Electrospun Fibers of Biocompatible and Biodegradable Polyesters, Poly(Ethylene Oxide) and Beeswax with Anti-Bacterial and Anti-Fungal Activities.

Fibrous materials composed of core-sheath fibers from poly(ethylene oxide) (PEO), beeswax (BW) and 5-nitro-8-hydroxyquinoline (NQ) were prepared via the self-organization of PEO and BW during the single-spinneret electrospinning of a homogeneous blend solution of the partners. Additionally, the application of the same approach enabled the preparation of fibrous materials composed of core-double sheath fibers from PEO, poly(L-lactide) (PLA) and NQ or 5-chloro-7-iodo-8-hydroxyquinoline (CQ), as well as from PEO, poly(ε-caprolactone) (PCL) and NQ. The consecutive selective extraction of BW and of the polyester with hexane and tetrahydrofuran, respectively, evidenced that core-double sheath fibers from PEO/polyester/BW/drug consisted of a PEO core, a polyester inner sheath and a BW outer sheath. In order to evaluate the possibility of the application of fibrous materials from PEO/BW/NQ, PEO/PLA/BW/NQ, PEO/PCL/BW/NQ and PEO/PLA/BW/CQ for plant protection, microbiological studies were performed using both phytopathogenic microorganisms (Pseudomonas corrugata, Fusarium graminearum and Fusarium avenaceum) and beneficial microorganisms (Pseudomonas chlororaphis, Bacillus amyloliquefaciens and Trichoderma asperellum). It was found that the fibrous materials had anti-bacterial and anti-fungal activity against both phytopathogenic and beneficial microorganisms. This is the first report on the activity of fibrous materials loaded with 8-hydroxyquinoline derivatives not only against phytopathogenic but also against beneficial microorganisms that are of importance in agriculture.

Core/Double-Sheath Composite Fibers from Poly(ethylene oxide), Poly(L-lactide) and Beeswax by Single-Spinneret Electrospinning.

The conventional approach for preparation of core-sheath fibers is coaxial electrospinning. Single-spinneret electrospinning of emulsions is a much less common method to obtain core-sheath fibers. Core-sheath structure may be generated by electrospinning of homogeneous blend solutions; however, reports on such cases are still scarce. Herein, the preparation of nanofibrous composites from poly(ethylene oxide) (PEO), poly(L-lactide) (PLA) and beeswax (BW) by single-spinneret electrospinning of their homogeneous blend solutions in chloroform is reported. The produced fibers had core/double-sheath structure with a PEO core, PLA inner sheath and BW outer sheath. This original fiber structure was evidenced by transmission electron microscopy, selective extraction of BW or PEO, and X-ray photoelectron spectroscopy. The PLA/BW double sheath led to hydrophobicity of the PEO/PLA/BW mats. The tensile tests revealed that PEO/PLA/BW mats had substantially improved mechanical behavior as compared to PEO, PLA and PEO/BW mats. PEO/PLA/BW mats can be used as drug carriers as evidenced by the one-pot incorporation of the model drug 5-nitro-8-hydroxyquinoline (NQ) into the fibrous materials. Microbiological tests showed that PEO/PLA/BW/NQ had antimicrobial activity. Therefore, the new materials are promising for wound healing applications.

Core-Sheath-Like Poly(Ethylene Oxide)/Beeswax Composite Fibers Prepared by Single-Spinneret Electrospinning. Antibacterial, Antifungal, and Antitumor Activities.

