Biochemical Interactions through Microscopic Techniques: Structural and Molecular Characterization

Probing the reduction of adhesion forces between biofilms and anti-biofouling filtration membrane surfaces using FluidFM technology

Biofouling is a persistent problem in many sectors (healthcare, medicine, marine, and membrane filtration processes). To control the biofouling of surfaces, it is essential to overcome or reduce the adhesion forces between biofilms and surfaces. To access and understand the molecular basis of these interactions, atomic force microscopy (AFM) is a well-suited technology that can measure adhesion forces at the piconewton level. However, AFM-based existing methods only probe interactions between individual cells and surfaces, which is not representative of realistic conditions given that bacteria mainly exist in biofilms. We develop here an original method using FluidFM, a combination of AFM and microfluidics, to probe the adhesion forces between biofilms and filtration membranes modified with an anti-biofouling agent, vanillin. This strategy involves i) growing bacterial biofilms on micrometer-sized polystyrene beads, ii) aspirating these biofilm beads at the aperture of microfluidic cantilevers and iii) using them as probes in force spectroscopy experiments. The results obtained first showed that COOH-functionalized polystyrene beads are more suitable for bacterial growth, and that biofilms obtained after 3 h of incubation could be used with FluidFM. Then, biofilm-scale force spectroscopy experiments showed a significant decrease in adhesion forces, adhesion work, and adhesion events after membrane modification, demonstrating the potential of vanillin-coated membranes to reduce biofouling. In addition, the comparison between results at the individual cell and biofilm scales highlighted the complexity of polymeric matrix unbinding and/or unfolding in the biofilm, showing that individual cells behave differently from biofilms. Overall, this method could have implications in the fields of materials science, chemical engineering, health, and the environment.

Electrochemiluminescence of Semiconductor Quantum Dots and Its Biosensing Applications: A Comprehensive Review

Electrochemiluminescence (ECL) is the chemiluminescence triggered by electrochemical reactions. Due to the unique excitation mode and inherent low background, ECL has been a powerful analytical technique to be widely used in biosensing and imaging. As an emerging ECL luminophore, semiconductor quantum dots (QDs) have apparent advantages over traditional molecular luminophores in terms of luminescence efficiency and signal modulation ability. Therefore, the development of an efficient ECL system with QDs as luminophores is of great significance to improve the sensitivity and detection flux of ECL biosensors. In this review, we give a comprehensive summary of recent advances in ECL using semiconductor QDs as luminophores. The luminescence process and ECL mechanism of semiconductor QDs with various coreactants are discussed first. Specifically, the influence of surface defects on ECL performance of semiconductor QDs is emphasized and several typical ECL enhancement strategies are summarized. Then, the applications of semiconductor QDs in ECL biosensing are overviewed, including immunoassay, nucleic acid analysis and the detection of small molecules. Finally, the challenges and prospects of semiconductor QDs as ECL luminophores in biosensing are featured.