Ayman Karam

Rational design of sugar-based-surfactant combined catalysts for promoting glycerol as a solvent.

Thumbnail image of graphical abstract A sugary treat: Here we report the great efficiency of sugar-based-surfactant combined catalysts for conducting selective base-catalyzed organic reactions in glycerol. Close control of the reaction selectivity was successfully obtained owing to the formation of catalytic hydrophobic pockets in glycerol (see figure). The advantages of our catalytic processes and its similarities with catalysis in water are also highlighted.

Significant enhancement on selectivity in silica supported sulfonic acids catalyzed reactions

Thanks to strong hydrophilic interactions between reaction products and the catalyst surface, mesoporous silica supported sulfonic sites were found to be much more selective than homogeneous and common solid acid catalysts.

Selective and Catalyst-free Oxidation of D-Glucose to D-Glucuronic acid induced by High-Frequency Ultrasound

This systematic experimental investigation reveals that high-frequency ultrasound irradiation (550 kHz) induced oxidation of D-glucose to glucuronic acid in excellent yield without assistance of any (bio)catalyst. Oxidation is induced thanks to the in situ production of radical species in water. Experiments show that the dissolved gases play an important role in governing the nature of generated radical species and thus the selectivity for glucuronic acid. Importantly, this process yields glucuronic acid instead of glucuronate salt typically obtained via conventional (bio)catalyst routes, which is of huge interest in respect of downstream processing. Investigations using disaccharides revealed that radicals generated by high frequency ultrasound were also capable of promoting tandem hydrolysis/oxidation reactions.

Effect of non-cross-linked calcium on characteristics, swelling behaviour, drug release and mucoadhesiveness of calcium alginate beads

In this study, ibuprofen-loaded calcium alginate beads (CABs) with varying amounts of non-cross-linked calcium (NCL-Ca) were prepared using different washing methods. The influence of NCL-Ca on beads properties was investigated. Increasing the number or duration of washes led to significant decreases in the amount of NCL-Ca whereas the impact of the volume of washes was not significant. Approximately 70% of the initial amount of Ca(2+) was NCL-Ca which was removable by washing while only 30% was cross-linked (CL-Ca). Ca(2+) release from the CABs was bimodal; NCL-Ca was burst-released followed by a slower release of CL-Ca. Washing methods and the amount of NCL-Ca had significant influences on the encapsulation efficiency, beads weight, beads swelling, drug release profile and the mucoadhesiveness of CABs. This study highlighted the importance of washing methods and the amount of NCL-Ca to establish CABs properties and understand their behaviour in the simulated intestinal fluids (SIFs).

Conversion of Cellulose into Amphiphilic Alkyl Glycosides Catalyzed by Aquivion, a Perfluorosulfonic Acid Polymer

The perfluorosulfonic acid (PFSA) Aquivion PW98 is an amphiphilic solid superacid which is shown to catalyze the conversion of cellulose into amphiphilic alkyl glycosides (AAGs) in 85 % yield (with 97 % selectivity). The process involves a mechanocatalytic depolymerization of cellulose followed by a direct glycosylation with n-dodecanol. In comparison to H2 SO4 and solid acid catalysts commonly employed in cellulose processing, Aquivion PFSA PW98 is not only recyclable but also exhibits superior catalytic performances in terms of yield, selectivity, and reactor productivity.

Efficient approach to enhance drug solubility by particle engineering of bovine serum albumin

The aim of this study was to investigate the use of bovine serum albumin (BSA) as a solubility enhancer for indometacin (IND) as a model drug. IND-BSA solid dispersions were prepared by both spray drying and freeze drying techniques using IND:BSA solution (20:1 Molar Ratio (MR)) and IND:BSA suspension (100:1 MR). The solid state of IND in solid dispersions was characterised by SEM, DSC and XRD. The aqueous solubility of IND in the presence of increased amounts of BSA was evaluated. Additionally, IND dissolution and release profiles were evaluated. IND in solid dispersions with BSA showed significantly higher solubility in water than that of the physical mixture of both. Enhancement factors of 24,000 and 100,000 were obtained for the solid dispersion formulated in 20:1 MR and 100:1 MR, respectively. Dissolution studies in-vitro indicated a significant increase in the dissolution rate of IND from solid dispersions compared to that of the free drug, with almost 95% of the drug dissolved in the first 5min. Furthermore, an immediate release of IND from BSA solid dispersions was shown. The potential use of albumin as solubility enhancer for poorly soluble drugs, particularly, for immediate release volume-limited dosage forms is reported.

The use of albumin solid dispersion to enhance the solubility of unionizable drugs

Abstract In this study, solid dispersions of prednisolone (PRD) and bovine serum albumin (BSA) were prepared by spray drying and freeze drying methods using a PRD:BSA solution [20:1 molar ratio (MR)]. PRD-BSA dispersed mixtures were characterized by scanning electron microscopy (SEM), and powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). PRD-BSA physical and dispersed mixtures showed significantly higher solubility in water than that of unprocessed drug. Enhancement factor of six was obtained in both physical mixture and solid dispersion solubility studies. In-vitro dissolution and release studies under physiological conditions showed an immediate release of PRD from the solid dispersions, with almost 90% of the drug dissolved in the first 10 min. PRD was immediately released from BSA binding complex. This study demonstrates the potential for the use of BSA to enhance the solubility and dissolution rate, hence bioavailability, of the unionizable drugs.