ABSTRACT
Although the biological and clinical relevance of extracellular vesicles (EVs) is increasingly recognized, their isolation and detection have proven to be extremely difficult. On the one hand, due to the biological complexity of body fluids, physical separation of vesicles from similar-size particles and cells is complicated. Consequently, it is probable that in many studies not only vesicles were detected.1 On the other hand, since the diameter of vesicles is typically ranging from 30 nm to 1 µm, vesicles are below the detection range of many currently used techniques.2 As a result, after isolation the recovery and contamination cannot be reliably quantified, and isolation protocols have not been standardized (Chapter 5). The interrelated difficulties of the detection and isolation of EVs clearly expose one of the main issues to be solved by the research field. To fully understand
and appreciate the content of this book, it is essential to point out the capabilities and limitations of methods to isolate and detect EVs. This chapter provides an overview of novel and conventional methods to detect EVs. For each technique, we will discuss its capability to assess relevant properties of vesicles, whether the information is obtained from individual or multiple vesicles and whether the technique can be applied directly in suspension. In addition, we will contemplate the applicability of each method in terms of measurement time, assuming the detection of 10,000 vesicles, a number that is common in flow cytometry. All findings are summarized in Table 4.1. The methods listed in Table 4.1 can often provide more detailed information than mentioned here if the instrument is operated by a specialist with foreknowledge of the sample.