Composite fibrous materials are prepared from poly(ethylene oxide) (PEO) and beeswax (BW) by single-spinneret electrospinning using chloroform as a common solvent. The obtained fibers have core-sheath-like structure, as evidenced by the water contact angle values and corroborated by the results on the elemental composition of the fiber's surface determined by X-ray photoelectron spectroscopy (XPS) and by analyses with scanning electron microscopy of fibers before and after selective extraction of PEO or BW. Furthermore, the core-sheath-like structure is proven by transmission electron microscopy. This is attributed to self-assembly of BW molecules on the surface of the formed fibers driven by the incompatibility between PEO and BW. 5-Nitro-8-hydroxyquinoline (NQ) is embedded as a model drug with antibacterial, antifungal, and anticancer properties in the PEO/BW fibrous materials. XPS analyses reveal that NQ is present on the surface of the PEO/BW/NQ materials. Using a purposely designed cell for fixation of the fibrous materials the NQ release in phosphate buffer solution with рН 7.4 is followed. The new PEO/BW/NQ fibrous materials exhibit antibacterial activity against S. aureus and E. coli, antifungal effect against C. albicans, and selective anticancer activity against HeLa (human cervical adenocarcinoma cells) and SH-4 (human melanoma cells) cell lines.

Photocatalytic self-cleaning poly(L-lactide) materials based on a hybrid between nanosized zinc oxide and expanded graphite or fullerene.

New self-cleaning materials of polymer fibers decorated with a hybrid between nanosized zinc oxide and expanded graphite (EG) or fullerene (C60) were obtained. The new materials were prepared by applying electrospinning in conjunction with electrospraying. Poly(l-lactide) (PLA) was selected as a biocompatible and (bio)degradable polymer carrier. PLA solution was electrospun in combination with electrospraying of a suspension that contained the ZnO/EG or ZnO/C60 hybrid. Mats with different content of EG or C60 were obtained. The new materials were characterized by scanning and transmission electron microscopy (SEM and TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD). The photocatalytic activity of the materials was evaluated by using model dyes. The formation of a hybrid between ZnO and EG led to enhancement of the photocatalytic activity of the mats at ZnO/EG weight ratios of 90/10 and 85/15. Increase in the photocatalytic activity of the ZnO-containing mats was also achieved by the formation of a hybrid between ZnO and C60 at a fullerene content of 0.5 and 1.0 wt.% in respect to ZnO weight. The new materials exhibited antibacterial activity as evidenced by the performed studies against Staphylococcus aureus.

Poly(L-lactide) and poly(butylene succinate) immiscible blends: from electrospinning to biologically active materials.

For the first time the preparation of defect-free fibers from immiscible blends of high molar mass poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) in the whole range of the polyester weight ratios is shown. Electrospinning using the solvent-nonsolvent approach proved most appropriate. Moreover, electrospinning revealed crucial for the obtaining of PLA/PBS materials maintaining integrity. DSC and XRD analyses attested for a plasticizing effect and for increased PLA crystallinity at PBS addition to PLA. The mechanical properties of the PLA/PBS mats were controlled by the alignment of the fibers and changed from plastic to brittle materials upon increasing the PBS content. Drug loading and tests against pathogenic microorganisms suggested that the obtained mats can find application as antibacterial fibrous materials.

Antibacterial fluoroquinolone antibiotic-containing fibrous materials from poly(L-lactide-co-D,L-lactide) prepared by electrospinning.

Microfibrous materials based on poly(l-lactide-co-d,l-lactide) (coPLA) and coPLA/poly(ethylene glycol) (PEG) containing a fluoroquinolone antibiotic: ciprofloxacin hydrochloride (Cipro), levofloxacin hemihydrate (Levo) or moxifloxacin hydrochloride (Moxi) were obtained by electrospinning. The presence of Moxi led to an increase in the conductivity of the coPLA and coPLA/PEG spinning solutions and to the preparation of membranes composed of fibers aligned with the collector rotation direction. The one-step incorporation of the antibiotics in the fibers was confirmed by infrared spectroscopy and fluorescence microscopy. The antibiotics were dispersed in the coPLA or coPLA/PEG polymer matrix and the XRD spectra revealed the presence of crystalline phase characteristic of PEG and of the respective antibiotic. It was found that the release profiles of the antibiotics did not depend on the antibiotic nature but were dependent on the fiber composition. The presence of PEG in the fibers allowed a more rapid antibiotic release within the first 2h of release. The performed microbiological tests with Staphylococcus aureus revealed that the coPLA/Cipro, coPLA/PEG/Cipro, coPLA/Levo, coPLA/PEG/Levo, coPLA/Moxi and coPLA/PEG/Moxi mats inhibited the bacterial growth. In addition, the presence of an antibiotic in the mats led to a substantial decrease in the adhesion of the pathogenic microorganism and in the case of the coPLA/PEG/antibiotic series - to prevention thereof.

