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Fibrous materials of poly(l-lactide- co-d,l-lactide), poly(l-lactide- co-d,l-lactide)/poly(ethylene glycol), and curcumin were prepared by electrospinning. The incorporation of poly(ethylene glycol) in the fibers caused a decrease in the mean fiber diameters down to 700 nm and in the water contact angle value, the latter being equal to 0 at poly(l-lactide- co-d,l-lactide)/poly(ethylene glycol) 60/40 weight ratio. The water contact angle values of poly(l-lactide- co-d,l-lactide)/curcumin fibrous materials considerably exceeded those of films of the same composition (approximately 120° as compared to approximately 95°, for electrospun mats and solution-cast films, respectively). Curcumin affected the thermal stability of the fibrous materials and the crystallinity degree of the polymers. The mechanical properties of the electrospun materials also depended on the composition of the polymer matrix and the amount of curcumin therein. In the curcumin-containing fibers, curcumin was found in the amorphous state, while higher antioxidant activity was exhibited by poly(l-lactide- co-d,l-lactide)/poly(ethylene glycol)/curcumin fibrous materials. In vitro determination of the activated partial thromboplastin time and prothrombin time showed that poly(l-lactide- co-d,l-lactide)/curcumin fibrous materials displayed anticoagulant activity. Antibacterial effect toward Staphylococcus aureus was manifested by the curcumin-containing mats.

In this study, a novel water-insoluble polyelectrolyte complex between chitosan and poly(acrylic acid- co-maleic acid) was prepared and characterized. The chitosan used (M̅v = 23,000–60,000 g/mol) formed water-insoluble polyelectrolyte complexes at pH 2.2–4.8 and water-soluble chitosan oligomers (M̅v = 2,700 g/mol) at pH 2.2–7.4. The polyelectrolyte complexes formed were used in the preparation of novel carriers for a Trichoderma spp. biocontrol agent. Three types of beads were prepared: noncross-linked chitosan beads, coated with a chitosan/poly(acrylic acid- co-maleic acid) polyelectrolyte complex; genipin-cross-linked chitosan beads; and cross-linked chitosan beads, coated with a chitosan/poly(acrylic acid- co-maleic acid) polyelectrolyte complex. Trichoderma viride was immobilized either in the bulk or in the surface layer of the beads. The microbiological tests confirmed that T. viride immobilized in either mode maintained viability and the capacity to develop and to inhibit the growth of the pathogenic soil microorganisms, Alternaria and Fusarium.

The antiproliferative activity of electrospun mats of poly(L-lactide- co-D,L-lactide) (coPLA) containing quaternized chitosan (QCh) and/or doxorubicin hydrochloride (DOX) was evaluated against the Michigan Cancer Foundation-7(MCF-7) human breast carcinoma cell line. QCh- and DOX-containing nanofibrous mats possess good antiproliferative activity and decrease considerably the viability of the MCF-7 cells for the different periods of cell incubation as confirmed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Fluorescent microscopy analyses and scanning electron microscopy observations revealed that apoptosis was one of the major mechanisms of MCF-7 cell death induced by the QCh- and DOX-containing mats.

Bundle membranes were made by electrospinning poly(L-lactide) (PLLA) and PLLA/poly(ethylene glycol) (PEG) using the ionic properties of diclofenac sodium (DS), lidocaine hydrochloride (LHC), benzalkonium chloride (BC), and combinations thereof. The self-bundling of the fibers was initiated by using a designed grounded multi-needle electrode. Computer simulations on the electrostatic field distribution depended on the multi-needle position with respect to a grounded rotating drum collector which allowed the optimal arrangement of the electrospinning component set-up to obtain bundles. The combination of the ionization of the drugs as well as the utilization of the multi-needle electrode allowed the successful preparation of a series of mono-(DS, LHC, or BC), bi-(DS/LHC), and three-(DS/LHC/BC) drug(s)-loaded bundle membranes. Based on the Fourier transform infrared spectra, the drug systems were incorporated into the fibrous materials. The microbiological tests confirmed that the PLLA/ PEG bundle membranes containing BC (10 wt%), DS (30 wt%), DS/LHC (DS, 30 wt%; LHC, 30 wt%), and DS/LHC/BC (DS, 15 wt%; LHC, 15 wt%; and BC, 10 wt%) exhibited antibacterial activity against the pathogenic microorganism Staphylococcus aureus.

Nanofibrous mats containing chitosan and Trichoderma viride spores were successfully prepared by electrospinning. The presence of the fungal spores in the nanofibrous mats was determined by scanning electron microscopy. The viability of the incorporated spores was estimated by cultivating the obtained biohybrids and studying the fungus growth. The fungal spores incorporated into the chitosan-containing fibrous mats were viable; the T. viride developed and reproduced normally. The electrospun biohybrid materials inhibited the growth of diverse phytopathogenic strains ( Fusarium, Alternaria) when placed at suitable growth conditions. Coating the plant sprouts with the biohybrids by direct electrospinning was easily done.

