Profiling to Probing: Atomic force microscopy to characterize nano-engineered implants

Surface modification of implants in the nanoscale or implant nano-engineering has been recognized as a strategy for augmenting implant bioactivity and achieving long-term implant success. Characterizing and optimizing implant characteristics is crucial to achieving desirable effects post-implantation. Modified implant enables tailored, guided and accelerated tissue integration; however, our understanding is limited to multicellular (bulk) interactions. Finding the nanoscale forces experienced by a single cell on nano-engineered implants will aid in predicting implants’ bioactivity and engineering the next generation of bioactive implants. Atomic force microscope (AFM) is a unique tool that enables surface characterization and understanding of the interactions between implant surface and biological tissues. The characterization of surface topography using AFM to gauge nano-engineered implants' characteristics (topographical, mechanical, chemical, electrical and magnetic) and bioactivity (adhesion of cells) is presented. A special focus of the review is to discuss the use of single-cell force spectroscopy (SCFS) employing AFM to investigate the minute forces involved with the adhesion of a single cell (resident tissue cell or bacterium) to the surface of nano-engineered implants. Finally, the research gaps and future perspectives relating to AFM-characterized current and emerging nano-engineered implants are discussed towards achieving desirable bioactivity performances. This review highlights the use of advanced AFM-based characterization of nano-engineered implant surfaces via profiling (investigating implant topography) or probing (using a single cell as a probe to study precise adhesive forces with the implant surface)

Latest Trends in Surface Modification for Dental Implantology: Innovative Developments and Analytical Applications

An increase in the world population and its life expectancy, as well as the ongoing concern about our physical appearance, have elevated the relevance of dental implantology in recent decades. Engineering strategies to improve the survival rate of dental implants have been widely investigated, focusing on implant material composition, geometry (usually guided to reduce stiffness), and interface surrounding tissues. Although efforts to develop different implant surface modifications are being applied in commercial dental prostheses today, the inclusion of surface coatings has gained special interest, as they can be tailored to efficiently enhance osseointegration, as well as to reduce bacterial-related infection, minimizing peri-implantitis appearance and its associated risks. The use of biomaterials to replace teeth has highlighted the need for the development of reliable analytical methods to assess the therapeutic benefits of implants. This literature review considers the state-of-the-art strategies for surface modification or coating and analytical methodologies for increasing the survival rate for teeth restoration.Ministerio de Ciencia e Innovación PID2019-109371GB-I00Junta de Andalucía PAIDI 2020, P20_00671Universidad de Sevilla US-1380878, PPI505/2020, PPI532/202

Anti-bacterial and Anti-adhesive Nanostructured Coatings for Improved Implant Biocompatibility

In this thesis, new coatings against bacterial adhesion and protein adsorptionwere developed, characterized and their effectiveness against bacterial adhesion and protein adsorption was investigated. Two strategies were followed to resist the bacterial adhesion. The first one is based on designing of high-ordered nanostructured polymer features while the second one concern with construction of polymer loaded with anti-bacterial agents. Reduction of protein adsorption is the second aim of this thesis. To achieve this goal, ultra-thin films with nano-scaled topography were manufactured

Differentiation of Bone Marrow Derived Mesenchymal Stem Cells (BM-MSCs) Using Engineered Nanofiber Substrates

Ph.DDOCTOR OF PHILOSOPH

Bio-mimetic multimodal nanostructured surfaces fabricated with self-assembling biopolymer and its applications

Nanotechnology will revolutionize the industrial world in 21st century. Almost every country has invested in research to unfold the mysteries of nanomaterials and for their applications. A major driving force of nanomaterial research is through the imitation of living system and materials, also known as biomimetics. Polymeric biomaterials have a critical role in the advancement of medicine and sustainable green materials. In this dissertation I demonstrate the roles that the polysaccharide biopolymer chitin has as the major structural component of the arthropod cuticle and the potential that chitin has as a versatile component to novel biomaterial applications. Chitin is a polysaccharide that is a polymer of N-acetylglucosamine, chitin is the second most abundant biopolymer on the planet and a primary component of insect, arthropod and fungal exoskeletons/cuticles. Various factors contribute to the mechanical properties of an insect cuticle including cuticle thickness and composition. In my dissertation research I have also shown that nanoscale chitin polymer alignment may be another factor that contributes to the optical, surface, and mechanical properties of a cuticle. Purified chitin self-assembles into 20 nm chitin nanofibers that serve as the foundation for all higher order chitin structures in the cuticles of insects and other arthropods via interactions with structural cuticle proteins. In addition to this I have also demonstrated that purified chitin and its deacetylated form of chitosan have great potential as a substrate for many nanofabrication technique and thus provide a new and novel material in place of traditional synthetic polymers. In my dissertation is shown that the chitin and chitosan have great potential as the substrate for nanosphere lithography for the production of the generation of flexible antimicrobial and antifogging nanostructured surfaces. Metal nanoparticles are critical for many application and industrial processes, however the methods needed for their synthesis often are energy intensive and environmentally unfriendly. I demonstrate that chitin and chitosan are powerful tools for the green synthesis of metal nanoparticles. While arthropod cuticles are traditional examples for bio-mineralization and bio-metalization, I have found that a primary component of these process is due in fact to chitin and I use chitin to develop a novel class of composite nanomaterial which has important implications for a broad range of applications including antimicrobial surfaces, bioremediation, and cell scaffolds for biomedical engineering and regenerative medicine

