Nanoceria-modified platinum supported on hierarchical zeolites for selective alcohol oxidation

The highly selective oxidation of alcohols to aldehydes has been achieved due to the synergic effect of Pt and CeO₂ supported on hierarchical zeolites. The combination of Pt and CeO₂ strongly enhances the catalytic performance of the oxidation of benzyl alcohol to benzaldehyde with respect to the isolated materials. In addition, the hierarchical zeolite not only increases the fraction of exposed active sites because of its high surface area that can prevent the aggregation of Pt and CeO₂ nanoparticles, but also affects the oxidation state of cerium. The presence of a high content of trivalent Ce species (Ce³⁺) on the hierarchical zeolite benefits the oxidation reaction, eventually leading to almost 100% yield of an aldehyde product. Moreover, the catalytic performance can be further improved by the easily tunable Si to Al ratio of zeolite catalysts.

Illustration of Pt/CeO₂ supported on hierarchical zeolites promoting the highly selective oxidation of benzyl alcohol to benzaldehyde.     

Repellent activity of herbal essential oils against Aedes aegypti (Linn.) and Culex quinquefasciatus (Say.)

Objective

To determine the mosquito repellent activity of herbal essential oils against female Aedes aegypti and Culex quinquefasciatus.

Methods

On a volunteer''s forearm, 0.1 mL of each essential oil was applied to 3 cm×10 cm of exposed skin. The protection time was recorded for 3 min after every 30 min.

Results

Essential oil from clove oil in olive oil and in coconut oil gave the longest lasting period of 76.50 min and 96.00 min respectively against Aedes aegypti. The citronella grass oil in olive oil, citronella grass oil in coconut oil and lemongrass oil in coconut oil exhibited protection against Culex quinquefasciatus at 165.00, 105.00, and 112.50 min respectively.

Conclusions

The results clearly indicated that clove, citronella and lemongrass oil were the most promising for repellency against mosquito species. These oils could be used to develop a new formulation to control mosquitoes.     

Enhanced Diagnosis of Pneumococcal Bacteremia Using Antigen- and Molecular-Based Tools on Blood Specimens in Mali and Thailand: A Prospective Surveillance Study

Prior antibiotic use, contamination, limited blood volume, and processing delays reduce yield of blood cultures for detection of Streptococcus pneumoniae. We performed immunochromatographic testing (ICT) on broth from incubated blood culture bottles and real-time lytA polymerase chain reaction (PCR) on broth and whole blood and compared findings to blood culture in patients with suspected bacteremia. We selected 383 patients in Mali and 586 patients in Thailand based on their blood culture results: 75 and 31 were positive for pneumococcus, 100 and 162 were positive for other pathogens, and 208 and 403 were blood culture negative, respectively. ICT and PCR of blood culture broth were at least 87% sensitive and 97% specific compared with blood culture; whole blood PCR was 75–88% sensitive and 96–100% specific. Pneumococcal yields in children < 5 years of age increased from 2.9% to 10.7% in Mali with > 99% of additional cases detected by whole blood PCR, and from 0.07% to 5.1% in Thailand with two-thirds of additional cases identified by ICT. Compared with blood culture, ICT and lytA PCR on cultured broth were highly sensitive and specific but their ability to improve pneumococcal identification varied by site. Further studies of these tools are needed before widespread implementation.     

HEC-cysteamine conjugates: influence of degree of thiolation on efflux pump inhibitory and permeation enhancing properties

Within the present study hydroxyethyl cellulose-cysteamine conjugates are investigated regarding biocompatibility, in situ gelling, permeation enhancing and efflux pump inhibitory properties. For this purpose, a series of concentrations of sodium periodate was prepared to oxidize HEC leading to ring opening of glucose subunits. The resulting polymers showing varying degrees of oxidation (DO) were then conjugated with cysteamine stabilized via reductive amination. Consequently, HEC-cysteamine conjugates with increasing degree in thiolation were obtained. Since the conjugates are positively charged, potency of cytotoxicity was tested by resazurin assay. In situ gelling properties of the conjugates were studied to investigate change of their viscosity due to inter- and/or intramolecular crosslinking via disulfide bonds. The influence of the presence of the conjugates on transport of rhodamine 123 and fluoresceinisothiocyanate-dextran 4 (FD4) representing model compounds for P-glycoprotein (P-gp) inhibition and permeation enhancing studies, respectively, across Caco-2 cell monolayers was determined. The conjugates showed a degree of thiolation in the range of 316-2158 μmol/g. Within 30 min, dynamic viscosity of the conjugate with the lowest degree of thiolation 0.5% (m/v) increased up to 300-fold. The conjugates showed a degree of thiolation-dependent increase in cytotoxicity but they all were found comparatively low cytotoxic. The addition of the conjugate with thiol group content of 1670 μmol/g resulted in the highest improvement in the transport of both rhodamine 123 and FD4 as compared to buffer control. Accordingly, the degree of thiolation strongly influences the properties of the conjugates and the modulation of the degree of thiolation could be exploited for development of various drug delivery systems.     

