Bioinspired cell-derived nanovesicles protect the heart from ischemia reperfusion injury

Introduction

Exosomes have been proven to alleviate myocardial ischemia reperfusion (I/R) injury in preclinical studies. However, the laborious and low-yield production process of naturally secreted exosomes has been impeding their translation into clinical trials.

Purpose

We aim to develop a simple and cost-effective protocol to produce exosome mimetics, bioinspired Cell-Derived Nanovesicles (CDNs), and examine their intrinsic bioactivity in a mouse model of I/R injury.

Methods

CDNs were produced from human U937 monocytes using cell shearing approach and characterized by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). Lipid composition of cells and CDNs was analysed by lipidomics. I/R injury was induced by transient occlusion of left coronary artery. Data was analysed with Mann-Whitney U test. P<0.05 was considered statically significant.

Results

We obtained 538 mg (protein content) of CDNs, or 3x109 CDNs, via cell shearing approach from 2×107 cells, approximately 15 folds of exosomes via natural secretion from the same number of cells. CDNs were 125±8 nm in diameter with negative surface charge (zeta potential −7.0±0.8) and presented as double-membranous vesicles under TEM. In vitro, CDNs showed strong antioxidant activity and could be taken up by bone marrow-derived macrophages. Following intravenous administration, as demonstrated by the IVIS Spectrum imaging system, CDNs accumulated specifically in the infarct area of the heart within 3 hours. Compared with saline treatment, CDNs reduced myocardial infarct size by 31.6% (p<0.01) after 24 hours of I/R injury. Intriguingly, CDNs generated from human mesenchymal stem cells showed similar therapeutic efficacy. Mechanistically, CDNs inhibited infiltration of inflammatory cells (macrophages) and promoted upregulation of the anti-inflammatory cytokine interleukin 10 (IL10) in the I/R injured hearts. In the blood stream, CDNs increased IL10 protein level and exerted antioxidant activity. Furthermore, CDNs reduced I/R injury-induced cell apoptosis in the myocardium.

Conclusion

We have established a cost-effective approach to produce exosome mimetics, bioinspired CDNs, which protect the heart from I/R injury via inhibition of inflammation, oxidative stress and cardiac cell apoptosis. CDNs have intrinsic cardioprotective capability in heart injury, comparable to exosomes.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): National University Health System.

Enhancing image contrast of carbon nanotubes on cellular background using helium ion microscope by varying helium ion fluence

Carbon nanotubes (CNTs) have become an important nano entity for biomedical applications. Conventional methods of their imaging, often cannot be applied in biological samples due to an inadequate spatial resolution or poor contrast between the CNTs and the biological sample. Here we report a unique and effective detection method, which uses differences in conductivities of carbon nanotubes and HeLa cells. The technique involves the use of a helium ion microscope to image the sample with the surface charging artefacts created by the He⁺ and neutralised by electron flood gun. This enables us to obtain a few nanometre resolution images of CNTs in HeLa Cells with high contrast, which was achieved by tailoring the He⁺ fluence. Charging artefacts can be efficiently removed for conductive CNTs by a low amount of electrons, the fluence of which is not adequate to discharge the cell surface, resulting in high image contrast. Thus, this technique enables rapid detection of any conducting nano structures on insulating cellular background even in large fields of view and fine spatial resolution. The technique demonstrated has wider applications for researchers seeking enhanced contrast and high-resolution imaging of any conducting entity in a biological matrix - a commonly encountered issue of importance in drug delivery, tissue engineering and toxicological studies.

Synthesis, biological and modeling studies of 1,3-di-n-propyl-2,4-dioxo-6-methyl-8-(substituted) 1,2,3,4-tetrahydro [1,2,4]-triazolo [3,4-f]-purines as adenosine receptor antagonists

A new series of potential adenosine receptor antagonists with a [1,2,4]-triazolo-[3,4-f]-purine structure bearing at the 1 and 3 position n-propyl groups have been synthesized, and their affinities at the four human adenosine receptor subtypes (A(1), A(2A), A(2B) and A(3)) have been evaluated. In this case the presence of n-propyl groups seems to induce potency at the A(2A) and A(3) adenosine receptor subtypes as opposed to our previously reported series bearing methyl substituents at the 1 and 3 positions. In particular the non-acylated derivative 17 showed affinity at these two receptor subtypes in the micromolar range. Indeed, preliminary molecular modeling investigations according to the experimental binding data indicate a modest steric and electrostatic antagonist-receptor complementarity.