Additions of silver in biomedical application

Srebro ze swych antyseptycznych właściwości znane było już od starożytności. Po odkryciu antybiotyków (penicyliny w 1929 r.)poszło w zapomnienie, przegrywając z silnie rozwijającą się farmakologią. Powrót srebra nastąpił we wczesnych latach 60-tych XX wieku, a obecnie srebro jako środek bakteriobójczy przeżywa swój prawdziwy„renesans”. Srebro swoją mocną pozycję zawdzięcza temu, że atakuje komórkę bakterii na wielu płaszczyznach, m.in.: atakuje jądro bakterii – wiąże się z bakteryjnym DNA uszkadzając w ten sposób replikację komórek bakterii, powoduje zaburzenie przemieszczania się elektronów i tym samym ogranicza proces wytwarzania przez bakterie energii - proliferacja (rozrost) bakterii zostaje zahamowana, łączy się z błoną komórkową bakterii, co zakłóca jej funkcję, blokuje enzymy, tym samym powodując przerwanie procesów fizjologicznych. Obok zdolności zwalczania drobnoustrojów srebro może mieć jednak również toksyczne działanie na komórki człowieka. Jak wskazuje Schierholz i współaut. (1998) bezpieczeństwo stosowania srebra jest ograniczone. Wg nich koncentracja jonów srebra w płynach ustrojowych powyżej 10 mg/l może być toksyczna dla pewnych makromolekuł obecnych w ludzkim organizmie. Bosetti i współaut. (2002) w swoich badaniach dowodzą braku toksycznego wpływu srebra na komórki ludzkie (tj. limfocyty, fibroblasty i osteoblasty), a nawet twierdzą, że metal ten pobudza komórki kościotwórcze (osteoblasty) do wzmożonej aktywności. Argument ten dodatkowo budzi zainteresowanie srebrem jako czynnikiem nadającym się do użytku medycznego. Biorąc pod uwagę takie wyniki sprzymierzeńca w srebrze upatruje m.in. ortopedia (badania in vitro przeprowadzone przez Bosetti i współaut. (2002) dowodzą zwiększonej skuteczności implantów zawierających srebro, stosowanych przy złamaniach czy też stłuczeniach). Rozpatrując za i przeciw stosowaniu srebra jako środka działającego bakteriobójczo lub/i bakteriostatycznie należy wziąć pod uwagę, iż efekt toksyczności metali (w tym również srebra) zależy od formy w jakiej są one dostępne dla komórki mikroorganizmu, czy jest to jon czy postać organiczna (Ennever 1994).Realizowane badania mają na celu uzyskanie odpowiedzi na pytanie jak wykorzystać właściwości srebra do zastosowań biomedycznych przy jednoczesnym uniknięciu jego toksyczności. Wstępne badania pokazują, iż powierzchnie pokryte cienką warstwą srebra silnie związaną z substratem mogą ograniczać toksyczność srebra w środowisku tkankowym przy zachowaniu aktywności antybakteryjnej.Silver had been known since antiquity for its antiseptic properties. After the discovery of antibiotics (penicillin in 1929) felt into oblivion, losing to the strong growth of pharmacology. Return of silver occurred in the early 60s of the twentieth century, and now silver as a bactericide is undergoing a big “renaissance”. Silver its strong position has thanks to the fact that attacks the bacteria cell on multiple levels. It attacks the nucleus of bacteria- is associated with bacterial DNA, thus damaging the bacterial cell replication, causes a movement disorder of electrons and thereby reduces the process of energy by the bacteria - proliferation (growth) of bacteria is inhibited, combines with the cell membrane of bacteria, which disturbs with its function, blocks the enzymes, thus causing the disruption of physiological processes. Besides the ability to fight against microbial, silver can also have toxic effects on human cells. As indicated by Schierholz et al. (1998) the safety of silver is limited. According to them, the concentration of silver ions in body fluids of more than 10 mg /l maybe toxic to certain macromolecules present in the human body. Bosetti et al. (2002) in their studies have shown no toxicity of silver to human cells (eg lymphocytes, fibroblasts and osteoblasts), and even claim that this metal stimulates cells (osteoblasts) to increased activity. This argument makes that raises interest in silver as a particle suitable for medical use. Given these results orthopedics sees silver as an ally (in vitro studies conducted by Bosetti et al. (2002) demonstrate the increased effectiveness of silver-containing implants used for fractures or contusions). Considering the pros and cons of using silver as an antibacterial agent acting and /or bacteriostatic should take into account that the effect of toxic metals (including silver) depends on the form in which they are available to the cells of the microorganism, whether it is a form of ion or organic (Ennever 1994). Studies are carried out to obtain answers to the question of how to use the properties of silver for biomedical applications while avoiding its toxicity. Preliminary studies show that surfaces coated with a thin layer of silver strongly associated with the substrate can reduce the toxicity of silver in the tissue environment, while maintaining antibacterial activity

