Assembly of Cellulose Nanocrystal-Lysozyme Composite Films with Varied Lysozyme Morphology.

In modern society, there is a constant need for developing reliable, sustainable, and cost-effective antibacterial materials. Here, we investigate the preparation of cellulose nanocrystal (CNC)-lysozyme composite films via the well-established method of evaporation-induced self-assembly. We consider the effects of lysozyme concentration and aggregation state (native lysozyme, lysozyme amyloid fibers, and sonicated lysozyme amyloid fibers) on suspension aggregation and film-forming ability. Although at higher lysozyme loading levels (ca. 10 wt %), composite films lost their characteristic chiral nematic structuring, these films demonstrated improved mechanical properties and antibacterial activity with respect to CNC-only films, regardless of lysozyme aggregation state. We anticipate that the results presented herein could also contribute to the preparation of other CNC-protein-based materials, including films, hydrogels, and aerogels, with improved mechanical performance and antibacterial activity.

Nylon-6/chitosan core/shell antimicrobial nanofibers for the prevention of mesh-associated surgical site infection.

The state-of-the-art hernia meshes, used in hospitals for hernia repair, are predominantly polymeric textile-based constructs that present high mechanical strength, but lack antimicrobial properties. Consequently, preventing bacterial colonization of implanted prosthetic meshes is of major clinical relevance for patients undergoing hernia repair. In this study, the co-axial electrospinning technique was investigated for the development of a novel mechanically stable structure incorporating dual drug release antimicrobial action. Core/shell structured nanofibers were developed, consisting of Nylon-6 in the core, to provide the appropriate mechanical stability, and Chitosan/Polyethylene oxide in the shell to provide bacteriostatic action. The core/shell structure consisted of a binary antimicrobial system incorporating 5-chloro-8-quinolinol in the chitosan shell, with the sustained release of Poly(hexanide) from the Nylon-6 core of the fibers. Homogeneous nanofibers with a "beads-in-fiber" architecture were observed by TEM, and validated by FTIR and XPS. The composite nanofibrous meshes significantly advance the stress-strain responses in comparison to the counterpart single-polymer electrospun meshes. The antimicrobial effectiveness was evaluated in vitro against two of the most commonly occurring pathogenic bacteria; S. aureus and P. aeruginosa, in surgical site infections. This study illustrates how the tailoring of core/shell nanofibers can be of interest for the development of active antimicrobial surfaces.

Cell-Membrane-Inspired Silicone Interfaces that Mitigate Proinflammatory Macrophage Activation and Bacterial Adhesion.

Biofouling on silicone implants causes serious complications such as fibrotic encapsulation, bacterial infection, and implant failure. Here we report the development of antifouling, antibacterial silicones through covalent grafting with a cell-membrane-inspired zwitterionic gel layer composed of 2-methacryolyl phosphorylcholine (MPC). To investigate how substrate properties influence cell adhesion, we cultured human-blood-derived macrophages and Escherichia coli on poly(dimethylsiloxane) (PDMS) and MPC gel surfaces with a range of 0.5-50 kPa in stiffness. Cells attach to glass, tissue culture polystyrene, and PDMS surfaces, but they fail to form stable adhesions on MPC gel surfaces due to their superhydrophilicity and resistance to biofouling. Cytokine secretion assays confirm that MPC gels have a much lower potential to trigger proinflammatory macrophage activation than PDMS. Finally, modification of the PDMS surface with a long-term stable hydrogel layer was achieved by the surface-initiated atom-transfer radical polymerization (SI-ATRP) of MPC and confirmed by the decrease in contact angle from 110 to 20° and the >70% decrease in the attachment of macrophages and bacteria. This study provides new insights into the design of antifouling and antibacterial interfaces to improve the long-term biocompatibility of medical implants.

Nanostructured surface topographies have an effect on bactericidal activity.

