Faster Bacterial Inactivation Research Articles

Innovative electrochemical synthesis of highly defective Ta2O5/Cu2O nanotubes inactivating bacteria under low-intensity solar irradiation

This study presents an innovative electrochemical preparation of Ta2O5 nanotubes (NTs) decorated with Cu2O nanoparticles (NPs). The Ta2O5/Cu2O nanotubes led to fast bacterial inactivation under low-intensity solar irradiation. The Cu2O decoration on Ta2O5 nanotubes accelerated the E. coli inactivation kinetics by several orders of magnitude compared to bare Ta2O5 nanotubes. Systematic characterization of the surface properties of Ta2O5/Cu2O nanotubes is reported. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), XPS-spectroscopy, and energy dispersive X-ray spectroscopy (EDX) were used to understand the structural, morphological and chemical composition of the decorated nanotubes. UV–VIS spectroscopy, photoluminescence (LP), and surface reflectivity further allowed to understand the effect of photons on the nanotube interfaces giving insight into the role of structural defects, oxygen vacancies and Cu2O decoration. The oxygen vacancies formation and contribution to the bacterial inactivation have been highlighted. The bandgap of Ta2O5/Cu2O decreased upon increasing the Cu2O addition to Ta2O5 NTs. A differentiated mechanism for bacterial inactivation is suggested under low-intensity solar light (50 mW/cm2) for Ta2O5 NTs and Ta2O5/Cu2O NTs. The high photocatalytic activity of Ta2O5 possibly involved the surface and bulk electron diffusion steps, leading to the generation of the observed surface catalytic sites. A mechanism has been proposed for the antibacterial activity of the prepared nanotubes.

Fast Bacterial Inactivation Kinetics on an Inherently Antimicrobial Anionic Block Polymer

Mitigation of the global threat associated with antibiotic-resistant microbes necessitates effective preventative measures. One such strategy relies on self-disinfecting anionic block polymers that undergo a water-activated surface pH drop, which kills over 99.9999% of various microbes in minutes. In this work, we elucidate the time-dependent morphological response of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria to this polymer surface. Since pre-exposure of the polymer to solvent-vapor or hydrothermal annealing alters the tortuosity of pathways responsible for proton diffusion, corresponding changes in bacterial inactivation kinetics are compared and analyzed in the context of a model capable of differentiating between single-stage and more complex inactivation processes.

Hybrid ZnO@Au Nanorod Array for Fast and Repeatable Bacteria Inactivation

Comprehensive SummaryThe worldwide abuse of antibiotics and resultant antimicrobial resistance made the development of new antibacterial materials an urgent and significant issue. Herein, a hybrid ZnO@Au nanorod array with fast bacterial inactivation and excellent recyclability was reported. 93% bacteria could be inactivated within 5 min ultra‐sonication under indoor daylight, and the killing rate maintains above 90% after seven repeated using cycles. Antibacterial mechanism involves extracellular reactive oxygen species (ROS) generated from photocatalysis and piezoelectricity of nanorod array, intracellular ROS generation and decrease of adenosine‐triphosphate (ATP) originated from electron transfer (ET) from bacteria to nanorod array, as well as mechanical effect from the nanorod, among which ET mechanism plays a major role. Large Schottky barrier from the hybrid interface not only enhances the ROS generation by promoting the charge transfer and carrier separation as well as light utilization, but also enables one‐direction electron transfer from bacteria to nanorod array. The resultant continuous electron loss breaks the energy metabolism and disturbs the redox equilibrium, leading to bacterial death. This study demonstrates the great potential of hybrid structure in antibacterial applications and indicates ET as a novel effective antibacterial mechanism for semiconductor materials, which provides insights into the design of next‐generation antibacterial materials.

Dynamics of VOCs degradation and bacterial inactivation at the interface of AgxO/Ag/TiO2 prepared by HiPIMS under indoor light

