Synthesis and surface modification of polyurethanes with chitosan for antibacterial properties

Biodegradable ciprofloxacin-incorporated waterborne polyurethane polymers prevent bacterial biofilm formation in vitro

The aim of the present study was to explore whether ciprofloxacin-incorporated waterborne polyurethane (WBPU) polymers have the capacity to inhibit bacterial biofilm formation in vitro. WBPU polymers were incorporated with ciprofloxacin and were cultured with Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus) in media for 2, 4 or 7 days. In another experiment, the WBPU membranes were cultured with Proteus mirabilis (P. mirabilis) in artificial urine for 2, 4 or 7 days. Colony counting, scanning electron microscopy and fluorescence confocal microscopy were utilized to examine bacterial biofilms on the surfaces of membranes. The membranes were further co-cultured with P. mirabilis in a simple model of an artificial catheterized bladder in order to evaluate their ability to control encrustation. The WBPU films with ciprofloxacin effectively inhibited bacterial biofilm formation in the culture medium and in artificial urine. In addition, in artificial urine, the films with ciprofloxacin reduced catheter obstruction. In conclusion, ciprofloxacin-incorporated WBPU polymers are able to effectively inhibit bacterial biofilm formation in vitro.

A Mild Method for Surface-Grafting PEG Onto Segmented Poly(Ester-Urethane) Film with High Grafting Density for Biomedical Purpose

In the paper, poly(ethylene glycol) (PEG) was grafted on the surface of poly(ester-urethane) (SPEU) film with high grafting density for biomedical purposes. The PEG-surface-grafted SPEU (SPEU-PEG) was prepared by a three-step chemical treatment under mild-reaction conditions. Firstly, the SPEU film surface was treated with 1,6-hexanediisocyanate to introduce -NCO groups on the surface with high density (5.28 × 10-7 mol/cm²) by allophanate reaction; subsequently, the -NCO groups attached to SPEU surface were coupled with one of -NH₂ groups of tris(2-aminoethyl)amine via condensation reaction to immobilize -NH₂ on the surface; finally, PEG with different molecular weight was grafted on the SPEU surface through Michael addition between terminal C = C bond of monoallyloxy PEG and -NH₂ group on the film surface. The chemical structure and modified surface were characterized by FT-IR, ¹H NMR, X-ray photoelectron spectroscopy (XPS), and water contact angle. The SPEU-PEGs displaying much lower water contact angles (23.9⁻21.8°) than SPEU (80.5°) indicated that the hydrophilic PEG chains improved the surface hydrophilicity significantly. The SPEU-PEG films possessed outstanding mechanical properties with strain at break of 866⁻884% and ultimate stress of 35.5⁻36.4 MPa, which were slightly lower than those of parent film, verifying that the chemical treatments had minimum deterioration on the mechanical properties of the substrate. The bovine serum albumin adsorption and platelet adhesion tests revealed that SPEU-PEGs had improved resistance to protein adsorption (3.02⁻2.78 μg/cm²) and possessed good resistance to platelet adhesion (781⁻697 per mm²), indicating good surface hemocompatibility. In addition, due to the high grafting density, the molecular weight of surface-grafted PEG had marginal effect on the surface hydrophilicity and hemocompatibility.

Disulfide bond reconstruction: A novel approach for grafting of thiolated chitosan onto wool

Chitosan, a natural biopolymer, is used as a multifunctional agent for modification of wool either through chemical crosslinking or physical coating. For the first time, wool fabric has been modified with chitosan through disulfide bond breaking and reforming reactions. The chitosan was thiolated and then grafted onto the reduced wool fibers through disulfide bonds. In order to understand the mechanism of the grafting of thiolated chitosan onto wool, glutathione was used as a model compound for wool in the research. The structures of thiolated chitosan reacted with glutathione and wool fabrics grafted with thiolated chitosan were investigated by FTIR, ¹³CNMR, XPS, XRD, SEM. The dyeability, shrink-resistance and biocompatibility were also tested. The results suggested that glutathione reacted with thiolated chitosan and formed disulfide bond. The thiolated chitosan-grafted wool fabric had good shrink-resistance and dyeability. Hydrophilicity and antibacterial properties were also improved compared with untreated wool fabric. The results provide a novel approach for modification of wool through fiber-intrinsic groups like disulfide bonds.

