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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., Journal of Colloid and Interface Science, 622, ISSN:0021-9797, ISSN:1095-7103

Reusable face masks are an important alternative for minimizing costs of disposable and surgical face masks during pandemics. Often complementary to washing, a prolonged lifetime of face masks relies on the incorporation of self-cleaning materials. The development of self-cleaning face mask materials requires the presence of a durable catalyst to deactivate contaminants and microbes after long-term use without reducing filtration efficiency. Herein, we generate self-cleaning fibers by functionalizing silicone-based (polydimethylsiloxane, PDMS) fibrous membranes with a photocatalyst. Coaxial electrospinning is performed to fabricate fibers with a non-crosslinked silicone core within a supporting shell scaffold, followed by thermal crosslinking and removal of the water-soluble shell. Photocatalytic zinc oxide nanoparticles (ZnO NPs) are immobilized on the PDMS fibers by colloid-electrospinning or post-functionalization procedures. The fibers functionalized with ZnO NPs can degrade a photo-sensitive dye and display antibacterial properties against Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) due to the generation of reactive oxygen species upon irradiation with UV light. Furthermore, a single layer of functionalized fibrous membrane shows an air permeability in the range of 80–180 L/m2s and 65% filtration efficiency against fine particulate matter with a diameter less than 1.0 µm (PM1.0). Graphical abstract

Urinary tract infections (UTIs) are among the most predominant microbial diseases, leading to substantial healthcare burdens and threatening human well-being. UTIs can become more critical when caused by Pseudomonas aeruginosa, particularly by antimicrobial-resistant types. Thereby a rapid diagnosis and identification of the antimicrobial-resistant P. aeruginosa can support and guide an efficient medication and an effective treatment toward UTIs. Herein, we designed a platform for prompt purification, and effective identification of P. aeruginosa to combat the notorious P. aeruginosa associated UTIs. A peptide (QRKLAAKLT), specifically binding to P. aeruginosa, was grafted onto PEGylated magnetic nanoclusters and enabled a successful capture and enrichment of P. aeruginosa from artificial human urine. Rapid identification of antimicrobial resistance of the enriched P. aeruginosa can be moreover accomplished within 30 min. These functionalized magnetic nanoclusters demonstrate a prominent diagnostic potential to combat P. aeruginosa associated UTIs, which can be extended to other P. aeruginosa involved infections., Biosensors and Bioelectronics, 222, ISSN:0956-5663, ISSN:1873-4235

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.

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 (

Chronic wounds are not only a burden for patients but also challenging for clinic treatment due to biofilm formation. Here, we utilized the phenomenon that chronic wounds possess an elevated local pH of 8.9 and developed pH-sensitive silica nanoparticles (SiNPs) to achieve a targeted drug release on alkaline wounds and optimized drug utility. Chlorhexidine (CHX), a disinfectant and antiseptic, was loaded into SiNPs as the model drug. The loaded CHX displayed a release 4 - 5 fold higher at pH 8.0 and 8.5 than at pH 6.5, 7.0 and 7.4. CHX-SiNPs furthermore exhibited a distinctive antibacterial activity at pH 8.0 and 8.5 against both Gram-negative and -positive bacterial pathogens, while no cytotoxicity was found according to cell viability analysis. The CHX-SiNPs were further formulated into alginate hydrogels to allow ease of use. The antibacterial efficacy of CHX-SiNPs was then studied with artificial wounds on ex vivo human skin. Treatment with CHX-SiNPs enabled nearly a 4-lg reduction of the viable bacterial cells, and the alginate formulated CHX-SiNPs led to almost a 3-lg reduction compared to the negative controls. The obtained results demonstrated that CHX-SiNPs are capable of efficient pH-triggered drug release, leading to high antibacterial efficacy. Moreover, CHX-SiNPs enlighten clinic potential towards the treatment of chronic wound infections. STATEMENT OF SIGNIFICANCE: A platform for controlled drug release at a relatively high pH value i.e., over 8, was established by tuning the physical structures of silica nanoparticles (SiNPs). Incorporation of chlorhexidine, an antimicrobial agent, into the fabricated SiNPs allowed a distinctive inhibition of bacterial growth at alkaline pHs, but not at acidic pHs. The efficacy of the SiNPs loaded with chlorhexidine in treating wound infections was further validated by utilizing ex vivo human skin samples. The presented work demonstrates clinic potential of employing alkaline pH as a non-invasive stimulus to achieve on-demand delivery of antimicrobials through SiNPs, showcasing a valuable approach to treating bacterial infections on chronic wounds.

