Antimicrobial Polymer-Peptide Conjugates Based on Maximin H5 and PEG to Prevent Biofouling of E. coli and P. aeruginosa.

Many pathogens, such as Pseudomonas aeruginosa and Escherichia coli bacteria can easily attach to surfaces and form stable biofilms. The formation of such biofilms in surfaces presents a problem in environmental, biomedical, and industrial processes, among many others. Aiming to provide a plausible solution to this issue, the anionic and hydrophobic peptide Maximin H5 C-terminally deaminated isoform (MH5C) has been modified with a cysteine in the C-terminal (MH5C-Cys) and coupled to polyethylene glycol (PEG) polymers of varying sizes (i.e., 2 kDa and 5 kDa) to serve as a surface protective coating. Briefly, the MH5C-Cys was bioconjugated to PEG and purified by size exclusion chromatography while the reaction was confirmed via SDS-PAGE and MALDI ToF. Moreover, the preventive antimicrobial activity of the MH5C-Cys-PEG conjugates was performed via the growth curves method, showing inhibition of bacterial growth after 24 h. The efficacy of these peptide-polymer conjugates was extensively characterized via scanning electron microscopy (SEM), minimum inhibition concentration (MIC), minimum biofilm inhibition concentration (MBIC), and minimum biofilm eradication concentration (MBEC) assays to evaluate their ability to eradicate and prevent the biofilms. Interestingly, this work demonstrated a critical PEG polymer weight of 5 kDa as ideal when coupled to the peptide to achieve inhibition and eradication of the biofilm formation in both bacteria strains. According to the MICs (40 µM) and MBICs (300 µM), we can conclude that this conjugate (MH5C-Cys-5 kDa) has an action that prevents/inhibits the formation of biofilms and the eradication of biofilms (MBEC 500 µM). In contrast, the MH5C-Cys peptide with PEG polymer of 2 kDa did not show inhibition or eradication of the biofilms.

Aptamer-Based Impedimetric Assay of Arsenite in Water: Interfacial Properties and Performance.

In this work, we explore the use of electrochemical methods (i.e., impedance) along with the arsenic-specific aptamer (ArsSApt) to fabricate and study the interfacial properties of an arsenic (As(III)) sensor. The ArsSApt layer was self-assembled on a gold substrate, and upon binding of As(III), a detectable change in the impedimetric signal was recorded because of conformational changes at the interfacial layer. These interfacial changes are linearly correlated with the concentration of arsenic present in the system. This target-induced signal was utilized for the selective detection of As(III) with a linear dynamic range of 0.05-10 ppm and minimum detectable concentrations of ca. 0.8 µM. The proposed system proved to be successful mainly because of the combination of a highly sensitive electrochemical platform and the recognized specificity of the ArsSApt toward its target molecule. Also, the interaction between the ArsSApt and the target molecule (i.e., arsenic) was explored in depth. The obtained results in this work are aimed at proving the development of a simple and environmentally benign sensor for the detection of As(III) as well as in elucidating the possible interactions between the ArsSApt and arsenic molecules.