Quantum-dot-modified microbubbles with bi-mode imaging capabilities

Abstract

The aim of this paper was to develop a novel bi-mode ultrasound/fluorescent imaging agentthrough stepwise layer-by-layer deposition of poly(allylamine hydrochloride) (PAH) andCdTe quantum dots (QDs) onto ST68 microbubbles (MBs) produced by sonication of amixture of surfactants (Span 60 and Tween 80). The experiments using photoluminescencespectroscopy and confocal laser scanning microscopy confirmed that CdTe nanoparticleswere successfully adsorbed on the outer surface of the MBs. The static light scatteringmeasurements showed that size distributions of MBs before and after QD deposition metthe size requirements for clinical application. The in vitro and in vivo ultrasonographyindicated that the QD-modified MBs maintained good contrast enhancement properties asthe original MBs. Furthermore, the in vitro ultrasound-targeted microbubble destruction(UTMD) experiment of the QD–MB composites was carried out to validate theability of MBs to deliver QDs for fluorescent imaging. The results showed that theQD-modified MBs not only maintained the capability of ultrasound imaging, butalso could be used as a targeted-drug controlled-release system to deliver theQDs for cell and tissue fluorescent imaging by UTMD. The novel dual-functionalimaging agent has potential for a variety of biological and medical applications.