Surface Anti-bacterial Adhesion Characteristics of TiO_2-coated PMMA

The anti-bacterial adhesion properties of TiO2-coated polymethyl methacrylate （PMMA） surfaces are investigated systematically. In detail, the adhesion of S. aureus （gram positive） and E. coli （gram negative） to TiO2-coated and uncoated PMMA surfaces are performed by the plate counting method. Afterwards, the adhesion free energy of bacteria on both supporting materials is quantified using the thermodynamic approach of Lifshitz van der Waals and acid/base interactions. The superior anti-adhesion capability of TiO2-coated PMMA is demonstrated when compared to native PMMA, both experimentally and theoretically.

Reducing bacterial adhesion to titanium surfaces using low intensity alternating electrical pulses

BACKGROUND Orthopedic implant-related infection remains one of the most serious complications after orthopedic surgery.In recent years,there has been an increased scientific interest to improve prevention and treatment strategies.However,many of these strategies have focused on chemical measures.AIM To analyze the effect of alternating current electrical fields on bacterial adherence to titanium surfaces.METHODS Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli)were exposed to 6.5 V electrical currents at different frequencies:0.5 Hz,0.1 Hz,and 0.05 Hz.After exposure,a bacterial count was then performed and compared to the control model.Other variables registered included the presence of electrocoagulation of the medium,electrode oxidation and/or corrosion,and changes in pH of the medium.RESULTS The most effective electrical model for reducing S.aureus adhesion was 6.5 V alternating current at 0.05 Hz achieving a 90%adhesion reduction rate.For E.coli,the 0.05 Hz frequency model also showed the most effective results with a 53%adhesion reduction rate,although these were significantly lower than S.aureus.Notable adhesion reduction rates were observed for S.aureus and E.coli in the studied conditions.However,the presence of electrode oxidation makes us presume these conditions are not optimal for in vivo use.CONCLUSION Although our findings suggest electrical currents may be useful in preventing bacterial adhesion to metal surfaces,further research using other electrical conditions must be examined to consider their use for in vivo trials.

<i>In Vitro</i>Evaluation of Bacterial Adhesion to Dental and Stainless-Steel Surfaces

This study aimed to describe the factors associated with biofilms formation in dental pathology by comparison of bacterial growth on dental and stainless-steel surfaces. We studied in vitro the behavior of Staphylococcus aureus Métis in order to observe the capacity of adhesion, to evaluate quantitatively the potential of proliferation and to compare the behavior of this germ in contact with the two surfaces. The biomaterials used were cylinders in Stainless steel (AISI 316L), dental fragments and stainless-steel fragments, all were disinfected for 15 minutes and then sterilized in a wet autoclave at 120˚C for 30 min. Macroscopic observation with a binocular magnifier of bacterial proliferation was carried out regularly after 6 h and 24 h of incubation. Observation by optical microscope based on GRAM staining made it possible to visualize the presence or absence of bacteria and to differentiate them. The adhesion of Staphylococcus aureus Méti S on dental fragments was compared to the one obtained on stainless steel fragments. We also carried a Bacterial count by optical dosing. The results show that the ability of this germ to colonize and develop biofilms on surfaces depends mainly on the characteristics of the surface. Rough surfaces as dental surface are more likely to developing biofilms than smooth surfaces like stainless-steel surface.

Materials and surface engineering to control bacterial adhesion and biofilm formation： A review of recent advances

Bacterial adhesion to surfaces and subsequent biofilm formation are a leading cause of chronic infections and biofouling. These processes are highly sensitive to environmental factors and present a challenge to research using traditional approaches with uncontrolled surfaces. Recent advances in materials research and surface engineering have brought exciting opportunities to pattern bacterial cell clusters and to obtain synthetic biofilms with well-controlled cell density and morphology of cell clusters. In this article, achievements in this field directions. we will review the recent and comment on the future

Controllable Protein Adsorption and Bacterial Adhesion on Polypyrrole Nanocone Arrays

In this research, polypyrrole nanocone arrays doped with β-Naphthalene sulphonic acid （PPy-NSA） were built. This film was expected to control protein adsorption and bacterial adhesion by potential-induced reversibly redox. The scanning Kelvin probe microscopy （SKPM） and surface contact angles （SCA） tests suggested that the surface potential and wettability of PPy-NSA nanocone arrays could be controlled by simply controlling its redox property via applying potential. The controllable surface potential and wettability in return controlled the adsorption of protein and adhesion of bacteria. The proposed material might find application in the preparation of smart biomaterial surfaces that can regulate proteins and bacterial adhesion by a simple potential switching.

