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Ultrasound-activated agents comprised of 5FU-bearing nanoparticles bonded to microbubbles inhibit solid tumor growth and improve survival.

ABSTRACT: Nanoparticle (NP) drug delivery vehicles may eventually offer improved tumor treatments; however, NP delivery from the bloodstream to tumors can be hindered by poor convective and/or diffusive transport. We tested whether poly(lactic-co-glycolic acid) NP delivery can be improved by covalently linking them to ultrasound (US)-activated microbubbles in a "composite-agent" formulation and whether drug 5-fluorouracil (5FU)-loaded NPs delivered in this fashion inhibit the growth of tumors that are typically not responsive to intravenously administered 5FU. After intravenous composite-agent injection, C6 gliomas implanted on Rag-1(-/-) mice were exposed to pulsed 1 MHz US, resulting in the delivery of 16% of the initial NP dose per gram tissue. This represented a five- to 57-fold increase in NP delivery when compared to multiple control groups. 5FU-bearing NP delivery from the composite-agent formulation resulted in a 67% reduction in tumor volume at 7 days after treatment, and animal survival increased significantly when compared to intravenous soluble 5FU administration. We conclude that NP delivery from US-activated composite agents may improve tumor treatment by offering a combination of better targeting, enhanced payload delivery, and controlled local drug release.

SUBMITTER: Burke CW

PROVIDER: S-EPMC3916048 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Ultrasound-activated agents comprised of 5FU-bearing nanoparticles bonded to microbubbles inhibit solid tumor growth and improve survival.

Burke Caitlin W CW Alexander Eben E Timbie Kelsie K Kilbanov Alexander L AL Price Richard J RJ

Molecular therapy : the journal of the American Society of Gene Therapy 20131031 2

Nanoparticle (NP) drug delivery vehicles may eventually offer improved tumor treatments; however, NP delivery from the bloodstream to tumors can be hindered by poor convective and/or diffusive transport. We tested whether poly(lactic-co-glycolic acid) NP delivery can be improved by covalently linking them to ultrasound (US)-activated microbubbles in a "composite-agent" formulation and whether drug 5-fluorouracil (5FU)-loaded NPs delivered in this fashion inhibit the growth of tumors that are typ ...[more]

PMID: 24172867

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Project description:Microbubbles (MBs) are optimal ultrasound contrast agents because their unique acoustic response allows for exquisite sensitivity in vivo. This unique response is derived from MBs' elasticity that allows them to oscillate differently from surrounding tissues. While the main use of MBs in the clinic is for cardiac and perfusion imaging, imparting MBs with bioresponsive properties would expand their use to detect pathophysiologic changes. This can be achieved by damping MBs' oscillations to silence their signal and rescuing it when they encounter the biomarker of interest to improve detection and specificity of diseases such as deep vein thrombosis (DVT). Here, we demonstrate that conjugating perfluorobutane-filled MBs with hyaluronic acid (HA) and cross-linking HA with biodegradable linkers eliminates harmonic signal because of increased MB stiffness and decreased oscillation. In this proof-of-concept study, we used a reversible pH-sensitive cross-linker to establish and validate this targeted and activatable pH-sensitive MB (pH-MB) platform. Conjugation of HA to MBs and targeting of pH-MBs to CD44-positive cells were validated. Harmonic signal loss due to stiffening of pH-MBs' shell was confirmed using a clinical ultrasound scanner equipped with Cadence contrast pulse sequencing. pH-MBs imaged before and after acidification increased harmonic signal fivefold. Because the cleavage of the cross-linker we used is reversible, harmonic signal was silenced again when the acidic suspension was neutralized, confirming that harmonic signal is dependent on the cross-linked HA. The rate of rise and the magnitude of harmonic signal increase could be manipulated by varying the phospholipid composition and the number of HA cross-linkers, indicating that the platform can be tuned to the desired response needed. In this study, we established the feasibility of using targeted and activatable MBs and plan to apply this platform to aid in the diagnosis and management of patients with DVT and potentially other conditions.

Project description:Platelet-endothelial interactions have been linked to increased inflammatory activation and a prothrombotic state in atherosclerosis. The interaction between von Willebrand factor (vWF)-A1 domain and platelet glycoprotein (GP) Ib/IX plays a significant role in mediating the adhesion of platelets to the injured endothelium. In the present study, contrast-enhanced ultrasound (CEU) molecular imaging with microbubbles bearing the vWF-A1 domain was performed to non-invasively monitor activated platelets on the vascular endothelium in the procession of atherosclerosis. A targeted CEU contrast agent was prepared by attaching the vWF-A1 domain to the shell of microbubbles (MbA1). Rat isotype control antibody was used to produce control (Mbctrl) microbubbles. The binding of MbA1 and Mbctrl to activated platelets was assessed in in vitro flow chamber experiments. Apolipoprotein E (ApoE-/-) deficient mice were studied as a model of atherosclerosis. At 8, 16 and 32 weeks of age, CEU molecular imaging of the proximal aorta with MbA1 and Mbctrl was performed and the imaging signals from microbubbles were quantified. Atherosclerotic lesion severity and platelets on the endothelial surface were assessed by histology and immunohistochemistry. In in vitro flow chamber studies, attachment of MbA1 to activated platelets on culture dishes was significantly greater than that of Mbctrl across a range of shear stresses (P<0.05). The attachment of Mbctrl was sparse and not related to the aggregated platelets. As lesion development progressed in the ApoE-/- mice, molecular imaging of activated platelets demonstrated selective signal enhancement of MbA1 (P<0.05 vs. Mbctrl) at all ages. Selective signal enhancement from MbA1 increased from 8 to 32 weeks of age. Immunohistochemistry for GPIIb revealed the presence of platelets on the endothelial cell surface in each group of ApoE-/- mice and that the degree of platelet deposits was age-dependent. The results of the present study indicated that non-invasive CEU molecular imaging with targeted microbubbles bearing the vWF-A1 domain could not only detect activated platelets on the vascular endothelium but also indicate lesion severity in atherosclerosis.

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Dataset Information

Ultrasound-activated agents comprised of 5FU-bearing nanoparticles bonded to microbubbles inhibit solid tumor growth and improve survival.

Publications

Ultrasound-activated agents comprised of 5FU-bearing nanoparticles bonded to microbubbles inhibit solid tumor growth and improve survival.

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