Synthesis, antiviral and contraceptive activities of nucleoside-sodium cellulose sulfate acetate and succinate conjugates.

Chemical conjugates between sodium cellulose sulfate (CS), displaying contraceptive and HIV-entry inhibiting properties, and nucleoside reverse transcriptase inhibitors (NRTIs) (3'-azido-2',3'-dideoxythymidine (AZT), 3'-fluoro-2',3'-dideoxythymidine (FLT), or 2',3'-dideoxy-3'-thiacytidine (3TC)) were designed to simultaneously provide contraceptive and anti-HIV activity. Two linkers, acetate and succinate, were used to conjugate the nucleoside analogs with CS. The conjugates containing cellulose sulfate-acetate (CSA) (e.g., AZT-CSA and FLT-CSA) were found to be more potent than CS and other conjugates (e.g., AZT-succinate-CS, and FLT-succinate-CS). The presence of both sulfate and the acetate groups on cellulose were critical for generating maximum anti-HIV activity. In addition to showing equal potency against wild-type and multidrug resistant HIV-1, the AZT-CSA conjugate displayed significant contraceptive activity in an animal model, providing the initial proof-of-concept for the design and synthesis of dual-activity compounds based on these combinations.

Preparation and characterization of starch/cyclodextrin bioadhesive microspheres as platform for nasal administration of Gabexate Mesylate (Foy) in allergic rhinitis treatment.

Bioadhesive and biodegradable microspheres were obtained by chemical cross-linking with epichlorohydrin of an alkaline solution of a mixture of starch and alpha-, beta-, or gamma-cyclodextrin (CyD). Microspheres were characterized by scanning electron microscopy, swelling degree, and water retention. The percentage of the effective CyD in microspheres was estimated by measuring the amount of iodine and typical organic compounds (TOCs) retained in the hydrophobic cavity of CyD. Gabexate Mesylate (trade name Foy); GM), an antiallergic drug, was included in microspheres by soaking in an aqueous solution containing the drug, followed by solvent evaporation or lyophilization. UV, IR, and DSC data indicated that despite the fact that GM is a hydrophilic drug, its hydrophobic moiety close to the benzene ring is able to penetrate the CyD cavity and to form stable inclusion complexes. Values of the association equilibrium constant for GM binding to CyD, obtained by UV differential spectroscopy, indicated that the affinity of the drug for alpha- and gamma-CyD is higher than that for beta-CyD. In vitro, GM was gradually released during 1h. Even if the release rate of the drug is relatively fast, the microspheres might actually provide the best platform since the material adheres to the nasal mucosa which was proved by adhesion tests. The GM integrity was checked by comparing its anti-trypsin activity before and after release.

Nitric oxide-dependent human acrosomal loss induced by PPCM (SAMMA) and by nitric oxide donors occurs by independent pathways: basis for synthesis of an improved contraceptive microbicide.

PPCM (previously designated sulfuric acid-modified mandelic acid [SAMMA]) is a contraceptive microbicide in preclinical development. Its contraceptive activity is attributable in part to its ability to promote premature acrosomal loss. Prior studies showed that PPCM-induced human acrosomal loss (PAL) is Ca(2+)-dependent. This study was carried out to determine transduction elements downstream from Ca(2+) entry. PAL is inhibited by inhibitors selective for endothelial-type nitric oxide synthase. PAL is completely inhibited by 0.1 microM ODQ (soluble guanylate cyclase inhibitor). PAL is inhibited by protein kinase G inhibitors with selectivity for the type II isotype. Several inhibitors of the nitric oxide/cyclic guanosine monophosphate (cGMP)/protein kinase G pathway induce Ca(2+)-dependent acrosomal loss when added alone. These responses are inhibited by nifedipine, a blocker of Ca(v1.x) voltage-dependent channels. Acrosomal loss induced by the nitric oxide donor SNAP (SNAL) does not require added Ca(2+). Sperm production of nitric oxide is increased by PPCM, an effect inhibited by nitro-L-arginine (nitric oxide synthase inhibitor). Although inhibited by ODQ, SNAL and acrosomal loss induced by other nitric oxide donors are unaffected by KT5823 (protein kinase G inhibitor). Unlike PAL, SNAL is partially inhibited by KT5720 (protein kinase A inhibitor) and genistein (protein tyrosine kinase inhibitor). Acrosomal loss response to PPCM and SNAP added in combination suggests that these agents act by independent mechanisms. A PPCM derivative was synthesized, in which a nitric oxide donor was esterified to PPCM (NOSPPA-23). NOSPPA-23 induces acrosomal loss with or without added Ca(2+). The ED(50) of NOSPPA-23 (4.8 nM) in the presence of Ca(2+) is 35-fold less than that of PPCM. These findings suggest the following: 1) elements responsible for PAL include endothelial nitric oxide synthase, soluble guanylate cyclase, and type II protein kinase G; 2) the resting state of the nitric oxide/cGMP/protein kinase G pathway is a determinant of acrosomal status; 3) PPCM and nitric oxide donors induce acrosomal loss via nitric oxide, but through independent pathways; and 4) covalent attachment of a nitric oxide donor to PPCM provides synergistic efficacy as a stimulus of acrosomal loss. Further studies with this novel prototype as an improved contraceptive microbicide are warranted.

Evaluation of novel biodegradable cyclic carbonate polyester copolymers for cytocompatibility using MRC-5 cells.

The objective of this work was to synthesize and characterize a novel series of biodegradable cyclic carbonate polyester copolymers based on lactide and 5-methyl-5-benzyloxy-carbonyl-1,3-dioxan-2-one (MBC). Two compositions were selected for characterization. One copolymer was based on a racemic mixture of 1-lactide with 15.4 mole % MBC and the other was based on 1-lactide with 8.2 mole % MBC. These polymers contain carboxylic acid moieties along the backbone that may be used for tethering bioactive agents, forming ionic crosslinks or be reacted with vinyl containing monomers to allow free radical crosslinking. The initial materials evaluated have the carboxylic acid functionalities blocked with benzene. These polymers and the de-blocked versions may have potential applications for hard and soft tissue scaffolds, control drug delivery matrixes or a variety of other applications in medicine. The copolymer samples were pressed into 7.0-mm diameter disk using a KBr press. The disks were then sterilized using U.V radiation under a laminar flow hood. After sterilization, the copolymer disks were submerged in 2 ml of media and placed in a CO2 regulated incubator at 37 degrees C. A total of six groups per phase (n = 7 test tubes per group) were used in this study. Test tubes in groups I and III were plated with MRC-5 and subsequently treated with media alone (controls). Test tubes in groups II and IV were plated with MRC-5 and subsequently treated with media before being introduced to copolymer samples. Cell number, as well as, biochemical markers such as protein and malondialdehyde (MDA) were determined at the end of the 24, 48 and 72-hour time periods. Representative test tubes were subjected to an H&E staining procedure for microscopic morphological evaluation. The results of this evaluation suggest that the exposure of both copolymers produced a non-cytotoxic environment with the MRC-5 cell line. Although both copolymers are non-cytotoxic, the sample having the higher MBC content is the preferred composition based upon MDA levels and morphological evaluations.