Poly(L-lactide) (PLLA)/polyethylene glycol (PEG) mixed solutions were successfully electrospun into micro-or nanofibrous polymer mats. The fiber diameter was in the range 100nm-6μm. The effect of the concentration of the spinning solutions and the ratio of PLLA/PEG on the fiber diameter and morphology was investigated. The hydrophilicity was tuned by varying the PLLA/PEG ratio. The tissue compatibility of the electrospun nanofibrous scaffolds was screened using two different cell models of human dermal fibroblasts and the osteoblast-like cell line MG-63. Both types of cells attached uniformly and approximately equally to all PLLA/PEG nanofibers. In long-term cultures osteoblast-like cells tend to spatially organize in tissue-like structure, particularly within the scaffold with the highest PEG content (PLLA/PEG at weight ratio 70/30). These results indicate that PLLA mixed with hydrophilic PEG produces a promising new biocompatible material for engineering scaffolds.

Electrospinning is a promising method for producing polymer materials composed of micro- and nanosized fibers. This method allows the preparation of random and aligned fibers of different morphologies, such as cylindrical or ribbon-shapes, defect-free or with defects, and with or without pores or porous. The increasing number of studies on electrospinning requires a set of criteria for more complex evaluation of the fiber morphology and the topology of these polymer materials to be established. The main characteristics necessary for a complex evaluation of the morphology of electrospun micro- and nanofibers have been systematized in this paper. Examples of characterization of the morphology and of the alignment of various micro- and nanofibers are given.

The first successful preparation of nanofibers of a polyampholyte (N-carboxyethylchitosan) by electrospinning was achieved by adding a non-ionogenic water-soluble polymer to the spinning solution. Using this approach, other polyelectrolytes, poly(2-acryloylamido-2-methylpropanesulphonic acid) (PAMPS), and copolymers of 2-acryloylamido-2-methylpropane-sulphonic acid (AMPS) and acrylic acid [P(AMPS- co-AA)] were also electrospun into nanofibers. The non-ionogenic water-soluble polymers were polyacrylamide (PAAm) and poly(vinyl alcohol) (PVA). The average diameters of the electrospun nanofibers were in the range 50-260nm. The average diameter of the nanofibers significantly decreased with increasing polyelectrolyte content. The electrospun nanofibers were crosslinked by heat treatment at 100, 120 or 150°C for the N-carboxyethylchitosan/PAAm pair and at 90°C in the case of P(AMPS- co-AA)/PVA. The presence of an ionizable low-molecular-weight compound (7-iodo-8-hydroxyquinoline-5-sulphonic acid, SQ) led to a more than two-fold decrease in the diameter of the nanofibers and to the appearance of defects. The SQ-containing nanofibers showed antimicrobial activity against pathogenic microorganisms.

Chitosan gel beads were prepared as a model for new chitosan materials and their blood compatibility was evaluated in vitroin human pool plasma and in human whole blood. The one-stage method for the preparation of monolithic beads consisted of performing a template polymerization of 2-acryloylamido-2-methylpropanesulfonic acid (AMPS) or copolymerization of AMPS and acrylic acid. Monolithic beads of semi-interpenetrating networks chitosan/copolymer were prepared in the presence of a cross-linking agent. The equilibrium degree of swelling of the beads was dependent on the composition. Reservoir-type beads consisting of a chitosan core and a coating of polyelectrolyte complex with anticoagulant activity and chitosan were also prepared. The reservoir-type beads and the monolithic beads showed improved compatibility with blood in comparison with the uncoated chitosan beads.

The enzymatic degradation of three types of pH-sensitive hydrogels, composed of the natural polyaminosaccharide chitosan and polyacrylamide, was studied. The weight of the films that were made with net-PAAm- i-chitosan, net-chitosan- i-PAAm and net-chitosan- net-PAAm decreased in the presence of the Trichoderma viride enzyme complex ; thus, the chitosan in the composite retained its degradability after crosslinking. The rate of enzymatic degradation depended on the structure of the network, on the amount of crosslinking agents, on the pH of the medium and on the temperature. Crosslinked chitosan alone degraded slower than net-chitosan- i-PAAm; this was attributed to the facilitated penetration of enzyme by the water-soluble PAAm in the semi-IPNs. T. viride embedded in chitosan/PAAm films or beads developed and reproduced normally. However, T. viride embedded in net-chitosani-PAAm developed considerably slower, and development was not detected in the case of net-PAAm- i-chitosan. All of the networks proved to be appropriate carriers of Bacillus subtilis.

Three types of polymer networks of chitosan and polyacrylamide (PAAm) – semi-interpenetrating networks (semi-IPNs) of chitosan and crosslinked PAAm ( net-PAAm– t-chitosan), semi-IPNs of PAAm and crosslinked chitosan ( net-chitosan– t-PAAm), and interpenetrating networks (IPNs) of crosslinked chitosan and crosslinked PAAm ( net-PAAm– net-chitosan) were prepared. Chitosan, in a two-fold molar excess to PAAm, provided pH-sensitivity to hydrogel networks. The amount of the crosslinking agent did not have much influence on the microhardness of network films, while higher contents of PAAm increased it. The equilibrium degree of swelling of the hydrogels had the highest values at pH 4 and decreased on increasing pH (pH 7, pH 9) or the ionic strength of the medium as well as with increasing of the degree of crosslinking. The networks in which chitosan was crosslinked, – semi-IPNs net-chitosan– t-PAAm and IPNs net-chitosan– net-PAAm, showed five cycles of completely reversible swelling.