BACKGROUND: Due to the increased emergence of antimicrobial resistance, alternatives to minimize the usage of antibiotics become attractive solutions. Biophysical manipulation of material surface topography to prevent bacterial adhesion is one promising approach. To this end, it is essential to understand the relationship between surface topographical features and bactericidal properties in order to develop antibacterial surfaces. RESULTS: In this work a systematic study of topographical effects on bactericidal activity of nanostructured surfaces is presented. Nanostructured Ormostamp polymer surfaces are fabricated by nano-replication technology using nanoporous templates resulting in 80-nm diameter nanopillars. Six Ormostamp surfaces with nanopillar arrays of various nanopillar densities and heights are obtained by modifying the nanoporous template. The surface roughness ranges from 3.1 to 39.1 nm for the different pillar area parameters. A Gram-positive bacterium, Staphylococcus aureus, is used as the model bacterial strain. An average pillar density at ~ 40 pillars µm-2 with surface roughness of 39.1 nm possesses the highest bactericidal efficiency being close to 100% compared with 20% of the flat control samples. High density structures at ~ 70 pillars µm-2 and low density structures at < 20 pillars µm-2 with surface roughness smaller than 20 nm reduce the bactericidal efficiency to almost the level of the control samples. CONCLUSION: The results obtained here suggests that the topographical effects including pillar density and pillar height inhomogeneity may have significant impacts on adhering pattern and stretching degree of bacterial cell membrane. A biophysical model is prepared to interpret the morphological changes of bacteria on these nanostructures.

Improved productivity of poly (4-hydroxybutyrate) (P4HB) in recombinant Escherichia coli using glycerol as the growth substrate with fed-batch culture.

BACKGROUND: The most successful polyhydroxyalkanoate (PHA) in medical applications is poly(4-hydroxybutyrate) (P4HB), which is due to its biodegradability, biocompatibility and mechanical properties. One of the major obstacles for wider applications of P4HB is the cost of production and purification. It is highly desired to obtain P4HB in large scale at a competitive cost. RESULTS: In this work, we studied the possibility to increase P4HB productivity by using high cell density culture. To do so, we investigated for the first time some of the most relevant factors influencing P4HB biosynthesis in recombinant Escherichia coli. We observed that P4HB biosynthesis correlated more with limitations of amino acids and less with nitrogen depletion, contrary to the synthesis of many other types of PHAs. Furthermore, it was found that using glycerol as the primary carbon source, addition of acetic acid at the beginning of a batch culture stimulated P4HB accumulation in E. coli. Fed-batch high cell density cultures were performed to reach high P4HB productivity using glycerol as the sole carbon source for cell growth and 4HB as the precursor for P4HB synthesis. A P4HB yield of 15 g L-1 was obtained using an exponential feeding mode, leading to a productivity of 0.207 g L-1 h-1, which is the highest productivity for P4HB reported so far. CONCLUSIONS: We demonstrated that the NZ-amines (amino acids source) in excess abolished P4HB accumulation, suggesting that limitation in certain amino acid pools promotes P4HB synthesis. Furthermore, the enhanced P4HB yield could be achieved by both the effective growth of E. coli JM109 (pKSSE5.3) on glycerol and the stimulated P4HB synthesis via exogenous addition of acetic acid. We have developed fermentation strategies for P4HB production by using glycerol, leading to a productivity of 0.207 g L-1 h-1 P4HB. This high P4HB productivity will decrease the total production cost, allowing further development of P4HB applications.

Tooth-Whitening with a Novel Phthalimido Peroxy Caproic Acid: Short Communication.

Professional tooth whitening in the dental office is a popular cosmetic procedure and is performed under carefully monitored conditions. This allows the controlled application of a relatively high concentration of bleaching ingredients based on hydrogen peroxide or peroxide derivatives which produce reactive oxygen species, and consequently induce enamel erosion, alteration of the microhardness of the teeth, irritation of the gums, pain or post bleach sensitivity. This short communication describes the successful and reliable application of a new professional tooth whitening technique using a novel phthalimido peroxycaproic acid complex while avoiding reactive oxygen species.

