Nanotechnology (Commonwealth Union) – Sepsis occurs when the immune system responds to infectious component in an unregulated manner. The need for the appropriate response is key for a healthy individual an excessive immune response beyond what is required can result in damage within the body.
The Korea Institute of Materials Science (KIMS) in South Korea, led by President Chul-jin Choi, has developed a label-free surface-enhanced Raman scattering (SERS) technique that quickly identifies a very small amount of living bacteria. The research team, led by Senior Researcher Minyoung Lee and Principal Researcher Sunggyu Park of the Advanced Bio and Healthcare Materials Research Division at KIMS, developed this technique. The method relies on directly growing plasmonic metal nanostructures on and around the bacterial cells, which amplifies the signals necessary for detection. It can detect trace amounts of bacteria in less than 1 h without the need for conventional culture-based amplification, and can assess bacterial responses to antibiotics within 2 h. The development could lead to faster diagnosis of serious infections, including sepsis, while helping clinicians select more effective antibiotic treatments.
Sepsis is a life-threatening condition that occurs when the body’s response to infection becomes dysregulated and causes organ dysfunction. Identifying the microorganism that caused the infection and administering an effective antibiotic without delay is crucial to improving patient outcomes. But at the beginning of an infection, the amount of bacteria in the blood is very small, so it is difficult to find them directly. Traditionally blood culture methods depend on growing the bacteria in a laboratory before identifying the causative pathogen and testing its antibiotic susceptibility. That means it could take many hours or even days before final results are available. This has led to an increasing demand for diagnostic methods that can rapidly detect live infectious bacteria and determine which antibiotics are likely to be effective against them.
KIMS has already developed super sensitive biosensor technologies to detect sepsis related protein biomarkers from blood samples using three-dimensional plasmonic nanostructures. The latest research builds on that work, by directly detecting the living bacteria that cause infections, and not just the biomarkers linked to the disease. With this approach, researchers can also determine bacterial responses to antibiotics in a much shorter time.
To develop the method, the research team developed an analytical technique based on SERS, using bacterial cells as nucleation points for the formation of nanostructures. Plasmonic metal nanostructures are grown directly on and around the cells to create intense electromagnetic fields that enhance the bacteria’s inherent Raman signals, making them easier to be identified.
The researchers refined the technology through three successive stages. Initially, they grew nanostructures around bacterial cells suspended in a solution. They then developed a method to deposit the metal nanostructures directly onto bacterial surfaces. In the final stage, they combined bacterial separation and enrichment with further nanostructure growth directly at the detection site. This progressive optimisation significantly enhanced the system’s sensitivity, improving its capacity to identify bacteria even when present in extremely small concentrations.
SERS is an analytical method that strengthens the naturally weak Raman signals produced by a material through powerful electromagnetic fields, known as plasmonic hot spots. These hot spots develop within nanoscale gaps between metallic nanostructures, such as those made from gold or silver.
“The key to this research is that we directly grow nanostructures where the bacteria are located and combine this approach with separation and enrichment technologies to overcome the limitations of detecting extremely low bacterial concentrations,” said Minyoung Lee, Senior Researcher and project leader at KIMS.