• Indoor/outdoor air pollution and bacteria were degraded on sputtered Ag x O/Ag/TiO 2 on textile. • Photocatalytic kinetics are carried out in the dark and under visible light. • Ag/AgxO nanoparticles show a significant effect on the activity of TiO 2 . • A possible mechanism of photocatalytic processes is suggested. Ag x O/Ag/TiO 2 photoactive thin films were produced by different modes of magnetron sputtering (namely, DCMS and HiPIMS). The spectral and microstructural properties of the Ag-Ag x O/TiO 2 thin films were studied by Diffuse Reflection Spectroscopy (DRS) and X-Ray Photoemission Spectroscopy (XPS). The atomic deposition of TiO2 and Ag in the thin sputtered film were studied by TEM. Ag x O/Ag/TiO 2 exhibited fast photocatalytic volatile organic compounds (VOCs) degradation and bacterial inactivation under low visible light intensity. The Langmuir Hinshelwood model was applied to highlight the photocatalytic performance of the Ag x O/Ag/TiO 2 catalyst. The oxidative states of Ag-Ag x O/TiO 2 were studied by XPS. Deconvolution of the Ag3d peak of the Ag x O/Ag/TiO 2 thin films showed the presence of AgO and metallic Ag. It is suggested that the mechanism involving the degradation of VOCs on AgO/Ag/TiO 2 catalysts is due to the transfer of holes from AgO to TiO 2 via the AgO/Ag/TiO 2 heterojunction. The electrostatic interaction between both semiconductors allows this charge transfer. In addition, the contribution of reactive oxygen species (ROS) in bacterial inactivation at the interface of AgO/Ag/TiO 2 thin film was also examined. Light-induced interfacial charge transfer (IFCT) between AgO and TiO 2 leading to pollutants oxidation appears to require low photons’ energy and can oxidize pollutants even at high concentrations. The sputtered coatings have also been studied for repetitive reuse, showing the sustainable activity of the prepared materials.

New dendritic porphyrins: Synthesis, spectroscopic and antibacterial evaluation

In this work, a new porphyrin-dendrimer (Pf-PPI) was synthesized, which can form complex Ag+ leading to a Pf-PPI-Ag+ stable compound. The molecular structure of the dendrimers was characterized by 1H NMR and 13C NMR, FT-IR, TGA and UV–vis. The metal complexation capacity of dendritic nanostructures was evaluated using filtration followed by atomic absorption, and the binding sites were elucidated by FT-IR spectrometry and TGA analysis. The results show that the functional groups in dendrimer branches are involved in the retention rate of cations. Transient studies proved good capacity for singlet oxygen generation even in the presence of the cation, showing that both complexing and sensitizing properties are compatible with each other. The antibacterial effect of the compounds on E. coli was also evaluated. Although some dark toxicity was observed, a complete and faster bacterial inactivation was recorded under visible light irradiation, demonstrating high photodynamic efficiency of the tested compounds.

CaIn2S4–In2O3 hybrid nanofibers with expedited photocarrier separation for fast photocatalytic bacterial inactivation under visible light

CaIn2S4–In2O3 hybrid fibers deliver exceptionally high photocatalytic activity for bacterial inactivation due to a strong interplay between CaIn2S4 and In2O3.

Deciphering the Mechanisms of Bacterial Inactivation on HiPIMS Sputtered CuxO-FeOx-PET Surfaces: From Light Absorption to Catalytic Bacterial Death.

The production of nontoxic, affordable, and efficient antibacterial surfaces is key to the well-being of our societies. In this aim, antibacterial thin films have been prepared using earth-abundant metals deposited using high-power impulse magnetron sputtering (HiPIMS). The sputtered FeOx, CuxO, and mixed CuxO-FeOx films exhibited fast bacterial inactivation properties under exposure to indoor light (340-720 nm) showing total bacterial inactivation within 180, 120, and 60 min, respectively. The photocatalytic mechanisms of these films were investigated, from the absorption of photons up to the bacteria's fate, by means of ultrafast transient spectroscopy, flow cytometry, and malondialdehyde (MDA) quantification justifying the cell wall disruption. The primary driving force leading to bacterial inactivation was found to be the oxidative stress at the interface between the sputtered thin films and the microorganism. This was justified by using engineered porinless bacteria disabling the possible ion diffusion leading to internal bacterial inactivation. Such stress is a direct consequence of the photogenerated electron-hole pairs at the interface of the sputtered layers. By diffuse reflectance spectroscopy, we found that both FeOx and CuxO present a band gap of ∼2.9 eV (>425 nm), while the mixed CuxO-FeOx thin film has a band gap below 2.3 eV (>540 nm). The structure and atomic composition of the films were characterized by energy-dispersive X-ray, X-ray photoelectron, and optical spectroscopy. While the composition and metal oxidation states are distinct in all three films, the difference in photocatalytic efficiency can, at first sight, be explained as the direct consequence of their absorbance and the unique interaction between Fe and Cu oxides in the composite film.

