The design and synthesis of macrocyclic cation receptors is very well documented in supramolecular chemistry.1 Despite anion recognition being a relatively new area of research, both positively charged and neutral receptors for anionic species have been prepared in the last few years.2 Recently we described the synthesis of neutral bifunctional receptors for the simultaneous complexation of hydrophilic anions and cations in organic media.3 In these receptors, the appropriate binding sites for both anionic and cationic species are covalently combined in a neutral molecule.4 In this Communication, we report our preliminary results on simultaneous transport of cations and anions through a supported liquid membrane (SLM) assisted by a novel type of neutral bifunctional receptor. To the best of our knowledge, this is the first example of carrier-assisted cotransport, in which the anion and cation of a hydrophilic salt are bound and transported simultaneously through a membrane.5-7Our synthetic strategy is based on the attachment of both cation and anion binding sites to the rigid lipophilic calix[4]-

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A new methodology for detecting the microbiological state of a wound dressing in terms of its colonization with pathogenic bacteria such as Staphylococcus aureus or Pseudomonas aeruginosa has been developed. Here we report how stabilized lipid vesicles containing self-quenched carboxyfluorescein dye are sensitive to lysis only by toxins/virulence factors from P. aeruginosa and S. aureus but not by a non-toxic Escherichia coli species. The development of the stabilized vesicles is discussed and their response to detergent (triton), bacterial toxin (α-hemolysin) and lipases (phospholipase A(2)). Finally, fabrics with stabilized vesicles attached via plasma deposited maleic anhydride coupling are shown visibly responding to S. aureus (MSSA 476) and P. aeruginosa (PAO1) but not E. coli DH5α in a prototype dressing.

Wound infection is commonly observed after surgery and trauma but is difficult to diagnose and poorly defined in terms of objective clinical parameters. The assumption that bacteria in a wound correlate with infection is false; all wounds contain microorganisms, but not all wounds are clinically infected. This makes it difficult for clinicians to determine true wound infection, especially in wounds with pathogenic biofilms. If an infection is not properly treated, pathogenic virulence factors, such as rhamnolipids from Pseudomonas aeruginosa , can modulate the host immune response and cause tissue breakdown. Life-threatening sepsis can result if the organisms penetrate deep into host tissue. This communication describes the sensor development for five important clinical microbial pathogens commonly found in wounds: Staphylococcus aureus , P. aeruginosa , Candida albicans/auris, and Enterococcus faecalis (the SPaCE pathogens). The sensor contains liposomes encapsulating a self-quenched fluorescent dye. Toxins, expressed by SPaCE infecting pathogens in early-stage infected wounds, break down the liposomes, triggering dye release, thus changing the sensor color from yellow to green, an indication of infection. Five clinical species of bacteria and fungi, up to 20 strains each (totaling 83), were grown as early-stage biofilms in ex vivo porcine burn wounds. The biofilms were then swabbed, and the swab placed in the liposome suspension. The population density of selected pathogens in a porcine wound biofilm was quantified and correlated with colorimetric response. Over 88% of swabs switched the sensor on (10 7 –10 8 CFU/swab). A pilot clinical study demonstrated a good correlation between sensor switch-on and early-stage wound infection.

Liposomes containing lipids and polydiacetylene (PDA) are hybrid systems encompassing both a fluid phospholipid membrane and a polymer scaffold (PDA). However, the biophysical role of PDA in such liposomes is not well understood. In this report, we studied the effects of photopolymerization of PDA on the stability of lipid-PDA liposomes, and their sensitivity to selected purified toxins and bacterial supernatants, using a fluorescence assay. Of the three different types of liposomes with variable lipid chain lengths that were chosen, the degree of polymerization had a significant impact on the long-term stability, and response, to external microbial exotoxins secreted by pathogenic bacteria, namely, Staphylococcus aureus and Pseudomonas aeruginosa. The degree of polymerization of TCDA played an important role in lipid-chain-length-dependent stabilization of lipid-PDA liposomes, as well as in their response to bacterial toxins of S. aureus and P. aeruginosa.