Synthesis and characterization of amino-functionalized guar gum based polyurea: Preparation of iodine complexes, structural investigation and release studies

Biobased materials are expanding dramatically in various industrial applications due to their unique intrinsic properties. In this study, various chemical functionalization procedures were used to synthesize guar gum, a naturally occurring polysaccharide-based polyurea, and its iodine complexes. Firstly, guar gum was subjected to tosylation reaction using p-toluene sulphonyl chloride to introduce tosyl moieties in the polymer chain with the degree of substitution (DS) ranging between 0.16 and 1.54. Sample having the highest degree of tosyl moiety was further reacted with tris(2-aminoethyl) amine to produce 6-deoxy-6-tris(2-aminoethyl) amine derivative via nucleophilic substitution reaction to impart amino functional groups. The degree of substitution in 6-deoxy-6-tris(2-aminoethyl) amine derivative was found to be 0.59. 6-deoxy-6-tris(2-aminoethyl) amine derivative was reacted with different diisocyanates (Toluene-2,4-diisocyanate (TDI), 1,6-diisocyanatohexane (HMDI)) to produce guar gum based polyurea. Iodine complexes of the resulting polyurea were prepared by reacting with different iodinating agents. Different chemical reactions, formation of polyurea and its iodine complexes were thoroughly analyzed by different analytical techniques such as FT-IR, NMR, elemental analysis, XRD, UV-Vis spectroscopy, and a reaction scheme has been proposed. Morphological and rheological characteristics were analyzed by SEM and viscosity measurement. Thermal analysis was carried out by TGA and DSC studies. Finally, by examining the complex's UV-Vis spectra, the iodine release characteristics from polyurea‑iodine complexes were investigated.

Preparation and characterizations of antibacterial iodine-containing coatings on pure Ti

Iodine-containing coatings were prepared on pure Ti surfaces via electrochemical deposition to enhance their antibacterial properties. The factors influencing iodine content were analyzed using an orthogonal experiment. The electrochemically deposited samples were characterized using scanning electron microscopy with energy dispersive spectroscopy and X-ray photoelectron spectroscopy, and their antibacterial properties and cytotoxicity were evaluated. The results showed that changing the deposition time is an effective way to control the iodine content. The iodine content, coating thickness, and adhesion of the samples increased with deposition time. Iodine in the coatings mainly exists in three forms, which are I2, I3-, and pentavalent iodine. For samples with iodine-containing coatings, the antibacterial ratios against E. coli and S. aureus were greater than 90% and increased with increasing iodine content. Although the samples with iodine-containing coatings showed some inhibition of the proliferation of MC3T3-E1 cells, the cell viabilities were all higher than 80%, suggesting that iodine-containing coatings are biosafe.

The importance of fungal pathogens and antifungal coatings in medical device infections

In recent years, increasing evidence has been collated on the contributions of fungal species, particularly Candida, to medical device infections. Fungal species can form biofilms by themselves or by participating in polymicrobial biofilms with bacteria. Thus, there is a clear need for effective preventative measures, such as thin coatings that can be applied onto medical devices to stop the attachment, proliferation, and formation of device-associated biofilms. However, fungi being eukaryotes, the challenge is greater than for bacterial infections because antifungal agents are often toxic towards eukaryotic host cells. Whilst there is extensive literature on antibacterial coatings, a far lesser body of literature exists on surfaces or coatings that prevent attachment and biofilm formation on medical devices by fungal pathogens. Here we review strategies for the design and fabrication of medical devices with antifungal surfaces. We also survey the microbiology literature on fundamental mechanisms by which fungi attach and spread on natural and synthetic surfaces. Research in this field requires close collaboration between biomaterials scientists, microbiologists and clinicians; we consider progress in the molecular understanding of fungal recognition of, and attachment to, suitable surfaces, and of ensuing metabolic changes, to be essential for designing rational approaches towards effective antifungal coatings, rather than empirical trial of coatings.

Acyclic N-halamine-immobilized polyurethane: Preparation and antimicrobial and biofilm-controlling functions

Hydroxyl groups were introduced onto polyurethane surfaces through 1,6-hexamethylene diisocyanate activation, followed by diethanolamine hydroxylation. Polymethacrylamide was covalently attached to the hydroxylated polyurethane through surface grafting polymerization of methacrylamide using cerium (IV) ammonium nitrate as an initiator. After bleach treatment, the amide groups of the covalently bound polymethacrylamide chains were transformed into N-halamines. The new N-halamine-immobilized polyurethane provided a total sacrifice of 10⁷-10⁸ colony forming units per milliliter of Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), and Candida albicans (fungi) within 10 min and successfully prevented bacterial and fungal biofilm formation. The antimicrobial and biofilm-controlling effects were both durable and rechargeable, pointing to great potentials of the new acyclic N-halamine-immobilized polyurethane for a broad range of related applications.