Impact of Hierarchical Architecture of Cryptotermes brevis Wing on the Modulation of Bacterial Adhesion

The wing architecture is an inspiration to fabricate novel materials with exquisite properties.The current study characterizes the structure and biological function of a termite’s wing.The topography of the surface of the wing was studied by electron microscopy,and surface profilometer.The physicochemical property of the surface was analyzed by Fourier transform infrared spectroscopy,X-ray diffraction spectroscopy,energy-dispersive X-ray spectroscopy,and gas chromatography-mass spectrometry analysis of the epicuticle content.Water Contact Angle measurement confirmed the hydrophobicity of the wing surface.When microorganisms come in contact with the surface of the wing,they adhere to the wing surface due to cell surface properties of their own and the surface chemistry of the wing.The current study reported the adhesion behavior of two bacterial species.The bactericidal activity of the wing was confirmed by counting the bacterial cell viability and examination under a confocal laser scanning microscope.Adhesion of bacteria was observed under the electron microscope.Bacterial oxidative stress,the topography of the wing,and the surface chemistry of the wing are the crucial factors that induce bactericidal activity.The nanostructure along with the chemical composition of the wing can be mimicked for the fabrication of novel material with antibacterial properties.

Feasibility of a Chronic Foreign Body Infection Model Studying the Influence of TiO2 Nanotube Layers on Bacterial Contamination

Bacterial infections on the surface of medical devices are a significant problem in therapeutic approach, especially when implants are used in the living. In cardiology, pacemaker generator pocket surfaces, made in titanium alloy can be colonized by pathogen microorganism. This contamination represents a major risk of sepsis, endocarditis and localized infections for patients. A way to limit this bacterial contamination is to modify the surface topography using nano-structuration process of the titanium alloy surface of the implanted devices. The aim of this study is to evaluate the influence of TiO2 nanotube layers on bacterial infection in the living, considering the feasibility of an animal model of chronic foreign body infection. TiO2 nanotube layers prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution were implanted subcutaneously in Wistar rats. Three weeks after implantation, TiO2 implants were contaminated by a Staphylococcus epidermilis strain using two different concentrations at 106 and 108 colony forming unit (CFU) in order to induce a sufficient infection level and to avoid unwanted over infection consequences on rats health during the experiments. After 28 days in the living, 75% of nanotube layers initially submitted to the 108 CFU inoculum were contaminated while only 25% nanotube layers initially submitted to the 106 CFU inoculum remained infected. This significant result underlines the influence of TiO2 nanotube layers in decreasing the infection level. Our in vitro experiments showed that the synthesized TiO2 nanotubes indeed decreased the Staphylococcus epidermilis adhesion compared to unanodized Ti foil.

Synthesis of a new chitosan derivative and assay of Escherichia coli adsorption

A new chitosan derivative is prepared using chitosan.Ethyl chlorocarbonate was first introduced to the hydroxyl group of phthaloylchitosan through a nucleophilic reaction.Hydrazine was then added to recover the amino groups of chitosan and promote cross-linking.The structure of this new chitosan derivative was characterized by Fourier transform infrared（FT-IR）and proton nuclear magnetic resonance（1H NMR）spectroscopy,and its physical properties were determined by X-ray diffraction（XRD）,differential scanning calorimetry（DSC）,and thermogravimetric analysis（TGA）.The thermal and chemical stabilities of the new derivative were improved compared with those of native chitosan.Assay of Escherichia coli adhesion on a film based on this chitosan derivative showed good adsorption and biofilm formation.

Efficacy of Qingre Huashi decoction(清热化湿方) on infection of Helicobacter pylori:inhibiting adhesion,antioxidant,and anti-inflammation

OBJECTIVE: To investigate the phytochemical profile of Qingre Huashi decoction( 清 热 化 湿 方, QHD) and evaluate the mechanisms rationalizing the use of QHD against Helicobacter pylori(H. pylori)-associated gastritis. METHODS: QHD is composed of 11 herbs, which was prepared by a fixed Pharmacy and concentrated into clear paste. High-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry(HPLC-QTOF/MS) was used to detect the phytochemical profile of QHD. The toxicity of QHD against H. pylori and human gastric epithelial cells was evaluated by the toxicology test and cell counting kit-8 assay. The adhesion model was constructed by incubating H. pylori and gastric mucosal epithelial cells for 2 h. The urease assay was used to examine the antiadhesion effects of QHD, and gene expression of adhesins was evaluated by quantitative polymerase chain reaction. The antioxidant activity was assessed by DCFHDA labeling. To evaluate the anti-inflammatory effect, the levels of pro-inflammatory cytokines in the culture supernatant were detected by enzyme-linked immunosorbent assay. RESULTS: HPLC-QTOF/MS profiling indicated the presence of primary compounds 1-20 in QHD. Drug concentration was determined as 1, 2, and 5 mg/m L by the toxic concentration of QHD against H. pylori and human gastric epithelial cells. QHD prevented H. pylori adhesion to the human gastric epithelial cells and reduced levels of reactive oxygen species. QHD also reduced the level of interleukin-8 and other proinflammatory cytokines that were upregulated by H. pylori infection. CONCLUSION: QHD could inhibit H. pylori adhesion, and exert antioxidant and anti-inflammatory effects in vitro.