Synergistic effects of conjugating cell penetrating peptides and thiomers on non-viral transfection efficiency

Nanoparticles generated by complex coacervation of plasmid DNA (pDNA) and modified chitosans namely chitosan-thioglycolic acid (TGA) conjugate and chitosan-HIV-1 Tat peptide conjugate were evaluated as gene delivery systems. In order to optimize transfection efficiency, chitosan-HIV-1 Tat peptide conjugate was combined with chitosan-TGA before its complexation with pDNA. Particle size and zeta potential measurements were performed to characterize the generated nanoparticles. The nanoparticles transfection efficiencies were assessed by exploitation of the green fluorescent protein (GFP) reporter gene. HEK293 cells were incubated for 24 h with the nanoparticles and the GFP positive cells were observed by fluorescence microscopy. The nanoparticles in the size range of 200-300 nm could transfect HEK293 cells as a model cell line with different transfection efficiencies. Unlike chitosan-TGA, chitosan-HIV-1 Tat peptide led to increased zeta potential of nanoparticles as compared to unmodified chitosan. The transfection efficiency of the nanoparticles generated by combination of chitosan-HIV-1 Tat peptide with chitosan-TGA was comparatively higher than that of the nanoparticles generated by either chitosan-TGA or the combination of chitosan-HIV-1 Tat peptide with unmodified chitosan. After 72 h of incubation, the combination of chitosan-HIV-1 Tat peptide with chitosan-TGA was found to be 7.12- and 67.37 times more efficient than unmodified chitosan and pDNA alone, respectively and showed a synergistic effect in transfection of pDNA into the cells. Moreover, none of the nanoparticles showed any severe cytotoxicity. Accordingly, this strategy might result in a potent carrier for gene delivery.     

Distribution of thiolated mucoadhesive nanoparticles on intestinal mucosa

It was the aim of the present study to evaluate and compare the distribution of thiolated mucoadhesive anionic poly(acrylic acid) (PAA) and cationic chitosan (CS) nanoparticles on intestinal mucosa. Modifications of these polymers were achieved by conjugation with cysteine (PAA-Cys) and 2-iminothiolane (CS-TBA). Nanoparticles (NP) were prepared by ionic gelation and labelled with the strong hydrophilic fluorescent dye Alexa Fluor 488 (AF 488) and hydrophobic fluorescein diacetate (FDA). Unmodified and modified CS and PAA NP were examined in vitro in terms of their mucoadhesive and mucus penetrating properties on the mucosa of rat small intestine. To investigate the transport of NP across the mucus layer, their diffusion behaviour through natural porcine intestinal mucus was studied through a new diffusion method developed by our group. Lyophilised particles displayed 526 μmol/g (CS) and 513 μmol/g (PAA) of free thiol groups and a zeta potential of 20 mV (CS) and -14 mV for PAA NP. Nanoparticle distribution on rat intestine suggested that mucoadhesion of thiolated NP is higher than the diffusion into the intestinal mucosa. Modified particles displayed more than a 6-fold increase in mucoadhesion compared to unmodified ones. The rank order with regard to mucoadhesion of all particles was: CS-TBA>PAA-Cys>CS>PAA, whereas CS-TBA showed 2-fold higher mucoadhesive properties compared to PAA-Cys NP. Diffusion through intestinal mucus was much higher for unmodified than for thiolated as well as for anionic compared to cationic particles. Overall, it was shown that thiolated particles of both anionic and cationic polymers have improved mucoadhesive properties and could be promising carriers for mucosal drug delivery.     

In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of oxidizing agents

The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four oxidizing agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any oxidizing agents became gel within 40 min. In contrast, when the oxidizing agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p < 0.05) raising compared to the negative control. According to these results, chitosan-TGA/oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.