Different types of nanoparticles were synthetized and studied either as a drug itself or as a drug delivery system aiming to combine benefits of individual particles. In this work we focused on the encapsulation of fluorescently labelled ruthenium dendrimers (FITC-CRD13) possessing anticancer properties [1] into the lipid vesicles composed of DMPC/DMPG/Cholesterol. FITC-CRD13 dendrimers (10 µM) were encapsulated into the liposomes by passive loading during the hydration step of lipid film (t = 1.5 h, T = 40°C) in sodium-phosphate buffer (10 mM, pH 7.4) upon the continuous shaking. Subsequently, the prepared vesicles were extruded through 400nm polycarbonate membrane and characterized by 1) absorption and fluorescence spectra of nanoparticles using size exclusion chromatography (SEC-HPLC) on a 30 nm size pore column; and 2) size measurements using dynamic light scattering (DLS). Absorbance at 220 nm and fluorescence at 495/520 nm was used for detection of liposomes and FITC-CRD13 dendrimers, respectively. Firstly, liposomes were eluted at 3.35 min. Fluorescence intensity measured along the elution profile centred at this time point was monitored for dendrimers being locked in liposomes. The coelution, thus encapsulation was less extensive because the subsequent peaks in dendrimer elution profile were observed, indicating the presence of non-entrapped material sized around 70 nm at the later retention times. Hydrodynamic diameter of purified dendrimer-liposomal sample that coeluted at 3.35 min was 210±10 nm with polydispersity index 0.1 reflecting an uniform sample with respect to the particle size. The obtained results can serve for optimization of the encapsulation protocol and as a base for further studies of the dendrimer-liposomal drug delivery platform in the cancer treatment.
This work has been financially supported by Science Grant Agency VEGA, project No. 1/0756/20; by Agency for Promotion Research and Development, project No. SK-PL-18-0080 and SK-BY-RD-19-0019; by KEGA, project No. 041UK-4/2020 and by NAWA International Academic Partnership Programme EUROPARTNER.
[1] Michlewska, S. et al., 2017. Ruthenium metallodendrimers with anticancer potential in an acute promyelocytic leukemia cell line (HL60), European Polymer Journal. Elsevier Ltd, 87, pp. 39–47. doi: 10.1016/j.eurpolymj.2016.12.011.
Size and encapsulation volume
Nice piece of work within a basic research in the field of nanomedicine ...both, liposomes and dendrimers are attractive systems for localized and controlled delivery of potentially toxic agents that cannot be administered systemically. However, one of the major drawbacks of liposomal formulations is their rapid clearance from the bloodstream due to interaction of liposomes with plasma proteins (opsonins) and subsequent consumption by the reticuloendothelial system, which shortens the blood circulation time. This time is inversely related to the size of the liposomes, however, small liposomes have lower space for cargo. Are there any recommendation regarding the „trade-off“ between the size of liposomes and encapsulation load?
Re: Size and encapsulation volume
Thank you for your question. As you have pointed out, the process of opsonization can be overcome by the modification of the surface of liposomes, for instance with PEG (polyethylene glycol), which can prolong the circulation time [1]. The size of liposomes is crucial to the biomedical applications (nanoscale is necessary). In the available literature the size of nanoparticles is recommended to the range between 10 nm - 500 nm [2]. The drug encapsulation efficiency is influenced by the size of the vesicle. We used the passive method to encapsulate dendrimers into the vesicles. It means that the drug, in our case dendrimers, were encapsulated in the preparation process of the vesicles. The low encapsulation efficiency (typical for passive method) can be improved using the active method, which covers the encapsulation step after the preparation of liposomes.
[1] Sercombe, L. et al., Advances and challenges of liposome assisted drug delivery, Frontiers in Pharmacology, 2015, 6, pp. 1–13.
[2] Yingchoncharoen, P., Kalinowski, D. S. and Richardson, D. R., Lipid-based drug delivery systems in cancer therapy: What is available and what is yet to come, Pharmacological Reviews, 2016, 68, pp. 701–787.
Re: Re: Size and encapsulation volume
Thank you for the comprehensive answer, and I wish you all the success in your future professional life.
iwa