Tony Azzam

Current developments in gene transfection agents.

DNA can be delivered into the cell nucleus either using physical means or specific carriers that carry the genes into the cells for gene expression). Various carriers for delivering genes have been investigated which can be divided into two main groups: viral carriers where the DNA to be delivered is inserted into a virus, and cationic molecular carriers that form electrostatic interactions with DNA). Successful gene therapy depends on the efficient delivery of genetic materials into the cells nucleus and its effective expression within these cells). Although at present the in vivo expression levels of synthetic molecular gene vectors are lower than for viral vectors and gene expression is transient, these vehicles are likely to present several advantages including safety, low-immunogenicity, capacity to deliver large genes and large-scale production at low-cost). The two leading classes of synthetic gene delivery systems that have been mostly investigated are cationic lipids and cationic polymers). This review discusses recent developments in viral vectors, physical means and molecular gene carriers). The last part focuses on our recent studies in developing a new series of biodegradable polycations for in vitro and in vivo gene transfection).

Synthesis and characterization of novel water soluble amphotericin B-arabinogalactan conjugates.

The coupling of amphotericin B (AmB), a water-insoluble antifungal agent, to arabinogalactan (AG) via an imine or amine bond was systematically investigated. AG was oxidized using potassium periodate, purified from the oxidizing agent using ion-exchange chromatography, and reacted with AmB to form the Schiff base. The Schiff base was reduced to the amine using borohydride. All reactions took place in aqueous media. The purification of the oxidized AG from the oxidizing agent was essential to prevent oxidative degradation of AmB at the coupling step. We investigated the effects of AmB to AG ratio, buffer type, and reaction pH on the reaction yield, molecular weight, conjugate activity against pathogenic yeast and hemolytic activity. The optimum coupling conditions were buffer borate 0.1 M, pH 11 at room temperature for 48 h. Lower toxicity in vivo was achieved by using low-pressure gel permeation chromatography and applying the solution of AmB-AG conjugate through a Sephadex column. Both amine and imine AmB-AG conjugates were soluble in water and exhibited improved stability in aqueous solutions as compared to the unbound drug. The conjugates showed comparable minimum inhibitory concentration (MIC) values against Candida albicans. The conjugates were about 60 times less hemolytic against sheep erythrocytes than the free drug, and about 40 times less toxic in BALB/c mice.

Synthesis and biodegradation of arabinogalactan sponges prepared by reductive amination

The synthesis of polysaccharide-based sponges for the use in tissue engineering was systematically investigated. A comparison study of the branched polysaccharide arabinogalactan (AG) and the linear polysaccharide dextran in the formation of sponges by the reaction with diamines or polyamines was conducted. Three AG-based sponges were synthesized from the crosslinking reaction with different amine molecules. The sponges obtained were highly porous, rapidly swelled in water, and were stable in vitro for at least 11 weeks in aqueous media at 37 degrees C. AG-chitosan sponges were chosen as most suitable to serve as scaffolds for cell growth in tissue engineering. The biocompatibility in vivo of these sponges was evaluated by histological staining and non-invasive MRI technique after implantation in BALB/c mice. The sponge evoked an inflammatory response with vascularization of the implant. The inflammatory reaction decreased with time, indicating a healing process.

Analysis of fatty acid anhydrides and polyanhydrides

Abstract Acid anhydrides are considered as important reagents in organic and peptide synthesis and in recent years for the formation of prodrugs and biomaterials for controlled release of drugs. This article highlights the analysis of mixed anhydrides and polyanhydrides synthesized by various methods. Analytical methods including HPLC, GLC, 1 H NMR and IR spectroscopy are described for the determination of anhydride hydrolysis and amidation.

Gene therapy for malignant brain tumors

Malignant primary and metastatic brain tumors have remained fatal in spite of major advances in diagnostic tools and the improvement of conventional therapies. Recent discoveries in the molecular basis of the disease have allowed increased understanding of the events that lead to the development of brain tumors and have also brought a new spectrum of alternatives for treatment. By using gene therapy, brain tumors can be treated by targeting their fundamental molecular defects, delivering gene-drugs to the malignant cells. The possible targets for this type of treatment are progressively increasing but abundant clinical success has yet to be obtained, in part due to imperfect delivery systems. In this review, the genetic fundamentals of various cerebral neoplasms and neurogenetic syndromes, different strategies used for gene therapy, various available DNA delivery systems, status of ongoing clinical trials, and possible prospects for the futureare discussed.