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1. Preconditioning Layers Affect Osteoblastic Cell Adhesion to Orthopedic Implant Surfaces

   https://doi.org/10.1007/978-3-031-17445-2_9  

   Boyd, James D; Grady, Martha E (November 2022, Springer International Publishing)

   Bacteria can proliferate orthopedic implants, resulting in infection rates as high as 5%. A consistent problem across implantology is the development of surfaces which successfully promote the adhesion and propagation of healthy fibroblast and osteoblast cells while deterring formation of bacterial biofilms. Selecting surface configurations which favor cell adhesion will lead to decreased infection rates. Progress in identifying appropriate surface configurations is hindered by the lack of quantitative adhesion techniques capable of comparing adhesion of cells and biofilms directly. Recent advancements in adhesion techniques have allowed for quantitatively measured adhesion strengths of both bacterial biofilms and cell monolayers using the laser spallation technique. The quantified stress-based adhesion values allow surface and environmental factors that modulate both bacterial and cell adhesion to implant surfaces to be evaluated. During implantation, blood propagates wound sites completely coating implant surfaces. Quantitatively determining the impact of preconditioning layers that accumulate on the implant surface on cell adhesion is vital to predict implant behavior. Previous work has demonstrated that these preconditioning layers either negatively or neutrally impact bacterial adhesion to titanium implant surfaces. This study focuses on the impact that blood plasma and fibronectin coatings have on the adhesion of osteoblastic (MG 63) cells and fibroblasts to the same titanium surfaces. Adhesion results indicate that preconditioning layers and increased surface roughness positively impact cell adhesion. Incorporating the increased adhesion values for cell adhesion into the Adhesion Index demonstrates that increased surface roughness, coupled with natural wound healing preconditioning of surfaces, yields positive biocompatibility. 

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2. Data: Sucrose-mediated formation and adhesion strength of Streptococcus mutans biofilms on titanium

   https://doi.org/10.18126/D1BG-NWTG  

   Butera, Tony; Waldman, Laura J.; Grady, Martha E. (January 2022, Materials Data Facility)

   Bacterial biofilms associated with implants remain a significant source of infections in dental, implant, and other healthcare industries due to challenges in biofilm removal. Biofilms consist of bacterial cells surrounded by a matrix of extracellular polymeric substance (EPS), which protects the colony from many countermeasures, including antibiotic treatments. Biofilm EPS composition is also affected by environmental factors. In the oral cavity, the presence of sucrose affects the growth of Streptococcus mutans that produce acids, eroding enamel and forming dental caries. Biofilm formation on dental implants commonly leads to severe infections and failure of the implant. This work determines the effect of sucrose concentration on biofilm EPS formation and adhesion of Streptococcus mutans, a common oral colonizer. Bacterial biofilms are grown with varying concentrations of sucrose on titanium substrates simulating dental implant material. Strategies for measuring adhesion for films such as peel tests are inadequate for biofilms, which have low cohesive strength and will fall apart when tensile loading is applied directly. The laser spallation technique is used to apply a stress wave loading to the biofilm, causing the biofilm to delaminate at a critical tensile stress threshold. Biofilm formation and EPS structures are visualized at high magnification with scanning electron microscopy (SEM). Sucrose enhanced the EPS production of S. mutans biofilms and increased the adhesion strength to titanium, the most prevalent dental implant material. However, there exists a wide range of sucrose concentrations that are conducive for robust formation and adhesion of S. mutans biofilms on implant surfaces. 

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3. Measuring Adhesion Strength of an Improved Dental Biofilm Model on a Titanium Surface

   https://doi.org/10.1007/978-3-031-17457-5_11  

   Hessin, M N; Boyd, J D; Grady, M E (November 2022, Springer International Publishing)

   Adhesion of bacteria to oral implant surfaces can lead to oral infections, and the prevention of strong biofilm adherence to implant surfaces can assist in the prevention of these infections like peri-implantitis. In prior studies, single species biofilm adhesion has been quantitatively measured via the laser spallation technique. However, colonizing oral biofilms rarely consists of a single bacteria species. Multiple early colonizer species, including several strains of Streptococci, dominate initial oral biofilm formation. This study aims to characterize the adhesion of a multi-species oral biofilm consisting of S. oralis, S. sanguinis, and S. gordonii on titanium, a common implant material, using the laser spallation technique. Previous work has established these specific Streptococci strains as a multi-species periodontal biofilm model. This study is the first to provide a quantitative adhesion measurement of this multi-species model onto a dental implant surface. First, adhesion strength of the multi-species model is compared to adhesion strength of the single-species streptococci constituents. Fluorescent staining and imaging by fluorescent microscopy are used to identify individual bacteria species within the biofilm. The multi-species biofilm presented in this study provides a more representative model of in vivo early biofilms and provides a more accurate metric for understanding biocompatibility on implant surfaces. 

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4. Impacts of hydrodynamic conditions and microscale surface roughness on the critical shear stress to develop and thickness of early‐stage Pseudomonas putida biofilms

   https://doi.org/10.1002/bit.28409  

   Wei, Guanju; Yang, Judy Q (July 2023, Biotechnology and Bioengineering)

   Abstract Biofilms can increase pathogenic contamination of drinking water, cause biofilm‐related diseases, alter the sediment erosion rate, and degrade contaminants in wastewater. Compared with mature biofilms, biofilms in the early‐stage have been shown to be more susceptible to antimicrobials and easier to remove. Mechanistic understanding of physical factors controlling early‐stage biofilm growth is critical to predict and control biofilm development, yet such understanding is currently incomplete. Here, we reveal the impacts of hydrodynamic conditions and microscale surface roughness on the development of early‐stagePseudomonas putidabiofilm through a combination of microfluidic experiments, numerical simulations, and fluid mechanics theories. We demonstrate that early‐stage biofilm growth is suppressed under high flow conditions and that the local velocity for early‐stageP. putidabiofilms (growth time < 14 h) to develop is about 50 μm/s, which is similar toP. putida's swimming speed. We further illustrate that microscale surface roughness promotes the growth of early‐stage biofilms by increasing the area of the low‐flow region. Furthermore, we show that the critical average shear stress, above which early‐stage biofilms cease to form, is 0.9 Pa for rough surfaces, three times as large as the value for flat or smooth surfaces (0.3 Pa). The important control of flow conditions and microscale surface roughness on early‐stage biofilm development, characterized in this study, will facilitate future predictions and managements of early‐stageP. putidabiofilm development on the surfaces of drinking water pipelines, bioreactors, and sediments in aquatic environments. 

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5. Targeting S. mutans biofilms: a perspective on preventing dental caries

   https://doi.org/10.1039/c9md00015a  

   Scharnow, Amber M.; Solinski, Amy E.; Wuest, William M. (July 2019, MedChemComm)

   The prevalence of biofilm diseases, and dental caries in particular, have encouraged extensive research on S. mutans biofilms, including methods of preventing its formation. Numerous small molecules with specific anti-biofilm activity against this pathogen have been isolated and synthesized. Generally, these molecules can be characterized into three categories: sucrose-dependent anti-adhesion, sucrose-independent anti-adhesion and cellular signaling interference. This review aims to provide an overview of the current small molecule strategies used for targeting S. mutans biofilms, and a perspective of the future for the field. 

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