Characterization and in vitro Biocompatibility of Binary Mixtures of Chitosan and Polyurethanes Synthesized from Chemically Modified Castor Oil, as Materials for Medical Use

This study aimed to evaluate the effect of the incorporation of chitosan into polyurethane matrices synthesized from chemically modified castor (Ricinus communis) oil by transesterification with pentaerythritol. An additional aim of this study was to determine the degree of acceptance as a biomaterial (obtained from renewable sources), based on the analysis of its mechanical properties (stress/rupture strain), hydrophilic character (contact angle), morphology (SEM) and in vitro compatibility of polyurethanes when in contact with mouse fibroblast L929 cells. No significant changes in mechanical properties were observed with the addition of chitosan to polyurethanes synthesized from chemically modified castor oil. All polyurethane formulas showed morphological changes with increased chitosan concentration. As chitosan/polyurethane binary mixtures do not present a cytotoxicity risk for L929 mouse fibroblasts and possess similar mechanical properties to soft and cardiovascular tissues, their use as a biomedical material is suggested.

Effect of chemical structure on properties of polyurethanes: Temperature responsiveness and biocompatibility

Polyurethanes are known as one of the most biocompatible and inherently blood-compatible materials and have a wide range of applications in the medical field due to their controllable structure and properties. Durability, elasticity, elastomeric structure, fatigue resistance, versatility, and easy acceptance by the biological media after the application makes these polymers preferable in medical area. In this study, polyurethane films were prepared using poly(propylene-ethylene glycol) and either toluene-2,4-diisocyanate or 4,4′-methylenediphenyl diisocyanate without adding any other ingredients such as solvent, catalyst, or chain extender to prevent negative effects of leachable molecules. Mechanical tests were performed at room temperature while swelling tests were conducted in water and phosphate-buffered saline at 4°C, 25°C, and 37°C. Temperature responsiveness was observed for the samples synthesized using toluene-2,4-diisocyanate and poly(propylene-ethylene glycol). These samples had more than 100% swelling at 4°C and about 4% swelling at 25°C and 37°C. Cytocompatibility tests were performed by culturing the samples and their extracts with mouse fibroblast cells (L929). Viability of human umbilical vein endothelial cells was studied to examine the compatibility of the films for blood contacting devices. Both toluene-2,4-diisocyanate and 4,4-methylenediphenyl diisocyanate–based polyurethane films showed no cytotoxic effect and good biocompatibility. Oxygen plasma treatment enhanced hydrophilicity of the films. After plasma treatment, human umbilical vein endothelial cell attachment on toluene-2,4-diisocyanate–based polyurethane films improved and 4,4-methylenediphenyl diisocyanate–based polyurethane films maintained their high cell affinity. Polyurethanes presenting temperature responsiveness, high biocompatibility, and high affinity for human umbilical vein endothelial cells were synthesized in medical purity and in a reaction media involving only diisocyanate and diol components without addition of any solvent, chain extender, or catalyst. Polyurethanes with these properties and as produced in this study are reported for the first time in the literature.

Surface modification and endothelialization of polyurethane for vascular tissue engineering applications: a review

Cardiovascular implants, especially vascular grafts made of synthetic polymers, find wide clinical applications in the treatment of cardiovascular diseases. However, cases of failure still exist, notably caused by restenosis and thrombus formation. Aiming to solve these problems, various approaches to surface modification of synthetic vascular grafts have been used to improve both the hemocompatibility and long-term patency of artificial vascular grafts. Surface modification using hydrophilic molecules can enhance hemocompatibility, but this may limit the initial vascular endothelial cell adhesion. Therefore, the improvement of endothelialization on these grafts with specific peptides and biomolecules is now an exciting field of research. In this review, several techniques to improve surface modification and endothelialization on vascular grafts, mainly polyurethane (PU) grafts, are summarized, together with the recent development and evolution of the different strategies: from the use of PEG, zwitterions, and polysaccharides to peptides and other biomolecules and genes; from in vitro endothelialization to in vivo endothelialization; and from bio-inert and bio-active to bio-mimetic approaches.

