Biofilm Deposition Research Articles

Effects of theobromine addition on chemical and mechanical properties of a conventional glass ionomer cement

In vitro effect of 1% theobromine addition on the physical and chemical properties of conventional glass ionomer (GIC) cement was investigated. Conventional GIC (GIC-C) and 1% theobromine added to GIC (GIC-THEO) specimens were compared regarding the microhardness (n = 10), sorption (n = 5), solubility (n = 5), color change (n = 10), fluoride release in saliva (n = 10) and the amount of biofilm deposition (n = 20). Compared against conventional GIC, adding 1% theobromine increased microhardness (p < 0.05), while its sorption, solubility, color and fluoride release to saliva (p > 0.05) remained unchanged. On the other hand, Streptococcus mutans biofilm amount deposited on its surface decreased statistically when theobromine was added to GIC (p < 0.05). Based on the results, it could be concluded that 1% theobromine addition to GIC can be a good strategy as it keeps some of its properties and improves microhardness and biofilm deposits strengthening its role in the preventive approach of dentistry.

Duodenoscope-Associated Infections: Update on an Emerging Problem.

The duodenoscope is among the most complex medical instruments that undergo disinfection between patients. Transmission of infection by contaminated scopes has remained a challenge since its inception. Notable risk factors for pathogen transmission include non-adherence to disinfection guidelines, encouragement of biofilm deposition due to complex design and surface defects and contaminated automated endoscope reprocessors. The most common infections following endoscopy are endogenous infections involving the patient's own gut flora. Exogenous infections, on the other hand, are associated with contaminated scopes and can theoretically be prevented by effective reprocessing. Pseudomonas aeruginosa is currently the most common organism isolated from contaminated endoscopes. Of note, reports of multidrug-resistant duodenoscopy-associated outbreaks have surfaced recently, many of which occurred despite adequate reprocessing. The FDA and CDC currently recommend comprehensive cleaning followed with at least high-level disinfection for reprocessing of flexible GI endoscopes. Reports of duodenoscope-related outbreaks despite compliance with established guidelines have prompted professional and government bodies to revisit existing guidelines and offer supplementary recommendations for duodenoscope processing. For the purposes of this review, we identified reports of duodenoscope-associated infections from 2000 till date. For each outbreak, we noted the organisms isolated, the number of cases reported, any possible explanations of contamination, and the measures undertaken to end each outbreak. We have also attempted to present an overview of recent developments in this rapidly evolving field.

Effect of sequential UV/free chlorine disinfection on opportunistic pathogens and microbial community structure in simulated drinking water distribution systems

Drinking water distribution systems (DWDS) may be a “Trojan Horse” for some waterborne diseases caused by opportunistic pathogens (OPs). In this study, two simulated DWDS inoculated with groundwater were treated with chlorine (Cl2) and ultraviolet/chlorine (UV/Cl2) respectively to compare their effects on the OPs distributed in four different phases (bulk water, biofilms, corrosion products, and loose deposits) of DWDS. 16S rRNA genes sequencing and qPCR were used to profile microbial community and quantify target genes of OPs, respectively. Results showed that UV/Cl2 was more effective than single Cl2 to control the regrowth of OPs in the water with the same residual chlorine concentration. However, the OPs inhabiting the biofilms, corrosion products, and loose deposits seemed to be tolerant to UV/Cl2 and Cl2, demonstrating that OPs residing in these phases were resistant to the disinfection processes. Some significant microbial correlations between OPs and Acanthamoeba were found by Spearman correlative analysis (p < 0.05), demonstrating that the ecological interactions may exist in the DWDS. 16S rRNA genes sequencing of water samples revealed a significant different microbial community structure between UV/Cl2 and Cl2. This study may give some implications for controlling the OPs in the DWDS disinfected with UV/Cl2.

Silver-Coated Endotracheal Tubes Cleaned With a Mechanism for Secretion Removal.

