Impact of surface topography and coating on osteogenesis and bacterial attachment on titanium implants

Titanium (Ti) plays a predominant role as the material of choice in orthopaedic and dental implants. Despite the majority of Ti implants having long-term success, premature failure due to unsuccessful osseointegration leading to aseptic loosening is still too common. Recently, surface topography modification and biological/non-biological coatings have been integrated into orthopaedic/dental implants in order to mimic the surrounding biological environment as well as reduce the inflammation/infection that may occur. In this review, we summarize the impact of various Ti coatings on cell behaviour both in vivo and in vitro. First, we focus on the Ti surface properties and their effects on osteogenesis and then on bacterial adhesion and viability. We conclude from the current literature that surface modification of Ti implants can be generated that offer both osteoinductive and antimicrobial properties

Antibacterial Surfaces, Thin Films, and Nanostructured Coatings

Creating antibacterial surfaces is the primary approach in preventing the occurrence and diffusion of clinical infections and foodborne diseases as well as in contrasting the propagation of pandemics in everyday life. Proper surface engineering can inhibit microorganism spread and biofilm formation, can contrast antimicrobial resistance (AMR), and can avoid cross-contamination from a contaminated surface to another and eventually to humans. For these reasons, antibacterial surfaces play a key role in many applications, ranging from biomedicine to food and beverage materials, textiles, and objects with frequent human contact. The incorporation of antimicrobial agents within a surface or their addition onto a surface are very effective strategies to achieve this aim and to properly modify many other surface properties at the same time. In this framework, this Special Issue collects research studying several materials and methods related to the antibacterial properties of surfaces for different applications and discussions about the environmental and human-safety aspects

Development of polymeric coatings with combined antifouling/antibacterial properties for titanium dental implants

