Novel polyelectrolyte complexes (PECs) between N-carboxyethylchitosan (CECh) and well-defined (quaternized) poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) have been obtained. The modification of chitosan into CECh allows the preparation of PECs in a pH range in which chitosan cannot form complexes. The CECh/PDMAEMA complex is formed in a narrow pH range around 7. The quaternization of the tertiary amino groups of PDMAEMA enables complex formation with CECh both in neutral and in alkaline medium. Cross-linked CECh is also capable of forming complexes with (quaternized) PDMAEMA. The antibacterial activity of (cross-linked) CECh, (quaternized) PDMAEMA, and their complexes against Escherichia coli has been evaluated. In contrast to (quaternized) PDMAEMA, (cross-linked) CECh exhibits no antibacterial activity. The complex formation between cross-linked CECh and (quaternized) PDMAEMA results in a loss of the inherent antibacterial activity of the latter in neutral medium. In acidic medium, the complexes exhibit strong antibacterial activity due to complex disintegration and release of (quaternized) PDMAEMA.

Novel fibrous materials of stereocomplex between high-molecular-weight poly(d- or l-)lactide (HMPDLA or HMPLLA) and diblock copolymers consisting of poly(l- or d-)lactide and poly(N,N-dimethylamino-2-ethyl methacrylate) blocks, respectively (PLLA-block-PDMAEMA or PDLA-block-PDMAEMA), were prepared by solution electrospinning. Fibers with mean diameters ranging from 1400 to 1700 nm were obtained. The stereocomplex formation was evidenced by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. Annealing at 100 degrees C for 8 h resulted in the appearance of crystalline peaks at 2theta values of 12, 21, and 24 degrees for PLA stereocomplex. X-ray photoelectron spectroscopy (XPS) analyses revealed the gradient composition of the fibers with a surface enriched in tertiary amino groups from PDMAEMA blocks. The availability of tertiary amino groups imparts hemostatic and antibacterial properties to the stereocomplex fibrous materials, as indicated by the performed tests on blood cells and on pathogenic microorganisms.

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We report on novel gene delivery vector systems based on hybrid polymer-magnetic micelles. The hybrid micelles were prepared by codissolution of hydrophobically surface modified iron oxide and amphiphilic polystyrene-b-poly(quaternized 2-vinylpyridine) block copolymer (PS-b-P2QVP) in organic solvent. After extensive dialysis against water, micelles with positively charged hydrophilic corona of PQVP and hydrophobic PS core were prepared, in which magnetic nanoparticles were randomly distributed. The hybrid micelles were used to form complexes with linear (salmon sperm, 2000 bp, corresponding to M(w) of 1.32 × 10(6) Da) and plasmid (pEGFP-N1, 4730 bp, corresponding to M(w) of 3.12 × 10(6) Da) DNA. The resulting magnetopolyplexes of phosphate:amine (P/N) ratios in the 0.05-20 range were characterized by light scattering, ζ-potential measurements, and transmission electron microscopy as well as cytotoxicity and gel retardation assays. The investigated systems displayed a narrow size distribution, particle dimensions below 360 nm, whereas their ζ-potential values varied from positive to negative depending of the P/N ratio. The resulting vector nanosystems exhibited low toxicity. They were able to introduce pEGFP-N1 molecules into the cells. The application of a magnetic field markedly boosted the transgene expression efficiency of the magnetopolyplexes, which was even superior to those of commercial transfectants such as Lipofectamine and dendritic polyethylenimine.

A novel method of preparing modified chitosan films was developed. Bi- and tri-component chitosan films were prepared by blending chitosan with high molecular weight polyoxyethylene. The films were loaded with 8-hydroxy-7-iodoquinoline-5-sulfonic acid which was chosen as a model drug. The properties of the films were studied with respect to crystallinity, thermal stability and swelling degree. These properties were shown to depend on the ratio of polyoxyethylene/chitosan. The drug release profile from the films was measured in a buffer at pH 6.8 and 37°C. The antimycotic effect of the films against Candida albicans was determined.

Recent studies have demonstrated that the 5' leader (Q sequence) of tobacco mosaic virus RNA has a certain enhancing capacity for translation of mRNA in both prokaryotes and eukaryotes. In order to estimate the efficiency of 52 to initiate translation of mRNA in Escherichia coli, in comparison to the Shine-Dalgarno (S/D) sequence, we have inserted eight different eukaryotic genes into two types of E. coli expression vectors containing one constitutive promoter (Pl) but different translationinitiation sites (S/D or Q A 3 sequence, respectively). The efficiency of transcription and translation in vivo was evaluated for these vectors by measuring the yield of protein and both the level and stability of mRNA. We report that substitution of Q A 3 for S/D decreases the yield of expressed protein 4-1900-fold and the content of gene-specific mRNA is decreased by about sevenfold. However, in comparison with the S/D sequence, the level of protein expressed under the translational control of Q A 3 is less sensitive to changes in the 5' coding region. We also report that the 52 sequence contains a region of 10-12 nucleotides complementary to the small ribosomal subunit RNA (rRNA) of E. coli, Eikenella corrodens and Xenopus faevis, and to the rRNA of the (small ribosomal) subunit of Oryza sativa.It has been shown that the 5' untranslated region of the tobacco mosaic virus (TMV) RNA (52 sequence) enhances translation of mRNA in vivo and in vitro in both eukaryotes and prokaryotes [l -61. Gallie et al.[5] constructed a series of mutant sequence derivatives of the native Q sequence and studied their ability to enhance translation of two mRNA: pglucuronidase and chloramphenicol acetyltransferase in tobacco mesophyll protoplasts, Xenopus laevis oocytes and Escherichia roli. They found that deletion of the 25-base poly(CAA) sequence from the middle part of Q increased its enhancing effect in E. roli but not in eukaryotic cells. The efficiency of this sequence (designated QA3) to initiate translation in several types of bacteria has been studied, and the conclusion was drawn that Q is a sequence functionally equivalent to the Shine-Dalgarno (S/D) sequence [6].Unlike the native S/D sequence having the consensus AAGGAGGT [7, 81, the 5' untranslated region of the TMV RNA is devoid of G and is therefore unable to interact with the 3' end of 16s rRNA. This feature allows speculation that the 52 sequence initiates translation in bacteria by alternative mechanisms of binding of mRNA to the ribosomes.Several studies have shown that the efficiency of expression of a specific gene depends very much on the AUG-codonCorrespondence to M. G. AbouHaidar,

Six new asymmetric monomethine cyanine dyes have been synthesized and their fluorescence characteristics in the presence of nucleic acids studied. The new dyes have no fluorescence of their own in water solutions upon excitation at 480 nm but they become strongly fluorescent in the presence of nucleic acids. The fluorescence maxima of the investigated dyes are found at 525–545 nm when bound to dsDNA and around 600 nm upon binding to RNA and ssDNA. Fluorescence quenching studies with increasing concentrations of NaCl indicate that the cyanine dyes have a mixed (intercalating and groove binding) type of interaction with dsDNA. © 1997 Federation of European Biochemical Societies.