Modulation of osteogenic and haemostatic activities by tuning cationicity of genipin-crosslinked chitosan hydrogels

Chitosan as a natural cationic polysaccharide has drawn wide interests as surface modification materials in orthopedic applications, with the potential to achieve combined osteogenic, antimicrobial and haemostatic functions. The cationicity of chitosan has been reported to play an important role in modifying the osteoblastic cell responses and the antibacterial activities, while its effect on the haemostatic properties has been rarely studied. To this aim, we prepared carboxymethyl chitosan hydrogels with different cationicity through crosslinking with different concentrations of genipin (1%, 2.5%, 5% and 10%). The genipin concentration strongly influenced both mesenchymal stem cell (MSC) responses and blood coagulation activity for chitosan-hydroxyapatite samples. Increasing genipin concentration overall enhanced the osteogenic and haemostatic potentials, and an optimum window of chitosan cationicity (5% genipin in our case) led to both the best MSC response and coagulant activities. In particular, the cationicity had demonstrated a profound modulation effect on the haemostatic activities of chitosan samples, through influencing three different aspects of the coagulation processes, including intrinsic coagulation pathway, aggregation and activation of platelet, and activation of erythrocyte. Tuning the crosslinking degree thus provides a simple and effective approach to achieving combined osteogenic and haemostatic functions, which has great potential in surface modification of surgical implants.

A new textured polyphosphazene biomaterial with improved blood coagulation and microbial infection responses

A new poly[bis(octafluoropentoxy) phosphazene] (OFP) was synthesized for the purpose of blood contacting medical devices. OFP was further either developed into crosslinkable polyphosphazene (X-OFP) or blended with polyurethane (PU) as the mixture (OFP/PU) for improvement of mechanical property of polyphosphazene polymers. All the materials were fabricated as smooth films or further textured with submicron pillars for the assay of antimicrobial and antithrombotic properties. Results showed that crosslinkable OFP (X-OFP) and blends of OFP/PU successfully improved the mechanical strength of OFP and fewer defects of pillars were found on the textured polyphosphazene surfaces. The antithrombotic experiments showed that polyphosphazene OFP materials reduced human Factor XII activation and platelet adhesion, thereby being resistant to plasma coagulation and thrombosis. The bacterial adhesion and biofilm experiments demonstrated that OFP materials inhibited staphylococcal bacterial adhesion and biofilm formation. The surface texturing further reduced the platelet adhesion and bacterial adhesion, and inhibited biofilm formation up to 23 days. The data suggested that textured OFP materials may provide a practical approach to improve the biocompatibility of current biomaterials in the application of blood contacting medical devices with significant reduction in risk of pathogenic infection and thrombosis.

STATEMENT OF SIGNIFICANCE

The thromboembolic events and microbial infection have been the significant barriers for the long term use of biomaterials in blood-contacting medical devices. The development of new materials with multiple functions including anti-thrombosis and antibacterial surfaces is a high research priority. This study synthesized new biostable and biocompatible polyphosphazene polymers, poly[bis(octafluoropentoxy)phosphazene] (OFP) and crosslinkable OFP, and successfully improved the mechanical strength of polyphosphazenes. Polymers were fabricated into textured films with submicron pillars on the surfaces. The antimicrobial and antithrombotic assays demonstrated that new materials combined with surface physical modification have significant reduction in risk of pathogenic infection and thrombosis, and improve the biocompatibility of current biomaterials in the application of blood-contacting medical devices. It would be interest to biomaterials and bioengineering related communities.

The Effect of Ultraviolet Irradiation on the Physicochemical Properties of Poly(vinyl Chloride) Films Containing Organotin(IV) Complexes as Photostabilizers