An investigation of cell responses to mechanical environment

With the development of in vitro systems for tissue engineering, various substrates and mechanical stimuli have been utilized to modulate the cell behavior. It’s known that various micropatterns have been fabricated and applied to regulate cell adhesion, morphology and function. Micropatterns created by standard photolithography process are usually rectangular channels with sharp corners (microgrooves) which provide limited control over cells and are not favorable for cell-cell interaction and communication. We propose a new micropattern with smooth wavy surfaces (micro-waves) to control the position and orientation of cells. Results showed that cells adhered to the wavy surface displayed both improved alignment and adhesion strength compared to those on the flat surface. Shear flow was further applied to examine the cell adhesion response to the flow. In recent years, nanoparticles (NPs) have gained increasing interest due to its potential use as drug delivery, imaging and diagnostic agents in pharmaceutical and biomedical applications. While lots of cells in vivo are under mechanical forces, little is known about the correlation of the mechanical stimulation and the internalization of NPs into cells. We investigate the effects of applied cyclic strain on NPs uptake by bovine aortic endothelial cells (BAECs). The cyclic strain results in a significant enhancement in NP uptake which increases almost linearly with strain level. In my study, micro-patterned substrates, shear flow and cyclic strain have been applied to investigate the cell behavior including cell alignment, cell spreading, cell adhesion and cellular uptake of NPs. Studies of cells response to these mechanical stress promote our current understanding of how cells sense and response to their mechanical environment

Study and development of new biodegradable polymeric materials carrying bioactive drugs.

206 p.Cada vez hay más patógenos resistentes ante agentes antimicrobianos. Por ello, es indispensable desarrollar nuevas estrategias para hacer frente a este problema. Una estrategia interesante es la de combinar fármacos con polímeros biodegradables, en forma de hidrogeles, superficies o nanosistemas. Además, los agentes antimicrobianos no se limitan a los antibióticos, ya que hay diversos metales y compuestos naturales que han demostrado ser útiles contra varios patógenos.En esta tesis se han desarrollado tres propuestas. Por una parte, hidrogeles formados por quitosano y poli(vinil alcohol), eficaces para liberación de fármacos. Estos hidrogeles termosensibles inyectables se han cargado con partículas de vidrio bioactivo, mejorando sus propiedades mecánicas y su bioactividad respecto a la formación y regeneración ósea.También se han estudiado dos mezclas polímero/fármaco. Se han buscado mezclas miscibles con el objetivo de crear dispersiones sólidas amorfas, pudiendo así mantener los fármacos cristalinos en forma amorfa dentro de una matriz polimérica, Las mezclas estudiadas han sido poli(¿-caprolactona)/xanthohumol y poli(¿-caprolactona)/ácido micofenólico. Además de confirmar la miscibilidad de ambas mezclas, se han estudiado otras propiedades y beneficios para la salud que podrían tener estas mezclas aparte de su función antibacteriana.Polyma

Development Of Hybrid Coating Materials To Improve The Success Of Titanium Implants