Biofilm on the surface of endotracheal tubes (ETTs) is associated with ventilator-associated pneumonia. The use of silver-coated ETTs has been suggested to reduce the occurrence of ventilator-associated pneumonia by preventing biofilm formation. However, mucus accumulation can reduce the antibacterial activity of silver-coated ETTs by isolating bacterial colonies from the silver surface. We hypothesized that, in mechanically ventilated subjects, periodic removal of secretions through the use of a cleaning device would enhance the antimicrobial properties of silver-coated ETTs and thus reduce bacterial colonization. Subjects were randomized to either standard suctioning (blind tracheal suctioning, control group) or blind tracheal suctioning plus cleaning maneuver every 8 h (treatment group). Tracheal aspirates were collected immediately before extubation for microbiological culture. After extubation, ETTs were collected for both cultural and non-cultural microbiological analysis and biofilm isolation. 39 subjects expected to be ventilated for > 48 h were enrolled; 36 ETTs (18 control, 18 treatment) and 29 tracheal samples (15 control, 14 treatment) were collected. Among the ETTs positive for bacterial colonization (15 vs 9, P = .18), cleaning maneuvers did not reduce microbial load, shown as the decimal logarithm of colony-forming units (CFU) per mL (1.6 ± 1.2 vs 0.9 ± 1.2 logCFU/mL, P = .15). There was a trend toward decreased biofilm deposition (439.5 ± 29.0 vs 288.9 ± 157.7 mg, P = .09) in the treated ETTs. No significant differences were observed in the number of positive tracheal aspirates (13 vs 10, P = .39) or in the microbial load (4.8 ± 4.0 vs 4.2 ± 3.8 logCFU/mL, P = .70) of tracheal secretions. Finally, no differences in the microbial load of Gram-positive organisms, Gram-negative organisms, or yeasts were found between the ETTs and tracheal aspirates of the 2 groups. In 39 critically-ill subjects intubated with silver-coated ETTs, periodic cleaning maneuvers did not decrease bacterial colonization of the ETTs and did not lower respiratory tract colonization compared to the standard suctioning. (Clinicaltrials.gov registration NCT02120001.).

Oral status, cognitive function and dependency among New Zealand nursing home residents.

To investigate clinical oral disease and its association with cognitive function and dependency among older New Zealanders in residential aged care. National survey of oral health in aged residential care throughout New Zealand. We classified residents into 1 of 3 levels of care: "low dependency care (or assisted living)"; "high dependency care"; or "specialist dementia care/psychogeriatric care." The Abbreviated Mental Test characterised cognitive function as "unimpaired" (scores of 7-10), "moderately impaired" (4-6) or "severely impaired" (0-3). Intra-oral examinations were conducted, along with a computer-assisted personal interview. Most of the 987 clinically examined participants were either at low or high dependency care level, with another 1 in 6 in psychogeriatric care. Almost half overall had severely impaired cognitive function. Just under half of the sample had 1 or more natural teeth remaining. Negative binomial regression modelling showed that the number of carious teeth was lower among women and higher among those who were older, those with more teeth and in those with severely impaired cognitive function. Oral debris scores (representing plaque biofilm and other soft deposits on teeth) were higher in men, those with more teeth, and in those with severely impaired cognitive function. Impaired cognitive function is a risk indicator for both dental caries and oral debris in aged residential care.

Evaluation of combined growth media for in vitro cultivation of oropharyngeal biofilms on prosthetic silicone