Antimicrobial-free knitted fabric as wound dressing and the mechanism of promoting infected wound healing

Fibrous biomaterials are widely used in the design and fabrication of antibacterial wound dressings.Two strategies are used to make anti-infective dressings:antibacterial and probiotic therapies,which have potential biotoxicity and other side-effects.Herein,we report a new strategy for fabricating wound dressings to combat infection.Poly(4-methyl-1-pentene)(PMP) fabric can remove bacteria from infectious wounds through dressing changes based on its efficient bacterial adhesion.The maximum adhered count of S.aureus and E.coli on the PMP fabric was 1.63 × 106CFU/cm~2 and 4.77 × 105CFU/cm~2,respectively.In addition,the PMP fabric could inhibit the twitching motility of bacteria,which is beneficial for inhibiting infection.The ability of the PMP fabric to accelerate wound healing was demonstrated in vivo in a rat wound model.After treatment with the PMP fabric dressing,pathogenic bacteria in the wound were removed through dressing change;therefore,the wound exhibited better healing speed than when the commercial dressing was used.The low bacterial concentration effectively stimulated the expression of growth factors and suppressed wound inflammation,thereby accelerating wound healing.PMP fabric has three advantages:(1) it has been approved for use in clinical treatment by the Food and Drug Administration;(2) no antibacterial agent or probiotics were used;(3) the fabric could be manufactured through an industrial production process.These results indicate that the new strategy can be used in the design of new-generation wound dressings for antibacterial applications.

Effects of cecropin-XJ on growth and adherence of oral cariogenic bacteria in vitro

Background CecropinXJ belongs to cecropinB, which is the most potent antibacterial peptide found naturally The aim of this study was to investigate the effects of cecropinXJ on growth and adherence of oral cariogenic bacteriaMethods Four oral cariogenic bacteria (Streptococcus mutans, Lactobacillus acidophilus, Actinomyces viscosus and Actinomyces naeslundii) were chosen for this experiment The minimal inhibitory concentrations (MICs) and reductive percent of bacterial growth were used to assay the antibacterial activity of cecropinXJ Mammalian cytotoxicity of cecropinXJ was tested with human periodontal membrane fibroblasts by tetrazolium (MTT) colorimetric assay The bacterial morphological changes induced by cecropinXJ were examined on scanning electron microscope (SEM) The influence of cecropinXJ on bacterial adhesion to salivacoated hydroxyapatite (SHA) was measured by scintillation countingResults The MICs of cecropinXJ for inhibition of the growth of four bacteria ranged from 40 to 428 μmol/L with the highest susceptible to A naeslundii and the lowest susceptible to L acidophilus At pH 68, 55 and 82, 1/2 MIC of cecropinXJ reduced the number of viable bacteria by 409%, 678% and 328% for S mutans and by 281%, 572% and 379% for L acidophilus The activities against Smutans and L acidophilus increased at pH 55 compared with pH 68 (P<001, respectively) In present of 50% saliva, 1/2 MIC of the peptide decreased the direct count of viable cells by 292% and 144% for S mutans and L acidophilus, respectively (P<001 and P>005, respectively), whereas almost no reduction counts were detected in the presence of 20% serum for both bacteria (P>005, respectively) Mammalian cytotoxicity of cecropinXJ from 10 to 100 μmol/L exhibited no cytotoxicity against human periodontal membrane fibroblasts (P>005) Bacterial morphological changes induced by MIC of cecropinXJ examined on SEM showed cell surface disruption Furthermore, the ability of A naeslundii adhesion to SHA decreased significantly with MIC of cecropinXJ for 10 and 20 minutes (P=0001 and 0000, respectively), and S mutans, A viscosus to SHA decreased significantly with MIC of cecropinXJ for 20 minutes( P=0000, respectively) Conclusions CecropinXJ exhibited bactericidal action against cariogenic pathogens, and the antibacterial activity enhanced in the acid environment The results also demonstrate that cecropinXJ prevents S mutans and actinomyces adsorption to SHA These findings suggest that CecropinXJ may have potential to prevent caries

Optical disassembly of cellular clusters by tunable ‘tug-of-war’ tweezers

Bacterial biofilms underlie many persistent infections,posing major hurdles in antibiotic treatment.Here we design and demonstrate‘tug-of-war’optical tweezers that can facilitate the assessment of cell–cell adhesion—a key contributing factor to biofilm development,thanks to the combined actions of optical scattering and gradient forces.With a customized optical landscape distinct from that of conventional tweezers,not only can such‘tug-of-war’tweezers stably trap and stretch a rod-shaped bacterium in the observing plane,but,more importantly,they can also impose a tunable lateral force that pulls apart cellular clusters without any tethering or mechanical movement.As a proof of principle,we examined a Sinorhizobium meliloti strain that forms robust biofilms and found that the strength of intercellular adhesion depends on the growth medium.This technique may herald new photonic tools for optical manipulation and biofilm study,as well as other biological applications.

