Microfluidic evaporator chip for concentration of bacterial samples for SERS identification

Abstract

Sepsis is a serious medical condition in which a person becomes infected with bacteria in his or her bloodstream. The symptoms of sepsis are a result of the immune system’s interaction with the infecting agent. Currently, to diagnose a patient with sepsis, a blood sample must be collected and cultured for 24-48 hours before the infection can be confirmed. In the meantime, a broad-scope antibiotic is administered which may or may not be effective in treating the patient. If the antibiotic is ineffective, a different antibiotic must be chosen. When the results of the blood culture are available, a narrow scope antibiotic, appropriate to treat the infection is administered. However, sepsis has a mortality rate of 18-30% depending on the infecting agent and the treatment is highly time sensitive. Within 24 hours, the syndrome may progress to septic shock and mortality rates reach 50%. Therefore, it is important to quickly and correctly identify the infecting agent and provide immediate targeted treatment.

Surface Enhanced Raman Spectroscopy (SERS) can be used to quickly identify and distinguish between different bacterial strains; however it requires higher bacterial concentrations than are present in the blood during the early stages of sepsis. A microfluidic evaporator chip has been developed to concentrate bacteria samples from 4μl to 100nl; the chip has been evaluated for concentration efficiency on Escherichia coli and methicillin-sensitive Staphylococcus aureus. Various blocking methods using bovine serum albumin (BSA) have been tested to reduce bacterial adhesion to the chip and have improved bacterial recovery to around 70% for both strains tested. Ongoing tests are being performed to improve bacterial recovery and sample purity for identification.