Poly(4-hydroxybutyrate) (P4HB) production in recombinant Escherichia coli: P4HB synthesis is uncoupled with cell growth.

BACKGROUND: Poly(4-hydroxybutyrate) (P4HB), belonging to the family of bacterial polyhydroxyalkanoates (PHAs), is a strong, flexible and absorbable material which has a large variety of medical applications like tissue engineering and drug delivery. For efficient production of P4HB recombinant Escherichia coli has been employed. It was previously found that the P4HB synthesis is co-related with the cell growth. In this study, we aimed to investigate the physiology of P4HB synthesis, and to reduce the total production cost by using cheap and widely available xylose as the growth substrate and sodium 4-hydroxybutyrate (Na-4HB) as the precursor for P4HB synthesis. RESULTS: Six different E. coli strains which are able to utilize xylose as carbon source were compared for their ability to accumulate P4HB. E. coli JM109 was found to be the best strain regarding the specific growth rate and the P4HB content. The effect of growth conditions such as temperature and physiological stage of Na-4HB addition on P4HB synthesis was also studied in E. coli JM109 recombinant in batch culture. Under the tested conditions, a cellular P4HB content in the range of 58 to 70% (w w(-1)) and P4HB concentrations in the range of 2.76 to 4.33 g L(-1) were obtained with a conversion yield (Y(P4HB/Na-4HB)) of 92% w w(-1) in single stage batch cultures. Interestingly, three phases were identified during P4HB production: the "growth phase", in which the cells grew exponentially, the "accumulation phase", in which the exponential cell growth stopped while P4HB was accumulated exponentially, and the "stagnation phase", in which the P4HB accumulation stopped and the total biomass remained constant. CONCLUSIONS: P4HB synthesis was found to be separated from the cell growth, i.e. P4HB synthesis mainly took place after the end of the exponential cell growth. High conversion rate and P4HB contents from xylose and precursor were achieved here by simple batch culture, which was only possible previously through fed-batch high cell density cultures with glucose.

Nanocomposites of cellulose nanofibers incorporated with carvacrol via stabilizing octenyl succinic anhydride-modified ɛ-polylysine.

Food packaging plays an extremely important role in the global food chain, allowing for products to be shipped across long distances without spoiling. However, there is an increased need to both reduce plastic waste caused by traditional single-use plastic packaging and improve the overall functionality of packaging materials to extend shelf-life even further. Herein, we investigate composite mixtures based on cellulose nanofibers and carvacrol via stabilizing octenyl-succinic anhydride-modified epsilon polylysine (MɛPL-CNF) for active food packaging applications. The effects of epsilon polylysine (εPL) concentration and modification with octenyl-succinic anhydride (OSA) and carvacrol are evaluated with respect to composites morphology, mechanical, optical, antioxidant, and antimicrobial properties. We find that both increased εPL concentration and modification with OSA and carvacrol lead to films with increased antioxidant and antimicrobial properties, albeit at the expense of reduced mechanical performance. Importantly, when sprayed onto the surface of sliced apples, MεPL-CNF-mixtures are able to successfully delay/hinder enzymatic browning, suggesting the potential of such materials for a range of active food packaging applications.

Imaging analysis of 1 138 supernumerary teeth by using cone-beam computed tomography.