Antibacterial electrospun poly(ɛ-caprolactone)/ascorbyl palmitate nanofibrous materials.

The one-step incorporation of ascorbyl palmitate (AP), a widely used derivative of vitamin C, into nanofibrous mats of poly(ɛ-caprolactone) (PCL) by electrospinning was demonstrated. The incorporation of AP was attested by IR spectroscopy; the AP content was determined by thermogravimetric analysis (TGA); and the surface composition of the mats: by X-ray photoelectron spectroscopy (XPS). The possibility for deposition of silver nanoparticles onto PCL/AP mats using the ability of AP to reduce silver ions was demonstrated. The silver content was determined by TGA, and the silver nanoparticles were observed by transmission electron microscopy (TEM). The nanoparticles were composed of elemental silver, as verified by XPS analyses. The UV-vis spectrophotometric analyses, study on quenching of the free 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and microbiological tests against the pathogenic microorganism Staphylococcus aureus showed that AP preserved its stability and its antioxidant and antibacterial activity when incorporated in the nanofibrous mats.

Hybrid nanofibrous yarns based on N-carboxyethylchitosan and silver nanoparticles with antibacterial activity prepared by self-bundling electrospinning.

Hybrid nanofibrous materials with antibacterial activity consisting of yarns from N-carboxyethylchitosan (CECh) and poly(ethylene oxide) (PEO) that contain 5 wt% or 10 wt% silver nanoparticles (AgNPs) were prepared. This was achieved by electrospinning using formic acid as a solvent and as a reducing agent for silver ions. AgNO3 was used as an Ag(+)-containing salt. Its concentration was selected to be 0.02 mol/L or 0.04 mol/L in order the content of the AgNPs in the electrospun nanofibers to be 5 wt% or 10 wt%, respectively. The self-bundling of the fibers into yarns with a mean diameter of ca. 35 µm was enabled only by using a grounded needle electrode. The reduction of the silver ions to an elemental silver was evidenced by UV-vis spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The transmission electron microscopy (TEM) analyses revealed that AgNPs formed at AgNO3 concentration of 0.02 mol/L were with a mean diameter of 4±0.5 nm and were distributed uniformly within the fiber. The increase of AgNO3 concentration to 0.04 mol/L led to the preparation of AgNPs with a higher mean diameter and a broader diameter distribution as well as to aggregate formation. The performed studies on the antibacterial activity of CECh/PEO/AgNPs fibrous materials against Staphylococcus aureus showed that at AgNPs content of 5 wt% the mats had bacteriostatic, and at AgNPs content of 10 wt%-bactericidal activity.

Tuning of the surface biological behavior of poly(L-lactide)-based electrospun materials by polyelectrolyte complex formation.