Three organotin(IV) complexes containing ciprofloxacin as a ligand (Ph₃SnL, Me₂SnL₂ and Bu₂SnL₂; 0.5% by weight) were used as additives to inhibit the photodegradation of polyvinyl chloride films (40 µm thickness) upon irradiation with ultraviolet light (λmax = 313 at a light intensity = 7.75 × 10-7 ein dm-3 S-1) at room temperature. The efficiency of organotin(IV) complexes as photostabilizers was determined by monitoring the changes in the weight, growth of specific functional groups (hydroxyl, carbonyl and carbene), viscosity, average molecular weight, chain scission and degree of deterioration of the polymeric films upon irradiation. The results obtained indicated that organotin(IV) complexes stabilized poly(vinyl chloride) and the dimethyltin(IV) complex was the most efficient additive. The surface morphologies of poly(vinyl chloride) films containing organotin(IV) complexes were examined using an atomic force microscope and scanning electron microscopy. These showed that the surface of polymeric films containing organotin(IV) complexes were smoother and less rough, compared to the surface of the blank films. Some mechanisms that explained the role of organotin(IV) complexes in poly(vinyl chloride) photostabilization process were proposed.

Biomodification Strategies for the Development of Antimicrobial Urinary Catheters: Overview and Advances

Microbial burden associated with medical devices poses serious health challenges and is accountable for an increased number of deaths leading to enormous medical costs. Catheter-associated urinary tract infections are the most common hospital-acquired infections with enhanced patient morbidity. Quite often, catheter-associated bacteriuria produces apparent adverse outcomes such as urosepsis and even death. Taking this into account, the methods to modify urinary catheters to control microbial infections with relevance to clinical drug resistance are systematically evaluated in this review. Technologies to restrict biofilm formation at initial stages by using functional nanomaterials are elucidated. The conventional methodology of using single therapeutic intervention for developing an antimicrobial catheter lacks clinically meaningful benefit. Therefore, catheter modification using naturally derived antimicrobials such as essential oils, curcumin, enzymes, and antimicrobial peptides in combination with synthetic antibiotics/nanoantibiotics is likely to exert sufficient inhibitory effect on uropathogens and is extensively discussed. Futuristic efforts in this area are projected here that demand clinical studies to address areas of uncertainty to avoid development of bacterial resistance to the new generation therapy with minimum discomfort to the patients.

Polyphosphates as Inhibitors for Poly(vinyl Chloride) Photodegradation

Three polyphosphates were used as inhibitors for poly(vinyl chloride) (PVC) photodegradation. The polyphosphates were added to PVC at a concentration of 0.5% by weight. The PVC films (40 µm thickness) were irradiated at room temperature with ultraviolet (UV) light for up to 300 h. The changes in PVC films after irradiation were monitored by Fourier transform infrared spectroscopy, weight loss, viscosity-average molecular weight determination, and atomic force microscopy. These changes were very noticeable in the blank PVC films compared to the ones obtained when additives were used. The polyphosphates can inhibit the PVC photodegradation through direct absorption of UV light, interactions with PVC chains, and acting as radical scavengers.

New Tetra-Schiff Bases as Efficient Photostabilizers for Poly(vinyl chloride)

Three new tetra-Schiff bases were synthesized and characterized to be used as photostabilizers for poly(vinyl chloride) (PVC) films. The photostability of PVC films (40 μm thickness) in the presence of Schiff bases (0.5 wt %) upon irradiation (300 h) with a UV light (λmax = 365 nm and light intensity = 6.43 × 10-9 ein∙dm-3∙s-1) was examined using various spectroscopic measurements and surface morphology analysis. The changes in various functional groups' indices, weight and viscosity average molecular weight of PVC films were monitored against irradiation time. The additives used showed photostability for PVC films, with Schiff base 1 being the most effective additive upon irradiation, followed by 2 and 3. The atomic force microscopy (AFM) images for the PVC surface containing Schiff base 1 after irradiation were found to be smooth, with a roughness factor (Rq) of 36.8, compared to 132.2 for the PVC (blank). Several possible mechanisms that explain PVC photostabilization upon irradiation in the presence of tetra-Schiff bases were proposed.