OBJECTIVES: This study aims to analyze and summarize the characteristics of supernumerary teeth by using cone-beam computed tomography (CBCT). METHODS: A total of 718 patients with 1 138 supernumerary teeth were retrospectively collected. Age, gender, number, location, morphology, eruption status, and accompanying symptoms of the supernumerary teeth were statistically analyzed. The relationship relative to jaws, gender, and eruption status were analyzed and discussed. RESULTS: The average age of the patients was 9.54±5.32 years, and the male to female ratio was 2.88∶1. About 77.02% of the patients sought medical advice during the mixed dentition period, and 50.70% had one supernumerary tooth. These supernumeraries were most commonly conical in shape, and 85.76% of them were in the incisor region, 92.09% in the upper jaw, 46.75% in inverted position, and 86.20% unerupted. Overall, 65.29% of them had fully developed roots, and 60.63% had an impact on adjacent structures. Significant differences were found in eruption status, morphology, zoning, direction, root development, and impact on adjacent structures between the supernumerary teeth located in the upper and lower jaws (P<0.05). Significant differences were also detected in gender, morphology, zoning, orientation, root development, and impact on adjacent structures between erupted and unerupted teeth (P<0.05). The incidence of supernumerary teeth in the incisor region was higher in males than that in females. Moreover, the root of supernumeraries was more completely developed in males than in females (P<0.05). CONCLUSIONS: For supernumerary teeth, CBCT images can provide accurate three-dimensional radiographic data and are valuable for clinical diagnosis and treatment planning.

Chitosan -based nanoniosome for potential wound healing applications: Synergy of controlled drug release and antibacterial activity.

This study aims to develop a niosomal platform which can delivery drugs such as tetracycline hydrochloride (TCH) to treat bacterial infections in wounds. To this end, chitosan (CS) was used to obtain a controlled drug release and at the same time antibacterial activity. By design of experiments the niosome encapsulated TCH (TCH-Nio) were optimized for their particle size and encapsulation efficiency, followed by analysis of the release profile of TCH and stability of TCH-Nio and TCH-Nio@CS. The antibacterial activity and cytotoxicity of the fabricated nanoparticles were investigated as well. The release rate of TCH from TCH-Nio@CS in all conditions is less than TCH-Nio. In addition, higher temperature increases the release rate of drug from these formulations. The size, polydispersity index, and encapsulation efficacy of TCH-Nio and TCH-Nio@CS were more stable in 4 °C compared to 25 °C. TCH, TCH-Nio, and TCH-Nio@CS had MIC values of 7.82, 3.91, and 1.95 µg/mL for Escherichia coli, 3.91, 1.95, and 0.98 µg/mL for Pseudomonas aeruginosa, and 1.96, 0.98, and 0.49 µg/mL for Staphylococcus aureus, respectively. Coating of chitosan on niosome encapsulated TCH (TCH-Nio@CS) led to a reduced burst release of TCH from niosome (TCH-Nio), and enabled 2-fold higher antibacterial and anti-biofilm activity against the tested bacterial pathogens E. coli, P. aeruginosa and S. aureus, compared to the uncoated TCH-Nio, and 4-folder higher than the TCH solution, suggesting the synergetic effect of niosome encapsulation and chitosan coating. Moreover, the formulated niosomes displayed no in vitro toxicity toward the human foreskin fibroblast cells (HFF). Both TCH-Nio and TCH-Nio@CS were found to down-regulate the expression of certain biofilm genes, i.e., csgA, ndvB, and icaA in the tested bacteria, which might partially explain the improved antibacterial activity compared to TCH. The obtained results demonstrated that TCH-Nio@CS is capable of controlled drug release, leading to high antibacterial efficacy. The established platform of TCH-Nio@CS enlighten a clinic potential toward the treatment of bacterial infections in skin wounds, dental implants and urinary catheter.

Advanced antifouling and antibacterial hydrogels enabled by controlled thermo-responses of a biocompatible polymer composite.