Titanium dental implants are a commonly used solution for the replacement of lost teeth. Even though the success rate is high, the number of infections related to the placement of the implant is still remarkable and may impair the proper function of the device, leading to health and economic costs. The infections related to medical devices start with a bacterial adhesion and proliferation on the material surface, leading to the formation of a complex biofilm able to protect the bacteria from the host immune response and the treatment with antibiotic. Due to the difficulty of treatment of the implant site one the biofilm is settled, one of the strategies to avoid the infection is to deal with the initial bacterial adhesion. This PhD thesis deals with the development of polymeric antibacterial coatings on titanium for dental implants, focusing on the achievement of fast and cost-effective procedure. With this aim, different coating strategies have been developed, tested and compared. A pre-treatment of the titanium surface was optimized in the first part of the thesis in order to achieve a clean surface and to enhance the chemical reactivity of the titanium oxide. With this aim, low pressure plasma activation was the selected method. The use of plasma activation allows for the removal of organic contaminants while increasing the surface energy of the treated surfaces. For the preparation of the polymeric antibacterial coatings, two different antifouling polymers have been used, namely, polyethylene glycol (PEG) and poly-2-hydroxyethylmetacrylate (PHEMA). PEG coatings were prepared by three different techniques, a wet chemical technique (silanization), a plasma enhanced chemical vapor deposition and an electrochemical process (electrodeposition). The three methods rendered an ultra-thin coating able to resist the bacterial adhesion. On the other hand, PHEMA-like coatings were prepared in a novel set-up by treating the liquid monomer by a plasma jet. Moreover, the different coatings were biofunctionalized in order to achieve multifunctionality and enhance the performance of the coating. For instance, the combination of PEG with a cell adhesion peptide (RGD) reported a better human fibroblast adhesion while maintaining the antifouling properties of the coating. PEG was also used as a platform for the immobilization of antimicrobial peptides (AMP). The bonding of the polymer with the AMP was optimized, achieving a surface able to reduce the bacterial adhesion and to kill the bacteria still able to adhere to the surface. Finally, the combination of two different plasma polymerized coatings with antibiotics (either Doxycycline or Vancomycin) was used as a drug delivery system.Els implants dentals de titani són la solució més estesa per substituir peces dentals. Tot i que les taxes d'èxit són elevades, el nombre d'infeccions relacionades amb la col·locació de l'implant és elevat, i influeix en el mal funcionament de l'implant, amb un elevat cost tan a nivell econòmic com de salut. Les infeccions associades als dispositius sanitaris comencen amb una adhesió i proliferació dels bacteris a la superfície del material, que comporta la formació d'un biofilm capaç de protegir els bacteris de l'acció del sistema immunitari de l'hoste i del tractament amb antibiòtics. Aquesta tesi doctoral es basa en el desenvolupament de recobriments polimèrics antibacterians en titani per aplicacions dentals, buscant aconseguir mètodes ràpids i econòmics. Per tal d'assolir aquest objectiu, s'han desenvolupat, provat i comparat diferents estratègies per obtenir els recobriments. En la primera part de la tesi s'ha optimitzat un pretractament de la superfície del titani, per tal d'obtenir una superfície neta i millorar la reactivitat química de l'òxid de titani. El mètode seleccionat per l'activació ha estat l'activació per plasma, que permet eliminar els contaminants orgànics i augmentar l'energia superficial de les mostres tractades. Els polímers seleccionats per als recobriments han estat el polietilenglicol (PEG) i el 2-hidroxietilmetacrilat (PHEMA), que tenen propietats antifouling. Per preparar els recobriments de PEG s'han utilitzat tres mètodes diferents, la silanització, la polimerització per plasma i l'electrodeposició. Els tres mètodes han donat com a resultat una capa fina capaç de resistir l'adhesió bacteriana. Per altra banda, els recobriments amb PHEMA s'han preparat amb una nova metodologia, tractant el líquid amb un plasma jet. Els diversos recobriments s'han biofuncionalitzat per tal d'aconseguir una multifuncionalitat i millorar el seu funcionament. La combinació del PEG amb un pèptid d'adhesió cel·lular ha permès millorar l'adhesió de fibroblasts i mantenir les propietats antifouling del recobriment. La immobilització de pèptids antibacterians al PEG permet obtenir una superfície resistent a l'adhesió bacteriana i amb efecte antibacterià sobre els bacteris capaços d'adherir-se al recobriment. Per últim, la combinació de dos recobriments preparats per polimerització per plasma amb dos antibiòtics (vancomicina o doxiciclina) permet obtenir un sistema d'alliberació de fàrmacs a la superfície del titani.Postprint (published version

Immobilization of polymeric nano-assemblies for antibacterial applications

With conventional antibiotic therapies being increasingly ineffective, bacterial infections with subsequent biofilm formation represent a global threat to human health and therefore,new strategies to fight bacteria colonization need to be found. Coimmobilization of functional, nanosized assemblies broadens the possibility to engineer dually functionalized active surfaces with a nanostructured texture. Surfaces decorated with different nanoassemblies, such as micelles, polymersomes, or nanoparticles are in high demand for various applications ranging from catalysis, biosensing up to antimicrobial surfaces. In this thesis, I present a combination of bio-orthogonal and catalyst-free strain-promoted azide-alkyne click (SPAAC) and thiol-ene reactions to simultaneously coimmobilize various nanoassemblies; polymersome-polymersome and polymersome-micelle assemblies were selected. For the first time, the immobilization method using SPAAC reaction was studied in detail to attach soft, polymeric assemblies on a solid support. Together, the SPAAC and thiol-ene reactions successfully coimmobilized two unique self-assembled structures on the surfaces. Additionally, poly-(dimethylsiloxane) (PDMS)-based polymersomes were used as "ink" for direct immobilization from a PDMS-based microstamp onto a surface creating locally defined patterns. Furthermore, an active and a passive strategy based on polymeric micelles were combined to fight bacterial growth. The passive strategy involved covalent immobilization of polymeric micelles through Michael addition between maleimide exposed micelles and thiol functionalized surfaces. Compared to the bare surface, micelle-decorated surfaces showed reduced adherence and survival of bacteria. To extend this passive defense against bacteria with an active strategy, the immobilized micelles were equipped with the antimicrobial peptide KYE28 (KYEITTIHNLFRKLTHRLFRRNFGYTLR). The peptide interacted nonspecifically with the immobilized micelles where it retained its antimicrobial property. The successful surface decoration with KYE28 was demonstrated by a combination of X-ray photoelectron spectroscopy and quartz crystal microbalance with dissipation monitoring. The initial antimicrobial activity of the nanostructured surfaces against Escherichia coli (E. coli) was found to be increased by the presence of KYE28. Combining immobilization reactions has the advantage to attach any kind of nanoassembly pairs, resulting in surfaces with desired interfacial properties. Different nanoassemblies that encapsulate multiple active compounds coimmobilized on a surface will pave the way for the development of multifunctional surfaces with controlled properties and effciency. Additionally, the combination of our active and a passive strategy represents a straightforward modular approach that can easily be adapted, for example, by exchanging the antimicrobial peptide to optimize potency against challenging bacterial strains, and/or to simultaneously achieve antimicrobial and anti-infection properties

