Littérature scientifique sur le sujet « Plasma-biomaterial interaction mechanisms »

More than half of the hospital-associated infections worldwide are related to the adhesion of bacteria cells to biomedical devices and implants. To prevent these infections, it is crucial to modify biomaterial surfaces to develop the antibacterial property. In this study, chitosan (CS) and chondroitin sulfate (ChS) were chosen as antibacterial coating materials on polylactic acid (PLA) surfaces. Plasma-treated PLA surfaces were coated with CS either direct coating method or the carbodiimide coupling method. As a next step for the combined saccharide coating, CS grafted samples were immersed in ChS solution, which resulted in the polyelectrolyte complex (PEC) formation. Also in this experiment, to test the drug loading and releasing efficiency of the thin film coatings, CS grafted samples were immersed into lomefloxacin-containing ChS solution. The successful modifications were confirmed by elemental composition analysis (XPS), surface topography images (SEM), and hydrophilicity change (contact angle measurements). The carbodiimide coupling resulted in higher CS grafting on the PLA surface. The coatings with the PEC formation between CS-ChS showed improved activity against the bacteria strains than the separate coatings. Moreover, these interactions increased the lomefloxacin amount adhered to the film coatings and extended the drug release profile. Finally, the zone of inhibition test confirmed that the CS-ChS coating showed a contact killing mechanism while drug-loaded films have a dual killing mechanism, which includes contact, and release killing.

Surface properties of polyethylene terephthalate (PET) coated with the ternary monolayers of the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), the immunosuppressant cyclosporine A (CsA), and the antioxidant lauryl gallate (LG) were examined. The films were deposited, by means of the Langmuir–Blodgett (LB) technique, on activated by air low temperature plasma PET plates (PETair). Their topography and surface chemistry were determined with the help of atomic force microscopy (AFM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS), respectively, while wettability was evaluated by the contact angle measurements. Then, the surface free energy and its components were calculated from the Lifshitz–van der Waals/Acid–Base (LWAB) approach. The AFM imaging showed that the Langmuir monolayers were transferred effectively and yielded smoothing of the PETair surface. Mass spectrometry confirmed compatibility of the quantitative and qualitative compositions of the monolayers before and after the transfer onto the substrate. Moreover, the molecular arrangement in the LB films and possible mechanisms of DOPC-CsA-LG interactions were determined. The wettability studies provided information on the type and magnitude of the interactions that can occur between the biocoatings and the liquids imitating different environments. It was found that the changes from open to closed conformation of CsA molecules are driven by the hydrophobic environment ensured by the surrounding DOPC and LG molecules. This process is of significance to drug delivery where the CsA molecules can be released directly from the biomaterial surface by passive diffusion. The obtained results showed that the chosen techniques are complementary for the characterization of the molecular organization of multicomponent LB films at the polymer substrate as well as for designing biocompatible coatings with precisely defined wettability.

AbstractSynthetic biomaterials are widely used for a variety of in vivo and in vitro biomedical applications. However, the performance, safety, and cost effectiveness of medical products are determined by desirable interactions between the physiological environments and biomaterial surfaces. Hence, development of surface modifications for biomaterials is strongly demanded by the biomedical industry. High energy techniques, such as glow discharge plasma, have been developed to impart specific chemical functionality to the biomaterial surfaces or to deposit new polymer films with desired properties. The use of plasma surface modification for biomedical applications is reviewed in this paper.

ABSTRACTAn enzyme immunoassay has been developed to semi-quantitate the degree of activation of platelets adhering to biomaterials. The method employs a monoclonal mouse anti-GMP-140 antibody. The glycoprotein GMP-140 is contained in alpha granules of resting platelets and is translocated to the outer membrane of platelets during activation via the thrombin-dependent pathway. A polyclonal anti-mouse IgG peroxidase conjugate is then added and platelet activation can be semi-quantitated by use of a suitable substrate, such as OPD.The results obtained by this method compare well with scanning electron microscopy, and are shown to be less prone to the misinterpretation often associated with other conventional assay systems such as the determination of platelet adhesion by detection of ATP.The adhesion and activation of platelets by biomaterials has been compared before and after coating these materials with phosphorylcholine (PC) derivatives. PC, in its form as a headgroup in membrane phosphoglyceride (lecithin) and ceramide (sphingomyelin) is a ubiquitous component of cell membranes, and displays extremely low interaction and binding with plasma proteins such as Factor XII [1,2], complement [2], fibrinogen [3,2], immunoglobulins [2] and albumin [2,4].Using the immunoassay described here activation of platelets is seen to be dramatically reduced after coating surfaces, such as polyethylene, with PC compared with the untreated control. A PCcoated surface should therefore be an ideal starting point for developing tissue-inducing biomaterials. In addition endothelial cells contain GMP-140 in their secretory granules [5]. This would make this assay a potential tool in the investigation of endothelial cell - biomaterial interaction.

Surgical instruments are intended to come into direct contact with the patients’ tissue and therefore need to be sterilized and decontaminated in order to prevent infections, inflammations and transmission of diseases. In the last years low-pressure plasma discharges have been successfully applied to remove various biomolecules from surfaces. However, the knowledge of the physical-chemical interaction mechanisms between plasma and biomolecules is still rather poor, which is a major limiting factor for the optimization of this type of plasma treatment. In this work an original contribution to the field is presented, either in terms of process development, of physical mechanisms investigation and process diagnostic protocols assessment. Experimental results were obtained with a low pressure double coil planar inductively coupled plasma reactor. Plasma interactions with low bio-contamination levels (less than 5 μg/mm2) typical of biological residuals present after standard hospital sterilization protocols were studied. Removal mechanisms of biological thin films during plasma treatment with oxygen and water vapor containing discharge mixtures were characterized in-situ by means of quartz crystal microbalance (QCM), time resolved mass spectrometry and optical emission spectrometry. A novel QCM measurement technique was developed in this work as a quasi-online diagnostic tool in pulsed plasma operation. After plasma treatment, surfaces analysis techniques (XPS and AFM and profilometry) have been used to investigate ex-situ chemical and morphological changes at the surface of the protein films. Moreover mass removal rates as measured by QCM were found to depend on treatment time, showing a self limiting etching kinetics. Removal rates dynamics has been characterized in different plasma conditions by a set of descriptive parameters and correlated with plasma induced chemical composition changes and morphological modification of the protein film. The interaction mechanism between plasma and protein films have been studied in-situ. In the last years several authors presented experimental investigations devoted to isolate potential agents effective in plasma decontamination (UV, radicals, ions, heat) and to identify possible synergic mechanisms between them, but in most cases particle fluxes have been produced outside plasma environments (beam experiments) or the effect on protein films was studied by physically decoupling the effects of single mechanisms (UV screen, afterglows). In this work experiments were designed to quantitatively measure the fluxes of different potentially sterilizing species in the plasma phase (ions, radicals, UV and heat) and their interaction effects with a model protein film. Particle fluxes have been calculated using data from Langmuir probe, mass spectrometry, optical emission actinometry and infrared pyrometry measurements. Different experiments have been performed using plasma internal parameters (e.g. fluxes) as independent variables for the decontamination treatments, modifying one flux component at time while keeping the others constant the influence of synergetic effects between decontamination agents have been measured. Furthermore the control of the DC bias applied on the sample holder allows changing the energy of the ions (moderate voltages from 10 to 150 V were applied) interacting with the surface. Within the confidence limits of the statistical method implemented for validation, ion assisted chemical etching operating in an ion limited regime proved to be the mechanism which describes more accurately the etching rates for our biological substrates.