In the upper aerodigestive tract, biofilm deposits by oropharyngeal microbes can cause failure of medical polymer devices like voice prostheses. Previous studies on testing of inhibitive strategies still lack of comparability due to varying study protocols concerning growth media, microbial species and growth conditions. Goal of the study was therefore to test cultivation of a mixed biofilm of isolated oropharyngeal microbes under in vitro growth conditions using mixtures of common growth media. Mixtures of yeast peptone dextrose medium (YPD), fetal bovine serum (FBS), RPMI 1640, Yeast nitrogen base medium (YNB) and brain heart infusion (BHI) were tested to grow mixed biofilm deposits of Candida albicans, Candida tropicalis, Staphylococcus aureus, Streptococcus epidermidis, Rothia dentocariosa and Lactobacillus gasseri on medical grade silicone. Periodic assessment of living biofilm was performed over 22 days by a digital microscope and the cultivated biofilm structures were analyzed by scanning electron microscopy after completion of the study. Mixtures of BHI, YPD and FBS improved microscopic growth of multispecies biofilm deposits over time, while addition of RPMI and YNB resulted in reduction of visible biofilm deposit sizes. A mixtures of FBS 30% + YPD 70% and BHI 30% + YPD 70% showed enhanced support of permanent surface growth on silicone. Growth kinetics of in vitro multispecies biofilms can be manipulated by using mixtures of common growth media. Using mixtures of growth media can improve growth of longterm multispecies oropharyngeal biofilm models used for in vitro testing of antibiofilm materials or coatings for voice prostheses.

Phase-resolved photoacoustic spectroscopy to monitor dental plaque on tooth enamel

ABSTRACTDental plaque is a biofilm on the enamel surface of the teeth, formed by colonizing bacteria. It is essential to monitor the biofilm presence on the surface of the enamel of the teeth, since plaque is a reason for periodontal disease and dental caries. This paper proposes applying photoacoustic spectroscopy to monitor and the phase-resolved photoacoustic method to analyze the biofilm plaque on samples of human dental enamel facets. The biofilm growth occurred in the oral cavity environment at deposition time of 48 and 72 h. Photoacoustic ex vivo monitoring found that: (1) Photoacoustic spectroscopy is a helpful tool to identify the bactericidal effect on dental plaque; (2) the biofilm deposition provides an optical absorption of the Soret band at 410 nm and increase of hydroxyl absorption band; (3) the biofilm thickness by phase-resolved photoacoustic method is in agreement with the literature in situ measurements. These new knowledges may help in development of a greater practicality and safety equipment able to identify and quantify dental biofilm, which may be achieved with low-cost Soret-band light emitting diode as light excitation.

Influence of calcareous deposit on corrosion behavior of Q235 carbon steel with sulfate-reducing bacteria

Cathodic protection is a very effective method to protect metals, which can form calcareous deposits on metal surface. Research on the interrelationship between fouling organism and calcareous deposits is very important but very limited, especially sulfate-reducing bacteria (SRB). SRB is a kind of very important fouling organism that causes microbial corrosion of metals. A study of the influence of calcareous deposit on corrosion behavior of Q235 carbon steel in SRB-containing culture medium was carried out using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and surface spectroscopy (EDS). The calcareous deposit was formed with good crystallinity and smooth surface under the gradient current density of −30 μA cm−2 in natural seawater for 72 h. Our results can help elucidate the formation of calcareous deposits and reveal the interrelationship between SRB and calcareous deposits under cathodic protection. The results indicate that the corrosion tendency of carbon steel was obviously affected by Sulfate-reducing Bacteria (SRB) metabolic activity and the calcareous deposit formed on the surface of carbon steel under cathodic protection was favourable to reduce the corrosion rate. Calcareous deposits can promote bacterial adhesion before biofilm formation. The results revealed the interaction between biofouling and calcareous deposits, and the anti-corrosion ability was enhanced by a kind of inorganic and organic composite membranes formed by biofilm and calcareous deposits.

3D printed feed spacers based on triply periodic minimal surfaces for flux enhancement and biofouling mitigation in RO and UF

In this proof of concept study, 3D printed feed spacers with complex geometries based on triply periodic minimal surfaces (TPMS) were designed and tested in reverse osmosis (RO) and ultrafiltration (UF) processes. The spacers showed flux enhancement of 15.5% and 38% in brackish water RO and UF tests with sodium alginate solution, respectively, in comparison to a commercial feed spacer. Moreover, lower feed channel pressure drop was also observed for the TPMS spacers. Biofouling tests were performed and the membranes were characterized using total organic carbon (TOC) and fluorescence microscopy. The TPMS spacers yielded a reduction in biofouling when compared to commercial feed spacers. Fouling patterns on the membranes were visualized for the different spacers using crystal violet stain, which also revealed a significantly reduced biofilm deposition using the TPMS spacers. The TPMS-based feed spacers have shown great promise in enhancing both RO and UF membrane processes, both in terms of flux enhancement and fouling reduction.

