Ultrasound Detection of Regional Oxidative Stress in Deep Tissues Using Novel Enzyme Loaded Nanoparticles

Abstract

Oxidative stress is a powerful tool that is critical to immune mediated responses in healthy individuals, yet additionally plays a crucial role in development of cancer, inflammatory pathologies and tissue ischemia. Despite this, there remain relatively few molecular tools to study oxidative stress, particularly in living mammals. To develop an intravenously injectable probe capable of labeling sites of oxidative stress in vivo, we designed and fabricated 200 nm CATalase Synthetic Hollow Enzyme Loaded nanoSpheres (catSHELS) using a versatile enzyme nanoencapsulation method. CatSHELS catalyze H2O2 to water and oxygen producing microbubbles that can be detected and imaged using a clinical ultrasound system. CatSHELS were optimized in vitro to maximize ultrasound signal and their functionality was demonstrated in rat ischemic renal injury (IRI) model. Ischemic oxidative injury was induced in a single kidney of normal rats by clamping the renal artery for1 hour followed by two hours of reperfusion. Imaging of both kidneys was performed following the intravenous bolus injection of 1012 catSHELS of the optimized formulation. There was significant increase in ultrasound signal of the injured kidney relative to controls. Our method offers a novel intravenous approach to detect oxidative stress in deep tissues in living animals.

Catalase-Containing Silica Particles as Ultrasound-Based Hydrogen Peroxide Sensors to Determine Infected From Noninfected Fluid Collections in Humans

“…Catalase-containing nanoshell particles help maintain catalase activity by retaining [17,18]. Although catalase-containing silica nanoshells were produced using a different formulation than reported previously, they also generated O 2 microbubbles at H 2 O 2 concentrations of 10 μM and above [17,18]. In this first study geared toward translating this technique to the clinic, we hypothesized that H 2 O 2 elevation could serve as a biomarker to distinguish infected from noninfected fluid collections.…”

“…Future studies will need to evaluate interobserver variability. Third, though microbubble production in the presence of H 2 O 2 has been well documented in the literature, and in this study quantification of H 2 O 2 levels in the fluid samples was not possible [17,18,31]. Amplex Red assay was unreliable because of several factors including biologic complexity of aspirate, sample heterogeneity, and contamination by blood that interferes with the fluorescence readout [32].…”

“…Previous reports describe nanoporous particles containing the enzyme catalase, which is capable of catalyzing H 2 O 2 into oxygen (O 2 ) and water both in vitro and in vivo, while protecting the enzyme from degradation [17,18]. On exposure to US, the released O 2 forms microbubbles that are detectable with standard US equipment ( Fig.…”

Biodegradable Catalase‐Modified Micelles as Ultrasound Contrast Agents for Inflammation Detection

“…[11,12] While most MBs-based UCAs are thin shell structures encapsulated with gas such as air and perfluorocarbons or assemblies of nanoparticles, they can hardly reflect the relevance between MBs and diseases, and some of them are not stable enough in internal environment. [13][14][15][16][17] For H 2 O 2 -related diseases detection, novel H 2 O 2 -responsive MBs-based UCAs are capable of converting endogenous H 2 O 2 to gas MBs in situ, [18][19][20][21][22][23] predominantly oxygen (O 2 ) MBs. The catalytic decomposition of endogenous H 2 O 2 would produce gas to saturate the surrounding fluid that is then nucleated to form gas MBs.…”

“…In order to produce sufficient MBs to achieve higher resolution, the systems need to have superior catalytic activity and high sensitivity. [20,22] In addition, biodegradability of the whole systems is also important because the accumulation of nondegradable products may cause further side effects to the body, thus restricting their translation into clinics. [24][25][26] Some biodegradable polymers-based nanomedicine systems were reported in recent years, showing good biocompatibility and great potential for clinical application.…”