Regioselectively modified sulfated cellulose as prospective drug for treatment of malaria tropica

A semi-synthetic glycosaminoglycan analogue inhibits and reverses Plasmodium falciparum cytoadherence

A feature of mature Plasmodium falciparum parasitized red blood cells is their ability to bind surface molecules of the microvascular endothelium via the parasite-derived surface protein Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). This ligand is associated with the cytoadherence pathology observed in severe malaria. As pRBC treated with effective anti-malarial drugs are still able to cytoadhere, there is therefore a need to find an adjunct treatment that can inhibit and reverse the adhesion process. One semi-synthetic, sulfated polysaccharide has been identified that is capable of inhibiting and reversing sequestration of pRBC on endothelial cells in vitro under physiological flow conditions. Furthermore, it exhibits low toxicity in the intrinsic (APTT assay) and extrinsic (PT assay) clotting pathways, as well as exhibiting minimal effects on cell (HUVEC) viability (MTT proliferation assay). These findings suggest that carbohydrate-based anti-adhesive candidates may provide potential leads for therapeutics for severe malaria.

Gellan sulfate inhibits Plasmodium falciparum growth and invasion of red blood cells in vitro

Here, we assessed the sulfated derivative of the microbial polysaccharide gellan gum and derivatives of λ and κ-carrageenans for their ability to inhibit Plasmodium falciparum 3D7 and Dd2 growth and invasion of red blood cells in vitro. Growth inhibition was assessed by means of flow cytometry after a 96-h exposure to the inhibitors and invasion inhibition was assessed by counting ring parasites after a 20-h exposure to them. Gellan sulfate strongly inhibited invasion and modestly inhibited growth for both P. falciparum 3D7 and Dd2; both inhibitory effects exceeded those achieved with native gellan gum. The hydrolyzed λ-carrageenan and oversulfated κ-carrageenan were less inhibitory than their native forms. In vitro cytotoxicity and anticoagulation assays performed to determine the suitability of the modified polysaccharides for in vivo studies showed that our synthesized gellan sulfate had low cytotoxicity and anticoagulant activity.

Alginate microbeads are complement compatible, in contrast to polycation containing microcapsules, as revealed in a human whole blood model

Alginate microbeads and microcapsules are presently under evaluation for future cell-based therapy. Defining their inflammatory properties with regard to humans is therefore essential. A lepirudine-based human whole blood model was used as an inflammation predictor by measuring complement and leukocyte stimulation. Alginate microbeads were complement-compatible since they did not activate complement as measured by the soluble terminal complement complex (sTCC), Bb or the anaphylatoxins C3a and C5a. In addition, alginate microbeads were free of surface adherent leukocytes. In contrast, microcapsules containing poly-L-lysine (PLL) induced elevated levels of sTCC, Bb, C3a and C5a, surface active C3 convertase and leukocyte adhesion. The soluble PLL induced elevated levels of sTCC and up-regulated leukocyte CD11b expression. PMCG microcapsules containing poly(methylene-co-guanidine) complexed with sodium alginate and cellulose sulfate triggered a fast sTCC response and C3 deposition. The PMCG microcapsules were still less activating than PLL-containing microcapsules as a function of time. The amounts of anaphylatoxins C3a and C5a were diminished by the PMCG microcapsules, whereas leukocyte adherence demonstrated surface activating properties. We propose the whole blood model as an important tool for measuring bioincompatibility of microcapsules and microbeads for future applications as well as determining the mechanisms leading to inflammatory reactions.

Regioselective esterification and etherification of cellulose: a review

Deep understanding of the structure-property relationships of polysaccharide derivatives depends on the ability to control the position of the substituents around the monosaccharide ring and along the chain. Equally important is the ability to analyze position of substitution. Historically, both synthetic control and analysis of regiochemistry have been very difficult for cellulose derivatives, as for most other polysaccharide derivatives. With the advent of cellulose solvents that are suitable for chemical transformations, it has become possible to carry out cellulose derivatization under conditions sufficiently mild to permit increasingly complete regiochemical control, particularly with regard to the position of the substituents around the anhydroglucose ring. In addition, new techniques for forming cellulose and its derivatives from monomers, either by enzyme-catalyzed processes or chemical polymerization, permit us to address new frontiers in regiochemical control. We review these exciting developments in regiocontrolled synthesis of cellulose derivatives and their implications for in-depth structure-property studies.

Marine polysaccharides in pharmaceutical applications: an overview

The enormous variety of polysaccharides that can be extracted from marine plants and animal organisms or produced by marine bacteria means that the field of marine polysaccharides is constantly evolving. Recent advances in biological techniques allow high levels of polysaccharides of interest to be produced in vitro. Biotechnology is a powerful tool to obtain polysaccharides from a variety of micro-organisms, by controlling the growth conditions in a bioreactor while tailoring the production of biologically active compounds. Following an overview of the current knowledge on marine polysaccharides, with special attention to potential pharmaceutical applications and to more recent progress on the discovering of new polysaccharides with biological appealing characteristics, this review will focus on possible strategies for chemical or physical modification aimed to tailor the final properties of interest.

Homogeneous sulfation of bagasse cellulose in an ionic liquid and anticoagulation activity

Homogeneous sulfation of bagasse cellulose (BC) with chlorosulfonic acid-dimethylformamide was accomplished in an ionic liquid 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl). The BCS products from the sulfation had degrees of substitution (DS) in the range of 0.52-2.95 and a simultaneous substitution pattern at C-6, C-2 and C-3 positions. The sulfated BCS attained significant anticoagulation activity, causing a dose-dependent prolongation of coagulation time and inhibition of FIIa and FXa activities in human plasma. The anticoagulation activity of BCS showed a positive correlation with DS, and some of the activity indexes exceeded those of heparin.

Polyanionic drugs and viral oncogenesis: a novel approach to control infection, tumor-associated inflammation and angiogenesis

Polyanionic macromolecules are extremely abundant both in the extracellular environment and inside the cell, where they are readily accessible to many proteins for interactions that play a variety of biological roles. Among polyanions, heparin, heparan sulfate proteoglycans (HSPGs) and glycosphingolipids (GSLs) are widely distributed in biological fluids, at the cell membrane and inside the cell, where they are implicated in several physiological and/or pathological processes such as infectious diseases, angiogenesis and tumor growth. At a molecular level, these processes are mainly mediated by microbial proteins, cytokines and receptors that exert their functions by binding to HSPGs and/or GSLs, suggesting the possibility to use polyanionic antagonists as efficient drugs for the treatment of infectious diseases and cancer. Polysulfated (PS) or polysulfonated (PSN) compounds are a heterogeneous group of natural, semi-synthetic or synthetic molecules whose prototypes are heparin and suramin. Different structural features confer to PS/PSN compounds the capacity to bind and inhibit the biological activities of those same heparin-binding proteins implicated in infectious diseases and cancer. In this review we will discuss the state of the art and the possible future development of polyanionic drugs in the treatment of infectious diseases and cancer.