Sustained release of antibiotics from uniform poly (ε-caprolactone) microspheres prepared by a simple fluidic device with a tapered glass capillary

Uniform poly(ε-caprolactone) microspheres containing a variety of water-soluble antibiotics, such as tobramycin, vancomycin, and gentamicin, were prepared by a simple fluidic device with a pristine or tapered glass capillary. Each type of antibiotic was dispersed in an organic solvent by ball-milling prior to microsphere preparation. The poly(ε-caprolactone) organic solution containing the powder of each antibiotic was introduced as the discontinuous phase into the fluidic device, where an aqueous phase containing surfactant served as the continuous phase. The poly(ε-caprolactone) microspheres were obtained after solvent evaporation. A tapered glass capillary was tested to produce poly(ε-caprolactone) microspheres, leading to the size reduction of the microspheres from 47.46 ± 0.72 to 25.49 ± 1.05 µm without destroying size uniformity. This size range should be suitable for parenteral injection into the human body. The release analysis revealed that gentamicin and vancomycin were released from the poly(ε-caprolactone) microspheres up to approximately 2 months in a more sustained manner than tobramycin, which is due to the solubility difference in the antibiotics in water. The antimicrobial activities of each type of antibiotic released from the poly(ε-caprolactone) microspheres were evaluated using Staphylococcus aureus and Escherichia coli.

Polymeric prodrugs of ampicillin as antibacterial coatings

A novel ampicillin prodrug containing two carboxylic acid functionalities was synthesized by reacting ampicillin with acyl chloride in the presence of base. This prodrug was subsequently converted into a poly(anhydride-amide) via solution polymerization. The polymer, which chemically incorporates the ampicillin prodrug into the polymeric backbone, was developed as a film to prevent infections associated with medical devices by controlled, localized release of antimicrobials. The robust polymer coatings exhibiting strong adhesion to stainless steel were produced under elevated temperature and reduced pressure. The in vitro hydrolytic degradation of the polymer into the ampicillin prodrug was measured and the antibacterial activity of polymer-derived coatings was examined using a Gram-positive bacterium, Staphylococcus aureus. Furthermore, the polymer cytotoxicity was screened using fibroblasts. The ampicillin prodrug demonstrated antibacterial activity and the polymer demonstrated no cytotoxic effects on fibroblasts. Based on these results, the biodegradation of the antimicrobial-based poly(anhydride-amide) into the prodrug displays substantial promise as an implant or implant coating to reduce device failure resulting from bacterial infections.

Silver sulfadiazine–immobilized celluloses as biocompatible polymeric biocides

Sulfadiazine was immobilized onto cotton cellulose using ethylene glycol diglycidyl ether as a binder. Upon treatment with diluted silver nitrate aqueous solution, the sulfadiazine moieties in the immobilized celluloses were transformed into silver–sulfadiazine coordination complexes. The resulting silver sulfadiazine–immobilized celluloses provided a 6-log reduction of 108 CFU mL−1 of Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), methicillin-resistant Staphylococcus aureus (drug-resistant bacteria), vancomycin-resistant Enterococcus faecium (drug-resistant bacteria), and Candida albicans (fungi) in 30–60 minutes, and a 5-log reduction of 107 PFU mL−1 of MS2 virus in 120 minutes. The antibacterial, antifungal, and antiviral activities were both durable and rechargeable. Additionally, trypan blue assay suggested that the new silver sulfadiazine–immobilized celluloses sustained excellent mammal cell viability, pointing to great potentials of the new materials for a broad range of health care–related applications.

Rapid disinfection by N-halamine polyelectrolytes

Two new N-halamine polyelectrolytes were synthesized, characterized, and deposited onto cotton fabric from a water solution using a layer-by-layer assembly technique. The fabrics were rendered biocidal by a dilute household bleach solution and challenged with Gram-positive and Gram-negative bacteria. The chlorinated swatches (five bilayer coated) inactivated ~106 Staphylococcus aureus and Escherichia coli O157:H7 within only 2 min of contact time. Although the coatings were susceptible to hydrolysis when exposed to repeated washing, the stability of the system was improved by a posttreatment with a cross-linking agent, 3-glycidoxypropyltrimethoxysilane.