To optimally apply antibiotics and antimicrobials, smart wound dressing conferring controlled drug release and preventing adhesions of biological objects is advantageous. Poly(N-isopropylacrylamide) (PNIPAAm), a conventional thermo-responsive polymer, and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), a typical antifouling polymer, have therefore potential to be fabricated as copolymers to achieve dual functions of thermo-responsiveness and antifouling. Herein, a hydrogel made of PNIPAM-co-PMPC was designed and loaded with octenidine, a widely applied antimicrobial agent for wound treatment, to achieve both antifouling and triggered drug release. The thermo-switch of the fabricated hydrogel allowed 25-fold more octenidine release at 37 °C (infected wound temperature) than at 30 °C (normal skin temperature) after 120 minutes, which led to at least a 3 lg reduction of the viable bacteria at 37 °C on artificially infected wounds. Furthermore, we pioneeringly assessed the antifouling property of the material in PBS buffer using single molecule/cell/bacterial force spectroscopy, and revealed that the fabricated hydrogel displayed distinctive antifouling properties against proteins, mammalian cells, and bacteria. This work demonstrated a promising design of a hydrogel applicable for preventing and treating wound infections. The concept of dual-functional materials can be envisaged for other clinical applications related to the prevention of biofilm-associated infections, such as urinary catheters, stents, and dental implants.

Uncoupling bacterial attachment on and detachment from polydimethylsiloxane surfaces through empirical and simulation studies.

Bacterial infections related to medical devices can cause severe problems, whose solution requires in-depth understanding of the interactions between bacteria and surfaces. This work investigates the influence of surface physicochemistry on bacterial attachment and detachment under flow through both empirical and simulation studies. We employed polydimethylsiloxane (PDMS) substrates having different degrees of crosslinking as the model material and the extended Derjaguin - Landau - Verwey - Overbeek model as the simulation method. Experimentally, the different PDMS materials led to similar numbers of attached bacteria, which can be rationalized by the identical energy barriers simulated between bacteria and the different materials. However, different numbers of residual bacteria after detachment were observed, which was suggested by simulation that the detachment process is determined by the interfacial physicochemistry rather than the mechanical property of a material. This finding is further supported by analyzing the bacteria detachment from PDMS substrates from which non-crosslinked polymer chains had been removed: similar numbers of residual bacteria were found on the extracted PDMS substrates. The knowledge gained in this work can facilitate the projection of bacterial colonization on a given surface.

Factor XIII Cross-Linked Adhesive Chitosan Hydrogels.

Biomedical adhesives have been found to be an attractive alternative to suturing in several circumstances. However, to date most of the clinically approved formulations are based on synthetic and highly reactive toxic chemicals. In this work, we aimed to combine for the first time the bioactive properties of the cationic polysaccharide chitosan and its intrinsic electrostatic binding to negatively charged tissues with the biocompatible and clinically compliant enzymatic cross-linking scheme of fibrin glue. This synergistic activity led to the generation of a transglutaminase Factor XIII cross-linkable chitosan formulation with fast gelation kinetics, tunable mechanical properties, antibacterial activity, and strong adhesion to cartilage.

Bioresponsive Hybrid Nanofibers Enable Controlled Drug Delivery through Glass Transition Switching at Physiological Temperature.

To avoid excessive usage of antibiotics and antimicrobial agents, smart wound dressings permitting controlled drug release for treatment of bacterial infections are highly desired. In search of a sensitive stimulus to activate drug release under physiological conditions, we found that the glass transition temperature (Tg) of a polymer or polymer blend can be an ideal parameter because a thermal stimulus can regulate drug release at the physiological temperature of 37 °C. A well-tuned Tg for a controlled drug release from fibers at 37 °C was achieved by varying the blending ratio of Eudragit® RS 100 and poly(methyl methacrylate). Octenidine, an antimicrobial agent often used in wound treatment, was encapsulated into the polymer blend during the electrospinning process and evaluated for its controlled release based on modulation of temperature. The thermal switch of the nanofibrous membranes can be turned "on" at physiological temperature (37 °C) and "off" at room temperature (25 °C), conferring a controlled release of octenidine. It was found that octenidine can be released in an amount at least 8.5 times higher (25 mg·L-1) during the "on" stage compared to the "off" stage after 24 h, which was regulated by the wet Tg (34.8-36.5 °C). The "on"/"off" switch for controlled drug release can moreover be repeated at least 5 times. Furthermore, the fabricated nanofibrous membranes displayed a distinctive antibacterial activity, causing a log3 reduction of the viable cells for both Gram negative and positive pathogens at 37 °C, when the thermal switch was "on". This study forms the groundwork for a treatment concept where no external stimulus is needed for the release of antimicrobials at physiological conditions, and will help reduce the overuse of antibiotics by allowing controlled drug release.