To control material-associated bacterial infections, understanding the underlying mechanisms of bacteria and surface interactions is essential. Here we focused on studying how material mechanical and chemical properties can impact bacterial adhesion, using polydimethylsiloxane (PDMS) as a model material. To this end, PDMS surfaces of different stiffness were coated with a 2 nm highly cross-linked PDMS-like polymer film to confer comparable surface chemistry, while retaining similar mechanical properties for coated and uncoated samples. The uncoated samples showed increased interfacial adhesion force with the decrease of Young's modulus, whereas the nanolayer deposition yielded a comparable adhesion force for all surfaces. The Gram negative strains Escherichia coli, its fimbriae mutants and Pseudomonas aeruginosa as well as the Gram positive strain Staphylococcus epidermidis were analysed for their adhesion on these surfaces. For each bacterial strain similar numbers were found on the coated surfaces of different PDMS species, whereas the numbers on the uncoated surfaces increased several fold with the decrease of material modulus. Similar adhesion behaviour was also observed for the negatively charged abiotic polystyrene beads of similar size to bacteria. These results strongly suggest that the interfacial chemistry of the PDMS rather than the material mechanical properties plays a critical role in bacterial adhesion.

Among nosocomial infections, materials associated infections are the most frequent and severe due to biofilm formation. To prevent bacterial colonization, understanding the underlying interaction between bacteria and surface is fundamental. Herein we focused on studying how material viscoelasticity and physicochemistry can influence bacterial adhesion, using polydimethylsiloxane (PDMS) as a model material. To delineate the impact caused by bulk material from interfacial physicochemical properties, a 2 nm PDMS-like polymer layer was coated onto PDMS surfaces of different stiffness to confer comparable surface chemical properties, while retaining similar viscoelasticity for coated and uncoated PDMS species. Although the uncoated samples displayed increasing interfacial adhesion force with the decreasing Young's modulus, the nanolayer coating ensured comparable forces independent of material stiffness. The Gram negative strains Escherichia coli and Pseudomonas aeruginosa and the Gram positive strain Staphylococcus epidermidis were found to adhere respectively in similar numbers on the coated surfaces of different PDMS species, whereas the amount on the uncoated surfaces increased several fold with the decreasing modulus. The similar adhesion behaviour was noticed for abiotic polystyrene beads of similar size to bacteria, demonstrating that the interfacial chemistry of the PDMS rather than the material viscoelasticity plays a crucial role in bacterial adhesion.

Titanium (Ti)-based implants are broadly applied in the medical field, but their related infections can lead to implant failure. Photo-irradiation of metal materials to generate antimicrobial agents, an alternative to antibiotics, is a promising method to reduce bacterial infection and antibiotic usage. It is therefore important to understand how bacterial pathogens respond to Ti surfaces. Here, Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus, the most prevalent pathogens linked to healthcare-associated infections, were used as model strains. Two different kinds of Ti surfaces respectively stored in dry condition and 0.9 % NaCl solution were applied. Upon UV irradiation and in the absence of bacteria, both tested surfaces exhibited similar bactericidal activity, even though the surfaces stored in 0.9 % NaCl solution generated a slightly higher level of reactive oxygen species (ROS). Interestingly, P. aeruginosa and S. aureus responded to the irradiated Ti surfaces differently regarding interaction time: the number of viable P. aeruginosa was reduced up to 90 % after 30 min interaction with the treated surfaces compared to the untreated ones, but this reduction is lessened to 69 %–81 % after 240 min. By contrast, UV treatment of surfaces did not impact the viability of S. aureus after 30 min interaction, however, led to more than 99 % reduction after 240 min incubation. These results provide first experimental evidence that Gram negative and positive bacterial species respond to ROS with different inactivation kinetics. This work also demonstrated that treatment with photo-irradiation in the absence of bacteria conferred Ti surfaces with efficient bactericidal activity.