Pyrosequencing analysis of source water switch and sulfate-induced bacterial community transformation in simulated drinking water distribution pipes.

Inter-basin water transfer and source water switching will be increasingly launched due to significant population increase and the shortage of the local water resources in cities around the world. Source water switch may cause physiochemical and microbiological de-stabilization of pipe material, biofilms, and loose deposits in drinking water distribution system (DWDS). Great sulfate alteration during source water switch had been deemed as the main cause of a red water case that occurred in a northern China city. To ascertain the relationship between water quality changing and bacterial communities of biofilms in DWDS and possible bacteria risk in a red water case, water quality changing experiments in simulated DWDSs were conducted for approximately 2years. Twenty-five corrosion scale samples and eight water samples collected from pipe harvest sites or during experimental periods were analyzed for their bacterial community composition by 454-pyrosequencing technology. Taxonomy results together with redundancy analysis (RDA) or canonical correspondence analysis (CCA) and hierarchical cluster analysis all indicated that bacterial community of samples with groundwater (GW) or surface water (SW) supply history and their variations under high sulfate water were rather different owing to different water source histories and the original pipe scale characteristics. Potential opportunistic pathogens: Burkholderia, Escherichia-Shigella, Mycobacterium, Serratia, Ralstonia, Novosphingobium, Flavobacterium, Sphingomonas, and Sphingopyxis were observed in scale or water samples.

Antibacterial and anti-encrustation biodegradable polymer coating for urinary catheter

Bacterial biofilm and crystalline deposits are the common causes of failure of long-term indwelling urinary catheter. Bacteria colonise the catheter surface causing serious infections in the urinary tract and encrustations that can block the catheter and induce trauma in patients. In this study, the strategy used to resist bacterial adhesion and encrustation represents a combination of the antibacterial effects of norfloxacin and silver nanoparticles and the PLGA-based neutralisation of alkali products of urea hydrolysis gained through the degradation of the polymer in an aqueous milieu. Silver nanoparticles were coated with tetraether lipids (TEL) to avoid aggregation when dispersed in acetone and during the film formation. The polymer films loaded with the two antibacterial agents were applied on Polyurethane (PUR) and Silicon sheets. We demonstrated the antibacterial and anti-adhesion effectiveness of the coatings whereby commercially available biocompatible polymers PUR and Silicon were used as controls. Using artificial urine and an in vitro encrustation model, it was shown that the coatings resist the encrustation for at least 2 weeks. This combination of a biodegradable polymer and wide-range antibacterial agents represents a potentially attractive biocompatible coating for urinary catheters.

Carbonate scale deactivating the biocathode in a microbial fuel cell

The development and the following inactivation of a carbon-based biocathode in single chamber and membraneless MFCs was investigated in this work. The electrochemical behavior of the biocathode has been analyzed over time during the MFC life. X-Ray Micro-Computed Tomographies (microCTs) have been carried out at progressive stages, documenting the building over time of a layer of scale deposition becoming thicker and thicker up to the cathode inactivation. The technique provides cross-sectional (tomographic) grayscale images and 3D reconstruction of volumes. Lighter color indicates lower X-ray attenuation (i.e., lower atomic density) thus allowing distinguishing biofilm from inorganic fouling on the basis of the average atomic number Z of each voxel (3D pixel). MicroCT was combined with Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) in order to qualitatively recognize chemical species in each different layer of the cathode's section. Results correlated the presence of biofilm and calcium carbonate deposits, prevalently in the inner part of the cathode, with the produced electric current over time. A specific microCT-related software quantified the time-dependent carbonate scale deposition, identifying a correlation between the decreasing performances of the device and the increasing quantity of scale deposition that penetrates the cathode cross section in time.

