Hello everyone,
I am trying to encapsulate an essential oil in the liposomes using the heating method and encountering some issues. I am following the protocol described below, but my solution always ends up aggregating, while heating. In use is soy lecithin, S75, from Lipoid. I would greatly appreciate any help and advice.
M.R. Mozafari's Protocol:
1. Hydrate the ingredients in an aqueous medium for 1–2 hours under nitrogen at room temperature (RT).
2. Mix the dispersion with the material to be encapsulated after adding glycerol at a temperature of 120°C. In the absence of cholesterol, a lower temperature can be used.
3. Mix the sample (800–1,000 rpm) at a temperature above the Tc* of the lipids until all the lipids and other excipients are dissolved/dispersed.
4. Leave the product above Tc* under nitrogen for 1 hour to allow the sample to anneal and stabilize.
My Protocol:
1. Add 72.75 mL PBS to the preparation vessel. Hydrate the phospholipids by adding them to the PBS solution at room temperature. Stir gently at 250 RPM, 1-2 hours, until a dispersion is obtained.
2. Transfer the essential oil to the hydrated phospholipids in the corresponding preparation vessel and homogenize the solution at 1000 RPM for 5 minutes.
3. Add 2.25 mL of glycerol to each batch and homogenize at 1000 RPM, 55°C for 30 minutes, or until the lipids are completely dissolved.
4. Finally, leave the suspension at 60°C for 1 hour.
The concentrations used are 4 mg/mL phospholipid and 4 mg/mL essential oil. The goal is to achieve at least 10 mg/mL for both the essential oil and the phospholipid.
Thank you in advance for your assistance!
Hello,
1. A high concentration of essential oil may be disrupting liposome self-assembly due to the hydrophilic-lipophilic balance. Using the same concentration of essential oil and phospholipid (the carrier) may reduce their efficacy. Start with a much lower concentration and gradually increase it to find the optimal balance.
2. Consider employing post-formation processing methods such as microfluidics, extrusion, or sonication to improve liposome formation. These techniques can produce smaller, more uniform liposomes and mitigate aggregation.
3. It may be beneficial to assess the zeta potential to measure the surface charge and adjust it to values greater or less than ±30 mV to avoid aggregation.
I hope this helps!
Here are a few suggestions to troubleshoot and potentially resolve the issue:
By making these adjustments, you should be able to reduce or eliminate the aggregation issue. If the problem persists, it might be helpful to consult with colleagues or experts who have experience with liposome preparation and encapsulation techniques.
Hi everyone;
After reading excellent answers given by Cecilia Torqueti de Barros and Phil Käding there is nothing much left for me to say in response to the question raised by Maximilian Proksch .
However, I would like to share some of our recent publications on the details of 'Heating method' and 'Mozafari method' and their differences with you. As you know, the main advantage of these 2 methods is absence of toxic solvents and high-shear force procedures. Different parameters must by fine tuned to achieve monomodal particle distribution, with acceptable PDI, without the need to use harsh procedures.
Please note that depending on the ingredients of the vesicles, and characteristics of the active material we want to encapsulate, we may need to use another polyol instead of glycerol. The importance of electrostatic repulsion was mentioned correctly by Cecilia. Phil in a very expert way mentioned the importance of phase transition temperature of the ingredients. These parameters are explained in the papers listed below (2 of them are attached, let me know if you require other literature):
1. Insight into heating method and Mozafari method as green processing techniques for the synthesis of micro-and nano-drug carriers.
Z Jalilian, MR Mozafari, S Aminnezhad, E Taghavi
Green Processing and Synthesis 13 (1), 20230136 (2024).
2. A Review of Patents on "Mozafari Method" as a Green Technology for Manufacturing Bioactive Carriers.
G Maleki, Z Bahrami, EJ Woltering, S Khorasani, MR Mozafari
Biointerface Research in Applied Chemistry 13 (1), 34 (2023).
3. Probing nanoliposomes using single particle analytical techniques: Effect of excipients, solvents, phase transition and zeta potential,
M Danaei, M Kalantari, M Raji, HS Fekri, R Saber, GP Asnani, ...
Heliyon 4 (12) (2018).
4. Impact of particle size and polydispersity index on the clinical applications of lipidic nanocarrier systems.
M Danaei, M Dehghankhold, S Ataei, F Hasanzadeh Davarani, ...
Pharmaceutics 10 (2), 57 (2018).
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