The degradation of chitosan using a crude enzyme complex from the soil fungus Trichoderma viride was examined in terms of temperature, pH, enzyme activity and the presence of a polymer partner. It was found that chitosan hydrolysis is not suppressed by combining it with polyoxyethylene or poly(2-acryloylamido-2-methylpropanesulfonic acid). The results on Trichoderma viride immobilized on beads imply that chitosan, as well as its polymer complexes are appropriate carriers for development of ecologically safe phytosanitary preparations.

New macromolecular chelators were synthesized under mild conditions by reaction of 8-hydroxyquinoline-2-carboxylic acid (8Q2COOH) with polyethers having amino end-groups (Jeffamines ED®) or poly(ethylene glycol)s in the presence of dicyclohexylcarbodiimide and dimethylamino-pyridine. The prepared amides (8Q2CONH-POE) and esters (8Q2COO-POE) were characterized by SEC, DSC, IR, 1H and 13C NMR spectroscopy, and MALDI-TOF mass spectrometry. It was found that the polyethers had 8-hydroxy-2-quinolinyl end groups and formed complexes with Fe3+ ions. The obtained complexes were studied with IR spectroscopy and DSC. The plant tests showed that the Fe3+ complex of 8Q2CONH-POE2000 had high efficacy in the remedy of iron-deficient maize plants under hydroponic conditions.

A drug release system based on chitosan and 8-hydroxy-7-iodoquinoline-5-sulfonic acid (SQ), a substance with antimicrobial and antimycotic activity, was developed. Drug loading and release from beads non-crosslinked or crosslinked with glutaraldehyde (GA) and epichlorohydrin (ECC), as well as beads coated with a polyelectrolyte of complex chitosanpoly(2-acryloylamido--2-propane sulfonic acid) under different conditions were compared. SQ was sorbed almost stoichiometrically with respect to the free amino groups in non-crosslinked or crosslinked ECC beads, whereas much higher amounts of SQ were entrapped in the beads crosslinked with GA. The amount of SQ released depended on chitosan crosslinking and pH of the medium, while the release rate of the drug is additionally influenced by drying and coating the beads with a polyelectrolyte complex. The longest period of diffusionally controlled release was observed from dry beads crosslinked with GA at pH 7.

The effect of Fe3+ chelates of polyethers having terminal 8-quinolinol (8Q) residues linked to the polymer chain at different ring positions on the remedy of iron-deficient maize plants was studied. It was found that Fe3+ chelates of polymers with 8Q groups attached at the 5-position (HOQ-P-QOH) were the most effective. Decreasing the temperature and photosynthetic photon flux density caused a four-fold retardation in the remedy of iron-deficient plants. The results are explained in terms of the stability of the Fe3+ complexes. The microbiological tests showed that the polyethers were active against Gram-positive and Gram-negative bacteria. HOQ-P-QOH also exhibited antimycotic activity.

The hydrolytic release of 5-chloro-8-hydroxyquinoline (HQ) from 5-chloro-8-quinolinylacrylate (AQ) containing polymers was studied under physiological under conditions (pH 7.2 and 37°C) as well as in acidic and alkaline medium. The hydrolysis rate was influenced by autocatalytic process with participation by quinolinyl groups as well as by neighboring groups. For copolymers of AQ and acrylamide (AM), the release rate increased with increasing pH, temperature, and the content of hydrophilic monomer. Copolymers of AQ and N-vinylpyrrolidone (VP) exhibit a lower rate of HQ release because of steric hindrance of the hydrolysis site and the influence of the alternating VP-AQ sequences which contribute to the enhanced hydrophobicity of the copolymer. The antimicrobial activity of the copolymers was found to be related to their hydrolysis behavior. The attachment of a biologically active agent to a macromolecular carrier can prolong its effect.

A new method for the dissolution of chitosan in an aqueous medium using polyoxyethylene diacid was developed. Films cast from these solutions were found to swell reversibly. The effect of polyether content and pH on the swelling behavior of the films was studied. Monolayer type devices for drug release applications were prepared using 8-hydroxy-7-iodoquinoline-5-sulfonic acid as a model drug.

Apparent partition coefficients for a series of poly(oxyethylene)s with 5-chloro-8-quinolinoxyl end-groups and different polyether chain lengths; POE*400, POE*1000, POE*1000 and POE*3000 (the subscripts show the molecular weight of the polyether chain) were determined for the system 1-octanol/water at different pHs at 37°. The partition coefficient was found to decrease with increasing polyether chain length. The substituent constants were calculated and the effect of the substituents on the partition behavior of the compounds was estimated. The antibacterial effect of POE* on gram-positive and gram-negative bacteria was found to be lower than that of CHQ. The activity of POE* slightly increased in the presence of Fe3+ ions.

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.