Chlorine dioxide: an evaluation based on a microbial decay approach during mango packing process

ABSTRACT Mango is highly consumed worldwide; nonetheless, its consumption has been related to foodborne outbreaks. This study was performed to evaluate bacterial transference during mango postharvest management and the feasibility of adopting chlorine dioxide as first choice disinfectant in mango packinghouse. Chlorine dioxide (3 and 5 ppm) and sodium hypochlorite (100 and 200 ppm) were evaluated at different turbidity and times against Salmonella Choleraesuis and Listeria monocytogenes. Bacterial transference was higher from water to fruit than vice-versa (49.17%). Chlorine dioxide (5 ppm) achieved the highest Salmonella reductions at low turbidity reaching 2.13 Log10 at 10 min; meanwhile, Listeria was totally reduced in all conditions. Bacterial decay kinetic showed that chlorine dioxide 5 ppm was 34-fold faster than sodium hypochlorite at 200 ppm in reducing 1 Log10 of Salmonella. Chlorine dioxide reached faster bacterial inactivation decay over sodium hypochlorite; its usage is safe and meets the regulatory standards set for mango processing.

Grafted semiconductors on PE-films leading to bacterial inactivation: Synthesis, characterization and mechanism

This study reports the colloidal preparation FeOx, TiO2 and FeOx-TiO2 grafted on polyethylene (PE) films leading to bacterial inactivation. A fast bacterial inactivation was attained by the FeOx-TiO2 compared to the FeOx-PE film due to the interfacial charge transfer (IFCT) FeOx to the lower-lying TiO2 trapped states. A pH-decrease was observed during bacterial inactivation due to the formation of carboxylic acids on the grafted films and the recovery to the initial pH ∼7 after elimination of the intermediates was followed quantitatively during bacterial inactivation. The potential on the TiO2-PE, FeOx-PE and FeOx-TiO2-PE film surfaces decreased during the bacterial inactivation concomitant with the loss of the cell wall permeability. Different mechanisms for the photo-induced E. coli inactivation for random nanoparticulate FeOx-PE and FeOx-TiO2-PE films are suggested based on the experimental observations reported in this study. During the inactivation of E. coli, the Fe-ions were seen to leach out in amounts ≤0.45ppm. This is within the EU sanitary allowed limits for industrial/drinking water. The wettability of the films was followed by contact angle measurements (CA) within the time of bacterial inactivation. By diffuse reflectance spectroscopy (DRS), the conversion of the Fe(III)-oxide to Fe(II)-oxide is reported during film recycling. The change in the Fe-oxidation states within the bacterial inactivation was further confirmed by X-ray photoelectron spectroscopy (XPS).

Formation of ammonium in saline solution treated by nanosecond pulsed cold atmospheric microplasma: a route to fast inactivation of E. coli bacteria

The formation of significant NH4+species in saline solutions treated by He/N2cold atmospheric plasma is proposed for the first time as the main process responsible for the fast bacterial inactivation ofE. coliat ambient temperature and physiological pH.

Efficiency of phage cocktails in the inactivation of Vibrio in aquaculture

Abstract Aquaculture is one of the fastest growing sectors in the world, having a very important role in the economy. However, the losses associated with bacterial infections such as vibriosis, lead to huge economic costs. The regular use of antibiotics in aquaculture has resulted in the development of resistant strains, which have contributed to the inefficacy of antibiotics. To reduce the risk of the development and spreading of microbial resistance and to control the fish diseases in aquaculture, alternative strategies must be developed. Phage therapy can be an eco-friendly alternative to prevent and control pathogenic bacteria in aquaculture. However, phage bacterial resistance is already well documented but the use of phage cocktails can overcome this drawback. The aim of this study was to evaluate the efficiency of cocktails of two and three phages of Vibrio parahaemolyticus (VP-1, VP-2 and VP-3) to control Vibrio in aquaculture. All phages were effective against V. parahaemolyticus, however, the VP-3 phage was the most efficient one (additional reduction of more 2 log when compared with the other two phages). The use of cocktails with two and three phages was significantly more effective (reductions of 4 log after 2 h) than the use of VP-1 and VP-2 phages alone (reductions of 0.8 log after 2 h), however, the efficiency of VP-3 phage was similar for the phage alone and for the phage in the cocktails (reduction of 3.8 log and 4.2 log for VP-3 phage alone and in cocktails, respectively, after 8 and 6 h). All phages remained viable for a long time (at least 5–7 months) in marine water. The VP-3 phage presented a larger burst size and a shorter latent period (42 and 40 min, respectively) than the other two phages (9 and 120 min and 15 and 90 min, respectively, for VP-1 and VP-2 phages). Overall, the use of phage cocktails of two or three phages increased the efficiency of phage therapy against Vibrio (more efficient and faster bacterial inactivation), delaying the development of resistance by the bacteria and the use of Vibrio phages with high burst sizes and short lytic cycles also increases the efficiency of phage therapy.

