1. Bioactive functional nanolayers of chitosan-lysine surfactant with single- and mixed-protein-repellent and antibiofilm properties for medical implantsUrban Ajdnik, Lidija Fras Zemljič, Olivija Plohl, Lourdes Pérez, Janja Trček, Matej Bračič, Tamilselvan Mohan, 2021, izvirni znanstveni članek Opis: Medical implant-associated infections resulting from biofilm formation triggered by unspecific protein adsorption arethe prevailing cause of implant failure. However, implant surfaces rendered with multifunctional bioactive nanocoatings offer apromising alternative to prevent the initial attachment of bacteria and effectively interrupt biofilm formation. The need to researchand develop novel and stable bioactive nanocoatings for medical implants and a comprehensive understanding of their properties incontact with the complex biological environment are crucial. In this study, we developed an aqueous stable and crosslinker-freepolyelectrolyte−surfactant complex (PESC) composed of a renewable cationic polysaccharide, chitosan, a lysine-based anionicsurfactant (77KS), and an amphoteric antibiotic, amoxicillin, which is widely used to treat a number of infections caused by bacteria.We successfully introduced the PESC as bioactive functional nanolayers on the“model”and“real”polydimethylsiloxane (PDMS)surfaces under dynamic and ambient conditions. Besides their high stability and improved wettability, these uniformly depositednanolayers (thickness: 44−61 nm) with mixed charges exhibited strong repulsion toward three model blood proteins (serumalbumin,fibrinogen, andγ-globulin) and their competitive interactions in the mixture in real-time, as demonstrated using a quartzcrystal microbalance with dissipation (QCM-D). The functional nanolayers with a maximum negative zeta potential (ζ:−19 to−30mV at pH 7.4), water content (1628−1810 ng cm−2), and hydration (low viscosity and elastic shear modulus) correlated with themass, conformation, and interaction nature of proteins. In vitro antimicrobial activity testing under dynamic conditions showed thatthe charged nanolayers actively inhibited the growth of both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcusaureus) bacteria compared to unmodified PDMS. Given the ease of fabrication of multifunctional and charged biobased coatingswith simultaneous protein-repellent and antimicrobial activities, the limitations of individual approaches could be overcome leadingto a better and advanced design of various medical devices (e.g., catheters, prosthetics, and stents). Ključne besede: silicone implants, protein-repellent, antimicrobial, chitosan, lysine, bioactive coatings, adsorption, QCM-D Objavljeno v DKUM: 15.04.2024; Ogledov: 266; Prenosov: 16 Celotno besedilo (4,24 MB) Gradivo ima več datotek! Več... |
2. Functionalisation of silicone by drug-embedded chitosan nanoparticles for potential applications in otorhinolaryngologyUrban Ajdnik, Lidija Fras Zemljič, Matej Bračič, Uroš Maver, Olivija Plohl, Janez Rebol, 2019, izvirni znanstveni članek Ključne besede: silicone, tympanostomy tube, chitosan, nanoparticles, drug delivery, antimicrobial activity Objavljeno v DKUM: 22.03.2019; Ogledov: 1460; Prenosov: 6 |
3. Surface modification of silicone with polysaccharides for the development of antimicrobial urethral cathetersMatej Bračič, 2016, doktorska disertacija Opis: In this work, alternative polysaccharide-based coatings were used to improve the antimicrobial and antifouling properties of silicone surfaces used for urethral catheters. The introduction of a catheter in the urethra is commonly connected with a high risk of microbial infections which often result in long-term health damage. Polysaccharide-based coatings like chitosan, carboxymethyl chitosan, and a synergistic formulation between hyaluronic acid and a natural lysine-based surfactant, were used to treat silicone surfaces to overcome the infection problems as an alternative to conventional approaches, which include the administration of antibiotics or coatings with metal ions. The polysaccharide-based macromolecular solutions and dispersions were firstly characterised by means of pH-titrations, dynamic light scattering and scanning electron microscopy in order to determine the size of particles in dispersions and their pH dependant charging behaviour. The knowledge gained from this was used to thoroughly study the interactions of the polysaccharide-based solutions and dispersions with the model silicone surfaces. The model surfaces were ultra-thin films prepared by dissolution of silicone in toluene and subsequent spin-coating on quartz crystals. The influence of pH, salt concentration, and various surface activation processes on the adsorption behaviour was evaluated by means of a very precise quartz crystal microbalance with dissipation. This knowledge was transferred to the application of the coatings on real systems i.e. casted silicone sheets and silicone tubes. The surface morphology, surface chemistry, as well as the mechanical and chemical stability of the coatings were further characterised on both model and real systems. For this purpose different microscopy and spectroscopy methods, pH-potentiometric titrations and methods for evaluation of mechanical properties were used. Finally the antimicrobial and antifouling properties were evaluated. The antimicrobial properties were tested against gram-positive and gram-negative bacteria as well as fungi, which are commonly found in infected urine, while the antifouling properties were tested by measuring the adhesion of bovine serum albumin, fibrinogen, and lysozyme biomolecules onto functionalised model films using the quartz crystal microbalance. The results showed that homogeneous and stable coatings can be achieved by adsorption from dispersions of the polysaccharide-based nanoparticles of 200-300 nm in size, which are formed by precipitation; i.e. careful pH adjustments of chitosan to pH = 6.5, carboxymethyl chitosan to pH = 7, and by mixing the hyaluronic acid and natural lysine-based surfactant solutions at concentrations of 2.5 x 10-4 mol/L and 1.25 x 10- 3 mol/L for the hyaluronic acid and 5.0 x 10-4 mol/L and 1.2 x 10-3 mol/L for the surfactant, respectively . The mass of the coatings on model silicone films can be increased by a 3-step adsorption, which directly influences the antimicrobial properties of the coatings that are improved with increasing coating mass, reaching values of up to 90 % in reduction of microorganism growth. It was also shown that the hyaluronic acid-natural surfactant formulation is superior to the chitosan coatings. The same conclusions were drawn from the antifouling evaluation where the zwitterionic nature of the formulation between natural based lysine surfactant and HA successfully suppressed the adhesion of biomolecules on silicone surfaces, while the chitosan coatings only moderately prevented the adhesion of proteins. One can conclude that the polysaccharide-based coatings can be successfully introduced to silicone surfaces from dispersion and as such successfully prevent biomolecule adhesion and reduce the growth of pathogen microorganisms which can be found in the urine during urethral infections. Ključne besede: Urethral catheters, Antimicrobial coatings, Silicone, Polysaccharides, Natural surfactants Objavljeno v DKUM: 24.10.2016; Ogledov: 2266; Prenosov: 236 Celotno besedilo (5,86 MB) |