Enatiomerically pure hydroxycarboxylic acids: current approaches and future perspectives.

The growing awareness of the importance of chirality in conjunction with biological activity has led to an increasing demand for efficient methods for the industrial synthesis of enantiomerically pure compounds. Polyhydroxyalkanotes (PHAs) are a family of polyesters consisting of over 140 chiral R-hydroxycarboxylic acids (R-HAs), representing a promising source for obtaining chiral chemicals from renewable carbon sources. Although some R-HAs have been produced for some time and certain knowledge of the production processes has been gained, large-scale production has not yet been possible. In this article, through analysis of the current advances in production of these acids, we present guidelines for future developments in biotechnological processes for R-HA production.

Antibacterial, Cytocompatible, Sustainably Sourced: Cellulose Membranes with Bifunctional Peptides for Advanced Wound Dressings.

Progressive antibiotic resistance is a serious condition adding to the challenges associated with skin wound treatment, and antibacterial wound dressings with alternatives to antibiotics are urgently needed. Cellulose-based membranes are increasingly considered as wound dressings, necessitating further functionalization steps. A bifunctional peptide, combining an antimicrobial peptide (AMP) and a cellulose binding peptide (CBP), is designed. AMPs affect bacteria via multiple modes of action, thereby reducing the evolutionary pressure selecting for antibiotic resistance. The bifunctional peptide is successfully immobilized on cellulose membranes of bacterial origin or electrospun fibers of plant-derived cellulose, with tight control over peptide concentrations (0.2 ± 0.1 to 4.6 ± 1.6 µg mm-2 ). With this approach, new materials with antibacterial activity against Staphylococcus aureus (log4 reduction) and Pseudomonas aeruginosa (log1 reduction) are developed. Furthermore, membranes are cytocompatible in cultures of human fibroblasts. Additionally, a cell adhesive CBP-RGD peptide is designed and immobilized on membranes, inducing a 2.2-fold increased cell spreading compared to pristine cellulose. The versatile concept provides a toolbox for the functionalization of cellulose membranes of different origins and architectures with a broad choice in peptides. Functionalization in tris-buffered saline avoids further purification steps, allowing for translational research and multiple applications outside the field of wound dressings.

Use of extracellular medium chain length polyhydroxyalkanoate depolymerase for targeted binding of proteins to artificial poly[(3-hydroxyoctanoate)-co-(3-hydroxyhexanoate)] granules.

Polyhydroxyalkanoates (PHA), which are produced by many microorganisms, are promising polymers for biomedical applications due to their biodegradability and biocompatibility. In this study, we evaluated the suitability of medium chain length (mcl) PHA as surface materials for immobilizing proteins. Self-stabilized, artificial mcl-PHA beads with a size of 200-300 nm were fabricated. Five of six tested proteins adsorbed nonspecifically to mcl-PHA beads in amounts of 0.4-1.8 mg m(-2) bead surface area. The binding capacity was comparable to similar-sized polystyrene particles commonly used for antibody immobilization in clinical diagnostics. A targeted immobilization of fusion proteins was achieved by using inactive extracellular PHA depolymerase (ePHA(mcl)) from Pseudomonas fluorescens as the capture ligand. The N-terminal part of ePhaZ(MCL) preceding the catalytic domain was identified to comprise the substrate binding domain and was sufficient for mediating the binding of fusion proteins to mcl-PHA. We suggest mcl-PHA to be prime candidates for both nonspecific and targeted immobilization of proteins in applications such as drug delivery, protein microarrays, and protein purification.