In-situ biofouling assessment in spacer filled channels using optical coherence tomography (OCT): 3D biofilm thickness mapping

Membrane systems for water purification can be seriously hampered by biofouling. The use of optical coherence tomography (OCT) to investigate biofilms in membrane systems has recently increased due to the ability to do the characterization in-situ and non-destructively. The OCT biofilm thickness map is presented for the first time as a tool to assess biofilm spatial distribution on a surface. The map allows the visualization and evaluation of the biofilm formation and growth in membrane filtration systems through the use of a false color scale. The biofilm development was monitored with OCT to evaluate the suitability of the proposed approach. A 3D time series analysis of biofilm development in a spacer filled channel representative of a spiral-wound membrane element was performed. The biofilm thickness map enables the time-resolved and spatial-resolved evaluation and visualization of the biofilm deposition pattern in-situ non-destructively.

Whether a novel drug delivery system can overcome the problem of biofilms in respiratory diseases?

Biofilm comprises a community of microorganisms which form on medical devices and can lead to various threatening infections. It is a major concern in various respiratory diseases like cystic fibrosis, chronic obstructive pulmonary disease, etc. The treatment strategies for such infections are difficult due to the resistance of the microflora existing in the biofilms against various antimicrobial agents, thus posing threats to the patient population. The present era witnesses the beginning of research to understand the biofilm physiology and the associated microfloral diversity by applying -omics approaches. There is very limited information about how the deposition of biofilm on the respiratory devices and lung itself affects the drug delivered, the delivery system, and other implications. The present mini review summarizes the basic introduction to the biofilms and its avoidance using various drug delivery systems with special emphasis on the respiratory diseases. Understanding the approaches, principles, and modes of drug delivery involved in preventing biofilm deposition will be of interest to both biological and formulation scientists, thereby opening avenues to explore the new vistas in biofilm research for identifying better treatments for pulmonary infectious diseases.

Significance of polymethylmethacrylate (PMMA) modification by zinc oxide nanoparticles for fungal biofilm formation

The objective of this study was to obtain a material composite with antifungal properties for dentures to be used as an alternative protocol in denture stomatitis treatment and prevention. Denture stomatitis is still a clinical problem in patients particularly vulnerable to this disease. Composites of PMMA and doped ZnO-NPs (weight concentrations, 2.5%, 5%, 7.5%) and PMMA with sprayed solvothermal and hydrothermal ZnO-NPs were tested. The following investigations of newly formed biomaterials were undertaken: influence on Candida albicans solution, biofilm staining, XTT analysis and a quantitative analysis of adhered C. albicans. These studies evidenced the antifungal activity of both nanocomposites PMMA–ZnO-NPs and the efficacy of sputtering of zinc oxide nanoparticles on the PMMA. The study of the biofilm deposition on the surface showed that antifungal properties increase with increasing concentration of ZnO-NPs. The XTT assay in conjunction with testing the turbidity of solutions may indicate the mechanism by which ZnO-NPs exert their effect on the increased induction of antioxidative stress in microorganism cells. The denture base made of the aforesaid materials may play a preventive role in patients susceptible to fungal infections.Based on the results obtained a modified treatment of stomatitis Type II (Newton’s classification) complicated by fungal infection was proposed.

