Detection of Methicillin-Resistant Staphylococcus Aureus Bacteria Using Liquid Crystals

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is an essential pathogen for public health and this bacteria commonly cause serious infectious in humans. In recent years, MRSA bacteria are detected by the bacterial culture and nucleic acid-based methods which are time-consuming and labor-intensive. In this study, a novel liquid crystal (LC)-based biosensing system was developed to overcome these limitations. The objective of this study was to detect the presence of MRSA bacteria which prepared within the isotonic water and phosphate buffer saline (PBS). In this system, the binding of MRSA bacteria to the dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP)-coated surface disrupted the orientation of LCs, triggering a transition from a homeotropic orientation to a random one. This transition in the orientation of the LCs was observed as a change from a dark optical LC image to a bright one under a polarized light microscope (POM) and the reflection values of LC molecules were determined by using a spectrometer. Through this sensing mechanism, MRSA bacteria prepared within the isotonic water was detected ranging from the 9.2x10 3 CFU/mL to 9.2x10 7 CFU/mL concentration. Furthermore, MRSA bacteria prepared in PBS was detected in the concentration range of 7.1x10 4 CFU/mL to 7.1x10 8 CFU/mL by using this system.

Liquid Crystal Biosensors: A New Therapeutic Window to Point-of-Care Diagnostics

“…17 The traditional labor-intensive and time-consuming bacterial culture and nucleic acid-based approaches for detecting methicillin-resistant Staphylococcus aureus (MRSA) bacteria have been replaced by LC-based biosensing systems. 18 It was possible to detect the SARS-CoV-2 virus using an LCbased diagnostic kit that could discriminate between COVID-19 samples that are −ve and +ve with an accuracy of 96% and between COVID-19 and influenza types A and B with an accuracy of 93%. This kit can be used for the rapid on-spot point of diagnosis of COVID-19 at border crossings, airports, and other locations.…”

“…The optical detection of the human influenza virus with high spatial resolution was studied using nematic LCs . The traditional labor-intensive and time-consuming bacterial culture and nucleic acid-based approaches for detecting methicillin-resistant Staphylococcus aureus (MRSA) bacteria have been replaced by LC-based biosensing systems …”

“…Second, due to their low interfacial energy (10 –6 to 10 –3 J/m 2 ), the ordering of LCs is sensitive to the chemistry of the substrate and the presence of different biochemical species. , Third, owing to the long-range orientational order of LCs, they can propagate the changes in the interfacial alignment of LC molecules over distances of up to ∼100 μm. − This, in turn, results in amplifying molecular-level interactions into visible optical signals detectable using a polarized optical microscope (POM). These LC-based optical biosensors have been designed to detect chemical and biological species such as lipids, proteins, pathogens, simple electrolytes, surfactants, endotoxins, and synthetic polymers. − …”

“…Before moving on to the discussion of LC biosensors for diagnostic applications, it might be helpful to the reader if we recapitulate the pioneering works that laid the foundation of biomedical interfaces for clinical applications. For the first time, Abbott et al demonstrated that biological lipids can be self-assembled at the aqueous interfaces of LCs, resulting in phospholipid-decorated LC interfaces wherein the mobility of adsorbed lipids is comparable to that of biological membranes. ,, These studies were instrumental in designing membrane mimics to delineate complex lipid–protein interactions which play a significant role in modulating disease states. ,− These interfaces could report real-time enzymatic activity, membrane disruption of antimicrobial peptides, membrane-induced aggregation of amyloid peptides, ligand–receptor binding, and so on. ,− LCs have recently been used to construct functional interfaces for detecting environmental pollutants, small-molecule analytes, toxic metal ions, and disease-causing pathogens. − ,− Using analyte-specific recognition elements such as aptamers and antibodies, highly sensitive multiplexed detection of antigens and biomarkers has been achieved for point-of-care diagnostics. − However, although optical approaches might be more sensitive than electrochemical ones, most end users are turned off by their expense and complexity.…”