While titanium (Ti) and its alloys have become ubiquitous within implantology as materials to restore or augment the function of human tissues, their success is plagued by complications associated with infection and aseptic implant loosening. These two risks account for the majority of implant failures in the clinic and limit the long-term success of titanium implants in vivo. Therefore, this thesis describes the development of robust multifunctional class II organic-inorganic hybrid coating materials for titanium implants that could be used to effectively target both complications, concurrently. During this master’s work, two different coating systems were examined. First, class II hybrid coating materials composed of chitosan and silica loaded with silver nanoparticles were investigated. These coatings displayed a high resistance to fracture, great substrate adhesion and inhibited the growth of two clinically relevant pathogenic bacteria (E. coli and S. aureus) in both biofilm and planktonic cultures. Secondly, a novel class II hybrid coating material was developed that was composed of polyethylene glycol, calcium, and silica and loaded with silver nanoparticles. This hybrid bioactive glass material possessed similar mechanical and antimicrobial properties to the chitosan-silica coatings and displayed an increased bioactive response. From this study, a better understanding of the feasibility of class II hybrid materials as implant coatings was developed. The work presented in this work may afford a novel strategy in improving the success of implants for biomedical applications

Nanodiamond particles for biomacromolecule immobilization and dye contaminant adsorption

Nanodiamond (ND) has become a widely studied material in recent years due to its excellent properties, which includes high specific surface area, oxygen-containing surface groups (desirable for physical or chemical functionalization), physically and chemically inert diamond core, optical transparency, and biocompatibility. ND has been found to be biocompatible and have no cytotoxicity to cells. To date, significant attention has been focused on utilizing ND material as a platform for biomacromolecule immobilization which is promising for biological applications such as biosensor. Moreover, excellent surface properties of ND might be able to make it a desirable adsorbent material. The present thesis work has focused on using ND for biomacromolecule immobilization as well as dye contaminant adsorption. First, the immobilization of an important biomacromolecule, carboxymethyl chitosan, onto ND surface as well as the properties of the product was investigated in detail. The carboxymethyl chitosan modified ND (NDCMCS) shows improved dispersity especially in low and high pH aqueous solutions. Moreover, the rich content of primary amine and hydroxyl on CMCS backbone would render further physical or chemical functionalization of ND more flexible and versatile. The following work is then focusing on the protein adsorption behaviors onto ND surface as well as whether protein could retain its structural features upon immobilization. To this end, bovine serum albumin (BSA) was chosen as a model protein for the study of protein conformation and the interaction between ND and protein in their complex. The results have demonstrated that ND is an excellent platform for protein immobilization with high affinity and approximately 80% of BSA structural features could be preserved upon immobilization. Second, based on strong ND-protein interaction, the assembly of ND-protein complex into macroscale material in a Layer-by-Layer (LBL) assembly fashion has been studied. The LBL assembly properties of ND-BSA complex with pristine ND were investigated on glass substrates. The ND-BSA/ND coatings fabricated by LBL assembly method were stable and more densely-organized coating structures could be obtained by increasing the number of bilayers deposited. The LBL assembly method for ND-protein coating fabrication could be easily employed to prepare biomacromolecule-functionalized ND films for biosensor applications. In the following work, it was found that NDs could also assemble into thin films through hydrogen bonding on a glass substrate. The films prepared have regularly-organized nanostructures, which could be tuned by adjusting the number of bilayers deposited. Moreover, the oxygen-containing surface groups on LBL films make possible the further functionalization by chemical or physical approach. Finally, the excellent surface properties of ND have found new promising applications in addressing current environmental issues and ND has been demonstrated to be an effective dye contaminant adsorbent. In this work, the adsorption of azo dye acid orange 7 (AO7) onto ND surface has been investigated in order to ascertain the adsorption behavior as well as the interaction involved in the adsorption process, where ND has been proved to have higher capacity in azo dye adsorption than widely used activated carbons and carbon nanotubes. Due to strong π-donor-acceptor interaction between ND surface graphite layer and azo bond, ND shows high affinity with azo dye. Though affinity is slightly lower at high pH values, the adsorption coefficients of ND with AO7 at neutral to alkaline pHs are still of the same orders of magnitude with those of low pH values, suggesting that ND could be a desirable candidate for textile wastewater treatment which is normally at alkaline pH. The present thesis work might potentially contribute to utilizing NDs for biological and environmental applications

Coatings Imparting Multifunctional Properties to Materials

Coatings are traditionally used to protect materials from corrosion and erosion and improve the equipment’s performance. At present, there are coatings that provide materials with new properties, for example, biocidal, hydrophobic and self-cleaning properties. A promising area of materials science is the development of "smart" coatings that simultaneously give materials several new properties. The coating propertiess are determined by the coatings’ material, the structure and the properties of the substrate surface, and the methods of forming the coatings. This book contains the results of the latest research on the formation of coatings that impart complexes of new properties to various materials