(T1130-01-01) Active Targeting to the Hepatocytes: How Important is Tailoring the Liposomes and Physicochemical Properties and Surface Modification in Targeting the Hepatocytes?

Purpose: The ability to selectively target drugs to their site of action is an increasingly important aspect in medicine. Using drug delivery systems and introducing active targeting strategies could maximize the accumulation of a drug to the desired site, while lowering its toxicity. Nanosized- drug carriers have been suggested to achieve this goal, and liposomes are one of the most studied nanocarriers. However, exploiting liposomes and other nanocarriers for delivery to the hepatocytes remains challenging, despite liver disease representing some of the most common diseases globally.

Methods: Different approaches have been taken to identify the best strategy for targeting the hepatocytes and to study the impact of composition on the physicochemical properties of liposomes. Three neutral liposomal formulations (100-200 nm) made from phosphatidylcholine derivatives (DSPC, soybean (SPC) and hydrogenated soybean (HSPC)) and cholesterol, using thin film hydration method. The liposomes were evaluated in terms of size, zeta potential and membrane fluidity. The liposomes lyophilization was performed for SPC liposomes using 150 mM sucrose using pre-and post-insertion method.

Results: Preliminary studies using SPC liposomes, suggested that a phospholipid: cholesterol ratio of 70:30 produced the best formulations; this ratio was then selected for all liposome formulations. Overall, liposomes size was below 200 nm with a narrow distribution index (PDI < 0.3 a.u.). The zeta potential was within the range for neutral liposomes (-10 to 10 mV). Surface modification was performed using 2 or 5 mol% PEG (neutral, cationic, anionic). In general, PEGylation led to an increase in size, which was statistically significant for SPC liposomes (p-value < 0.01). As expected, the surface charge was reduced compared to non- PEGylated vesicles. PEGylation efficiency varied between (22-85%), with DSPC liposomes achieving the highest efficiencies (85% when 2 mol% PEG was used). Initial PEG loading also affected PEGylation efficiency, with higher loadings achieved when 2 mol% PEG was used. Membrane permeability studies performed using Calcein as a hydrophilic probe, showed temperature- and PEGylation-dependent patterns for SPC and HSPC liposomes (p- value < 0.05). In term of lyophilization, in both cases, liposome size was maintained, but the post- insertion resulted in better homogeneity.

Conclusion: This study confirmed that composition must adjusted carefully when formulating liposomes, as this can affect the ease with which the surface can be modified and the release rate of an encapsulated compound.

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Acknowledgements: Many thanks for my government (Saudi Arabia) represented by Higher Education Ministry and My academic institute (Princess Nourah bint Abdulrahman University) for funding my work. Thank you for my supervisor, Dr. Marie-Christine Jones from the University of Birmingham, for her supervision and continuous efforts.


Figure 1: Impact of inserting different PEG-2000 types using 2 and 5mol% on SPC Liposomes average size (A), PDI (B), and Zeta potential (C). Data represents the mean± SD of three individual experiments.


Figure 2: Membrane permeability and %Release for SPC Liposomes (A), DSPC Liposomes (B), and HSPC Liposomes (C) with different modifications. Data represents the mean± SD of three individual experiments.


Table 1: PEG absorbance values for liposomes containing different types of PEG and their %EE.