Attenuation study with hemoglobin microbubbles for acoustic blood oxygen level dependent imaging

Abstract

A new microbubble-based biosensor for BOLD imaging applications was developed and acoustically characterized using ultrasound. The biosensor design was based on the use of hemoglobin protein as a shell component of microbubbles, which undergoes changes in structure upon oxygen binding, leading to changes in the mechanical properties of the shells. The acoustic characterization was performed using an ultrasound acoustic transducer with a center frequency of 1 MHz, which was used both as a source and a receiver. The transducer transmitted 5 us pulses at a PRF of 10 Hz at peak-negative pressures ranging from 0 to 0.1 MPa. The microbubbles were then excited, and their signals were measured and transformed to frequency domain using Fast-Fourier transform, from which attenuation was computed. The oxygen-saturated hemoglobin microbubbles were added to either oxy or deoxy PBS at a concentration of 4.5 × 6 mB/ml to collect the microbubble signal. The results showed that the biosensor has potential for use in BOLD imaging applications. The results showed that hemoglobin microbubbles were displaying distinct attenuation properties between oxy and deoxy conditions, thereby showing response to different levels of oxygen.