Innovative semi-transparent nanocomposite films presenting photo-switchable behavior and leading to a reduction of the risk of infection under sunlight

Novel sputtered polyethylene–TiO2 (PE–TiO2) thin films induce fast bacterial inactivation with concomitant photo-switchable hydrophobic to hydrophilic transition under light. RF-plasma pretreatments allowed an increased TiO2 loading on PE, favorably affecting the photocatalyst performance. ATR-FTIR spectroscopy shows that the increase in the cell lipid-layer fluidity leads to cell wall scission/bacterial inactivation.

RF-plasma pretreatment of surfaces leading to TiO2 coatings with improved optical absorption and OH-radical production

Evidence presented for the RF pretreatment of polyester enhances the TiO2 coating generation of oxidative species/radicals under a low level actinic light irradiation. After 30min RF-plasma pretreatment of the polyester samples, the fastest bacterial inactivation was observed concomitant with (a) the largest ratio of surface oxidized to the reduced functionalities as determined by XPS, (b) a strong sample optical absorption as seen by DRS and (c) the highest concentration surface OH-radicals monitoring the fluorescence of the hydroxy-terephthalic acid. Evidence for the photocatalyst self-cleaning was found by XPS due to the lack of accumulation of bacterial residues on the polyester-TiO2. A further proof of self-cleaning was the ability by the polyester-TiO2 samples to inactivate again bacterial charge at the end of an inactivation cycle. By XPS evidence is presented for the Ti4+/Ti3+ related redox catalysis and the details of the C and O-functionalities. Surface techniques such as XRF, DRS, TEM, contact angle (CA), XRD and XPS were applied to relate the microstructure of the TiO2 coatings with the destruction of Escherichia coli taken as a probe.

Innovative TiO2/Cu Nanosurfaces Inactivating Bacteria in the Minute Range under Low-Intensity Actinic Light

The bacterial inactivation of E. coli by cotton TiO(2)/Cu DC-magnetron sputtered thin films was investigated in the dark and under low-intensity actinic light. The TiO(2)/Cu sputtered layers revealed to be sensitive to actinic light showing the spectral characteristics of Cu/CuO. This indicates that Cu does not substitute Ti(4+) in the crystal lattice. Under diffuse actinic light (4 mW/cm(2)), the hybrid composite TiO(2)/Cu sample lead to fast bacterial inactivation times <5 min. This study presents evidence for a direct relation between the film optical absorption obtained by diffuse reflectance spectroscopy (DRS) and the bacterial inactivation kinetics by the TiO(2)/Cu samples. The Cu-ions inactivating the bacteria were followed in solution by inductively plasma coupled spectroscopy (ICPS). The amounts of Cu-ions detected by ICPS provide the evidence for an oligodynamic antibacterial effect. The changes in the oxidation state of Cu during bacterial inactivation were followed by XPS. The E. coli cell viability was detected by standard coliform counting CFU methods. The TiO(2)/Cu thickness layer was determined by profilometry and the film microstructure by XPS, TEM, AFM, XRD, XRF and contact angle (CA). A mechanism of bacterial inactivation by TiO(2)/Cu samples is suggested in terms of interfacial charge transfer (IFCT) involving charge transfer between TiO(2) and Cu.

Gas Plasma Treatment: A New Approach to Surgery?

In this survey we analyse the status quo of gas plasma applications in medical sciences. Plasma is a partly ionized gas, which contains free charge carriers (electrons and ions), active radicals, and excited molecules. So-called nonthermal plasmas are particularly interesting, because they operate at relatively low temperatures and do not inflict thermal damage to nearby objects. In the past two decades nonthermal plasmas have made a revolutionary appearance in solid state processing technology. The recent trends focus on using plasmas in health care, for "processing" of medical equipment and even living tissues. The major goal of tissue treatment with plasmas is nondestructive surgery: controlled, high-precision removal of diseased sections with minimum damage to the organism. Furthermore, plasmas allow fast and efficient bacterial inactivation, which makes them suitable for sterilization of surgical tools and local disinfection of tissues. Much research effort must be undertaken before these techniques will become common in medicine, but it is expected that a novel approach to surgery will emerge from plasma science.