Recyclable magnetite-silver heterodimer nanocomposites with durable antibacterial performance

There is a significant need for magnetite-silver nanocomposites that exhibit durable and recyclable antimicrobial activity. In this study, magnetic iron oxide nanoparticles (Fe₃O₄ NPs) coated with ethylenediamine-modified chitosan/polyacrylic acid copolymeric layer (Fe₃O₄@ECS/PAA) were fabricated. Subsequently, directly deposited silver (Ag) NPs procedure was carried out to form the antibacterial heterodimers of Fe₃O₄@ECS/PAA-Ag NPs. The composition and morphology of the resultant nanostructures were confirmed by FT-IR, XRD, TEM and TGA. The overall length of the heterodimers was approximately 45 nm, in which the mean diameter of Fe₃O₄@ECS/PAA NPs reached up to 35 nm, and that of Ag NPs was around 15 nm. The mass fraction of silver NPs in the nanocomposites was about 63.1%. The obtained Fe₃O₄@ECS/PAA NPs exhibited good colloidal stability, and excellent response to additional magnetic field, making the NPs easy to recover after antibacterial tests. In particular, the Fe₃O₄@ECS/PAA-Ag NPs retained nearly 100% biocidal efficiency (10⁶–10⁷ CFU/mg nanoparticles) for both Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus throughout ten cycles without washing with any solvents or water, exhibiting potent and durable antibacterial activity.

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Recyclable dual functional antibacterial heterodimer nanocomposites were fabricated.

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The nanostructures realized the combination of antibacterial ability and recyclable function.

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Biocidal efficiency retained nearly 100% throughout ten cycles.

Effect of the incorporation of chitosan on the physico-chemical, mechanical properties and biological activity on a mixture of polycaprolactone and polyurethanes obtained from castor oil

In the present study, polyurethane materials were obtained from castor oil, polycaprolactone and isophorone diisocyanate by incorporating different concentrations of chitosan (0.5, 1.0 and 2.0% w/w) as an additive to improve the mechanical properties and the biological activity of polyurethanes. The polyurethanes were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, stress/strain fracture tests and swelling analysis, and the hydrophilic character of the surface was determined by contact angle trials. The objectives of the study were to evaluate the effect of the incorporation of chitosan on the changes of the physico-chemical and mechanical properties and the in vitro biological activity of the polyurethanes. It was found that the incorporation of chitosan enhances the ultimate tensile strength of the polyurethanes and does not affect the strain at fracture in polyurethanes with 5% w/w of polycaprolactone and concentrations of chitosan ranging from 0 to 2% w/w. In addition, PCL5-Q-PU formulations and their degradation products did not affect cell viability of L929 mouse fibroblast and 3T3, respectively. Polyurethane formulations showed antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria. The results of this study have highlighted the potential biomedical application of this polyurethanes related to soft and cardiovascular tissues.

Study of the UV protective and antibacterial properties of aqueous polyurethane dispersions extended with low molecular weight chitosan

A series of aqueous dispersions of polyurethane (PU) and low molecular weight chitosan (CS_(LMW)) has been prepared in two steps synthetic process. In first step PU prepolymer, with NCO termini were prepared by reacting isophrone diisocyanate (IPDI), poly (caprolactone) diol (CAPA, Mn 1000), and 2,2-dimethylol propionic acid (DMPA), followed by neutralization of PU prepolymer with triethylamine (TEA). In second step PU prepolymer chain was extended by low molecular weight chitosan followed by dispersion formation by adding calculated volume of water. Molecular characterization of CS_(LMW)-PU finishes was done by FTIR and application on poly-cotton blended fabric samples was confirmed by scanning electron microscopy (SEM). Antimicrobial and UV protective performance of treated fabrics was performed by AATCC 100 and AATCC TM183 methods respectively. Furthermore, it shows that the addition of chitosan remarkably increases antimicrobial and UV protective properties of PUs.

Surface immobilization of kanamycin-chitosan nanoparticles on polyurethane ureteral stents to prevent bacterial adhesion

Bacterial adhesion is a major problem that can lead to the infection of implanted urological stents. In this study, kanamycin-chitosan nanoparticles (KMCSNPs) were immobilized on the surface of a polyurethane ureteral stent (PUS) to prevent urinary bacterial infection. KMCSNPs were synthesized using the ionic gelation method. The synthesized KMCSNPs appeared spherical with a ζ-average particle size of 225 nm. KMCSNPs were immobilized on the PUS surface by covalent immobilization techniques. The surface-modified PUS was characterized using attenuated total reflectance Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. The surface-modified PUS showed significantly increased antibacterial activity against Escherichia coli MTCC 729 and Proteus mirabilis MTCC 425 relative to the surface of an unmodified PUS. These findings suggest that the KMCSNP-immobilized PUS has the potential to prevent bacterial infection in the human urinary tract.

