Development of advanced dressings with antimicrobial properties for the treatment of infected wounds is an important approach in the fight against evolution of antibiotic resistant bacterial strains. Herein, the effects of ion-crosslinked nanocellulose hydrogels on bacteria commonly found in infected wounds were investigated in vitro. By using divalent calcium or copper ions as crosslinking agents, different antibacterial properties against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa were obtained. Calcium crosslinked hydrogels were found to retard S. epidermidis growth (up to 266% increase in lag time, 36% increase in doubling time) and inhibited P. aeruginosa biofilm formation, while copper crosslinked hydrogels prevented S. epidermidis growth and were bacteriostatic towards P. aeruginosa (49% increase in lag time, 78% increase in doubling time). The wound dressing candidates furthermore displayed barrier properties towards both S. epidermidis and P. aeruginosa, hence making them interesting for further development of advanced wound dressings with tunable antibacterial properties.

Efficient charge carrier extraction from a colloidal quantum dot (CQD) solid is crucial for highperformance of CQD solar cells (CQDSCs). Herein, highly ordered wrinkled MgZnO (MZO) thin films aredemonstrated to improve the charge carrier extraction of PbS CQDSCs. The highly ordered wrinkledMZO thin films are prepared using a low-temperature combustion method. The photovoltaicperformances of CQDSCs with a combustion-processed MZO (CP-MZO) thin film as an electrontransport material (ETM) are compared to those of CQDSCs with a conventional sol–gel processed MZO(SGP-MZO) thin film as an ETM. We performed photoluminescence quenching measurements of thecolloidal quantum dot (CQD) solid and charge carrier dynamic analysis of full solar cell devices. Theresults show that the highly ordered wrinkled CP-MZO thin film significantly increases the chargecarrier extraction from the CQD solid and therefore diminishes the charge interfacial recombination atthe CQD/ETM junction, leading to a 15.5% increase in power conversion efficiency. The improvedefficiency in the CP-MZO based CQDSC is also attributed to the compact and pin-hole free CP-MZOthin film.

Objectives

The combination of TiO₂ and H₂O₂ under light activation constitutes a promising method for disinfection of dental prosthetics and implants, due to production of reactive oxygen species (ROS). The aim of this work was to investigate the organic degradation ability of TiO₂ particles in combination with H₂O₂ and under light activation utilizing the organic dye rhodamine B (RhB).

Methods

Five different types of TiO₂ particles, consisting of anatase, rutile, or a mixture of these crystalline phases, were combined with H₂O₂ and RhB, and subsequently exposed to UV (365 nm) or visible (405 nm) light at an irradiance of 2.1 mW/cm².

Results

It was found that rutile in combination with low concentrations of H₂O₂ (1.0–3.5 mM) resulted in a degradation of RhB of 96% and 77% after 10 min exposure to 365 nm and 405 nm light, respectively, which was the highest degradation of all test groups. Control measurements performed without light irradiation or irradiation at 470 nm, or without TiO₂ particles resulted in little or no degradation of RhB.

Conclusions

Low H₂O₂ concentrations (1.0 mM–3.5 mM) and visible light (405 nm) used in combination with rutile TiO₂ particles showed the highest RhB degradation capacity.

Clinical significance

A combination of TiO₂ particles and H₂O₂ exposed to low energy UV or high energy visible light has an organic degradation capability that could be utilized in applications to kill or inactivate bacteria on medical devices such as dental implants for treatment against, e.g., peri-implantitis.

We have measured the dynamics of water confined in a porous magnesium carbonate material, Upsalite (R), using the high-resolution neutron backscattering spectrometer SPHERES. We found quasielastic scattering that does not flatten out up to 360 K, which means that the dynamics of water are much slower than in other matrix materials. Specifically, a single Lorentzian line could be fitted to the quasielastic part of the acquired spectra between 220 and 360 K. This, accompanied by an elastic line from dynamically frozen water present at all experimental temperatures, even above the melting point, signaled a significant amount of bound or slow water.

Implanted materials are susceptible to bacterial colonization and biofilm formation, which can result in severe infection and lost implant function. UV induced photocatalytic disinfection on TiO2 and release of Ag⁺ ions are two promising strategies to combat such events, and can be combined for improved efficiency. In the current study, a combinatorial physical vapor deposition technique was utilized to construct a gradient coating between Ag and Ti oxide, and the coating was evaluated for antibacterial properties in darkness and under UV light against Staphylococcus epidermidis. The findings revealed a potent antibacterial effect in darkness due to Ag⁺ release, with near full elimination (97%) of viable bacteria and visible cell lysis on Ag dominated surfaces. The photocatalytic activity, however, was demonstrated poor due to low TiO2 crystallinity, and UV light irradiation of the coating did not contribute to the antibacterial effect. On the contrary, bacterial viability was in several instances higher after UV illumination, proposing a UV induced SOS response from the bacteria that limited the reduction rate during Ag⁺ exposure. Such secondary effects should thus be considered in the development of multifunctional coatings that rely on UV activation. 