Objective To assess the symptoms associated with long-term Double-J ureteral stenting including the influence of biofilms on ureteral stents. Methods Patients with long-term (> 8 weeks) uni- or bilateral ureteral stents completed the Ureteral Stent Symptom Questionnaire (USSQ) at the day of stent exchange. Repeated assessment of patients was possible to allow for analysis of intra-individual changes. Assessment of biofilm mass on the stents was performed according to a validated method, its correlation with the USSQ total score was defined as primary outcome. Secondary outcomes included further analyses of stent-associated symptoms and their temporal course. Results A total of 87 stent indwelling periods in 35 patients were investigated. Median USSQ total score did not differ significantly between unilateral and bilateral stenting (42 vs. 39 points; p = 0.17). An increasing total stent treatment time up to study inclusion did not correlate with the USSQ total score, but was significantly correlated with less urinary symptoms and a better quality of life. USSQ total score and subscores within individual patients did not significantly increase or decrease over the sequence of stent indwelling periods. Higher total biofilm masses were not associated with higher USSQ total scores or subscores. Conclusion Long-term Double-J stenting provides a valuable treatment option, if stent-associated symptoms are low during the initial indwelling period. Thus, symptoms remain stable over the long-term course and the majority of patients is satisfied with the treatment. Furthermore, biofilm formation on ureteral stents does not seem to be the relevant driver of symptoms.

A facile methodology to durably modify cellulose fibers by forming in-situ phosphine oxide macromolecular physical networks is developed in this work. Such networks were formed by treating the cellulose fibers with a mixture of Michael adducts [trivinyl phosphine oxide (TVPO) and cyclic amines (piperazine and 2,4,6-tri(piperazine-1-yl)-1,3,5-triazine)] followed by a click crosslinking reaction initiated by dry heat, microwave, or steaming process. The in-situ phosphine oxide network is integrated within the cellulose fibers to produce a durable treatment against laundering. NMR and SEM analysis of the treated fibers verified the in-situ formation of phosphine oxide macromolecules in the bulk of cellulose fiber. The treatment was homogenous and achieved an outstanding phosphorus (P) retention (>95%) after even 50 laundry cycles. The treated cotton exhibited excellent fire retardant properties with a limiting oxygen index value >27% and passed the Swiss vertical flammability test at 2 wt% P. Analysis of evolved gasses during thermal decomposition of treated cellulose supported both the condensed and gas phases mechanism. The flame retardant treatment was further adapted to include antimicrobial properties by in-situ formation of silver nanoparticles within the cellulose fibers using a single-step process to demonstrate the versatility of this novel treatment methodology. The treated fabric exhibited excellent antimicrobial as well as flame retardant properties and was also durable to 50 laundry cycles. Contact angle measurements and moisture management test confirmed the excellent comfort behavior of the treated cellulose fabric.

A simple one-step solventless in-situ reduction method was developed to prepare silver nanoparticle (AgNP) based polymer composites using different silver precursors and thermoplastic polymers. This method utilizes the mild reducing environment of thermoplastic polymer melts to convert silver precursors to AgNPs during the extrusion process. Complete reduction of Ag2O with broad AgNP size distribution (20 ± 18 nm) in polyamide 6 (PA6) was obtained after 5 min processing. For same matrix, the uniformity of AgNPs improved significantly after 10 min processing time, associated with a slight increase in the particle diameter (26 ± 9 nm). No significant impact of in-situ AgNP synthesis method on chemical and macromolecular characteristics of polyamide 6 was detected. When this method was used to synthesize AgNPs in polylactic acid and polypropylene, the influence of surface energy of polymer melt was evident. Reduction of Ag2O in polylactic acid (at 165 °C) was slower compared to PA6 and 95 ± 3% Ag2O reduction was achieved after 10 min of processing. When polypropylene was used as the matrix, only 60% reduction of Ag2O was achieved, possibly due to poor wetting of the silver precursor, owing to the low surface energy of polypropylene. AgNP-PA6 composites were also successfully prepared using Ag2CO3 and Ag-palmitate as precursors. To demonstrate the potential application of such composites in food packaging, the silver release and antibacterial activity of AgNP-PA6 composite were also studied. Though the composites released 500 times less silver compared to the permitted limits of different safety standards, they exhibited an excellent antibacterial activity against a typical food pathogen (Listeria monocytogenes) already at a low level of AgNP loading i.e. 0.5 wt%.