Selective recognition and imaging of bacterial model membranes over mammalian ones by using cationic conjugated polyelectrolytes

Abstract

The development of new tools for the detection and fluorescence imaging of bacteria is of great interest in clinical diagnosis and food and environmental safety. In this work, we have explored the ability of two cationic fluorene-based conjugated polyelectrolytes, HTMA-PFP and HTMA-PFNT, emitting in the blue and red spectral regions respectively, to selectively label bacterial over mammalian cells. With this end in view, vesicles with lipid compositions mimicking those of bacterial or mammalian membranes were used as model membranes to explore the interaction of the polyelectrolytes with both systems in samples containing either a single type of vesicle or a mixture of both. Changes in the intrinsic fluorescence of HTMA-PFP and HTMA-PFNT were used to quantify the affinity of these polyelectrolytes for the model lipid membranes, while quenching experiments were employed to evaluate their selectivity to each lipid system. In addition, fluorescence microscopy experiments were performed to check the ability of polyelectrolytes to label the vesicles without affecting their integrity. Results showed that both polyelectrolytes rapidly label the model vesicles but they preferentially bind to those mimicking bacterial membranes, HTMA-PFNT being much more selective to this type of membranes than HTMA-PFP. Preliminary experiments with living bacteria and mammalian cells support this conclusion, showing that in samples with both types of cells together, HTMA-PFNT only images the bacterial cells, thus evidencing its potential use for the selective recognition and imaging of bacterial presence.

Synthesis and Characterization of a Novel Green Cationic Polyfluorene and Its Potential Use as a Fluorescent Membrane Probe

“…From this fit, a value of K P = 9.4 × 10 5 was obtained for the anionic vesicles, which indicates a very high affinity of HTMA-PFBT for this type of membranes, presumably because of the electrostatic interactions between the ammonium groups of the polyelectrolyte and the PG polar heads. This value was very similar to that obtained for the red polyelectrolyte HTMA-PFNT and higher than that calculated for the blue one [12,30,44,46]. In the case of the PC LUVs, the K P value was ~100 times lower than that corresponding to the PG vesicles, evidencing the higher preference of HTMA-PFBT to anionic membranes.…”

Development of A New Delivery System Based on Drug-Loadable Electrospun Nanofibers for Psoriasis Treatment

“…Such a biodegradable, biocompatible, bioadhesive, and low-toxic polymer is already commercialized, and used in other biomedical applications, and has already shown its suitability for the creation of these nanostructured systems with the appropriate release characteristics [26,27,28,29,30]. Additionally, this polymer not only allows the possibility of being used as the main building polymer for the creation of nanofibers, but also allows combining with other materials, such as fluorene-based copolymers [31,32], in order to combine functional properties within the same nanostructure [26,33,34]. The morphological characterization of these nanofibers, together with their encapsulation capacity, stability over time, and activity of the encapsulated compounds are also analyzed in this study.…”

Poly(methyl vinyl ether-alt-maleic acid) and ethyl monoester as building polymers for drug-loadable electrospun nanofibers

“…In both cases, blue-shift emission occurs with respect to their corresponding spectrum in water solution. This observation has previously been linked to the possibility that the conjugate chains in the polyelectrolytes are ordered or stretched and without forming aggregates 42 . This hypothesis, together with the fact that no shift was observed for PMVE/MA-Ac nanofibers when combined with HTMA-PFP, might explain why nanofibers of PMVE/MA-Ac blended with HTMA-PFNT gave no suitable nanofibers when electrospun.…”