Interventional Removal of Travelling Microthrombi Using Targeted Magnetic Microbubble, 2024, Li et al.

[SNT Gatchaman]

Interventional Removal of Travelling Microthrombi Using Targeted Magnetic Microbubble
Yongjian Li; Zujie Gao; Xiaobing Zheng; Yunfan Pan; Jinlong Xu; Yan Li; Haosheng Chen

Microthrombus is one of the major causes of the sequelae of COVID-19 and leads to subsequent embolism and necrosis. Due to their small size and irregular movements, the early detection and efficient removal of microthrombi in vivo remain a great challenge.

In this work, an interventional method is developed to identify and remove the traveling microthrombi using targeted-magneticmicrobubbles (TMMBs) and an interventional magnetic catheter. The thrombus-targeted drugs are coated on the TMMBs and magnetic nanoparticles are shelled inside, which allow not only targeted adhesion onto the traveling microthrombi, but also the effective capture by the magnetic catheter in the vessel.

In the proof-of-concept experiments in the rat models, the concentration of microthrombus is reduced by more than 60% in 3 minutes, without damaging the organs. It is a promising method for treating microthrombus issues.

Link | PDF (Advanced Healthcare Materials)

 

[SNT Gatchaman]

The formation of microthrombi (MT) is an important cause of death and disability of the patients infected with COVID-19. The microthrombi are widely found in their tissue sections, especially in the acute death cases. Microthrombi not only are the product of early pathogenesis of COVID-19, in which viruses trigger an inflammatory response and the inflammatory factors cause hypercoagulability by promoting the expression of the tissue factors in the endothelial cells, but also could be the major cause of the “Long COVID”.

 

[SNT Gatchaman]

To achieve the drug-free removal of these travelling microthrombi from the blood flow without false trapping of normal blood cells, a targeted capturing strategy is necessary. Here, we propose a two-step treatment method, the Interventional Microthrombus Removal (IMTR), employing the multifunctional microbubbles and the interventional magnetic technique.

Multifunctional microbubbles have been widely used in the recognition of microthrombi and material transport due to their good dispersion, large specific surface area and efficient specificity recognition [13] and compared with microparticles and droplets, microbubbles have more flexible density and excellent imaging performance.

I'll try and work out what ref 13 is, as it's a bit mangled in the pre-press refs list.

 

[SNT Gatchaman]

[13] A Combined Magnetic-Acoustic Device for Simultaneous, Coaligned Application of Magnetic and Ultrasonic Fields (2018, Advanced Materials Technologies)

[14] Multimodal and multifunctional nanoparticles with platelet targeting ability and phase transition efficiency for the molecular imaging and thrombolysis of coronary microthrombi (2020, Biomaterials Science)

 

[Murph]

Fascinating idea. Usually ideas out of China don't make much splash in the west but this paper is out of Tsinghua university which is China's #2 university, based in Beijing and their #1 tech/science university. Think MIT. So it is probably not junk science and could have some impact.

The primary application is acute covid but obviously it would be a good thing for the microclot people to use to test the theory of microclots in long covid.

 

[SNT Gatchaman]

One of the points is that with their methodology they deliberately created microclots (from larger clots so not amyloid style), filtered them to be between 10 and 100 µm and left them in circulation for 30 minutes before removing them from the IVC, or not in the controls. I'll try and post some summary quotes and results later.

 

[SNT Gatchaman]

Rat microthrombus model

(note these are "ordinary" microthrombi, not fibrin-amyloid microclots)

In this in vitro experiment, human-derived venous blood was used to form microthrombi; in vivo animal experiments, autologous venous blood from living animals was extracted to prepare microthrombi.

The preparation process is as follows: centrifugation at room temperature (1500 rpm, 10 minutes), the blood is divided into two layers after centrifugation, the upper layer is platelet-rich plasma, and the lower layer is a large number of red blood cells and a small amount of white blood cells; The solution was mixed to obtain platelet-rich plasma, and the platelet stain of DiOC6 (concentration 1 μg/ml, Solarbio) was added in a volume ratio of 3:1000, and incubated at room temperature for 10 minutes.

Add recalcification buffer with a volume ratio of 1:10 to restore the coagulation ability, mix quickly and thoroughly, and after 5-10 minutes, the platelet-rich large thrombus can be coagulated. After preparation, the platelet-rich large thrombus was placed in a refrigerator at 4°C and -12°C for about 3 hours and 24 hours, respectively, to allow the thrombus to fully shrink; the thrombus was hardened in liquid nitrogen for about 5 minutes, and the microthrombus were obtained by mechanicalgrinding. First, filter with a filter with a pore sizeof 100 microns to collect the microthrombus particles that can passthrough the filter; then filter with a filter with a pore sizeof 10 microns to collect the microthrombotic particles that do not passthrough the filter.

Thereby microthrombi with a size between 10-100 microns are obtained.

 

[SNT Gatchaman]

Removing microthrombi via interventional catheter

Two stage process: inject TMMBs (targeted magnetic microbubbles) to attach to circulating microthrombi; retrieve via a magnetic-tipped intravascular catheter.

To further validate the interventional microthrombi removal treatment, we investigated the effectiveness and safety of TMMB mediated microthrombi removal in the rat models, as shown in Figure 5A. Firstly, the microthrombus model of rat (Sprague-Dawley rat weighing 500-700g) is constructed after anesthesia by intravenous administration of dextran. About 30 minutes later, venous blood is drawn for microscopic observation, and the concentration of microthrombus is evaluated and counted.

Implying that in this rat model, induced microthrombi in the 10-100 µm range are in circulation for 30 mins.

The concentration of microthrombus in the sample is about 50/ml. Secondly,TMMBs are injected into the blood vessels through the femoral vein allowing them to freely bind to the travelling microthrombi in the blood flow. Thirdly, the magnetic catheter is inserted into the inferior vena cava. Fourthly, the magnetic catheter is kept staying in the vessel for about 3 minutes. In this period, the MT-TMMBs combinations can be captured to the surface of the magnetic catheter. Finally, the magnetic catheter is extracted, and the captured microthrombi are drawn out and removed from the body of the rat.

As shown in Figure 5D, the magnetic catheter has captured significant amount of dark substance on its surface. The colors, from dark to light, indicated that the amount of the captured substance reduces gradually along the catheter. Further analysis on the captured substance is performed with fluorescence observations of rhodamine-stained platelet marker RGDSandcoumarin 6-labeled PLGA using reflection transmission microscopy. Additionally, we used energy dispersive spectroscopy to identify their surface elements. As shown in Figure 5F and Figure S5, the captured substances are platelet-rich microthrombus and TMMBs. Most of the microthrombi are found close to the poles of the magnetic units, where the strength of magnetic field is large.

After the treatment, we take the venous blood sample from the rat and the concentration of microthrombus is counted on the fluorescence microscopy. The results show that the concentration of microthrombus is 60.87% lower than that of the samples taken before the treatment. As shown in Figure 5G, the concentration drops from 46/ml±19.6/ml to 18/ml ±11.7/ml (P<0.05).

 

[SNT Gatchaman]