Bacterial Adhesion on Soft Materials: Passive Physicochemical Interactions or Active Bacterial Mechanosensing?

The influence of mechanical stiffness of biomaterials on bacterial adhesion is only sparsely studied and the mechanism behind this influence remains unclear. Here, bacterial adhesion on polydimethylsiloxane (PDMS) samples, having four different degrees of stiffness with Young's modulus ranging from 0.06 to 4.52 MPa, is investigated. Escherichia coli and Pseudomonas aeruginosa are found to adhere in greater numbers on soft PDMS (7- and 27-fold increase, respectively) than on stiff PDMS, whereas Staphylococcus aureus adheres in similar numbers on the four tested surfaces. To determine whether the observed adhesion behavior is caused by bacteria-specific mechanisms, abiotic polystyrene (PS) beads are employed as bacteria substitutes. Carboxylate-modified PS (PS-COOH) beads exhibit the same adhesion pattern as E. coli and P. aeruginosa with four times more adhered beads on soft PDMS than on stiff PDMS. In contrast, amine-modified PS (PS-NH2 ) beads adhere in similar numbers on all tested samples, reminiscent of S. aureus adhesion. This work demonstrates for the first time that the intrinsic physicochemical properties associated with PDMS substrates of different stiffness strongly influence bacterial adhesion and challenge the previously reported theory on active bacterial mechanosensing, which provides new insights into the design of antifouling surfaces.

Substrate viscosity plays an important role in bacterial adhesion under fluid flow.

Many materials used in the medical settings such as catheters and contact lenses as well as most biological tissues are not purely elastic, but rather viscoelastic. While substrate elasticity has been investigated for its influence on bacterial adhesion, the impact of substrate viscosity has not been explored. Here, the importance of considering substrate viscosity is explored by using polydimethylsiloxane (PDMS) as the substrate material, whose mechanical properties can be tuned from predominantly elastic to viscous by varying cross-linking degree. Interfacial rheology and atomic force microscopy analysis prove that PDMS with a low cross-linking degree exhibits both low stiffness and high viscosity. This degree of viscoelasticity confers to PDMS a remarkable stress relaxation, a good capability to deform and an increased adhesive force. Bacterial adhesion assays were conducted under flow conditions to study the impact of substrate viscosity on Escherichia coli adhesion. The viscous PDMS not only enhanced E. coli adhesion but also conferred greater resistance to desorption against shear stress at air/liquid interface, compared to the PDMS with high crosslinking degree. These findings highlight the importance to consider substrate viscosity while studying bacterial adhesion. The current work provides new insights to an improved understanding of how bacteria interact with complex viscoelastic environments.

Beneficial Oral Biofilms as Smart Bioactive Interfaces.

Periodontitis is a very common health problem caused by formation of pathogenic bacterial biofilm that triggers inflammation resulting in either reversible gingivitis or irreversible periodontal hard and soft tissue damages, leading to loss of teeth when left untreated. Commensal bacteria play an important role in oral health in many aspects. Mainly by colonizing oral tissues, they (i) contribute to maturation of immune response, and (ii) foreclose attachment of pathobiont and, therefore, prevent from infection. The main goal of the study was to investigate if blocking of receptors on a commensal biofilm can prevent or reduce the attachment of pathogenic strains. To do so, biofilm produced by commensal Streptococcus sanguinis was treated with whole cell lysate of pathobionts Fusobacterium nucleatum or Porphyromonas gingivalis, followed by incubation with respective strain(s). The study revealed significant reduction in pathobiont adhesion to lysate-treated commensal biofilm. Therefore, adhesion of pathobionts onto the lysate-blocked biofilm was hindered; however, not completely eliminated supporting the idea that such approach in the oral cavity would benefit the production of a well-balanced and healthy bioactive interface.