Mesoporous magnesium carbonate (MMC) was first presented in 2013, and this material is currently under consideration for use in a number of biotechnological applications including topical formulations. This study presents the first evaluation of the antibacterial properties of the material with mesoporous silica and two other magnesium-containing powder materials used as references. All powder materials in this study are sieved to achieve a particle size distribution between 25 and 75 μm. The Gram-positive bacterium Staphylococcus epidermidis is used as the model bacterium due to its prevalence on human skin, its likelihood of developing resistance to antibiotics, for example, from routine exposure to antibiotics secreted in sweat, and because it is found inside affected acne vulgaris pores. Quantification of bacterial viability using a metabolic activity assay with resazurin as the fluorescent indicator shows that MMC exerts a strong antibacterial effect on the bacteria and that alkalinity accounts for the major part of this effect. The results open up for further development of MMC in on-skin applications where bacterial growth inhibition without using antibiotics is deemed favorable.

The choice of material for implanted prostheses is of great importance concerning bacterial colonization and biofilm formation. Consequently, methods to investigate bacterial behavior are needed in order to develop new infection resistant surfaces. In this study, different methodological setups were used to evaluate the antimicrobial effect of photocatalytic titanium oxide and silver surfaces. Biofilm formation and eradication under static and dynamic culture conditions were studied with the use of the following analytical techniques: viable colony-forming unit (CFU) counting, imprinting, fluorescence, and bioluminescence. The present study demonstrates that different methods are needed in order to evaluate the prophylactic and treatment effects on planktonic and biofilm bacteria and to assess the antimicrobial effect of different surface treatments/coatings. Choosing the right antibacterial testing model for the specific application is also of great importance. Both in situ approaches and indirect methods provide valuable complementary information. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2014.

The early fixation of bone screws after surgical implantation still remains a challenge in the field

of traumatology. Whilst hydroxyapatite (HA) coatings are known to enhance the fixation of implants;

their removal at a later time-point may be problematic. An HA coating has been developed

to demonstrate that both implant fixation and safe removal are feasible in the same design. Accordingly

the aim of this study was to compare the in-vivo performance of thin biomimetic HA coated

titanium screws to uncoated counterparts used as control after bilateral implantation in the femoral

condyle of 36 New Zealand White Rabbits. The screws were analysed macroscopically, by

histology, micro-CT and biomechanically at both two and six weeks post-implantation. The HA

coated screws demonstrated excellent biocompatibility. At two weeks the HA coated screws demonstrated

a significant increase in removal torque values as well as a strong trend towards higher

pull-out forces. In addition histology confirmed a higher degree of osseointegration and direct

bone to implant contact. At six weeks no difference in pull-out force and removal torque could be

detected. SEM images confirmed the absence of any residual HA coating indicating a fast coating

degradation in-vivo. The low level of removal torque after full osseointegration at 6 weeks supports

the feasibility of safe and easy removal of the implant. The HA coating under study appears

to offer a unique characteristic of enhanced fixation with a minimal increase in removal torque

after full osseointegration. This may be of value in clinical applications where it is necessary to

assure both screw fixation and later removal.

The water sorption properties and the dielectric spectroscopy response of calcined Upsalite?, a novel mesoporous and amorphous magnesium carbonate material candidate for several life-science based application areas, were investigated. The calcination of Upsalite? at 250°C, which removes organic groups present in the uncalcined material, is found to significantly affect the behaviour of adsorbed water. The proportion of free to bound water is considerably higher in the calcined material as compared to the uncalcined counterpart for relative humidities above ? 80 %. The amount of free water in calcined Upsalite? remains high even when the relative humidity is subsequently decreased and is the most likely cause of crystallization of the material into nesquehonite upon high humidity storage. In chorus, the presence of organic groups in uncalcined Upalite? most likely accounts for the higher binding degree of adsorbed water and, thus, the less likelihood of water-induced crystallization of this version of the material. Two dielectric relaxation processes were observed in calcined Upsalite? and were attributed to a Maxwell-Wagner and a Stern-layer relaxation process, respectively. The presented results create a fundamental understanding of water interaction properties in the novel mesoporous magnesium carbonate material Upsalite? and are expected to facilitate optimization of the stability of the material while simultaneously ensuring the lack of toxic surface groups; properties of importance for novel drug formulations and other life-science applications.