Abstract
To improve therapeutic efficacy of nanocarrier drug delivery systems, it is essential to improve their uptake and penetration in tumour tissue, enhance cellular uptake and ensure efficient drug release at the tumour site. Here we introduce a tumour targeting drug delivery system based on the ultrasound-mediated delivery of enzyme sensitive liposomes. These enzyme sensitive liposomes are coated with cleavable poly(ethylene glycol) (PEG) which will be cleaved by two members of the enzyme matrix metalloproteinase family (MMP-2 and MMP-9). Cleavage of the PEG coat can increase cellular uptake and will destabilize the liposomal membrane which can result in accelerated drug release. The main aim of the work was to study the effect of focused ultrasound and microbubbles on the delivery and therapeutic efficacy of the MMP sensitive liposome. The performance of the MMP sensitive liposome was compared to a non-MMP sensitive version and Doxil-like liposomes. In vitro, the cellular uptake and cytotoxicity of the liposomes were studied, while in vivo the effect of ultrasound and microbubbles on the tumour accumulation, biodistribution, microdistribution, and therapeutic efficacy were investigated. For all tested liposomes, ultrasound and microbubble treatment resulted in an improved tumour accumulation, increased extravasation, and increased penetration of the liposomes from blood vessels into the extracellular matrix. Surprisingly, penetration depth was independent of the ultrasound intensity used. Ultrasound-mediated delivery of free doxorubicin and the Doxil-like and MMP sensitive liposome resulted in a significant reduction in tumour volume 28 days post the first treatment and increased median survival. The MMP sensitive liposome showed better therapeutic efficacy than the non-MMP sensitive version indicating that cleaving the PEG-layer is important. However, the Doxil-like liposome outcompeted the MMP and non-MMP sensitive liposome, both with and without the use of ultrasound and microbubbles.
Highlights
Successful treatment of cancer remains a challenge for many solid tumour types
We introduce a dual tumour targeting drug delivery system based on ultrasound-mediated delivery of matrix metalloproteinase (MMP) sensitive liposomes coated with poly(ethylene glycol) (PEG)
The main aim of the work was to study the effect of focused ultrasound in combination with microbubbles on the delivery and therapeutic efficacy of the MMP sensitive liposome
Summary
Successful treatment of cancer remains a challenge for many solid tumour types. Conventional chemotherapy is used alone or in combination with other treatment modalities and is based on systemic administration of drugs which often lacks cancer specificity, causing severe side-effects. Tumour tissue lacks lymphatic drainage and due to uncontrolled growth of tumours, endothelial cells are poorly aligned and have large fenestrations, resulting in leaky vasculature. These anatomical irregularities result in leakage and accumulation of components from the blood plasma into tumour tissue, which makes the Journal of Controlled Release 325 (2020) 121–134
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