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1. 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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2. Effect of Host Surface Factors on Biocompatible Adhesion Index

   https://doi.org/10.1007/978-3-030-86737-9_12  

   Boyd, James D; Grady, Martha E (December 2021, Springer International Publishing)

   Biofilm formation is a significant problem in America, accounting for 17 million infections, and causing 550,000 deaths annually. An understanding of factors that contribute to strong biofilm surface adhesion at implant interfaces can guide the development of surfaces that prevent deleterious biofilms and promote osseointegration. The aim of this research is to develop a metric that quantifies the adhesion strength differential between a bacterial biofilm and an osteoblast-like cell monolayer to a medical implant-simulant surface. This metric will be used to quantify the biocompatible effect of implant surfaces on bacterial and cell adhesion. The laser spallation technique employs a high-amplitude short-duration stress wave to initiate spallation of biological films. Attenuation of laser energy results in failure statistics across increasing fluence values, which are calibrated via interferometry to obtain interface stress values. Several metrology challenges were overcome including how membrane tension may influence laser spallation testing and how to determine stress wave characteristics when surface roughness precludes in situ displacement measurements via interferometry. Experiments relating loading region within biofilm to centroid of biofilm revealed that location played no role in failure rate. A reflective panel was implemented to measure stress wave characteristics on smooth and rough titanium, which showed no difference in peak compressive wave amplitude. After overcoming these metrology challenges, the adhesion strength of Streptococcus mutans biofilms and MG 63 monolayers on smooth and rough titanium substrates is measured. An Adhesion Index is developed by obtaining the ratio of cell adhesion to biofilm adhesion. This nondimensionalized parameter represents the effect of surface modifications on increases or decreases in biocompatibility. An increase in Adhesion Index value is calculated for roughened titanium compared to smooth titanium. The increase in Adhesion Index values indicates that the increase in surface roughness has a more positive biological response from MG 63 than does S. mutans. In this work further experiments quantifying impact of various surface coating including blood plasma, and adhesion proteins found within the extracellular matrix to expand the Adhesion Index. 

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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. An Overview of Biofilm Formation–Combating Strategies and Mechanisms of Action of Antibiofilm Agents

   https://doi.org/10.3390/life12081110  

   Asma, Syeda Tasmia; Imre, Kálmán; Morar, Adriana; Herman, Viorel; Acaroz, Ulas; Mukhtar, Hamid; Arslan-Acaroz, Damla; Shah, Syed Rizwan; Gerlach, Robin (August 2022, Life)

   Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate. 

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5. 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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