Electrospun collagen nanofibers for tissue engineering

Design and fabrication of the scaffold is an important part of the tissue engineering process. Nanofibrous scaffolds based on proteins are gaining increasing acceptance due to its structural similarity to the extracellular matrix. Making use of the electrospinning technique, rat tail collagen type I nanofibers were produced using a collagen in hexafluoroisopropanol (HFIP) solution. In addition to optimizing the electrospinning process parameters, the effect of humidity on fiber morphology and diameter was investigated for fiber size control for particular tissue engineering applications. A generalized humidity effect on polymer fiber diameter of the polymer solution electrospinning process was developed. The as spun collagen type I fibers were unstable in aqueous solutions. To impart stability these fibers, the technique of ion implantation was used. Both helium (He+) and nitrogen (N+) ions were used. Polychromatic ion beam of energies of 0 – 100 MeV (He+) and 0 – 300 MeV (N+) with doses varied from 4*1015 ions /cm2 - 1.2*1016 ions/cm2 were used. The effect of the ion implantation process on collagen fiber stability was investigated as a function of ion dosages. While all implantation conditions gave stable fibers, their swelling characteristics vary. The structural and chemical compositional changes in the stabilized collagen type I fibers were investigated using the X-ray photoelectron spectroscopy (XPS). The results indicated that the lowest dose of both the ion species implanted had the highest degree of crosslinking and retained the largest amount of nitrogen which is essential for cell adhesion and important for tissue engineering

Preparation, Physico-Chemical Properties and Biomedical Applications of Nanoparticles

Nowadays, the impact of nanotechnology on applications in medicine and biomedical sciences has broader societal and economic effects, enhancing awareness of the business, regulatory, and administrative aspects of medical applications. The selected papers included in the present Special Issue gives readers a critical, balanced and realistic evaluation of existing nanomedicine developments and future prospects, allowing practitioners to plan and make decisions.The topics of this book covers the use of nanoparticles and nanotechnology in medical applications including biomaterials for tissue regeneration, diagnosis and monitoring, surgery, prosthetics, drug delivery systems, nanocarriers, and wound dressing. I would like to express my gratitude to all contributors to this issue, who have given so much of their time and effort to help create this collection of high quality papers

Advances in Bioengineering

The technological approach and the high level of innovation make bioengineering extremely dynamic and this forces researchers to continuous updating. It involves the publication of the results of the latest scientific research. This book covers a wide range of aspects and issues related to advances in bioengineering research with a particular focus on innovative technologies and applications. The book consists of 13 scientific contributions divided in four sections: Materials Science; Biosensors. Electronics and Telemetry; Light Therapy; Computing and Analysis Techniques