The loading of exosomes with drugs can be achieved with various methods. The choice of method is often dependent on the physical properties of the drug of interest. For instance, a drug with an overall negative charge would be very difficult to load into exosomes using a passive method because exosomes carry an overall negative charge. Note that you should test variable parameters for new loading experiments such that you determine the best parameters to use for large-scale loading.
The Electroporation method can be used to load drug into exosomes, but in order to do so, you must use an electroporation buffer; there are several buffers on the market, and formulations are similar, but be sure to be consistent with your choice. If it works for you, great – keep on using it! Note that if the required drug volume should be as low as possible such that the buffer is not compromised; if drug volume is excessive, consider using a higher concentration of drug.
Also be sure that your drug of interest is not compromised during the electroporation reaction; some drugs undergo conformational changes during the reaction. An alternative is to add your drug after the electroporation reaction since it will take some time for the micropores on the surfaces of the exosomes to close up.
Incubation is a passive method of loading drug into exosomes. Simply, drug and exosomes are suspended together and incubated until loading is maximized. This works well for neutral or positively charged drugs. We have successfully loaded exosomes suspended in DPBS with drug at various temperatures (37 oC and 4 oC, for example). Also, loading time is a variable that needs to be tested; we have used loading times as low as 5 minutes, and loading times of 18 hours.
Reagents such as Lipofectamine (ThermoFisher) and Exo-Fect (SBI) are practical options to use in cases where exosome loading is challenging. Size and/or charge on drugs often times makes exosome loading difficult, so using commercial reagents should be kept in mind in such cases.
Other Loading Methods
Other loading methods are available and can be viable options. Methods such as sonication and extrusion are methods used by other laboratories with success.