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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

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 (

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.

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%.