Poly(L-lactide) (PLLA) and poly(L-lactide)/poly(ethylene glycol) (PLLA/PEG) electrospun fibrous materials coated with a polyelectrolyte complex (PEC) were prepared. This was achieved by consecutive deposition of a layer of N-carboxyethylchitosan (CECh) and a layer of a double hydrophilic block copolymer, poly(ethylene oxide)-b-quaternized poly[2-(dimethylamino)ethyl methacrylate] (PEO-b-PDMAEMAQ100), resulting in PEC formation between the two polyelectrolytes on the surface. Noteworthy, to improve the water wettability of the electrospun PLLA fibrous materials, that is, to enable more uniform deposition of the polyelectrolyte partners, water/ethanol mixed solvent was used for preparation of CECh and PEO-b-PDMAEMAQ100 solutions. The formation of PEC-based coating was demonstrated by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The PEC formation allows targeted modification of the biological behavior of the electrospun materials as evidenced by the performed tests in respect to blood cells and pathogenic microorganisms. In contrast to the pristine mats, the novel PEC-coated mats exhibit hemostatic properties and reduce the adhesion of pathogenic microorganisms.

Polylactide stereocomplex-based electrospun materials possessing surface with antibacterial and hemostatic properties.

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.

Electrospun hybrid nanofibers based on chitosan or N-carboxyethylchitosan and silver nanoparticles.

Hybrid nanofibers from chitosan or N-carboxyethylchitosan (CECh) and silver nanoparticles (AgNPs) were prepared by electrospinning using HCOOH as a solvent. AgNPs were synthesized in situ in the spinning solution. HCOOH slowed down the cross-linking of the polysaccharides with GA enabling the reactive electrospinning in the presence of poly(ethylene oxide) (PEO). EDX analyses showed that AgNPs are uniformly dispersed in the nanofibers. Since AgNPs hampered the cross-linking of chitosan and CECh with GA in the hybrid fibers, the imparting of water insolubility to the fibers was achieved at a second stage using GA vapors. The surface of chitosan/PEO/AgNPs nanofibers was enriched in chitosan and 15 wt.-% of the incorporated AgNPs were on the fiber surface as evidenced by XPS.

Amphiphilic poly(D- or L-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) block copolymers: controlled synthesis, characterization, and stereocomplex formation.

Novel well-defined amphiphilic poly(D-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PDLA-b-PDMAEMA) and poly(L-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PLLA-b-PDMAEMA) copolymers were obtained. The synthesis strategy consisted of a three-step procedure: (i) controlled ring-opening polymerization (ROP) of (D- or L-)lactide initiated by Al(O(i)Pr)(3), followed by (ii) quantitative conversion of the polylactide (PLA) hydroxyl end-groups with bromoisobutyryl bromide and (iii) atom transfer radical polymerization (ATRP) of DMAEMA. The PLA block molecular weight was kept below 5000 g/mol. The macromolecular parameters of the (co)polymers were determined by (1)H NMR spectroscopy and size exclusion chromatography (SEC). The stereocomplexes of PDLA-b-PDMAEMA/PLLA-b-PDMAEMA diblock copolymers were prepared via solvent casting. The stereocomplex formation was evidenced by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The obtained stereocomplexes had melting temperature of about 65 degrees C above that of the individual copolymers and exhibited diffraction patterns assigned to the stereocomplex crystallites. In addition, for the first time it was shown that the replacement of one of the PLA partners with high molecular weight PLLA or PDLA did not hamper the stereocomplex formation. The presence of PDMAEMA blocks proved to impart hydrophilicity of the synthesized copolymers and related stereocomplexes, as determined by static water contact angle measurements.

Natural polyampholyte-based core-shell nanoparticles with N-carboxyethylchitosan-containing core and poly(ethylene oxide) shell.

For the first time, core-shell nanoparticles were prepared from the natural polyampholyte N-carboxyethylchitosan (CECh). This was triggered by polyelectrolyte complex (PEC) formation between CECh and strong polyelectrolyte-containing double hydrophilic block copolymers. Quaternized poly[2-(dimethylamino)ethyl methacrylate]-b-poly(ethylene oxide) (quaternized PDMAEMA-b-PEO) and sodium poly(2-acrylamido-2-methylpropane sulfonate)-b-poly(ethylene oxide) (PAMPSNa-b-PEO) were used as polycation and polyanion, respectively. Based on the proper choice of partners and medium conditions, spherical core-shell nanoparticles with PEO shell were obtained both in basic and in acidic medium. The size of the particles was in the range 230-450 nm and depended on the partner nature, the polyelectrolyte molar mass, the pH, and the ionic strength. The obtained structures were studied by dynamic light scattering (DLS), atomic force microscopy (AFM), cryogenic transmission electron microscopy (cryo-TEM), and X-ray photoelectron spectroscopy (XPS). The results were explained in terms of the polyampholytic nature of CECh and the host-guest concept.