Investigation of the relationship between cell surface hydrophobicity and demulsifying capability of biodemulsifier-producing bacteria

BACKGROUND： Cell surface hydrophobicity （CSH） is one of the key physicochemical features of biodemulsifier-producing bacteria that influence their demulsification capability maintenance in petroleum contaminated environments. METHODS： In present study, biodemulsifier-producing bacteria were isolated from petroleum contaminated environments using different isolation media and the correlation between their CSH and demulsifying ability was investigated. The demutsifying ability of isolates was measured through demulsification tests on water in kerosene emulsions. The microbial adhesion to the hydrocarbon （MATH） assay was used to denote their CSH. RESULTS： The evaluation of CSH showed that majority of biodemulsifier producing bacteria have high CSH which indicating a positive correlation between CSH and demulsifying capability. CONCLUSIONS： According to these results it can be concluded that CSH can be used as an indicator for assessment of biodemulsifier-producing bacteria and screening of new isolates for their biodemulsifier production.

Prevention of catheter-related Pseudomonas aeruginosa infection by levofloxacin-impregnated catheters in vitro and in vivo

Background Implanted medical catheter-related infections are increasing,hence a need for developing catheter polymers bonded to antimicrobials.We evaluated preventive effects of levofloxacin-impregnated catheters in catheterrelated Psuedomonas aeruginosa （strain PAO1） infection.Methods Drug release from levofloxacin-impregnated catheters was measured in vitro.Levofloxacin-impregnated catheters and polyvinyl chloride （PVC） catheters were immersed in 5 ml 50％ Luria Bertani medium containing 108 CFU/ml Pseudomonas aeruginosa then incubated for 6,12,24 or 48 hours at 37℃ when bacteria adhering to the catheters and bacteria in the growth culture medium were determined.Impregnated and PVC catheters were singly implanted subcutaneously in mice,50 μl （107CFU） of PAO1 was injected into catheters.After the first and fifth days challenge,bacterial counts on implanted catheters and in surrounding tissues were determined microbiologically.Bacterial colonization and biofilm formation on implanted catheters were assessed by scanning electron microscopy.Results Drug release from levofloxacin-impregnated catheters was rapid.Levofloxacin-impregnated catheters had significantly fewer bacteria compared to PVC in vitro.After first and fifth day of challenge,no or significantly fewer bacteria adhered to impregnated catheters or in surrounding tissues compared to PVC.Scanning electron microscopical images after first day displayed from none to significantly fewer bacteria adhering to impregnated implanted catheters,compared to bacteria and microcolonies adhering to PVC catheters.After the fifth day,no bacteria were found on impregnated catheters,compared to clusters surrounding mucus-like substance and coral-shaped biofilms with polymorphonuclear leukocyte on PVC catheters.After the first day of challenge,secretion occurred in all implanted catheters with surrounding tissues mildly hyperaemic and swollen.After the fifth day,minute secretions inside impregnated catheters and no inflammation in tissues,whereas purulent secretion inside PVC catheters and abscesses in surrounding tissues.Conclusion Levofloxacin-impregnated catheter is a promising new strategy for prevention of catheter-related Psuedomonas aeruginosa infection.

In vivo study on heparin/poly-L-lysine-copper coating for surface functionalization of ureteral stent

Polyurethane(PU)ureteral stents are used in clinics to maintain the ureteral patency.Due to biofilm formation and encrustation complications,long-term clinical usage has been limited.It is therefore necessary to develop an effective response to this unmet medical need.A heparin/poly-L-lysine/copper(NPs)coating was developed in our previous work that showed the effect of preventing infection and encrustation in vitro.In this work,a further study was conducted by grafting NPs on clinical ureteral stents that then were implanted into the infectious bladders of Wistar rats to investigate the effects of nanoparticles on bacterial growth and crystal deposition in vivo.It was found that decreased numbers of adherent microbes,urease amount splitting by bacteria,and deposited crystals were observed on the NPs stents with significant differences in comparison with PU stents.Besides,histological analysis showed that the NPs stents decreased the host tissue inflammation in close relation to the decrease biofilm formation and encrustation after 28 days of implantation.