Photostabilizing Efficiency of Poly(vinyl chloride) in the Presence of Organotin(IV) Complexes as Photostabilizers

Three organotin complexes containing furosemide as a ligand (L), Ph₃SnL, Me₂SnL₂ and Bu₂SnL₂, were synthesized and characterized. Octahedral geometry was proposed for the Me₂SnL₂ and Bu₂SnL₂, while the Ph₃SnL complex has trigonal bipyramid geometry. The synthesized organotin complexes (0.5% by weight) were used as additives to improve the photostability of poly(vinyl chloride), PVC, (40 μm thickness) upon irradiation. The changes imposed on functional groups, weight loss and viscosity average molecular weight of PVC films were monitored. The experimental results show that the rate of photodegradation was reduced in the presence of the organotin additives. The quantum yield of the chain scission was found to be low (9.8 × 10(-7)) when Ph₃SnL was used as a PVC photostabilizer compared to controlled PVC (5.18 × 10(-6)). In addition, the atomic force microscope images for the PVC films containing Ph₃SnL₂ after irradiation shows a smooth surface compared to the controlled films. The rate of PVC photostabilization was found to be highest for Ph₃SnL followed by Bu₂SnL₂ and Me₂SnL₂. It has been suggested that the organotin complexes could act as hydrogen chloride scavengers, ultraviolet absorbers, peroxide decomposers and/or radical scavengers.

Spectroscopic, Physical and Topography of Photochemical Process of PVC Films in the Presence of Schiff Base Metal Complexes

The photostability of poly(vinyl chloride), PVC, containing various Schiff base metal complexes (0.5% by weight) was investigated. Various indices corresponding to a number of functional groups were monitored with irradiation of polymeric films to determine their photostabilization activities. The quantum yield of the chain scission (Φcs) of modified polymeric films was found to be (1.15–4.65) × 10⁶. The surface morphology of a PVC sample was investigated by the use of atomic force microscope (AFM). The photostability of PVC films in the presence of Schiff base additives was found to follow the following order: PVC < PVC + CuL₂ < PVC + CdL₂ < PVC + ZnL₂ < PVC + SnL₂ < PVC + NiL₂. Various mechanisms for PVC films photostability containing the Schiff base additives have been suggested.

Advanced removal of C. famata in bioaerosols by simultaneous adsorption and photocatalytic oxidation of Cu-doped TiO2/PU under visible irradiation

Polyurethane (PU), a honeycomb structure material, was used as a substrate onto which TiO₂ and Cu-TiO₂ were deposited in order to integrate the adsorption property to the photocatalysts. TiO₂ deposited on PU (TiO₂/PU) and Cu-doped TiO₂ deposited on PU (Cu-TiO₂/PU) were synthesized and applied to the removal of Candida famata (C. famata), a frequently encountered airborne yeast. The removal capacities of C. famata by PU, TiO₂/PU and Cu-TiO₂/PU were 1.5 × 10⁵, 3.2 × 10⁵ and 6.9 × 10⁵ (CFU/cm³) under dark condition and 1.5 × 10⁵, 3.3 × 10⁵ and 1.8 × 10⁶ (CFU/cm³) under visible light irradiation, respectively. PU and TiO₂/PU seemed to exhibit only an adsorption ability for removing C. famata in aerosols under both dark and visible light. The C. famata removal capacity of Cu-TiO₂/PU under visible light was increased 2.6-fold compared to that under dark condition. This significant increase was attributed to the Cu dopant, which enhanced the electron-hole separation efficiency and capacity of TiO₂, resulting in the high photocatalytic activity of Cu-TiO₂/PU under visible light.