Novel biodegradable adaptive hydrogels: controlled synthesis and full characterization of the amphiphilic co-networks.

Adaptive and amphiphilic poly(N,N-dimethylamino-2-ethyl methacrylate-graft-poly[epsilon-caprolactone]) co-networks (netP(DMAEMA-g-PCL)) were synthesized from a combination of controlled polymerization techniques. Firstly, PCL cross-linkers were produced by ring-opening polymerization (ROP) of epsilon-CL initiated by 1,4-butane-diol and catalyzed by tin(II) 2-ethylhexanoate ([Sn(Oct)2]), followed by the quantitative esterification reaction of terminal hydroxyl end-groups with methacrylic anhydride. Then, PCL cross-linkers were copolymerized to DMAEMA monomers by atom-transfer radical polymerization (ATRP) in THF at 60 degrees C using CuBr complexed by 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) and 2-ethyl isobutyrylbromide (EiBBr) as catalytic complex and initiator, respectively. A comprehensive study of gel formation was carried out by employing dynamic light scattering (DLS) to determine the gel point as a function of several parameters and to characterize the viscous solutions obtained before the gel point was reached. The evolution of the mean diameters was compared to a model previously developed by Fukuda and these attest to the living formation of the polymer co-network. Furthermore, we also demonstrated the reliability of ATRP for producing well-defined and homogeneous polymer co-networks by the smaller deviation from Flory's theory in terms of cross-linking density. For sake of clarity, the impact of polymerization techniques over the final structure and, therefore, properties was highlighted by comparing two samples of similar composition, but that were produced by either ATRP or thermal-initiated free-radical polymerization (FRP).

Electrospun chitosan-coated fibers of poly(L-lactide) and poly(L-lactide)/poly(ethylene glycol): preparation and characterization.

Fibrous poly(L-lactide) (PLLA) and bicomponent PLLA/poly(ethylene glycol) mats were prepared by electrospinning and then were coated with chitosan. The presence of chitosan coating was proved by scanning electron microscopy and by fluorescence microscopy. On contact with blood, the chitosan coating led to changes in erythrocyte shape and in their aggregation. The haemostatic activity of the mats increased with increasing chitosan content. Microbiological studies against Staphylococcus aureus revealed that the chitosan coating imparts antibacterial activity to the hybrid mats. The combined haemostatic and antibacterial activities render these novel materials suitable for wound-healing applications.

Polyelectrolyte complexes based on (quaternized) poly[(2-dimethylamino)ethyl methacrylate]: behavior in contact with blood.

Polyelectrolyte complexes (PECs) between (quaternized) poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and (crosslinked) N-carboxyethylchitosan (CECh) or poly(2-acrylamido-2-methylpropane sodium sulfonate) (PAMPSNa) were prepared and characterized in terms of their stability, equilibrium water content, and surface morphology. The evaluation of the behavior of the studied PECs in contact with blood revealed that the (crosslinked) CECh/(quaternized) PDMAEMA complexes had lost the inherent PDMAEMA cytotoxicity but still preserved haemostatic activity. In contrast, the complex formation between (quaternized) PDMAEMA and PAMPSNa allowed the preparation of materials with improved blood compatibility.

Polyelectrolyte complexes between (cross-linked) N-carboxyethylchitosan and (quaternized) poly[2-(dimethylamino)ethyl methacrylate]: preparation, characterization, and antibacterial properties.

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.