Contribution of assimilable organic carbon to biological fouling in seawater reverse osmosis membrane treatment

Biological fouling occurs on RO membranes when bacteria and nutrients are present in conditions that are conducive to growth and proliferation of the bacteria. Controlling microbial growth on the membranes is typically limited to biocide application (i.e., disinfectants) in seawater RO plants. However, biological growth and subsequent fouling has not been well-managed. Pretreatment has not been focused on nutrient limitation. This project used a biological assay, the assimilable organic carbon (AOC) test to evaluate pretreatment effects on the nutrient supply. The AOC test provided a useful surrogate measurement for the biodegradability or biofouling potential of RO feed water. Biofouling observed in controlled conditions at the bench- and pilot-scale resulted in statistically significant correlations between AOC and the operational effects caused by biofouling. Membrane fouling rates are observed through operational changes over time such as increased differential pressure between the membrane feed and concentrate locations and decreased permeate flux through the membrane. In full scale plants there were strong correlations when AOC was used as a predictor variable for increased differential pressure (0.28–0.55 bar from September–December 2012) and decreased specific flux (1.40 L per hour/(m2 · bar)). Increased differential pressure was associated with RO membrane biological fouling when the median AOC was 50 μg/L during pilot testing. Conditions were also evaluated at the bench-scale using a flat sheet RO membrane. In a comparison test using 30 and 1000 μg/L AOC, fouling was detected on more portions of the membrane when AOC was higher. Biofilm and bacterial deposits were apparent from scanning electron microscope imaging and biomass measurements using ATP.

Functional characterization of biomedical potential of biosurfactant produced by Lactobacillus helveticus

Various lactic acid bacteria (LAB) have been isolated and screened for biosurfactant production and their biomedical and food applications. Additionally, various different concentrations of the biosurfactant (0.625–25mgml−1) were used to evaluate its antimicrobial and antiadhesive potential against a range of pathogenic microorganisms. Biosurfactant was found to be stable to pH changes over a range of 4.0-12.0, being most effective at pH 7 and showed no apparent loss of surface tension and emulsification efficiency after heat treatment at 125°C for 15min. Present study demonstrated that biosurfactant obtained from Lactobacillus helveticus has the ability to counteract effectively the initial deposition of biofilm forming pathogens to silicone surfaces and to significantly sluggish biofilm growth.

Periodontal status in Taiwanese pregnant women

Background/purposeFew studies have investigated the periodontal status of Taiwanese pregnant women. This study aimed to investigate the periodontal status of pregnant women and to examine its relation to oral hygiene. Material and methodsThis study randomly recruited 477 pregnant women. Among them, 203 women were in their first trimester. Forty-six women completed the study to the end of their third trimester. We also recruited 160 nonpregnant women as the control group. Clinical periodontal parameters were recorded and included probing pocket depth [PPD (mm)], clinical attachment level [CAL (mm)], gingival index simplified [GI-s (%)], and plaque index [PI (%)]. ResultsThe GI-s of the pregnant group (PG) was higher than that of the control group [CG; (i.e., nonpregnant)], but only the third trimester was statistically significantly different (P<0.001).The full mouth dental PI was higher in the PG than in the CG (P<0.001), particularly in the interproximal areas. The mean PPD was greater in the PG than in the CG (P<0.001) in all tooth areas. The mean CAL was higher in the PG than in the CG (P<0.001), but no difference existed between the different trimesters. The CG had a higher percentage of sites with a shallow PPD, compared to the PG (P<0.001); the PG had a higher percentage of sites with a PPD of 4–6 mm, compared to the CG (P<0.001). Only the PI of the full mouth and lingual tooth surfaces in the third trimester were better than in the first trimester throughout the pregnancy. ConclusionGingival inflammation in pregnant women is positively correlated with the increased deposition of a dental plaque biofilm.

Inappropriate Toothbrushes Selection Alter Composite Dental Material Restoration Surface Roughness: A Preliminary Study