Modified chitosan scaffolds: Proliferative, cytotoxic, apoptotic, and necrotic effects on Saos-2 cells and antimicrobial effect on Escherichia coli

Scaffolds used in tissue engineering applications should have high biocompatibility with minimum allergic, toxic, apoptotic, or necrotic effects on the growing cells and newly forming tissue and, if possible, have antimicrobial property to prevent infection at the host site. In this study, novel micro-fibrous chitosan scaffolds, having mineralized bioactive surface to enhance cell adhesion and a model antibiotic (gentamicin) to prevent bacterial attack, were prepared. The effects of the scaffolds on proliferation, viability, apoptosis, and necrosis of Saos-2 cells are reported for the first time. Wet spinning technique was used in the scaffold preparation and biomineralization was achieved by incubating them in five-time concentrated simulated body fluid for 2, 7, or 14 days (coded as CH-BM/2, CH-BM/7, and CH-BM/14, respectively). Gentamicin, an effectively used antibiotic in bone treatments, was loaded by vacuum-pressure cycle. Energy-dispersive X-ray results demonstrated that Ca/P ratio of the mineral phase varies depending on the incubation period. When the scaffolds were cultured with Saos-2 cells, cell adhesion and extracellular matrix formation occurred on all types of scaffolds. Alamar Blue cytotoxicity tests showed correlation among mineral concentration and cytotoxicity where CH-BM/2 had significantly more favorable properties. For all types of scaffolds, apoptosis and necrosis were less than 10%, meaning the samples are biocompatible. Gentamicin-loaded scaffolds showed high antimicrobial efficacy against Escherichia coli. The presence of mineral phase enhanced the adhesive capacity of cells and entrapment efficiency of antibiotic. These results suggest that the bioactive and antimicrobial scaffolds prepared in this study can act as promising matrices in bone tissue engineering applications.

An update on polysaccharide-based nanomaterials for antimicrobial applications

Scientific community has made a lot of efforts to combat the infectious diseases using antimicrobial agents, but these are associated with problems of development of multi-drug resistance and their adverse side effects. To tackle these challenges, nanocarrier-based drug delivery system using polysaccharides has received enormous attention in the past few years. These antimicrobial agents can become more efficacious when adsorbed, entrapped, or linked to polysaccharides. In addition, these nanocarrier-based systems provide an increase in the surface area of the drug and are able to achieve the targeted drug delivery as well as used for the synthesis of packaging materials with improved mechanical strength, barrier, and antimicrobial properties. This review focuses on potential therapeutic applications of nanocarrier-based drug delivery systems using polysaccharides for antimicrobial applications.

Polyurethane types, synthesis and applications – a review

Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships.

Effect of radio frequency discharge plasma on surface properties and biocompatibility of polycaprolactone matrices

Surface modification of bioresorbable polymer material (polycaprolactone, PCL) with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target was investigated. Plasma treatment resulted in an increase of surface roughness of PCL, crystallite size, the surface free energy and hydrophilicity. Increased treatment time (30, 60, 150 seconds) provoked the polymer surface saturation with the sputtering target ions (calcium, phosphorus). The assessment of plasma exposure of PCL surface on bone marrow multipotent mesenchymal stromal cells behavior (BM MSCs) has been performed. Modification of the polymer surface with the abnormal glow discharge stimulated adhesion and subsequent proliferation of BM MSCs; thus, maximum values were achieved with the surface treatment for 60 s. This type of plasma modification did not affect cell viability (apoptosis, necrosis). Thus, the surface modification with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target, appear to be a promising method of surface modification of bioresorbable polymer material (PCL) for tissue engineering.

Immobilization of heparin on chitosan-grafted polyurethane films to enhance anti-adhesive and antibacterial properties

Infections caused by bacteria adhering to implant surfaces are one of the main reasons for the failure of the implants. In this study, polyurethane (PU), which is the most commonly used polymer in the production of medical devices, was synthesized and surfaces of polyurethane films were modified by chitosan (CH) grafting and heparin (Hep) immobilization in order to enhance anti-adhesiveness and antibacterial properties. Functional groups present on the surface, topographical shapes, and free energies of the polyurethane films were determined. Pristine polyurethane, chitosan-grafted polyurethane (PU–CH), and heparin immobilized polyurethane (PU–CH–Hep) films demonstrated high anti-adhesive efficacy against bacteria in the given order, where PU–CH–Hep was the most effective one. When PU–CH–Hep samples were incubated with different bacteria, complete death was observed for Pseudomonas aeruginosa (Gram negative), Staphylococcus aureus (Gram positive), and Staphylococcus epidermidis (Gram positive). Some living Escherichia coli (Gram negative) were observed after 24 h of incubation. Pristine and modified polyurethane samples demonstrated no adverse effect on proliferation of L929 fibroblast cells and were found to be biocompatible according to MTT cytotoxicity tests.