Mechanical and tribological properties of A-C:H/Ti coatings doped by silver using ion implantation and magnetron sputtering methods : abstract

Due to favorable mechanical, tribological and biomedical properties the carbon coatings are of interest of many branches of the industry [1]. Growing interest in Ag doped DLC coatings is observed within the space of the last several years. Both, well known antibacterial properties [2] of silver as well as a good biocompatibility [3] of carbon coatings constitute the outstanding solution for a variety of applications, especially for medical implants. The aim of this study was the evaluation of influence of silver onto the mechanical and tribological properties of nanocomposite DLC coatings. Carbon coatings were produced using a hybrid RFPACVD/MS method and silver ions were incorporated into carbon matrix. The processes consist of followed stages: synthesis of nanocomposite carbon (CVD) doped titanium coatings (PVD)[4] and next stage carbon (CVD) and silver deposition (PVD)or Ag ion implantation into carbon coating. Carbon layers synthesis was performed with use of the classic RF PACVD process in methane atmosphere whereas as the titanium ions source the pulsed magnetron sputtering (MS) process was applied. Second stage was performed in the same reaction chamber but the PVD process was carried out using the silver cathode. The ion implantation process was carried out with the use of silver ions with energy of 15 keV. In order to determine the influence of silver ion implantation process onto overall physiochemical properties of carbon coatings four ion doses of 2,4,7 and 10×1016Ag+/cm2 were applied. Due to application of the gradient of chemical composition of Ti–C it is possible to manufacture thick and well adherent carbon layers with a very good mechanical, tribological parameters and corrosion resistive. Application of silver as a doping material allowed modification of the mechanical and biological properties of manufactured layers depending on the silver amount (C:Ag ratio)

Plasma oxidized Ti6Al4V and Ti6Al7Nb alloys for biomedical applications

Titanium and its alloys are one of the most popular metallic materials used in medicine for many years. Their favorable mechanical properties, high corrosion resistance and good biotolerance in an environment of tissues and body fluids, cause that they are widely used as construction material of orthopaedic dental and neurological implants. Their disadvantages are poor tribological properties manifested by high coefficient of friction, scuffing and tendency to formation of adhesive couplings. In many research centers the works on improving the unfavorable tribological properties of titanium alloys are conducted. They rely on the use of modern methods of surface treatment including the thermo-chemical methods (nitriding, carburizing, oxidation) and the synthesis of thin films using PVD and CVD methods. In the presented work the glow discharge oxidation was applied to improve the surface properties of two-phase Ti6Al4V and Ti6Al7Nb titanium alloys. The results include a description of the obtained structure of the surface layer, surface topography, micro-hardness, wear ratio and corrosion resistance. The obtained results indicate changes in the surface layer of the material. The surface hardness was more than doubled and the depth of increased hardness region was up to 85 microns. This, in turn, several times decreased the wear rate of the modified materials while reducing the wear rate of the countersample. At the same time the carried out thermo-chemical treatment did not cause any structural changes in the core material. The oxidation process preferably influenced the corrosion properties of titanium alloys. Both, significant increase in the corrosion potential (approx. 0.36 V), as well as increased polarization resistance were observed. The modified surfaces also retained a high resistance to pitting corrosion

Plasma oxidized Ti6Al4V and Ti6Al7Nb alloys for biomedical applications

Titanium and its alloys are one of the most popular metallic materials used in medicine for many years. Their favorable mechanical properties, high corrosion resistance and good biotolerance in an environment of tissues and body fluids, cause that they are widely used as construction material of orthopaedic dental and neurological implants. Their disadvantages are poor tribological properties manifested by high coefficient of friction, scuffing and tendency to formation of adhesive couplings. In many research centers the works on improving the unfavorable tribological properties of titanium alloys are conducted. They rely on the use of modern methods of surface treatment including the thermo-chemical methods (nitriding, carburizing, oxidation) and the synthesis of thin films using PVD and CVD methods. In the presented work the glow discharge oxidation was applied to improve the surface properties of two-phase Ti6Al4V and Ti6Al7Nb titanium alloys. The results include a description of the obtained structure of the surface layer, surface topography, micro-hardness, wear ratio and corrosion resistance. The obtained results indicate changes in the surface layer of the material. The surface hardness was more than doubled and the depth of increased hardness region was up to 85 microns. This, in turn, several times decreased the wear rate of the modified materials while reducing the wear rate of the countersample. At the same time the carried out thermo-chemical treatment did not cause any structural changes in the core material. The oxidation process preferably influenced the corrosion properties of titanium alloys. Both, significant increase in the corrosion potential (approx. 0.36 V), as well as increased polarization resistance were observed. The modified surfaces also retained a high resistance to pitting corrosion