Introduction. Regular dental plaque control by means of chemically and mechanically methods are among efforts to improve oral health and hygiene. Mechanical cleansing using toothbrush is still the gold standard for continually removing of dental plaque. But on the other hand, inappropriate selection of toothbrushes type selection promotes alteration on dental material restoration surface. Toothbrushes with different degree of stiffness are readily available on market and are classified as hard, medium, and soft. Mechanical friction due to regular movement of the toothbrush with various degree of stiffness was predicted as factor that related with surface roughness alteration on dental material restoration. Nowadays, resin composite material is still declared as the material of choice to repair dental hard tissue damage due to caries activity. However, it has been found that the irregularity of surface promotes bacterial adhesion and biofilm deposition, whereas the smooth surface does not favor bacterial deposition. The progress of bacterial deposition promotes secondary caries on the margin between material restoration and teeth. The aim of this in vitro study was to evaluate the influence of brushing treatment by means of three different toothbrushes on the surface of resin-based compositesExperimental. Specimens were prepared from experimental RBCs with 5 mm diameter and 2 mm thick. Specimens were divided equally into 3 different groups (group A, B, and C). Each group has 5 numbers of specimens. Group A was treated with hard toothbrush, and group B as well as C were treated with medium and soft toothbrush respectively. The toothbrush was mounted in the customized mechanically brushing machine to control the force and number of cycle during specified time. Brushing cycle and time for all groups was conducted for 1000 times of brushing in 60 minutes. Surface roughness resulted from mechanically brushing is evaluated by means of profilometer device.Results and Discussion. The results of the preliminary study shows that there is a differences of surface roughness between groups. The value of roughness varied among all group, and the highest number of roughness were found in group A (&gt; 0.2 micrometres).Conclusions. This result implies brushing with hard toothbrush preferentially has greater risk of surface damage and become pronounce factor of secondary caries.

(Invited) Hybrid Materials for Electrocatalytic and Photoelectrochemical Reduction of Carbon Dioxide: Comparison to Their Activity during Oxygen Reduction

Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO2 reduction and, depending on reaction conditions (applied potential, strength of the electrolyte, local pH, local concentration of CO2 and the catalyst applied), various products can be obtained. Because the CO2 molecule is very stable, its electroreduction would be characterized by large over-potentials. In this respect, behavior of carbon dioxide resembles that of dioxygen. In both cases, the limiting steps involve protonation of the respective species. A crucial problem in designing effective electrocatalytic systems for the reduction of carbon dioxide is the necessity to cope with the another competitive process, namely the simultaneous hydrogen evolution. Mechanisms of reductions of both carbon dioxide and protons are dependent not only on the proton availability and mobility at the electrocatalytic interface but also on the presence the adsorbed hydrogens at the active catalytic sites. In this respect, numerous metallic catalysts (e.g. Cu, Pd, Pt) have been proposed. Alternate approaches to efficient electroreduction of carbon dioxide my refer to utilization of biological systems. Recently, whole cell biocatalysts and microbial electrocatalysts have been considered. Microorganisms can form very stable biofilms well-adhering to different solid surfaces. We propose here a hybrid (biofilm-based organic-inorganic) support or matrix for catalytic (noble metal) nanoparticles. The system was obtained by consecutive deposition of the porous polyaniline-supported bacterial biofilm (Yersinia enterocolitica) and multi-walled carbon nanotubes. Although this biofilm does not exhibit appreciable activity toward reduction of carbon dioxide, its structure (while being robust) contains open water channels existing between the bacterial micro-colonies thus permitting unimpeded flow of the aqueous electrolyte. The system’s performance will also be discussed with respect to the oxygen reduction. To appreciate effective reduction of carbon dioxide, instead of conventional Pd nanoparticles, nanosized Pd immobilized within supramolecular assemblies of tridentate Schiff-base ligands or supported onto hybrid biofilm-based matrices have been considered. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities. Among important issues are specific interactions between nitrogen coordinating centers and metallic palladium sites. interface. The above activating phenomena will also be verified during oxygen reduction. Through intentional and controlled combination of metal oxide semiconductors, we have been able to drive effectively photo-electrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide (TiO2) and copper (I) oxide (Cu2O) has been explored toward the reduction of carbon (IV) oxide (CO2) before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. The role of TiO2 is not only in stabilizing the interface: the oxide is also expected to prevent the recombination of charge carriers. Possibility of further decoration with traces of the conventional noble-metal-based systems (mentioned above) will be also addressed.