Novel integrated approach of adsorption and photo-oxidation using Ag-TiO2/PU for bioaerosol removal under visible light

We investigated a novel approach by synthesizing an integrated material, which could act as both adsorbent and photocatalytic material, for bioaerosol purification under visible light conditions. Ag was used as a dopant agent to enhance photocatalytic activity of TiO₂, leading to high photocatalytic activity of the doped TiO₂ even under visible light. Under visible light, the doped TiO₂ photocatalyst could produce oxy radicals, oxidative agents, that participate in oxidation reactions to decompose important organic components of bacteria, leading to death or removal of bacteria from an aerosol. Adsorption property was integrated into the enhanced TiO₂ photocatalyst by using polyurethane (PU), a honeycomb structure material, as a substrate for coating process of the doped TiO₂. Three materials including pristine PU, TiO₂ coating on PU (TiO₂/PU), and Ag-doped TiO₂ coating on PU (Ag-TiO₂/PU) were used to remove Escherichia coli in an aerosol under visible light. Under dark conditions, the removal capacities of E. coli in the aerosol by PU, TiO₂/PU, and Ag-TiO₂/PU were 1.2 × 10⁵, 2.7 × 10⁵, and 6.2 × 10⁵ (CFU/cm³), respectively. Under visible light irradiation, the removal capacities of E. coli in an aerosol by PU, TiO₂/PU, and Ag-TiO₂/PU were 1.2 × 10⁵, 2.7 × 10⁵, and 1.8 × 10⁶ (CFU/cm³), respectively. The improvement of the removal capacity by TiO₂/PU and Ag-TiO₂/PU, versus PU, is due to adsorption alone and the combination of adsorption plus photocatalytic activity, respectively.

Organic-inorganic hybrid nanoparticles for bacterial inhibition: synthesis and characterization of doped and undoped ONPs with Ag/Au NPs

Organic nanoparticles (ONPs) of lipoic acid and its doped derivatives ONPs/Ag and ONPs/Au were prepared and characterized by UV-Visible, EDS, and TEM analysis. The antibacterial properties of the ONPs ONPs/Ag and ONPs/Au were tested against bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhi). Minimal Inhibitory Concentration (MIC) and bacterial growth inhibition tests show that ONPs/Ag are more effective in limiting bacterial growth than other NPs, particularly, for Gram positive than for Gram-negative ones. The order of bacterial cell growth inhibition was ONPs/Ag > ONPs > ONPs/Au. The morphology of the cell membrane for the treated bacteria was analyzed by SEM. The nature of bond formation of LA with Ag or Au was analyzed by molecular orbital and density of state (DOS) using DFT.

Two methods for one-point anchoring of a linear polysaccharide on a gold surface

Two strategies to achieve a one-point anchoring of a hydrolyzed pullulan (P9000) on a gold surface are compared. The first strategy consists of forming a self-assembled monolayer of a 6-amino-1-hexanethiol (AHT) and then achieving reductive amination on the surface between the aminated surface and the aldehyde of the polysaccharide reductive end sugar. The second consists of incorporating a thiol function at the extremity of the pullulan (via the same reductive amination), leading to P9000-AHT and then immobilizing it on gold by a spontaneous reaction between solid gold and thiol. The modified pullulan was characterized by NMR and size-exclusion chromatography coupled to a light-scattering detector. P9000-AHT appears to be in a disulfide dimer form in solution but recovers its unimer form with dithiothreitol (DTT) treatment. The comparison of the two strategies by contact angle and XPS revealed that the second strategy is more efficient for the pullulan one-point anchoring. P9000-AHT even in its dimer form is easily grafted onto the surface. The grafted polymer seems to be more in a coil conformation than in a rigid brush. Furthermore, QCM measurements highlighted that the second strategy leads to a grafting density of around 3.5 × 10(13) molecules·cm(-2) corresponding to a high surface coverage. The elaboration of a dense and oriented layer of polysaccharides covalently linked to a gold surface might enhance the use of such modified polysaccharides in various fields.