400 nm and oxygen to metal charge transfer close to 250 nm. It was loaded with the model drug duloxetine (DX) by wet method. Locked-in drug within the mesopores of TiO2 was confirmed by XRD, DRS-UV-Vis and FT-IR techniques. About 11% loading of drug was verified by UV-Vis spectroscopy. The study of drug release showed two stages of burst release between 0 and 12 h and beyond that slow extended release of DX occurred. The total burst release was equal to 20%, and even at the end of 40 h the total release was equal to 90%. Hence, mesoporous TiO2 was established as a viable, biocompatible DX reservoir for its controlled release. The same mesoporous TiO2 could be convenient for the release of potentially toxic drugs which require small and extended dose.

ESTIMATION OF MELOXICAM IN HUMAN PLASMA BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY (LC-MS/MS)

A simple, rapid, selective, and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for estimation of meloxicam (MX) in human plasma using hypersil gold column (C18, 10 cm x 4.6 mm i.d, 5 µm), methanol: Milli-Q-water: formic acid (70:30:1 v/v) as mobile phase and piroxicam (PX) as an internal standard. Samples were extracted using liquid–liquid extraction. The concentration of MX was determined by isocratic HPLC-MS/MS in multiple reaction monitoring (MRM) mode. The mass transition ion-pair for MX was m/z 352.0→115.0 and 331.8 → 94.8 for PX. The proposed method was linear in the range of 10.090–3002.964 ng/mL for MX. The intra- and inter-run precision values are within 12.82% for MX at a lower limit of quantitation (LLOQ) level. The overall recovery for PX was 60.81% with a total runtime of 3 min.

Comparative antioxidant and antimycobacterial activities of Opuntia ficus-indica fruit extracts from summer and rainy seasons

The antioxidant and antimycobacterial activities of Opuntia ficus-indica (OFI) fruit extracts were evaluated according to seasonal cultivation. The antioxidant activities of OFI extracts were assessed by different in vitro methods and the total phenolic and flavonoid contents were also examined. The antimycobacterial activity was measured against Mycobacterium tuberculosis strain H37Rv (ATCC 27294) by the microplate alamar blue assay method. In the antioxidant assay, methanol extracts of OFI in summer showed the highest antioxidant activity of all tested methods, and the lowest IC50 was observed in the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. Pearsons correlation coefficient was evaluated and the results from the extracts of summer and rainy season OFI were significantly correlated with the total phenolic and flavonoid contents. The methanol extracts of OFI in summer showed a high level of antimycobacterial activity against M. tuberculosis H37Rv, with a minimum inhibitory concentration of 50 µg ml−1. The results of this study suggest that OFI could be an important source of antioxidants as well as antimycobacterials against M. tuberculosis.

CO2 Adsorption of Metal Organic Framework Material Cu-BTC via Different Preparation Routes

In this work, Cu3(BTC)2 (Cu-BTC) metal organic framework (MOF), also known as HKUST-1, was prepared by 3 different synthetic route. The synthesized Cu-BTC materials were characterized by powder X-ray diffraction (XRD) for phase structure, scanning electron microscopy (SEM) for crystal structure, thermogravimetric analysis (TGA) for thermal stability, and nitrogen adsorption-desorption for pore textural structure. The results showed that the sample synthesized by microwave method has the high surface area and pore volume of 1721 m2g− 1 and 0.7424 cm3g− 1, respectively. Among the three synthetic methods, the sample synthesized by microwave method exhibited a CO2 uptake of 23.3% at 25 °C and ambient pressure.